The androgen receptor (AR) is one of the main components in the development and progression of prostate cancer (PCa), and treatment strategies are mostly directed toward manipulation of the AR pathway. In the metastatic setting, androgen deprivation therapy (ADT) is the foundation of treatment in patients with hormone-sensitive prostate cancer (HSPC). However, treatment response is short-lived, and the majority of patients ultimately progress to castration-resistant prostate cancer (CRPC). Surmountable data from clinical trials have shown that the maintenance of AR signaling in the castration environment is accountable for disease progression. Study results indicate multiple factors and survival pathways involved in PCa. Based on these findings, the alternative molecular pathways involved in PCa progression can be manipulated to improve current regimens and develop novel treatment modalities in the management of CRPC. In this review, the interaction between AR signaling and other molecular pathways involved in tumor pathogenesis and its clinical implications in metastasis and advanced disease will be discussed, along with a thorough overview of current and ongoing novel treatments for AR signaling inhibition. Prostate cancer (PCa) is the most frequently diagnosed neoplasm in developed countries and is accountable for the second-highest rate of cancer-related deaths . SignifiThe underlying molecular mechanisms that lead to progression to CRPC are associated with the conservation of AR signaling in the castration-level androgen setting . ClinicaThe need to understand the intricate relationship between AR signaling and other molecular cascades involved with the pathogenesis of PCa and its therapeutic implications in advanced disease is of utmost importance, along with the familiarity of current and novel therapeutic approaches utilizing the AR signaling pathway for the treatment and management for patients with PCa in the advanced setting.Classified as a steroid hormone receptor, the AR is a ligand-activated nuclear transcription factor whose role is the regulation of target gene expression. The AR consists of a DNA-binding domain (DBD), along with a hinge region and ligand-binding domain (LBD) and an N-terminal domain (NTD) that consists of two repeated polymorphic trinucleotide segments. The repeat segments are constituted of random polyglutamine and polyglycine repeats, which are involved in the regulation of AR transcriptional activity ,19. AR eThe prostate tumor microenvironment (TME) harbors a various number of inflammatory cells and stromal components. Of these cellular constituents, cancer-associated fibroblasts (CAFs) are recruited and activated by factors secreted from the primary cancer, enabling molecular crosstalk with tumor cells. This interaction activates CAFs, which initiate cytokine release and extracellular matrix (ECM) deposition. This molecular cascade results in the reorganization of the structure and composition of the connective tissue along with the release of growth factors that influence the modification of the ECM. This alteration increases tumor stiffness and induces the proliferation and growth, along with drug-resistance of the newly transformed epithelial cells . The CAFIn the TME, tumor-associated macrophages (TAMs) comprise the majority of the population within the cellular milieu and are usually activated by a variety of chemokines, from chemokine C-C motif ligand 2 (CCL2) to CCL5 . DependeThe molecular crosstalk and relationship between the prostate TME and AR signaling are of an intricate nature, in which the AR and TME have both tumorigenic and anti-tumorigenic roles . The AR As the benign prostate cells transform into cancer cells, the structural and genomic transition of the stromal cells results in a progressive decrease in AR expression. Starting from low-grade PCa, there is a linear decrease in the mean AR stromal expression, which is almost entirely absent in high-grade disease . It has According to the study results of Abeshouse et al., AR gene mutations and amplifications are observed in 1% of patients with PCa , and appAs a therapeutic form of castration, ADT plays an essential role in the management of metastatic PCa and patients in the advanced setting. This chemical regimen inhibits the production of androgens and consists of anti-androgens that competitively bind to the C-terminal of the AR, resulting in activation blockage of the AR. The ADT regimen usually consists of gonadotropin-releasing hormone (GnRH) agonists that inhibit the production of androgens, such as leuprolide acetate, triptorelin, goserelin acetate, and histrelin ,67,68. ARecent studies and clinical trials have focused on other pathways of AR alterations to better comprehend the vast clinical spectrum of therapeutic resistance to ADT in the clinical setting of PCa. Several AR variants (AR-Vs) that result in natural resistance have been observed in CRPC cell lines . Most AREven in the setting of CRPC, AR signaling continues as a significant factor of tumor growth and disease development . The prop = 0.001). The most common adverse events (AE) were fatigue and musculoskeletal events, which occurred in 31% of the enzalutamide arm in comparison to 21% in the placebo group , p < 0.001). The therapeutic advantages of enzalutamide were observed in all specified subgroups, which consisted of patients with low-volume disease and patients who had received prior chemotherapy with docetaxel. Incidence of grade 3 or higher AE was comparable between the study groups at 24% for enzalutamide-treated patients and 25% for the placebo group. The study concluded that enzalutamide treatment significantly reduced metastatic progression or death, and due to its safety profile, enzalutamide should be considered a viable therapeutic option for patients with mHSPC p = 0.005) and rPFS at 24 months was 68.2% in the study drug cohort while 47.5% was noted in the placebo group. Grade 3 or 4 adverse events were observed with comparable frequency across the two study populations at 42.2% in the apalutamide group and 40.8% in the control group [The therapeutic benefit of apalutamide was explored in the phase III, double-blind, TITAN  NCT02489318) clinical trial [18 clinicThe expression of AR is crucial in the development and progression of PCa, and for this reason, ADT is considered the mainstream treatment of PCa. When stimulated, AR translocation to the nucleus is initiated, and regulation of the genetic code needed for cell growth and proliferation occurs . The purProteolysis-targeting chimeras (PROTACs) are molecular structures that consist of a trimeric complex between a target protein and an E3 ubiquitin ligase, which enables ubiquitination of the target followed by consequent AR degradation ,112. RecIn a phase I clinical trial of ARV-110 (NCT03888612), an orally bioavailable PROTAC, 18 patients with at least two prior therapies regarding mCRPC were administered 140 mg of ARV-110 daily. The study reported that two patients achieved a reduction in PSA of ≥50%. Two patients developed grade 3/4 elevated hepatic enzyme levels, but the overall safety profile of the drug was tolerable . AlthougWith the continuous surge in the incidence of PCa, constant improvement in diagnostic modalities and therapeutic options in the clinical setting are mandatory. The significance of AR signaling in the disease continuum of advanced PCa and mCRPC certifies that the AR receptor will remain as the primary therapeutic target. Despite robust clinical research and developments in the pharmaceutical industry for novel anti-androgens, unmet clinical needs remain, and the various mechanisms of resistance that lead to CRPC suggest the requirement of a fundamentally distinct therapeutic approach with novel drug targets. Numerous mutations of the AR have been described as the underlying mechanism to treatment failure, which opens the opportunity for advances and improvements in the diagnosis of PCa at the molecular level. The clinical nature of PCa mandates the importance of identifying these mutations for a tailored-administration of androgen inhibitors most suitable to each patient. Due to its key role in the transcription process, the AR-NTD has become a target for potential novel inhibitors. Although it is a significant challenge, targeting AR degradation or signal blockage provides the potential for developing SARDs and novel inhibitors, such as PROTACs, to overcome drug resistance in patients with PCa in the advanced and metastatic setting. Despite promising results for both modalities mentioned above, further studies and clinical trials would be needed for these novel approaches to be fully utilized in the everyday clinical setting. The development of novel pharmaceuticals based on the accumulated information regarding AR will ultimately reshape future treatment paradigms and clinical decisions in the ongoing treatment advancement for metastatic and advanced PCa.Due to the advances of modern medicine, improvements in traditional therapies and novel treatments have evolved for the treatment of PCa and the therapeutic armory is continuously increasing. AR signaling is a crucial factor involved in the growth and progression of PCa. Therefore, in accordance with this disease spectrum, anti-AR molecules are in development to target the whole disease spectrum of PCa, from high-risk tumors to CRPC in the metastatic setting. However, there is a need for novel therapeutic approaches to improve the overall outcomes in patients with PCa. Many therapeutic agents with different AR-inhibiting mechanisms have shown efficacy in various clinical trials. Moreover, novel AR inhibitors, such as PROTACs and SARDs, have shown promising preclinical efficacy and safety profiles, therefore providing another option for overcoming resistance to current androgen-targeted therapeutics. Further prospective studies and accumulation of data from ongoing clinical trials will provide elucidation of the resistance mechanism of prostate tumors and the underlying molecular pathways for better treatment response.


Virtual reality (VR) and augmented reality (AR) have been combined with physical rehabilitation and psychological treatments to improve patients' emotional reactions, body image, and physical function. Nonetheless, no detailed investigation assessed the relationship between VR or AR manual therapies (MTs), which are touch-based approaches that involve the manipulation of tissues for relieving pain and improving balance, postural stability and well-being in several pathological conditions. The present review attempts to explore whether and how VR and AR might be integrated with MTs to improve patient care, with particular attention to balance and to fields like chronic pain that need an approach that engages both mind and body. MTs rely essentially on touch to induce tactile, proprioceptive, and interoceptive stimulations, whereas VR and AR rely mainly on visual, auditory, and proprioceptive stimulations. MTs might increase patients' overall immersion in the virtual experience by inducing parasympathetic tone and relaxing the mind, thus enhancing VR and AR effects. VR and AR could help manual therapists overcome patients' negative beliefs about pain, address pain-related emotional issues, and educate them about functional posture and movements. VR and AR could also engage and change the sensorimotor neural maps that the brain uses to cope with environmental stressors. Hence, combining MTs with VR and AR could define a whole mind-body intervention that uses psychological, interoceptive, and exteroceptive stimulations for rebalancing sensorimotor integration, distorted perceptions, including visual, and body images. Regarding the technology needed to integrate VR and AR with MTs, head-mounted displays could be the most suitable devices due to being low-cost, also allowing patients to follow VR therapy at home. There is enough evidence to argue that integrating MTs with VR and AR could help manual therapists offer patients better and comprehensive treatments. However, therapists need valid tools to identify which patients would benefit from VR and AR to avoid potential adverse effects, and both therapists and patients have to be involved in the development of VR and AR applications to define truly patient-centered therapies. Furthermore, future studies should assess whether the integration between MTs and VR or AR is practically feasible, safe, and clinically useful. Virtual reality (VR) and augmented reality (AR) have recently drawn professionals and patients' attention in several fields, including psychology, physical, and neurological rehabilitation, and surgery. In particular, the development of low-cost head-mounted displays (HMDs), which can be associated with smartphones, gaming consoles, personal computers, or workstations, brought VR and AR outside research laboratories toward a vast audience of users , 2. VR aVR aims to create an environment that the users feel as realistic and coherent: they should experience “presence”—the illusion of “being there” in the simulated environment and the feeling that what is happening is plausible. Indeed, the simulated events have to follow precise physical laws, satisfy psychosocial expectations, and synchronize with the user's actions . AR aimsThe efficacy of both VR and AR lies, thus, in the creation of a coherent simulation: the users must experience the same physical laws during the whole simulation and perceive synchronicity between their (re)actions and the virtual stimuli. Once accustomed to the simulation, the users must see congruence between what is happening and their expectations . If the In the last decade, VR and AR applications in the medical and psychological fields have increased: they are used for educational purposes, surgical training and procedures, neuromotor rehabilitation, and anxiety treatments , 4. Howeper se. Hence, the interaction of MTs with VR and AR remains somehow unknown.Manual therapies (MTs) are touch-based approaches, such as various types of massage or osteopathic manipulative treatment (OMT), that involve the manipulation of tissues . AlthougTherefore, after briefly reviewing the effects of MTs, VR, and AR in healthcare, the present paper aims to propose how these approaches, in particular, MTs and VR, could be combined for improving patient care. Indeed, integrating the tactile, proprioceptive, and interoceptive sensations elicited by MTs with the  simulated VR experience could harness the benefits and overcome the limits of both. Their integration's positive effects could occur especially in fields like pain, whose treatment needs a comprehensive approach that involves physical, biochemical, and psychosocial factors –14.In order to obtain a comprehensive analysis of the literature, the current review used the following search strategies in Pubmed:for VR and AR, the basic query was [“systematic review” (Publication Type)] AND ;for manual therapies, the basic query was [“systematic review” (Publication Type)] AND [bodywork OR  OR (“osteopathic manipulative treatment”) OR (“osteopathic treatment”) OR (“high velocity low amplitude”) OR (“muscle energy”) OR (counterstrain) OR  OR  OR  OR (“lymphatic pump”) OR (“rib raising”) OR  OR  OR (“fourth ventricle”) OR (CV4) OR (“trigger point”)].For both queries, we repeated the search by adding condition-specific keywords, such as pain, chronic pain, balance, dementia, depression, quality of life, phobia, and surgery. We then selected the papers involving adult people (18+ years old), from inception to February 2021.MTs, VR, and AR are used to manage several pathological conditions and improve patients' health-related quality of life (HRQoL) and disability. Over the last few years, several systematic reviews investigated their efficacy and safety. Despite the need for more rigorous research—more significant samples, better description of randomization, allocation concealment, interventions, and control group, follow-up assessment, better statistical analyses, standardized methodology, uniform choice of the outcomes to easily pool the results in meta-analyses—for MTs –17, VR aMTs, VR, and AR are generally safe—just some minor transient adverse effects were reported, particularly muscle stiffness and symptoms worsening for MTs , 24, andEvidence shows that MTs could help improve fatigue, sleep, and well-being –35. MTs MTs could be useful in caring for individuals with acute and chronic pain. In particular, MTs  showed clinical effects in acute and chronic LBP, neck pain, lateral epicondylitis, headaches, pain due to surgical and non-surgical adhesion, and pain-related disability , 40–45. Nevertheless, there are mixed results on the effectiveness of MTs in reducing pain: for instance, in some cases MTs such as spinal therapies seem to be ineffective in treating mild to moderate chronic LBP , whereasSome weak evidence shows that MTs, for instance, OMT, might help prevent falls and ameliorate objective measures of mobility and balance  in the case of dizziness  and cervLastly, some evidence shows MTs might help manage essential hypertension as an adjunctive therapy to drugs , 16, an As an educational tool, VR and AR enable students to better understand anatomical structures and their spatial relationships through interactive 3D images or models , 20, 22.Specific surgical-oriented VR/AR systems [such as the Da Vinci remote surgical system ] improvein vivo exposure therapy, possibly due to the difficulties in recreating credible social interactions ; and cognitive therapy—using a virtual coach voiced by a real therapist—to augment the treatment of different kinds of phobias and anxiety, cravings for various substances , post-traumatic stress disorder (PTSD), depressive symptoms, and distorted body image in case of anorexia nervosa. The effects are often transferred successfully in everyday life and maintained for months or years, maybe because AR and (mostly) VR allow the simulation of an ecological environment where every exposition cue can be entirely controlled , 65–68. ractions  or the uractions , 81. Morractions –72—the gractions .Beyond the field of psychology, VR improves static and dynamic balance, mobility, gait, stride length, sitting and standing time, fear of movements and risk of falls, aerobic and motor function, muscle tension and strength, and activities of daily life in various populations, healthy or with some disorder  , 73, 76.It is worth noting that, in both fields of psychology and rehabilitation, VR and AR are used mostly as add-on therapies combined with already established treatments. Indeed, VR and AR seem to enhance the conventional therapies' effects through the intensification of experience induced by gamification and realistic simulations , 30, 66.Lastly, by recreating certain events  in a simulated environment, VR and AR could also help understand the causes of psychological and neuromotor disorders and the stimuli that trigger them, allowing practitioners to deliver the therapy that best suits their patients , 75, 78.Despite the burgeoning research on VR and AR role in the rehabilitation field, MTs and their combination with these technologies seem to have not received attention. Research has focused primarily on patients experiencing VR and AR before or after physical therapy sessions, with therapists acting as “mere” support  or whenever patients had difficulties in executing a task –85. Due Considering that MTs elicit tactile, proprioceptive, and interoceptive sensations, whereas VR and AR send primarily visual and auditory stimuli, these interventions could be complementary. It is true that new technologies are emerging to bring tactile and internal sensations in simulated environments—for example, force feedback systems like Geomagic Touch to simulate tactile sensations and proprioception , skin-inThe combination of MTs with VR and AR could define a whole-body intervention that includes both interoceptive and exteroceptive signals, with the potential of improving sensorimotor integration and rebalancing distorted perceptions and body images in patients suffering from eating disorders, autism spectrum disorder (ASD), or other disperceptive conditions (maybe even body identity integrity disorder) , 90, 91.Therefore, after discussing the usefulness of low-cost head-mounted displays (HMDs), the devices more suitable to introduce VR in the setting of MTs, this section will focus on the potential and reciprocal contributions between VR (in particular), AR, and MTs to improve healthcare.As a side note, VR and AR could also improve students' training and manual skills. For instance, AR-derived 3D models of the manipulated/mobilized body tissues could enhance the manipulations' efficacy and avoid potential adverse effects. However, the technology required for achieving the high precision in tactile and force reproduction needed to perform efficient training is still lacking at the moment .A limitation of several VR studies is that the authors used systems such as Nintendo® Wii Fit, PlayStation® 2 EyeToy camera, and Microsoft® Xbox Kinect that, although more engaging than conventional therapy, lack the immersion that should characterize VR—they lack presence , 2. FurtThe commercialization of low-cost HMDs, which can be associated with personal computers, tablets, and smartphones, partially overcome the lack of immersion . Indeed,Despite the limitations regarding immersion, HMDs could represent the key for combining VR and AR with MTs: on the one hand, the tactile stimuli of MTs might somehow replace the proprioceptive and interoceptive stimuli needed for immersion; on the other hand, while receiving MTs, patients tend to stand still, e.g., lying on the massage table, and so tracking the body's movements could be unnecessary. Therefore, while receiving treatment, the patients could easily immerse themselves in the VR experience, hence benefitting from interventions. In fact, the therapeutic goal becomes paramount to choose the proper equipment to use: for instance, proprioceptive devices or motion-capture would be necessary if the VR experience had to directly act on body perception, whereas the same devices would be not required if the VR simulation served just as a distractor or relaxing stimulus.HMDs could also enhance ecological validity in both the research and the clinical setting. In neuroscience, VR has been deemed paramount to introducing ecological validity in the laboratories while maintaining adequate control of experimental stimuli and confounding variables . Using VThe portability and accessibility of HMDs could increase the studies' ecological validity and generalization because researchers may study VR directly in the clinical setting or at the patients' homes, thus genuinely bringing VR outside the laboratories and into real life. Indeed, VR helps people perform therapeutic exercises at home with good results in stroke and incomplete spinal cord injury –102.Relying on the Internet and the Cloud, HMDs and associated devices  could send data about the performed exercises directly to the therapists, thus allowing them to supervise their patients better and potentially improving adherence to therapy . Even auAll these features can also be used to customize the treatment received by the patients. Indeed, technological evolution allows therapists to model therapeutic exercises or tasks for their patients: therapists could record themselves while doing the exercises, save and customize the motions through VR software and, then, construct specific and easily flexible therapeutic plans. On the other side, patients could view the tasks to be performed as many times as they need, detect maladaptive movements  and check their performance and progress , 98, 103Manual therapists could instruct patients through HMDs as well, showing them how to perform several kinds of self-massage or self-touch that could help maintain the effects of MTs in the long-term. Regarding home-based care, the use of wireless haptic interfaces  could evAlthough cheaper than other technologies, HMDs are not free: their cost could still be unaffordable for people of low socioeconomic status. Therefore, who should bear the cost of HMDs (or similar devices) for these people, should they need them for improving their health through home-based VR sessions ? Indeed,MTs may induce local effects, through the activation of mechanobiological pathways that can change the cells' behavior , and leaIndeed, touch activates several neural pathways that project to cerebral areas involved in sensory, affective, and cognitive functions . WhereasInterestingly, in the last few years, several papers showed that OMT may affect brain activity in both healthy adults , 119 andMTs may elicit a parasympathetic response, which usually correlates with a state of relaxation , 122. MTCurrently, there is robust evidence that inflammation may influence the nervous system and cognitive-affective functions –135. TheThe activation of the interoceptive network and the physiological changes mentioned above, including the possible modifications of heart rate variability (HRV) elicited by the alteration in the autonomic tone , 139, coVR and AR could help MTs in several ways and especially in treating pain and pain-related disability. Appropriate VR designs are recognized to provide analgesic outcomes : they caA specific simulated environment depicting several types of postures, movements, or situations could help therapists and patients understand better when and how pain occurs. This type of simulation could show postures/movements from both first and third-person perspective: in the former case, appropriate kinesthetic and proprioceptive devices could be paramount to elicit the sense of body ownership efficiently; in the latter case, the observation of another person or avatar would trigger the activation of the mirror neuron system, an essential mediator for successful sensorimotor rehabilitation using VR –148.That same simulated environment could also help decrease the pain-related experience in the same way that interventions such as RHI, mental imagery, and mirror therapy do –151. IndThrough VR and AR, the triggering stimuli can be adapted to patients' needs varying their intensity, duration, repetition, and so on. The simulated stimuli could even surpass reality , hence favoring better results with more ease, although this is yet to be tested , 66. IndAll these effects could make patients more aware of their pain-related experience and improve pain management. For example, patients could better comprehend what events trigger their pain, thus learning how to manage and face them, and what events may reduce pain. On the other hand, therapists could better understand their patients' pain-related experiences. On occasion, pain treatment is problematic because patients fail to reproduce the exact conditions that induce their pain. Therefore, therapists lack a clear understanding of their patients' pain-related experience and the best intervention to perform. This situation is particularly significant when pain is not worsened by physical factors but by psychosocial ones, like stress, negative emotions, and beliefs. Despite evidence demonstrating that psychological and neurobiological factors can significantly influence musculoskeletal pain—pain is more about how the brain elaborates the psychophysical stimuli and responds to them, and that pain is, first and foremost, a subjective feeling , 154–156VR and AR could help therapists enhance the effectiveness of pain neuroscience education and other programs aiming to teach the most recent discoveries about the complexity of pain , 160. ThVR and AR applications could help patients overcome the fear of movement through exposition to activities perceived as painful , 163. WhIt is worth noting that sometimes pain could arise from traumatic events  the patients fail to correctly remember—the memory was not adequately encoded and, therefore, the event lacks a precise context. A typical example of this situation is PTSD . The “blVR also has the potential to elicit awe, emotion at the core of experiences such as flow, strong spiritual and mystical feelings, and the “overview effect” . Awe-inspiring environments might create a safe space that makes patients relaxed, peaceful, joyful, prosocially active, and ready to have a transformative experience, i.e., changing their behavior . This seLastly, as already described in the paragraph “3.1 The advantages of HMDs in research and clinical fields,” an advantage that VR and AR could give to MTs is the possibility of continuing and monitoring the treatment at the patient's home, thus improving adherence to therapy . By remoHowever, this use of VR entails careful control and protection of patients' personal data to guarantee their privacy, especially if third parties are involved in the applications used by therapists and patients .The VR's putative modulatory effects on pain and other conditions  may be achieved since VR might reflect how the brain works . If the According to this view, the organism does not need to understand what is happening in the world perfectly, nor it could: due to the limited energy and resources  available, it would be impossible to pay attention to all the environmental variables, i.e., sensory stimuli. Therefore, based on past sensorimotor activations (past beliefs), the brain creates a surrogate model of reality—the internal generative model—and then makes predictions about the upcoming events (posterior beliefs) by weighting that same model with the sensory evidence . These predictions must be accurate enough (not the most correct!) to allow the organism to survive and protect its psychophysical integrity. After every experience , the brain:tests its generative model against the sensory information coming from the world;tries to fit the sensory information in the generative model;if required, updates the generative model  to increase its usefulness and accuracy, but always trying to keep the model's complexity and redundancy at a minimum .Since the resources available are limited, the brain needs to make useful predictions while maintaining a surrogate model of reality as simple as possible. This way, both the information free energy (the number of variables accounted for) and the thermodynamic free energy (the metabolic cost to encode and apply the generative model) are minimized . From aThe Bayesian brain has gained growing attention in the last years. It involves the whole body multisensorial, motor, and interoceptive/affective representation in the brain and its control by a complex neural network—the “body matrix” . Indeed,VR could facilitate the update of the internal generative model since it seems to function similarly to the brain: indeed, researchers aim to construct VR systems able to create sensory stimuli, detect the subjects' movements or actions and, based on a model of the users' body, try to predict the sensory consequences to give users a plausible and coherent experience, as if they were in the real world . If the The more advanced the VR system is—i.e., multimodal devices to recreate every external and internal sensation, and software based on complex machine learning algorithms able to perform the aforementioned processes—the more the simulation is perceived as coherent and embodied. VR users, thus, would feel the virtual body as their own, the brain would generate its internal model based on it, and the sense of agency would become “embodied” in it , 90. AgaWhen patients perceive a virtual simulation as coherent, therapists could use VR to elicit specific prediction errors through finely controlled stimuli to violate the internal generative model and facilitate its update. This way, therapists could favor modifying the dysfunctional representations of the body that may be at the root of pain, eating disorders, and other conditions that involve self-perception, including depression. Indeed, the brain uses the embodied simulation to predict sensations, actions, and even emotions , 90.Therefore, complex VR simulations aim to act as cognitive prostheses to change the neurobiological processes that underlie both the perception and the physiological body responses to events. To this end, therapists need systems (hardware and software) that create a scenario that is felt coherent by the patients' brain, despite the awareness that “it is all an illusion,” and that is able to elicit specific responses  useful to reach the desired outcome  , 90, 177There are several considerations in regards to the integration between MTs and simulated experiences: in particular, they concern the state of research about the relationship between MTs and VR or AR, the characteristics of available VR and AR technologies, the possible negative consequences of their use.Since literature lacks papers about the integration between MTs and VR or AR, trials that combine these interventions are required, starting from the ones that should assess the feasibility of combining the two approaches and evaluate possible adverse effects. The following trials should assess the effects of VR and AR applied before or after MTs sessions; others should investigate the effects of conducting VR sessions while the patient is receiving MT. Researchers should also evaluate whether VR could help patients change their counterproductive or wrong beliefs about pain and movement. Lastly, there is the need to understand whether manual therapists could use already developed VR and AR applications, or if new and original software is required.Therapists need valid and reliable devices able to create immersive environments that induce presence/flow and avoid cybersickness. Since presence and cybersickness share a common ground—they are both increased by immersion, research should define which features of the simulation or the technology used could skew the virtual experience toward presence or cybersickness , 180. InAlthough useful as explained in “3.1 The advantage of HMDs in research and clinical fields,” HMDs might favor cybersickness, in particular, when the body is immobile while the eyes are tracking virtual visual stimuli. This might occur when the patient explores a virtual environment while receiving MT on a massage table , 181. InAccording to some authors, HMDs could hinder the immersion in the virtual simulation due to the feeling of wearing HMDs . HoweverResearchers could also study which biomarkers can discriminate between presence and cybersickness: for instance, some trials evaluated the use of HRV, which functions as a useful indicator of stress, sympathetic and parasympathetic modulation, all factors that can influence the balance between presence and cybersickness . The HRVAnother possible issue with VR and AR is the uncanny valley phenomenon that could arise, for instance, when VR is used to support and supervise patients at home. The therapist avatar or, more likely, the virtual coach could elicit feelings of aversion if it should look quite-but-not-exactly human , 81, thuAnother limitation is that VR simulations are not usually personalized for specific patients, but represent “generic” scenarios  to which every patient has to adapt. This limitation could entail a low engagement with the therapy, especially in the long-run and despite relying on specific features such as gamification for increasing motivation. Indeed, even factors such as age, gender, and personality traits may influence the VR experience and its effectiveness , 187. OnThe addition of MTs to VR could increase the patients' motivation by improving their body awareness. Therapists can use touch to help patients become more aware of their bodily sensations—touch can elicit both interoceptive and proprioceptive feelings , 113 —anLast but not least, a limitation regarding the use of VR and AR  arises from the negative consequences the users could suffer. Patients could have difficulties in “returning to the real world” should the VR sessions be too frequent or take too much time . Motion VR could also induce negative emotions that persist in real life—reliving a fear in a virtual environment could be way more intense than just thinking about it, and indeed immersion/absorption mediates the emotional experience in VR —and causAll these negative effects on emotion, memory, and behaviors may be increased by body-swapping since different bodies—different embodiments—seem to easily favor different emotions and behaviors that may transfer in real life , 195. ThTherefore, beyond designing VR and AR technologies able to minimize all the risks mentioned above, it is paramount to help manual therapists understand which patients would benefit from VR and which patients would risk deteriorating their condition , 191.The present review discussed the effects of MTs, VR, and AR. These interventions have been applied in several medicine and psychology fields and showed results that could significantly impact healthcare if confirmed by more rigorous trials. The commercialization of low-cost HMDs could allow manual therapists to combine VR and AR with MTs, thus creating an intervention that genuinely affects the whole mind-body unity. Indeed, MTs act primarily through touch, eliciting the tactile, proprioceptive, and interoceptive systems, whereas VR and AR send primarily visual-auditory stimuli and aim to affect the user's body's perception. Both MTs and VR may influence the mind, inspiring calm, joy, trust, and awe. Through remote Internet connection, HMDs would also allow manual therapists to supervise their patients at home and patients to continue their treatment outside the clinic, as it is already successfully happening in the rehabilitation field.Regarding the effects the integration between MTs and VR or AR might have on balance and gait, both types of interventions have shown positive effects on these conditions, even in the case of pathologies such as PD , 56, 82.However, several limitations exist that must be overcome to fully harness the potential of the integration between MTs and virtual simulations, starting from assessing the feasibility of combining the two interventions. On the one hand, more research is required to see whether MTs could elicit or hinder the feeling of presence or flow during VR and augment the sense of ownership of the virtual body. On the other hand, more research is required to see whether VR and AR could help MTs manage painful conditions and address negative beliefs about movement and pain. There is also the need to evaluate which available VR and AR applications might be adequate to use in the MTs setting. Besides, to define a truly personalized approach, both therapists and patients have to be involved in elaborating VR and AR software and the process of gamification. Lastly, therapists require reliable tools to recognize which patients would benefit from VR and AR since, as any other treatment, they may induce serious adverse effects.The success of the integration between MTs and VR or AR in everyday clinical practice will also depend on its practical feasibility. Indeed, although low-cost devices such as HDMs are ever more available , the sofAll these questions are therefore left for future research, with the hope that healthcare and educational institutions may lead the innovation, both for their patients and the patients of private clinics, thus realizing the clinical usefulness of these interventions—with VR and AR we can make the impossible possible , 199.FC, MA, and MC conceptualized the study. FC and MC drafted the initial manuscript. AG, VM, and AM critically reviewed the manuscript for important intellectual content. FC, MC, and JE revised the final manuscript. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.VM was employed by company Softcare Studios. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


There were statistically significant differences in the incidence of GL (p = 0.04), and tooth or root fracture (p = 0.0009). Operating time was significantly lower in physics forceps than that of conventional forceps, mean difference ), Z = 3.78 (p = 0.0001), I2 = 79%. The available evidence is limited by a high risk of bias and low evidence certainty. Based on the current evidence, physics forceps might be better than the conventional extraction forceps in terms of the extraction duration, pain after extraction, trauma to both hard and soft tissue, and complications. Physics forceps are newer instruments that have not yet been introduced in the teaching of dental graduates. The introduction of physics forceps can be time saving, less invasive and reduce post-extraction complications.This systematic review and meta-analysis studied the clinical outcomes with physics forceps compared to those with conventional forceps for closed dental extraction. A systematic literature search was performed to identify all the published randomized clinical trials that compared the relevant clinical outcomes with physics forceps to those with conventional forceps for closed dental extraction. A total of 11 studies were included. The adverse events were significantly lower with physics forceps ( Dental extraction is one of the most common procedures performed by dentists. Indications for extraction are impaction, tooth or root fracture, caries, or periodontal disease . Using iA variety of new instruments and techniques have been introduced for atraumatic tooth extractions. A powered periotome and newer implant drills are useful for immediate or delayed implant placement ,10,11,12The objectives of this meta-analysis was to update the evidence comparing these two instruments and perform quantitative analysis of clinically important outcomes to present an absolute measure of effect. Additionally, a summary of findings table was constructed on the basis of the GRADE approach to ascertain the certainty of evidence, and provide a clinical recommendation based on the evidence.ClinicalTrials.gov), Google Scholar, and proceedings from major scientific meetings published by May 2020 in English language. The ClinicalTrials.gov website was searched for unpublished trials. The detailed search strategy is presented in This systematic review was registered on PROSPERO (CRD42021268530). Electronic literature search was performed on databases PubMed/Medline, Web of Science, U.S. clinical-trial registries  using the ROB 2 tool [The qualities of the included studies were assessed using criteria from the Cochrane Collaboration’s Handbook  ,23,24,25All trials were performed in India except for one, which was conducted in Iraq. The included studies were published between 2014 and May 2020, with the sample size ranging from 14 to 200. Five trials ,19,20,25n = 48) compared to with the conventional forceps (n = 120), with odds ratio 0.42 , Z = 3.78 (p = 0.0002), and I2 = 21%. There was a significant difference in the incidence of GL (p = 0.04), and tooth or root fracture (p = 0.0009).The results of the meta-analysis of adverse events are presented in p = 0.0001), and I2 = 79%.The meta-analytical results of operative time are presented in p = 0.06) and I2 = 96%). The funnel plot presented in The results of the meta-analysis of pain on the first post-operative day are presented in There was a significant reduction in adverse events (77 fewer per 1000) with the physics forceps compared to with the conventional forceps, which can be understood as 8 fewer adverse events per 100 extractions. Individually, the reduction in GL and tooth/root fracture are statistically significant with the physics forceps, but the difference did not achieve statistical significance for BCPF. This is a significant reduction in adverse clinical events with which to recommend a change in practice from regularly using the conventional to the physics forceps. The reduction in BCPF (56 fewer/1000), GL (138 fewer/1000), and tooth or root fracture (76 fewer/1000) is very promising and supports using the physics forceps over the conventional forceps. The evidence has low certainty for all the outcomes. Even the mean difference in operative time and pain on VAS favours the physics forceps with low-to-moderate certainty. The evidence for the outcomes of BCPF, GL and tooth or root fracture was very low because of inconsistencies in the measurement and the probability of selective reporting, and studies have a high risk of bias, used in the GRADE approach for the evaluation of evidence certainty .2 = 21%). For the operating time, the samples showed moderate-to-high heterogeneity (I2 = 79%). Sensitivity analysis by removing the results from Hasan and Shenoi brought the heterogeneity down to 58%. Similarly, for the pain after extraction, the samples showed high heterogeneity (I2 = 96%). Sensitivity analysis by selectively removing the studies did not resolve the heterogeneity. This high heterogeneity may be because of the subjective evaluation of pain on VAS. Although VAS is traditionally treated as a continuous outcome, it is essentially not a numerical scale, and is based on subjective perception. Similarly, various other comparative studies of physics versus conventional forceps in orthodontic extractions also showed better results for physics forceps [The physics forceps design reduces the incidence of root fractures and maintains the buccal cortical plate. This is also necessary for the success of an immediate dental implant. The forceps is an innovative extraction instrument that can perform difficult extractions without the need to reflect a flap with predictable results ,18,23. T forceps ,19,20,25 forceps .Extractions using physics forceps are less invasive than those with conventional forceps, and can be considered a reliable method, requiring significantly less comparative intraoperative time. The physics forceps requires a learning curve, but gives the clinician the unique opportunity to atraumatically undertake conventionally difficult extractions in order to maintain alveolar height, thus facilitating immediate prosthetic rehabilitation. Unlike the use of conventional forceps in training in dental schools, the physics forceps is a novel instrument, however, the learning of wrist movements and the direction of application of force is not difficult for the users of conventional forceps. The physics forceps is more efficient in reducing operating time, and preventing marginal-bone and soft-tissue loss in orthodontically indicated premolar extractions, with comparable clinical outcomes to those of the conventional forceps, associated with few complications.Physics forceps are newer instruments that have not yet been introduced in the teaching of dental graduates. Physics forceps compare well to the conventional extraction forceps in terms of extraction duration, pain after extraction, and lesser trauma to both hard and soft tissue, with fewer complications. We recommend the introduction of physics forceps in regular clinical use and the training of dental graduates. Further trials are required, especially in other population groups, to evaluate the physics forceps as a better alternative and successor to the conventional dental-extraction forceps.


Stem cell-based regenerative therapy has opened an avenue for functional recovery of patients with spinal cord injury (SCI). Regenerative rehabilitation is attracting wide attention owing to its synergistic effects, feasibility, non-invasiveness, and diverse and systemic properties. In this review article, we summarize the features of rehabilitation, describe the mechanism of combinatorial treatment, and discuss regenerative rehabilitation in the context of SCI. Although conventional rehabilitative methods have commonly been implemented alone, especially in studies of acute-to-subacute SCI, the combinatorial effects of intensive and advanced methods, including various neurorehabilitative approaches, have also been reported. Separating the concept of combined rehabilitation from regenerative rehabilitation, we suggest that the main roles of regenerative rehabilitation can be categorized as conditioning/reconditioning, functional training, and physical exercise, all of which are indispensable for enhancing functional recovery achieved using stem cell therapies. Rehabilitative therapies are performed after these procedures, but the injured spinal cord exhibits only a small degree of plasticity and functional recovery2. For more than two decades, stem cell-based regenerative therapy has been investigated as a state-of-the-art treatment that is expected to change the prognosis after SCI. Both cellular graft sources, including olfactory ensheathing cells (OECs), mesenchymal stem cells (MSCs), and neural stem/progenitor cells (NS/PCs), and tissue graft sources, including peripheral nerve and olfactory mucosa, have been investigated. Although some of these methods have proceeded to the clinical trial stage, the transplanted stem cells do not always work as we expected and thus the current data only show limited functional recovery. One factor that markedly affects the therapeutic potential is the microenvironment, which changes over time after injury3. Although many researchers reported that stem cell therapies have significant effects in the early phases, they lose their therapeutic potential in the chronic phase as neuronal plasticity decreases6. There are 50-fold more patients in the chronic phase than in the acute-to-subacute phase; therefore, it is crucial to establish strategies that can be used to treat the chronically injured spinal cord7.Spinal cord injury (SCI) results in various neurological sequelae in the motor, sensory, and autonomic systems. There is no treatment in the strict sense, only approaches to reduce secondary damage acute SCI, including surgical procedures to restabilize and decompress the spinal cord and to augment blood pressure9, has been proposed based upon preclinical12 and clinical15 research that reported a variety of mechanisms and effects on physical functions including muscle strength, gait, and the ability to perform activities of daily living (ADL)17. This concept is concisely defined as “The application of rehabilitation protocols and principles together with regenerative medicine therapeutics toward the goal of optimizing functional recovery through tissue regeneration, remodeling, or repair”8. Rehabilitation is suggested to promote functional integration of the graft and host neuronal system when combined with stem cell therapies2. However, to the best of our knowledge, regenerative rehabilitation following SCI has not been structurally summarized because research in this area is in its infancy. Therefore, this review provides an overview of the mechanisms of rehabilitation performed in combination with stem cell therapies and describes the concepts of clinical regenerative rehabilitation. In addition, we briefly introduce rehabilitative strategies more generally, independent of their combinatorial use with regenerative therapies, to provide a more integrated discussion of this area. Although regenerative medicine encompasses various treatments including cell, tissue, and organ replacement, cytokine therapy, and neurorehabilitative approaches to induce regeneration of impaired body parts and/or systems19, this review specifically deals with stem cell transplantation therapies. Rehabilitation includes physical treatments utilizing electrical stimulation, magnetic stimulation, and infrared and ultrasound treatments. Here, we focus on exercise training and physical therapies used in combination with exercise.Recently, a strategy to combine optimal rehabilitation with regenerative treatments, called regenerative rehabilitationWe searched studies in the Web of Science (BIOSIS), Medline (via PubMed), Scopus, and ProQuest databases from the beginning of 1981 to 1 July 2021. Keywords related to “spinal cord injury” and “transplantation” in combination with terms related to “rehabilitation” and “training” were used in searches for preclinical research. In addition, although some functional assessments of forelimbs require training, this training is often not described in the abstract. Therefore, we closely checked the methods sections of the studies chosen using keywords related to “forelimb” instead of “rehabilitation” to determine whether rehabilitative training was implemented. Studies in which the post-therapeutic training frequency was no less than three times per week were assembled into a table. Keywords related to “spinal cord injury” and “transplantation” limited to clinical research were applied to searches for clinical studies.20. By stimulating reorganization of rostrocaudal spinal inter-neuronal networks, a research group reported better functional recovery with quadrupedal training than with bipedal gait training in a hemisection rat model21. On the other hand, bipedal training has advantages because it explicitly trains the paretic limbs even in severe SCI animal models that tend to use forelimbs more than hindlimbs in quadrupedal gaits18, and it may be better suited for investigating the effects on the local spinal network. Cycling training involves rhythmic sensory-motor training and promotes right–left coordination along with range-of-motion exercises22. Some researchers used swimming training for incomplete SCI model rats because it is a natural behavior of this species. Although it requires simple apparatus, controlling an appropriate exercise load is difficult. Importantly, specific training paradigms to encourage voluntary stepping are more effective than entirely passive stepping23. Instrumental training promotes activity-based learning and suppresses maladaptive plasticity24. By contrast, while it remains controversial, some reports suggest there are unfavorable training conditions that may lead to the development of hypersensitivity, such as delayed initiation of running wheel training resulting in aberrant nociceptive plasticity for cervical hemi-contusion model rats25 and early initiation of passive mechanical training for moderately thoracic cord contusion model rats26. In addition, researchers have reported a trade-off relationship, the deterioration of a specific function secondary to other training targeting functions, between locomotor and forelimb dexterity tasks in rats with cervical dorsolateral quadrant lesion28 and between standing and stepping abilities in rats with dorsal rhizotomy29. This emphasizes the importance of designing optimal therapeutic strategies corresponding to the impairment model22.Owing to technical limitations, no consensus has been reached regarding rehabilitative methods in experimental animals. Interventional studies targeting hindlimb and gait function are predominantly conducted in rodents, while few studies have used minipigs, felines, and non-human primates. Many of these studies applied the thoracic cord injury model and implemented physical training including hindlimb motion due to the advantages of more accessible assessment and a higher survival rate, together with the applicability of various SCI types and their severity. Quadrupedal treadmill training was adopted in most mouse studies, while both bipedal and quadrupedal treadmills were used in rat models. Body-weight supporting apparatus is frequently applied to enable the training in animals with severe impairment. Cycling, swimming, and climbing training routines were also sometimes used in rodents. The most suitable rehabilitative method might differ between models. Quadrupedal training is called physiological gait training because it enables coordination between the forelimbs and hindlimbs. A validated and standardized training protocol was recently reported in moderate contusive SCI model mice35. A single-pellet reaching task, Whishaw reaching, involves horizontal reaching training, and a clear relationship between training intensity and improvement was recently shown in rats with cervical dorsolateral quadrant lesion36. The modified Montoya staircase task involves training for perpendicular reaching of each hand independently37. Compared with gait training, such task-specific training has advantages including a lack of confounding by off-task home cage self-training that overrides the training effect38. In addition, forelimb function has been actively investigated not only with SCI models, but also in the context of the specific contribution of a tract(s) and propriospinal neurons39.Forelimb functional recovery in animals with cervical SCI has also been investigated. Although gait analysis, climbing tasks, the cylinder test, grip strength, and object manipulation, including food-pellet reaching tasks, are applied as assessment measures, reaching tasks require training to evaluate the acquisition of dexterity40, a growing number of studies have demonstrated functional recovery induced by rehabilitative training. With regard to motor function, a variety of changes have been reported, including regeneration and reorganization of intra-spinal43 and spinal descending circuits44, enforcement of synaptic function45, axonal regeneration, and exercise-dependent plasticity46, improvements of motor control through the restoration of spinal inhibitory capacity47, sensory-motor integration, and supra-spinal control48. Expression of various neurotrophic factors50, growth factors51, and both excitatory and inhibitory molecules47 has been suggested to be involved in these changes. Neurotrophic factors have been proposed to promote neural plasticity, vascularization, and neuroprotection8. Furthermore, treadmill training reportedly promotes proliferation and migration of ependymal cells, which are considered to be a source of neural stem cells, in thoracic cord clip-compression model rats52. Although it is reported that ependymal cells do not proliferate after injury in the adult human spinal cord53, another group reported that they are activated in some humans of a certain age54 and in animal models including mouse transection SCI56. A similar beneficial effect might be induced by rehabilitation in combination with stem cell transplantation.Although the number of rehabilitative training animal models is still limited57. Muscle volume and function decrease after SCI, and the dominant muscular fiber type changes58. Importantly, disuse muscle atrophy is also reported to promote motor neuronal degeneration59. Moreover, although it is often overlooked in preclinical studies of chronic SCI, disuse-induced functional deterioration is speculated to suppress or even mask the beneficial effect of specific treatments11.Another critical role of rehabilitation is to prevent and ameliorate the negative impact of disuse due to impairments2. Very few preclinical studies have investigated the combinatorial effects of stem cell therapy and rehabilitation regardless of chronicity  to assess the synergistic effect of transplantation and rehabilitation and (2) to broaden the applications in patients with chronic SCI in whom stem cell therapy is ineffective when applied alone to asses60 did not observe any remarkable effect on rats with mild contusive thoracic SCI who received a subacute intramedullary injection of bone marrow-derived MSCs when hindlimb cycling exercise was applied at a frequency of three times per week. In 2016, Sachdeva et al.63 applied a similar training method with a higher frequency (five times per week) in spinal cord-transected rats who received a peripheral nerve graft. They found that cycling exercise strongly facilitated regeneration by propriospinal, but not sensory, neurons, accompanied by increases in mRNA expression of regeneration-associated genes. Regarding other studies that applied minimal doses, Nicola et al.61 did not find any additional effect of 10 min/day training on rats with mild thoracic SCI. Kubasak et al.62 applied incremental doses from 5 to 20 min/day and showed that functional recovery was significantly enhanced in a transection model. These results imply that rehabilitative treatments used in combination with stem cell therapy have a minimum dose threshold and that an appropriate method or strategy is required to elicit beneficial effects. Further investigations are needed to determine the appropriate dose, intensity, and training method for each SCI model.In the early study of the combinatorial treatment in 2006, Yoshihara et al.64. Sun et al. subacutely transplanted both OECs and Schwann cells into a rat with moderate contusion injury and performed bipedal BWSTT. While the activity of astrocyte-like OECs at the lesion site was not modified, they found that treadmill training significantly contributed to increased serotoninergic activity within lumbar enlargement. Locomotor function was significantly greater in the trained groups, and the effect was greater in the group that received combinatorial therapy than in the training-only group65. Hwang et al. acutely transplanted NS/PCs into the moderately contused rat spinal cord and then performed bipedal BWSTT for 8 weeks. The combinatorial approach significantly promoted graft survival and differentiation more into neurons and oligodendrocytes, which correlated with greater functional recovery than in the control groups. It also enhanced tissue protection, myelination, and restoration of serotonergic fiber innervation in the lumbar spinal cord, which the authors attributed to reduced stress caused by active oxygen or active nitrogen through insulin-like growth factor (IGF)-1 signaling12. In addition, they showed that combined rehabilitation contributed to upregulation of brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and neurotrophic factor 3 (NT-3). Massoto et al. performed MSC transplantation in the acute phase and treadmill training for 8 weeks in mice with moderate clip-compression injury. They reported better functional recovery together with a larger area of white matter, more myelinated fibers, and fewer microcavitations and degenerating nerve fibers, along with significantly increased NT-4 expression66. Younsi et al. subacutely transplanted NS/PCs into cervical contusive lesions of rats and then performed quadrupedal treadmill training for 6 weeks. Combined rehabilitation enhanced graft survival and promoted differentiation into neurons and oligodendrocytes. They further demonstrated better functional recovery together with improved myelination, descending tract regeneration, and tissue sparing following combinatorial treatment67. Sachdeva et al. performed cycling training in combination with super acute peripheral nerve grafting in a rat transection model. They found that exercise enhanced propriospinal neuronal regeneration and mRNA expression of growth-associated protein 43 (GAP43), β-actin, and Neuritin, which are responsible for neuronal regeneration, while no remarkable effect was observed on sensory neurons63. The mechanisms are briefly illustrated in Fig. With regard to the behavioral, histological, and functional aspects of hosts with acute and subacute SCI, Takeoka et al. reported that partial body-weight-supported treadmill training (BWSTT) gait exercise enhanced the effect of OEC grafts in super acute thoracic cord-transected rats. They observed that combinatorial treatments induced a fourfold increase in regenerating axons within the caudal stump of the transected spinal cord, and consequently improved hindlimb function and electrophysiological states. In addition, they found that the combinatorial effect was preserved after re-transection of the spinal cord, indicating that regenerative rehabilitation promoted the reorganization of lumbosacral circuits68 or for a short duration before every assessment69. Whereas other studies implemented the task as regular rehabilitative training after transplantation, there was no untrained groups72. Thus, to our knowledge, the specific contribution of regenerative rehabilitation to forelimb functional recovery has not been reported, and the findings described above were all obtained with gait training. Overall, the mechanism of regenerative rehabilitation has not been completely elucidated.Only some of the studies that performed the combinatorial treatment with transplantation and rehabilitation focused on training-specific effects. Consequently, these studies sometimes did not compare trained and untrained or less-trained animals. This was particularly true of studies of forelimb function that utilized pellet reaching tasks; training was usually implemented just as part of the assessment only before SCI73. While combinatorial treatment with rehabilitation is a favorable treatment option, only two studies investigated combinatorial treatment with cell transplantation and rehabilitation in the chronic phase of SCI if the 6-week rule is strictly applied11. Tashiro et al.11 studied motor and sensory recovery following transplantation in combination with rehabilitation in the chronic phase. They performed NS/PC transplantation followed by bipedal BWSTT for 8 weeks in severe contusive thoracic SCI mouse models. The mice displayed significant locomotor recovery, which corroborated the synergistic effect of the combinatorial treatment on axonal regeneration and synaptogenesis, as well as an increase in neuronal differentiation of the transplanted cells. The additive effects on immunohistological changes imply that serotoninergic activity was enhanced by transplantation and GABAergic activity was restored by rehabilitation11. They further reported amelioration of thermal allodynia and coarse touch-pressure hyperalgesia, and a reduction of calcitonin gene-related peptide-positive fibers, which function in the transmission of pain, together with upregulation of GABAergic activity in the posterior horn10. Although they demonstrated significant functional recovery upon combinatorial therapy, no pertinent differences were observed between the combinatorial treatment and rehabilitation alone groups. Thus, they concluded that an additional treatment(s) is needed to use stem cell therapies in patients with chronic SCI11. Theisen et al.22 investigated the effects of peripheral nerve grafting at 42 days post injury (DPI) in combination with cycling exercise in T12-transected rats and reported that spinal axon regeneration was enhanced after exercise. No significant difference was detected between the two exercise periods, namely, 6 weeks starting at 35 DPI and 10 weeks starting at 7 DPI. Although these outcomes were due to a combination of chronic transplantation and acute or late subacute rehabilitative interventions, we would classify the latter as chronic regenerative rehabilitation. The difference between late subacute and chronic phase SCI has not been determined in terms of rehabilitation studies. A study by the same laboratory further compared the results of chronic peripheral nerve grafting with acute interventions63 and concluded that exercise has no long-lasting or cumulative effect in terms of axonal regeneration.A consensus study concluded that 6 weeks is the minimum timeframe required to reach the chronic phase of SCI in the rodent model74. These studies imply that the effects of combinatorial treatment with rehabilitation and stem cell transplantation in the chronic phase are not inferior to those in the subacute phase with regard to sensory recovery, but the effects of transplantation on motor function decrease over time.Regarding late subacute interventions, Dugan et al. investigated the role of the local spinal inhibitory circuit upon GABAergic neuronal progenitor cell transplantation in thoracic cord clip-compression rat models. Cells were transplanted into the lumbar enlargement excluding the injury site at 28 DPI, and treadmill quadrupedal training with an incline of 8° was performed for 4 weeks. They demonstrated that neuropathic pain assessed by allodynia, hyperalgesia, and ongoing pain was ameliorated upon reduction of inflammation, as represented by upregulation of IL4 and downregulation of tumor necrosis factor α and interleukin 1β, together with increased BDNF expression. Moreover, combined rehabilitation in both the subacute and chronic phases significantly promoted the restoration of GABAergic activity, while transplantation alone did not induce remarkable changes75. Great efforts have been made to develop more effective rehabilitative treatments for patients with SCI. Researchers have reported that intensive overground walking together with training of balance function76, BWSTT77, and training of hand and reaching function78 effectively improve body function of SCI patients. It is noteworthy that multimodal rehabilitation can induce functional recovery even in patients with chronic motor-complete SCI79. It is suggested that the central nervous system (CNS) reorganizes itself during the acquisition, retention, and consolidation of motor skills. This concept is summarized as neurorehabilitation and neuroplasticity80. There might be such significant overlap between the chief mechanisms underlying the effects of stem cell therapies and neurorehabilitation that these two treatments show synergism16. Although most neurorehabilitative treatments are non-invasive, some require a neurosurgical procedure to implant epidural electrodes or an intrathecal drug administration system81.Joint range-of-motion exercise, paretic and non-paretic muscle strengthening, systemic physical capacity training, and practice of basic motions, including gait and transfer, are clinically applied as conventional rehabilitation82. BWSTT and robot-assisted gait training (RAGT) improve the gait of patients in a more accessible, faster, and safer manner than regular overground training83. Some types of RAGT include additional functions such as FES84. Brain–computer interface is a new technology that connects specific brain signals of thoughts, perceptions, and motor intent to the output device, which provides a specific response that rewards functional training or a compensatory response to the impaired body function85.Studies have reported the effects of various “peripheral” neurorehabilitative methods that target the peripheral sensorimotor system. Functional electrical stimulation (FES), including neuromuscular electrical stimulation (NMES), is a method to assist the impaired muscular function of patients using electrical stimulation. NMES assists the voluntary movements of patients by enhancing the intent of movements via timely and tuned electrical stimulation. It is utilized for the training of both gait and upper limb activities86. In addition, both non-invasive transcutaneous and minimally invasive spinal/brain stimulation has been developed owing to their direct and harmless neuromodulatory properties88. Moreover, a series of studies revealed that combinatorial treatment with intrathecal medication and monoamine agonists enhances and manipulates the effect of electrical stimulation89. The brain-spine interface was recently reported in a primate model in which an electroencephalograph was applied to control epidural stimulation patterns90. Utilizing these multimodal neurorehabilitative approaches, Asboth et al. reported a novel rehabilitative treatment in which body-weight-supported RAGT was performed in combination with spinal epidural stimulation and treatment with serotoninergic and dopaminergic agonists in a preclinical study. They further observed reorganization of the efferent circuit cortico-reticulospinal circuit, which caused rerouting of cortical projections and contributed to functional recovery44.On the other hand, the “central” neurorehabilitative method targeting the CNS has also been investigated with various means and strategies. Preclinical studies showed that direct current stimulation induces migration and proliferation of neural progenitor cells together with upregulation of neurotrophic factors91. It is noteworthy that only standard/conventional rehabilitation training was performed in studies of patients with acute and subacute SCI. This might be because preclinical research showed that stem cell therapies only induce significant functional improvement in the early phases. Therefore, researchers have no specific obligation to deliver stem cell therapy in combination with an intensive strategy or a neurorehabilitative approach using an advanced device, i.e., regenerative rehabilitation in a narrow sense.Several clinical studies of stem cell-based regenerative treatments with cellular or tissue grafting for human patients with SCI have been conducted worldwide. This section summarizes the features of rehabilitation in five studies of acute SCI, four studies of subacute SCI, 33 studies of chronic SCI, and nine studies in which the chronicity was not specified Tables  and 3. A92 reported that the quality and quantity of rehabilitation influenced the long-term outcome in patients who underwent OEC transplantation, although they did not investigate the threshold. To our knowledge, this is the only study investigating the relationship between functional recovery and the characteristics of rehabilitation after stem cell therapy.Since stem cell therapy has fewer effects on chronic SCI, combining rehabilitation attracts wide attention with its feasibility over the success in preclinical studies. Many research groups have implemented specific combined rehabilitative approaches. Furthermore, Huang et al.93.Rehabilitative interventions are often applied both before and after stem cell treatment in clinical studies involving patients with chronic SCI. We named the former “pre-rehabilitation” and the latter “post-rehabilitation”. Usually, only conventional rehabilitative methods are applied as pre-rehabilitation. Pre-rehabilitation can be categorized as mobilization of disuse-provoked impairments such as weakened and contracted muscles, homogenization of the status of patients before stem cell treatment, and identification of responsiveness to rehabilitation, which is far feasible than stem cell therapies. It is noteworthy that a study even excluded cases that showed a possibility of recovery with rehabilitation96.The majority of groups seemed to apply only conventional rehabilitation. No rehabilitative protocol was provided in most cases97.Intensive rehabilitation with the conventional method was also frequently applied. A massive dose of rehabilitation of >4–6 h per day was applied for a remarkably long duration exceeding 24 weeks up to 1 year99, early induction of training for essential motion including gait and ADL15, sensory training98, and the facilitation method13.Several researchers chose a traditional, but specific, rehabilitative approach to maximize the effect of stem cell therapy. The principles of these approaches include facilitation of physical exercise99, NMES100, Upper body circuit resistance training101, BWSTT99, and RAGT14, to be implemented.It was not rare for advanced rehabilitation, including FES99.Physical treatments including electrical field, ultrasound, and temperature gradients were also applied to induce mechanotransductive effects101.Home-based aerobic and strengthening program using dumbbell, resistance band, and upper limb ergometerRehabilitative strategies appeared in regenerative studies can be characterized into six large groups:101 utilized the talk-test to determine an intensity that made speaking uncomfortable in maintaining the appropriate intensity level. We suggest that the second, third, fourth, fifth, and sixth groups are regenerative rehabilitation in a narrow sense, whereas the first group is combined rehabilitation, i.e., regenerative rehabilitation in a broad, but not a narrow, sense.Although it is difficult to know the exercise load in home-based training, Maher et al.102. Functional training will be the core element of regenerative rehabilitation. Although researchers have elucidated various micro-mechanisms via which SCI rehabilitation, in general, promotes functional recovery at the molecular, synaptic, local circuit, tract, and even cortical levels, the number of evidence showing interaction with residual tissue or transplanted cells is few in the field of regenerative rehabilitation. It is remarkable there has been no study investigating the effect brought about by rehabilitation regarding forelimb-hand function. Physical exercise is crucial to upregulate neurotrophic factors. These factors have remarkable effects including neuroprotection, especially in the acute phase, modification of proliferation of transplanted cells and their differentiation into neurons and oligodendrocytes, and induction of host neural plasticity67. Thus, physical exercise acts like medication. However, it remains to be elucidated to what degree the functional training and the physical exercise are distinguishable; whereas these two approaches possess a different character, there is still some overlapping. Further investigations are needed.According to the mechanism revealed in preclinical and clinical studies, the roles of regenerative rehabilitation can be categorized as (i) conditioning/reconditioning, (ii) functional training, and (iii) physical exercise. Conditioning and reconditioning mainly target physical problems such as contracture, muscle atrophy, and cardiopulmonary deconditioning, which are derived from disuse due to SCI sequelae. They are even more important in the chronic phase because of the long deconditioning period64. Although stem cell therapy seems to induce only limited recovery, the additive effect of regenerative rehabilitation may be key to realizing significant motor and functional recovery following chronic SCI. However, it seems difficult for combinatorial treatments incorporating stem cell therapy and rehabilitation to outperform each individual treatment, particularly in the chronic phase15. Therefore, it is crucial to optimize regenerative rehabilitation based on the mechanisms to maximize the effects of stem cell therapy. In addition, further investigations are needed to discover a way of enhancing recovery.In the field of stem cell regenerative medicine, the role of rehabilitation is becoming increasingly important, with preclinical studies delineating the molecular mechanisms and effects. Studies of combinatorial treatment have reported synergistic effects2. Combination treatment with emerging novel technologies from the fields of bioengineering or molecular biology has evolvability either. For example, neuromodulation with multimodal therapies including spinal epidural stimulation, brain–computer interface, neuroprosthetics, and pharmacological intervention is expected to restore functional movement upon inducing plasticity of spared circuits and residual projection81. On the other hand, in vivo reprogramming technology, which enables the generation of new neurons from non-neuronal cells via reprogramming, was recently developed, which is proposed as a novel regenerative strategy103. While no study has combined these groundbreaking technologies with stem cell therapy or rehabilitation, to the best of our knowledge, we believe that such extended regenerative rehabilitative strategies will further broaden the therapeutic potential of SCI.To date, researchers are pointing out the therapeutic potential to combine stem cell therapy and rehabilitation with pharmacological treatments as represented by neurotrophic factors and reagents against axonal growth inhibitorSupplementary Information


A tele-rehabilitation platform was developed to improve access to ambulatory rehabilitation services in Hong Kong. The development was completed in October 2019 and rolled out for use to occupational therapists, physiotherapists, and speech therapists. During the COVID-19 pandemic, rehabilitation services were severely interrupted. Tele-rehabilitation was used extensively to meet the demand for rehabilitation service delivery.The aims of this study were to (1) describe the design and development process of a tele-rehabilitation service, and (2) study how the tele-rehabilitation platform was used to overcome the disruption of rehabilitation service during the COVID-19 pandemic.Tele-rehabilitation was developed utilizing 4 core determinants of Unified Theory of Acceptance and Use of Technology as guiding principles. A generic prescription platform, called the activity-based prescription system, and a mobile app, called the Rehabilitation App, were built. Five outcomes were used to examine the utilization of tele-rehabilitation both before and during the pandemic: throughput, patient demographic, patient conditions, workforce, and satisfaction from patients and staff.There was a tremendous increase in the use of tele-rehabilitation during pandemic. The total number of patients (up until July 2020) was 9101, and the main age range was between 51 to 70 years old. Tele-rehabilitation was used for a much wider scope of patient conditions than originally planned. More than 1112 therapists, which constituted 50.6% of the total workforce (1112/2196), prescribed tele-rehabilitation to their patients. Moreover, there was a high satisfaction rate from patients, with a mean rating of 4.2 out of 5, and a high adherence rate to prescribed rehabilitation activities .The findings of our study suggested that tele-rehabilitation in the form of a generic prescription platform and mobile app can be an effective means to provide rehabilitation to patient. During the COVID-19 pandemic, tele-rehabilitation has been used extensively and effectively to mitigate service disruption. Our findings also provide support that there is a high level of satisfaction with tele-rehabilitation; however, a longer duration study is required to demonstrate the sustained use of tele-rehabilitation, especially after the pandemic. The Hospital Authority is the statutory body responsible for managing public health services in Hong Kong. The Hospital Authority provides over 90% of inpatient care and 30% of outpatient care and is the major provider of rehabilitation service to Hong Kong citizens . The HonTo overcome service bottlenecks, especially those for patients after stroke, patients after hip fracture, and older adult patients with frailty, the report  recommenTele-rehabilitation refers to the provision of rehabilitation service at a distance using telecommunication technology as the service delivery medium. It is an alternative means of providing all aspects of care including interviews, physical assessments, diagnoses, interventions, maintenance activities, consultations, education, and training to patients in a remote location . Tele-reThe tele-rehabilitation platform’s development was completed in October 2019. The aim of its development was to provide therapists with a new form of service delivery. Since mid-January 2020, COVID-19 has affected Hong Kong and in late January 2020 rehabilitation services delivery became seriously disrupted, with a 50% drop in attendance. To combat the disruption of service, occupational therapists, physiotherapists, and speech therapists extensively utilized the tele-rehabilitation platform from mid-February 2020 onward, and its content expanded rapidly from early March 2020 onward, gathering momentum during the COVID-19 outbreak.The aims of this study were to describe the design and development process of the tele-rehabilitation platform and investigate how the tele-rehabilitation platform was used to overcome the disruption of rehabilitation services during the COVID-19 pandemic.Performance expectancy is defined as the degree to which an individual believes that the use of the new system will help them improve their job performance. Effort expectancy is defined as the degree to which a person perceives the system as easy to use. Social influence is defined as the degree to which an individual perceives that important others believe they should use an information system. Organizational facilitating condition is defined as the degree to which an individual believes an organizational and technical infrastructure exists to support the use of the system. These determinants applicable to technology acceptance by health care workers [A technology or innovation can only be considered useful if it is accepted and used in daily clinical practice. There are several criteria to consider in predicting whether target users will actually use the technology. The Unified Theory of Acceptance and Use of Technology , based o workers . These 4Focus groups were formed to work in close collaboration with physiotherapists, occupational therapists, and speech therapists. An agile approach was used; therapists could test the prototypes during regular focus group meetings and provide feedback. Moreover, patients were invited to try the mobile app and provide comments on a regular basis for continuous user interface improvements.Tele-rehabilitation has been used for patients after stroke -16, in cAfter thorough discussions, it was decided that a new prescription platform and a mobile app would be developed. The utilization of a mobile app in tele-rehabilitation has been supported in many studies ,31. AfteThe Clinical Management System is the electronic medical record that all therapists in Hospital Authority use daily for clinical practice to disseminate health care information or clinical data and enhance patient care . The actA therapist could complete a prescription with a few clicks. Altogether, 144 videos were incorporated into the ABPS. The ABPS was designed as a generic prescription platform to allow the future addition of training videos and reminders and future inclusion of more allied health professions.Patients using tele-rehabilitation could be older adults who may have cognitive impairment or poor memory. Thus, the mobile app was designed to be simple and barrier-free. If a therapist prescribed a training video to a patient, a notification would be pushed to the app at the prescribed time. A swipe on the notification message could trigger the training video without having to log in to the app . The patOccupational therapist, physiotherapist, and speech therapist staff committees were engaged to encourage therapists to participate in design, testing, and use. Senior management also expressed that tele-rehabilitation was a corporate direction, and therapists were encouraged to use this new technology. During the rollout of tele-rehabilitation, onsite support was provided to all hospitals. In addition, user guides and support hotline were provided to therapists and training videos were made available to patients to ensure adequate support to both therapists and patients.Privacy and data security were essential concerns in the development of tele-rehabilitation . Data onWe compared tele-rehabilitation use before and during the COVID-19 outbreak. Analysis before the outbreak analysis pertained to the period from October 2019 to January 2020, and analysis during outbreak period analysis pertained to the period from February 2020 to July 2020.We collected 5 outcomes: throughput, the prescription rate of tele-rehabilitation; patient demographics; patient conditions for which tele-rehabilitation was prescribed; utilization rates by occupational therapists, physiotherapists, and speech therapist; and staff and patient satisfaction.Satisfaction surveys were prepared and forwarded to both therapists and patients for collecting their opinion on the Rehabilitation App. The format of the surveys was discussed in the focus group. Therapists suggested that the surveys should be simple and require only a short time to complete. The survey for the therapists consisted of 8 questions while the survey for patients consisted of 4 questions. A 5-point scale was use in the survey . A prompt was shown on ABPS 30 days after the therapist started prescribing with the platform. The prompt contained a reminder to complete the survey. For patients, 7 days before their prescribed rehabilitation activity ended, a prompt was shown in Rehabilitation App to invite the patient to complete the survey.P values less than .05 were statistically significant. When significance was found, the adjusted residual value was calculated. Statistical significance was set as <–1.96 and >1.96 . All data were analyzed using SPSS statistical software .Patient demographic, workforce, and patient condition variables were nonparametric categorical data; therefore, chi-square analysis was used. Physiotherapy added 41 musculoskeletal training videos in early March and 15 additional musculoskeletal training videos in April. Speech therapy added 8 swallowing training videos in mid-March. Occupational therapy added 8 pulmonary training videos in early April. A total of 72 videos were added from February to April.The number of prescriptions per month showed a slightly decrease from October 2019 to January 2020. The number of new patients per month increased to 462 in February 2020 and spiked to 2024 in March 2020. The total number of patients prescribed accumulated to 9101  by the eP=.83) or age distribution (above and below 60 years: P=.36).The Rehabilitation App was designed for adult patients, and the age of prescribed patients ranged from 18 to 106 years old. Age group analysis of patients revealed that before the outbreak, the age group with the highest prescription rate was 61 to 70 years . During P=.998).Speech therapy had a relatively simple patient condition distribution; the main conditions were head and neck diseases, stroke, neurological conditions, neurosurgery, and cancer. Stroke and head and neck disease remained the largest case group for speech therapy throughout . The meaP=.93).Occupational therapy had several major patient condition groups including stroke, neurological conditions, weakness and deconditioning, pain and injury, cancer, and fractures . Stroke-other conditions comprised a large variety of musculoskeletal conditions including soft tissue problems and degenerative problems and occupied the highest percentage before and during the outbreak. The mean number of prescriptions per month before the outbreak was 174, and the mean increased to 1015 per month during the outbreak. The average number of prescription per month increased after the outbreak  (P=.04). There were statistically significant decreases in weakness and deconditioning  and neurological condition ; (2) statistically significant increase in lower back pain , pain and injury , and neck pain . This was also demonstrated by the percentage change in distribution in these conditions.Physiotherapy had a diverse patient conditions distribution. There were several conditions including stroke, weakness and deconditioning, fracture hip, pain and injury, neurological conditions, and low back pain . The mos4 / 174) . There wP=.001) and physiotherapists (P<.001), and no statistically significant difference for speech therapists (P=.45). Further analysis by adjusted residual value demonstrated that there were differences in prescriptions between occupational therapist II and senior occupational therapist and between physiotherapist II, physiotherapist I, and senior physiotherapist  prescribed tele-rehabilitation to patients, which constituted 50.6% (1112/2196) of the total workforce. Physiotherapy and occupational therapy had a 3-tier rank structure . Rank II was the entry rank, and rank I was the middle rank. Speech therapy had a 2-tier rank structure (basic and senior). Speech therapists had the highest overall prescription rate . There were statistically significant differences in prescriptions by rank for occupational therapists . Originally, tele-rehabilitation was designed to treat patients with stroke, patients with hip fracture, and older adults with frailty. Our study showed that tele-rehabilitation can be used for a much wider spectrum of patient conditions. The generic design of the tele-rehabilitation was able to expand training content and cope with the service demand for rehabilitation during the outbreak period.Tele-rehabilitation utilization reached a peak in March 2020 during the first wave of outbreak in Hong Kong. Tele-rehabilitation use dropped from 2024 new patients in March to approximately 1300 per month from April to July. The stable trend indicated that tele-rehabilitation was used irrespective of number of confirmed COVID-19 cases. Continuous monitoring is needed to study the sustainability of utilization and especially during the postpandemic phase.Our study showed that there was no difference in distribution between patients above or below 60 years old. This finding echos those of Crotty et al —the age P=.001) and physiotherapy (P<.001), and there was an apparent difference in the prescription rate of tele-rehabilitation among the 3 allied health professions . Speech therapy had the most severe disruption in service during the outbreak, which could be attributed to the high rate of prescription. There was a highest absolute number of prescriptions among physiotherapist. This was attributable to fact that physiotherapy had the largest workforce, and there was extensive use of tele-rehabilitation for musculoskeletal conditions. The differences, however, also raised the question of whether tele-rehabilitation was equally suitable to different allied health services. For example, tele-rehabilitation in the form of a video may not fit activities of daily living training, which requires the use of tools and equipment. Whereas for physical training prescribed by physiotherapist and oral-motor training prescribed by speech therapists, video training is a suitable format.Analysis of workforce data demonstrated that 50.6% of the total workforce (1112/2196) prescribed tele-rehabilitation. There was significant difference in prescription rate between basic and senior ranks in occupational therapy . These findings aligned well with the initial goals of the tele-rehabilitation platform. However, we noticed that hip fracture ranked rather low in the prescription rate for both physiotherapists and occupational therapists which was surprisingly not aligned with the objectives of the platform’s development. On the other hand, both physiotherapists and occupational therapists prescribed tele-rehabilitation for a broad spectrum of clinical conditions. There was a significant increase in prescriptions to musculoskeletal conditions of lower back pain , neck pain , and pain and injury . The results demonstrate that tele-rehabilitation is indicated for a broad spectrum of patient conditions.A generic design was adopted for both the ABPS and mobile app. This facilitated rapid expansion of training content. Previous studies ,21,26,31The COVID-19 pandemic has altered health care delivery globally. Severe restrictions such as social distancing and the suspension of rehabilitation services were enacted to prevent spread of disease. The World Health Organization recommended postponing treatments that were not considered urgent in order to ensure safety, while still guaranteeing the essential rehabilitation services . The pantrain the trainer model can be a feasible to allow rapid staff development to enable trained staff to onboard others in the use of tele-rehabilitation [Through the advent of technology, faster internet connection, cheaper smart devices (smartphones and tablets), and new software being available, tele-rehabilitation is able to offer many benefits. However, there are challenges ahead if tele-rehabilitation is to be used extensively in the future. For example, the use of tele-rehabilitation is a paradigm shift for therapists from conventional face-to-face interventions. During the outbreak, there was a rapid increase in the number of therapists who needed to prescribe tele-rehabilitation. Consequently, training and accrediting staff to use tele-rehabilitation became essential. A litation . There wlitation . Moreovelitation ,39.The COVID-19 pandemic will not affect the acute outbreak period alone but may also create a serious backlog for rehabilitation in the postpandemic recovery period, which is referred to as “care debt .” To traThis observational study has a number of limitations. This study only reports outcomes of tele-rehabilitation utilization before and during outbreak periods. It does not cover the clinical effectiveness of tele-rehabilitation to patients; this requires additional well-powered clinical studies. The Unified Theory of Acceptance and Use of Technology  is used The COVID-19 pandemic has seriously affected rehabilitation service delivery. Our study has shown that a tele-rehabilitation platform was used extensively and effectively during the outbreak period to mitigate service disruption. In addition to the original targeted conditions (stroke and hip fracture), tele-rehabilitation was prescribed for a large variety of clinical conditions. The tele-rehabilitation platform, though it cannot replace all face-to-face rehabilitation services, has demonstrated its potential during the COVID-19 crisis and has promising potential to become a sustainable service delivery model.