Engineering Human TMJ Discs with Protein Releasing 3D Printed Scaffolds
The temporomandibular joint (TMJ) disc is a heterogeneous fibrocartilaginous tissue positioned between the mandibular condyle and glenoid fossa of the temporal bone, with important roles in TMJ functions. Tissue engineering TMJ discs has emerged as an alternative approach to overcoming limitations of current treatments for TMJ disorders. However, the anisotropic collagen orientation and inhomogeneous fibrocartilaginous matrix distribution present challenges in the tissue engineering of functional TMJ discs. Here, we developed 3 dimensional (3D) printed anatomically correct scaffolds with region variant microstrand alignment, mimicking anisotropic collagen alignment in the TMJ disc and corresponding mechanical properties. Connective tissue growth factor (CTGF) and transforming growth factor beta 3 (TGFb3) were then delivered in the scaffolds by spatially embedding CTGF or TGFb3 encapsulated microspheres (uS) to reconstruct the regionally variant fibrocartilaginous matrix in the native TMJ disc. When cultured with human mesenchymal stem/progenitor cells (MSCs) for 6 wk, 3D printed scaffolds with CTGF/TGFb3 uS resulted in a heterogeneous fibrocartilaginous matrix with overall distribution of collagen rich fibrous structure in the anterior/posterior (AP) bands and fibrocartilaginous matrix in the intermediate zone, reminiscent of the native TMJ disc. High dose of CTGF/TGFb3 uS (100 mg uS/g of scaffold) showed significantly more collagen II and aggrecan in the intermediate zone than a low dose (50 mg uS/g of scaffold) Similarly, a high dose of CTGF/TGFb3 uS yielded significantly higher collagen I expression in the AP bands compared with the low dose and empty uS. From stress relaxation tests, the ratio of relaxation modulus to instantaneous modulus was significantly smaller with CTGF/TGFb3 uS than empty uS. Similarly, a significantly higher coefficient of viscosity was achieved with the high dose of CTGF/TGFb3 uS compared with the low dose and empty uS, suggesting the dose effect of CTGF and TGFb3 on fibrocartilage formation. Together, our findings may represent an efficient approach to engineering the TMJ disc graft with anisotropic scaffold microstructure, heterogeneous fibrocartilaginous matrix, and region dependent viscoelastic properties.
Journal of dental research