Background: Engineered diaphragmatic repair has been proven viable experimentally. Under FDA oversight, we aimed at examining long term local and systemic safety, as well as efficacy, of an engineered diaphragmatic tendon graft built within clinically admissible guidelines, as a regulatory pre-requisite for human trials of this methodology.
Methods: Newborn lambs (n=27) underwent partial diaphragmatic replacement with either a Teflon patch; a clinically allowable, trilayered composite acellular bioprosthesis; or the same bioprosthesis seeded with autologous amniotic mesenchymal stem cells, expanded and processed under Good Manufacturing Practice guidelines (unlabelled, per the FDA). Comprehensive hematologic and serum chemistry tests were performed at various time points post-operatively. Animals were killed at 7, 10 and 14 months (ovine adulthood) post-implantation, for multiple additional safety and efficacy analyses. Results: There was no mortality or abnormalities in any of the blood tests or full body autopsy specimens. There were significantly higher re-herniation (P=0.014) and overall failure (re-herniation or eventration; P=0.012) rates in acellular bioprosthesis compared to engineered grafts, with no significant differences between acellular and Teflon implants. Modular tensile strength and total collagen levels were significantly higher in engineered than in acellular bioprosthesis (P=0.016 and 0.003, respectively). Lysozyme and myeloperoxidase immunohistochemistries were unremarkable in all grafts.
Conclusion: In a long-term large animal model, diaphragmatic repair with a clinically viable autologous tendon engineered with amniotic mesenchymal stem cells leads to improved outcomes when compared with an equivalent acellular bioprosthesis, with no local or systemic adverse effects. Clinical trials of engineered diaphragmatic repair appear practicable within regulatory guidelines.