A Full-scaled Tissue Engineering Graft for Osteochondral Regeneration raw data
Description
In this study we endeavoured to develop a full-scaled osteochondral graft with LhCG as the cartilage phase, PLGA scaffold as the subchondral phase, and a naturally formed interpentration network (IPN) that mimics the cartilage-bone interface. The IPN in the graft is formed by spontaneous migration of chondrocytes in LhCG into the porous PLGA scaffold. The decellularization potential of the full-scaled osteochondral graft will also be investigated in this study. Collectively we have developed both cell-laden and decellularized full-scaled tissue engineered graft with a naturally formed cartilage-bone interpenetration zone and investigated their potential to repair traumatic osteochondral lesions. The anisotropic graft is characterized for its microarchitecture and biochemical composition. The osteochondral lesion repair capability was investigated within a rabbit osteochondral defect model by examining the mechanical property and biological property of the regenerated tissue. The PLGA-SMS subchondral layer was integrated with scaffold-free cartilage layer sandwiching a transition zone to establish the cartilage-bone interface. Gelation of chondral layer on top of the porous subchondral bone layer mimics the osteochondral gradient in terms of biochemical composition and its micro-architecture. The secretion of ECM from native chondrocytes and the migration of chondrocytes into the porous SMS scaffold formed the layer specific osteochondral tissue zonal structure naturally. The decellularized version of the graft has been successfully derived as confirmed by the removal of cellular component and retention of ECM composition and its morphology. In the untreated defect no regeneration was observed in the cartilage layer and the tissue gradually degenerated. On the other hand, the biomimetic gradient LhCG+ scaffold exhibited superior tissue coverage at the defect macroscopically. Furthermore, histological analysis demonstrated the regeneration of both subchondral bone and cartilage tissue as evidenced by the same phenotype of neo-tissue when compared with the native healthy osteochondral tissue in the same zonal region. In addition, confined subchondral bone formation with bone volume to total defect volume similar to the native tissue was observed in the LhCG+ graft after 100 days of implantation within the animal model studies. Among the two types of graft, LhCG+ demonstrated a significantly higher Young’s modulus which suggested stronger load-bearing capacity of regenerated neo–tissue which is approximately 70% of native tissue mechanical strength. These results suggested that the engineered osteochondral mimetic cell laden full-scaled graft that comprises of cartilage layer, subchondral bone layer and gradient interface showed strong regenerative capabilities to repair osteochondral tissue defects.