Repair of large articular cartilage defects with implants of autologous mesenchymal stem cells seeded into beta-tricalcium phosphate in a sheep model.

Tissue engineering has long been investigated to repair articular cartilage defects. Successful reports have usually involved the seeding of autologous chondrocytes into polymers. Problems arise because of the scarcity of cartilage tissue biopsy material, and because the in vitro expansion of chondrocytes is difficult; to some extent, these problems limit the clinical application of this promising method. Bone marrow-derived mesenchymal stem cells (MSCs) have been proved a potential cell source because of their in vitro proliferation ability and multilineage differentiation capacity. However, in vitro differentiation will lead to high cost and always results in decreased cell viability. In this study we seeded culture-expanded autologous MSCs into bioceramic scaffold-beta-tricalcium phosphate (beta-TCP) in an attempt to repair articular cartilage defects (8 mm in diameter and 4 mm in depth) in a sheep model. Twenty-four weeks later, the defects were resurfaced with hyaline-like tissue and an ideal interface between the engineered cartilage, the adjacent normal cartilage, and the underlying bone was observed. From 12 to 24 weeks postimplantation, modification of neocartilage was obvious in the rearrangement of surface cartilage and the increase in glycosaminoglycan level. These findings suggest that it is feasible to repair articular cartilage defects with implants generated by seeding autologous MSCs, without in vitro differentiation, into beta-TCP. This approach provides great potential for clinical applications.