Co-implantation of bone marrow mesenchymal stem cells and chondrocytes increase the viability of chondrocytes in rat osteo-chondral defects

Replacement of chondrocytes by adult stem cells was believed to improve the performance of autologous chondrocytes transplantation, since less chondrocytes were needed. Previous studies have demonstrated that the increased cartilage production in pellet co-cultures of chondrocytes and bone marrow mesenchymal stem cells (BMSCs) is due to the trophic effects of the MSC by stimulating chondrocyte proliferation and matrix production. However, the destination of MSCs or chondrocytes after implanted in osteo-chondral defects is not clear. The aim of the present study is to investigate the viability of MSCs and chondrocytes after co-implantation into a rat osteo-chondral defect model. MSCs were isolated from bone marrow and chondrocytes were extracted from knee joints of neonatal rats. Results of sulfated glycosaminoglycans (GAG) and collagen quantification demonstrated that co-culture pellets of BMSCs and chondrocytes have more GAG deposition than that of BMSCs or chondrocytes alone. Tracking cells with fluorescence protein demonstrated that MSCs disappeared following co-culture. In a rat knee injury model, co-implantation of BMSCs and chondrocytes contained more viable chondrocytes than chondrocytes implanted alone. To conclude, BMSCs were replaced by chondrocytes in pellet co-culture and BMSCs increased the viability of chondrocytes following co-implantation in a osteo-chondral defects model. Co-implantation of BMSCs and chondrocytes may be a promising approach to repairing osteo-chondral defects in the clinical setting.