In nude mice vivo chondrogenesis of BMSCs induced by Co-transplantation of BMSCs and chondrocytes

Objective To test the hypothesis that chondrocytes can promote in nude mice vivo chondrogenic differentiation and chondrogenesis of BMSCs at non-chondrogensis site. Methods We separated BMSC and cartilage cells from SD rats and cultured them. The supernatant of cartilage culture was separated as the BMSC inducing solution, and used to induce differentiation of the cells from the 2nd generation. Samples were taken 7 days later, and immunohistochemistry was applied to determine the expression of specific type Ⅱ cartilage collagen. RT-PCR was adopted to detect the expression of type Ⅱcollagen and aggrecan mRNA Porcine BMSCs and auricular chondrocytes were mixed at different ratios (7:3) and 5.0×107 mixed cells/ml were suspended in chitosan,and then the mixture was imbed into nude mice subcutaneously as experimental groups. Chondrocytes or BMSCs at the same cell number were mixed imbeded respectively as controls. 1.5 ×107 chondrocytes were imbeded as low concentration chondrocyte control. All samples were collected at 8 weeks post-injection. Results All specimens in experimental groups and chondrocyte group formed mature cartilage with collagen II expression. In contrast, specimens in BMSC group showed mainly fibrous tissue. Only a small amount of cartilage was formed in specimens of low concentration chondrocyte group. Conclusion These results indicate that chondrocytes can promote in vivo chondrogenic differentiation and chondrogenesis of BMSCs .