In vivo chondrogenesis of BMSCs induced by co-transplantation of BMSCs and chondrocytes

Objective To test the hypothesis that chondrocytes can promote in vivo chondrogenic differentiation and chondrogenesis of BMSCs at non-chondrogensis site.Methods Porcine BMSCs and auricular chondrocytes were mixed at different ratios (6∶4 or 7∶3) and 2.5×107 mixed cells were suspended in 0.5 ml 30% Pluronic F-127,and then the mixture was injected into nude mice subcutaneously as experimental groups.Chondrocytes or BMSCs at the same cell number were mixed with 0.5 ml Pluronic and injected respectively as controls.0.75×107 chondrocytes were mixed and injected as low concentration chondrocyte control.All samples were collected at 8th week post-injection.Results All specimens in experimental groups and chondrocyte group formed mature cartilage with collagen Ⅱ expression.Mature lacuna structures and metachromatic matrices were also observed in these specimens with the same level of GAG contents (about 10 mg/g).Average wet weight of specimens in experimental groups (320±48 mg and 294±37 mg respectively) was over 70% of that in chondrocyte group (418±33 mg).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 and the average wet weight was below 30% of that in chondrocyte group.Conclusion Chondrocytes can promote in vivo chondrogenic differentiation and chondrogenesis of BMSCs at non-chondrogenesis sites.