Overexpressing Runx2 of BMSCs improve the repairment of knee cartilage defects.

BACKGROUND Recruitment of gene modify bone marrow mesenchymal stem cells (BMSCs) has been considered an alternative to single cell injection in articular cartilage repair. PURPOSE The aim of this study was to investigate the effect whether of runt-related transcription factor 2(Runx2) overexpression bone marrow mesenchymal stem cells in vivo could improve the quality of repaired tissue of a knee cartilage defect in a rabbit model. METHODS Thirty-two New Zealand rabbits were randomly divided into four groups.The blank group (Con) don't received anything, the model group (Mo) was administered saline, the simple stem cell group (MSCs) received MSCs injection, the Runx2 transfection group (R-MSCs) received Runx2 overexpression MSCs injection. After adapting to the environment for a week, a 5 mm diameter cylindrical osteochondral defect was created in the center of medial femoral condyle. Cell and saline injections are performed in the first and third weeks after surgery. The cartilage repair was evaluated by macroscopically and microscopically at 4 and 8 weeks. RESULTS Macroscopically, defects were filled and surfaces were smoother in the MSCs groups than in the Mo group at 4 weeks. Microscopically, the R-MSCs group showed coloration similar to surrounding normal articular cartilage tissue at 8weeks in masson trichrome staining. The COL-Ⅱ, SOX9 and Aggrecan mRNA expression of MSCs was enhanced at 4 weeks compared with R-MSCs, then the expression reduced at 8 weeks, but was still higher than Mo group level (P<0.05). The western blot examination revealed that the COL-Ⅱand SOX9 expression of MSCs was higher than R-MSCs at 4 weeks, then the expression reduced at 8 weeks, but was still higher than Mo level (P<0.05). The IL-1β content in joint fluid also revealed that cartilage repair with R-MSCs was better than that with MSCs at 8 weeks (P<0.05). CONCLUSIONS The R-MSCs group showed cellular morphology and arrangement similar to surrounding normal articular cartilage tissue, Runx2 overexpression of MSCs resulted in overall superior cartilage repair as compared with MSCs at 8 weeks.