To investigate the effect of down-regulation of microRNA-564(miR-564) gene on chondrogenic differentiation of synovial mesenchymal stem cells.

The third passage of SMSCs was used for the experiment. The experimental design was as follows: the blank group of SMSCs; the control group of miRNA inhibitor transfected with SMSCs; the experimental group of miR-564 inhibitor transfected into SMSCs. The three groups were cultured and induced for chondrogenesis. The histomorphology of chondrocytes was observed and the three cell proliferation curves were detected within 7 d before induction. Finally, the cartilage differentiation-specific genes and proteins in the three groups of SMSCs were detected, including collagen, proteoglycan, sex related Y protein-box 9(Sox 9), SMAD family member 4(Smad4). All the data were analyzed by one-way ANOVA test.

The morphology and characteristics of the cells were consistent with chondrocytes. The experimental group showed more cells and the toluidine blue staining of the experimental group was more obvious. The proliferation rate of the experimental group was significantly higer than that of the control group (F=0.842, P<0.01). Reverse transcription-PCR(RT-PCR) and western blot showed that the specific genes and protein expression of chondrocyte differentiation in the experimental group were significantly higher than those in the control group (F=2 274.75, F=447.31, F=30 476.22; all P <0.01), and the key genes of TGF-BMP signaling pathway(TGF-BMP)and Smad 4 protein increased significantly in the experimental group(F=457.02, P <0.01).

Down-regulation of miR-564 gene expression could promote the proliferation and differentiation of synovial mesenchymal stem cells into chondrocytes, and may be achieved by the action of TGF-BMP pathway.