To investigate connexins43 (Cx43) expression and its effect on chondrogenesis in the cocultures of bone marrow mesenchymal stromal cells (BMSCs)with articular chondrocytes (ACs).

The second passage BMSCs and ACs from New Zealand white rabbits were cocultured at the ratio of 3∶1 (BMSCs to ACs) for 21 days in vitro. The coculture patterns included the cell-cell contact coculture in the 24-well plates as experimental group and the cell-cell noncontact coculture through a Transwell chamber as control group. Cx43 inhibitor 18-ɑ glycyrrhetnic acid (GA) 50 μmol/L was supplemented in each group and subsequently cocultured for 21 days. Levels of glycosaminoglycans (GAG) in the medium supernatants of each group were detected by enzyme linked immunosorbent assay (ELISA). Expression of Cx43 and type Ⅱ collagen a1 (COL2a1) in the each group were analyzed using immunocytochemistry staining (ICC) and Western blotting.

GAG levels of the medium supernatants, expression of Cx43 and COL2a1 were significantly high in the experimental group compared with control group [(327.517±24.612) ng/L vs. (171.612±13.163) ng/L, t=13.683, P<0.05; 0.694±0.036 vs. 0.522±0.036, t=8.203, P<0.05; 0.684±0.046 vs. 0.415±0.039, t=10.915, P<0.05]. Following addition of 50 μmol/L GA in each group, GAG levels and COL2a1 expression were not significant difference between the contact coculture group and the noncontact coculture group [(144.671±5.229) ng/L vs. (138.270±5.542) ng/L, t=2.058, P>0.05; 0.240±0.028 vs. 0.223±0.026, t=1.086, P>0.05], whereas these all decreased significantly (t=17.541, 6.015, P<0.05) and Cx43 expression (0.671±0.029, 0.505±0.030) showed no significant change compared with cocultures without GA supplementation (t=1.454, 1.139, P>0.05).

Expression of Cx43 increases and Cx43 promotes chondrogenesis in contact coculture of BMSCs with ACs, which plays a major role in the regulation of chondrogenic differentiation.

Bone marrow mesenchymal stem cell; Chondrocyte; Coculture; Connexins 43; Chondrogenesis