[Cx43 silencing inhibits mechanical stress-induced apoptosis in mouse articular chondrocyte]

To explore the effect of connexin 43 (Cx43) silence on the apoptosis in mouse chondrocyte under mechanical stress.
 Methods: Mouse chondrocyte ATDC5 cells were divided into a control group, a mechanical stress group, a Cx43 siRNA transfection group, a scramble siRNA transfection group, a mechanical stress+scramble group, and a mechanical stress+siCx43 group. Flexcell FX-5000 system was used to produce mechanical stress on ATDC5 cells cultured in vitro. The mRNA and protein level of Cx43 was detected by quantitative RT-PCR (RT-qPCR) and Western blot. The cell activity and cell apoptosis was detected by cell counting kit-8 (CCK-8) method and flow cytometry, respectively. Caspase-3 activity was detected by colorimetric assay. The protein expression of Bcl-2, Bax, p-JNK and JNK was detected by Western blot.
 Results: Mechanical stress upregulated the mRNA and protein expression of Cx43 (both P<0.05). Transfection of Cx43 siRNA significantly decreased Cx43 mRNA and protein level (both P<0.05). After stimulation with mechanical stress, chondrocyte viability was significantly decreased, whereas cell apoptosis and caspase-3 activity were increased (both P<0.05). Mechanical stress obviously upregulated Bax protein level, and downregulated Bcl-2 protein expression and Bcl-2/Bax (both P<0.05). Cx43 siRNA transfection significantly increased cell viability, inhibited cell apoptosis and caspase-3 activity (both P<0.05). Cx43 siRNA also inhibited Bax expression, and increased the Bcl-2 protein expression and Bcl-2/Bax (both P<0.05). Furthermore, Cx43 siRNA significantly suppressed the p-JNK expression induced by mechanical stress (P<0.05).
 Conclusion: Cx43 silence inhibits mechanical stress-induced apoptosis in chondrocyte, which might be mediated by JNK signaling pathway.