[Promoting effect of thrombin on proliferation of bone marrow-derived mesenchymal stem cells and its mechanisms]

This study was aimed to investigate the growth-promoting activity of thrombin on mesenchymal stem cells (MSC) and its mechanisms. Human bone marrow MSC were cultured in serum-free medium supplemented with graded concentrations of thrombin, and the proliferation status of MSC was detected by MTT test. The expression levels of protease-activated receptors (PAR) and c-MYC gene were detected by PCR. Activated Akt signaling pathway was revealed by Western blot, and specific inhibitors of the signaling pathways were used to confirm the effects. The results showed that thrombin stimulated MSC proliferation in a dose-dependent manner; the minimal concentration of thrombin for stimulating MSC growth was 0.5 U/ml, and the promoting effect reached its maximum when thrombin at a dose of 8 U/ml was employed. PCR results showed that MSC expressed the two types of PAR1 and PAR2. After PAR1 was blocked with a specific inhibitor SCH79797, the growth-promoting effect of thrombin was inhibited, while this phenomenon was not observed when MSC were exposed to FSLLRY-NH2, a specific inhibitor for PAR2. Further experiments showed that after exposure to thrombin, the AKT signaling pathway in MSC was promptly activated, and c-MYC expression was greatly up-regulated. Meanwhile, when LY294002, a specific AKT inhibitor, was added into the culture medium, the up-regulation of c-MYC expression was reduced, accompanied by the low rate of MSC growth. It is concluded that thrombin can stimulate MSC proliferation by eliciting PAR1-mediated AKT activation and subsequent up-regulation of c-MYC expression.