MTOR signaling pathway-mediated autophagy involved in inhibition of osteoblast differentiation induced by cadmium in human bone marrow mesenchymal stem cells

Abstract

Objective: To investigate the role of autophagy mediated by mTOR signaling pathway in the inhibition of osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) induced by cadmium. Methods: HBMSCs were divided into 0, 2.5 or 5.0 μmol/L groups according to the exposure dose of cadmium chloride (CdCl2), and each group was treated for 1 day, 4 days and (or) 7 days. The ALP activity and mRNA and protein expression levels of osteogenesis markers (ALP, RUNX2 and OSTERIX), autophagy-related proteins (LC3 and Beclin-1) and mTOR signaling pathway related proteins (mTOR, p-mTOR and p-p70S6K) expression, alkaline phosphatase staining and alizarin red staining were detected. MHY 1485 was selected as the signaling pathway activator. The control group, CdCl2 group (5.0 μmol/L), MHY 1485 group and CdCl2+MHY 1485 combined treatment group were set. After 7 days of treatment, the expression levels of autophagy related proteins and mTOR signaling pathway related proteins of hBMSCs in each group were detected. Results: There was no significant difference in ALP activity between 0, 2.5 and 5.0 μmol/L groups on day 1 and 4 (P>0.05); On day 7, compared with the 0 μmol/L group, the ALP activity, expression of osteogenic markers (ALP, RUNX2, OSTERIX) and mTOR signaling pathway related proteins (mTOR, p-mTOR, p-p70S6K) expression decreased in the 2.5 and 5.0 μmol/L group (P<0.05). Compared with the 0 μmol/L group, the staining of the 2.5 and 5.0 μmol/L groups became lighter, and the formation of ALP and mineralized nodules was reduced. Compared with the CdCl2 group, the autophagy related protein expression in the CdCl2+MHY 1485 combined treatment group decreased, and the mTOR signaling pathway related protein expression increased. The difference was statistically significant (P<0.05). Conclusion: The inhibition of osteogenic differentiation of hBMSCs by cadmium may be related to autophagy mediated by mTOR signaling pathway.