TGF-β1 induces apoptosis of bone marrow-derived mesenchymal stem cells via regulation of mitochondrial reactive oxygen species production.

Bone marrow-derived mesenchymal stem cells (BMSCs) are the most promising seed cells in regenerative medicine. Our previous study demonstrated that transforming growth factor (TGF)-β1 induced BMSC senescence in vitro. Whether TGF-β1 affects the apoptosis of BMSCs has not been examined; therefore the aim of the present study was to investigate this effect. BMSCs were isolated from mouse bone marrow, and the third-passage cells were exposed to 0, 10 and 20 ng/ml TGF-β1 for 24 h. Cell proliferation was measured by MTT assay; apoptosis was assessed using DAPI staining; and the apoptotic signals Annexin V, B-cell lymphoma (Bcl)-2 and Bcl-2-associated X protein (Bax) were measured using western blotting. Mitochondrial reactive oxygen species (ROS) were measured by flow cytometry following staining with MitoSOX™ Red mitochondrial superoxide indicator. The MTT assay showed that 10 and 20 ng/ml TGF-β1 inhibited BMSC proliferation. DAPI staining demonstrated that 10 and 20 ng/ml TGF-β1 promoted BMSC apoptosis, which was further confirmed by a western blotting assay showing a significant increase in the pro-apoptotic signals Annexin V and Bax but a decrease in the anti-apoptotic signal Bcl-2. It was also found that TGF-β1 markedly increased the mitochondrial ROS levels in BMSCs. It is well known that mitochondrial ROS are strong stimulators of cell apoptosis. These findings indicate that TGF-β1 can induce BMSC apoptosis, and the mechanism may involve mitochondrial ROS generation.