Effects of hypoxia‑inducible factor‑1α on the proliferation and apoptosis of human synovial mesenchymal stem cells.

Hypoxia is a constant feature of the synovial microenvironment. How synovial mesenchymal stem cells (SMSCs) proliferate and differentiate in a hypoxic environment over a long period of time has aroused the interest of researchers. The aim of the present study was to explore the effects of hypoxia-inducible factor-1 alpha (HIF-1 alpha) on the proliferation and apoptosis of human SMSCs. SMSCs were harvested and cultured under different concentration of oxygen, normoxia (21% O-2), hypoxia (5% O-2) and severe hypoxia (0.5% O-2) to determine its effect on the expression of HIF-1 alpha. Then, the cells were collected and cell proliferation and apoptosis were detected at severe hypoxia (0.5% O-2) and hypoxia (5% O-2) conditions following HIF-1 alpha siRNA transfection. There were no significant changes in cellular proliferation or apoptosis when cultured in normoxia (21% O-2), hypoxia (5% O-2) or severe hypoxia (0.5% O-2). However, the mRNA and protein expression of HIF-1 alpha were markedly upregulated in the hypoxic conditions. Further experiments suggested that the proliferation of SMSCs was obviously suppressed and apoptosis was markedly increased under severe hypoxic (0.5%) and hypoxic (5% O-2) conditions following HIF-1 alpha siRNA transfection. In conclusion, HIF-1 alpha effectively improved the tolerance of SMSCs to hypoxia, which may promote cellular proliferation and prevent the apoptosis of SMSCs under hypoxic conditions.