To investigate the effects of hypoxia on osteogenic differentiation of periodontal ligament cells (PDLCs) and the role of hypoxia inducible factor-1α (HIF-1α) in this process.

Human PDLCs were isolated and identified by checking the expression of vimentin and cytokeratin. PDLCs were cultured in normoxia (20% O₂) or hypoxia (1% O₂) for 12-72 h. Changes of alkaline phosphatase (ALP) activity and mRNA expressions of osteogenic markers ALP, collagen-Ⅰ (COL1) and runt related transcription factor 2 (RUNX2) were detected. Western blot was used to detect the expression of HIF-1α. After transfected with HIF1α-siRNA, the expressions of HIF-1αand osteogenic dif-ferentiation markers were furthered detected. The statistics were analyzed with SPSS13.0.

Positive vimentin but negative cytokeratin were observed in primary cultured PDLCs. ALP activity and mRNA expressions of ALP, COL1 and RUNX2 were decreased in PDLCs in hypoxia for 48 h, while HIF-1α expression was increased. After knocking down of HIF-1α with siRNA, HIF-1α was significantly reduced in PDLCs under hypoxia, while ALP activity and mRNA expressions of osteogenic markers were significantly increased.

Hypoxia may inhibit osteogenic differentiation of PDLCs via upregulated HIF-1α.