[Effect of hypoxia on the expression of HIF-1alpha and VEGF in human periodontal ligament cells in vitro].

Purpose: To investigate the effect of hypoxia on the expression of HIF-1alpha and VEGF in human periodontal ligament cells (hPDLCs) in vitro.

Methods: HPDLCs were cultured in Dulbecco's modified Eagle's medium (DMEM) and subcultured at confluence. Experiments were carried out with the third passage of hPDLCs populations. In the normoxic control group, cells were incubated under normoxic conditions of 20% O2, 5% CO2, 75% N2 for 24 hours and 48 hours, respectively. In the hypoxic group, cells were incubated in a humidified atmosphere of 1% O2, 5% CO2, 94% N2 for 24 hours and 48 hours, respectively. The expression of HIF-1alpha and VEGF in hPDLCs in vitro was measured using reverse transcription-polymerase chain reaction. SP immunohistochemistry method was performed to localize the distribution of HIF-1alpha and VEGF in hPDLCs. The data was analyzed by Student's t test, one-way ANOVA and LSD test with SPSS 13.0 software package.

Results: There was no significant difference between the hypoxic group and the normoxic control group in the expression of HIF-1alpha mRNA in hPDLCs. The expression of VEGF mRNA in the hypoxic group of 24 hours and 48 hours was both statistically higher than in the control group (P<0.05). The expression of HIF-1alpha protein was significantly increased with hypoxia time while the staining of HIF-1alpha was negative under normoxic condition. The expression of VEGF protein in hypoxic groups was significantly higher than in normoxic control groups. The staining of VEGF gradually enhanced in a time-dependent manner and was weakly positive after 48 hours under normoxic condition.

Conclusion: Hypoxia could change the metabolic pathway of human periodontal ligament cells by upregulating the expression of HIF-1alpha and other relevant growth factors.