To investigate the impact of
hypoxia on the expression of receptor activator of
NF-kB ligand (RANKL) and
osteoprotegerin (OPG) in human periodontal ligament cells (hPDLCs) in vitro. hPDLCs were incubated in a hypoxic atmosphere of 2% O2, 5% CO2, 94% N2 at 37°C for 6, 12, 24 and 48 h. After that, cell proliferation assay was determined using
CCK-8 technique. SP immunocytochemistry method was performed to trace the expression of
hypoxia-inducible factor 1 alpha (HIF-1α) in hPDLCs. The expression levels of RANKL and OPG were investigated using real-time PCR and ELISA. As a control, the cells were incubated at normoxic conditions of 20% O2, 5% CO2, 75% N2. All results were analyzed using one-way ANOVA at a significant level of P=0.05. OPG
mRNA and
protein levels were down-regulated meanwhile RANKL
mRNA and soluble RANKL (sRANKL)
protein levels were up-regulated after stimulated by
hypoxia. The relative RANKL/OPG expression ratios were increased in both
mRNA and
protein levels. The expression of RANKL
mRNA and sRANKL
protein levels was enhanced significantly (P<0.05) under the
hypoxia conditions at 12 h, 24 h and 48 h while OPG
mRNA and
protein were reduced significantly (P<0.05) at 12 h, 24 h and 48 h.
Hypoxia can affect the expression of RANKL and OPG in hPDLCs, which constitute an important pathogenic event in the alveolar
bone resorption. Lack of
oxygen in periodontal tissue may accelerate the development of
periodontitis.