Effect of heat stress on the expression levels of receptor activator of NF-κB ligand and osteoprotegerin in human periodontal ligament cells.

AIM

To investigate the expression levels of the receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) in human periodontal ligament fibroblasts (PDLs) when stimulated with heat.

METHODOLOGY

Periodontal ligament fibroblasts were subjected to various temperature increases for 5 min and then maintained at 37 °C. After that, cell viability was determined using an MTT assay. The expression levels of RANKL and OPG were investigated using real-time RT-PCR and ELISA. As a control, the cells were cultured at 37 °C. Data were analysed using one-way anova at a significant level of P = 0.05. Results  Cell viability was reduced significantly in the heated groups (P < 0.05). Heat stress downregulated the mRNA expression levels of RANKL and OPG (P < 0.05). When the cells were heated at 39 °C, the protein release of OPG was increased (P < 0.05). There were no significant differences between the heated groups and the control in the release of soluble RANKL (P > 0.05). The relative RANKL/OPG expression ratios were decreased at 39, 43 and 50 °C (P < 0.05), but increased at 47 °C (P < 0.05).

CONCLUSIONS

Heat influenced the balance between RANKL and OPG in PDLs. Low heat downregulated their relative ratio, whilst high heat upregulated it.