1, 25-dihydroxyvitamin D₃ Increases VDR and RANKL Expression in hPDLCs

Objective: The present study aimed to investigate the effects of 1, 25-dihydroxyvitamin D₃ (VD₃) on the regulation of vitamin D receptor (VDR), receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) in human periodontal ligament cells (hPDLCs) populations. Methods: 12 primary hPDLCs populations were established from 12 donors individually. Two samples of each hPDLCs population of passage three were treated respectively with 10^-8 mol/L VD₃ (V group) or 0.1% absolute ethyl alcohol as controls (C group). 6 days later, the mRNA expression levels of VDR, RANKL and OPG in the samples were determined with real-time RT-PCR to analyze the difference between V and C groups. Results: 11 out of 12 hPDLCs populations showed increased VDR mRNA expression in the V group, averagely 3.12 times of that in the C group (p=0.003). The mRNA expression of RANKL was also up-regulated by VD₃ in 11 out of 12 hPDLCs populations to averagely 9.82 times of that in the C group (p=0.003) while with a wide range of fold change, from 74.65% to 119.18 times of the controls. In addition, VD₃ decreased the mRNA expression of OPG in 8 out of 12 hPDLCs populations, averagely to 90.35% of the controls (p=0.410). OPG/RANKL ratio was down-regulated in 11 out of 12 in the V group to averagely 10.36% of the controls (p=0.003). Conclusions: VD₃ significantly increases the expression of VDR and RANKL while decreases OPG/RANKL ratio in hPDLCs, which may help promote osteoclastogenesis. Different regulation of target genes among various cell populations, especially RANKL, suggest individual diversity in respond to VD₃ stimulation.