1,25(OH)2D3 supports the osteogenic differentiation of hPDLSCs under inflammatory conditions through inhibiting PLAP-1 expression transcriptionally

Periodontal ligament-associated protein-1 (PLAP-1) is a newly identified negative regulator which is the mineralization of human periodontal ligament stem cells (hPDLSCs). The aim of the present study is to determine whether 1α, 25-dihydroxyvitamin D3 (1,25(OH)2D3) could enhances the osteoblastic differentiation of hPDLSCs under inflammatory condition, and if PLAP-1 is involved in this process. hPDLSCs were in combination or alone cultured with lipopolysaccharide (LPS) and 1,25(OH)2D3, in osteo-inductive medium. The expression levels of osteoblastic markers and PLAP-1 of hPDLCs during osteo-inductive culture were assessed by western blot and real-time quantitative PCR(qRT-PCR). The potential vitamin D receptor elements (VDREs) which were located in PLAP-1 promoter region were identified and confirmed. The data showed that LPS inhibited osteoblastic differentiation and induced the expression of PLAP-1 in hPDLSCs. The increasing addition of 1,25(OH)2D3 reversed the LPS-induced inhibition of osteoblastic differentiation of hPDLSCs through the suppression of PLAP-1 expression. Moreover, a potential VDRE within the PLAP-1 promoter region was identified and shown to bind with VDR by chromatin immunoprecipitation (ChIP) assays. This negative region was also found to mediate suppressor reporter gene activity. 1,25(OH)2D3 could enhances the osteogenic differentiation of hPDLSCs under inflammatory condition through inhibiting PLAP-1 expression transcriptionally.