Preliminary investigation of the vitamin D pathway in periodontal connective tissue cells

Background: The vitamin D pathway, from toll-like receptor activation to human cationic antimicrobial protein (hCAP-18/LL-37) generation, has been identified in monocytes and keratinocytes. This study aimed to investigate the vitamin D pathway in human gingival fibroblasts (hGFs) and human periodontal ligament cells (hPDLCs) and to provide preliminary evidence of its role in periodontal immune defense. Methods: Primary cultures of hGFs and hPDLCs were stimulated with 1,25-dihydroxy vitamin D-3 and 1,25-hydroxy vitamin D-3, with or without Porphyromonas gingivalis lipopolysaccharide. CYP27B1 RNA interference and vitamin D receptor (VDR) antagonism were also used for reverse proof. The mRNA expression of hCAP-18/LL-37, VDR, interleukin (IL)-6, IL-8, and monocyte chemotactic protein-1 were detected using real-time polymerase chain reaction. The LL-37 concentrations were measured using enzyme-linked immunosorbent assay. Results: In hGFs and hPDLCs, 25-hydroxy vitamin D-3 and 1,25-dihydroxy vitamin D-3 induced hCAP-18/LL-37 expression, which was further increased by Porphyromonas gingivalis lipopolysaccharide. If the function of CYP27B1 or VDR was blocked, the induction was significantly weakened. IL-8 and monocyte chemotactic protein-1 mRNA expression could be suppressed by the vitamin D pathway. Conclusion: These findings suggest that the vitamin D pathway exists in hGFs and hPDLCs and plays an important role in immune defense in periodontal soft tissues.