Calcitriol exerts a mineralization-inductive effect comparable to that of vitamin C in cultured human periodontium cells

Abstract

This study inspected whether calcitriol could exert a mineralization-inductive effect comparable to that of vitamin C in cultured human periodontium cells (hPDCs). The mRNA expression of the mineralization-related biomarkers core-binding factor subunit alpha-1 (Cbfal), collagen 1 alpha l (Col-l), alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP), osteocalcin (OCN), vitamin D receptor (VDR), cementum protein 1 (CEMP-1), cementum attachment protein (CAP), interleukin 6 (IL-6), transforming growth factor-beta 1 (TGF-beta 1) and osteoprotegerin (OPG) was surveyed after incubation of hPDCs with vitamin C and calcitriol for 2 weeks. Translational expression information from ALP activity and CEMP-1 and CAP immunofluorescence assays was acquired from hPDCs at the second and third weeks. Extracellular calcifications were confirmed by von Kossa staining, Alizarin Red staining and synchrotron transmission X-ray microscopy (TXM) at the fourth and fifth weeks. It was found that both vitamin C and calcitriol not only increased mineralization-related mRNA fold-changes but also enhanced ALP activity, CEMP1 immunofluorescence, von Kossa and Alizarin Red staining and TXM-associated calcifications. Generally, 10(-8) M calcitriol displayed greater mineralization significance than 10(-7) M calcitriol in the assays tested. However, vitamin C stimulated lower Cbfal, Col-1, ALP, OPN, BSP, OCN, VDR, CEMP-1 and IL-6 mRNA fold-changes than 10(-8) M calcitriol. Finally, TXM analysis indicated that a 10(-8) M calcitriol treatment stimulated greater calcifications than vitamin C treatment. Therefore, the analytical results confirmed the osteo-inductive potential of vitamin C in cultured hPDCs. In contrast, 10(-8) M calcitriol could potentially function as a substitute because it stimulates a greater mineralization effect than vitamin C or 10(-7) M calcitriol.