title: UV-irradiated 7-dehydrocholesterol coating on polystyrene surfaces is converted to active vitamin D by osteoblastic MC3T3-E1 cells.
abstract: The aim of the present study was to determine the effects of UV irradiation on the conversion of 7-dehydrocholesterol (7-DHC), which has been coated onto a polystyrene surface, to cholecalciferol (D3), and the resulting effect on the formation of vitamin D (1,25-D3) by MC3T3-E1 cells. The changes in gene expression of the enzymes regulating its hydroxylation, Cyp27b1 and Cyp27a1, were monitored as well as the net effect of the UV-treated 7-DHC coating on cell viability and osteoblast differentiation. MC3T3-E1 cells were found to express the enzymes required for synthesizing active 1,25-D3, and we found a dose-dependent increase in the production of both 25-D3 and 1,25-D3 levels for UV-activated 7-DHC samples unlike UV-untreated ones. Cell viability revealed no cytotoxic effect for any of the treatments, but only for the highest dose of 7-DHC (20 nmol per well) that was UV-irradiated. Furthermore, osteoblast differentiation was increased in cells treated with some of the higher doses of 7-DHC when UV-irradiated, as shown by collagen-I, osterix and osteocalcin relative mRNA levels. The conversion of 7-DHC to preD3 exogenously by UV irradiation and later to 25-D3 by MC3T3-E1 cells was determined for the optimum 7-DHC dose (0.2 nmol per well), i.e. 8.6 ± 0.7% of UV-activated 7-DHC was converted to preD3 and 6.7 ± 2.8% of preD3 was finally converted to 25-D3 under the conditions studied. In conclusion, we demonstrate that an exogenous coating of 7-DHC, when UV-irradiated, can be used to endogenously produce active vitamin D. We hereby provide the scientific basis for UV-activated 7-DHC coating as a feasible approach for implant therapeutics focused on bone regeneration.
authors.affiliation: Department of Fundamental Biology and Health Sciences, Research Institute on Health Sciences (IUNICS), University of Balearic Islands, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Satué
authors.forename: Alba
authors.initials: A
authors.lastname: Córdoba
authors.forename: Joana M
authors.initials: JM
authors.lastname: Ramis
authors.forename: Marta
authors.initials: M
authors.lastname: Monjo
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002454:Cell Differentiation; D002470:Cell Survival; D002762:Cholecalciferol / Q000378:metabolism*; D020099:Coated Materials, Biocompatible / Q000737:chemistry / Q000378:metabolism*; D003684:Dehydrocholesterols / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D011137:Polystyrenes / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D020099:Coated Materials, Biocompatible; D003684:Dehydrocholesterols; D011137:Polystyrenes; D002762:Cholecalciferol; C016705:7-dehydrocholesterol