UV photoactivation of 7-dehydrocholesterol on titanium implants enhances osteoblast differentiation and decreases Rankl gene expression

• Published in: Acta biomaterialia 2013-03, Vol.9 (3), p.5759-5770
• Main Authors: Satué, M., Petzold, C., Córdoba, A., Ramis, J.M., Monjo, M.
• Format: Article
• Language: English
• Subjects: 7-Dehydrocholesterol; Alkaline Phosphatase - metabolism; Animals; Calcification, Physiologic - drug effects; Calcification, Physiologic - genetics; calcium; Cell Count; Cell Differentiation - drug effects; Cell Differentiation - genetics; Cell Line; Cell Shape - drug effects; Cell Survival - drug effects; chemical structure; Cholecalciferol - pharmacology; Coated Materials, Biocompatible - pharmacology; coatings; cytotoxicity; Dehydrocholesterols - radiation effects; Fourier transform infrared spectroscopy; gene expression; Gene Expression Regulation - drug effects; Gene Expression Regulation - radiation effects; high performance liquid chromatography; Mice; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - metabolism; Osteoblast differentiation; osteoblasts; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoblasts - enzymology; Osteoblasts - radiation effects; Prostheses and Implants; RANK Ligand - genetics; RANK Ligand - metabolism; Spectroscopy, Fourier Transform Infrared; Time Factors; titanium; Titanium - pharmacology; Titanium implant; ultraviolet radiation; Ultraviolet Rays; UV irradiation; Vitamin D
• ISSN: 1742-7061; 1878-7568
• DOI: 10.1016/j.actbio.2012.11.021

Vitamin D plays a central role in bone regeneration, and its insufficiency has been reported to have profound negative effects on implant osseointegration. The present study aimed to test the in vitro biological effect of titanium (Ti) implants coated with UV-activated 7-dehydrocholesterol (7-DHC), the precursor of vitamin D, on cytotoxicity and osteoblast differentiation. Fourier transform infrared spectroscopy confirmed the changes in chemical structure of 7-DHC after UV exposure. High-pressure liquid chromatography analysis determined a 16.5±0.9% conversion of 7-DHC to previtamin D3 after 15min of UV exposure, and a 34.2±4.8% of the preD3 produced was finally converted to 25-hydroxyvitamin D3 (25-D3) by the osteoblastic cells. No cytotoxic effect was found for Ti implants treated with 7-DHC and UV-irradiated. Moreover, Ti implants treated with 7-DHC and UV-irradiated for 15min showed increased 25-D3 production, together with increased ALP activity and calcium content. Interestingly, Rankl gene expression was significantly reduced in osteoblasts cultured on 7-DHC-coated Ti surfaces when UV-irradiated for 15 and 30min to 33.56±15.28% and 28.21±4.40%, respectively, compared with the control. In conclusion, these findings demonstrate that UV-activated 7-DHC is a biocompatible coating of Ti implants, which allows the osteoblastic cells to produce themselves active vitamin D, with demonstrated positive effects on osteoblast differentiation in vitro.