Alfacalcidol enhances collagen quality in ovariectomized rat bones

The aim of this study was to investigate the effects of alfacalcidol (1α(OH)D₃: ALF) on bone collagen employing an ovariectomized rat model. Thirty-five 16-week-old female Sprague-Dawley rats were divided into five groups: SHAM (sham-operated-+-vehicle), OVX (ovariectomy-+-vehicle), and three ALF-treated groups, that is, ovariectomy-+-0.022-μg/kg/day ALF, ovariectomy-+-0.067-μg/kg/day ALF, and ovariectomy-+-0.2-μg/kg/day ALF. After 12 weeks of treatment, tibiae were subjected to histological, biochemical and immunohistochemical analyses. Collagen matrices in OVX bone appeared as immature and poorly organized; however, with the ALF treatment, it was improved in a dose-dependent manner. Contents of collagen and pyridinoline cross-link were decreased in OVX compared with SHAM, but they increased to the level comparable to SHAM in ALF-treated groups. The total aldehyde, that is, a sum of free and those involved cross-links, in the highest dose of ALF was significantly higher than the rest of the groups (p-<-0.05). In addition, the expression of lysyl oxidase was increased in the all ALF-treated groups compared with OVX (p-<-0.05). In conclusion, ALF increases not only the amount of collagen but also enhances the maturation of collagen in ovariectomy-induced osteoporotic bones, which likely contributes to the improvement of bone quality.