Inhibitory effect of vitamin K2 on vascular calcification and osteoporosis : experimental approach to understanding the bone-vascular axis

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This study aims to explore the bone-vascular axis based on in vivo/ ex vivo measurements of bone properties and vascular calcification and to evaluate the inhibitory effects of vitamin K2 intake on these metabolic disorders. We established in vivoμCT, which was customized for imaging of mouse hindlimbs, and determined the time course of trabecular architectural changes in the tibia of a mouse model of high-turnover chronic kidney disease(CKD). At the end of the experimental period, structural and material properties of vertebral cortical bone were evaluated byμCT and Fourier transform infrared microspectroscopy, and aortic calcification was examined by von Kossa staining and plasma atomic emission spectrometry. The age-related regression of tibial trabecular network was observed to the higher degree in CKD mice than in control mice. The material properties of vertebral cortical bone did not differ significantly between CKD and control mice, and there was no appearance of aortic calcification in both groups. However, aortic accumulation of P and Ca contents were higher in CKD and inversely correlated with the cortical bone thickness, suggesting the existence of a bone-vascular axis. On the other hand, vitamin K2 supplementation had a beneficial effect on trabecular bone mass and architecture as well as the maturation of cortical bone tissue in growing rat tibiae, showing its potential to enhance bone quality and reducing fracture risk during growth spurts.