open access

https://hdl.handle.net/2115/72268

Treatment with eldecalcitol positively affects mineralization, microdamage, and collagen crosslinks in primate bone

英語

Collagen crosslinks

2015-04

Elsevier

Bone

73

8-15

Eldecalcitol (ELD), an active form of vitamin D analog approved for the treatment of osteoporosis in Japan, increases lumbar spine bone mineral density (BMD), suppresses bone turnover markers, and reduces fracture risk in patients with osteoporosis.We have previously reported that treatmentwith ELD for 6months improved the mechanical properties of the lumbar spine in ovariectomized (OVX) cynomolgus monkeys. ELD treatment increased lumbar BMD, suppressed bone turnover markers, and reduced histomorphometric parameters of both bone formation and resorption in vertebral trabecular bone. In this study, we elucidated the effects of ELD on bone quality (namely, mineralization, microarchitecture, microdamage, and bone collagen crosslinks) in OVX cynomolgus monkeys in comparison with OVX-vehicle control monkeys. Density fractionation of bone powder prepared from lumbar vertebrae revealed that ELD treatment shifted the distribution profile of bone mineralization to a higher density, and backscattered electronmicroscopic imaging showed improved trabecular bone connectivity in the ELD-treated groups. Higher doses of ELD more significantly reduced the amount of microdamage compared to OVX-vehicle controls. The fractionated bone powder sampleswere divided according to their density, and analyzed for collagen crosslinks. Enzymatic crosslinks were higher in both the high-density (?2.0 mg/mL) and low-density (b2.0 mg/mL) fractions from the ELD-treated groups than in the corresponding fractions in the OVX-vehicle control groups. On the other hand, non-enzymatic crosslinkswere lower in both the high- and low-density fractions. These observations indicated that ELD treatment stimulated the enzymatic reaction of collagen crosslinks and bonemineralization, but prevented non-enzymatic reaction of collagen crosslinks and accumulation of bone microdamage. Bone anti-resorptive agents such as bisphosphonates slow down bone remodeling so that bone mineralization, bonemicrodamage, and non-enzymatic collagen crosslinks all increase. Bone anabolic agents such as parathyroid hormone decrease bone mineralization and bone microdamage by stimulating bone remodeling. ELD did not fit into either category. Histological analysis indicated that the ELD treatment strongly suppressed bone resorption by reducing the number of osteoclasts, while also stimulating focal bone formation without prior bone resorption (bone minimodeling). These bidirectional activities of ELD may account for its unique effects on bone quality.

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8756-3282