title: Treatment with eldecalcitol positively affects mineralization, microdamage, and collagen crosslinks in primate bone.
abstract: 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 treatment with ELD for 6 months 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 electron microscopic 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 samples were 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 (<2.0 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 crosslinks were lower in both the high- and low-density fractions. These observations indicated that ELD treatment stimulated the enzymatic reaction of collagen crosslinks and bone mineralization, 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, bone microdamage, 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.
authors.affiliation: Jikei University School of Medicine, Orthopedic Surgery Department, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan. Electronic address: xlink67@gol.com.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Saito
authors.affiliation: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
authors.forename: Marc D
authors.initials: MD
authors.lastname: Grynpas
authors.affiliation: Department of Anatomy and Cell Biology, Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Burr
authors.affiliation: Department of Anatomy and Cell Biology, Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Allen
authors.affiliation: Musculoskeletal Research, Charles River Laboratories Preclinical Services Montreal, Senneville, Quebec, Canada.
authors.forename: Susan Y
authors.initials: SY
authors.lastname: Smith
authors.affiliation: Musculoskeletal Research, Charles River Laboratories Preclinical Services Montreal, Senneville, Quebec, Canada.
authors.forename: Nancy
authors.initials: N
authors.lastname: Doyle
authors.affiliation: Division of Oral Health Science, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Amizuka
authors.affiliation: Division of Oral Health Science, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Tomoka
authors.initials: T
authors.lastname: Hasegawa
authors.affiliation: Jikei University School of Medicine, Orthopedic Surgery Department, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Yoshikuni
authors.initials: Y
authors.lastname: Kida
authors.affiliation: Jikei University School of Medicine, Orthopedic Surgery Department, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Keishi
authors.initials: K
authors.lastname: Marumo
authors.affiliation: Medical Science Department, Chugai Pharmaceutical Co., Ltd., Tokyo, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Saito
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002113:Calcification, Physiologic / Q000187:drug effects*; D003094:Collagen / Q000378:metabolism*; D005260:Female; D008252:Macaca fascicularis; D008854:Microscopy, Electron; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D014807:Vitamin D; D003094:Collagen; C547512:eldecalcitol
keywords: Bone microarchitecture; Bone microdamage; Bone mineralization; Bone quality; Collagen crosslinks; Vitamin D