title: Elcatonin prevents bone loss caused by skeletal unloading by inhibiting preosteoclast fusion through the unloading-induced high expression of calcitonin receptors in bone marrow cells.
abstract: This study aimed to clarify whether elcatonin (EL) has a preventive action on bone dynamics in skeletal unloading. Seven-week-old male C57BL/6J mice with either ground control (GC) or tail suspension (TS) were administered EL 20U/kg or a vehicle (veh) three times per week and assigned to one of the following four groups: GCEL, GCveh, TSEL, and TSveh. Blood samples and bilateral femurs and tibias of the mice were obtained for analysis. After 7days of unloading, the trabecular bone mineral density in the distal femur obtained via peripheral quantitative computed tomography and the trabecular bone volume were significantly higher in the TSEL group than in the TSveh group. The bone resorption histomorphometric parameters, such as the osteoclast surface and osteoclast number, were significantly suppressed in the TSEL mice, whereas the number of preosteoclasts was significantly increased. The plasma level of tartrate-resistant acid phosphatase-5b (TRACP-5b) was significantly lower in the TSEL group than in all other groups. In the bone marrow cell culture, the number of TRACP-positive (TRACP(+)) multinucleated cells was significantly lower in the TSEL mice than in the TSveh mice, whereas the number of TRACP(+) mononucleated cells was higher in the TSEL mice. On day 4, the expression of nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1), cathepsin K and d2 isoform of vacuolar ATPase V0 domain (ATP6V0D2) mRNA in the bone marrow cells in the TSEL mice was suppressed, and the expression of calcitonin receptor (Calcr) mRNA on day 1 and Calcr antigen on day 4 were significantly higher in the TSveh mice than in the GCveh mice. EL prevented the unloading-induced bone loss associated with the high expression of Calcr in the bone marrow cells of mouse hindlimbs after tail suspension, and it suppressed osteoclast development from preosteoclasts to mature osteoclasts through bone-resorbing activity. This study of EL-treated unloaded mice provides the first in vivo evidence of a physiological role of EL in the inhibition of the differentiation process from preosteoclasts to osteoclasts.
authors: Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. Electronic address: m-tsuka@med.uoeh-u.ac.jp.
authors: Manabu
authors: M
authors: Tsukamoto
authors: Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. Electronic address: menuki@med.uoeh-u.ac.jp.
authors: Kunitaka
authors: K
authors: Menuki
authors: Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. Electronic address: t-murai@med.uoeh-u.ac.jp.
authors: Teppei
authors: T
authors: Murai
authors: Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. Electronic address: hatakeakihisa@gmail.com.
authors: Akihisa
authors: A
authors: Hatakeyama
authors: Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. Electronic address: behaveabandon@yahoo.co.jp.
authors: Shinichiro
authors: S
authors: Takada
authors: Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. Electronic address: kayoko830@gmail.com.
authors: Kayoko
authors: K
authors: Furukawa
authors: Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. Electronic address: a-sakai@med.uoeh-u.ac.jp.
authors: Akinori
authors: A
authors: Sakai
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D015519:Bone Density / Q000187:drug effects; D001854:Bone Marrow Cells / Q000378:metabolism*; D001862:Bone Resorption / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology*; D002116:Calcitonin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D000071556:Cancellous Bone / Q000473:pathology / Q000503:physiopathology; D002459:Cell Fusion; D002478:Cells, Cultured; D005269:Femur / Q000473:pathology / Q000503:physiopathology; D005786:Gene Expression Regulation / Q000187:drug effects; D019417:Hindlimb Suspension; D008297:Male; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018003:Receptors, Calcitonin / Q000378:metabolism*; D000071681:Tartrate-Resistant Acid Phosphatase / Q000378:metabolism
chemical_list: D015415:Biomarkers; D012333:RNA, Messenger; D018003:Receptors, Calcitonin; D002116:Calcitonin; D000071681:Tartrate-Resistant Acid Phosphatase; C012755:elcatonin
keywords: Calcitonin; Calcitonin receptor; Disuse-induced osteoporosis; Osteoclast; Preosteoclast; Tail suspension