title: The inhibitory effects of a RANKL-binding peptide on articular and periarticular bone loss in a murine model of collagen-induced arthritis: a bone histomorphometric study.
abstract: BACKGROUND
  We designed OP3-4 (YCEIEFCYLIR), a cyclic peptide, to mimic the soluble osteoprotegerin (OPG), and was proven to bind to RANKL (receptor activator of NF-κB ligand), thereby inhibiting osteoclastogenesis. We recently found that another RANKL binding peptide, W9, could accelerate bone formation by affecting RANKL signaling in osteoblasts. We herein demonstrate the effects of OP3-4 on bone formation and bone loss in a murine model of rheumatoid arthritis.
  
  
  METHODS
  Twenty-four seven-week-old male DBA/1J mice were used to generate a murine model of collagen-induced arthritis (CIA). Then, vehicle or OP3-4 (9 mg/kg/day or 18 mg/kg/day) was subcutaneously infused using infusion pumps for three weeks beginning seven days after the second immunization. The arthritis score was assessed, and the mice were sacrificed on day 49. Thereafter, radiographic, histological and biochemical analyses were performed.
  
  
  RESULTS
  The OP3-4 treatment did not significantly inhibit the CIA-induced arthritis, but limited bone loss. Micro-CT images and quantitative measurements of the bone mineral density revealed that 18 mg/kg/day OP3-4 prevented the CIA-induced bone loss at both articular and periarticular sites of tibiae. As expected, OP3-4 significantly reduced the CIA-induced serum CTX levels, a marker of bone resorption. Interestingly, the bone histomorphometric analyses using undecalcified sections showed that OP3-4 prevented the CIA-induced reduction of bone formation-related parameters at the periarticular sites.
  
  
  CONCLUSIONS
  The peptide that mimicked OPG prevented inflammatory bone loss by inhibiting bone resorption and stimulating bone formation. It could therefore be a useful template for the development of small molecule drugs for inflammatory bone loss.
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. kat-hpha@tmd.ac.jp.
authors.forename: Genki
authors.initials: G
authors.lastname: Kato
authors.affiliation: Department of Orthodontic Science, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. y.shimizu.orts@tmd.ac.jp.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Department of Removable Partial Prosthodontics, Division of Oral Health Science, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. y.arai.rpro@tmd.ac.jp.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Arai
authors.affiliation: Department of Removable Partial Prosthodontics, Division of Oral Health Science, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. naturpro@tmd.ac.jp.
authors.forename: Natsuki
authors.initials: N
authors.lastname: Suzuki
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. sug-hpha@tmd.ac.jp.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Sugamori
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. m.maeda@uke.de.|Present address: Department of Trauma-, Hand- and Reconstructive Surgery, Experimental Trauma Surgery, Molecular Skeletal Biology Laboratory, University Medical Center Hamburg-Eppendorf, Heisenberg Group, Martinistrasse 52, 20246, Hamburg, Germany. m.maeda@uke.de.
authors.forename: Miki
authors.initials: M
authors.lastname: Maeda
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. takahashi.hpha@tmd.ac.jp.
authors.forename: Mariko
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. tamu.hpha@tmd.ac.jp.
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Tamura
authors.affiliation: Department of Removable Partial Prosthodontics, Division of Oral Health Science, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. wakabayashi.rpro@tmd.ac.jp.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Wakabayashi
authors.affiliation: Department of Biomedical Sciences, Research Division of Immunology, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA. Ramachandran.Murali@csmc.edu.
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Murali
authors.affiliation: Department of Orthodontic Science, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. t.ono.orts@tmd.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ono
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. kohya.hpha@tmd.ac.jp.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ohya
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. mis-hpha@tmd.ac.jp.
authors.forename: Setsuko
authors.initials: S
authors.lastname: Mise-Omata
authors.affiliation: Department of Pharmacology, Division of Bio-Matrix, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8549, Japan. kazu.hpha@tmd.ac.jp.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Aoki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001169:Arthritis, Experimental / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D015519:Bone Density / Q000187:drug effects; D001862:Bone Resorption / Q000378:metabolism / Q000517:prevention & control*; D002358:Cartilage, Articular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D024042:Collagen Type I / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D055104:Infusions, Subcutaneous; D008297:Male; D008811:Mice, Inbred DBA; D009842:Oligopeptides / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects; D053244:Osteoprotegerin / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D010455:Peptides / Q000097:blood; D011485:Protein Binding; D053245:RANK Ligand / Q000378:metabolism*; D013977:Tibia / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D055114:X-Ray Microtomography
chemical_list: D024042:Collagen Type I; C484520:OP3-4 peptide; D009842:Oligopeptides; D053244:Osteoprotegerin; D010455:Peptides; D053245:RANK Ligand; C052929:collagen type I trimeric cross-linked peptide