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

Genki Kato,Yasutaka Sugamori,Setsuko Mise-Omata,Noriyuki Wakabayashi,Takashi Ono,Natsuki Suzuki,Miki Maeda,Yuki Arai,Yukihiko Tamura,Ramachandran Murali,Kazuhiro Aoki,Yasuhiro Shimizu,Mariko Takahashi,Keiichi Ohya

doi:10.1186/s13075-015-0753-8

Abstract

IntroductionWe 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.MethodsTwenty-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.ResultsThe 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.ConclusionThe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0753-8) contains supplementary material, which is available to authorized users.

Highlights

We designed OP3-4 (YCEIEFCYLIR), a cyclic peptide, to mimic the soluble osteoprotegerin (OPG), and was proven to bind to RANKL, thereby inhibiting osteoclastogenesis
Bone marrow cells from tibiae and femurs were cultured in the presence of soluble RANKL and macrophage colony-stimulating factor (M-CSF) for 4 days, and the Tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells were counted
We have demonstrated that the RANKL-binding peptide OP3-4 increased bone formation at periarticular sites, and decreased bone resorption, preventing bone loss due to collagen-induced arthritis (CIA)

Summary

Introduction

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. Leading to a reduction of the bone quality, followed by atypical fractures [9,10,11] In this context, a clinical trial using parathyroid hormone (PTH), a stimulator of bone formation and a bone resorption inhibitor [12], has been initiated to determine whether such treatment can reduce the fracture risk. The WP9QY peptide (W9), a different RANKL binding peptide derived based on the structures of tumor necrosis factor type 1 receptor/ receptor activator of nuclear factor-κB (RANK) receptors [15, 16], was demonstrated to promote bone formation, as well as to inhibit bone resorption [17]. We hypothesized that the RANKLbinding peptide OP3-4 would stimulate bone formation, as well as inhibit bone resorption

Methods

Results

Discussion

Conclusion