Selective inhibition of RANK blocks osteoclast maturation and function and prevents bone loss in mice
Hyunsoo Kim, … , Yongwon Choi, Soo Young Lee
Hyunsoo Kim, … , Yongwon Choi, Soo Young Lee
Published March 2, 2009
Citation Information: J Clin Invest. 2009;119(4):813-825. https://doi.org/10.1172/JCI36809.
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Research Article Bone biology

Selective inhibition of RANK blocks osteoclast maturation and function and prevents bone loss in mice

Abstract

Regulation of the formation and function of bone-resorbing osteoclasts (OCs) is a key to understanding the pathogenesis of skeletal disorders. Gene-targeting studies have shown that the RANK signaling pathway plays a critical role in OC differentiation and function. Although pharmaceutical blockade of RANK may be a viable strategy for preventing bone destruction, RANK is implicated in multiple biological processes. Recently, a cytoplasmic motif of RANK was identified that may be specifically involved in OC differentiation. Here, we developed a cell-permeable inhibitor termed the RANK receptor inhibitor (RRI), which targets this motif. The RRI peptide blocked RANKL-induced OC formation from murine bone marrow–derived macrophages. Furthermore, RRI inhibited the resorptive function of OCs and induced OC apoptosis. Treatment with the peptide impaired downstream signaling of RANK linked to Vav3, Rac1, and Cdc42 and resulted in disruptions of the actin cytoskeleton in differentiated OCs. In addition, RRI blocked inflammation-induced bone destruction and protected against ovariectomy-induced bone loss in mice. These data may be useful in the development of selective therapeutic agents for the treatment of osteoporosis and other bone diseases.

Authors

Hyunsoo Kim, Han Kyoung Choi, Ji Hye Shin, Kyung Hee Kim, Ji Young Huh, Seung Ah Lee, Chang-Yong Ko, Han-Sung Kim, Hong-In Shin, Hwa Jeong Lee, Daewon Jeong, Nacksung Kim, Yongwon Choi, Soo Young Lee

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Figure 3

The RRI peptide inhibits OC formation at the terminal differentiation stage.

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The RRI peptide inhibits OC formation at the terminal differentiation st...
(A) BMMs were cultured for 4 days in M-CSF and RANKL and stained for TRAP activity. Duration of exposure to the peptides in days (left panel) and TRAP-stained OCs (bottom panel). Number of TRAP+ MNCs (right panel). Data are representative of at least 3 experiments. (B) Effect of the peptide on pre-OCs fusion. Pre-OCs isolated by coculture of BM cells with OBs for 6 days. Purified pre-OCs were induced to fuse for 24 hours under M-CSF and RANKL treatment in the presence of either WT or Mt peptides. Cells were stained for TRAP (left panel). Number of counted TRAP+ MNCs (right panel). (C) Determination of the minimal inhibitory sequences of RANK. Sequences of the RANK inhibitors (WT-1 to WT-5) and control peptides (Mt-1 to Mt-5) (left panel). TRAP-stained OCs (right panel) incubated with each inhibitor (5 μM) and control peptide (5 μM) conjugated with Hph-1 protein transduction domain. Number of TRAP+ MNCs (bottom panel). All data represent mean ± SD. *P < 0.001. Scale bars: 200 μm.