RANKL-independent osteoclastogenesis in the SH3BP2 cherubism mice

Mizuho Kittaka; Tetsuya Yoshimoto; Henry Hoffman; Marcus Evan Levitan; Yasuyoshi Ueki

doi:10.1016/j.bonr.2020.100258

RANKL-independent osteoclastogenesis in the SH3BP2 cherubism mice

Bone Rep. 2020 Mar 27:12:100258. doi: 10.1016/j.bonr.2020.100258. eCollection 2020 Jun.

Authors

Mizuho Kittaka^{1

2}, Tetsuya Yoshimoto^{1

2}, Henry Hoffman³, Marcus Evan Levitan^{1

2}, Yasuyoshi Ueki^{1

2}

Affiliations

¹ Department of Biomedical Sciences and Comprehensive Care, Indiana University, School of Dentistry, Indianapolis, IN 46202, USA.
² Indiana Center for Musculoskeletal Health, Indiana University, School of Medicine, Indianapolis, IN 46202, USA.
³ Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City, School of Dentistry, Kansas City, MO 64108, USA.

Abstract

Even though the receptor activator of the nuclear factor-κB ligand (RANKL) and its receptor RANK have an exclusive role in osteoclastogenesis, the possibility of RANKL/RANK-independent osteoclastogenesis has been the subject of a long-standing debate in bone biology. In contrast, it has been reported that calvarial injection of TNF-ɑ elicits significant osteoclastogenesis in the absence of RANKL/RANK in NF-κB2- and RBP-J-deficient mice, suggesting that inflammatory challenges and secondary gene manipulation are the prerequisites for RANKL/RANK-deficient mice to develop osteoclasts in vivo. Here we report that, even in the absence of RANKL (Rankl ^-/- ), cherubism mice (Sh3bp2 ^KI/KI ) harboring the homozygous gain-of-function mutation in SH3-domain binding protein 2 (SH3BP2) develop tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclasts spontaneously. The Sh3bp2 ^KI/KI Rankl ^-/- mice exhibit an increase in tooth exposure and a decrease in bone volume/total volume compared to Sh3bp2 ^+/+ Rankl ^-/- mice. The multinucleated cells were stained positively for cathepsin K. Osteoclastic marker gene expression in bone and serum TRAP5b levels were elevated in Sh3bp2 ^KI/KI Rankl ^-/- mice. Elevation of the serum TNF-ɑ levels suggested that TNF-ɑ is a driver for the RANKL-independent osteoclast formation in Sh3bp2 ^KI/KI mice. Our results provide a novel mutant model that develops osteoclasts independent of RANKL and establish that the gain-of-function of SH3BP2 promotes osteoclastogenesis not only in the presence of RANKL but also in the absence of RANKL.

Keywords: Cherubism; RANKL; RANKL-independent osteoclastogenesis; SH3BP2; TNF-ɑ.

Abstract

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