Loss of Wdfy3 Leads to Enhanced Osteoclastogenesis Via NF-κB Activation

Dennis J. Wu^1,2, Ran Gu², Ritu Sarin², Regina Zavodovskaya³, Chia-Pei Chen⁴, Konstantinos Zarbalis^5,6 and Iannis E. Adamopoulos^1,2,6, ¹Graduate Group in Immunology, University of California, Davis, Davis, CA, ²Division of Rheumatology, Allergy and Clinical Immunology, University of California, Davis, Davis, CA, ³Department of Anatomy, Physiology and Cell Biology, University of California, Davis, Davis, CA, ⁴Department of Statistics, University of California, Davis, Davis, CA, ⁵Department of Pathology and Laboratory Medicine, University of California, Davis, Sacramento, CA, ⁶Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Northern California, Sacramento, CA

Meeting: 2015 ACR/ARHP Annual Meeting

Date of first publication: September 29, 2015

Keywords: osteoclastogenesis and osteoclasts

Session Information

Date: Tuesday, November 10, 2015

Title: Biology and Pathology of Bone and Joint: Bone Remodeling and Metabolism

Session Type: ACR Poster Session C

Session Time: 9:00AM-11:00AM

Background/Purpose: Autophagy and phagocytosis are conserved cellular functions involved in the protein degradation process in immunity. Recently, autophagy-related proteins were shown to regulate osteoclast mediated bone resorption, a critical process in autoimmune diseases such as rheumatoid arthritis. Wdfy3 is a master regulator in selective autophagy for clearing ubiquitinated protein aggregates. In this study, we generated a series Wdfy3 transgenic mice (Wdfy3^lacZ, and Wdfy3^loxP) to investigate the function of Wdfy3 in osteoclast development and function.

Methods: Wdfy3 expression in Wdfy3^lacZ neonatal mice was analyzed by histology and X-gal staining. Bone marrow-derived macrophages from wild type, Wdfy3^lacZ, and Wdfy3 conditional knockout (Wdfy3-cKO) mice (Wdfy3 ^loxP/loxP-LysM-Cre⁺) were differentiated into osteoclasts with macrophage colony-stimulating factor (M-CSF), and receptor activator of NF-κB ligand (RANKL). Wdfy3 expression on osteoclast-like cells was analyzed by X-gal staining and immunohistochemistry. RANKL-induced NF-κB signaling was analyzed by Western blot. Osteoclast-related genes Ctsk, Acp5, Mmp9 were measured by qPCR. Osteoclasts were characterized by tartrate-resistant acid phosphatase staining and filamentous actin ring formation assay. Osteoclast function was evaluated by dentin resorption assay.

Results: Our data showed that Wdfy3 is up regulated in osteoclasts in in vitro cultures and highly expressed at the growth plate of neonatal mice. Osteoclasts derived from Wdfy3-cKO, showed increased osteoclast differentiation and function as evidenced by higher number and enlarged size of TRAP⁺ multinucleated cells. Western blot analysis also revealed up-regulation of TRAF6, enhanced degradation of p-IκBα and increased p-NF-κB p65 in Wdfy3-deficient osteoclasts stimulated with RANKL compared to the control cells. Consistent with these observations Wdfy3 conditional knockout mice also showed an increase in osteoclast-related genes Ctsk, Acp5, Mmp9 and an increase of dentine resorption in in vitro assays. Importantly, no difference was observed in autophagic flux in Wdfy3 deficient bone marrow-derived macrophages and control cells at basal level or under starvation.

Conclusion: Taken together, our data highlight a novel role for Wdfy3 osteoclast development and function, which can be exploited for the treatment of musculoskeletal diseases.

Disclosure: D. J. Wu, None; R. Gu, None; R. Sarin, None; R. Zavodovskaya, None; C. P. Chen, None; K. Zarbalis, None; I. E. Adamopoulos, None.

To cite this abstract in AMA style:

Wu DJ, Gu R, Sarin R, Zavodovskaya R, Chen CP, Zarbalis K, Adamopoulos IE. Loss of Wdfy3 Leads to Enhanced Osteoclastogenesis Via NF-κB Activation [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/loss-of-wdfy3-leads-to-enhanced-osteoclastogenesis-via-nf-b-activation/. Accessed .

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