USP29 Represses the Osteoclastic Differentiation of Human CD14⁺ Peripheral Blood Mononuclear Cells by Stabilizing MafB

Shaoyu Hu¹, Bingquan Li¹, Jianfeng Ouyang¹, Yue Meng², Jian Ji³, Xiaofei Zheng^4,*, Yongheng Ye^1,*
1 Department of Joint and Sports Medicine, Zhuhai Hospital Affiliated with Jinan University (Zhuhai People’s Hospital), Zhuhai, China
2 Department of Joint Surgery, The Fifth Affiliated Hospital of Southern Medical University, Guangzhou, China
3 Department of Hepatobiliary Breast Surgery, The Fifth Affiliated Hospital of Southern Medical University, Guangzhou, China
4 Department of Sports Medicine, The First Affiliated Hospital, Guangdong Provincial Key Laboratory of Speed Capability, The Guangzhou Key Laboratory of Precision Orthopedics and Regenerative Medicine, Jinan University, Guangzhou, China
* Corresponding Author: Xiaofei Zheng. Email: email ; Yongheng Ye. Email: email

BIOCELL https://doi.org/10.32604/biocell.2026.071651

Received 09 August 2025; Accepted 17 December 2025; Published online 21 January 2026

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Abstract

Objectives: Dysregulated osteoclast function contributes to skeletal diseases. However, the specific ubiquitination regulators of the osteoclastogenesis repressor MafB, particularly at the post-translational level, remain undefined. This study aims to identify ubiquitin-specific proteases (USPs) that deubiquitinate MafB and enhance its stability. Methods: We constructed a MafB-conjugated luciferase and overexpressed 40 individual USPs, measuring changes in luciferase activity. The identified USP was overexpressed in human CD14⁺ peripheral blood mononuclear cells (PBMCs) to evaluate its effect. Osteoclast differentiation was assessed through osteoclast marker Integrin alpha-V (CD51) staining and Western blot analysis. Co-immunoprecipitation (co-IP) was performed to assess the interplay. The influence on MafB ubiquitination and degradation was evaluated via immunoprecipitation and Western blot. Finally, MafB was knocked down in the USP-overexpressing PBMCs to analyze its effect on osteoclast differentiation. Results: Overexpression of ubiquitin-specific protease 29 (USP29) significantly increased MafB expression by approximately 75% (p < 0.0001). Elevated USP29 levels strongly inhibited osteoclastic differentiation in CD14⁺ PBMCs (p < 0.0001). USP29 was found to interact with MafB, markedly reducing its ubiquitination and subsequent degradation in PBMCs (p < 0.001). Knocking down MafB in USP29-overexpressing PBMCs alleviated the inhibitory effect of USP29 on osteoclastogenesis. Conclusion: USP29 acts as a potent stabilizer of MafB, inhibiting osteoclastogenesis in human CD14⁺ PBMCs, at least in part, by enhancing MafB stability. These findings expand our understanding of USP29’s role and the post-translational regulation of MafB. Furthermore, USP29 serves as a vital factor that controls osteoclast differentiation, and its regulatory function is at least partially mediated by deubiquitinating and stabilizing MafB.