Suppression of osteoclast multinucleation via a posttranscriptional regulation–based spatiotemporally selective delivery system

AUTHORS

Qingqing Wang, Haoli Wang, Huige Yan, Hongsen Tian, Yining Wang, Wei Yu, Zhanqiu Dai, Pengfei Chen, Zhaoming Liu, Ruikang Tang, Chao Jiang, Shunwu Fan, Xin Liu, Xianfeng Lin

ABSTRACT

Redundancy of multinucleated mature osteoclasts, which results from the excessive fusion of mononucleated preosteoclasts (pOCs), leads to osteolytic diseases such as osteoporosis. Unfortunately, the currently available clinical drugs completely inhibit osteoclasts, thus interfering with normal physiological bone turnover. pOC-specific regulation may be more suitable for maintaining bone homeostasis. Here, circBBS9, a previously unidentified circular RNA, was found to exert regulatory effects via the circBBS9/miR-423-3p/Traf6 axis in pOCs. To overcome the long-standing challenge of spatiotemporal RNA delivery to cells, we constructed biomimetic nanoparticles to achieve the pOC-specific targeted delivery of circBBS9. pOC membranes (POCMs) were extracted to camouflage cationic polymer for RNA interference with circBBS9 (POCM-NPs@siRNA/shRNAcircBBS9). POCM-NPs endowed the nanocarriers with improved stability, accurate pOC targeting, fusogenic uptake, and reactive oxygen species–responsive release. In summary, our findings may provide an alternative strategy for multinucleated cell–related diseases that involves restriction of mononucleated cell multinucleation through a spatiotemporally selective delivery system.

Role of chromatin modulator Dpy30 in osteoclast differentiation and function

AUTHORS

Yanfang Zhao, Xiaoxiao Hao, Zhaofei Li, Xu Feng, Jannet Katz, Suzanne M.Michalek, Hao Jiang, Ping Zhang

ABSTRACT

Osteoclasts are the principal bone resorption cells crucial for homeostatic bone remodeling and pathological bone destruction. Increasing data demonstrate a vital role of histone methylation in osteoclastogenesis. As an integral core subunit of H3K4 methyltransferases, Dpy30 is notal as a key chromatin regulator for cell growth and differentiation and stem cell fate determination, particularly in the hematopoietic system. However, its role in osteoclastogenesis is currently unknown. Herein, we generated Dpy30F/F; LysM-Cre+/+ mice, which deletes Dpy30 in myeloid cells, to characterize its involvement in osteoclast differentiation and function. Dpy30F/F; LysM-Cre+/+ mice showed increased bone mass, evident by impaired osteoclastogenesis and defective osteoclast activity, but no alteration of osteoblast numbers and bone formation. Additionally, our ex vivo analysis showed that the loss of Dpy30 significantly impedes osteoclast differentiation and suppresses osteoclast-related gene expression. Moreover, Dpy30 deficiency significantly decreased the enrichment of H3K4me3 on the promoter region of NFATc1. Thus, we revealed a novel role for Dpy30 in osteoclastogenesis through epigenetic mechanisms, and that it could potentially be a therapeutic target for bone destruction diseases.

TET2 regulates osteoclastogenesis by modulating autophagy in OVX-induced bone loss

AUTHORS

Chen Yang, Huaqiang Tao, Haifeng Zhang, Yu Xia, Jiaxiang Bai, Gaoran Ge, Wenming Li, Wei Zhang, Long Xiao, Yaozeng Xu, Zhirong Wang, Ye Gu,H uilin Yang, Yu Liu & Dechun Geng

ABSTRACT

Increased bone resorption by osteoclasts after estrogen deficiency is the main cause of postmenopausal osteoporosis. TET2 (tet methylcytosine dioxygenase 2) is a DNA demethylase that regulates cellular function and differentiation potential. Macroautophagy/autophagy maintains cellular homeostasis by recycling unnecessary and damaged organelles. This study revealed that TET2 promoted bone loss in oophorectomized (OVX) mice and that TET2 promoted osteoclast differentiation by regulating autophagy. Tet2 knockdown inhibited autophagy and osteoclast differentiation in vitro. Mechanistically, Tet2 knockdown increased BCL2 (B cell leukemia/lymphoma 2) expression and BCL2 exhibited increased binding to BECN1 and negatively regulated autophagy. Small interfering RNA specific to Bcl2 interfered with BCL2 expression in Tet2-knockdown bone marrow cells/precursors, partially reversing autophagy dysregulation and promoting osteoclast differentiation. Moreover, the LV-shTet2 lentivirus prevented bone loss in OVX mice. In summary, our findings provide evidence that TET2 promotes osteoclast differentiation by inhibiting BCL2 expression and positively regulating BECN1-dependent autophagy.