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TGFβ reprograms TNF stimulation of macrophages towards osteoclastogenesis [ATAC-seq]

ABSTRACT: TNF plays a key role in inflammation and bone resorption. However, the mechanisms regulating TNF-mediated osteoclastogenesis remain largely unclear because its direct osteoclastogenic ability is weak. Here, we found that TGFβ priming enables TNF to effectively induce osteoclastogenesis from macrophages, independently of the osteoclastogenic action of RANKL. Lack of TGFβ signaling in macrophages suppresses inflammatory, but not physiological, osteoclastogenesis and bone resorption in vivo. Mechanistically, TGFβ priming reprograms macrophage response to TNF towards osteoclastogenesis by remodeling chromatin accessibility and histone modification. TGFβ and TNF induce an unconventional osteoclastogenic program, which includes the suppression of the TNF-induced IRF1-IFNβ-IFN stimulated gene (ISG) axis, promotion of IRF8 degradation and B-Myb induction. These mechanisms are present in RA, in which TGFβ level is elevated and correlated with osteoclast activity. Our findings identify a function and mechanism of action for TGFβ in TNF-mediated inflammatory osteoclastogenesis, and open avenues for selective treatment of inflammatory bone loss.

ORGANISM(S): Homo sapiens

PROVIDER: GSE171841 | GEO | 2022/03/24

REPOSITORIES: GEO

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Project description:Clarification of the mechanisms underlying osteoclast differentiation enable us to understand the physiology of bone metabolism as well as the pathophysiology of bone diseases, such as osteoporosis. Recently, it has been reported that epigenetics can determine the cell fate and regulate cell type specific gene expression. However, little is known about epigenetics during osteoclastogenesis. To reveal a part of epigenetics, especially focused on chromatin dynamics, during early osteoclastogenesis and identify novel transcription factors involved in osteoclastogenesis, we investigated genome-wide analysis of open chromatin during receptor activator of nuclear factor-M-NM-:B ligand (RANKL)-induced osteoclastogenesis using DNase I hypersensitive sites sequencing (DNase-seq). DNase-seq was performed using the extracted nuclei obtained from RAW264 cells treated with or without RANKL for 24 hours, followed by several bioinformatic analyses. DNase I hypersensitive sites (DHSs) during RANKL-induced osteoclastogenesis were dynamically changed and accumulated in promoter regions, although the distributions of DHSs among cis-regulatory DNA regions were identical regardless of RANKL stimulation. Motif discoveries from DHSs successfully identified well-known osteoclastogenic transcription factors such as Jun, CREB1, FOS, ATF2 and ATF4, but also novel transcription factors for osteoclastogenesis such as Zscan10, Atf1 Nrf1 and Srebf2. siRNA knockdown of these identified novel transcription factors impaired osteoclastogenesis. Taken together, DNase-seq can be a useful tool for comprehension of epigenetics, especially chromatin dynamics during osteoclastogenesis and for identification of novel transcription factors involved in osteoclastogenesis. This study may reveal underlying mechanisms that determine cell-type specific differentiation of bone cells and may lead to investigate novel therapeutic targets for osteoporosis. Examination of genome-wide DNase Hypersensitive Sites in differentiated and undifferentiated RAW264 cells.

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TGFβ reprograms TNF stimulation of macrophages towards osteoclastogenesis [ATAC-seq]

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