Roxadustat Inhibits Osteoclast Differentiation and Function by Disrupting Cell Cycle Exit

Bone remodeling relies on a balance between osteoclast-mediated resorption and osteoblast-mediated formation. Roxadustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, promotes osteoblast differentiation but its effects on osteoclasts remain unclear. This study investigated roxadustat’s impact on osteoclast differentiation and function in vitro using primary murine bone marrow-derived mononuclear cells differentiated with M-CSF and RANKL. Cell viability, TRAP staining, bone resorption assays, RNA-seq, flow cytometry, immunofluorescence, Western blot for p27, and rescue experiments with the cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor abemaciclib were performed. Roxadustat suppressed osteoclast differentiation and resorption without cytotoxicity in a concentration-dependent manner. RNA-seq revealed enrichment of cell cycle pathways; although differentiation was inhibited, roxadustat paradoxically promoted osteoclast precursor proliferation, evidenced by increased Ki67 and decreased p27 expression. The inhibitory effects on osteoclastogenesis and resorption were partially reversed by abemaciclib. Given that terminal differentiation typically requires cell cycle exit, these findings suggest that roxadustat may inhibit osteoclast differentiation at least in part by disrupting this process, promoting precursor proliferation, and downregulating p27. Together with its known anabolic effects on osteoblasts, roxadustat might have dual therapeutic potential for bone disorders with renal anemia, such as osteoporosis in chronic kidney disease.