LSD1 knockdown confers protection against osteoclast formation by reducing histone 3 lysine 9 monomethylation and dimethylation in ITGB3 promoter.

ITGB3, an osteoclast marker, is involved in osteoclast formation. Nevertheless, its related mechanism remains poorly characterized. Herein, this study examines the mechanisms affecting osteoclast formation with the involvement of ITGB3. Osteoclast formation was induced with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-kappa B ligand (RANKL), followed by measurement of the mRNA and protein expression of ITGB3 and LSD1. After gain- and loss-of-function assays, cell viability and the expression of osteoclast marker genes (NFATc1, ACP5, and CTSK) were assessed, and osteoclast formation was evaluated with TRAP staining. ChIP assays were used to examine histone 3 lysine 9 (H3K9) monomethylation (H3K9me1) and H3K9 dimethylation (H3K9me2) modifications and LSD1 protein enrichment in the ITGB3 promoter. During osteoclast formation, ITGB3 and LSD1 were gradually augmented. Knockdown of LSD1 or ITGB3 curbed cell viability, the expression of osteoclast marker genes, and osteoclast formation. Moreover, overexpression of ITGB3 nullified the suppressive impact of LSD1 knockdown on osteoclast formation. Mechanistically, LSD1 promoted ITGB3 expression by reducing H3K9 levels in the ITGB3 promoter. LSD1 enhanced ITGB3 expression by decreasing H3K9me1 and H3K9me2 levels in ITGB3 promoter to boost osteoclast formation.