GATA1 Knockdown Attenuates Osteoclast Differentiation and Subchondral Bone Loss in Experimental Osteoarthritis Through an SKP2-Associated Mechanism

Background: Osteoclast-mediated subchondral bone remodeling contributes to osteoarthritis (OA), but the role of GATA binding protein 1 (GATA1) remains unclear. This study examined whether GATA1 is associated with osteoclast differentiation and S-phase kinaseassociated protein 2 (SKP2) regulation in experimental OA. Methods: OA was induced by anterior cruciate ligament transection in rats. Bulk subchondral bone mRNA sequencing, intra-articular GATA1 knockdown, micro-computed tomography, histology, and tartrateresistant acid phosphatase (TRAP) staining were combined with nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) induced differentiation of RAW264.7 cells, gene-expression analyses, NFATc1 localization, Filamentous actin (F-actin)-ring assessment, an SKP2 promoter-reporter assay, and SKP2 rescue. Results: GATA1 expression was elevated in bulk OA subchondral bone. GATA1 knockdown was associated with higher bone mineral density and bone volume and fewer TRAP-positive osteoclasts in vivo. In RAW264.7 cells, GATA1 knockdown reduced TRAP-positive multinucleated cells, osteoclast-associated gene expression, NFATc1 nuclear localization, and F-actin-ring formation. GATA1 overexpression increased SKP2 promoter-reporter activity, whereas SKP2 overexpression partially reversed the effects of GATA1 knockdown. Conclusions: The findings support an SKP2-associated role for GATA1 in osteoclast differentiation and subchondral bone remodeling. Direct GATA1 binding to endogenous SKP2, cell-resolved localization in vivo, and validation in primary cells, human OA, and reciprocal epistasis models remain necessary.