PALLADIN regulates osteogenic differentiation of bone marrow mesenchymal stem cells and protects against bone loss in ovariectomized mice

Abstract

Abstract Osteoporosis is a systemic skeletal disease associated with reduced bone density and impaired bone quality, which leading to a greater risk of fracture. The pathogenesis of osteoporosis is closely associated with compromised osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). The actin-cytoskeleton associated protein PALLADIN has been reported to play a central role in the remodeling of the actin-cytoskeleton. However, no studies to date have established whether PALLADIN can influence osteogenic differentiation of BMSCs or the onset of osteoporosis. Here, PALLADIN knockdown was observed to reduce osteogenic differentiation of BMSCs, confirming the involvement of the gene in osteoporosis. Knockdown also altered the cytoskeletal organization and reduced Ras homolog family member A (RhoA) activity to inhibit osteogenic differentiation. The results of the in vivo experiments showed that overexpression of Palladin reversed bone loss and marrow adipose tissue (MAT) accumulation in OVX mice, while Palladin knockdown increased both bone loss and MAT accumulation in OVX mice. Together, these results suggest a model in which Palladin protects against bone loss induced by OVX through the promotion of BMSCs osteogenesis. In human osteoporotic BMSCs, PALLADIN expression is significantly downregulated, correlating with disease status. While functional validation in primary human osteoporotic BMSCs remains to be performed, these preclinical findings establish Palladin as a novel regulator of BMSCs osteogenic differentiation and provide a foundation for future efforts to characterize the pathogenesis of osteoporosis and identify new therapeutic targets.