SIR-4156

Senescence of bone marrow mesenchymal stem cells (BMSCs) impairs their stemness and osteogenic differentiation, which is the principal cause of senile osteoporosis (SOP). Imbalances in nicotinamide phosphoribosyltransferase (NAMPT) homeostasis have been linked to aging and various diseases. Herein, reduction of NAMPT and impaired osteogenesis were observed in BMSCs from aged human and mouse. Knockdown of Nampt in BMSCs promotes lipogenic differentiation and increases age‐related bone loss. Overexpression of Nampt ameliorates the senescence‐associated (SA) phenotypes in BMSCs derived from aged mice, as well as promoting osteogenic potential. Mechanistically, NAMPT inhibits BMSCs senescence by facilitating OPA1 expression, which is essential for mitochondrial dynamics. The defect of NAMPT reduced mitochondrial membrane potential, interfered with mitochondrial fusion，and increased SA protein and phenotypes. More importantly, we have confirmed that P7C3, the NAMPT activator, is a novel strategy for reducing SOP bone loss. P7C3 treatment significantly prevents BMSCs senescence by improving mitochondrial function through the NAMPT‐OPA1 signaling axis. Taken together, these results reveal that NAMPT is a regulator of BMSCs senescence and osteogenic differentiation. P7C3 is a novel molecule drug to prevent the pathological progression of SOP.