Visfatin Enhances RANKL-Induced Osteoclastogenesis In Vitro: Synergistic Interactions and Its Role as a Mediator in Osteoclast Differentiation and Activation

Visfatin, an adipokine secreted by various cell types, plays multifaceted pathophysiological roles in inflammatory conditions, including obesity, which is closely associated with osteoclastogenesis, a key process underlying bone loss and increased osteoporosis (OP) risk. However, the role of visfatin in osteoclastogenesis remains controversial. This study was conducted to investigate the effects of visfatin on receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation from precursor cells in vitro. Our results demonstrated that although visfatin exhibited a modest osteoclast-inductive effect relative to that of RANKL, co-stimulation of bone marrow-derived macrophages (BMDMs) with visfatin and RANKL led to significantly enhanced osteoclast differentiation and activation compared to individual stimulation. Neutralization of visfatin activity using blocking antibodies before differentiation markedly suppressed RANKL-induced osteoclastogenesis, as evidenced by a near-complete absence of tartrate-resistant acid phosphatase-positive multinucleated osteoclasts, decreased levels of nuclear factor of activated T cells cytoplasmic 1 and osteoclast-specific proteins, inhibition of nuclear factor-κB and mitogen-activated protein kinase signaling pathways, and a decrease in resorption pit formation. Our findings underscore the critical role of visfatin in RANKL-induced osteoclastogenesis in vitro and highlight the RANKL/visfatin signaling axis as a potential therapeutic target for destructive bone loss-related diseases.