Osteoclast Stimulatory Transmembrane Protein (OC‐STAMP): A Key Regulator in Osteoclast Fusion

The integrity of bone mass depends on the balance between osteoblastic bone formation and osteoclastic bone resorption. Osteoclasts derived from hematopoietic stem cells in bone marrow via a mechanism mediated mainly by two cytokines: the receptor activator of nuclear factor-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). Osteoclast stimulatory transmembrane protein (OC‐STAMP) is a newly identified master fusogen that functions as a regulator of osteoclastogenesis. It is considered a key factor during macrophage fusion and differentiation. Osteoclast formation is mediated by a variety of factors and mechanisms other than OC-STAMP. Furthermore, numerous preclinical studies have investigated drugs that could target osteoclast differentiation, to allow better management of pathological bone metabolism. To improve understanding of osteoclast fusion and differentiation processes, this review will discuss recent findings on OC-STAMP and related signalling pathways.