Abstract
OBJECTIVE: Multinucleated osteoclasts are the principal specialised cells responsible for bone resorption, but osteoclastogenesis, the formation of osteoclasts, entails substantial nutrient and bioenergetic demands. Macropinocytosis is an efficient pathway for nutrient scavenging in metabolically active cells; however, the interplay among metabolic state, osteoclast differentiation and macropinocytosis in bone-related diseases remains poorly understood. METHODS: In this study, osteoclast differentiation was induced using murine bone marrow-derived macrophages and RAW 264.7 cells to investigate the role of macropinocytosis in metabolic regulation. Lipopolysaccharide (LPS) was applied to mimic inflammatory conditions in vitro to assess the influence of macropinocytosis on both metabolic profiles and inflammation-associated osteoclastogenesis. Additionally, ligature-induced periodontitis and ovariectomy (OVX)-induced bone loss models in mice were employed to evaluate the in vivo impact of macropinocytosis on bone resorption. RESULTS: Enhanced macropinocytosis promoted osteoclast formation, with LPS further accelerating differentiation and increasing macropinocytic activity. This upregulation helped to meet the energy requirements of osteoclastogenesis via oxidative phosphorylation and glycolysis. Inhibition of macropinocytosis with (N-ethyl-N-isopropyl) amiloride (EIPA) reduced energy production and suppressed osteoclast differentiation. Elevated macropinocytosis was also observed in the periodontitis and OVX models, and its inhibition led to early, dose-dependent restoration of bone mass. CONCLUSION: Macropinocytosis provides a critical energy source for osteoclast differentiation. Targeting this pathway with EIPA represents a promising therapeutic approach for bone-related diseases. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: As a bulk endocytic process, macropinocytosis offers a novel therapeutic target for bone-related diseases. The efficacy of EIPA in suppressing osteoclastogenesis and bone resorption suggests its potential as a clinical intervention drug.