Immunometabolism of macrophages in the bone microenvironment: a new perspective for bone healing therapy

BACKGROUND: Immunometabolism, the regulation of immune cell function through metabolic pathways, has emerged as a key focus in regenerative medicine. Traditional bone healing therapies primarily target the osteoblast-osteoclast regulatory axis, overlooking the metabolic reprogramming of immune cells (e.g., macrophages) and limiting regenerative efficiency. Macrophages orchestrate bone healing through dynamic shifts between proinflammatory (M1-like) and reparative (M2-like) metabolic phenotypes. Recent studies have shown that their immunometabolic transitions govern the sequential phases of bone healing. Therefore, targeting macrophage immunometabolism may offer a novel therapeutic paradigm for bone regeneration. AIM OF REVIEW: This review summarizes recent advances in understanding how macrophage metabolism regulates bone healing, emphasizing the critical role of immunometabolism in resolving inflammation and regenerating tissue throughout the repair process. By integrating insights from the fields of cellular metabolism, microenvironmental signals, and biomaterial science, this review aims to offer an integrative perspective on how targeting macrophage metabolic control could serve as a therapeutic strategy to enhance bone regeneration. KEY SCIENTIFIC CONCEPTS OF REVIEW: This review addresses five core concepts. First, it delineates the spatiotemporal roles and phenotypic shifts of macrophages in the different phases of bone healing. Second, it explores how the reprogrammed metabolism of glucose, lipids, and amino acids underlies macrophage polarization and function. Third, it emphasizes how microenvironmental cues, including cytokines, metabolic intermediates, and microbiota-derived metabolites, modulate macrophage immunometabolism. Fourth, it summarizes emerging therapeutic strategies designed to regulate macrophage metabolism for bone regeneration, such as cell-based therapies, immunomodulatory hydrogels, and nanotechnologies. Finally, it identifies major challenges in this field. These include the temporal-spatial complexity of immunometabolism, the lack of human-relevant models, the emerging concepts of cross-system regulation, and the technological limitations in targeted regulation. Together, these insights provide a conceptual basis for future precision immunometabolic interventions in bone repair.