M2 macrophage-derived exosomes improve periodontitis-induced inflammatory bone loss by regulating glycolysis in male rats.

M2 macrophage-derived exosomes (M2-Exo) have emerged as promising therapeutic agents for bone regeneration; however, the mechanisms underlying their protective effects against periodontitis-associated bone loss remain poorly understood. In this study, a rat model of periodontitis was established through silk ligation combined with lipopolysaccharide (LPS) injection. Animals received local administration of M2-Exo with or without the glycolysis inhibitor 2-deoxy-D-glucose (2-DG). Alveolar bone regeneration was evaluated using micro-computed tomography (micro-CT), whereas histological alterations were assessed by hematoxylin and eosin (H&E), Masson's trichrome, tartrate-resistant acid phosphatase (TRAP), and Goldner's trichrome staining. Expression of TRIM26, RUNX2, and pyruvate kinase M2 (PKM2) was analyzed by immunohistochemistry. Micro-CT analysis demonstrated that M2-Exo markedly improved alveolar bone integrity, as evidenced by an increased bone volume fraction (BV/TV) and a reduced distance between the alveolar bone crest and cementoenamel junction (ABC-CEJ). Histological examination further confirmed these regenerative effects, revealing more organized trabecular architecture, reduced inflammatory cell infiltration, and attenuated collagen deposition and fibrosis. Consistently, Goldner's trichrome staining indicated enhanced bone mineralization, whereas TRAP staining demonstrated decreased osteoclast activity. At the molecular level, M2-Exo treatment significantly increased the expression of RUNX2 and PKM2 while suppressing TRIM26 expression. Notably, co-administration of 2-DG partially abrogated these beneficial effects, indicating a critical role for glycolytic metabolism in M2-Exo-mediated bone regeneration. Collectively, these findings demonstrate that M2-Exo promotes alveolar bone regeneration in periodontitis, at least in part, by enhancing glycolysis through the TRIM26/PKM2/RUNX2 signaling axis. This study provides mechanistic insight into exosome-mediated metabolic regulation and highlights its therapeutic potential for the treatment of periodontitis-associated bone loss.