Acupuncture accelerates wound healing via CGRP-RAMP1-TSP1-mediated macrophage M2 polarization.

BACKGROUND: Macrophages orchestrate the immune microenvironment during skin wound healing. While acupuncture's efficacy in accelerating wound healing is established, its underlying mechanisms, particularly those related to macrophage modulation, remain poorly characterized. This study aimed to investigate how acupuncture modulates macrophage phenotype and inflammatory responses to facilitate skin repair. METHODS: We established an 8-mm full-thickness dorsal skin defect model in C57BL/6 J mice, randomizing them into control and acupuncture groups. To investigate the role of the calcitonin gene-related peptide (CGRP) pathway, the CGRP receptor antagonist BIBN4096 was administered intradermally before each acupuncture treatment. For the acupuncture group, we performed a daily 20-min intervention for 10 days, which consisted of oblique manual needling at four predefined locations around the wound. Wound repair quality, inflammatory cytokine levels, and macrophage polarization were assessed using histological analysis (H&E and Masson's staining), flow cytometry, enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and reverse transcription quantitative polymerase chain reaction (RT-qPCR). RESULTS: Acupuncture significantly facilitated wound closure, enhanced collagen deposition, and improved tissue repair quality. These benefits were associated with an immunomodulatory effect, characterized by enhanced M2 macrophage polarization within the wounds, a reduction in systemic macrophage load in the spleen, and reduced local and systemic levels of IL-1β and IL-6. Mechanistically, the activation of the CGRP-RAMP1-TSP-1 pathway was critical, as its inhibition with BIBN4096 abrogated the effects of acupuncture on macrophage polarization and wound healing. Notably, the suppression of inflammatory cytokines by acupuncture was only partially dependent on CGRP signaling. CONCLUSIONS: Our findings indicate that acupuncture promotes wound healing and inflammation resolution, at least in part, by activating the CGRP-RAMP1-TSP-1 pathway to drive M2 macrophage polarization. Furthermore, the persistence of its anti-inflammatory effects after CGRP inhibition strongly suggests the involvement of additional, non-CGRP-dependent pathways in modulating the immune response.