Bone transport induces CGRP release from sensory nerves to promote angiogenesis and heal diabetic foot wounds in rats

Abstract Diabetic foot ulcer (DFU) is a critical complication of diabetes, characterized by high recurrence rates, high disability rates, high mortality, and a significant socioeconomic burden. The tibial cortex transverse transport therapy, based on the tension-stress effect, has demonstrated significant efficacy in promoting the healing of DFUs; however, its underlying mechanisms remain incompletely elucidated. Recent evidence show calcitonin gene-related peptide (CGRP) is important for tissue regeneration. However, its role in BT-mediated healing is still unknown. This study aimed to investigate whether and how sensory nerves participate in the process of BT-promoted DFU healing via the release of CGRP. A femoral BT model was established in diabetic rats, with concurrent creation of an ischemic and dorsal foot wound model on the ipsilateral hindlimb. Capsaicin was employed to ablate sensory nerves and block CGRP release. Animals were allocated into four groups: sham-operated group, external fixator group, BT group, and BT + capsaicin group. Wound healing rate, angiogenesis, and CGRP expression in the DRG and regenerated skin were assessed. Transcriptomic analysis was performed on healed skin tissue. In vitro, the effects of CGRP on tube formation ability, as well as on the expression of CD31, VEGFA, and FAK phosphorylation, were evaluated in HUVECs. The BT technique significantly promoted the healing of dorsal foot wounds in diabetic rats ( P < 0.05) and increased the count of newly formed blood vessels within the wounds ( P < 0.05). CGRP release from sensory nerve axons in the DRG and within the wounds was significantly increased ( P < 0.05). Following sensory nerve blockade by capsaicin, CGRP secretion decreased, and both angiogenesis and wound healing rates were significantly slowed ( P < 0.05). Transcriptome sequencing revealed that DEGs in the BT group were significantly enriched in the nervous system development and tube formation systems. In vitro experiments confirmed that CGRP promoted endothelial cell tube formation in a dose-dependent manner ( P < 0.05), upregulated the expression of angiogenesis-related proteins and genes such as CD31 and VEGFA, and promoted FAK phosphorylation ( P < 0.05). The bone transport technique promotes diabetic foot wound healing via a “nerve-vessel-regeneration” axis. CGRP secreted by sensory nerves mediates this process, potentially by enhancing angiogenesis through the CGRP-FAK-VEGF signaling axis.