Sustained-release CGRP microspheres accelerate diabetic wound healing by synergistically promoting neurovascular regeneration through modulation of macrophage and endothelial cell functions

Diabetic refractory wounds are a severe complication of diabetes, often synchronized with diabetic peripheral neuropathy. In this study, we demonstrated a significantly downregulated expression of calcitonin gene-related peptide (CGRP) in the skin tissues of both diabetic patients and diabetic mouse models. This observation implies the crucial role of CGRP in diabetic wound healing. Based on this discovery, we engineered glucose-responsive along with sustained-release antibacterial hydrogel microspheres (BA-HPCS@CGRP) for the controlled delivery of CGRP and conducted systematic evaluation of its therapeutic efficacy. In vitro findings demonstrated that microspheres not only directly enhanced the migration and tube formation capabilities of endothelial cells impaired by high glucose but also further facilitated the restoration of endothelial cell function by promoting the secretion of angiopoietin-like protein 4 (Angptl4) by macrophages after switching to M2 phenotype by CGRP. The results from diabetic mouse models showed that BA-HPCS@CGRP accelerated diabetic wound healing by modulating macrophage polarization towards to M2 phenotype and reduced inflammation, promoted neurovascular regeneration and restored the local CGRP expression. These findings suggest that sustained releasing of low concentration of CGRP provides novel therapeutic approaches for diabetic wounds via modulating macrophage. Moreover, BA-HPCS@CGRP achieves comprehensive sequential therapy through the synergistic modulation of the "neuro-immune-vascular" axis, which might open new perspective to chronic wounds and regenerative medicine.