An endoplasmic reticulum stress-responsive nanocomposite hydrogel for diabetic wound healing through a fibroblast-immune cell dual regulation hub

Diabetic wounds exhibit excessive endoplasmic reticulum stress (ERS), which can lead to fibroblast dysfunction, abnormal natural killer (NK) cell activation, and imbalanced macrophage polarization. ERS exerts a bidirectional regulatory effect on wound fibroblasts and immune cells; simply inhibiting ERS impedes wound tissue regeneration. Existing hydrogels cannot precisely regulate ERS and synergistically repair multicell functional defects. Monocyte Chemoattractant Protein-1 (MCP-1), synthesized by fibroblasts in diabetic wounds, is a key molecular regulator of ERS and fibroblast function and a hub for fibroblast-immune cell interactions. This study constructed histidine-chitosan-fibroblast growth factor receptor (FGFR) agonist peptide 1 (FAP1)-pGPU6/GFP/Neo MCP-1-shRNA plasmid (HCFD) nanoparticles. The HCFD nanoparticles were loaded onto 3-carboxyphenylboronic acid (PBA)-modified methyl acrylate gelatin (GelMA) hydrogel (GP), forming the nanocomposite hydrogel Gel-PBA-HCFD (GPHCFD). The GPHCFD nanocomposite hydrogel utilizes FAP1 to target FGFR on wound fibroblasts. Under conditions of excessive ERS, GPHCFD nanocomposite hydrogels were triggered to break boric acid bonds and protonate histidine imidazole, thereby achieving the precise release of the plasmid, which could stably knock out the MCP-1 gene in fibroblasts. Notably, GPHCFD exhibited excellent ERS-responsive functionality, significantly reducing MCP-1 expression and alleviating excessive ERS in fibroblasts under in vitro thapsigargin (Tg)-induced high ERS conditions and high ERS environments in diabetic wounds. GPHCFD improved fibroblast proliferation, migration, and collagen secretion functions. Furthermore, GPHCFD inhibited inflammatory factors of NK cells, including TNF-α and IFN-γ, as well as the aberrant proliferation of CD45⁺CD3^-NK1.1⁺ NK cells by reducing the MCP-1-mediated activation of the CCR2 receptor on NK cells and ERS. Additionally, CD45⁺CD3^-NK1.1⁺CD11b^- NK cells were encouraged to differentiate into mature CD45⁺CD3^-NK1.1⁺CD11b⁺ NK cells by GPHCFD. Additionally, the GPHCFD nanocomposite hydrogel reduced the MCP-1-mediated activation of the CCR2 receptor on macrophages, thereby decreasing excessive ERS in macrophages and driving their polarization from M1-type CD68⁺iNOS⁺ cells to M2-type CD68⁺CD206⁺ cells. This GPHCFD nanocomposite hydrogel integrates ERS-responsive nanoparticle release, fibroblast gene editing, and immune reprogramming, offering a new therapeutic modality for diabetic wounds incorporating tissue regeneration-immune homeostasis synergistic regulation.