Substance P Promotes Wound Healing Primarily Through the NK-1 Receptor by Stimulating Cell Migration and TGF-β1 Release

Substance P alone significantly stimulated fibroblast proliferation and migration in both scratch assays (horizontal) and transwell assays (vertical) over 24 hours. Blocking the NK-1 receptor with spantide II abolished substance P's ability to stimulate cell migration. NK-2 receptor antagonism also significantly reduced migration but was less effective than NK-1 blockade. Combined NK-1 and NK-2 antagonism produced the greatest inhibition. TGF-β1 levels were significantly elevated in substance P-treated cell supernatants, while all receptor antagonist combinations showed significantly lower TGF-β1 levels than substance P alone.

In vitro study using buffalo fetal fibroblast cultures. Wound healing was modeled using scratch assays (horizontal migration) and transwell assays (vertical migration). Substance P was tested alone and in combination with specific receptor antagonists: spantide II (NK-1 antagonist), an NK-2 antagonist, and both together. TGF-β1 levels in cell culture supernatants were measured by immunoassay. Cell proliferation was also assessed.

Chronic non-healing wounds (diabetic foot ulcers, pressure sores, venous leg ulcers) affect millions worldwide and cost healthcare systems billions. Understanding the specific receptor mechanism behind substance P's wound healing effects opens the door to targeted peptide-based wound therapies. If NK-1 receptor activation is the key, then substance P analogs or NK-1 agonists could be developed as topical wound treatments.

Neuropeptides are increasingly recognized for roles beyond nervous system signaling — they regulate immune responses, inflammation, and tissue repair. Substance P's wound healing properties connect the nervous system directly to tissue regeneration, explaining why denervated wounds (in diabetic neuropathy, for example) heal poorly. NK-1 receptor agonists could potentially restore this healing signal in conditions where nerve-derived substance P is deficient.

This was an in vitro study using buffalo fetal fibroblasts, which may not perfectly represent human adult skin wound healing biology. No in vivo wound healing experiments were conducted. The study used a single cell type (fibroblasts) and did not examine substance P's effects on other wound healing cells (keratinocytes, endothelial cells, immune cells). TGF-β1 was the only growth factor measured, though substance P likely affects multiple healing mediators.