Hypertrophic scar regression is linked to the occurrence of endothelial dysfunction

Most microvessels have been shown to become stenosed or completely occluded during hypertrophic scar progression. Here, we examined the morphology of capillary endothelial cells (ECs) and fibroblasts using immunofluorescence staining for CD31 and alpha-smooth muscle actin (α-SMA) and electron microscopy. In addition, ECs and fibroblasts were isolated from scar tissues, and the levels of transforming growth factor beta 1 (TGF-β1), platelet-derived growth factor (PDGF), endothelin 1 (ET-1), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were assayed using ELISAs. Furthermore, we assessed cell viability, total collagen production, and cell apoptosis in hypertrophic scar-derived fibroblasts cultured with EC-conditioned medium. Then, anti-TGF-β1, anti-PDGF, anti-ET-1, anti-VEGF, and anti-bFGF neutralising antibodies were individually added to the EC medium to identify which growth factor plays a more important role in inhibiting fibroblasts biology. Our results showed microvessel lumen occlusion and EC atrophy during scar development, particularly in regressive scars (RSs). Additionally, EC growth factor secretion decreased and reached the lowest levels in RSs. Furthermore, based on the culture results, RS EC medium inhibited fibroblast viability and collagen production and induced apoptosis. Moreover, TGF-β1, PDGF, and bFGF played more important roles in these processes than VEGF and ET-1. The endothelial dysfunction occurring in hypertrophic scars contributes to fibroblast inhibition and scar regression, and reduced TGF-β1, PDGF, and bFGF levels play key roles during this process.