AT2R Activation Improves Wound Healing in a Preclinical Mouse Model.

Abnormal skin healing resulting in chronic wounds or hypertrophic scarring remains a major healthcare burden. Here, the antifibrotic angiotensin II type 2 receptor (AT2R) signaling pathway was modulated to determine its impact on cutaneous wound healing. Balb/c mice received two splinted full-thickness wounds. Topical treatments with the selective AT2R agonist compound 21 (C21) and/or selective antagonist PD123319 or saline vehicle were administered until sacrifice on post-wounding days 7 or 10. The rate of wound re-epithelialization was accelerated by PD123319 and combination treatments. In vitro, C21 significantly reduced human fibroblast migration. C21 increased both collagen and vascular densities at days 7 and 10 post-wounding and collagen I:III ratio at day 10, while PD123319 and combination treatments decreased them. Genes associated with regeneration and repair were upregulated by C21, while PD123319 treatment increased the expression of genes associated with inflammation and immune cell chemotaxis. C21 treatment reduced wound total leukocyte and neutrophil staining densities, while PD123319 increased these and macrophage densities. Overall, AT2R activation with C21 yields wounds that mature more quickly with structural, cellular, and gene expression profiles more closely approximating unwounded skin. These findings support AT2R signal modulation as a potential therapeutic target to improve skin quality during wound healing.

Ketotifen directly modifies the fibrotic response of human skin fibroblasts.

Fibrosis is a destructive, end-stage disease process. In the skin, it is associated with systemic sclerosis and scarring with considerable health burden. Ketotifen is a clinical antihistamine and mast cell stabilizer. Studies have demonstrated mast cell-dependent anti-fibrotic effects of ketotifen but direct effects on fibroblasts have not been determined. Human dermal fibroblasts were treated with pro-fibrotic transforming growth factor-ß1 (TGFß) followed by ketotifen or control treatments to determine direct effects on fibrotic fibroblasts. Ketotifen impaired TGFß-induced α-smooth muscle actin gene and protein responses and decreased cytoskeletal- and contractility-associated gene responses associated with fibrosis. Ketotifen reduced Yes-associated protein phosphorylation, transcriptional coactivator with PDZ binding motif transcript and protein levels, and phosphorylation of protein kinase B. In a fibroblast-populated collagen gel contraction assay, ketotifen reduced the contractile activity of TGFß-activated fibroblasts. In a murine model of bleomycin-induced skin fibrosis, collagen density and dermal thickness were significantly decreased in ketotifen-treated mice supporting in vitro findings. These results support a novel, direct anti-fibrotic activity of ketotifen, reducing pro-fibrotic phenotypic changes in fibroblasts and reducing collagen fibres in fibrotic mouse skin. Together, these findings suggest novel therapeutic potential and a novel mechanism of action for ketotifen in the context of fibrosis.