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Aberrant scar formation, which includes keloid and hypertrophic scars, is associated with a pathological disorganized wound healing process with chronic inflammation. The TGF-β/Smad signaling pathway is the most canonical pathway through which the formation of collagen in the fibroblasts and myofibroblasts is regulated. Sustained activation of the TGF-β/Smad signaling pathway results in the long-term overactivation of fibroblasts and myofibroblasts, which is necessary for the excessive collagen formation in aberrant scars. There are two categories of therapeutic strategies that aim to target the TGF-β/Smad signaling pathway in fibroblasts and myofibroblasts to interfere with their cellular functions and reduce cell proliferation. The first therapeutic strategy includes medications, and the second strategy is composed of genetic and cellular therapeutics. Therefore, the focus of this review is to critically evaluate these two main therapeutic strategies that target the TGF-β/Smad pathway to attenuate abnormal skin scar formation.

The renin-angiotensin system (RAS) plays an important role in scar formation. We have previously shown that oral administration of ramipril and losartan could inhibit scarring. For easier application, here we developed a series of topical ramipril and losartan creams in different concentrations and formulations to explore the effect on scar formation in a C57BL/6 mouse scar model. The harvested scar tissues were analyzed with H&E staining, Masson staining and immunohistochemical staining. We found the group treated with 0.2% losartan urea cream (Prep. 1) or 0.1% ramipril cream (Prep. 2) had significantly smaller scars compared to the negative control, while the proliferation of fibroblasts was less active and the collagen fibers were more regular; both groups showed similar efficacy with the positive control (triamcinolone acetonide urea). We also found that drug transdermalness couldn’t directly determine the efficacy. Our findings indicate that local application of angiotensin converting enzyme inhibitor drugs (ACEIs) and angiotensin receptor blocker drugs (ARBs) can reduce scarring by reducing the expression of collagen I, collagen III, phosphorylated small mothers against decapentaplegic 3 (p-Smad3) and transforming growth factor-β 1 (TGF-β1). This may provide new insight on scar treatment in clinic.