Ex vivo evaluation of antifibrotic compounds in skin scarring: EGCG and silencing of PAI-1 independently inhibit growth and induce keloid shrinkage

Abstract

Keloid disease (KD) is a common fibroproliferative disorder of unknown etiopathogenesis. Its unique occurrence in human skin and lack of animal models pose challenges for KD research. The lack of a suitable model in KD and overreliance on cell culture has hampered the progress in developing new treatments. Therefore, we evaluated the effect of two promising candidate antifibrotic therapies: ( À )-epigallocatechin-3-gallate (EGCG) and plasminogen activator inhibitor-1 (PAI-1) silencing in a long-term human keloid organ culture (OC). Four millimeters of air-liquid interface (ALI) keloid explants on collagen gel matrix in serum-free medium (n ¼ 8 cases) were treated with different modalities (EGCG treatment; PAI-1 knockdown by short interfering RNA (siRNA) and application of dexamethasone (DEX) as control). Normal skin (n ¼ 6) was used as control (only for D0 keloid-untreated comparison). Besides routine histology and quantitative (immuno-) histomorphometry, the key phenotypic and growth parameters of KD were assessed. Results demonstrated that EGCG reduced keloid volume significantly (40% by week 4), increased apoptosis (Z40% from weeks 1 to 4), and decreased proliferation (r17% in week 2). EGCG induced epidermal shrinkage, reduced collagen-I and -III at mRNA and protein levels, depleted 98% of keloid-associated mast cells, and reduced the percentage of both cellularity and blood vessel count by week 4. Knockdown of PAI-1 significantly reduced keloid volume by 28% in week 4, respectively, and reduced collagen-I and -III at both mRNA and protein levels. As expected, DEX increased keloid apoptosis, decreased keloid proliferation, and collagen synthesis, but induced connective tissue growth factor overexpression. In conclusion, using keloid OC model, we provide the first functional evidence for testing candidate antifibrotic compounds in KD. We show that EGCG and PAI-1 silencing effectively inhibits growth and induces shrinkage of human keloid tissue in situ. Therefore, the application of EGCG, PAI-1 silencing, and other emerging compounds tested using this model may provide effective treatment and potentially aid in the prevention of recurrence of KD following surgery. Keloid disease (KD) is a benign hyperproliferative dermal disease of unknown etiopathogenesis with ill-defined treatment, 1 which is unique to humans. 2 KD can arise following an abnormal wound healing process in genetically susceptible individuals. 2 The hallmark of KD is excessive deposition of extracellular matrix (ECM) in the dermis. 3 The lack of an animal model that can truly mimic human KD in vivo condition imposes limitations when investigating functional activities of potential therapeutic agents in treating KD. 4,5 However, these models have failed to provide the essential components of skin tissue that occur in vivo, such as mature ECM, blood vessels, inflammatory cells, and intrinsic and extrinsic biochemical interactions. Therefore, the ultimate aim of this study was to determine the applicability of recent research findings in existing i...

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