Plasminogen activator inhibitor-I–related regulation of procollagen I (α 1 and α 2) by antitransforming growth factor-β 1 treatment during radiation-impaired wound healing

Abstract

Purpose: Plasminogen activator inhibitor (PAI)-1 mediates transforming growth factor-β₁ (TGF-β₁)–related signaling by stimulating collagen Type I synthesis in radiation-impaired wound healing. The regulation of α(I)-procollagen is contradictory in fibroblasts of different fibrotic lesions. It is not known whether anti–TGF-β₁ treatment specifically inhibits α(I)-procollagen synthesis. We used an experimental wound healing study to address anti–TGF-β₁–associated influence on α(I)-procollagen synthesis. Methods and Materials: A free flap was transplanted into the preirradiated (40 Gy) or nonirradiated neck region of Wistar rats: Group 1 (<i>n</i> = 8) surgery alone; Group 2 (<i>n</i> = 14) irradiation and surgery; Group 3 (<i>n</i> = 8) irradiation and surgery and anti–TGF-β₁ treatment. On the 14th postoperative day, skin samples were processed for fibroblast culture, <i>in situ</i> hybridization for TGF-β₁, immunohistochemistry, and immunoblotting for PAI-1, α₁/α₂(I)-procollagen. Results: Anti–TGF-β₁ significantly reduced TGF-β₁ mRNA (<i>p</i> < 0.05) and PAI-1 expression (<i>p</i> < 0.05). Anti–TGF-β₁ treatment <i>in vivo</i> significantly reduced α₁(I)-procollagen protein (<i>p</i> < 0.05) and the number of expressing cells (<i>p</i> < 0.05) in contrast to significantly increased (<i>p</i> < 0.05) α₂(I)-procollagen expression. Conclusion: These results emphasize anti–TGF-β₁ treatment to reduce radiation-induced fibrosis by decreasing α₁(I)-procollagen synthesis <i>in vivo</i>. α₁(I)-procollagen and α₂(I)-procollagen might be differentially regulated by anti–TGF-β₁ treatment. Increased TGF-β signaling in irradiated skin fibroblasts seemed to be reversible, as shown by a reduction in PAI-1 expression after anti–TGF-β₁ treatment.