Effect of Relaxin Expression from an Alginate Gel-Encapsulated Adenovirus on Scar Remodeling in a Pig Model

Purpose: Relaxin (RLX) is a transforming growth factor-beta 1 (TGF-beta 1) antagonist that is believed to function as a potent collagen re-arranger and a major suppressor of extracellular matrix components. Adenoviruses (Ads) are accepted vectors for cancer gene therapy. However, repeated treatments of Ad are limited by short-term biological activity in vivo. The efficacy of sustained RLX expression to scar remodeling was assessed using an injectable alginate gel-matrix system. Materials and Methods: Pig scar tissue was treated with relaxin-expressing Ad loaded in alginate gel (gel/Ad-RLX). Surface areas, color, and pliability of scars were compared, and various factors influencing scar formation and collagen arrangement were analyzed. Results: Gel/Ad-RLX decreased scar size, color index, and pliability. Immunohistochemistry showed decreased levels of major extracellular matrix proteins in the gel/Ad-RLX-treated group. Furthermore, treatment with gel/Ad-RLX reduced expression of tissue inhibitor of metalloproteinase-1 and alpha-smooth muscle actin and markedly increased expression of matrix metalloproteinase-1 in pig scar tissues. Gel/Ad-RLX also significantly downregulated TGF-beta 1 and upregulated TGF-beta 3 mRNAs in pig scar tissues. Conclusion: These results support a prominent role for RLX in scar remodeling and suggest that gel/Ad-RLX may have therapeutic effects on scar formation.