The effect of halofuginone, an inhibitor of collagen type I synthesis, on urethral stricture formation: In vivo and in vitro study in a rat model

Purpose: Urethral strictures are narrowing of the urethra caused by fibrosis due to excessive collagen production in response to an insult. We evaluated the effects of halofuginone, a potent inhibitor of collagen α1(I) gene expression, on experimentally induced urethral strictures in vivo and on rat urethral fibroblasts in vitro. Materials and Methods: Applying coagulation current to the male rat urethra produced urethral strictures. Halofuginone was given to the animals for 7 days, starting on the day of stricture formation, either orally at 1 and 5 ppm in the diet or by injection of 0.03% halofuginone solution into the urethra. All rats were sacrificed on day 21. Collagen α1(I) gene expression was evaluated by in situ hybridization, collagen content by sirius red staining and urethral morphology by urethrogram. Results: Coagulation current produced reproducible strictures with a typical urethrogram appearance, which were associated with increases in collagen α1(I) gene expression and collagen content at the stricture site. Halofuginone injected into the urethra or orally at 5 ppm normalized the urethrogram and prevented increases in collagen α1(I) gene expression and collagen content. Halofuginone at a concentration of 10^-8 M. inhibited the collagen secreted by fibroblasts derived from the rat male urethra, which was due to inhibition of the collagen α1(I) gene expression. Conclusions: Halofuginone prevented stricture formation and may become an important mode of therapy in the prevention of restenosis during urethral stricture formation.