Transforming Growth Factor-β1 Induced Urethral Fibrosis in a Rat Model

Purpose: We sought to develop a reproducible TGF-beta 1 injection technique to induce urethral fibrosis in the rat urethra. Materials and Methods: A total of 32 male Sprague Dawley (R) rats weighing 300 to 350 gm were anesthetized with ketamine/xylazine intraperitoneally. Using a 5 mm penoscrotal incision the rat urethra was exposed. In the experimental group varying doses of TGF-beta 1 (5, 10 and 25 mu g) were injected in each side of the urethral wall. Normal saline infiltration was used in the sham treated group. Rats were sacrificed 2 and 4 weeks following TGF-beta 1 injection. Urethral specimens were stained with hematoxylin and eosin, and Masson trichrome, and Western blot evaluations were performed. Normal and strictured urethral tissues from patients were collected and evaluated in the same fashion. Results: There was no evidence of urethral wall thickening or fibrosis in the sham treated group. Varied histological evidence of fibrosis was noted in all experimental groups. There was a significant increase in collagen type I expression 2 weeks after injection of 5, 10 and 25 mg TGF-beta 1. Collagen type III expression was significantly increased 2 weeks after injecting 10 and 25 mg of TGF-beta 1, which persisted to 28 days after injection. Conclusions: TGF-beta 1 injection can successfully generate a reproducible rat model of urethral spongiofibrosis. This technique is simple, inexpensive and reproducible. Our series is a proof of concept study. Additional studies in larger animals are needed to further confirm our findings.