The role of oral and transurethral pirfenidone administration for preventing urethral stricture formation in experimental urethral stricture models in rabbits and its effects on biomarkers

Abstract Background: Urethral stricture is characterized by the narrowing of the urethra due to the formation of scar tissue. The pathogenesis of urethral stricture involves a fibrotic process caused by excessive collagen synthesis and changes in the composition of the extracellular matrix. Various agents with antifibrotic activity have been studied in experimental models of urethral stricture prevention, including Halofuginone, Mitomycin C, Botulinum toxin A, somatostatin analogs, glucocorticoids, and Rapamycin. Pirfenidone is a drug used in the treatment of interstitial pulmonary fibrosis known for its antifibrotic, anti-inflammatory, and antioxidant effect. In this study, we aimed to evaluate the effect of pirfenidone on fibrosis, inflammation, and biomarkers in male rabbits with induced urethral injury. Materials and Methods: Thirteen male New Zealand rabbits, aged 120 ± 20 days and weigthing 3-4 kg, were used. Urethral tissue injury was induced in all rabbits. The rabbits were randomized into three groups. The groups were Sham (urethral injury only), contained 3 rabbits; urethral injury + oral pirfenidone administration, contained 5 rabbits; and urethral injury + intraurethral pirfenidone administration, contained 5 rabbits. Blood samples were collected on days 0-1-3-5-7 and 14 considering the stages of wound healing. Serum levels of TGF-β, IL-1β, TNF-α, PDGF, and FGF were analyzed and recorded. On day 15 following treatment and monitoring, rabbits were sacrificed after penectomy. Formalin-fixed, paraffin-embedded (FFPE) urethral tissue sections were stained with Hematoxylin & Eosin (H&E) and Masson's Trichrome (MT) for histopathological examination under light microscopy, focusing on urethral fibrosis and inflammation, including spongiosal fibrosis and inflammation. Results: Histopathologically, oral pirfenidone treatment significantly reduced inflammation following urethral injury in rabbits. Fibrosis values among the rabbit groups were similar. There was no significant change in FGF, IL-1β and TGF- β levels, biomarkers involved in wound healing, inflammation, and fibrosis formation, between oral pirfenidone and intraurethral pirfenidone treatments. However, PDGF and TNF-alpha levels were suppressed in the group treated with oral pirfenidone, supporting its anti-inflammatory and antifibrotic effects after urethral stricture. Conclusion: Pirfenidone, known for its anti-inflammatory and antifibrotic effects, presents new hopes in the management of urethral fibrosis, where current medical treatment options are limited.