Experimental defect in rabbit urethra repaired with acellular aortic matrix

Urethral reconstruction following failed hypospadias repair or post-traumat ic chronic stricture requires adequate amounts of tissue. Many surgical tec hniques utilizing different types of biological tissues have been attempted : (a) vascularized skin flaps from the prepuce, scrotum or penile shaft; (b ) full-thickness free skin grafts; (c) vesical or buccal mucosa grafts; (d) ureter; artery; vein and appendix tissue. More recently, biodegradable pol ymers have also been used as delivery vehicles of urothelial cells in anima ls. It has been demonstrated that the implant of an acellular tissue matrix in the bladder can guide the regeneration of urothelium, blood vessels, sm ooth muscle and nerves. The aim of this study was to create an experimental model of urethral defect, and then repair it by implanting homologous acel lular aortic grafts as urethral substitutes. An acellular matrix was obtain ed by detergent enzymatic treatment of rabbit thoracic aorta. The growth of urethral epithelium was verified in vitro, and homologous acellular vessel s were then implanted in rabbits, bridging a previous surgical urethral def ect. The outcome of reconstructive surgery was evaluated histologically at 10 days, 3 weeks, 3 and 12 months. As the time after surgery increased, the neourothelium became less thick, signs of inflammatory response disappeare d, and the orientation of collagen fibrils and smooth muscle fascicles rese mbled that of a normal urethra. The implants displayed abundant vasculariza tion, and the luminal surface started to become irregular. Acellular blood vessels may represent a promising approach to urethral defect therapy for d ifferent reasons: (a) unlimited availability, (b) readily obtainable in dif ferent lengths and gauges, (c) the potential for being organized as tissue bank, and (d) that just one simple surgical procedure is needed. Neverthele ss, before this technique call be applied in humans, it must be tested in m ore species and animals.