The biological behavior of autologous collagen injected into the rabbit bladder

Growing interest in the endoscopic treatment of vesicoureteral reflux and urinary incontinence has led to the development of safe reliable techniques that use an injectable bulking agent. A variety of injectable materials has been studied, such as polytetrafluoroethylene, fat and bovine collagen. We evaluated autologous collagen extracted from the dermis of skin for potential use in the urinary tract. Therefore, an animal model was developed to study the biological behavior of autologous collagen within the bladder. Collagen was extracted from the skin of rabbits and radiolabeled with 125iodine. An aliquot of radiolabeled autologous collagen was injected submucosally in the bladder. The animals were monitored weekly under a gamma camera. The decay of the radiolabeled collagen was recorded during 50 days. The animals were then sacrificed and the bladder wall at the site of injection was studied histologically and on electron microscopy. Decay of the injected collagen within the urinary tract was similar to control material, indicative of good stability within the bladder. A mild inflammatory response with fibroblastic and vascular invasion of the collagen implant was observed. These preliminary data suggest that autologous collagen injected endoscopically can provide a safe reliable bulking material that could be used to treat urinary incontinence and lower grades of vesicoureteral reflux in children.