The biological behavior of autologous collagen-based extracellular matrix injected into the rabbit bladder wall

Endoscopic techniques are providing a minimally invasive approach to the treatment of vesicoureteral reflux and urinary incontinence. Bovine collagen has been used, but potential degradation over time and sensitivity reactions have limited its usefulness. We evaluate the use of an autologous collagen-based extracellular matrix preparation injected within the rabbit bladder submucosa and compare it to the stability of bovine collagen-injected similarly. Of 28 New Zealand white rabbits, 12 underwent injection of autologous collagen-based extracellular matrix, 12 bovine collagen, and four normal saline sham injections into the anterior bladder submucosa. Twelve collagen specimens were iodinated with iodine 125 ((125)I) paraaminobenzoate reagent. The (125)I-labeled rabbits were monitored with a gamma camera to assess the level of decay of radioactivity over 12 weeks. All animals were killed 12 weeks post-injection. Assessment of radioactivity showed minimal difference in radioisotope labeling between the autologous and bovine collagen (total counts and decay kinetics). Compared to bovine collagen, the autologous collagen- based extracellular matrix implants histologically showed increased fibroblastic and vascular infiltration focally. The most significant histologic difference was the marked inflammatory response associated with the bovine collagen implants. These data suggest that in the short term, autologous and bovine collagen appear to have similar stability. The response to autologous collagen-based extracellular matrix may increase longevity of the implant, primarily by reducing immunologic rejection and improving biocompatibility within the host tissue. Further long-term studies are necessary to assess the long-term stability of autologous collagen-based extracellular matrix. Neurourol. Urodynam. 18:487-495, 1999.