Bladder augmentation with acellular dermal biomatrix in a diseased animal model

Purpose: The use of bowel for bladder augmentation is associated with many complications. We have reported that acellular dermal biomatrix can be used successfully for directing the regeneration of each key bladder wall element in healthy domestic pigs. Before proposing that this material should be used in the human setting a final set of experiments using this scaffold to replace diseased bladder wall is necessary. We determined if acellular dermal biomatrix can be used to replace diseased bladder wall. We compared our findings to our previous results. Materials and Methods: Six domestic male pigs underwent urethral ligation and suprapubic tube placement. Five female pigs served as controls for bladder dynamics. Machined resistance valves of 5 and 10 cm H2O pressure were placed into the lumen of the cystostomy catheter for a mean of 3.3 weeks (range 3 to 4). Obstruction was then relieved and partial cystectomy was performed, followed by augmentation with a 4 X 4 cm segment of acellular dermal biomatrix of the markedly thickened and poorly compliant bladder. Animals were sacrificed 3 months following augmentation. Standard urodynamic studies were performed. Contractility and compliance were measured in freshly isolated regenerated and native bladder tissues. Histological evaluation was performed on hematoxylin and eosin, and Masson's trichrome stained sections. Results: Bladder compliance was markedly decreased after 3.3 weeks of obstruction. Mean compliance +/- SEM before obstruction was 16.28 +/- 9.21 cm H2O. After 3.3 weeks of obstruction average compliance was 4.13 +/- 0.98 cm H2O. One pig died 2 weeks following augmentation due to graft separation and sepsis. Gross examination of augmented bladders revealed the complete replacement of acellular dermal biomatrix with bladder tissue. Histological evaluation revealed extensive fibrosis with small islands of poorly organized muscle in contrast to the complete regeneration of mucosa, smooth muscle and serosa seen in augmentations previously performed in healthy animal bladders. Maximum contractile tension of the patch tissue was not different than that in the native tissue from the obstructed hypertrophied bladder but it was only approximately 10% of the tension produced by healthy tissue from nonobstructed augmented bladders. The obstructed bladder patch and native tissue was approximately 14 times stiffer than healthy bladder tissue. Conclusions: While augmentation of healthy porcine bladder with acellular dermal biomatrix results in excellent functional bladder tissue regeneration, similar experiments in a porcine model of obstructed bladder disease failed to show favorable results. Therefore, acellular dermal biomatrix cannot be recommended at this time for human bladder dysfunction. Results support the contention that matrices designed for human bladder augmentation should be tested in a disease animal model before recommending them for human bladder dysfunction.