Functional rat bladder regeneration through xenotransplantation of the bladder acellular matrix graft

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Abstract
Objective: To determine the decreased antigenicity of the bladder acellular matrix graft (BAMG) through xenotransplantation and to assess the in vivo and in vitro functional properties of the rat urinary bladder thus regenerated.Materials and methods: After partial cystectomy (>50%), BAMGs prepared from hamster, rabbit and dog urinary bladders were grafted to male and female Sprague‐Dawley rats; 10 control rats underwent partial cystectomy only. Urinary storage and voiding function were monitored in 15 animals using a specially designed ‘micturition cage’ and cystometry. After 4 months, organ‐bath studies and histological techniques were used to evaluate bladder regeneration in vitro in the grafted animals.Results: Clinically relevant antigenicity was not evident; no animal died from rejection and all bladder wall components regenerated in all BAMG xenografts. However, the degree and quality of regeneration varied. Muscularization, peak pressure, and bladder capacity were higher in the hamster BAMG‐grafted animals, whereas in vitro contractility and compliance were best in the dog BAMG‐regenerated bladders. All grafted bladders had significantly better capacity and compliance than the autoregenerated bladders after partial cystectomy alone.Conclusions: The present in vivo and in vitro studies show that BAMG‐augmentation cystoplasty can lead to morphological and functional regeneration of the rat bladder, preserving its low‐pressure reservoir function. Because BAMG‐regenerated bladders show functional innervation that is similar to normal bladders, they can work in coordination with the host bladder components, thus generating adequate intravesical pressure to produce sustained voiding. The decreased antigenicity makes heterologous BAMG transplants feasible without immunosuppression.