Bladder Tissue Regeneration with a Collagen-Based Biomatrix in a Model for Bladder Exstrophy Compared to Regeneration in Normal Bladder

Abstract

Purpose Patients with bladder exstrophy may need a bladder augmentation to improve function. Tissue engineering aims to develop alternatives for the current technique in which intestinal tissue is used. In this study we compared the regeneration of bladder tissue with a collagen-based biomatrix in a sheep model for bladder exstrophy with bladder tissue regeneration in normal bladder. Material and Methods Biomatrices of bovine collagen type I were prepared by subsequent freezing, lyophilisation and crosslinking. In 12 fetal sheep a bladder exstrophy was surgically created at 79 days’ gestation. Lambs were born at full term (140 days' gestation) by normal delivery. After one week the bladder lesion was reconstructed with a collagen biomatrix (group 1). In 10 normal newborn lambs the bladder was opened one week after birth, and closed with a collagen biomatrix (group 2). Functional (cystogram and urodynamic) and histological studies were performed to evaluate the bladders at 1 or 6 months after surgery. Results Survival rate was 58% in group 1 and 90% in group 2. In all animals the cystograms were normal, except for low grade reflux in some lambs of group 1. Urodynamic studies at 6 months showed lower compliance in group 1 (2.0 ± 1.4 versus 4.0 ± 2.7 ml/cmH2O). Histological evaluation at 1 month revealed small areas of squamous differentiation of regenerated urothelium in group 1. At 6 months in both groups normal urothelial lining was present, extracellular matrix was comparable, and slight smooth muscle cell ingrowth was seen. Conclusions This study indicates that bladder regeneration with a collagen-based biomatrix in diseased bladders results in functional bladder tissue with comparable characteristics as normal regenerated bladder tissue. This collagen-based biomatrix might be useful in reconstruction of bladder defects.