CULTURED UROTHELIUM IN SHEEP BLADDER AUGMENTATION

In search of alternatives for urothelial-lined augmentation or reconst ruction of the urinary bladder, this study combined the application of seromuscular gastrointestinal (GI) segments with the use of in-vitro cultured, autologous urothelial cells in a sheep model. A cell culture system was set up for establishment and expansion of urothelial cells out of small biopsies from bladder mucosa. A biodegradable carrier ma de of lactidcaprolactoncopolymer was introduced, allowing upside-down transplantation of cell cultures in vivo. Bladder mucosal biopsies wer e taken from 14 sheep (mean weight 13.3 kg) with an average yield of 3 .5x10(5) viable cells/cm(2) after trypsinization. Primary low-density cultures grew to confluence within 5-7 days. Secondary cultures were e stablished on the biodegradable film and were available a week later. They were transplanted onto demucosalized segments of stomach (group 1 ) or colon (group 2) in 5 animals each, followed by bladder incorporat ion in clam fashion. The earliest specimens, demonstrating survival an d some proliferation of the cultured urothelium in both groups, were o btained 13 days postoperatively. To exclude urothelial regrowth, a tem porary pouch grafted with cultured urothelium was created in 2 more sh eep of each group. Biopsies were taken after 2 and 3 weeks, respective ly, when the reopened pouch was integrated into the bladder (delayed a ugmentation). In these pouches, adherence and proliferation of urothel ial cells could not be demonstrated. Limited radiologic and urodynamic investigations after 5-6-month follow-up revealed good shape, capacit y, and compliance of the primarily augmented bladders only. The result s indicate that urothelial cell cultures can be established and applie d in vivo. Despite upside-down transplantation, they are able to survi ve on seromuscular segments in an autologous setting. The bladder envi ronment is necessary to promote complete covering of the seromuscular segments. Based on our histologic findings, the share of both resident bladder urothelium and transplanted cells in the formation of the fin al urothelial lining remains uncertain. Morphologic and urodynamic fol low-up data indicate that this process can be accelerated by the trans planted urothelial cells, reducing fibrotic changes of the GI segments . The functional quality of the augmented bladder seemed to improve co mpared to results after seromuscular augmentation alone.