© 2 0 0 4 B J U I N T E R N A T I O N A L | 9 3 , 6 0 9 – 6 1 6 | doi:10.1111/j.1464-410X.2004.04675.x 609 Original Article SURGICAL MODEL OF COMPOSITE CYSTOPLASTY M. FRASER et al. A surgical model of composite cystoplasty with cultured urothelial cells: a controlled study of gross outcome and urothelial phenotype M. FRASER*†¶, D.F.M. THOMAS*, E. PITT†, P. HARNDEN‡, L.K. TREJDOSIEWICZ† and J. SOUTHGATE¶ *Departments of Paediatric Urology and ‡Pathology and †Cancer Research UK Clinical Centre, St. James’s University Hospital, Leeds and ¶Jack Birch Unit of Molecular Carcinogenesis, Department of Biology, University of York, UK Accepted for publication 31 October 2003 Conventional colocystoplasty, de- epithelialized colocystoplasty and sham operations were carried out in six control animals. After killing the animals at ª 90 days the bladders were removed for examination and immunohistochemical analysis, using a panel of antibodies against cytokeratins and urothelial differentiation-associated antigens. RESULTS Macroscopically, the bladders augmented with composite segments derived from uterine muscle had no evidence of shrinkage or contracture. Histological analysis showed that in four of five composite uterocystoplasties, the neo-urothelium was stratified and had a transitional morphology, although in some areas coverage was incomplete. Immunohistochemical analysis showed evidence of squamous differentiation in both native and augmented segments. All composite and de-epithelialized colonic segments showed significant contraction with poor urothelial coverage, reflecting the unsuitability of the thin-walled porcine colon for de-epithelialization. CONCLUSIONS The functional and macroscopic outcome of bladder augmentation with a composite derived from cultured urothelium and de- epithelialized smooth muscle of uterine origin endorses the feasibility of composite cystoplasty. KEYWORDS bladder, urothelium, tissue engineering, reconstruction, enterocystoplasty, surgical model OBJECTIVES To study the outcome of composite cystoplasty using cultured urothelial cells combined with de-epithelialized colon or uterus in a porcine surgical model, using appropriate controls, and to characterize the neo-epithelium created by composite cystoplasty. MATERIALS AND METHODS Urothelial cells were isolated and propagated in vitro from open bladder biopsies taken from nine female minipigs. Cohesive sheets of confluent urothelial cells were transferred to polyglactin carrier meshes and sutured to de- epithelialized autologous colon in four animals and de-epithelialized autologous uterus in five. These composite segments were then used for augmentation cystoplasty. INTRODUCTION The use of intestinal segments for bladder augmentation or substitution (enterocystoplasty) has been a major advance in the surgical management of congenital and acquired abnormalities of the bladder. However, the benefits of enterocystoplasty are offset by well-documented, relatively common and potentially serious complications, including mucus production, stone formation, chronic low-grade infection and metabolic disturbance (reviewed in [1]). These problems are attributable to the lining of the intestine, an absorptive, mucus- secreting epithelium that is not adapted to prolonged contact with urine. The ideal material for bladder reconstruction would combine the compliance afforded by smooth muscle with the non-absorptive barrier lining of normal urothelium. Despite extensive research into alternatives to conventional enterocystoplasty very few techniques have been translated into clinical practice. Ureterocystoplasty achieves the goal of a urothelium-lined augmentation but is effectively confined to a few patients with a combination of gross ureteric dilatation and an ipsilateral nonfunctioning kidney [2]. Seromuscular enterocystoplasty coupled with autoaugmentation also creates a urothelium-lined augmentation [3,4]. However, in clinical practice the role of this technique may be limited by the difficulty of detrusor myectomy in a contracted or heavily trabeculated neuropathic bladder, and by the limited potential to increase the capacity of small bladders by autoaugmentation. We previously reported the development of reliable cell-culture systems capable of generating large areas of normal human urothelium [5–7], with the aim of developing a tissue-engineering approach to bladder reconstruction. Other groups have described tissue-engineering approaches for the development of whole-bladder replacements [8] or biomaterials for bladder wall substitution [9,10]. However, as the complications of enterocystoplasty are largely attributable to the epithelium rather than the intestinal smooth muscle, we favoured the concept of ‘composite’ cystoplasty, in which autologous urothelium is cultured in vitro and combined with de-epithelialized bowel at the time of reconstruction [11,12]. This concept has been endorsed by studies in which we showed that in vitro-propagated normal human urothelial (NHU) cells can be induced to stratify and differentiate when recombined with a de-epithelialized stroma in organ culture [13].