Feasibility Study of a Novel Urinary Bladder Bioreactor M. CHAD WALLIS, M.D., 1 HERMAN YEGER, Ph.D., 2 LISA CARTWRIGHT, M.D., 1 ZHIPING SHOU, 2 MILICA RADISIC, Ph.D., 3 JENNIFER HAIG, B.Sc., 2 MOHAMMED SUOUB, M.D., 1 ROULA ANTOON, M.D., 2 and WALID A. FARHAT, M.D. 1,2 ABSTRACT We have devised a bioreactor to simulate normal urinary bladder dynamics. The design permits a cell- seeded scaffold made from a modified porcine acellular matrix to be placed between 2 closed chambers filled with culture medium and be mechanically stimulated in a physiologically relevant manner. Speci- fically designed software increased hydrostatic pressure from 0 to 10 cm of water in a linear fashion in 1 chamber, resulting in mechanical stretch and strain on the scaffold. Pressure was increased over 55 min (filling) and then decreased to 0 over 10 s (voiding). Commercially available small intestinal submucosa scaffolds were used to test the mechanical capabilities of the bioreactor, and pressure waveforms were generated for up to 18 h. Scaffolds were seeded with bladder smooth muscle or urothelial cells and incu- bated in the bioreactor, which generated pressure waveforms for 6 h. Scaffold integrity was preserved as seen through Masson’s trichrome staining. No obvious contamination of the system was noted. Hema- toxylin and eosin staining showed presence of cells after incubation in the bioreactor, and immunohisto- chemistry and real-time reverse transcriptase polymerase chain reaction suggested continued cellular activity. Cellular orientation tended to be perpendicular to the applied pressure. Preliminary results suggest that our bioreactor is a suitable model for simulating normal physiological conditions of bladder cycling in an ex vivo system. INTRODUCTION F UNCTIONS OF THE urinary bladder include storage and emptying of urine while maintaining chemical gradients between the urine and the blood. Cellular and extracellu- lar components contribute to these functions. In terms of cellular components, urothelial cells (UCs) form a multi- layered, specialized epithelium that serves as an effective blood–urine permeability barrier. The smooth muscle cells (SMCs) are responsible for accommodating bladder filling at low pressure (6–10 cm of water (H 2 O)) 1 and contract during emptying. Extracellular components consist of col- lagens, proteoglycans, and glycosaminoglycans; this matrix serves as a reservoir for growth factors and profoundly in- fluences cell growth, differentiation, development, and met- abolic responses. Proteins can be used as phenotypic markers of different bladder SMCs and UCs. Expression changes in contractile and structural proteins are markers of differentiation in SMCs, whereas membrane and intermediate filament pro- teins can denote differentiation in UCs (Table 1). Gastrointestinal tract tissue is the standard available substitute tissue for urinary bladder tissue in the adult and pediatric populations. However, incorporating bowel tis- sue into the urinary tract can lead to infection, stone forma- tion, perforation, carcinogenesis, andmetabolic abnormalities 1 Department of Surgery, Division of Urology, University of Toronto and The Hospital for Sick Children, Toronto, Ontario, Canada. 2 Department of Developmental and Stem Cell Biology, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada. 3 Department of Chemical Engineering and Applied Chemistry, Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada. TISSUE ENGINEERING: Part A Volume 14, Number 3, 2008 # Mary Ann Liebert, Inc. DOI: 10.1089/tea.2006.0398 339