CELLULAR SIGNALING IN THE BLADDER

Laurence S. Baskin^1,3, Simon W. Hayward^1,2, Ronald A. Sutherland¹, Michael S. DiSandro¹, Axel A.Thomson² and Gerald R. Cunha^1,2

Department of Urology1, Anatomy2 and Pediatrics3 University of California, San Francisco San Francisco, California, 94143-0738

Received 11/13/97 Accepted 11/25/97

5. BLADDER REPLACEMENT

One of the most exciting areas of bladder research is development of new methods of bladder augmentation which avoid the use of intestinal segments. We have created a model of bladder augmentation in which we use an acellular tissue matrix to elicit regeneration of bladder tissue (figure 3) (11). In this model, the dome of the bladder is excised (again, this was first performed in the rodent model) and acellular tissue matrix made from either the bladder or the stomach is sutured to the surgical defect. The acellular matrix is prepared by incubating the bladders or stomachs of adult rats in distilled water for one hour to lyses the cells and to release intracellular contents. Tissues are then suspended in 40 ml of 40% sodium deoxycholate (Sigma Chemical Company, St. Louis, MI), for 2 to 4 hours, followed by treatment with 2,000 Kunitz units of Deoxyribonuclease I (Sigma Chemical Company) in 1 M sodium chloride solution for 1 to 2 hours. This process is repeated 1 to 3 times to extract all cellular material. Histologic confirmation shows an absence of cells. The preparation of the acellular matrix is designed to avoid complete removal of potentially important growth factors, as well as other extracellular matrix ligands. After suturing the acellular matrix patch in place, animals were sacrificed at serial time points to specifically study the interface between the native bladder and the acellular matrix tissue. Complete re-epithelization with urothelial cells occurred by 4 days and smooth muscle regenerated into the acellular matrix by 2 weeks post-grafting. Interestingly, the smooth muscle grew in juxta-position to the epithelial surface, which over time matured into normal size bundles by 26 weeks post-grafting.

Figure 3. A model of bladder regeneration with an acellular tissue matrix shows that urothelium, smooth muscle and nerves can grow into the tissue matrix most likely under the influence of stromal-epithelial cellular communication. (12) (Used with Permission). Neovascularization was seen by 2 weeks and neural elements from the native bladder formed around the developing bundles of smooth muscle as early as 4 weeks. These animals were able to void and function normally. Careful histologic analysis showed that the acellular tissue matrix did not regenerate into completely normal bladder, but over time smooth muscle bundles did organize into their appropriate position in the periphery of the bladder, and the urothelium itself covered this matrix, presumably under the influence of KGF from tissue injury (6). This model has been very useful for studying the cellular signaling that occurs in the native bladder, especially in relation to potential bladder augmentation and bladder replacement.