Extracellular matrix and integrin composition of the normal bladder wall

We performed an immunohistochemistry study of the normal human bladder so as to understand the interactions of extracellular matrix (ECM) components and the integrins of cell adhesion that accommodate the volume changes and maintain an impermeable barrier to reabsorption of urine in the bladder. The normal human urothelial cell and/or its plasma membrane contained integrins alpha 3, alpha V, beta 1, and beta 4 but did not contain integrin beta 3. The urothelial basement membrane (UBM) contained collagen type IV and laminin. Fibronectin and integrins alpha 3 and beta 4 were found in or near the UBM area, with types I and III collagen and tenascin abutting the area. The patterns of collagen, laminin, tenascin, vitronectin, fobronectin, and the alpha 3, alpha V, beta 1, and beta 3 integrins in the lamina propria, vessels, nerves, and smooth-muscle layers are described. These findings detail the normal anatomical ECM/integrin relationship that provides the cellular basis for bladder-wall relationships responsible for its impermeable state and other functions.