Expression of P2X3 purinoceptors in suburothelial myofibroblasts of the normal human urinary bladder

Abstract

To investigate the possible localization of P2X3 receptors on suburothelial myofibroblasts and the structural relationship between these cells and sensory nerves in the human bladder. Bladder specimens were obtained from 17 patients. Cryosections were prepared for immunofluorescent investigations using various antibodies, including cytoskeletal marker vimentin, alpha-smooth muscle actin (alpha-SM actin), desmin, P2X3 purinoceptors, afferent nerve fibers marker calcitonin gene related peptide, substance P and Griffonia simplicifolia isolectin B4. Double-labeling was employed to determine the spatial relationship of myofibroblasts with P2X3 purinoceptors and afferent fibers. In the bladder suburothelium, there was a network of fusiform vimentin-positive cells with branching processes. Almost all of these vimentin-positive myofibroblasts showed immunoreactivity for alpha-SM actin. P2X3 receptors' immunoreactivity was not distributed on any of the suburothelial afferent nerve fibers including calcitonin gene related peptide, substance P and isolectin B4-containing nerves in the bladder. However, abundant P2X3 receptors localized on the small soma and branching processes of suburothelial myofibroblasts. Furthermore, a large number of suburothelial afferent fibers were found to contact closely with myofibroblasts, or intermingle with each other. In the suburothelium of the human bladder, there was a layer of vimentin-positive myofibroblasts. Almost all vimentin-positive myofibroblasts showed double labeling for alpha-SM actin. These cells expressed P2X3 receptors. Suburothelial myofibroblasts may be intermediate in processing adenosine triphosphate-mediated sensory activation.