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

Objectives:   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.
Methods:   Bladder specimens were obtained from 17 patients. Cryosections were prepared for immunofluorescent investigations using various antibodies, including cytoskeletal marker vimentin, α-smooth muscle actin (α-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.
Results:   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 α-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.
Conclusions:   In the suburothelium of the human bladder, there was a layer of vimentin-positive myofibroblasts. Almost all vimentin-positive myofibroblasts showed double labeling for α-SM actin. These cells expressed P2X3 receptors. Suburothelial myofibroblasts may be intermediate in processing adenosine triphosphate-mediated sensory activation.