Role Of Piezo Channels In Urothelial Cell Mechanotransduction

During the micturition cycle, the ability to sense and transduce the degree of tension in the wall of the bladder allows the bladder to accommodate to changing urine volumes and to transmit the filling state to the CNS. The urothelium, and in particular the umbrella cells (UC), is proposed to play an important role in mechanotransduction: upon bladder filling, UC sense membrane stretch and transduce it into a number of cellular responses, including exocytosis of subapical discoidal/fusiform vesicles and release of neurotransmitters. The mechanosensor present in the UC that directly responds to membrane stretch is unknown. Piezo channels are a newly discovered family of mechanosensitive channels associated with the physiological responses to pressure, shear stress and tension. In this study, we sought to determine the involvement of Piezo channels in UC mechanosensation. We found that rat UC express both Piezo1 and Piezo2 channels which exhibit different subcellular localizations: Piezo1 is expressed at the apical region and at tight junction sites, whereas Piezo2 is found in the cytosol. Silencing Piezo1 expression by in-situ transduction of rat bladders with adenoviruses encoding Piezo1-shRNA showed a significant decrease in apical exocytosis (61 ± 9 %) compared to control upon ex vivo bladder filling. We also assessed the impact of knocking-down Piezo1 in bladder function by monitoring continuously the intravesical pressure on anesthetized rats previously transduced with either scrambled- or Piezo1-shRNA. We observed that loss of Piezo1 leads to a lower voiding frequency and also affects bladder compliance (defined as ΔV/ΔP during filling). All together, these results show the involvement of Piezo1 in sensing mechanical stretch required for normal bladder function. Future directions involve establishing the role of Piezo2 in rat bladder function as well as detailed characterization of the cascade of events triggered by Piezo1 activation.