Mechanisms of Disease: involvement of the urothelium in bladder dysfunction

Studies have challenged the traditional view that the urothelium is a passive barrier to solutes and ions, and have demonstrated its sensory role in bladder function. The authors of this Review discuss the studies that have examined sensory mechanisms in the urothelium and the role these mechanisms have in the pathophysiology of bladder dysfunction. Although the urinary bladder urothelium has classically been thought of as a passive barrier to ions and solutes, a number of novel properties have been recently attributed to urothelial cells. Studies have revealed that the urothelium is involved in sensory mechanisms (i.e. the ability to express a number of sensor molecules or respond to thermal, mechanical and chemical stimuli) and can release chemical mediators. Localization of afferent nerves next to the urothelium suggests that urothelial cells could be targets for neurotransmitters released from bladder nerves or that chemicals released by urothelial cells could alter afferent nerve excitability. Taken together, these and other findings highlighted in this article suggest a sensory function for the urothelium. Elucidation of mechanisms that influence urothelial function might provide insights into the pathology of bladder dysfunction.