Sensory Receptors are Found in a Non‐sensory Organ: The Bladder

Abstract

Recent research has found that “sensory” receptors (including olfactory receptors (Olfr), taste receptors (Tas), and opsins (Opn)) play functional roles throughout the body. However, the expression of these receptors has not yet been carefully examined in the bladder. In this study, we utilized customized Taqman low density gene array cards to perform quantitative PCR and identify novel sensory receptors in mouse bladder tissue. We extracted RNA from murine bladder (2 male, 2 female), and then screened for the presence of sensory receptors using custom Taqman arrays which included probesets for 43 ORs, 35 bitter TRs, 3 TRs for umami/sweet, 5 opsins, and 7 G‐proteins and/or accessory proteins associated with sensory signaling pathways, as well as a Gapdh control. Using these arrays, we found the expression of 30 sensory transcripts in all male and female bladder samples, with 10 receptors being relatively well‐expressed (Ct values<~30). These moderately expressed receptors included 2 opsins (Opn1sw, Opn3), 3 ORs (Olfr558, Olfr99, Olfr78), and 5 TRs (Tas1r3,Tas2r143, Tas2r135, Tas2r108, Tas2r126. We did not note any significant sex differences, and the top hit (Opn1sw) was the same for all four arrays. We have localized these top receptors within the bladder using two different methods: quantitative PCR on microdissected bladder tissue, and RNAscope fluorescent imaging. Although some receptors have higher relative expression in either urothelium or muscle, all of the receptors are expressed in both of these cell types. Notably, two of the ORs found in the bladder (Olfr78, Olfr558) are known to respond to bacterial metabolites, which may be relevant in the setting of cystitis/urinary tract infections (UTIs). We then screened by qRT‐PCR for a subset of five of these receptors as well as two control receptors (not detected in bladder in the initial screen) in various tissues: brain, colon, eye, heart, kidney, skeletal muscle, and tongue. We found that all five of the receptors of interest were expressed in at least one tissue in addition to bladder, with varying patterns of expression for each. Further investigation could help us better understand why these receptors are expressed in these tissues. Moreover, determining the role of these novel sensory receptors in the bladder has the potential to enhance our understanding of bladder function, and may lead to novel treatments for conditions such as cystitis/UTIs.