The urethra is considered a passive conduit for urine. Here, we reveal a surprising multicellular signaling pathway guiding the urethra’s dynamic response to an invading pathogen. Using a genetic approach in female mice, we deposited uropathogenic Escherichia coli into the distal urethra to establish a model of ascending urinary tract infection that progresses to the bladder within 4 h. We show that urethral neuroendocrine cells (UNECs), and the serotonin they synthesize, protect the bladder from bacterial colonization. We tested the hypothesis that serotonin initiates urethral contraction to expel ascending bacteria. We identified transient receptor potential cation channel subfamily A member 1, a noncanonical lipopolysaccharide receptor, in human and mouse UNECs and localized the serotonin receptors (HTR) 2B and 3, as well as the calcium-activated chloride channel anoctamin 1 (ANO1) to the pacemaker cells of the human and mouse urethra, the interstitial cells of Cajal (ICCs). HTR2B or ANO1 activation is sufficient for urethral contraction and is required for serotonin-induced mouse urethral contraction. Our results support the hypothesis that the urethra actively surveils its environment and responds to an ascending pathogen by evoking UNECs and ICC to induce urethral contraction and pathogen expulsion.

Most mechanosensitive afferents do not express markers of peptidergic nociceptors and therefore remain largely overlooked in studies of bladder dysfunction and disease. TrkB-mediated labeling of putative Aδ mechanoreceptors emerged as a valuable tool for the study of neuropeptide-negative bladder afferents with a confirmed role in bladder mechanosensation. Targeted neuronal ablation likewise validated an intersectional genetic strategy that can now directly test the role of TrkB mechanoreceptors in bladder physiology and disease.

Polychlorinated biphenyls (PCBs) are persistent organic pollutants linked to deleterious health outcomes, including voiding dysfunction in developmentally exposed mice. Changes in prostate volume and/or extracellular matrix composition are associated with voiding dysfunction in men and animal models. Whether PCB-induced changes in voiding function in male mice occur in part via alterations to the prostate or an alternate mechanism is unclear. Therefore, we tested whether developmental exposure to the MARBLES PCB mixture altered prostate morphology in young adult offspring. C57Bl/6J female mice were dosed daily with the MARBLES PCB mixture at 0, 0.1, 1 or 6 mg/kg/d for two weeks prior to mating and through gestation and lactation, offspring were collected at 6 weeks of age. Ventral prostate mass was decreased in the 1 mg/kg/d PCB group compared to other PCB groups. There were no PCB-induced changes in prostate smooth muscle thickness, apoptosis, proliferation, or testes mass. PCBs impacted the prostate extracellular matrix; anterior prostate collagen density was decreased in the 1 mg/kg/d PCB group compared to all other groups. Normalized bladder volume was increased in male and female offspring in the 6 mg/kg/d PCB group compared to control. No change in water consumption, bladder mass or bladder smooth muscle thickness accompanied changes in bladder volume. Urine and serum creatinine concentrations were elevated but only in male mice. Together, these results suggest that developmental exposure to PCBs can influence prostate wet weight and prostate/bladder morphology, but PCBs do not promote prostate enlargement. Whether these changes persist throughout adult life and how they contribute to voiding function in animal models and humans is of future interest.

Many women suffer from symptoms associated with dysfunction of the lower urinary tract, including incontinence and overactive bladder, especially during pregnancy. While causes are likely multifactorial, environmental factors, such as exposure to polychlorinated biphenyls (PCBs), have been shown to alter voiding in adult female mice. However, the distribution of PCBs and their metabolites to the bladder and urine, as well as their effects on bladder drug-metabolizing enzyme expression after dosing with PCB mixtures, remains largely unexplored. Female C57BL/6J mice were exposed to MARBLES PCB mixture (0, 0.1, 1, and 6 mg/kg/d) through gestation and lactation, and post-weaning bladder, urine, blood, adipose, and liver were collected for measurement of PCBs and OH-PCBs, and for abundance of cytochrome P450 ( Cyp ) transcripts in liver and bladder. PCBs and OH-PCBs were detected in all tissues in a dose-dependent manner. Bladder, adipose, and liver retained parent PCBs while OH-PCBs were predominant in urine and blood. Cyp1a2 mRNA abundance was elevated in the liver of the high dose PCB group versus the vehicle, and the same trend was observed in the bladder. These results define the signatures of PCBs and OH-PCBs in the bladders and urine of post-weaning dams exposed to the MARBLES mixture of PCBs and provide a reference for comparison with accumulation in more commonly studied tissues. Our results also provide new insights into the regulation of Cyp1a2 in the liver and bladder, changes that may play a role in how environmental exposures in adulthood alter voiding function.

SUMMARY: Aging is accompanied by profound changes in bladder function, leading to increased urinary frequency and incontinence that impair quality of life in humans and are recapitulated in mouse models. Bladder filling and emptying rely on precise mechanosensory feedback, yet how aging alters this sensory control remains unclear. PIEZO ion channels convert mechanical forces into cellular signals essential for bladder fullness sensation. Using inducible smooth-muscle specific Piezo1 deletion, we find that loss of Piezo1 attenuates aging-related bladder dysfunction. Dietary enrichment with margaric acid, a membrane-active fatty acid previously shown to inhibit PIEZO channels, reduced urinary dysfunction in aged mice. In humans, genotype–phenotype analyses reveal an association between a PIEZO1 gain-of-function variant and early-onset neuromuscular bladder dysfunction. Together, these findings define a smooth-muscle, PIEZO1-mediated mechanosensory basis for aging-related bladder dysfunction and introduce a non-invasive strategy for targeting PIEZO channels in vivo .

This study identifies disrupted Hh signaling as a key determinant of female bladder and urethral contractility, providing new insights into molecular mechanisms maintaining continence. We observe impaired contractile responses to multiple stimuli, including urethral response to serotonin. In addition, we identify ectopic expression of uroplakin IIIa in urethra of Gli mutant mice, arising after prenatal development. By reducing—but not completely ablating—Hh signaling, we elucidate essential roles of this pathway in determining continence.