No abstract

Aims The prevalence of urinary dysfunction increases with age, yet therapies are often suboptimal. Incomplete understanding of the linkages between system, organ, and tissue domains across lifespan remains a knowledge gap. If tissue‐level changes drive the aging bladder phenotype, parallel changes should be observed across these domains. In contrast, a lack of inter‐domain correlation across age groups would support the hypothesis that urinary performance is a measure of the physiologic reserve, dependent on centrally‐mediated adaptive mechanisms in the aging system. Methods Male and female mice across four age groups underwent sequential voiding spot assays, pressure/flow cystometry, bladder strip tension studies, histology, and quantitative PCR analyses. The primary objective of this study was to test the impact of age on the cortical, autonomic, tissue functional and structural, and molecular domains, and identify inter‐domain correlations among variables showing significant changes with age within these domains. Results Behavior revealed diminished peripheral voiding and spot size in aged females. Cystometry demonstrated increased postvoid residual and loss of volume sensitivity, but the preservation of voiding contraction power, with almost half of oldest‐old mice failing under cystometric stress. Strip studies revealed no significant differences in adrenergic, cholinergic, or EFS sensitivity. Histology showed increased detrusor and lamina propria thickness, without a change in collagen/muscle ratio. Adrb2 gene expression decreased with age. No consistent inter‐domain correlations were found across age groups. Conclusions Our findings are consistent with a model in which centrally‐mediated adaptive failures to aging stressors are more influential over the aging bladder phenotype than local tissue changes.

A geroscience-informed approach to the increasing prevalence of bladder control problems in older adults requires understanding the impact of aging on dynamic mechanisms that ensure resilience in response to stressors challenging asymptomatic voluntary control over urine storage and voiding. Bladder control is predicated on sensory neural information about bladder volume. Modulation of volume-induced bladder wall tensions by autonomic and mucosal factors controls neural sensitivity to bladder volume. We hypothesized that HCN (hyperpolarization-activated cyclic nucleotide-gated) channels integrate these factors and thereby mediate adrenergic detrusor tension control. Furthermore, loss of HCN expression compromises that integration, and could result in loss of precision of detrusor control. Using a lifespan mouse model, RT-qPCR and pharmacologic studies in pre-tensioned intact and mucosa-denuded bladder strips were made. The dominant hcn1 expression declines with maturation and aging, however aging is also associated with increased variance around mean values. In strips from mature animals, isoproterenol had less effect in denuded muscle strips than in intact strips, and HCN blockade diminished isoproterenol responsiveness. With aging, variances about mean response values significantly increased, paralleling hcn1 expression. Our findings support a role for HCN in providing neuroendocrine/paracrine integration and suggest an association of increased heterogeneity of HCN expression in aging with reductions in response precision to neuroendocrine control. The functional implication is an increased risk of dysfunction of brainstem/bladder regulation of neuronal sensitivity to bladder volume. This supports the clinical model of the aging bladder phenotype as an expression of loss of resilience, and not as emerging bladder pathology with aging.

The urinary bladder functions as a reservoir to store and extrude liquid bodily waste. Significant debate exists as to this tissue's cellular composition and genes associated with their functions. We use a repertoire of cell profiling tools to comprehensively define and spatial resolve cell types. We characterize spatially validated, basal-to-luminal gene expression dynamics within the urothelium, the cellular source of most bladder cancers. We define three distinct populations of fibroblasts that spatially organize from the sub-urothelial layer through to the detrusor muscle, clarifying knowledge around these controversial interstitial cells, and associate increased fibroblasts with aging. We overcome challenges of profiling the detrusor muscle, absence from earlier single cell studies, to report on its transcriptome with many novel and neuronal-like features presumably associated with neuromuscular junctions. Our approach provides a blueprint for tissue atlas construction and the data provides the foundation for future studies of bladder function in health and disease.