How is Fullness Sensed in the Urinary Bladder?

总结 在正常的日常生活中，膀胱充盈的感觉被传递到中枢神经系统， 排尿不太频繁，尿潴留不太痛苦。人们的注意力集中在 然而，试图治疗膀胱功能障碍，以了解下尿路的任何疾病， 必须解决一个基本的生理问题，即：膀胱充盈是如何感觉到的？ 令人惊讶的是，感知膀胱充盈的基本生理机制仍然难以捉摸。探索这个 一个根本性的问题将是目前提案的重点，这将加深我们对这一点的理解 过程，提供了重要的见解，涉及翻译膀胱充盈的基本机制 转化为传入信息我们提出了新的总体概念，即机械性能的局部变化 膀胱壁在充盈过程中的收缩是驱动感觉流出的原因。重要的是，压力本身并不 驱动传入神经活动。相反，膀胱壁的局部变形是传入神经的刺激。 神经活动在充盈过程中，逼尿肌平滑肌（DSM）的局部兴奋在空间上扩散，引起小的收缩。 膀胱壁的短暂收缩，称为微动。微动导致角变形， 膀胱壁张力的局部变化。我们认为正是这种局部的血管壁张力变化 触发传入神经活动以感知膀胱充盈。这个提议的核心是确定 在膀胱中被感知，而不推测参与信号传导的细胞类型（尿路上皮细胞， 间质细胞、成纤维细胞等）。该项目采用了许多新的技术和方法，如我们的 五平面反射图像宏观平台，能够实时监控整个系统的微动 膀胱的表面。我们开发了尖端的成像方法和信号处理 算法来量化膀胱运动和Ca 2+信号动力。在目标1中，我们将确定 膀胱充盈期间DSM的局部激发。我们将使用成像技术对小鼠进行基因表达， 编码的Ca ~（2+）指示剂研究DSM的兴奋性如何影响Ca ~（2+）信号的空间分布。目的 图2探索了激励与角失真的速率/程度之间的时空关系，以及 充盈期间的传入神经活动。我们将同时记录DSM Ca 2+活性、膀胱压力 和传入神经活动。最后，在目标3中，我们将研究传入神经机械感知的基础 在膀胱和Piezo 1和Piezo 2拉伸敏感阳离子通道的作用。重要的是，我们将 在体内表征Piezo 2敲除小鼠的膀胱功能。通过这个项目的完成，我们将获得 对充盈过程中的物理力被泌尿系统感知的机制的基本见解 膀胱一旦我们对这些过程有了充分的了解，我们将更适合建模，研究和 治疗膀胱功能障碍。

SUMMARY In normal day-to-day life, the sense of urinary bladder fullness is conveyed to the central nervous system such that voiding of urine is not too frequent, and retaining urine is not too painful. Much attention has focused on attempting to treat urinary bladder dysfunctions however, to understand any disorder of the lower urinary tract an essential physiological question must be addressed, and that is: How is bladder fullness sensed? Amazingly, the basic physiological mechanisms for sensing bladder fullness remain elusive. Exploring this fundamental question will be the focus of the current proposal, which should deepen our understanding of this process, providing important insights into the fundamental mechanisms involved in translating bladder fullness into afferent information. We propose the novel overarching concept that local changes in mechanical properties of the urinary bladder wall during filling are what drives sensory outflow. Importantly, pressure, per se, does not drive afferent nerve activity. Rather, it is the local deformation of the bladder wall that is the stimulus for afferent nerve activity. During filling, local excitation of detrusor smooth muscle (DSM) spreads spatially to cause small transient contractions of the bladder wall, called micromotions. Micromotions lead to angular distortions and localized changes in wall tension of the bladder wall. It is this localized change in wall tension that we believe triggers afferent nerve activity to sense bladder filling. This proposal gets at the heart of determining how fullness is sensed in the urinary bladder, without speculating about cell types involved in signaling (urothelial cells, interstitial cells, fibroblasts, etc). This project utilizes numerous novel techniques and approaches, such as our pentaplanar reflected image macroscopy platform that enables real-time monitoring of micromotions on the entire surface of the bladder. We have devleoped cutting edge imaging methodologies and signal processing algorithms to quantify bladder motility and Ca2+ signaling dynamcis. In Aim 1, we will determine the basis for local excitation of DSM during bladder filling. We will use imaging techniques on mice expessing genetically encoded Ca2+ indicators to study how the excitatiliby of the DSM affects the spatial spread of Ca2+ signals. Aim 2 explores spatial-temporal relationships between excitation and the rate/extent of angular distortions, and afferent nerve activity during filling. We will use simultaneous recordings of DSM Ca2+ activity, bladder pressure and afferent nerve activity. Finally, in Aim 3, we will investigate the basis for mechano-sensing by afferent nerves in the urinary bladder and the role of Piezo1 and Piezo2 stretch-sensitive cation channels. Importantly, we will characterize bladder function in Piezo2 knockout mice in vivo. Through completion of this project, we will gain fundamental insights into the mechanisms whereby physical forces during filling are sensed by the urinary bladder. Once we gain a full understanding of these processeses, we will be better suited to model, study, and treat bladder dysfunctions.