How is Fullness Sensed in the Urinary Bladder?

摘要 在正常的日常生活中，膀胱充满的感觉被传递到中枢神经系统 排尿不会太频繁，保留尿液也不会太痛。很多注意力都集中在 尝试治疗膀胱功能障碍，但要了解任何下尿路疾病 必须解决一个基本的生理学问题，那就是：如何感觉到膀胱充满？ 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。探索这一点 根本问题将是当前提案的重点，这将加深我们对此的理解 过程，为转化膀胱充盈的基本机制提供了重要的见解 转化为传入信息。我们提出了力学性能局部变化这一新的总体概念 充盈过程中膀胱壁的收缩是感官流出的驱动力。重要的是，压力本身并不能 驱动传入神经活动。相反，是膀胱壁的局部变形刺激了传入 神经活动。在充盈过程中，逼尿肌的局部兴奋在空间上扩散，导致小的 膀胱壁的一过性收缩，称为微动。微动会导致角度扭曲和 膀胱壁张力的局限性变化。我们认为，正是这种局部的墙体张力变化 触发传入神经活动来感觉膀胱的充盈。这项提议是决定丰满程度的核心 在膀胱中被感知，而不推测参与信号传递的细胞类型(尿路上皮细胞， 间质细胞、成纤维细胞等)。这个项目利用了许多新的技术和方法，例如我们的 五平面反射图像宏观平台，实现对整体微动的实时监控 膀胱表面。我们开发了尖端的成像方法和信号处理 量化膀胱运动和钙信号动力学的算法。在目标1中，我们将确定 DSM在膀胱充盈过程中的局部兴奋。我们将在小鼠身上使用成像技术来表达基因 编码了钙离子指示器，以研究DSM的兴奋性如何影响钙信号的空间扩散。目标 2探讨了激发和角度扭曲的速率/程度之间的时空关系，以及 充盈过程中的传入神经活动。我们将使用同步记录的DSM钙离子活动，膀胱压力 以及传入神经活动。最后，在目标3中，我们将研究传入神经机械感觉的基础。 以及在膀胱和Piezo1和Piezo2拉伸敏感阳离子通道中的作用。重要的是，我们会 体内研究Piezo2基因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量通过尿液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，我们就更适合建模、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.