Mechanisms of epithelial renewal in normal and diseased urinary bladder

膀胱内有移行的尿路上皮，翻转缓慢，但有很大的诱导再生能力。尿路上皮干细胞(USC)的利基由基础干细胞和底层间充质组成，为更新提供动力。然而，对USC的分子特征或管理USC在损伤或疾病中的生态位适应的调控机制知之甚少。该研究计划的长期目标是确定控制正常静止的尿路上皮干细胞(USCs)快速、损伤诱导的再生反应的基因、途径和分子，并应用我们所了解的非正常机制来阐明尿路上皮肿瘤异常的疾病过程(例如间质性膀胱炎/疼痛膀胱综合征、膀胱癌)。我们已经建立并研究了两种损伤模型，一种是由尿路感染(UTIs)的主要病原体--致尿性大肠杆菌(UPEC)感染引起的，另一种是由一种化学物质--鱼精蛋白硫酸盐(PS)引起的。我们发现，急性UPEC感染导致膀胱表层细胞迅速脱落，显著的急性炎症反应，以及南加州大学利基细胞有丝分裂活动的显著增加。另一方面，PS诱导的化学损伤会导致细胞塌陷，但不会引起炎症，也不会对USC产生反应。我们发现，感染性损伤后的上皮更新是由骨形态发生蛋白(BMP)信号通路介导的。诱导重组酶介导的Bmp4受体Bmpr1a在膀胱上皮细胞中的可诱导消融导致其不能维持USC的增殖或在感染后再生终末分化的表浅细胞。此外，长期感染导致上皮间充质边界的破坏和准上皮向间充质转变的特征。该应用的具体目的是阐明Bmp4信号缺陷小鼠对急性和长期UPEC感染的尿路上皮反应的机制，并阐明尿路上皮对不同形式损伤的反应的细胞和分子基础。

The urinary bladder is lined by a transitional urothelium with nonnally slow tumover but substantial injuiyinducible regenerative capacity. Tlie urothelial stem cell (USC) niche, comprising basal stem cells and underlying mesenchyme, fuels the renewal. However, little is known about the molecular features ofthe USCs or the regulatory mechanisms goveming USC niche adaptation in injury or disease. The long term objectives of the research program is to identify the genes, pathways and molecules that govem the rapid, injuryinduced regenerative response of normally quiescent urothelial stem cells (USCs) and to apply what we leam about the nonnal mechanisms to shed light on disease processes with abnormal urothelial tumover (e.g., interstitial cystitis/painful bladder syndrome, bladder cancer). We have developed and study two models of injury, one caused by infection by uropathogenic E. coli (UPEC), the primary causative agent of urinary tract infections (UTIs), and the other by a chemical, protamine sulfate (PS). We show that acute UPEC infection results ui rapid sloughing of superficial cells lining the bladder, marked acute inflammatory response, and a substantial spike in mitotic activity of the USC niche. On the other hand, chemical injury induced by PS causes sloughing but no inflammation and no USC response. We find that epithelial renewal following infectious injury is mediated by the Bone moiphogenetic protein (Bmp) signaling pathway. Inducible cre-recombinase-mediated ablation of the Bmp4 receptor Bmprla in the bladder epithelium resulted in its inability to sustain USC proliferation or regenerate terminally differentiated superficial cells in response to infection. Furthermore, long term infection led to a disruption of epitheUalmesenchymal boundaries and features of qjithelial-to-mesenchymal transition. The specific aims of this application are to elucidate the mechanism tmderlying urothelial response to acute and long term UPEC infection in Bmp4- signaling deficient mice and to elucidate the cellular and molecular underpinnings ofthe urothelial responses to different forms of injury.