Role of Fgfr2 signaling in bladder injury and regeneration

项目概要/摘要： 环磷酰胺（CPP）诱导的膀胱尿道损伤可导致危及生命的健康状况 包括出血性膀胱炎和膀胱癌。该应用程序的广泛的长期目标是确定 驱动CPP膀胱损伤的机制和因此的治疗靶点。CPP诱导尿路上皮细胞凋亡 48 h内坏死，14 d后增殖修复完成。当成纤维细胞生长 因子受体2（Fgfr 2）活性减弱其他组织的损伤，Fgfr 2在CPP诱导的尿路上皮损伤中的作用是 不清楚初步数据显示，Fgfr 2：1）抑制尿路上皮细胞损失和2）增强尿路上皮修复 CPP损伤后关于细胞损失，注射角质形成细胞生长因子（KGF），一种上皮Fgfr 2的配体， 在野生型小鼠中，CPP前24小时阻断凋亡性尿路上皮细胞损失。Akt，一种FGF信号传导的转换器， 已知的细胞凋亡阻遏物在KGF之后的尿路上皮中上调。关于再生， 所有膀胱尿路上皮层中Fgfr 2的条件性缺失在损伤后具有缺陷的尿路上皮修复。3天 CPP后，对照组有尿路上皮增生，尿斑蛋白（屏障蛋白）染色显著恢复， 炎症和出血的主要解决，而突变膀胱的增生较少， 尿斑蛋白染色和持续出血和炎症。而突变体和对照组都有扩增， CPP后3天，角蛋白14（Krt 14）阳性推定祖细胞穿过基底层，突变Krt 14+细胞 肥大细胞核增大提示细胞周期缺陷。细胞周期分析和DNA测定 内容表明突变Krt 14+细胞具有异常的核内复制（DNA复制没有完成， 有丝分裂，导致多倍体）。经历明显的内复制的Fgfr 2突变细胞也有证据表明， 损伤后3天DNA损伤/复制应激增加。鉴于Fgfr 2刺激Erk， 细胞周期进入和内复制，Erk及其读数进行了评估，两者都减少突变体3 CPP后的几天再生缺陷，包括大（可能是多倍体）Krt 14+细胞，持续10天后CPP。 总之，假设Fgfr 2信号通过抑制细胞凋亡来改善CPP引起的尿路上皮损伤 并通过Erk抑制尿激酶的内复制促进CPP后的再生。为了验证这一 假设，提出了以下目的：目的1：研究Fgfr 2信号转导的刺激如何阻断CPP。 诱导膀胱尿路上皮细胞丢失。全动物和基于细胞的测定将阐明Fgfr 2/Akt阻断 CPP诱导的凋亡性损伤。Akt抑制剂将在KGF之前使用，以显示Akt在Fgfr 2下游的作用。 目的2：确定Fgfr 2如何促进CPP损伤后膀胱尿道的再生。整个动物和 基于细胞的分析将阐明Fgfr 2/Erk抑制核内复制和驱动再生的作用，包括 在突变体中用组成型活性Erk进行遗传拯救，在对照中用化学拯救加速修复。目的 3：确定CPP损伤后Fgfr 2信号传导在膀胱尿道炎中的细胞特异性作用。Fgfr 2将被删除 在特定的尿路上皮层，以确定CPP损伤后的细胞特异性行动。

Project Summary/Abstract: Cyclophosphamide (CPP)-induced injury to bladder urothelium can lead to life-threatening health conditions including hemorrhagic cystitis and bladder cancer. The application’s broad long-term objectives are to identify mechanisms driving CPP bladder injury and thus therapeutic targets. CPP induces urothelial loss from apoptosis and necrosis within 48 hours, followed by proliferation and repair finishing by 14 days. While fibroblast growth factor receptor 2 (Fgfr2) activity blunts injury in other tissues, roles of Fgfr2 in CPP-induced urothelial injury are unclear. Preliminary data shows that Fgfr2: 1) dampens urothelial cell loss and 2) enhances urothelial repair after CPP injury. Regarding cell loss, injection of keratinocyte growth factor (KGF), a ligand for epithelial Fgfr2, 24 hours prior to CPP in wildtype mice blocks apoptotic urothelial cell loss. Akt, a transducer of Fgf signaling and known repressor of apoptosis, is upregulated in urothelium after KGF. Regarding regeneration, mice with conditional deletion of Fgfr2 in all bladder urothelial layers have defective urothelial repair after injury. At 3 days post-CPP, controls had urothelial hyperplasia, significant restoration of uroplakin (barrier protein) staining and major resolution of inflammation and hemorrhage, while mutant bladders had less hyperplasia, attenuated uroplakin staining, and ongoing hemorrhage and inflammation. While both mutants and controls had expansion of Keratin 14 (Krt14)-positive putative progenitor cells across basal layers 3 days after CPP, mutant Krt14+ cells were hypertrophic with enlarged nuclei suggesting a cell cycle defect. Cell cycle profiling and assays for DNA content suggest that mutant Krt14+ cells have aberrant endoreplication (DNA replication without completion of mitosis, leading to polyploidy). Fgfr2-mutant cells undergoing apparent endoreplication also had evidence of increased DNA damage/replication stress 3 days after injury. Given that Fgfr2 stimulates Erk that can suppress cell cycle entry and endoreplication, Erk and its readouts were assessed and both were reduced in mutants 3 days after CPP. Regeneration defects, including large (likely polyploid) Krt14+ cells, persisted 10 days after CPP. Together, the hypothesis is that Fgfr2 signaling ameliorates urothelial injury from CPP by suppressing apoptosis via Akt and promotes regeneration after CPP by repressing endoreplication of urothelium via Erk. To test this hypothesis, the following Aims are proposed: Aim 1: Investigate how stimulation of Fgfr2 signaling blocks CPP- induced bladder urothelial cell loss. Whole animal and cell-based assays will elucidate roles of Fgfr2/Akt to block CPP-induced apoptotic injury. Akt inhibitors will be used prior to KGF to show roles of Akt downstream of Fgfr2. Aim 2: Determine how Fgfr2 promotes regeneration of bladder urothelium after CPP-injury. Whole animal and cell-based assays will elucidate roles of Fgfr2/Erk to suppress endoreplication and drive regeneration, including genetic rescue with constitutively active Erk in mutants and chemical rescue to accelerate repair in controls. Aim 3: Identify the cell-specific roles of Fgfr2 signaling in the bladder urothelium after CPP injury. Fgfr2 will be deleted in specific urothelial layers to identify cell-specific actions after CPP-injury.