Cross talk between epithelial, inflammatory and mesenchymal cells in the development of portal fibrosis

有相当大的兴趣，了解机制之间的关系，胆 损伤和门静脉纤维化，慢性胆管病进展的主要机制。 先天性肝纤维化（CHF）和Caroli病（CD）是遗传性胆管疾病 由PKHD 1突变引起，PKHD 1是编码纤维囊蛋白的基因，其特征是胆汁性 发育不全、节段性导管扩张和进行性门静脉纤维化伴门静脉高压。在 CHF和CD、胆管细胞功能障碍和门静脉纤维化是由肝细胞的遗传缺陷引起的。 胆管上皮，而不是坏死性炎症损伤，因此，代表了一种模型疾病， 阐明胆管细胞在胆道疾病的门静脉纤维化中的作用。我们 我建议在CHF/CD小鼠模型中研究这些机制， Pkhd 1（Pkhd 1 del 4/del 4小鼠）。我们公布的初步数据表明， pkhd 1del 4/del 4小鼠胆道纤维化的发展与a 巨噬细胞和aSMA阴性但胶原阳性的胆管周围细胞浸润 纤维细胞此外，我们还显示了Pkhd 1del 4/del 4胆管细胞， 其特征是β-连环蛋白的PKA依赖性磷酸化增加， pSer-675-β-catenin的Ser 675核转位及其转录水平的提高 活动β-连环蛋白与FXR相互作用，抑制其抗炎信号传导， 从而激活NF-kB和炎性小体依赖性分泌IL-1β， CXCL 1和CXCL 10，反过来，能够吸引巨噬细胞。通过抑制CXCR 3， CXCL 10受体，或通过给予FXR激动剂（奥贝胆酸）巨噬细胞 浸润以及囊肿生长、脾脏大小和肝纤维化显著减少。 最后，在Pkhd 1del 4/del 4胆管细胞中，雅普的核穿梭是细胞凋亡的先决条件。 β-连环蛋白激活，因此，对于促纤维化介质CTGF，CXCL 1和 CXCL 10. 基于这些观察，我们提出，当纤维囊蛋白有缺陷时， β-连环蛋白、雅普、FXR信号传导调节几种胆汁上皮细胞的分泌， 趋化因子协调胆管周围浸润的连续变化， 用于建立门静脉炎症和纤维化。为了证明这一新的假设，我们 将在具体目标1中研究雅普、β-连环蛋白和FXR信号传导之间的关系， pkhd 1del 4/del 4小鼠，它们在控制囊肿生长、炎症、纤维化和 它们作为治疗靶点的相关性。在具体目标2中，我们将研究 Pkhd 1del 4/del 4小鼠膀胱周围浸润及其动态变化 以及治疗策略的影响。 这些研究将为胆管细胞功能障碍在门静脉纤维化中的作用提供一个新的模型。 调控信号的知识可能会导致新的治疗策略。

There is considerable interest in understanding the mechanistic relationships between biliary damage and portal fibrosis, the main mechanism of progression in chronic cholangiopathies. Congenital Hepatic Fibrosis (CHF) and Caroli disease (CD) are genetic cholangiopathies caused by mutations in PKHD1, the gene encoding for fibrocystin, characterized by biliary dysgenesis, segmental ductal dilations and progressive portal fibrosis with portal hypertension. In CHF and CD, cholangiocyte dysfunction and portal fibrosis are caused by a genetic defect in the biliary epithelium, rather than by necroinflammatory damage and thus, represent a model disease for elucidating the role of cholangiocytes in portal fibrosis of biliary diseases. We propose to study these mechanisms in a mouse model of CHF/CD, harbouring a deleting mutation in Pkhd1 (Pkhd1del4/del4 mice). Our published and preliminary data have established that in Pkhd1del4/del4 mice biliary fibrosis develops in conjunction with accumulation of a peribiliary cell infiltrate by macrophages and by aSMA-negative, but collagen positive cells like fibrocytes. Furthermore, we have shown Pkhd1del4/del4 cholangiocytes are characterized by an increased PKA-dependent phosphorylation of β-catenin at Ser675, the nuclear translocation of pSer-675-β-catenin and its increased transcriptional activity. ß-catenin interacts with FXR inhibiting its anti-inflammatory signaling and thereby activating NF-kB and the inflammasome-dependent secretion IL-1β and consequently of CXCL1 and CXCL10, that are, in turn, able to attract macrophages. By inhibiting CXCR3, the cognate receptor of CXCL10, or by administration of an FXR agonist (obeticholic acid) macrophage infiltration was significantly reduced as well as cyst growth, spleen size and liver fibrosis. Finally, in Pkhd1del4/del4 cholangiocytes, nuclear shuttling of YAP is a pre-requisite for β-catenin activation and thus, for the expression of the pro-fibrogenic mediators CTGF, CXCL1, and CXCL10. Based on these observations, we propose that, when fibrocystin is defective, the interplay among β-catenin, YAP, FXR signalling regulates the secretion from the biliary epithelium of several chemokines that orchestrate sequential changes in the peribiliary infiltrate and are responsible for the establishment of portal inflammation and fibrosis. To demonstrate this novel hypothesis, we will investigate in specific aim 1 the relationship among YAP, β-catenin and FXR signalling in Pkhd1del4/del4 mice, their role in controlling, cyst growth, inflammation, fibrosis and their relevance as therapeutic targets. While in specific aim 2 we will investigate the nature of the pericystic infiltrate in Pkhd1del4/del4 mice, and its dynamic changes during the establishment of fibrosis and the effects of treatment strategies. These studies will provide a new model for role of cholangiocyte dysfunction in portal fibrosis. Knowledge of the regulatory signaling could lead to new therapeutic strategies.