Basis of Post-Fontan Protein Losing Enteropathy

描述（由申请人提供）：此申请响应NHLBI和罕见疾病办公室，以支持了解，预防和治疗罕见心脏病的新方法。这些探索性项目必须提出新的假设，并开发出证明可行性的方法。我们的目标是了解为什么3-10%接受Fontan手术矫正先天性单室心脏的患者在手术后数月至数年发生蛋白丢失性肠病（PLE）。半数PLE患者死亡。可变的发病提示多因素病因。我们假设遗传限制和环境损害导致PLE，其分子基础也未知。最近的研究结果显示，ple后fontan患者在小肠上皮细胞的基底外侧表面特异性地丢失了硫酸肝素蛋白多糖（HSPG）。我们过去的研究表明，一些患有遗传性蛋白糖基化障碍的患者会出现PLE，并表现出相同的HSPG丢失，当PLE消退时，HSPG再次恢复正常。这使得肠细胞HSPG成为相关细胞类型中唯一已知的PLE分子标记物。我们假设局部HSPG的丢失，加上fontan诱导的静脉压升高的全身性促炎条件导致了PLE。我们的初步体外数据支持这些因素的强大协同作用。在AIM 1中，我们将在体外测试这一假设，通过测量人类培养的上皮细胞的细胞旁蛋白渗漏，这些上皮细胞以不同的方式剥离HSPG，用细胞因子挑战，并置于压力下。在AIM 2中，遗传上缺乏主要基底外侧HSPG核心蛋白Syndecan-1或所有由肠上皮细胞合成的HS的小鼠模型将被评估在炎症挑战和/或压力增加的情况下蛋白质损失。我们预测hspg缺陷小鼠及其衍生的肠黏膜对炎症诱导的PLE更为敏感。这些结果可以提供对PLE如何发展的基本理解，确定Fontan患者的遗传风险，并为这种神秘罕见疾病的新疗法提供见解。

DESCRIPTION (provided by applicant): This application responds to NHLBI and the Office of Rare Diseases to support novel approaches to understand, prevent, and treat rare heart diseases. These exploratory projects must present new hypotheses and develop ways to demonstrate feasibility. Our goal is to understand why 3-10% of patients who have Fontan surgery to correct congenital univentricular hearts develop protein-losing enteropathy (PLE) months to years after the operation. Half of the PLE patients die. The variable onset suggests a multifactorial etiology. We hypothesize that genetic limitations and environmental insults lead to PLE, whose molecular basis is also unknown. Recent results show the PLE-stricken post-Fontan patients lose heparan sulfate proteoglycan (HSPG) specifically from the basolateral surface of small intestine epithelial cells. Our past work shows that some patients with inherited protein glycosylation disorders develop PLE and show an identical HSPG loss, which normalizes again when PLE resolves. This makes enterocyte HSPG the only known molecular marker of PLE in a relevant cell type. We hypothesize that localized loss of HSPG, plus a general systemic pro-inflammatory condition within the Fontan-induced setting of increased venous pressure cause PLE. Our preliminary in vitro data supports a robust synergism of these factors. In AIM 1, we will test this hypothesis in vitro by measuring paracellular protein leakage in human cultured epithelial cells variably stripped of their HSPG, challenged with cytokines, and placed under pressure. In AIM 2, mouse models that genetically lack the major basolateral HSPG core protein, Syndecan-1, or all HS synthesized by intestinal epithelial cells will be assessed for protein loss with an inflammatory challenge and/or increased pressure. We predict that the HSPG-deficient mice and intestinal mucosa derived from them will be more sensitive to inflammation-induced PLE. The results could provide a fundamental understanding of how PLE develops, identify Fontan patients genetically at risk for developing PLE, and provide insights to new therapeutics for this enigmatic rare disease.