Intestinal Stem Cell Responses to Cryptosporidium Infection

摘要 隐孢子虫仍然是艾滋病患者中一种重要的机会性病原体 HAART治疗。这种寄生虫感染人类的胃肠道上皮；感染艾滋病患者 通常会导致危及生命的疾病。隐孢子虫也是年幼儿童腹泻的常见原因 发展中国家。事实上，感染隐孢子虫与#年死亡率显著相关。 年幼的儿童，似乎使儿童容易受到肠道感染，并具有持久的年龄缺陷 身体生长和认知发展。其潜在的分子机制尚不清楚。初级阶段 隐孢子虫在人体内的感染部位是小肠，这是人体内再生 最快的速度。在我们的初步研究中，我们观察到隐孢子虫感染仅限于绒毛(主要是 肠上皮细胞)。然而，感染会导致肠干显著减少。 细胞(ISC)数量(以及几个ISC标记的表达水平)。我们还确定了一个小组 感染后肠上皮细胞中表达水平显著改变的基因。其中一些基因 编码肠细胞-ISC网络中信号通路的重要组件，因此，可能是 参与了隐孢子虫引起的ISC功能障碍。因此，我们假设隐孢子虫 肠上皮绒毛感染通过改变信号转导途径阻碍隐窝内ISC功能 肠上皮细胞到ISC网络中的通路。我们将使用体外、体外和体内感染模型和 补充生化、分子和形态方法表征ISC的功能障碍 隐孢子虫感染过程中的种群(ISC可塑性)(目标1)及其信号转导途径 与感染引起的ISC功能障碍有关(目标2)。随着这些目标的实现，我们将拥有 确定了隐孢子虫感染过程中ISC的可塑性，并确定了哪些信号通路 尤其受到感染导致ISC功能障碍的影响。这些成果将为以下方面奠定基础 建立长期的、机械的研究，以确定其发病机制(特别是长期影响) 肠道内隐孢子虫感染。

Summary Cryptosporidium remains an important opportunistic pathogen in AIDS patients who do not have access to HAART treatment. This parasite infects the gastrointestinal epithelium in humans; infection in AIDS patients often leads to life-threatening illness. Cryptosporidium is also a common cause of diarrhea in young children in developing countries. Indeed, infection with Cryptosporidium shows significant association with mortality in young children and appears to predispose children to enteric infection with lasting deficits in age-appropriate body growth and cognitive development. The underlying molecular mechanisms are unclear. The primary infection site of Cryptosporidium in human is the small intestine, one of tissues in the body that regenerates the most quickly. In our preliminary study, we observed that Cryptosporidium infection is limited to the villi (mainly enterocytes) of intestinal epithelium. Nevertheless, infection causes a significant decrease in intestinal stem cell (ISC) numbers (as well as the expression levels of several ISC markers). We also identified a panel of genes whose expression levels are significantly altered in enterocytes following infection. Some of these genes code important components of the signaling pathways in the enterocyte-ISC network and thus, may be involved in Cryptosporidium-induced ISC dysfunction. Therefore, we hypothesize that Cryptosporidium infection in the villi of intestinal epithelium impedes ISC function in the crypts through changes of signaling pathways in the enterocyte-to-ISC network. We will use in vitro, ex vivo, and in vivo infection models and complementary biochemical, molecular, and morphologic approaches to characterize the dysfunction of ISC populations (ISC plasticity) during Cryptosporidium infection (Aim 1) and identify the signaling pathways pertinent to ISC dysfunction induced by infection (Aim 2). With the completion of these aims, we will have determined the ISC plasticity during Cryprosporidium infection and identified which signaling pathways are specifically affected by infection leading to ISC dysfunction. These outcomes will establish a foundation on which to build long-term, mechnistic studies to define the pathogenesis (particularly the long-lasting effects) of Cryptosporidium infection in the intestine.