Signaling Pathways Associated with Crypt Fission

描述(由申请人提供)： 在大量肠道丢失后，剩余肠道的适应性过程导致粘膜表面积的扩大，以加强营养物质的消化和吸收。肠功能衰竭发生在无法充分代偿的患者，导致长期需要肠外营养以维持足够的营养和液体平衡。我正在进行的K08工作使用小鼠小肠切除模型来研究回肠分泌谱系在适应过程中的作用，以及其他研究人员最近的报告，强调了在适应反应中存在显著的地区差异的事实。这些发现导致了回盲部切除(ICR)小鼠模型的发展，以评估空肠的适应性。这一模型表明，空肠的部分长期适应性反应是由于肠道干细胞的扩张，通过隐窝分裂增加了隐窝的总数。与假手术动物相比，这种机制在不改变增殖、隐窝深度或绒毛高度的情况下增加了肠道的口径。据我所知，这是第一份关于隐窝分裂是适应性反应的组成部分的报告。以前，由于隐窝分裂而导致的隐窝数量增加与出生后发育期间的肠道干细胞扩张有关，也是由于放射或化疗暴露导致的肠道干细胞丢失的结果。尽管在这些不同条件下驱动隐窝分裂的机制尚未得到评估，但最近在转基因小鼠中的研究表明，抑制骨形态发生蛋白(BMP)信号导致Wnt/(-catenin)通路激活，从而增加隐窝分裂。这个R03应用程序的目标是解决这样的假设，即抑制BMP信号导致Wnt/(-catenin)通路激活，该通路与发育过程中和ICR后的隐窝分裂有关。为了实现这一点，我们将使用定量原位杂交和免疫组织化学方法评估候选通路基因表达的变化，比较动物在发育过程中[P7(低裂变)与P21(高裂变)]和手术切除后7天[假手术(低裂变)与ICR(高裂变)]。通过基因表达微阵列鉴定的这些组之间差异表达的转录本将被比较，以确定与隐窝分裂相关的共同变化。这些研究将为肠道丧失后发生的长期适应机制提供重要的见解，从而为肠衰竭患者提供潜在的治疗方法。

DESCRIPTION (provided by applicant): Following massive intestinal loss, an adaptive process in the remaining bowel results in the expansion of mucosal surface area to enhance digestion and absorption of nutrients. Intestinal failure occurs in patients who are unable to sufficiently compensate, resulting in the prolonged requirement of parenteral nutrition to sustain adequate nourishment and fluid balance. My ongoing K08 work using a murine model of small bowel resection to investigate the role of secretory lineages in the ileum during adaptation, together with recent reports from other investigators, has highlighted the fact that there are marked regional differences in the adaptive response. These findings led to the development of a murine model of ileocecal resection (ICR) to allow evaluation of adaptation in the jejunum. This model demonstrates that part of the long-term adaptive response in the jejunum occurs due to an expansion of intestinal stem cells increasing the total number of crypts by crypt fission. This mechanism increases the caliber of the intestine without changes in proliferation, crypt depth or villus height when compared to sham-operated animals. To my knowledge this is the first report of crypt fission being a component of the adaptive response. An increase in crypt number by crypt fission has previously been associated with intestinal stem cell expansion during postnatal development, and as a result of intestinal stem cell loss due to radiation or chemotherapy exposure. Although the mechanisms driving crypt fission in these various conditions have not been evaluated, recent studies in transgenic mice have demonstrated inhibition of bone morphogenic protein (BMP) signaling results in the activation of Wnt/(-catenin pathways increasing crypt fission. The goal of this R03 application is to address the hypothesis that inhibition of BMP signaling results in the activation of the Wnt/(-catenin pathways associated with crypt fission during development and following ICR. To achieve this, we will assess changes in the expression of candidate pathway genes using quantitative in situ hybridization and immunohistochemistry comparing animals during development [P7 (low fission) vs. P21 (high fission)] and 7 d following surgical resection [sham-operation (low fission) vs. ICR (high fission)]. Differentially expressed transcripts between these groups identified by gene expression microarrays will be compared to identify common changes associated with crypt fission. These studies will provide important insight into the long-term adaptive mechanisms that occur following intestinal loss, leading to potential therapies for patients suffering from intestinal failure.