Morphogenesis of the fetal intestinal epithelium

描述（由申请人提供）：小肠上皮在发育过程中经历了一系列显著的形态发生变化。内胚层来源的上皮管最初由单层短柱状细胞组成。在E10.5和E14.5之间，管的周长和长度增加。在E14.5和E16.5之间的48小时内，上皮显著重塑，先前平坦的管腔表面转化为绒毛（上皮表面的指状突起）。由于绒毛代表了肠道的功能性吸收单位，因此详细了解导致其形成的机制是一个重要的目标。此外，未能建立适当的肠表面积（如特发性短肠综合征）可能危及生命。这里提供的数据挑战了目前关于早期肠上皮组织和上皮在E14.5重塑的机制的想法。这项工作的工作模型是：早期肠上皮（E12.5-14.5）是假复层的，通过称为g-分裂的对称细胞分裂生长（因为它们增加了上皮的周长和长度）。在E14.5，管腔表面积通过不同类型的特化细胞分裂（称为e-分裂）来扩展（因为它们用于扩展管腔表面）。在e-分裂中，在细胞动力学沟处添加新的顶端表面。因此，E-分裂将子细胞分离到不同的绒毛上。分裂后，有丝分裂后的细胞改变形状，沿着其顶/基轴缩短，并增加其顶面，作为第一绒毛出现。这种细胞重塑迅速将上皮周长转化为长度。这些过程的保真度需要Wnt 5a和平面细胞极性信号传导。以前没有研究过肠道生长的这些方面。该提案利用遗传小鼠模型，一种新的肠道外植体培养系统和先进的成像技术，以机械地解剖这些表面生成过程中涉及的相互关联的信号和图案化事件。特定目的旨在检查g-分裂（Aim 1）和e-分裂（Aim 2）的形态和功能特征，并研究肠延长的潜在机制，包括Wnt 5a和平面细胞极性信号传导（Aim 3）的作用。使用所有这些数据，将生成一个数学模型，以进一步研究祖细胞周期时间，细胞凋亡和细胞形状变化等参数在肠延长中的作用。这些研究的结果可能对胎儿肠组织的生物工程和胎儿和新生儿短肠综合征的治疗具有重要意义。

DESCRIPTION (provided by applicant): The epithelium of the small intestine undergoes a remarkable series of morphogenic changes during its development. The endodermally derived epithelial tube is initially comprised of a single layer of short columnar cells. Between E10.5 and E14.5, the tube increases in girth and length. In the 48 hours between E14.5 and E16.5, the epithelium is dramatically remodeled and the previously flat luminal surface is converted into villi (fingerlike projections of the epithelial surface). Since villi represent the functional absorptive unit of the intestine, a detailed understanding of the mechanisms leading to their formation is an important goal. Moreover, failure to establish proper intestinal surface area (as in idiopathic short bowel syndrome) can be life threatening. Data presented here challenge current thinking about the organization of the early intestinal epithelium and the mechanisms by which the epithelium is remodeled at E14.5. The Working Model underlying this work is that: The early intestinal epithelium (E12.5-14.5) is pseudostratified and grows via symmetrical cell divisions called g-divisions (because they increase epithelial girth and length). At E14.5, luminal surface area is extended by means of a different type of specialized cell division, called e-divisions (because they serve to expand the luminal surface). In e-divisions, new apical surface is added at the cytokinetic furrow. E-divisions therefore separate daughter cells onto different villi. After e-divisions, postmitotic cells change shape, shortening along their apical/basal axis and increasing their apical surface, as the first villi emerge. This cell reshaping rapidly converts epithelial girth to length. The fidelity of these processes requires Wnt5a and planar cell polarity signaling. None of these aspects of intestinal growth have previously been investigated. This proposal makes use of genetic mouse models, a novel intestinal explant culture system and advanced imaging techniques to mechanistically dissect the interconnected signaling and patterning events involved in these surface-generating processes. The Specific Aims are designed to examine the morphological and functional characteristics of g-divisions (Aim 1) and e-divisions (Aim 2) and to investigate the mechanisms underlying intestinal lengthening, including the role of Wnt5a and planar cell polarity signaling (Aim 3). Using all of these data, a mathematical model will be generated to further investigate the role of such parameters as progenitor cycling time, apoptosis and cell shape change in intestinal lengthening. The outcome of these studies could have important implications for the bioengineering of fetal intestinal tissue and the treatment of short bowel syndrome in the fetus and newborn.