Developmental processes shaping the luminal surface & stem cell zones in the gut

描述（申请人提供）：胃肠道管腔表面沿肠道解剖节段有明显的结构，如中肠的胃褶、环褶和肠绒毛，后肠的胃粘膜和结肠绒毛。内胚层地形的出现与细胞增殖成图案阵列的空间限制相一致，随后将形成隐窝和凹窝。这些上皮干细胞区维持肠道的管腔折叠结构。绒毛萎缩可导致营养不良和脱水，往往是难治性的；管腔干细胞区结构的破坏是癌症的早期征兆。了解干细胞区和管腔地形的模式是如何相关的，将有助于了解这些疾病。最近，研究表明，发育中的小肠管腔地形的形成可以完全理解为机械力的多轴屈曲。不同轴向平滑肌分化的时机为生长的粘膜产生绒毛提供了充分的物理约束。这一发现表明，沿着消化道的不同形状的褶皱也可能是由一些物理参数的变化引起的。此外，这一发现表明，通过屈曲形成的褶皱可能为肠道中有图案的、受限的上皮干细胞区提供了径向上不均匀的位置线索。最后，指出了机械过程在腔内再生条件中的可能作用。为了研究这一点，提出了以下目标：确定物理力在确定肠道前后轴（A-P）不同内胚层地形中的作用。具体目标2。确定拓扑结构在发育中的小肠干细胞区形成和维持中的分子信号事件中的作用。具体目标3。确定物理力量在病理性损伤后成人肠上皮恢复过程中的作用。这些研究将结合小鸡和老鼠系统提供的独特优势。它们与人类的解剖结构和肠道发育非常相似。机械性能的测量和肠道外植体的物理操作将与计算机建模方法相结合，以了解机械力在塑造肠道不同腔地形中的作用。对外植体培养的药理学和遗传扰动将被用来理解形状和形态梯度与干细胞区室模式的关系。这项工作可能为我们对绒毛萎缩等病理条件的理解提供了新的视角，但也可能有助于更全面地了解肠道形态发生背后的分子和机械力之间的关系。

DESCRIPTION (provided by applicant): The luminal surface of the gastrointestinal tract has distinct structures along the anatomical segments of the gut such as the gastric rugae, circular folds and villi in the midgut, and haustra and the colonic villi in the hindgut. The emergence of the endodermal topography coincides with the spatial restriction of proliferating cells into patterned arrays from which crypts and pits will later form. These epithelial stem cell zones maintain the luminal fold structure of the gut. Villous atrophy can lead to malnutrition and dehydration that are often refractory; disruption of the luminal stem cell zone architecture is an early sign of cancers. An understanding of how the patterning of the stem cell zones and luminal topography are related would give insight to these diseases. Recently, it has been demonstrated that the generation of luminal topography of the developing small intestine can be completely understood in terms of multi-axial buckling by mechanical forces. The timing of smooth muscle differentiation in different axis provide sufficient physical constraint to the growing mucosa to generate the villi. This finding suggests that the different shapes of folds along the alimentary canal may arise by variation of a few physical parameters as well. Moreover, the finding suggests that the folds by buckling may provide radially non-uniform positional cues for patterned, restricted epithelial stem cell zones in the gut. Lastly, it points o the possible role of mechanical processes in luminal regeneration conditions. To investigate this, following aims are proposed: Specific Aim 1. Determine the role of physical forces in specifying the different endodermal topographies along the anterior-posterior (A-P) axis of the gut. Specific Aim 2. Determine the role of topology on molecular signaling events in the formation and maintenance of stem cell zones in the developing small intestine. Specific Aim 3. Determine the role of physical forces during the recovery of the adult gut epithelium following pathologic insult. These studies will combine the unique advantages afforded by both chick and mouse systems. They share close similarity to human anatomy and gut development. Measurement of mechanical properties and physical manipulation of gut explants will be combined with in silico modeling approaches to understand the role of mechanical forces in shaping the different luminal topographies of the gut. Pharmacological and genetic perturbations on explant cultures will be utilized to understand the relationship of shape and morphogen gradients to the patterning of the stem cell compartments. The work may give a fresh light on our understanding of pathological conditions such as villous atrophy, but may also contribute to a more comprehensive picture between the molecular and mechanical forces that underlie gut morphogenesis.