Mechanochemical mechanisms of intestinal villus development and regeneration

项目摘要 肠绒毛包括由上皮层包裹的间充质核心，上皮层一起增加肠绒毛的粘附。 肠吸收表面积近100倍。辐射、化疗药物和 许多胃肠道疾病引起绒毛萎缩，导致营养吸收不良和消化不良。 并发症值得注意的是，在许多情况下，萎缩的绒毛完全再生，恢复其手指状形态， 然而在其他情况下，再生过程受损，导致持续的绒毛萎缩。如何绒毛 再生它们的形态，以及为什么这个过程会失败是未知的。此外，我们缺乏对 哺乳动物绒毛在发育过程中最初是如何构建的。这个项目的长期目标是了解如何 在发育和再生过程中整合信号和力来塑造哺乳动物绒毛， 人类肠道组织生长和再生的策略。 绒毛形成起始于胚胎中，其中间充质细胞聚集在覆盖的绒毛周围。 上皮细胞形成凝聚，称为绒毛簇。虽然绒毛簇似乎需要绒毛 形态发生，其形成的机制尚未确定。在这里，我探索一个链接， 在哺乳动物胚胎发育过程中， 成年人在再生过程中。首先，我量化了绒毛簇的物理特性，并测试了 开始间充质凝聚成簇，随后上皮弯曲成绒毛 通过间充质细胞收缩性并通过不同的界面张力加强。接下来，我检查 这些间充质凝聚事件和绒毛形成机制的遗传机制。 具体地说，我提出并测试了一个由单细胞RNA测序数据生成的模型，其中收缩性 上皮下间充质的活动由内皮素依赖性Ca2+信号传导触发， 收缩通过间隙连接在相邻细胞之间局部耦合，以驱动簇的形成 和上皮弯曲。最后，我测试是否上皮下间充质细胞利用类似的机械化学 再生绒毛结构以响应成年肠损伤的机制，此外， 以单细胞分辨率表征绒毛再生以鉴定成年绒毛的新遗传介质 架构总之，这些研究将确定如何信号和力量相互作用，形成和改革哺乳动物 肠绒毛，确定新的治疗靶点，以刺激绒毛再生，更广泛地说，将解决 组织的形状和大小是如何再生的

PROJECT SUMMARY Intestinal villi comprise a mesenchymal core ensheathed by an epithelial layer that together increase the intestinal absorptive surface area nearly 100 fold. Damage to villi incurred by irradiation, chemotherapeutics, and many gastrointestinal maladies cause villus atrophy, resulting in nutrient malabsorption and digestive complications. Remarkably, in many cases atrophied villi fully regenerate to restore their finger-like morphology, yet in other situations the regenerative process is impaired, resulting in persistent villus atrophy. How villi regenerate their morphology and why this process can fail are unknown. Moreover, we lack an understanding of how mammalian villi are initially built during development. The long-term goal of this project is to understand how signals and forces are integrated to sculpt mammalian villi during development and regeneration so as to improve strategies for growing and regenerating human intestinal tissue. Villus formation initiates in the embryo with the aggregation of mesenchymal cells adjacent to the overlying epithelium that form condensations, termed villus clusters. While villus clusters seem to be required for villus morphogenesis, the mechanisms underlying their formation have not been identified. Here, I explore a link between these events that first build villi in the mammalian embryo during development and those that rebuild them in the adult during regeneration. First, I quantify the physical properties of villus clusters and test whether mesenchymal condensation into clusters, and the subsequent buckling of the epithelium into villi, is initiated through mesenchymal cellular contractility and reinforced by differential interfacial tension. Next, I examine the genetic mechanisms underlying the mechanics of these mesenchymal condensation events and villus formation. Specifically, I put forth and test a model generated from single-cell RNA sequencing data wherein the contractile activities of the subepithelial mesenchyme are triggered by Endothelin-dependent Ca2+ signaling, and the contractions become coupled locally between neighboring cells through gap junctions to drive cluster formation and epithelial buckling. Finally, I test whether subepithelial mesenchymal cells utilize similar mechanochemical mechanisms to regenerate villus architecture in response to damage in the adult intestine, and additionally, characterize villus regeneration at single cell resolution to identify new genetic mediators of adult villus architecture. Together, these studies will define how signals and forces interact to form and reform mammalian intestinal villi, identify new therapeutic targets to stimulate villus regeneration, and, more broadly, will address the question of how tissue shape and size are regenerated.