Mechanisms of Physiological Organ Shrinkage

生理器官萎缩的机制

• 批准号: 10494209
• 负责人: Lucy Erin O'brien
• 金额: $ 47.65万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-30 至 2025-08-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10494209
• 关键词: Address; Adopted; Adult; Anatomy; Animals; Apoptosis; Apoptotic; Behavior; Biology; Calcium Oscillations; Celiac Disease; Cell Count; Cell Lineage; Cell Therapy; Cell division; Cells; Complex; Data; Daughter; Digestive Physiology; Disease; Drosophila genus; Endotoxemia; Enterocytes; Equation; Equilibrium; Experimental Models; Famines; Food; Future; Genetic; Giardiasis; Goals; Growth; Health; Human; Image; Individual; Ingestion; Intestines; Invertebrates; Investigation; Knowledge; Label; Laboratories; Laboratory Study; Mammals; Mammary gland; Mechanics; Methods; Midgut; Mitosis; Modeling; Modernization; Molecular; Monitor; Nutrient; Organ; Organ Size; Parenteral Nutrition; Pathologic; Pathway interactions; Periodicity; Physiological; Protocols documentation; Refractory; Regulation; Reporter; Research; Rodent; Siblings; Side; Signal Transduction; Skeletal Muscle; Skin; Small Intestines; Starvation; Testing; Time; Tissues; Transcription Coactivator; Translating; Undifferentiated; Wild Animals; Withdrawal; Work; base; body cavity; cell behavior; fly; frontier; genetic manipulation; human disease; in vivo; in vivo monitoring; innovation; mature animal; mechanical force; optogenetics; promoter; purge; response; serial imaging; stem cell differentiation; stem cell division; stem cells; tool; virtual

PROJECT SUMMARY Many adult organs--for instance, intestine, mammary gland, skeletal muscle, skin—respond to reduced levels of functional demand by shrinking their physical size. In these organs, cells are lost faster than they are made, leading to a reduction in total cell number. The intestine is a broadly conserved exemplar of demand- driven organ shrinkage. In wild animals, cyclic periods of starvation cause intestinal size to shrink by 60-75%. Humans also undergo healthy intestinal shrinkage, but excessive or dysregulated cell loss can quickly become pathological, as seen in enteropathies like celiac sprue, endotoxemia, and giardiasis. Yet—unlike the mechanisms that balance cell division/loss during everyday turnover—the mechanisms that tune cell imbalance for physiological shrinkage are virtually unknown. The roadblock to mechanistic investigation of intestinal shrinkage has been the lack of a tractable laboratory model, which must allow cells (and their dynamic behaviors) to be monitored across time and must possess cell-specific markers and other tools to facilitate mechanistic studies. Historically, studies used rodents, but modern research protocols cannot replicate natural famine/feast cycles. My lab has developed a new invertebrate model of intestinal shrinkage that is both tractable and genetically manipulable: the Drosophila adult midgut, akin to the vertebrate small intestine. We demonstrate that intestinal shrinkage is conserved in Drosophila, and we document that its underlying basis is the massive squeezing-out of now-superfluous enterocytes through active extrusion. Here, we investigate intestinal shrinkage from both sides of the equation for net cellular balance: mature cell loss (Aim 1) and stem cell capacity (Aim 2). Our studies leverage the midgut’s superlative toolkit of cell- specific genetic reporters and our own pioneering innovations for real-time and longitudinal imaging of functioning midguts inside live animals. In Aim 1, we ask how the gut senses loss of ingested food— mechanical compression, lack of nutrients, or both. We test if two known regulators of extrusion, the transcriptional co-activator YAP/Yorkie and intercellular Ca2+ waves, function during shrinking to increase extrusions. Third, we probe whether a shrinking gut regulates cell extrusions at the organ scale or at the level of individual cells. In Aim 2, we seek the mechanisms that cause a 75% culling of the stem cell pool during shrinkage—even as stem cell mitoses paradoxically increase. We will test if stem cells initiate non-self- renewing divisions, adopt terminal fates directly, and/or activate apoptosis. The fly gut’s digestive physiology, stem cell lineages, and molecular regulation are similar to humans. Hence by elucidating the cell-to-organ scale mechanisms that operate at this frontier of tissue biology, this project may yield leads for therapies to treat cellular imbalances in human disease.

项目概要 许多成人器官——例如肠道、乳腺、骨骼肌、皮肤——对减少的 通过缩小其物理尺寸来满足功能需求。在这些器官中，细胞丢失的速度比原来要快 产生，导致细胞总数减少。肠道是需求的广泛保守的范例 导致器官萎缩。在野生动物中，周期性的饥饿会导致肠道尺寸缩小 60-75%。 人类也会经历健康的肠道收缩，但过度或失调的细胞损失很快就会变得 病理性的，如乳糜泻、内毒素血症和贾第鞭毛虫病等肠病。然而——与 在日常更新过程中平衡细胞分裂/损失的机制——调节细胞的机制 生理收缩的不平衡几乎是未知的。 肠道收缩机制研究的障碍是缺乏易于处理的方法 实验室模型，必须允许跨时间监测细胞（及其动态行为）并且必须 拥有细胞特异性标记和其他工具来促进机制研究。历史上，研究使用 啮齿动物，但现代研究方案无法复制自然的饥荒/盛宴周期。 我的实验室开发了一种新的肠道收缩无脊椎动物模型，该模型既易于处理又易于控制 可基因操纵：果蝇成体中肠，类似于脊椎动物的小肠。我们展示 肠道收缩在果蝇中是保守的，我们记录其根本基础是大量的 通过主动挤压挤出现在多余的肠细胞。 在这里，我们从净细胞平衡方程的两边研究肠道收缩：成熟 细胞损失（目标 1）和干细胞能力（目标 2）。我们的研究利用中肠最高级的细胞工具包 特定的基因记者和我们自己的实时和纵向成像的开创性创新 活体动物体内发挥功能的中肠。在目标 1 中，我们询问肠道如何感知摄入食物的损失—— 机械压缩、缺乏营养或两者兼而有之。我们测试是否有两个已知的挤出调节器， 转录共激活因子 YAP/Yorkie 和细胞间 Ca2+ 波，在收缩期间发挥作用以增加 挤压件。第三，我们探讨缩小的肠道是否在器官尺度或水平上调节细胞挤出 单个细胞。在目标 2 中，我们寻找导致 75% 干细胞库在 收缩——即使干细胞有丝分裂反而增加。我们将测试干细胞是否启动非自我 更新分裂，直接采取最终命运，和/或激活细胞凋亡。 果蝇肠道的消化生理、干细胞谱系和分子调控与人类相似。 因此，通过阐明在组织生物学这一前沿运作的细胞到器官的规模机制， 该项目可能会产生治疗人类疾病细胞失衡的疗法的线索。