Linking cell forces to organ-scale morphogenesis of the small intestine

项目摘要/摘要 长长的小肠在体腔的范围内被组织成紧凑的环状，以便 获得足够的养分吸收表面积。先天性胃肠道畸形导致肠循环异常 疾病，如中肠扭转，通常使人虚弱或致命。在开发过程中，这些循环形成 通过屈曲，一种常见的形态发生机制，组织通过该机制向外弯曲以响应压力 机械力。最初直的肠管在其附着膜的约束下的伸长 肠系膜会产生压力，使管子弯曲成固定的环状结构。循环形态可以是 从几个物理参数的实验测量中预测，包括肠系膜硬度。在……里面 对延长的肠管增加拉伸的反应，肠系膜在硬化之前最初是顺应性的 并抵抗进一步伸展，从而迫使管子弯曲。这种刚性对拉伸的依赖性是 被称为结构性非线性，这种特性在成人组织中具有很好的特征，但在很大程度上被忽视了 发展，对其生物学决定因素知之甚少。在这里，我们建议澄清关键 小肠成环过程中肠系膜结构非线性的生物学基础。收集的初步数据 由申请人强烈涉及细胞收缩调节鸡肠系膜僵硬转变，与 收缩能力的破坏令人惊讶地导致肠系膜顺应性降低，而不是僵硬。 连同先前在抑制骨形态发生蛋白(BMP)活性时显示出类似变化的工作， 我们假设BMP信号诱导细胞收缩调节肠系膜预硬化顺应性(目标1)。 而这些收缩细胞对细胞外基质(ECM)的紧致作用设定了僵化转变(目标2)。 对这一假说的实验检验将有助于阐明肠道正常发育的机制。 通过将细胞行为和基质组织的分子控制与器官规模的循环相结合，这将产生 对不正确的循环引起的胃肠道出生缺陷的病因学的重要见解。 为了实现这些目标，申请者将接受跨越发展阶段的实验技术培训。 生物学和生物工程，包括鸡胚学、分子生物学、免疫化学和软组织 机械师。申请人将参加跨部门的研讨会，参加并出席工程学和 发展会议，并接受赞助商、共同赞助商和咨询委员会的指导，世卫组织 贡献不同的专业知识。申请者还将接受负责任的研究、口头和 书面沟通、指导和许多其他职业技能。这项培训将为申请者做好准备 学术界的博士后研究再生应用中生理紊乱的起源。

PROJECT SUMMARY / ABSTRACT The lengthy small intestine is organized into compact loops within the confines of the body cavity in order to achieve sufficient nutrient-absorbing surface area. Abnormal looping results in congenital gastrointestinal disorders, such as midgut volvulus, which are often debilitating or lethal. During development, these loops form by buckling, a common morphogenetic mechanism by which a tissue bends outward in response to compressive mechanical forces. Elongation of the initially straight gut tube against the constraint of its attached membranous mesentery results in compressive forces that buckle the tube into stereotyped loops. Loop morphology can be predicted from experimental measurement of a handful of physical parameters, including mesentery stiffness. In response to increasing stretch by the elongating gut tube, the mesentery is initially compliant before stiffening and resisting further extension, thereby forcing the tube to buckle. This dependence of stiffness on stretch is known as constitutive nonlinearity, a property well characterized in adult tissues but largely overlooked in development, where its biological determinants are poorly understood. Here, we propose to elucidate key biological bases of mesentery constitutive nonlinearity during small intestine looping. Preliminary data collected by the applicant strongly implicates cell contractility in tuning the stiffening transition of chick mesentery, with disruption of contractility surprisingly resulting in diminished mesentery compliance prior to unchanged stiffening. Together with prior work showing similar changes upon inhibition of bone morphogenic protein (BMP) activity, we hypothesize that BMP signaling induces cell contractility to tune mesentery pre-stiffening compliance (Aim 1) and that extracellular matrix (ECM) compaction by these contracting cells sets the stiffening transition (Aim 2). Experimental examination of this hypothesis will shed light on the mechanics of proper intestinal development by integrating molecular control of cell behavior and matrix organization with organ-scale looping, which will yield important insight into the etiology of gastrointestinal birth defects arising from improper looping. In completing these Aims, the applicant will receive training in experimental techniques spanning developmental biology and bioengineering, including chick embryology, molecular biology, immunochemistry, and soft tissue mechanics. The applicant will participate in cross-department seminars, attend and present at engineering and development conferences, and receive mentorship from the sponsor, co-sponsor, and advisory committee, who contribute a diverse range of expertise. The applicant will also train in responsible conduct of research, oral and written communication, mentorship, and many other career skills. This training will prepare the applicant for postdoctoral research in academia studying the origins of physiological disorders for regenerative applications.