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

项目总结/摘要 在体腔的范围内，长长的小肠被组织成紧凑的环，以便 获得足够的营养吸收表面积。先天性胃肠道异常成环 疾病，如中肠扭转，这往往是衰弱或致命的。在发育过程中， 通过屈曲，一种常见的形态发生机制，通过该机制，组织响应于压缩而向外弯曲。 机械力最初直的肠管在其附着的膜的约束下的伸长 肠系膜产生压缩力，将管弯曲成定型的环。环形态可以是 从实验测量的少数物理参数，包括肠系膜刚度预测。在 由于肠管的伸长，肠系膜对增加的拉伸作出反应，在变硬之前，肠系膜最初是顺应性的 并阻止进一步延伸，从而迫使管弯曲。刚度对拉伸的依赖性是 这种特性在成人组织中得到很好的表征，但在 发展，其生物决定因素知之甚少。在这里，我们建议阐明关键 小肠成袢过程中肠系膜结构非线性的生物学基础。收集的初步数据 强烈暗示细胞收缩性在调节鸡肠系膜的硬化转变中， 收缩性的破坏令人惊讶地导致在硬化不变之前肠系膜顺应性降低。 与先前的工作显示在抑制骨形态发生蛋白（BMP）活性后的类似变化一起， 我们假设BMP信号传导诱导细胞收缩以调节肠系膜预硬化顺应性（目的1） 并且这些收缩细胞的细胞外基质（ECM）压缩设定了硬化转变（Aim 2）。 对这一假设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， 重要的洞察力的病因胃肠道出生缺陷所产生的不适当的环。 在完成这些目标，申请人将接受培训，在实验技术跨越发展 生物学和生物工程，包括鸡胚胎学，分子生物学，免疫化学和软组织 力学申请人将参加跨部门研讨会，出席并出席工程和 发展会议，并接受赞助商，共同赞助商和咨询委员会的指导， 贡献各种专业知识。申请人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。该培训将为申请人做好准备， 在学术界从事博士后研究，研究生理疾病的起源，以供再生应用。

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.