RUI: Investigating Non-Linear Tissue Deformations Using Hydra Mouth Opening as a Quantitative in Vivo Model

上皮组织遍布全身，发挥着多种重要功能。上皮的完整性对于维持发育和体内平衡过程中的生理功能是不可或缺的。上皮组织承受极端变形-弯曲，拉伸和压缩-在广泛的时间和长度范围内。该项目创建了一个跨学科的研究和教育计划，旨在描述上皮组织极端变形的原因和影响。一个主要的优势在于实验系统的独创性：淡水水螅，它已被证明是一个强大的体内生物力学系统。PI将研究九头蛇的张嘴，这是一个重要的生理过程，完全依赖于组织变形，其中上皮细胞在几十秒内经历了每个细胞高达200%的方位应变。口张开速度快，可以用荧光显微镜观察。因此，这是一个令人兴奋的系统，可以在动手教学实验室环境中教授本科生关于动力系统的知识。PI将为她的系统生物学课程设计一个为期三周的开口实验模块。本模块将提供独特的动手接触组织生物力学。PI还将为斯沃斯莫尔学院（Swarthmore College）的儿童科学项目（Science for Kids program）开发一个关于九头蛇行为的实践练习，该项目为来自邻近城镇切斯特（Chester）的儿童提供服务，Chester主要是一个少数族裔社区。最后，她将建立在她成功吸引本科生参与她的研究的记录上，并继续努力增加妇女和其他代表性不足的少数民族的研究参与。本研究解决了非线性组织力学在生理背景下的作用的基本问题。九头蛇的开口作为一种体内生物物理系统位于“金发姑娘区”，因为它足够简单，可以进行数学描述，但又足够复杂，可以研究多组分分层、结构和生物力学反馈的影响。PI将剖析九头蛇张开嘴巴的细胞和分子机制。据推测，张嘴是由神经元信号（感觉）触发的，该信号通过钙波和/或机械偶联在上皮细胞间传播。这将通过使用钙指示剂的体内荧光延时成像，正常和无神经的九头蛇菌株的嫁接实验，以及物理和化学操作来改变细胞间的通信和机械特性来进行测试。该小组将使用现有的图像分析和流变学工具量化这些扰动的影响。此外，PI将确定组织水平的约束如何影响张嘴。为了研究这一点，PI将通过手术切除不同数量的组织，并使用几何约束来改变头部几何形状。PI还将研究细胞外基质（ECM）的作用，它通过荧光标记的ECM成分的实时成像和ECM性质的化学操作来偶联上皮细胞层。本文将建立口腔张开的时空动力学数学模型。PI将使用实验数据约束模型中非线性项的比例和依赖关系，并提取与过程相关的紧急长度和时间尺度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Epithelial tissues are found throughout the body and exercise a variety of critical functions. Epithelial integrity is indispensable for maintaining physiological functions during development and homeostasis. Epithelial tissues withstand extreme deformations - bending, stretching, and compression - on a broad range of time and length scales. This project creates an interdisciplinary research and education program aimed at characterizing the causes and effects of extreme deformations in epithelial tissues. A major strength lies in the originality of the experimental system: the freshwater polyp Hydra, which has been demonstrated to be a powerful in vivo biomechanical system. The PI will study Hydra mouth opening, a physiologically important process, that relies exclusively on tissue deformation wherein epithelial cells experience azimuthal strains up to 200% per cell, within tens of seconds. Mouth opening is quick and can be visualized using epifluorescence microscopy. Thus, this is an exciting system to teach undergraduate students about dynamical systems in a hands-on teaching laboratory setting. The PI will design a 3-week mouth opening laboratory module for her Systems Biology course. This module will provide unique hands-on exposure to tissue biomechanics. The PI will also develop a hands-on exercise on Hydra behavior for the Science for Kids program at Swarthmore College, which serves children from the neighboring town of Chester, a primarily minority community. Finally, she will build upon her track record of successfully engaging undergraduate students in her research and continue her efforts toward increasing research participation of women and other underrepresented minorities. This study addresses fundamental questions on the role of non-linear tissue mechanics in a physiological context. Hydra mouth opening sits in the ‘Goldilocks zone’ as an in vivo biophysical system because it is simple enough for a mathematical description and complex enough to study effects of multicomponent layering, structure, and biomechanical feedback. The PI will dissect the cellular and molecular mechanisms by which Hydra opens its mouth. It is hypothesized that mouth opening is triggered by a neuronal signal (sensation), which is propagated through the epithelium from cell-to-cell by calcium waves and/or mechanical coupling. This will be tested using in vivo fluorescence time-lapse imaging using calcium indicators, grafting experiments of normal and nerve-free Hydra strains, and physical and chemical manipulations to change cell-cell communication and mechanical properties. The group will quantify the effect of these perturbations using existing image analysis and rheology tools. In addition the PI will determine how tissue-level constraints affect mouth opening. To study this, the PI will surgically excise different amounts of tissue and use geometrical constraints to alter head geometry. The PI will also study the role of the extracellular matrix (ECM), which couples the epithelial cell layers via live imaging of fluorescently tagged ECM components and chemical manipulation of ECM properties. A mathematical model of the spatial and temporal dynamics of mouth opening will be developed. The PI will constrain the scaling and dependencies of the non-linear terms in the model using experimental data and extract emergent length and timescales associated with the process.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.