Collaborative Research: EAGER: The Role of Cell-Cell Forces in the Cadherin Switch Model

这个早期概念的探索性研究拨款(AGER)的研究目标是建立钙粘蛋白表达变化或钙粘素转换模型与分化间充质干细胞(MSCs)在骨形成过程中遇到的不断演变的机械微环境之间的联系。MSCs在分化过程中既经历了细胞基质或整合素介导的力，又经历了细胞-细胞或钙粘附素介导的力。然而，尽管钙粘附素的调节对正常的骨形成是必不可少的，但通过钙粘附素的细胞-细胞力的作用在很大程度上被忽视了。“钙粘附素开关”规定，当骨髓间充质干细胞分化为骨形成细胞时，一个钙粘附素上调，另一个下调。这种转换与骨形成过程中不断变化的力学环境相平行：MSCs始于软骨髓(~1kPa)，并在坚硬的未矿化基质(10s Kpa)中分化为骨基质生成细胞。这项工作旨在将钙粘附素开关与MSCs不断变化的机械微环境联系起来。该方法结合使用了两种工具：电液动力(E-Jet)和3D全场牵引力显微镜(3D TFM)。E-Jet将在聚丙烯酰胺底物上形成蛋白质和刚性的图案，并能够操纵细胞-细胞和细胞-底物的作用力。3DTFM将测量作用力，从而定量地建立关系。细胞-细胞力在分化和骨形成中的影响在很大程度上被忽略了。这项工作的结果可能会导致骨疾病的新疗法，并更全面地了解骨和其他组织的组织发育。通过这项工作，细胞培养底物的3D TFM和E-Jet图案化等相对较新的技术将更容易为更广泛的科学界所接受。教育部分通过机构之间和跨学科的互动，侧重研究生培训和研究经验。这项研究还将被用来突出机械工程(ME)领域的广度，特别是针对女生校园中学(CMS)，目的是使这些和其他K-12年级的学生更容易接触到ME，否则他们可能因为对该领域的先入为主的概念而对ME不感兴趣。

The research objective of this EArly-Concept Grant for Exploratory Research (EAGER) is to establish the link between the changing cadherin expression, or the cadherin switch model, and the evolving mechanical microenvironment that differentiating mesenchymal stem cells (MSCs) encounter during bone formation. MSCs experience both cell-matrix, or integrin-mediated, and cell-cell, or cadherin-mediated, forces during differentiation. However, the role of cell-cell forces through cadherins has been largely neglected despite that cadherin regulation is essential to normal bone formation. The "cadherin switch" specifies that as MSCs differentiate in to bone forming cells, one cadherin is up regulated and another is down regulated. The switch parallels the changing mechanical environment during bone formation: MSCs begin in soft marrow (~1kPa) and differentiate into bone matrix-producing cells in stiff, unmineralized matrix (10s of kPa). This work aims to relate the cadherin switch to the changing mechanical microenvironment for MSCs. The approach uses a combination of two tools: Electrohydrodynamic (E-Jet) and 3D, full-field traction force microscopy (3D TFM). E-Jet will pattern both proteins and stiffness on polyacrylamide substrates and enable manipulation cell-cell and cell-substrate forces. 3D TFM will measure the forces thus quantitatively establishing the relationship. The influence of cell-cell forces in differentiation and bone formation has largely been neglected. Results from this work could lead to new treatments for bone diseases and a more complete understanding of tissue development both for bone and for other tissues. Through the work the relatively new techniques, 3D TFM and E-Jet patterning of cell culture substrates, will be made more accessible to a broader scientific community. The educational component focuses on graduate student training and research experiences through interactions between institutions and across disciplines. The research will also be used to highlight the breadth of the field of Mechanical Engineering (ME) specifically for the Campus Middle School (CMS) for Girls, with the goal of making ME more accessible to these and other K-12 students who otherwise may not be interested in ME based on preconceptions of the field.