The impact of mechanosensing on dendritic cell biology

生物组织显示出与其功能相适应的各种化学和机械特性。一种这样的性质是组织的刚度，以组织弹性模量（E）的单位表示，如由其在机械应力下变形的固有阻力所定义的。在稳定状态下，免疫细胞如树突状细胞（DC）在体内巡逻，并经历范围从0.1至> 64千帕斯卡（kPa）的广谱组织硬度。从研究涉及改变组织机械特性的疾病（如纤维化和钙化）中获得的证据表明，细胞能够感知大的细胞外物理干扰。然而，在这些疾病模型中，组织机械张力的改变与复杂的生物学变化（如炎症和组织损伤）密切相关，排除了机械力及其对免疫系统影响的研究。拟议的研究计划的目的是了解细胞外机械力以及其他生物学特性（如营养和氧气可用性）如何影响免疫细胞的稳态和功能。我们提出了一个研究计划，旨在1。研究DCs中机械信号转导通路的特征; 2.研究免疫细胞在不同张力条件下的功能表现，以及其他生理参数，如氧气和营养浓度; 3.检查免疫细胞在机械应力下发生的转录和代谢变化。我们将采用由聚二甲基硅氧烷（PDMS）水凝胶包被的板组成的细胞培养系统来模拟对应于软粘膜和脑（<1kPa）、脂肪组织、脾、淋巴结和肝（2 - 5kPa）、骨髓（0.3 - 24.7kPa）和发炎的淋巴器官（50kPa）的生理张力。在我们的初步研究中，比较了一种生长在刚性基质与柔性基质上的骨髓源性免疫细胞（骨髓树突状细胞），确定了河马信号分子，具有PDZ结合基序（Taz）的转录共激活因子，作为一种重要的介质，在刚性张力条件下促进免疫细胞功能。因此，我们将研究张力和雅普/Taz信号传导对免疫细胞分化、功能和代谢的调节作用。 人体内不同的生理机械环境如何调节免疫细胞的发育和体内平衡尚不清楚。拟议的研究计划将为这种以前未被充分认识的生物相互作用提供新的见解。鉴于细胞生物学研究的一个基本方面涉及在弹性模量在MPa范围内的塑料器皿上进行组织培养，该弹性模量高于细胞在体内遇到的弹性模量，这项研究对回答生物学问题的体外系统的设计具有重要意义。

Biological tissues display diverse chemical and mechanical properties that are tailored to their functions. One such property is the stiffness of the tissue, expressed in the unit of tissue elastic modulus (E) as defined by its intrinsic resistance to deform under mechanical stress. Under steady state, immune cells such as dendritic cells (DCs) patrol the body and experience a wide spectrum of tissue stiffness, ranging from 0.1 to >64 kilo pascals (kPa). Evidence from studying diseases involving altered tissue mechanical properties, such as fibrosis and calcification, suggests that cells are capable of sensing large extracellular physical disturbances. However, in these disease models, alterations in tissue mechanical tension go hand in hand with complex biological changes such as inflammation and tissue damage, precluding the study of mechanical forces and their impact on the immune system in isolation. The objective of the proposed research program is to understand how extracellular mechanical force, together with additional biological properties such as nutrient and oxygen availability, influences immune cell homeostasis and function. We propose a research program that aims to 1. Characterize the mechanical signal transduction pathways in DCs; 2. Investigate how immune cells behave functionally under differential tension conditions, compounded to additional physiological parameters such as oxygen and nutrient concentrations; 3. Examine the transcriptional and metabolic alterations occurring within immune cells upon mechanical stress. We will employ a cell culturing system consisting of polydimethylsiloxane (PDMS) hydrogel-coated plates to mimic physiological tensions corresponding to soft mucosa and brain (<1kPa), adipose tissue, spleen, lymph nodes and liver (2-5kPa), bone marrow (0.3-24.7kPa), and inflamed lymphoid organs (50kPa). In our preliminary studies, comparison of a type of bone marrow-derived immune cells (bone marrow dendritic cells) grown on stiff vs compliant substrates identified the hippo signaling molecule, transcriptional coactivator with PDZ-binding motif (Taz), as one important mediator promoting immune cell function under stiff tension conditions. We will thus examine the role of tension and Yap/Taz signaling on the regulation of immune cell differentiation, function and metabolism. How diverse, physiological mechanical environments in the body regulate immune cell development and homeostasis is not known. The proposed research program will provide new insights into this previously underrecognized biological interaction. Given that a fundamental aspect of cell biology research involves tissue culturing on plastic wares with elastic modulus in the range of MPa, magnitudes higher than what the cells encounter in the body, this study has important implications on the design of in vitro systems in answering biological questions.