Regulatory roles of variable mechanical stimuli in cell function

大多数细胞类型对其所处的物理环境高度敏感，作用于它们的生理力在许多调节细胞功能中起主导作用。这种机械传导总是用单调的机械刺激来研究；然而，体内的细胞暴露在不规则变化的刺激下。两个例子包括呼吸和循环。最近，我们发现证据表明，在肺泡上皮II型细胞中，无论是在培养中还是在体内，拉伸的生理变异性的存在从根本上改变了这些细胞的分泌反应。细胞通过粘附分子和细胞骨架（CSK）感知外部机械力。因此，假设通过CSK，大多数（如果不是全部）基本细胞功能也会对机械刺激的变异性敏感是可行的。进化的力量应该有利于那些能够适应和利用现有可变性的结构。因此，我们的中心假设是，通常存在于体内的机械刺激的生理水平变异性在许多基本细胞功能中具有基本的调节作用。机械转导的这一方面在细胞和组织培养研究中被忽视了。因此，一个主要的挑战是确定我们的发现是特异性的上皮细胞，还是这种现象普遍代表了机械生物学的主要范式转变。为了验证这一假设，我们将使用四种不同的体外细胞系统：肺上皮细胞、血管内皮细胞和平滑肌细胞以及皮肤或肺成纤维细胞。我们将在体外测试这些细胞系统的各种结果，同时逐渐改变机械刺激的可变性。具体来说，我们的目的是确定可变拉伸（VS）模式对特定细胞因子、酶和结构ECM蛋白的转录、翻译和分泌的影响。我们还将评估VS对细胞分裂、生长和凋亡等基本功能的影响，以揭示不同器官系统之间的普遍机制。最后，为了确定VS对代谢的可能影响，我们将评估VS过程中活性氧（ROS）的产生。为了阐明VS诱导现象的机制，我们将在VS过程中沿着机械转导途径使用各种抑制剂，同时对CSK的成分和组织进行成像。然后，我们将开发新的CSK网络模型，以更好地理解从粘附位点通过CSK到细胞核的机械力传递。如果我们的假设是正确的，那么除了许多基本的细胞功能外，酶、细胞因子和ECM构件的产生和分泌都会受到VS的影响。此外，VS也可能影响

Most cell types are highly sensitive to their physical environment and physiological forces acting on them play a dominating role in many regulatory cell functions. Such mechanotransduction is always studied using monotonous mechanical stimuli; however, cells in the body are exposed to irregularly varying stimuli. Two examples include breathing and circulation. Recently, we found evidence that in alveolar epithelial type II cells, both in culture and in vivo, the presence of physiological variability in stretch fundamentally alters the secretory response of these cells. Cells sense external mechanical forces via adhesion molecules and the cytoskeleton (CSK). It is thus feasible to assume that through the CSK, most if not all basic cell functions would also be sensitive to variability in mechanical stimuli. Evolutionary forces should favor structures that can adapt to and take advantage of existing variability. Accordingly, our central hypothesis is that physiological levels of variability in mechanical stimuli that are normally present in the body have fundamental regulatory roles in many basic cell functions. This aspect of mechanotransduction has been overlooked in cell and tissue culture studies. A major challenge is therefore to establish whether our findings are specific to epithelial cells or the phenomenon is general representing a major paradigm shift in mechanobiology. To test this hypothesis, we will use four different in vitro cell systems: lung epithelial cells, vascular endothelial and smooth muscle cells and skin or lung fibroblasts. We will test various outcomes in these cell systems in vitro while gradually changing variability in mechanical stimuli. Specifically, we aim to determine the effects of variable stretch (VS) pattern on transcription, translation and secretion of specific cytokines, enzymes and structural ECM proteins. We will also assess the effect of VS on basic cell functions such as division, growth and apoptosis to uncover universal mechanisms among different organ systems. Finally, to determine the possible effects of VS on metabolism, we will assess the generation of reactive oxygen species (ROS) during VS. To shed light on the mechanisms of VS-induced phenomena, we will employ various inhibitors along the mechanotransductory pathway during VS while imaging the constituents and organization of the CSK. We will then develop novel network models of the CSK to better understand mechanical force transmission from adhesion sites through the CSK to the nucleus. If our hypothesis is correct, then besides many basic cell functions, the production and secretion of enzymes, cytokines and ECM building blocks will all be affected by VS. Additionally, VS may also influence ROS which play a crucial role in the pathogenesis of several major diseases including atherosclerosis, neuro-degenerative diseases, metabolic disorders, aging and cancer. Thus, our project - the first to apply VS patterns to probe cell functions - could have far reaching transformative implications for the understanding of how cells work in real living tissues and hence for biology and medicine. This research could thus influence the way scientists including biologists, physiologists, physicists as well as clinicians think about the cell.