Tissue Engineered Model of Aging to Study the Role of Cellular Interdependence in Failing Tissues

尽管取得了进展，但衰老在现代生物学中仍是一个未解决的问题。许多导致细胞损伤的机制已经被确定，但生物体，即活着的动物和植物，可能不是因为细胞耗尽而死亡，而是因为更大规模的失败。细胞的衰竭扩散为组织、器官的衰竭，并最终导致整个生物体的衰竭。这个项目关注的是这种有序崩溃的第一个中间步骤：从细胞到组织的衰竭扩散。为此，该项目将从理论上和实验上确定细胞间复杂相互作用在衰老组织中的作用，利用组织工程策略独立控制年龄和细胞相互作用。实验将辅以数学模型和计算机模拟，得出死亡率曲线（随着年龄增长的死亡概率图）和这些组织的预期寿命。此外，该项目将能够量化细胞尺度老化过程与源于更大规模相互作用效应的老化过程的相对重要性。从更广泛的影响来看，老龄化影响到每个人。随着预期寿命的稳步增长，迫切需要更好地了解衰老背后的原理，以找到减少与年龄有关的疾病的方法。该项目将为科学界和医学界在涉及衰老的多个尺度上提供新的视角，为延缓或逆转衰老的新方法铺平道路，并帮助实现更健康的老年。研究结果将传播给广泛的受众，从中学生到本科生和研究生，以及当地社区，特别强调STEM领域中代表性不足的群体。活动包括为中学女生举办的讲习班、为高中生举办的地区科学展览项目以及在当地医疗中心举办的研讨会。尽管存在许多关于细胞损伤的理论，但很少有人知道微观故障如何级联到组织，器官和最终生物体的宏观故障。该项目的目标是通过理论和实验建立衰老组织中细胞之间复杂的相互依赖和相互作用的作用，将微观细胞失败与宏观衰老表现联系起来。根据来自研究人员实验室的强有力的初步数据，他们假设衰老，即随着实际年龄的增长而死亡的可能性增加，是由于细胞相互依赖的网络上的失败，而不是一系列孤立的细胞失败。为了验证这一假设，该项目的目标是：1)制造由不同密度（老年和年轻）心脏组织的单一和多种细胞类型（心脏成纤维细胞、心肌细胞和内皮细胞）组成的3D工程心脏组织；2)将组织老化一个月，无论有无氧化应激，同时测量组织和细胞群体的存活统计数据；3)使用详细的分析理论对相互作用的作用进行推论。具体来说，计算模型研究了边缘权重由扩散方程和一级反应动力学决定的空间相互依赖网络。节点的失效是随机的，这取决于它们与其他节点的相互作用，就像渗流一样扩散。计算框架将为提出的实验生成可测试的假设，作为回报，实验测量将约束模型参数。项目发现有可能通过引入一种全新的观点来改变衰老研究，即衰老是任何（生命或非生命）系统的普遍属性，这些系统具有足够数量的组件，这些组件强烈依赖于彼此来执行其微观功能。此外，这种观点第一次使我们能够量化和模拟老化的进程，给定一定的相互依赖网络结构来预测一个相互依赖的系统应该如何以及何时灾难性地崩溃。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。

Though progress has been made, aging remains an unsolved problem in modern biology. A number of mechanisms that lead to cell damage have been identified, but organisms, i.e., living animals and plants, presumably die not because they run out of cells, but because of failures of much larger scale. Cellular failures spread into failure of tissues, organs and ultimately the organism. This project focuses on the first intermediate step of this ordered collapse: the spread of failure from cells to tissues. To this end, the project will theoretically and experimentally establish the role of complex interactions between cells in aging tissues, using tissue engineering strategies to independently control both age and cell interactions. Experiments will be supplemented by mathematical models and computer simulations that will output mortality curves (plots of probability of death with increasing age) and life expectancies of these tissues. Furthermore, the project will be able to quantify the relative importance of cellular scale aging processes compared to those stemming from larger scale interaction effects. In view of broader impacts, aging affects everyone. With steadily increasing life expectancy, there is an immediate need to better understand principles underlying aging to find ways to decrease age-related diseases. This project will offer a fresh view to the scientific and medical community on the multiple scales involved in aging, paving the way for new approaches to delay or reverse aging and help attain healthier old ages. The research findings will be disseminated to a broad audience, from middle school to undergraduate and graduate students, and to the local community, with specific emphasis on underrepresented groups in STEM fields. Activities include workshops for middle school girls, regional science fair projects for high school students and seminars at a local medical center.Although there exist a number of theories on cell damage, very little is known about how microscopic failures cascade to macro scale failure of tissues, organs and ultimately the organism. The goal of this project is to bridge microscopic cell failure to macroscopic manifestations of aging, by theoretically and experimentally establishing the role of complex interdependence and interactions between cells in aging tissues. Based on strong preliminary data from the investigators' labs, it is hypothesized that aging, defined in terms of an increased probability of death with chronological age, is due to failures cascading through an interdependent network of cells, rather than a series of isolated cell failures. To test this hypothesis, the aims of this project are to 1) Fabricate 3D engineered heart tissues consisting of varying densities of (aged and young) single and multiple cell types of the heart tissue (cardiac fibroblasts, cardiomyocytes and endothelial cells); 2) Age the tissue for a month, both with and without oxidative stress, while measuring the survival statistics of a population of tissues and cells within; and 3) Make inferences regarding the role of interactions using a detailed analytical theory. Specifically, the computational model studies spatial interdependence networks whose edge weights are determined by the diffusion equation and first order reaction kinetics. The nodes fail stochastically depending on their interaction with others, in a percolation-like spread. The computational framework will generate testable hypotheses for the proposed experiments, and in return, experimental measurements will constrain the model parameters. Project findings have the potential to transform aging research by introducing an entirely new view that aging is a universal attribute of any (living or non-living) system that has a sufficient number of components that strongly depend on one other to carry out their microscopic functions. Furthermore, this view enables, for the first time, the ability to quantify and simulate the progression of aging, given a certain interdependence network structure to predict how and when an interdependent system should be expected to catastrophically collapse.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.