BIOMECHANICS OF STEM CELLS

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目及 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 对于中心来说，它不一定是研究者的机构。 该项目的目的是研究干细胞的机械特性。我们将使用一种将实验与有限元模拟相结合的新方法来识别干细胞的机械特性，例如杨氏模量和极限强度。实验将涉及在施加抽吸压力下对干细胞进行微吸管抽吸（MPA）。随后，将使用商业有限元软件 ABAQUS 对吸气过程进行模拟。我们将尝试干细胞的各种候选粘弹性材料模型，例如麦克斯韦模型、广义麦克斯韦模型、开尔文-沃伊特模型或标准线性固体（SLS）模型。目标是找到最接近干细胞材料反应的模型（通过 MPA 实验测量），以及模型参数的一组最佳值。我们将通过调整 FEM 模拟中使用的模型来实现这一点，直到模拟的抽吸历史（抽吸体积投影作为时间的函数）与实验观察到的相匹配。为了计算模型参数的总体平均值，将对对应于三种细胞系的大量干细胞进行抽吸实验：CD34+细胞（通常用于心脏治疗）、神经干细胞（NSC）和骨髓基质细胞（mBMSC）。对于每个实验，都需要进行大量的有限元模拟来微调模型及其参数。因此，需要超级计算资源来成功执行该项目。我们建议在该项目中在 PSC 的 Pople 上使用 ABAQUS，因为我们之前有使用 ABAQUS 并使用 Pople 进行 CFD 和 FSI 模拟的经验。我们将提供我们自己的 ABAQUS 许可证。此外，ABAQUS 的并行执行可以同时使用线程和 MPI 任务，我们将确定哪种模式在 Pople 上效果最好。因此，我们希望为该项目请求 Pople 提供 30,000 个 SU 的启动资金。这很可能不足以完成该项目，因此我们打算稍后申请研究拨款。我们还想请求 ASTA 支持该项目，帮助找出在 Pople 上运行 ABAQUS 模拟的最有效方法。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The aim of this project is to investigate the mechanical properties of stem cells. We shall use a novel approach that combines experiments with FEM simulations to identify mechanical properties of stem cells such as the Young's modulus and ultimate strength. The experiments will involve micropipette aspiration (MPA) of stem cells under an applied suction pressure. Subsequently, the aspiration process will be simulated using the commercial FEM software ABAQUS. We shall try various candidate viscoelastic material models for the stem cells, such as the Maxwell model, Generalized Maxwell model, Kelvin-Voigt model or Standard Linear Solid (SLS) model. The goal is to find the model that best approximates the material response of stem cells (as measured experimentally via MPA), together with a set of optimum values for the model parameters. We shall achieve this by tuning the model used in the FEM simulations until the simulated aspiration history (aspirated volume projection as a function of time) matches that experimentally observed. To compute population means of the model parameters, aspiration experiments will be performed on a number of stem cells corresponding to three cell lines: CD34+ cells (generally used for cardiac therapy), neural stem cells (NSCs) and bone marrow stromal cells (mBMSCs). For each experiment, a large number of FEM simulations need to be performed to fine tune the model and its parameters. Hence the need for supercomputing resources for the successful execution of this project. We propose to use ABAQUS on PSC's Pople for this project, as we have prior experience with ABAQUS and using Pople for CFD and FSI simulations. We shall provide our own ABAQUS license. Furthermore, the parallel execution of ABAQUS can use both threads and MPI tasks, and we shall determine which mode works best on Pople. Thus, we would like to request a startup grant on Pople with 30,000 SUs for this project. This will most likely be insufficient for completing the project and so we intend to apply for a research allocation later. We would also like to request ASTA support for this project, for help in figuring out the most efficient way to run our ABAQUS simulations on Pople.