BIOMECHANICS OF STEM CELLS

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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.