Experimental tools and mathematical models to study electrical-mechanical properties of spatial-temporal patterns in cultured cardiac cells

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The proposed study is aimed at understanding the link between the biomechanical and electrical properties of cultured cardiac cells and their role on autonomous electrical activity. The high level of complexity of cardiomyocyte (electrically-active cardiac cells) dynamics needs integration of numerous approaches and techniques to uncover the multiscale changes occurring in culture and the functional impact on electrical activity at both the cell and multicellular levels. Here, we proposed a project involving bioinstrumentation development, image acquisition techniques as well as analysis, and modelling works summarized below to better understand the effects of cell deformation on bioelectric characteristics and spatio-temporal electrical self-organization.1. Develop a combined approach for culture in our bioreactor and data acquisition with electrical and mechanical stimulations for non-terminal experiments and sub-cellular study of electrophysiological properties We have developed a bioreactor for culture of CMs that provided programmed electrical and mechanical stimuli to cells. In parallel, an acquisition system to record fluorescence changes (for example for intracellular calcium transient with fluo-4) to visualize the effects of electrical stimulation and mechanical deformation of the cells in post-culture has been developed. Three important limitations of the proposed combined systems exist at this stage: displacement of the field of view (FOV) under study when stretched, jitter due to linear stepper motors control, and impossibility to acquire fluorescence data while stretching. We propose to correct these limitations by integrating a feedback control motion to stabilize the FOV and to modify the bioreactor stretching electronic circuit to microstepping.2. Study of the spatial-temporal autonomous electrical activity of isotropic and patterned cardiomyocyte monolayers following culture on elastic substrates:Experiments by our group present varying time-dependent behaviors when recording at a single site. The temporal activity can be transiently or permanently affected following acute electrical or mechanical stimulation. However, it is clear that the changes seen locally are limited to explain what could be variation in the spatial-temporal dynamics. We thus propose to study the stability of spatio-temporal activity of topographically patterned cardiomyocytes. More precisely we will study self-organized activity on electrically-coupled CMs and its stability is perturbed by acute stretch to understand the role of cell deformation.3. Evaluate, with a mathematical model, the role of heterogeneous dispersion of intrinsic frequencies of autonomous electrical activity on global activity of patterned and unpatterned monolayersEvaluate, with a mathematical model, the role of heterogeneous dispersion of intrinsic frequencies of autonomous electrical activity on electrical self-organization. CMs isolated from neonatal hearts can be either autonomous or non-autonomous cells. In cell culture, initial seeding is random such that how these two populations are distributed within the monolayer is unknown. We propose to look at the effects of having mixture of these two populations on spatio-temporal activity based on a novel approach of mathematical modeling and study how cell topography can influence the autonomous activity. The high level of complexity of CM dynamics needs integration of these innovative approaches and techniques to uncover the multiscale changes occurring in culture and the functional impact on electrical activity at both the cell and multicellular levels.