Cardiac muscle | EPFL Graph Search

Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The cardiac muscle (myocardium) forms a thick middle layer between the outer layer of the heart wall (the pericardium) and the inner layer (the endocardium), with blood supplied via the coronary circulation. It is composed of individual cardiac muscle cells joined by intercalated discs, and encased by collagen fibers and other substances that form the extracellular matrix. Cardiac muscle contracts in a similar manner to skeletal muscle, although with some important differences. Electrical stimulation in the form of a cardiac action potential triggers the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum. The rise in calcium causes the cell's myofilaments to slide past each other in a

Mechanoelectric feedback in cardiomyocyte monolayers and whole hearts in response to stretch

Barbara Murienne

Stretch has been shown to induce electrophysiological changes in the whole heart and cardiomyocyte monolayer models. However, the mechano-electric mechanisms responsible for these changes are still not completely understood. In this project, micropatterned cardiomyocyte monolayers were anisotropically stretched in order to investigate two hypotheses: the increase in action potential duration (APD) and decrease in conduction velocity (CV) in response to stretch and the effect of stretch-activated channel blockers on these electrophysiological changes. The results obtained showed a decrease in APD in response to stretch in all experiments. Regarding CV, a decrease during propagation in the longitudinal direction (along the long axis of the aligned cardiomyocytes) and an increase during propagation in the transverse direction (along the short axis of the aligned cardiomyocytes) were observed in response to stretch. These electrophysiological changes did not seem altered by the presence of 70 μM and 85 μM streptomycin. However, the results for the APD have to be considered with caution due to limitations of the data analysis procedure

2009

Mathematical modeling and numerical simulation of excitation-contraction phenomena in the heart

In this Master thesis we aim at studying some physiological and computational aspects of the excitation-contraction mechanisms in the heart muscle. This phenomenon exhibits many complexities at different spatio-temporal scales. The relevance and applicability of several recent phenomenological and physiologically detailed ionic models will be assessed. The choice of the treated models is based on an equilibrium between results that manage to reproduce correctly the complexity of the cardiac electrophysiology and a weak computational cost in order to solve the large set of ODEs which describe the dynamics of that ionic model. The preferred models include a large part of the more recent electrophysiological discoveries and understandings (e.g. L-type calcium and ryanodine channels) in order to reproduce at best the electrical conduction in the human cardiac tissue based on different experimental or computational measurements. According to these previous remarks, we will perform a thorough testing and quantitative comparison of these models and mechanical activation mechanisms in the framework of the LifeV finite element library. In a second step, a recent model for the description of crossbridge dynamics will be implemented. The importance of using good ionic models makes sense to identify correctly the possible influence on the muscle mechanics activation, which enable the heart to pump blood throughout the entire circulatory system.

2013

Isolation and characterisation of a porcine cardiac adherent cell population from heart biopsies

Christelle Hasselmann

Cardiac diseases represent the major cause of mortality in the Western world. The discovery of the promising human Cardiac Adherent Proliferating (CAP) cells for a potential cardiac cell therapy by the Tissue Engineering group induced the need of a reliable animal model. The aim of the project is to identify a porcine cardiac cell population having similar characteristics as human CAP cells. Here a protocol for isolating cells from porcine heart biopsies have been established, as well as the in vitro expansion method. Additionally, the characterization of those expanded porcine cardiac cells was accomplished by growth kinetics study, FACS analysis, multilineage potential and myogenic induction assays. In this study we identified a not yet described porcine cardiac adherent cell population directly isolated from biopsies within the inner right ventricle. With almost

5\times {10}^{7}

expanded cells after 30 days in culture, porcine cardiac cells present a high rate of proliferation in vitro. Porcine cardiac cells maintain a swirl-like pattern until 5-6 days in culture, and become fibroblast-like with a parallel organization when confluent. FACS analysis indicated that porcine cells are mainly CD90+ in opposite to human CAP cells. Both species show a similar CD45- and CD44+ profile. The multilineage assay showed no histological differentiation into fat, bone and cartilage on porcine cardiac cells like on human CAP cells. However gene expression analysis on porcine cardiac cells indicated that aP2 was upregulated in population undergoing an adipogenic induction, as well as osteopontine expression in osteogenic induction population. Porcine cardiac cell myogenic induction potential was tested on C2C12 myogenic mouse cells. The mouse cells differentiated in muscle in vitro thanks to the influence of those cardiac cells. Both cell populations have similar characteristics and the main distinction is the different CD90 expression profile. Those results encourage to realise additional studies, to confirm that those isolated cells could be a reliable model of human CAP cells.

2009

Isolation and characterisation of a porcine cardiac adherent cell population from heart biopsies

Christelle Hasselmann

5\times {10}^{7}

2009