Building human myocardium in a dish
Within work package "Building human myocardium in a dish" our goal is to create engineered cardiac microtissue that can be used to better understand healthy and diseased cardiac physiology. In addition, the high throughput platform we are designing within this work package will serve as a tool for screening the effects of genetic, cellular and pharmaceutical therapies.
The heart is a complex organ which is composed of a diverse set of muscle and non-muscle cells embedded in a connective tissue matrix, the extracellular matrix (ECM). The cardiac ECM plays an important role in the contractility of the heart by forming an aligned or anisotropic network which provides cues for proliferation, differentiation, alignment and coupling of cell with each other and their environment, thereby providing contractile function. During pathogenesis of the heart, the composition and architecture of the ECM alters. The aligned ECM changes into a chaotic or isotropic organization which alters cardiac structure and function. Current therapies for heart disease focus on attenuating cardiac function although often with only a temporary beneficial effect, possibly caused by the chaotic organization of the ECM.
More insights in the changes of the cellular microenvironment and how this affects cardiac function in disease might lead to the improvement of therapies. Within the project “Myocardium in a dish” we we characterize the cardiac microenvironment in heart disease which can be implemented in 3D engineered cardiac tissue.
Characterization of cellular microenvironment and ECM was first performed on mouse hearts with pressure overload. Pressure overload was produced by constricting the transverse aorta (TAC) of mice and after 9 weeks the hearts were subjected to histological and biochemical analysis. The composition and architecture of the ECM combined with mechanical and cellular interactions were elucidated in these hearts. TAC hearts were characterized by induction of fibrosis and change in ECM organization into a more isotropic organization.
To study the effect of the change in ECM organization on the mechanical performance of mouse cardiac cells, microtissues were engineered using cells in microfabricated tissues gauges (microTUGs, Legant 2009). The 3D tissues consists of mouse cardiac muscle cells and non-muscle cells in a matrix with an biaxial or uniaxial constraints which allow manipulation of tissue organization, thereby mimicking healthy aligned and diseased chaotic cardiac tissue organization. Spontaneous contraction of the microtissues was followed for 7 days by video recordings and forces can be quantified from micropost displacement. So far, results show that tissue organization does not affect cell ratios and sarcomere maturation of the cardiac cells. Furthermore, the results indicate that the beating frequency decreased over time.
By implementing the effect of healthy vs diseased cellular microenvironment of the functionality of cardiomyocytes, more insight into heart pathobiology will be generated and facilitate in the optimization of new therapies for cardiac disease.