Effect of endothelial cell organisation on hiPSC-CM maturation in a cardiac micro-tissue model

Introduction

Over the past decade, the development of robust protocols for the generation of cardiomyocytes derived from human induced pluripotent stem cell (hiPSC-CMs) has considerably facilitated the study of genetic cardiomyopathies and the screening of new therapeutic molecules for cardiac diseases. One of the major limitations of this model is the lack of mature contractile function of hiPSC-CMs compared to adult human cardiomyocytes. Numerous studies have shown that the function of hiPSC-CMs can be improved by using multiple cardiac cell types in 3D co-culture to mimic the in vivo cell environment. However, the potential impact of the relative spatial organization of the different cell types inside the cardiac microtissue is still poorly understood.

Objective

The aim of this study is to evaluate the effect of endothelial cell organization on hiPSC-CM function within a cardiac microtissue model.

Method

After derivation of hiPSC-CMs from hiPSCs using a cardiac differentiation protocol, a 3D co-culture model called a “spheroid” is established by self-aggregation of different cardiac cell types (70% hiPSC-CM + 15% cardiac fibroblasts + 15% endothelial cells). Two different spheroid models with the same composition but with different organization (self-organized: endothelial cells homogeneously distributed or constrained: endothelial cells are concentrated to form a core at the center of the spheroid) will be functionally compared by assessing their contractility and kinetics of calcium transients. Molecular and cellular analyzes to identify the origin of the observed differences will also be performed using RT-qPCR and immunohistochemistry.

Results

Contractile analysis shows a significant increase in the amplitude of contraction of spheroids with the constrained organization (core of endothelial cells) to the self-organized spheroids (homogeneous distribution of cells). Differences in calcium kinetic parameters such as the time to reach the calcium peak or the time for calcium transient decay are also observed between the two conditions. Furthermore, immunohistochemistry and RT-qPCR analyses revealed an improved cell viability and maturation of hiPSC-CMs, demonstrating the positive effect of preforming an endothelial cell core on the function and maturation of this 3D model.

Conclusion

The development of this model highlights the important role of cell organization in the enhanced function of hiPSC-CMs enabled by 3D co-culture of cardiac cells.