Structural remodeling and functional maturation of stem cell-derived cardiomyocytes in novel 3D microprinted scaffolds.

• Applicant: Nina Ullrich, Ph.D.
• Subject Area: Anatomy and Physiology ; Cell Biology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 417543243

Stem cell-derived cardiomyocytes raise new hope for myocardial repair and may serve to replace diseased cardiomyocytes to compensate for functional loss in the failing heart. At the current degree of differentiation, these cells present a rather immature phenotype, characterized by undefined cellular structure and disordered myofilament arrangement compared to adult cardiomyocytes, inefficient Ca handling and spontaneous contractile activity, strong hallmarks of immaturity, which lead to fragile and instable Ca signaling and favor the development of undesired electrical activities in these cells. The structural and functional deficiencies reminiscent of premature native myocytes limit successful integration into host myocardium and call for new strategies to enhance maturation before these cells may be used in cell therapeutic approaches. The great challenge is to identify the specific requirements and parameters of stem cell-derived cardiomyocytes that trigger further cardiogenic maturation. Here, we propose the hypothesis that myocyte shape influences function, thereby determining cardiac features. In analogy to the shape of adult cardiomyocytes, we have designed novel rectangular-shaped 3D scaffolds for single cell culture to evaluate the influence of a particular cell shape and geometry on cardiomyocyte function. In preliminary experiments, reshaping stem cell-derived cardiomyocytes in cuboid scaffolds induced significant structural reorganization of the myofilaments and enhanced the efficiency of Ca handling. Based on these exciting new data, we propose two causally linked experimental strategies to provide deep insight into the structural and functional changes occurring upon cell growth in specific shapes. In the first aim, we investigate the exact trigger mechanisms that lead to structural remodeling and try to answer to the question whether interaction with scaffold walls (cuboidal growth in 3D) or just cellular reorientation in a rectangular shape with precise long axis formation (growth in 2D) are required to initiate the observed strong remodeling processes. Outside-in signaling analysis may provide further insight into the genetic control of cell architecture and formation of cardiac-specific microdomains, such as t-tubules and intercalated disks. The second part of the project proposal aims to elucidate the mechanisms that lead to enhanced Ca handling by structural remodeling. In particular the hypothesis will be tested that changes in cell microarchitecture influence the interaction of the Ca influx and Ca release pathways that critically control excitation-contraction coupling in stem cell-derived cardiomyocytes. Overall, the major goal of this project is to define the mechanisms that lead to stable and efficient Ca signaling in order to reduce the risk of arrhythmogenic electrical activity in these novel cardiomyocytes and to make them better suited for future clinical applications.

• DFG Programme: Research Grants