Induced pluripotent stem cell-derived cardiomyocytes

Abstract

Abstract Until several years ago, for in\xa0vitro studies scientists have mostly employed animal-derived cardiomyocytes to investigate the following: (1) the excitation-contraction-coupling (ECC) machinery; (2) The effects of disease-related pathological conditions on the ECC machinery; (3) Cardiomyocyte bioenergetics and metabolism; (4) Developmental changes in the ECC machinery in cardiomyocytes obtained from animals at different ages; (5) Inotropic and chronotropic modulation by autonomic agonists and antagonists; (6) Arrhythmia models and antiarrhythmic efficacies of different drugs; (7) Cardiac toxicity of approved drugs and new chemical entities. Although these experimental models have vastly expanded our knowledge regarding cardiac function under physiological and pathophysiological conditions, in many cases, key ECC characteristics of these animal models differ from those of the human heart. A new thrilling era of cardiac (but not only) research has emerged in the late 90s, early 2000s with the fundamental discovery by Thomson, Itskovitz, and coworkers that pluripotent embryonic stem cells (ESCs) can be derived from the inner cell mass of human blastocytes. These ESCs demonstrated the two fundamental features of stem cells: self-renewal and the ability to differentiate into the three germ layers, endoderm, mesoderm, and ectoderm. This pivotal discovery was received by the scientific community with world-wide enthusiasm, thus embracing the concept of using human ESC-derived cardiomyocytes (ESC-CMs) for cardiac muscle regeneration; for example, replacing dead cardiac tissue following myocardial infarction following coronary artery occlusion. Nonetheless, in addition to major ethical concerns regarding the use of cardiomyocytes generated from (destroyed) human embryos, other drawbacks are the limited supply and the need to use immunosuppression upon ESC-CMs transplantation in experimental animals and human hearts. Nonetheless, the use of human ESC-CMs promptly became the focus of many laboratories worldwide, for both basic research and clinical applications, aiming for example at postmyocardial infarction tissue regeneration. In 2006/7 the scientific community was overwhelmed (again) by the breakthrough discovery of Takahashi and Yamanaka who discovered the four transcription factors critical for cells’ pluripotency, thus providing the unique opportunity to reprogram any somatic cell into human-induced pluripotent stem cell (iPSCs). Once human iPSCs are generated, they can be differentiated into almost any cell type, such as cardiomyocytes, neurons, pancreatic cells, and skeletal muscle cells. The ability to generate almost any cell type by reprogramming our own somatic cells (e.g., skin fibroblasts, blood cells, hair keratinocytes) has truly revolutionized the scientific world, with far-reaching implications that are beyond the scope of this chapter. To acquaint the readers with the magical world of iPSCs into cardiomyocytes (iPSC-CMs), this chapter addresses the following topics: (1) Differentiating iPSC-CMs; (2) Functional properties of immature iPSC-CMs; (3) Experimental procedures for promoting maturation of immature iPSC-CMs.