Abstract-Human embryonic stem (hES) cells can differentiate in vitro, forming embryoid bodies (EBs) composed of derivatives of all three embryonic germ layers. Spontaneously contracting outgrowths from these EBs contain cardiomyocytes (CMs); however, the types of human CMs and their functional properties are unknown. This study characterizes the contractions and action potentials (APs) from beating EB outgrowths cultured for 40 to 95 days. Spontaneous and electrical field-stimulated contractions were measured with video edge-detection microscopy. ␤-Adrenergic stimulation with 1.0 mol/L isoproterenol resulted in a significant increase in contraction magnitude. Intracellular electrical recordings using sharp KCl microelectrodes in beating EB outgrowths revealed three distinct classes of APs: nodal-like, embryonic atrial-like, and embryonic ventricular-like. The APs were described as embryonic based on the relatively depolarized resting membrane potential and slow AP upstroke. Repeated impalements of an individual beating outgrowth revealed a reproducible AP morphology recorded from different cells, suggesting that each outgrowth is composed of a predominant cell type. Complex functional properties typical of cardiac muscle were observed in the hES cell-derived CMs including rate adaptation of AP duration and provoked early and delayed afterdepolarizations. Repolarization of the AP showed a significant role for I Kr based on E-4031 induced prolongation of AP duration as anticipated for human CMs. In conclusion, hES cells can differentiate into multiple types of CMs displaying functional properties characteristic of embryonic human cardiac muscle. Thus, hES provide a renewable source of distinct types of human cardiac myocytes for basic research, pharmacological testing, and potentially therapeutic applications. R ecent studies have demonstrated that human embryonic stem (hES) cells in vitro can form embryoid bodies (EBs), some of which begin to spontaneously contract. [1][2][3] These beating EBs contain cardiac myocytes (CMs) based on the expression of cardiac-specific genes, cellular ultrastructure, and extracellular electrical activity. 1,3 Progress has been made in isolating cardiac myocytes from the mixed population of cells in the EB, 2 but no studies have yet defined what types of cardiac myocytes exist in the differentiating human EBs. In comparison, multiple types of mouse embryonic stem (mES) cell-derived CMs have been identified and characterized including nodal, atrial, ventricular, and Purkinje cells. However, mES cells have significant differences from hES cells such as variations in the stage-specific antigens and in the ability of leukemia inhibitory factor (LIF) to maintain the undifferentiated state. 4 Thus, differentiation of CMs from ES cells from the different species may be significantly different.Defining the types of CMs that can be obtained from hES cells is essential for further research using this model system and for any potential utilization of these cells for cell-based therapies. A var...

Cellular remodeling in heart failure results in decreased density of T-tubules and L-type Ca(2+) channels, which contribute to abnormal EC coupling.

Due to the biological complexity of the cardiovascular system, the animal model is an urgent pre-clinical need to advance our knowledge of cardiovascular disease and to explore new drugs to repair the damaged heart. Ideally, a model system should be inexpensive, easily manipulated, reproducible, a biological representative of human disease, and ethically sound. Although a larger animal model is more expensive and difficult to manipulate, its genetic, structural, functional, and even disease similarities to humans make it an ideal model to first consider. This review presents the commonly-used large animals—dog, sheep, pig, and non-human primates—while the less-used other large animals—cows, horses—are excluded. The review attempts to introduce unique points for each species regarding its biological property, degrees of susceptibility to develop certain types of heart diseases, and methodology of induced conditions. For example, dogs barely develop myocardial infarction, while dilated cardiomyopathy is developed quite often. Based on the similarities of each species to the human, the model selection may first consider non-human primates—pig, sheep, then dog—but it also depends on other factors, for example, purposes, funding, ethics, and policy. We hope this review can serve as a basic outline of large animal models for cardiovascular researchers and clinicians.

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