Human cardiomyocyte progenitor cell-derived cardiomyocytes display a maturated electrical phenotype

Cardiomyocyte progenitor cells (CMPCs) can be isolated from the human heart and differentiated into cardiomyocytes in vitro. A comprehensive assessment of their electrical phenotype upon differentiation is essential to predict potential future applications of this cell source. CMPCs isolated from human fetal heart were differentiated in vitro and examined using immunohistochemistry, Western blotting, RT-PCR voltage clamp and current clamp techniques. Differentiated cultures presented up to 95% alpha-actinin positive cardiomyocytes. Adherens junction and desmosomal proteins beta-catenin, N-cadherin, desmin and plakophilin2 were upregulated. Expression levels of cardiac connexins were not affected by differentiation, however Cx43 phosphorylation was increased upon differentiation, accompanied by translocation of connexins to the cell border. RT-PCR analysis demonstrated upregulation of all major cardiac ion channel constituents during differentiation. Patch clamp experiments showed that cardiomyocytes had a stable resting membrane potential of -73.4 +/- 1.8 mV. Infusion of 1 mM BaCl2 resulted in depolarization to -59.9 +/- 2.8 mV, indicating I-K1 channel activity. Subsequent voltage clamp experiments confirmed presence of near mature I-Na, I-Ca,I-L and I-K1 current densities. Infusion of the I-Kr, blocker Almokalant caused prolongation of the action potential by 40%. Differentiated monolayers were not spontaneously contracting in the absence of serum, but responded to field stimulation, displaying adult ventricular-like action potentials. Human fetal CMPC-derived cardiomyocytes have a homogenous and rather mature electrical phenotype that benefits to in vitro physiology and pharmacology. In the context of cardiac repair, their properties may translate into a reduced pro-arrhythmic risk and enhanced electrical integration upon transplantation. (C) 2009 Elsevier Inc. All rights reserved.Signal transduction in aging related disease

Foetal and adult cardiomyocyte progenitor cells have different developmental potential

In the past years, cardiovascular progenitor cells have been isolated from the human heart and characterized. Up to date, no studies have been reported in which the developmental potential of foetal and adult cardiovascular progenitors was tested simultaneously. However, intrinsic differences will likely affect interpretations regarding progenitor cell potential and application for regenerative medicine. Here we report a direct comparison between human foetal and adult heart-derived cardiomyocyte progenitor cells (CMPCs). We show that foetal and adult CMPCs have distinct preferences to differentiate into mesodermal lineages. Under pro-angiogenic conditions, foetal CMPCs form more endothelial but less smooth muscle cells than adult CMPCs. Foetal CMPCs can also develop towards adipocytes, whereas neither foetal nor adult CMPCs show significant osteogenic differentiation. Interestingly, although both cell types differentiate into heart muscle cells, adult CMPCs give rise to electrophysiologically more mature cardiomyocytes than foetal CMPCs. Taken together, foetal CMPCs are suitable for molecular cell biology and developmental studies. The potential of adult CMPCs to form mature cardiomyocytes and smooth muscle cells may be essential for cardiac repair after transplantation into the injured heart.Signal transduction in aging related disease