Zebrafish hearts can regenerate by replacing damaged tissue with new cardiomyocytes. Although the steps leading up to the proliferation of surviving cardiomyocytes have been extensively studied,... Show moreZebrafish hearts can regenerate by replacing damaged tissue with new cardiomyocytes. Although the steps leading up to the proliferation of surviving cardiomyocytes have been extensively studied, little is known about the mechanisms that control proliferation and redifferentiation to a mature state. We found that the cardiac dyad, a structure that regulates calcium handling and excitation-contraction coupling, played a key role in the redifferentiation process. A component of the cardiac dyad called leucine-rich repeat-containing 10 (Lrrc10) acted as a negative regulator of proliferation, prevented cardiomegaly, and induced redifferentiation. We found that its function was conserved in mammalian cardiomyocytes. This study highlights the importance of the underlying mechanisms required for heart regeneration and their application to the generation of fully functional cardiomyocytes. Show less
Vliet, P. van; Boer, T.P. de; Heyden, M.A.G. van der; Tamer, M.K. el; Sluijter, J.P.G.; Doevendans, P.A.; Goumans, M.J. 2010
In the past years, cardiovascular progenitor cells have been isolated from the human heart and characterized. These cells can differentiate into cardiomyocytes, smooth muscle cells and endothelial... Show moreIn the past years, cardiovascular progenitor cells have been isolated from the human heart and characterized. These cells can differentiate into cardiomyocytes, smooth muscle cells and endothelial cells and are therefore of great value for investigation of the mechanisms that drive progenitor cell function and plasticity, drug testing and, potentially, therapeutical purposes. In this respect, most studies have focused on enhancing differentiation with chemicals or growth factors, or co-culture with other cell types. Although they have revealed important mechanisms, protocols need to be established that exclude the need for such factors when one considers using progenitor cells to repair the human heart. In this study we tested whether we could induce cardiomyogenic differentiation of human cardiomyocyte progenitor cells (CMPCs) by altering their membrane potential. We induced hyperpolarization in CMPCs by either co-culturing them with a K(ir)2.1-overexpressing cell line or by overnight culture in medium containing low potassium concentrations. Hyperpolarization led to increased intracellular calcium concentrations, activation of calcineurin signaling, increased cardiac-specific gene and protein expression levels and, ultimately, to the formation of spontaneously beating cardiomyocytes. Thus, hyperpolarization is sufficient to induce differentiation of CMPCs, thereby revealing a novel mechanism for cardiomyogenic differentiation of heart-derived progenitor cells. Show less
Vliet, P. van; Smits, A.M.; Boer, T.P. de; Korfage, T.H.; Metz, C.H.G.; Roccio, M.; ... ; Goumans, M.J. 2010
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... Show moreIn 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. Show less
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... Show moreCardiomyocyte 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. Show less
