β1- and β2-adrenoceptor responses in cardiomyocytes derived from human embryonic stem cells:: comparison with failing and non-failing adult human heart

Background and purpose: Characterization of human embryonic stem cell-derived cardiomyocytes (hESC-CM) in relation to adult myocytes is essential for their future use in transplantation or as a model system. The beta-adrenoceptor pathways, which are known to be effective early in hESC-CM development, are of major importance because of their control of rate and force of beating, arrhythmia generation and apoptosis/necrosis. We have therefore performed detailed pharmacological analysis of the b-adrenoceptor responses in developing hESC-CM. Experimental approach: hESC-CMs were differentiated from H7 ESCs and studied up to 79 days of differentiation. Rate of beating and time course of contraction and relaxation were measured in superfused preparations. Key results: Responses to the mixed beta(1)- and beta(2)-adrenoceptor agonist isoprenaline were evident from day 10 to day 79. Stability of the responses during an application, for repeated applications on the same experimental day and over the time of development, was determined. Concentrations for half-maximal response (12.9 nM) were similar to those from adult human heart, but closer to those obtained from failing rather than normal ventricle. Acceleration of both contraction and relaxation was quantitatively similar to that in adult ventricular myocytes, as was sensitivity to muscarinic inhibition. Use of specific antagonists showed that both beta(1)- and beta(2)-adrenoceptors contributed to contractile responses, as seen with adult myocytes. Conclusions and implications: These data show the compatibility of hESC-CM with adult human myocardium in terms of beta-adrenoceptor response. The experiments described here also confirm the utility of the hESC-CM preparation for detailed pharmacological analysis.