Project description:In this study we have compared functional and molecular properties of highly purified murine induced pluripotent stem (iPS) cell- and embryonic stem (ES) cell-derived cardiomyocytes (CM). In order to obtain large amounts of purified CM, we have generated a transgenic murine iPS cell line, which expresses puromycin resistance protein N-acetyltransferase and EGFP under the control of the cardiomyocyte-specific α-myosin heavy chain promoter (alphaMHC-Puro-IRES-GFP, aPiG). We demonstrate that murine aPIG-iPS and aPIG-ES cells differentiate into spontaneously beating CM at comparable efficiencies. When selected with puromycin both cell types yielded more than 97% pure population of CMs. Both aPIG-iPS and aPIG-ES cell-derived CM express typical cardiac transcripts and structural proteins and possess similar sarcomeric organization. Action potential recordings revealed that iPS- and ES cell-derived CM respond to beta-adrenergic and muscarinic receptor modulation, express functional voltage-gated sodium, calcium and potassium channels and possess comparable current densities. Comparison of global gene expression profiles of CM generated from iPS and ES cells revealed that both cell types cluster close to each other but are highly distant to undifferentiated ES or iPS cells as well as unpurified iPS and ES cell-derived embryoid bodies (EB). Both iPS and ES cell-derived CMs express genes and functional categories typical for CM. They are enriched in genes involved in transcription and genes coding for structural proteins involved in cardiac muscle contraction and relaxation. They also express genes involved in heart and muscle developmental processes, ion export and ion binding processes and various metabolic processes for ATP synthesis. These CMs downregulate genes involved in immune response, cell cycle and cell division, thus demonstrating the CMs population is mitotically inactive. Most surface signaling pathways are also downregulated. Thus, a transgenic aPiG-iPS cell line can provide a robust supply of highly purified and functional CMs for future in vitro and in vivo studies. Seven different experimental groups were included into analysis: undifferentiated murine ES cells (1) and undifferentiated murine iPS cells (2), murine ES cell-derived embyroid bodies (3) and murine iPS cell-derived embryoid bodies at day 16 of differentiation (4), murine ES cell-derived cardiomyocytes (5) and murine iPS cell-derived cardiomyocytes (6) at day 16 of differentiation (they were generated by puromycin selection for 7 days prior to RNA isolation). Adult mouse tail tip fibroblasts (7) were used as a control for iPS cells. Total RNA samples were prepared from three independent biological replicates in groups 1-6. In group 7, single RNA probes were analyzed as three technical replicates.

Project description:Recent establishment of induced pluripotent stem (iPS) cells opened new avenues for generating human patient-specific stem cell derivatives that can be used for in vitro modeling of human disease, drug development and cell replacement therapy. In this study we analyzed the molecular and functional properties of cardiomyocytes (CM) differentiated from human iPS cells. Clusters of synchronously beating cells were first observed at day 11 of iPS cell differentiation. Beating clusters that were microdissected at day 18 of differentiation expressed high levels of cardiospecific transcripts NKx2.5, alpha-MHC, MLC2v, alpha-actinin and troponin T. Immunocytochemical stainings for alpha-actinin and troponin T revealed cross-striations typical of CM. Functional assessment of iPS cell-derived CM showed that these cells possess intact calcium transients and respond to beta-adrenergic and muscarinic stimulation. Molecular, structural and electrophysiological properties of iPS cell-derived CMs were highly comparable to their human ES cell-derived counterparts at the same differentiation stage. Comparison of global gene expression profiles of human ES and iPS cells and the corresponding microdissected beating areas further confirmed their similarity. We conclude that human iPS cells can differentiate into functional CM, which are indistinguishable from human ES cell-derived CMs and may fulfill the basic requirement for their use in disease modeling, drug screening and future therapeutic applications. Six different experimental groups were included into analysis: undifferentiated human ES cells (1) and undifferentiated human iPS cells (2), human ES cell-derived cardiomyocytes (3) and human iPS cell-derived cardiomyocytes (4) enriched by microdissection of spontaneously contracting embryoid body outgrowths, and human fetal (5) and adult (6) heart tissue. Total RNA samples were prepared from three independent biological replicates in groups 1-4. In groups 5 and 6, single RNA probes were analyzed as three technical replicates.

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