Project description:Recent studies have been successful at utilizing ectopic expression of transcription factors to generate induced cardiomyocytes (iCMs) from fibroblasts, albeit at a low frequency in vitro. This work investigates the influence of small molecules that have been previously reported to improve differentiation to cardiomyocytes as well as reprogramming to iPSCs in conjunction with ectopic expression of the transcription factors Hand2, Nkx2.5, Gata4, Mef2C, and Tbx5 on the conversion to functional iCMs. We utilized a reporter system in which the calcium indicator GCaMP is driven by the cardiac Troponin T promoter to quantify iCM yield. The TGFβ inhibitor, SB431542 (SB), was identified as a small molecule capable of increasing the conversion of both mouse embryonic fibroblasts and adult cardiac fibroblasts to iCMs up to ~5 fold. Further characterization revealed that inhibition of TGFβ by SB early in the reprogramming process led to the greatest increase in conversion of fibroblasts to iCMs in a dose-responsive manner. Global transcriptional analysis at Day 3 post-induction of the transcription factors revealed an increased expression of genes associated with the development of cardiac muscle in the presence of SB compared to the vehicle control. Incorporation of SB in the reprogramming process increases the efficiency of iCM generation, one of the major goals necessary to enable the use of iCMs for discovery-based applications and for the clinic. Mouse embryonic fibroblasts (MEFs) and adult mouse cardiac fibroblasts (CFs) were transfected with an empty vector (0F) or the combination of Hand2, Nkx2.5, Gata4, Mef2C, and Tbx5 (5F). Samples were exposed to the vehicle control (D, DMSO), SB431542 (SB, 0.5 uM MEF, 5 uM CF), or TGFb1 (T, 2 ng/mL) during culture. Transcription factor expression was induced at Day 0 and samples were isolated at Day 3 post-induction.
Project description:Direct conversion of fibroblasts to induced cardiomyocytes (iCMs) has great potential for regenerative medicine. Recent publications have reported significant progress, but the evaluation of reprogramming has relied upon non-functional measures such as flow cytometry for cardiomyocyte markers or GFP expression driven by a cardiomyocyte-specific promoter. The issue is one of practicality: the most stringent measures - electrophysiology to detect cell excitation and the presence of spontaneously contracting myocytes - are not readily quantifiable in the large numbers of cells screened in reprogramming experiments. However, excitation and contraction are linked by a third functional characteristic of cardiomyocytes: the rhythmic oscillation of intracellular calcium levels. We set out to optimize direct conversion of fibroblasts to iCMs with a quantifiable calcium reporter to rapidly assess functional transdifferentiation. We constructed a reporter system in which the calcium indicator GCaMP is driven by the cardiomyocyte-specific Troponin T promoter. Using calcium activity as our primary outcome measure, we compared several published combinations of transcription factors along with novel combinations in mouse embryonic fibroblasts. The most effective combination consisted of Hand2, Nkx2.5, Gata4, Mef2c, and Tbx5 (HNGMT). This combination is >50-fold more efficient than GMT alone and produces iCMs with cardiomyocyte marker expression, robust calcium oscillation, and spontaneous beating that persists for weeks following inactivation of reprogramming factors. HNGMT is also significantly more effective than previously published factor combinations for the transdifferentiation of adult mouse cardiac fibroblasts to iCMs. Quantification of calcium function is a convenient and effective means for the identification and evaluation of cardiomyocytes generated by direct reprogramming. Using this stringent outcome measure, we conclude that HNGMT produces iCMs more efficiently than previously published methods. Mouse embryonic fibroblasts were treated with different combinations of transcription factors to drive transdifferentiation to induced cardiomyocytes (iCMs). Putative iCMs were enriched by zeocin selection. Zeocin resistance was conferred to iCMs via the TroponinT-GCaMP5-Zeo lentiviral reporter.
Project description:Global gene expression patterns of the iCMs shift from a MEF state toward a cardiac-like phenotype by Gata4/Mef2c/Tbx5 (GMT) or GMT/miR-133 transduction at 3, 7 and 18 days after transduction (D3, D7 and D18) MiR-133 silenced fibroblast signatures in parallel with cardiac gene activation, and Snai1 overexpression inhibited the effects of miR-133-mediated cardiac reprogramming. MEFs were used for negative control, mouse heart tissue for positive control. Gene expression profiles were compared among MEFs, iCMs and heart. 23474 probes were analyzed in each experiment.
Project description:Cardiomyocytes derived from induced pluripotent stem cells (iPSC-CMs) or directly reprogrammed from non-myocytes (induced cardiomyocytes, iCMs) are promising sources for heart regeneration or disease modeling. However, the similarities and differences between iPSC-CM and iCM are still unknown. Here we performed transcriptome analyses of beating iPSC-CMs and iCMs generated from cardiac fibroblasts (CFs) of the same origin. Although both iPSC-CMs and iCMs establish CM-like molecular features globally, iPSC-CMs exhibit a relatively hyperdynamic epigenetic status while iCMs exhibit maturation status that more resemble adult CMs. Based on gene expression of metabolic enzymes, iPSC-CMs primarily employ glycolysis while iCMs utilize fatty acid oxidation as the main pathway. Importantly, iPSC-CMs and iCMs exhibit different cell cycle status, alteration of which influenced their maturation. Therefore, our study provides a foundation for understanding the pros and cons of different reprogramming approaches.
2017-09-26 | GSE99814 | GEO
Project description:Gene expression profiles of induced cardiomyocytes(iCMs)
Project description:The direct conversion, or trans-differentiation, of non-cardiac cells into cardiomyocytes by forced expression of transcription factors and microRNAs provide promising ways of cardiac regeneration. However, genetic manipulations are still not desirable in real clinical applications. we report the generation of automatically beating cardiomyocyte-like cells from mouse fibroblasts with only chemical cocktails. These chemical-induced cardiomyocyte-like cells (CiCMs) express cardiomyocyte-specific markers, exhibit sarcomeric organization, and possess typical cardiac calcium flux and electrophysiological features. Microarray-bassed gene expression patterns of Mouse embryonic fibroblasts (MEFs), CiCMs, and cardiomyocytes(CMs) indicated a clear transition from dividing MEFs to differentiated cardiomyocyte-like state in CiCM samples. Mouse embryonic fibroblasts were treated with a small-molecule combination CRFVPT (10 μM CHIR99021 (C); 10 μM RepSox (R); 50 μM Forskolin (F); 0.5 mM VPA (V); 5 μM Parnate, (P); 1 μM TTNPB (T)) to induce transdifferentiation to chemical-induced cardiomyocyte-like cells. CiCMs beating clusters were picked at day 24 for analysis. MEFs were isolated from mouse embryos, and CMs were isolated from mouse hearts. Total RNA of MEFs, CiCMs and CMs were extracted and hybridization on Affymetrix microarrays.
Project description:Recent studies have been successful at utilizing ectopic expression of transcription factors to generate induced cardiomyocytes (iCMs) from fibroblasts, albeit at a low frequency in vitro. This work investigates the influence of small molecules that have been previously reported to improve differentiation to cardiomyocytes as well as reprogramming to iPSCs in conjunction with ectopic expression of the transcription factors Hand2, Nkx2.5, Gata4, Mef2C, and Tbx5 on the conversion to functional iCMs. We utilized a reporter system in which the calcium indicator GCaMP is driven by the cardiac Troponin T promoter to quantify iCM yield. The TGFβ inhibitor, SB431542 (SB), was identified as a small molecule capable of increasing the conversion of both mouse embryonic fibroblasts and adult cardiac fibroblasts to iCMs up to ~5 fold. Further characterization revealed that inhibition of TGFβ by SB early in the reprogramming process led to the greatest increase in conversion of fibroblasts to iCMs in a dose-responsive manner. Global transcriptional analysis at Day 3 post-induction of the transcription factors revealed an increased expression of genes associated with the development of cardiac muscle in the presence of SB compared to the vehicle control. Incorporation of SB in the reprogramming process increases the efficiency of iCM generation, one of the major goals necessary to enable the use of iCMs for discovery-based applications and for the clinic.