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.
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:Direct cardiac reprogramming of fibroblasts to cardiomyocytes presents an attractive therapeutic strategy to restore cardiac function following injury. Cardiac reprogramming was initially achieved through the overexpression of the transcription factors Gata4, Mef2c, and Tbx5 (GMT), and later, Hand2 (GHMT) and Akt1 (AGHMT) were found to further enhance this process. Yet, staunch epigenetic barriers severely limit the ability of these cocktails to reprogram adult fibroblasts. We undertook a screen of mammalian gene regulatory factors to discover novel regulators of cardiac reprogramming in adult fibroblasts and identified the histone reader PHF7 as the most potent activating factor. Mechanistically, PHF7 localizes to cardiac super-enhancers in fibroblasts, and through cooperation with the SWI/SNF complex, increases chromatin accessibility and transcription factor binding at these sites. Importantly, PHF7 is the first epigenetic factor found to achieve efficient reprogramming in the absence of Gata4. Here, we highlight the underexplored necessity of cardiac epigenetic modifiers, such as PHF7, in harnessing chromatin remodeling complexes to overcome critical barriers to direct cardiac reprogramming.
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.