Project description:Reprogramming of mouse fibroblasts toward a myocardial cell fate by forced expression of cardiac transcription factors or microRNAs has recently been demonstrated. The potential clinical applicability of these findings is based on the minimal regenerative potential of the adult human heart and the limited availability of human heart tissue. An initial, but mandatory step toward clinical application of this approach is to establish conditions for conversion of adult human fibroblasts to a cardiac phenotype. Toward this goal, we sought to determine the optimal combination of factors necessary and sufficient for direct myocardial reprogramming of human fibroblasts. Here we show that four human cardiac transcription factors, including Gata4, Hand2, Tbx5, and myocardin, and two microRNAs, miR-1 and miR-133, activated cardiac marker expression in neonatal and adult human fibroblasts. After maintenance in culture for 4-11 weeks, human fibroblasts reprogrammed with these proteins and microRNAs displayed sarcomere-like structures and calcium transients, and a small subset of such cells exhibited spontaneous contractility. These phenotypic changes were accompanied by expression of a broad range of cardiac genes and suppression of non-myocyte genes. These findings indicate that human fibroblasts can be reprogrammed to cardiac-like myocytes by forced expression of cardiac transcription factors with muscle-specific microRNAs and represent a step toward possible therapeutic application of this reprogramming approach. Human foreskin fibroblasts were transduced with 5 transcription factors and total RNA was obtained 4 weeks later. total RNA was also obtained from human foreskin fibroblasts as a negative control and adult human heart tissue as a positive control. The expression level of genes in each sample was compared.
Project description:Reprogramming of mouse fibroblasts toward a myocardial cell fate by forced expression of cardiac transcription factors or microRNAs has recently been demonstrated. The potential clinical applicability of these findings is based on the minimal regenerative potential of the adult human heart and the limited availability of human heart tissue. An initial, but mandatory step toward clinical application of this approach is to establish conditions for conversion of adult human fibroblasts to a cardiac phenotype. Toward this goal, we sought to determine the optimal combination of factors necessary and sufficient for direct myocardial reprogramming of human fibroblasts. Here we show that four human cardiac transcription factors, including Gata4, Hand2, Tbx5, and myocardin, and two microRNAs, miR-1 and miR-133, activated cardiac marker expression in neonatal and adult human fibroblasts. After maintenance in culture for 4-11 weeks, human fibroblasts reprogrammed with these proteins and microRNAs displayed sarcomere-like structures and calcium transients, and a small subset of such cells exhibited spontaneous contractility. These phenotypic changes were accompanied by expression of a broad range of cardiac genes and suppression of non-myocyte genes. These findings indicate that human fibroblasts can be reprogrammed to cardiac-like myocytes by forced expression of cardiac transcription factors with muscle-specific microRNAs and represent a step toward possible therapeutic application of this reprogramming approach.
Project description:Four transcription factors, GATA4, Hand2, MEF2C, Tbx5 (GHMT) activated cardiac gene expression in cardiac fibroblasts, suggesting that these factors are able to reprogram fibroblasts toward a cardaic cell fate. Total RNA isolated from adult cardiac fibroblasts transduced with empty retroviral vector or GHMT-retroviruses for 2, and 4 weeks.
Project description:Direct lineage conversion among various somatic cell types revolutionized the field of stem cell and regenerative medicine. In addition, the platform of cellular reprogramming offered a powerful system to gain new knowledge about cell plasticity and cell fate determination and ultimately challenged previous notions of cell identity. Previously, we successfully utilized single cell transcriptomics to reconstruct the molecular routes of how a murine fibroblast adopts cardiomyocyte fate following a continuum of states. In this study, we employed a comparative single cell transcriptomics approach to study human cardiac reprogramming. In comparison with murine fibroblasts and other human cell types, we identified unexpected heterogeneity in human cardiac fibroblasts that was mainly due to variance in cell cycle status. Trajectories inferred by SLICER suggest molecular routes and pathways taken by human fibroblasts when transiting into CM fate. Importantly, by assigning a “cell fate index” to each single cell on the iCM trajectories resolved from both mouse and human fibroblasts, we discovered species differences in fibroblast plasticity and intermediate cell fate statuses when reprogrammed towards a CM fate. Collectively, our comparative single cell transcriptomics study of human cardiac reprogramming revealed previously unrecognized molecular features of human cardiac fibroblasts and regulatory mechanisms in human cardiomyocyte cell fate control.
Project description:Background: Direct cardiac reprogramming is currently being investigated for the generation of cells with a true cardiomyocyte (CM) phenotype. Based on the original approach of cardiac transcription factor-induced reprogramming of fibroblasts into CM-like cells, various modifications of that strategy have been developed. However, they uniformly suffer from poor reprogramming efficacy and a lack of translational tools for target cell expansion and purification. Therefore, our group has developed a unique approach to generate proliferative cells with a pre-CM phenotype that can be expanded in vitro to yield substantial cell doses. Methods: Cardiac fibroblasts were reprogrammed toward CM fate using lentiviral transduction of cardiac transcriptions factors (GATA4, MEF2C, TBX5, and MYOCD). The resulting cellular phenotype was analyzed by RNA sequencing and immunocytology. Live target cells were purified based on intracellular CM marker expression using molecular beacon technology and fluorescence-activated cell sorting. CM commitment was assessed using 5-azacytidine–based differentiation assays and the therapeutic effect was evaluated in a mouse model of acute myocardial infarction using echocardiography and histology. The cellular secretome was analyzed using mass spectrometry. Results: We found that proliferative CM precursor-like cells were part of the phenotype spectrum arising during direct reprogramming of fibroblasts toward CMs. These induced CM precursors (iCMPs) expressed CPC- and CM-specific proteins and were selectable via hairpin-shaped oligonucleotide hybridization probes targeting Myh6/7-mRNA–expressing cells. After purification, iCMPs were capable of extensive expansion, with preserved phenotype when under ascorbic acid supplementation, and gave rise to CM-like cells with organized sarcomeres in differentiation assays. When transplanted into infarcted mouse hearts, iCMPs prevented CM loss, attenuated fibrotic scarring, and preserved ventricular function, which can in part be attributed to their substantial secretion of factors with documented beneficial effect on cardiac repair. Conclusions: Fibroblast reprogramming combined with molecular beacon-based cell selection yields an iCMP-like cell population with cardioprotective potential. Further studies are needed to elucidate mechanism-of-action and translational potential.
Project description:Four transcription factors, GATA4, Hand2, MEF2C, Tbx5 (GHMT) activated cardiac gene expression in cardiac fibroblasts, suggesting that these factors are able to reprogram fibroblasts toward a cardaic cell fate.
Project description:Fibroblasts can be directly reprogrammed toward a cardiac fate by introducing cardiogenic transcription factors (TFs), although the underlying mechanisms of the cardiac reprogramming process remain unclear. Three cardiac TFs, GATA4, MEF2C, and Tbx5 (referred to as GMT) can activate cardiac genes in fibroblasts and their cardiogenic activity is enhanced by the Hand2 TF and the Akt1 kinase. To understand the mechanistic basis of cardiac reprogramming, we performed a genome-wide analysis of cardiogenic TF binding sites and active enhancers, which were annotated by H3K27ac histone modification, during the reprogramming process. We found that cardiogenic TFs rapidly co-occupy core regulatory elements of cardiac genes and activate myriad cardiac enhancers that are enriched predominantly in Mef2 binding sites. Addition of Hand2 and Akt1 to the GMT reprogramming cocktail expands the spectrum of co-occupied active cardiac enhancers. As reprogramming proceeds over time, reprogramming TFs continue to activate additional cardiac enhancers, which are also enriched for Mef2 motifs, while fibroblast enhancers are silenced. This transition of the enhancer landscape strongly correlated with changes in the fibroblast and cardiac transcriptome. To test the relevance of cardiac reprogramming enhancers to the regulation of cardiogenesis in vivo, we assayed a collection of reprogramming enhancers in transgenic mouse embryos and found that they directed highly specific expression patterns in the developing heart. Our findings demonstrate that Hand2 and Akt1 enhance reprogramming by facilitating cardiac enhancer occupancy and identify Mef2 as a central effector of cardiac reprogramming, which coordinates the actions of accessory factors across a broad landscape of cardiac enhancers.
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs.
Project description:Fibroblasts can be directly reprogrammed toward a cardiac fate by introducing cardiogenic transcription factors (TFs), although the underlying mechanisms of the cardiac reprogramming process remain unclear. Three cardiac TFs, GATA4, MEF2C, and Tbx5 (referred to as GMT) can activate cardiac genes in fibroblasts and their cardiogenic activity is enhanced by the Hand2 TF and the Akt1 kinase. To understand the mechanistic basis of cardiac reprogramming, we performed a genome-wide analysis of cardiogenic TF binding sites and active enhancers, which were annotated by H3K27ac histone modification, during the reprogramming process. We found that cardiogenic TFs rapidly co-occupy core regulatory elements of cardiac genes and activate myriad cardiac enhancers that are enriched predominantly in Mef2 binding sites. Addition of Hand2 and Akt1 to the GMT reprogramming cocktail expands the spectrum of co-occupied active cardiac enhancers. As reprogramming proceeds over time, reprogramming TFs continue to activate additional cardiac enhancers, which are also enriched for Mef2 motifs, while fibroblast enhancers are silenced. This transition of the enhancer landscape strongly correlated with changes in the fibroblast and cardiac transcriptome. To test the relevance of cardiac reprogramming enhancers to the regulation of cardiogenesis in vivo, we assayed a collection of reprogramming enhancers in transgenic mouse embryos and found that they directed highly specific expression patterns in the developing heart. Our findings demonstrate that Hand2 and Akt1 enhance reprogramming by facilitating cardiac enhancer occupancy and identify Mef2 as a central effector of cardiac reprogramming, which coordinates the actions of accessory factors across a broad landscape of cardiac enhancers.
Project description:Background: Direct cardiac reprogramming of fibroblasts into cardiomyocytes has emerged as one of the promising strategies to remuscularize the injured myocardium. Yet, it is still insufficient to generate functional induced cardiomyocytes (iCMs) from human fibroblasts using conventional reprogramming cocktails, such as our previously published combination consisting of MEF2C, GATA4, TBX5 and microRNA miR-133 (MGT133). Results: To discover potential missing factors for human direct reprogramming, we performed transcriptomic comparison between human iCMs and functional cardiomyocytes (CMs). We identified T-box transcription factor TBX20 as the top CM gene that is unable to be activated by MGT133. TBX20 is required for normal heart development and cardiac function in adult CMs but its role on cardiac reprogramming remains undefined. Here, we found that transduction of MGT133+TBX20 in human cardiac fibroblasts resulted in enhanced reprogramming featured with significantly activated contractility gene programs and signatures more similar to ventricular CMs. Human iCMs produced with MGT133+TBX20 more frequently demonstrated beating and calcium oscillation in co-culture with pluripotent stem cell derived CMs. More mitochondria and higher mitochondrial respiration were also detected in iCMs after TBX20 overexpression. Mechanistically, comprehensive transcriptomic, chromatin occupancy and epigenomic integration revealed that TBX20 localized to the cis-regulatory enhancers of under-expressed cardiac genes, such as MYBPC3, MYH7 and MYL4, to activate gene expression via strengthening the occupancy and co-occupancy of transcription factors. Furthermore, we identified TBX20-regulated enhancers and confirmed the synergistic effect of MGT and TBX20 on enhancer activation. Conclusions: TBX20 promotes cardiac cell fate conversion via direct activating cardiac enhancers. Human iCMs generated with TBX20 showed enhanced cardiac function in terms of contractility and mitochondrial respiration.