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: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.

Project description:Background: Pathological cardiac overload triggers maladaptive myocardial remodeling that predisposes to the development of heart failure. The contribution of long non-coding RNAs (lncRNAs) to intercellular signaling during cardiac remodeling is largely unknown. Methods: We analyzed the expression of Gadlor 1 and Gadlor2 lncRNAs in mouse hearts, mouse cardiac cells, extracellular vesicles (EVs), human failing hearts as well as patient serum. Gadlor knock-out (KO) mice were generated and analyzed. The effect of Gadlor knock-out and Gadlor overexpression during cardiac pressure overload induced by transverse aortic constriction (TAC) was analyzed by echocardiography, histological analyses and RNA sequencing in isolated cardiac cells. Gadlor1/2 interaction partners were identified by RNA antisense purification coupled with mass-spectrometry (RAP-MS). Results: In the heart, the related lncRNAs Gadlor1 and 2 are mainly expressed in endothelial cells and to a lesser extent in fibroblasts. Gadlor1/2 are upregulated in failing mouse hearts as well as in the myocardium and in serum of heart failure patients. Interestingly, Gadlor1 and 2 are secreted from endothelial cells within EVs, which are taken up by cardiomyocytes. Gadlor-KO mice exerted reduced cardiomyocyte hypertrophy, diminished myocardial fibrosis and improved cardiac function, but paradoxically suffered from sudden death during prolonged overload. Gadlor overexpression, in turn, triggered hypertrophy, fibrosis and cardiac dysfunction. Mechanistically, Gadlor1 and Gadlor2 inhibit angiogenic gene expression in endothelial cells, while promoting the expression of pro-fibrotic genes in cardiac fibroblasts. In cardiomyocytes, Gadlor1/2 upregulate mitochondrial genes, but downregulate angiogenesis genes, while interacting with the transcriptional regulator Glyr1 and the calcium/calmodulin-dependent protein kinase type II (CaMKII), entailing cardiomyocyte hypertrophy and perturbed cardiomyocyte calcium dynamics. Conclusions: We describe that Gadlor1 and 2, two related, novel lncRNAs, are upregulated in cardiac pathological overload and are secreted from endothelial cells within EVs. Gadlor1/2 induce cardiac dysfunction, cardiomyocyte hypertrophy and myocardial fibrosis by exerting heterocellular effects on cardiac cellular gene-expression and by affecting calcium dynamics in cardiomyocytes, which take up the Gadlor1/2 by EV mediated transfer from endothelial cells. Targeted inhibition of Gadlor lncRNAs in endothelial cells or fibroblasts might serve as therapeutic strategy in the future.

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Transdifferentiation Of Human Dermal Fibroblasts Towards The Cardiac Cell Lineage

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