Cardiac disease accounts for the largest proportion of adult mortality and morbidity in the industrialized world. However, progress toward improved clinical treatments is hampered by an incomplete understanding of the genetic programs controlling early cardiogenesis. To better understand this process, we set out to identify genes whose expression is enriched within early cardiac fated populations, obtaining the transcriptional signatures of mouse embryonic stem cells (mESCs) differentiating along a cardiac path.
Efficient array-based identification of novel cardiac genes through differentiation of mouse ESCs.
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View SamplesMouse embryonic stem cells can differentiate in vitro into spontaneously contracting cardiomyocytes. The main objective of this study was to investigate cardiogenesis in cultures of differentiating embryonic stem cells (ESCs) and to determine how closely it mimics in vivo cardiac development. We identified and isolated a population of cardiac progenitor cells (CPCs) through the use of a reporter DNA construct that allowed the expression of a selectable marker under the control of the Nkx2.5 enhancer. We proceeded to characterize these CPCs by examining their capacity to differentiate into cardiomyocytes and to proliferate. We then performed a large-scale temporal microarray expression analysis in order to identify genes that are uniquely upregulated or downregulated in the CPC population. We determined that the transcriptional profile of the mESC derived CPCs was consistent with pathways known to be active during embryonic cardiac development. We conclude that in vitro differentiation of mESCs recapitulates the early steps of mouse cardiac development.
Mouse ES cell-derived cardiac precursor cells are multipotent and facilitate identification of novel cardiac genes.
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View SamplesTransdifferentiation has been recently described as a novel method for converting human fibroblasts into induced cardiomyocyte-like cells. Such an approach can produce differentiated cells to study physiology or pathophysiology, examine drug interactions or toxicities, and engineer tissues. Here we describe the transdifferentiation of human dermal fibroblasts towards the cardiac cell lineage via the induced expression of transcription factors (TFs) GATA4, TBX5, MEF2C, MYOCD, NKX2-5, and delivery of microRNAs miR-1 and miR-133a. Cells undergoing transdifferentiation expressed ACTN2 and TNNT2 and partially organized their cytoskeleton in a cross-striated manner. The conversion process was associated with significant upregulation of a cohort of cardiac-specific genes, activation of pathways associated with muscle contraction and physiology, and downregulation of fibroblastic markers. We used a genetically encoded calcium indicator and readily detected active calcium transients although no spontaneous contractions were observed in transdifferentiated cells. Finally, we determined that inhibition of Janus kinase 1, inhibition of glycogen synthase kinase 3, or addition of NRG1 significantly enhanced the efficiency of transdifferentiation. Overall, we describe a method for achieving transdifferentiation of human dermal fibroblasts into induced cardiomyocyte-like cells via transcription factor overexpression, microRNA delivery, and molecular pathway manipulation.
Core Transcription Factors, MicroRNAs, and Small Molecules Drive Transdifferentiation of Human Fibroblasts Towards The Cardiac Cell Lineage.
Specimen part, Treatment, Time
View SamplesTransient over-expression of defined combinations of master regulator genes can effectively induce cellular reprogramming: the acquisition of an alternative predicted phenotype from a differentiated cell lineage. This can be of particular importance in cardiac regenerative medicine wherein the heart lacks the capacity to heal itself, but simultaneously contains a large pool of fibroblasts. In this study we determined the cardio-inducing capacity of ten transcription factors to actuate cellular reprogramming of mouse embryonic fibroblasts into cardiomyocyte-like cells. Over-expression of transcription factors MYOCD and SRF alone or in conjunction with Mesp1 and SMARCD3 significantly enhanced the basal but necessary cardio-inducing effect of the previously reported GATA4, TBX5, and MEF2C. In particular, combinations of five or seven transcription factors significantly enhanced the activation of cardiac reporter vectors, and induced an upregulation of cardiac-specific genes. Global gene expression analysis also demonstrated a significantly greater cardio-inducing effect when the transcription factors MYOCD and SRF were used. Detection of cross-striated cells was highly dependent on the cell culture conditions and was enhanced by the addition of valproic acid and JAK inhibitor. Although we detected Ca2+ transient oscillations in the reprogrammed cells, we did not detect significant changes in resting membrane potential or spontaneously contracting cells. This study further elucidates the cardio-inducing effect of the transcriptional networks involved in cardiac cellular reprogramming, contributing to the ongoing rational design of a robust protocol required for cardiac regenerative therapies.
Transcription factors MYOCD, SRF, Mesp1 and SMARCD3 enhance the cardio-inducing effect of GATA4, TBX5, and MEF2C during direct cellular reprogramming.
Specimen part
View SamplesDerivation of induced smooth muscle cells (iSMC) through direct transdifferentiation of a convenient and expandable primary cell source would open a wide range of prospects for their use in tissue engineering, drug testing, and disease modeling. Hypothesizing that MYOCD as a master regulator of smooth muscle gene expression would facilitate the generation of iSMC, we studied the conversion of human endothelial progenitor cells (EPC) into iSMC through the induced expression of by over-expression of MYOCD. A significant cytoskeletal rearrangement of the EPC resembling that of mesenchymal cells occurred within 3 days post initiation of MYOCD expression. This transition was associated with a downregulation of endothelial cell surface markers (CD31, CD105) as determined by flow cytometry. By day 7, iSMC derivation was evident with a significant upregulation of smooth muscle markers ACTA2, MYH11, TAGLN, and downregulation of CD31 and CDH5 as determined by gene expression analysis. Immunofluorescence revealed expression of MYH11 and ACTA2 and absence of endothelial markers VWF and CD31. By two weeks, microarray gene expression analysis demonstrated a significant similarity between iSMC and umbilical artery SMC (UASMC). The iSMC continued to develop toward the SMC lineage after four weeks of MYOCD induced expression. Microarray gene expression analysis showed an upregulation of molecular pathways associated with smooth muscle contraction and cytoskeletal reorganization in iSMC. Calcium transients were detected in iSMC when stimulated with phenylephrine but not in EPC. Contractility of iSMC was also higher than that of EPC as determined by traction force microscopy. Tissue-engineered blood vessels constructed using iSMC showed functionality with respect to flow- and drug- mediated vasodilation and vasoconstriction.
Transdifferentiation of human endothelial progenitors into smooth muscle cells.
Time
View SamplesDirect 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.
Optimization of direct fibroblast reprogramming to cardiomyocytes using calcium activity as a functional measure of success.
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View SamplesTo investigate the transcriptional remodelling during EMT, we treated normal murine mammary gland epithelial cells with TGFbeta for 0, 2h, 6h, 12h, 24h, 36h, 48h, 60h, 72h, 96h, 168h and 240h. Using WGCNA and pathway enrichment analysis we identified multiple gene expression modules that were enriched in general, signaling, metabolic or stuctural pathways highly relevant for EMT. Overall design: RNA sequencing of NMuMG/E9 cells induced to undergo EMT by treatment with TGFbeta from 0-10 days.
PyMT-1099, a versatile murine cell model for EMT in breast cancer.
Specimen part, Cell line, Subject
View SamplesWe have identified the transcription factor forkhead box protein F2 (Foxf2) to be upregulated in its expression during the EMT process and studied its functional contribution to EMT by siRNA-mediated knockdown in NMuMG cells treated for 4 days with TGFbeta followed by mRNA-sequencing. Our analysis revealed a dual role of Foxf2 during TGFbeta-induced EMT in promoting apoptosis while inducing cell junction breakdown and migration. Overall design: mRNA sequencing of NMuMG/E9 cells transfected with control siRNA or Foxf2 specific siRNA and treated with TGFbeta for 4 days
Foxf2 plays a dual role during transforming growth factor beta-induced epithelial to mesenchymal transition by promoting apoptosis yet enabling cell junction dissolution and migration.
Subject
View SamplesCase story. A patient with massive infiltration of the visceral adipose tissue depot by BAT in a patient with a catecholamine secreting paraganglioma. BAT tissue was identified by protein expression of UCP1 (western blotting and immunostaining)
Chronic adrenergic stimulation induces brown adipose tissue differentiation in visceral adipose tissue.
Specimen part
View SamplesThe endocytic receptor megalin constitutes the main pathway for clearance of plasma proteins from the glomerular filtrate in the proximal tubules. However, little is know about the mechanisms that control receptor activity. A widely discussed hypothesis states that the intracellular domain (ICD) of megalin, released upon ligand binding, acts as a transcription regulator to suppress receptor expression - a mechanism proposed to safeguard the proximal tubules from protein overload. Here, we have put this hypothesis to the test by generating a mouse model co-expressing the soluble ICD and the full-length receptor. Despite pronounced expression in the proximal tubules, the ICD failed to exert any effects on renal proximal tubular function such as megalin expression, protein retrieval, or renal gene transcription. Thus, our data argue that the ICD does not play a role in regulation of megalin activity in vivo in the proximal tubules.
The soluble intracellular domain of megalin does not affect renal proximal tubular function in vivo.
Sex, Age, Specimen part
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