Identifying the Transcriptome Signature of Calcium Channel Blocker in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes
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ABSTRACT: This study aimed to simulate chronic CCB treatment and to examine both the functional and transcriptomic changes in human cardiomyocytes. We differentiated cardiomyocytes from three human induced pluripotent stem cell (iPSC) lines and exposed them to four different CCBs—nifedipine, amlodipine, diltiazem, and verapamil—at their physiological serum concentrations for two weeks. Without inducing cell death and damage to myofilament structure, CCBs elicited line specific inhibition on calcium kinetics and contractility. While all four CCBs exerted similar inhibition on calcium kinetics, verapamil applied the strongest inhibition on cardiomyocyte contractile function. By profiling cardiomyocyte transcriptome after CCB treatment, we identified little overlap in their transcriptome signatures. Verapamil is the only inhibitor that reduced the expression of contraction related genes, such as myosin heavy chain and troponin I, consistent with its depressive effects on contractile function. This is the first study to identify the transcriptome signatures of different CCBs in human cardiomyocytes. The distinct gene expression patterns suggest that although the four inhibitors act on the same target, they may have distinct effects on normal cardiac cell physiology.
Project description:Objective: L-type calcium channels (LTCC) homeostatically regulate calcium on a beat by beat basis, but also provide Ca that over long time scales may contribute to transcriptional regulation. We previously showed that sustained LTCC blockade (CCB) elicits LTCC remodeling in ventricular cardiac myocytes (CM). Here we hypothesize that sustained CCB has broad effects on the expression of genes involved in calcium handling. Methods and Results: Therefore, we subjected adult mice to sustained CCB for 24 hours and performed gene expression profiling. In comparison to vehicle-only control animals, 231 genes were up-regulated, and 111 genes were down-regulated by sustained LTCC blockade (p <0.01). Gene ontology analysis suggested that the CaMKIIdelta signaling pathway was up-regulated in these cells. Unexpectedly, phosphorylation of phospholamban (PLN) at threonine17 (Thr17), an index of CaMKIIdelta activity, was not changed by sustained CCB; however, the degree of phosphorylation of the neighboring PLN-Ser16 substrate site for PKA was significantly reduced by sustained CCB compared to control. Gene expression profiling suggested no change in PKA, but it showed that protein phosphatase 2A (PP2A) mRNA increased, and immunoblots demonstrated that PP2Ac-alpha protein was significantly increased by sustained CCB. Consistent with elevated PP2Ac-alpha protein expression LTCC exhibited decreased phosphorylation of the C-terminal Ser1928 PKA substrate site. Conclusions: We conclude that sustained CCB elicits a spectrum of transcriptional events, including compensatory up-regulation of LTCC and PP2Ac-alpha. Although this study is restricted to mouse, these results suggest the new hypothesis that clinically-relevant sustained LTCC blockade in humans results in changes in gene regulation in the heart. Keywords: L-type calcium channel, calcium channel blockade, verapamil Female and male ICR mice (12-14 weeks age) weighing between 25 and 30 grams were anesthetized with a ketamine/xylazine mixture ( i.p.) allowing the subcutaneous implantation of miniosmotic pumps (Alzet, model 2001). The pumps were filled with either verapamil or vehicle (0.02% ascorbic acid). Control animals carried mini-pumps with vehicle and control animals were investigated in parallel with each set of experimental animals. Mini pumps delivered verapamil at 3.6 mg/kg/day for 24 (RNA)-48 (protein) hours. After treatment animals were anesthetized and weighed. Hearts were excised, rinsed, blotted dry, weighed, and then frozen on dry ice and the stored at -80oC until studied. Animals were anesthetized and euthanized according to animal protocols approved by the University of Kentucky Institutional Animal Care and Use Committee. This investigation conforms with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication NO. 85-23, revised 1996). Left ventricular free wall from female mice was rapidly excised and either snap frozen at -80oC or used immediately for RNA isolation. Three VER treated mice and 3 vehicle treated mice were used to generate RNA for microarray. Total RNA was isolated using the RNAqueous -4PCR kit (Ambion) and quantitated spectrophotometrically at 260nm. Contaminating genomic DNA was eliminated by DNase treatment (Ambion). RNA quality was assessed using the Agilent 2100 Bioanalyzer. Microarray data was obtained using the Affymetrix 430 V2 GeneChip (representing 45,101 probe sets), in accordance with the manufacturer’s specifications.
Project description:Objective: L-type calcium channels (LTCC) homeostatically regulate calcium on a beat by beat basis, but also provide Ca that over long time scales may contribute to transcriptional regulation. We previously showed that sustained LTCC blockade (CCB) elicits LTCC remodeling in ventricular cardiac myocytes (CM). Here we hypothesize that sustained CCB has broad effects on the expression of genes involved in calcium handling. Methods and Results: Therefore, we subjected adult mice to sustained CCB for 24 hours and performed gene expression profiling. In comparison to vehicle-only control animals, 231 genes were up-regulated, and 111 genes were down-regulated by sustained LTCC blockade (p <0.01). Gene ontology analysis suggested that the CaMKIIdelta signaling pathway was up-regulated in these cells. Unexpectedly, phosphorylation of phospholamban (PLN) at threonine17 (Thr17), an index of CaMKIIdelta activity, was not changed by sustained CCB; however, the degree of phosphorylation of the neighboring PLN-Ser16 substrate site for PKA was significantly reduced by sustained CCB compared to control. Gene expression profiling suggested no change in PKA, but it showed that protein phosphatase 2A (PP2A) mRNA increased, and immunoblots demonstrated that PP2Ac-alpha protein was significantly increased by sustained CCB. Consistent with elevated PP2Ac-alpha protein expression LTCC exhibited decreased phosphorylation of the C-terminal Ser1928 PKA substrate site. Conclusions: We conclude that sustained CCB elicits a spectrum of transcriptional events, including compensatory up-regulation of LTCC and PP2Ac-alpha. Although this study is restricted to mouse, these results suggest the new hypothesis that clinically-relevant sustained LTCC blockade in humans results in changes in gene regulation in the heart. Keywords: L-type calcium channel, calcium channel blockade, verapamil
Project description:Cardiomyocytes (CMs) lost during ischemic cardiac injury cannot be replaced due to their limited proliferative capacity. Ca2+ is an important signal transducer that regulates key cellular processes, but its role in regulating CM proliferation is incompletely understood. A drug screen targeting proteins involved in CM Ca2+ cycling in human embryonic stem cell-derived cardiac organoids (hCOs) revealed that only the inhibition of L-Type Calcium Channel (LTCC) using nifedipine induced the CM cell cycle. Overexpression of Ras-related associated with Diabetes (RRAD), an endogenous inhibitor of LTCC, induced CM cell cycle activity in vitro, in human cardiac slices, and in vivo. Mechanistically, LTCC inhibition by RRAD or nifedipine induced CM cell cycle by modulating calcineurin activity and Hoxb13 nuclear translocation. Moreover, ectopic expression of RRAD/CDK4/CCND in combination induced CM proliferation in vitro and in vivo, improved cardiac function and reduced scar size post-myocardial infarction. Together, these findings represent a robust pathway for new Ca2+ signaling-based cardiac regenerative strategies.
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:Although human pluripotent stem cells-derived cardiomyocytes (hPSC-CMs) have emerged as a novel platform for heart regeneration, disease modeling, and drug screening, their immaturity significantly hinders their application. A hallmark of postnatal cardiomyocyte maturation is the metabolic substrate switch from glucose to fatty acids. We hypothesized that fatty acid supplementation would enhance hPSC-CM maturation. Fatty acid treatment induces cardiomyocyte hypertrophy and significantly increases cardiomyocyte force production. The improvement in force generation is accompanied by enhanced calcium transient peak height and kinetics, and by increased action potential upstroke velocity. Fatty acids enhance mitochondrial respiratory reserve capacity. RNA sequencing showed fatty acid treatment upregulates genes involved in fatty acid β-oxidation and downregulates genes in lipid synthesis. Signal pathway analyses reveal that fatty acid treatment results in phosphorylation of multiple intracellular kinases. Thus, fatty acids increase human cardiomyocyte hypertrophy, force generation, calcium dynamics, action potential upstroke velocity, and oxidative capacity. This enhanced maturation should facilitate hPSC-CMs usage for cell therapy, disease modeling, and drug/toxicity screens.
Project description:Calcium signaling is a central regulator of cardiomyocyte growth and function. Calmodulin is a critical mediator of calcium signals. Because the amount of calmodulin within cardiomyocytes is limiting, precise regulation of calmodulin expression may be an important for regulation of calcium signaling. In this study, we show for the first time that calmodulin levels are regulated post-transcriptionally in heart failure. The cardiomyocyte-restricted microRNA miR-1 inhibited translation of calmodulin-encoding mRNAs via highly conserved target sites within their 3â-untranslated regions. In keeping with its effect on calmodulin expression, miR-1 downregulated calcium-calmodulin signaling through the calcineurin to NFAT. miR-1 also negatively regulated expression of Mef2a and Gata4, key transcription factors that mediate calcium-dependent changes in gene expression. Consistent with downregulation of these hypertrophy-associated genes, miR-1 attenuated cardiomyocyte hypertrophy in cultured neonatal rat cardiomyocytes and in the intact adult heart. Our data indicate that miR-1 regulates cardiomyocyte growth responses by negatively regulating the calcium-signaling components calmodulin, Mef2a, and Gata4. We show that miR-1 is downregulated in a murine heart failure model. miRNAs expression changes were measured in calcineurin transgenic model of heart failure and control mice using a Luminex platform. Reduced miR-1 expression was associated with broad alteration in expression of predicted target genes. To test this, we measured miRs including miR-1 and genome wide transcriptome changes in vivo and in vitro system. Calcineurin transgenic heart was compared to nontransgenic heart (NTg vs. CNTg). We also investigated the gene expression changes during the course of cardiomyocytes differentiation using DMSO treated P19CL6 cell lines. Two time points (day 6 and day 10) were compared to identified the gene expression changes of predicted miR-1 targets (Day 6 vs. Day 10).
Project description:Calcium signaling is a central regulator of cardiomyocyte growth and function. Calmodulin is a critical mediator of calcium signals. Because the amount of calmodulin within cardiomyocytes is limiting, precise regulation of calmodulin expression may be an important for regulation of calcium signaling. In this study, we show for the first time that calmodulin levels are regulated post-transcriptionally in heart failure. The cardiomyocyte-restricted microRNA miR-1 inhibited translation of calmodulin-encoding mRNAs via highly conserved target sites within their 3’-untranslated regions. In keeping with its effect on calmodulin expression, miR-1 downregulated calcium-calmodulin signaling through the calcineurin to NFAT. miR-1 also negatively regulated expression of Mef2a and Gata4, key transcription factors that mediate calcium-dependent changes in gene expression. Consistent with downregulation of these hypertrophy-associated genes, miR-1 attenuated cardiomyocyte hypertrophy in cultured neonatal rat cardiomyocytes and in the intact adult heart. Our data indicate that miR-1 regulates cardiomyocyte growth responses by negatively regulating the calcium-signaling components calmodulin, Mef2a, and Gata4.
Project description:Fight-or-flight responses involve β-adrenergic-induced increases in heart rate and contractile force. Despite decades of investigations, predominantly focusing on ryanodine receptor and phospholamban phosphorylation, the molecular mechanisms underlying the sympathetic nervous system control of cardiac contractility remain controversial and incompletely elucidated. Here, we identify the calcium-channel inhibitor Rad as a critical component. In cardiomyocytes isolated from knock-in mice expressing Rad with alanine-substitutions of the four PKA-phosphorylated serine residues (4SA-Rad), calcium currents cannot be increased by adrenergic agonists or phosphatase inhibitor. In these mice, basal cardiac contractility, exercise capacity and heart rate are reduced, and the augmentation of contractile force by adrenergic agonists is severely blunted. Expression of mutant calcium-channel β-subunits that cannot bind Rad is sufficient to restore calcium influx and cardiac contractility in 4SA-Rad mice to levels induced by adrenergic agonists in wild-type mice, revealing a potential therapeutic approach to enhance cardiac contractility while bypassing stimulation of adrenergic receptors.
Project description:Heart muscle cells, cardiomyocytes, are highly differentiated cells that usually do not proliferate . During the non-proliferative state, extracellular signals control cardiomyocyte contractile function. However, during development and regeneration, cardiomyocytes enter the cell cycle and divide. It is unknown how cardiomyocytes modify their intracellular signaling to direct the cell cycle program. Here, we show that the nuclear lamina protein Lamin B2 (Lmnb2) regulates cardiomyocyte cell cycle activity using a gatekeeper mechanism. We identified Lmnb2 as a candidate for regulating intracellular signaling with deep transcriptional profiling of single cardiomyocytes. Lmnb2 was sufficient and necessary for cardiomyocyte cycling in the presence of serum. Lmnb2 increased the nucleoporin NUP98 and permeability of the nuclear membrane for phosphorylated ERK1/2. In vivo, the Lmnb2 gene was required for cardiomyocyte cell cycle activity during development. Increasing the expression of Lmnb2 in neonatal mice promoted cardiomyocyte M-phase and cytokinesis. LmnB2 gene transfer in neonatal mice that received a myocardial injury increased cardiomyocyte division and myocardial function in the injury border zone, indicating that the regenerated cardiomyocytes were functionally integrated. We propose a gatekeeper function of Lmnb2 that can be targeted to increase cardiomyocyte regeneration without the administration of exogenous growth factors.
Project description:We performed RNA-Seq analysis of neoatal rat ventricular cardiomyocytes (NRVCs) and human pluripotent stem cells derived cardiomyocytes (hPSC-CMs) which were treated with Nimodipine (NM) to investigate the moleclular mechanism of inhibiting L-type calcium channel (LTCC) to promote cardiomyocyte proliferation.