COX6A2 deficiency leads to cardiac remodeling in human pluripotent stem cell-derived cardiomyocytes.

BACKGROUND: Cardiac remodeling is the initiating factor for the development of heart failure, which can result from various cardiomyopathies. Cytochrome c oxidase subunit 6A2 (COX6A2) is one of the components of cytochrome c oxidase that drives oxidative phosphorylation. The pathogenesis of myocardial remodeling caused by COX6A2 deficiency in humans remains unclear because there are no suitable research models. In this study, we established a COX6A2-deficient human cardiac myocyte (CM) model that mimics the human COX6A2 homozygous mutation and determined the effects of COX6A2 dysfunction and its underlying mechanism. METHODS: A human COX6A2 homozygous knockout cardiomyocyte model was established by combining CRISPR/Cas9 gene editing technology and hiPSC-directed differentiation technology. Cell model phenotypic assays were done to characterize the pathological features of the resulting COX6A2-deficient cardiomyocytes. RESULTS: COX6A2 gene knockout did not affect the pluripotency and differentiation efficiency of hiPSCs. Myocardial cells with a COX6A2 gene knockout showed abnormal energy metabolism, increased oxidative stress levels, abnormal calcium transport activity, and decreased contractility. In addition, L-carnitine and trimetazidine significantly improved energy metabolism in the COX6A2-deficient human myocardial model. CONCLUSIONS: We have established a COX6A2-deficient human cardiomyocyte model that exhibits abnormal energy metabolism, elevated oxidative stress levels, abnormal calcium transport, and reduced contractility. This model represents an important tool to gain insight into the mechanism of action of energy metabolism disorders resulting in myocardial remodeling, elucidate the gene-phenotype relationship of COX6A2 deficiency, and facilitate drug screening.

The pseudoenzyme ADPRHL1 affects cardiac function by regulating the ROCK pathway.

BACKGROUND: Pseudoenzymes, catalytically deficient variants of active enzymes, have a wide range of regulatory functions. ADP-ribosylhydrolase-like 1 (ADPRHL1), a pseudoenzyme belonging to a small group of ADP-ribosylhydrolase enzymes that lacks the amino acid residues necessary for catalytic activity, may have a significant role in heart development based on accumulating evidence. However, the specific function of ADPRHL1 in this process has not been elucidated. To investigate the role of ADPRHL1 in the heart, we generated the first in vitro human embryonic stem cell model with an ADPRHL1 knockout. METHOD: Using the CRISPR/Cas9 system, we generated ADPRHL1 knockout in the human embryonic stem cell (hESC) H9 line. The cells were differentiated into cardiomyocytes using a chemically defined and xeno-free method. We employed confocal laser microscopy to detect calcium transients and microelectrode array (MEA) to assess the electrophysiological activity of ADPRHL1 deficiency cardiomyocytes. Additionally, we investigated the cellular mechanism of ADPRHL1 by Bulk RNA sequencing and western blot. RESULTS: The results indicate that the absence of ADPRHL1 in cardiomyocytes led to adhered abnormally, as well as perturbations in calcium transients and electrophysiological activity. We also revealed that disruption of focal adhesion formation in these cardiomyocytes was due to an excessive upregulation of the ROCK-myosin II pathway. Notably, inhibition of ROCK and myosin II effectively restores focal adhesions in ADPRHL1-deficient cardiomyocytes and improved electrical conduction and calcium activity. CONCLUSIONS: Our findings demonstrate that ADPRHL1 plays a critical role in maintaining the proper function of cardiomyocytes by regulating the ROCK-myosin II pathway, suggesting that it may serve as a potential drug target for the treatment of ADPRHL1-related diseases.

KCNQ1-deficient and KCNQ1-mutant human embryonic stem cell-derived cardiomyocytes for modeling QT prolongation.

BACKGROUND: The slowly activated delayed rectifier potassium current (IKs) mediated by the KCNQ1 gene is one of the main currents involved in repolarization. KCNQ1 mutation can result in long-QT syndrome type 1 (LQT1). IKs does not participate in repolarization in mice; thus, no good model is currently available for research on the mechanism of and drug screening for LQT1. In this study, we established a KCNQ1-deficient human cardiomyocyte (CM) model and performed a series of microelectrode array (MEA) detection experiments on KCNQ1-mutant CMs constructed in other studies to explore the pathogenic mechanism of KCNQ1 deletion and mutation and perform drug screening. METHOD: KCNQ1 was knocked out in human embryonic stem cell (hESC) H9 line using the CRISPR/cas9 system. KCNQ1-deficient and KCNQ1-mutant hESCs were differentiated into CMs through a chemically defined differentiation protocol. Subsequently, high-throughput MEA analysis and drug intervention were performed to determine the electrophysiological characteristics of KCNQ1-deficient and KCNQ1-mutant CMs. RESULTS: During high-throughput MEA analysis, the electric field potential and action potential durations in KCNQ1-deficient CMs were significantly longer than those in wild-type CMs. KCNQ1-deficient CMs also showed an irregular rhythm. Furthermore, KCNQ1-deficient and KCNQ1-mutant CMs showed different responses to different drug treatments, which reflected the differences in their pathogenic mechanisms. CONCLUSION: We established a human CM model with KCNQ1 deficiency showing a prolonged QT interval and an irregular heart rhythm. Further, we used various drugs to treat KCNQ1-deficient and KCNQ1-mutant CMs, and the three models showed different responses to these drugs. These models can be used as important tools for studying the different pathogenic mechanisms of KCNQ1 mutation and the relationship between the genotype and phenotype of KCNQ1, thereby facilitating drug development.

Losartan protects human stem cell-derived cardiomyocytes from angiotensin II-induced alcoholic cardiotoxicity.

Alcoholic cardiomyopathy (ACM) is a myocardial injury caused by long-term heavy drinking. Existing evidence indicates that high levels of oxidative stress are the key to pathological cardiomyopathy caused by long-term exposure to high concentrations of alcohol, while angiotensin II (AngII) and its type 1 receptor (AT1R) play an important role in excessive drinking. Whether oxidative stress-induced damage in ACM is related to AngII and AT1R is unclear, and the effects of alcohol on the electrophysiology of myocardial cells have not been reported. Most existing studies have used animal models. This study established an in vitro model of ACM based on human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The transcriptional profiling of alcohol treatment was performed by RNA-seq analysis. The role of oxidative stress, the expression of nicotinamide adenine dinucleotide phosphate oxidase (NOX), and the role of AngII and AT1R in the overactivation of oxidative stress were studied using fluorescent labeling, Western blotting, and high-content quantitative analysis. Real-time cell analysis(RTCA) and microelectrode array (MEA) were used to continuously monitor myocardial beating, observe the effects of alcohol on myocardial electrophysiological activity, and clarify the protective effects of the AT1R blocker losartan on ACM. We found that AngII and AT1R contribute to the effects of alcohol on the myocardium through oxidative stress damage, the mechanism of which may be achieved by regulating NOX.

Ranolazine rescues the heart failure phenotype of PLN-deficient human pluripotent stem cell-derived cardiomyocytes.

Phospholamban (PLN) is a key regulator that controls the function of the sarcoplasmic reticulum (SR) and is required for the regulation of cardiac contractile function. Although PLN-deficient mice demonstrated improved cardiac function, PLN loss in humans can result in dilated cardiomyopathy (DCM) or heart failure (HF). The CRISPR-Cas9 technology was used to create a PLN knockout human induced pluripotent stem cell (hiPSC) line in this study. PLN deletion hiPSCs-CMs had enhanced contractility at day 30, but proceeded to a cardiac failure phenotype at day 60, with decreased contractility, mitochondrial damage, increased ROS production, cellular energy metabolism imbalance, and poor Ca2+ handling. Furthermore, adding ranolazine to PLN knockout hiPSCs-CMs at day 60 can partially restore Ca2+ handling disorders and cellular energy metabolism, alleviating the PLN knockout phenotype of HF, implying that the disorder of intracellular Ca2+ transport and the imbalance of cellular energy metabolism are the primary mechanisms for PLN deficiency pathogenesis.

Generation of a homozygous S100A1 knockout human embryonic stem cell line (WAe009-A-73) by the CRISPR/Cas9 editing system.

S100A1 is a calcium-binding protein involved in myocardial contractility,which possesses a high affinity for calcium.  Several studies have demonstrated that S100A1 is a protector against myocardial injury. In this study, we have generated a homozygous S100A1 knockout (S100A1-KO) human embryonic stem cell (hESC) line by the CRISPR/Cas9 editing system. This S100A1-KO hESC line maintained normal morphology, pluripotency and karyotype, which can differentiate into three germ layers in vivo.

The Role of METTL3-Mediated N6-Methyladenosine (m6A) of JPH2 mRNA in Cyclophosphamide-Induced Cardiotoxicity.

Cyclophosphamide (CYP)-induced cardiotoxicity is a common side effect of cancer treatment. Although it has received significant attention, the related mechanisms of CYP-induced cardiotoxicity remain largely unknown. In this study, we used cell and animal models to investigate the effect of CYP on cardiomyocytes. Our data demonstrated that CYP-induced a prolonged cardiac QT interval and electromechanical coupling time courses accompanied by JPH2 downregulation. Moreover, N6-methyladenosine (m6A) methylation sequencing and RNA sequencing suggested that CYP induced cardiotoxicity by dysregulating calcium signaling. Importantly, our results demonstrated that CYP induced an increase in the m6A level of JPH2 mRNA by upregulating methyltransferases METTL3, leading to the reduction of JPH2 expression levels, as well as increased field potential duration and action potential duration in cardiomyocytes. Our results revealed a novel mechanism for m6A methylation-dependent regulation of JPH2, which provides new strategies for the treatment and prevention of CYP-induced cardiotoxicity.

Generation of a homozygous MYH7 gene knockout human embryonic stem cell line (WAe009-A-69) using an episomal vector-based CRISPR/Cas9 system.

Myosin heavy chain 7 (MYH7) encodes the human heart myosin heavy chain subunit, which plays an important role in myocardial contraction. MYH7 is the main pathogenic gene that causes Hypertrophic cardiomyopathy (HCM) and Dilated cardiomyopathy (DCM). In this experiment, a MYH7 homozygous knockout human embryonic stem cell (hESC) line, WAe009-A-69, was generated using an episomal vector-based CRISPR/Cas9 system. It can be an ideal tool to further study the function of MYH7. The cell line was confirmed with pluripotency, normal karyotype and trilineage differentiation potential.

Novel roles of an intragenic G-quadruplex in controlling microRNA expression and cardiac function.

Simultaneous dysregulation of multiple microRNAs (miRs) affects various pathological pathways related to cardiac failure. In addition to being potential cardiac disease-specific markers, miR-23b/27b/24-1 were reported to be responsible for conferring cardiac pathophysiological processes. In this study, we identified a conserved guanine-rich RNA motif within the miR-23b/27b/24-1 cluster that can form an RNA G-quadruplex (rG4) in vitro and in cells. Disruption of this intragenic rG4 significantly increased the production of all three miRs. Conversely, a G4-binding ligand tetrandrine (TET) stabilized the rG4 and suppressed miRs production in human and rodent cardiomyocytes. Our further study showed that the rG4 prevented Drosha-DGCR8 binding and processing of the pri-miR, suppressing the biogenesis of all three miRs. Moreover, CRISPR/Cas9-mediated G4 deletion in the rat genome aberrantly elevated all three miRs in the heart in vivo, leading to cardiac contractile dysfunction. Importantly, loss of the G4 resulted in reduced targets for the aforementioned miRs critical for normal heart function and defects in the L-type Ca2+ channel-ryanodine receptor (LCC-RyR) coupling in cardiomyocytes. Our results reveal a novel mechanism for G4-dependent regulation of miR biogenesis, which is essential for maintaining normal heart function.

Knockout of MYOM1 in human cardiomyocytes leads to myocardial atrophy via impairing calcium homeostasis.

Myomesin-1 (encoded by MYOM1 gene) is expressed in almost all cross-striated muscles, whose family (together with myomesin-2 and myomesin-3) helps to cross-link adjacent myosin to form the M-line in myofibrils. However, little is known about its biological function, causal relationship and mechanisms underlying the MYOM1-related myopathies (especially in the heart). Regrettably, there is no MYMO1 knockout model for its study so far. A better and further understanding of MYOM1 biology is urgently needed. Here, we used CRISPR/Cas9 gene-editing technology to establish an MYOM1 knockout human embryonic stem cell line (MYOM1-/- hESC), which was then differentiated into myomesin-1 deficient cardiomyocytes (MYOM1-/- hESC-CMs) in vitro. We found that myomesin-1 plays an important role in sarcomere assembly, contractility regulation and cardiomyocytes development. Moreover, myomesin-1-deficient hESC-CMs can recapitulate myocardial atrophy phenotype in vitro. Based on this model, not only the biological function of MYOM1, but also the aetiology, pathogenesis, and potential treatments of myocardial atrophy caused by myomesin-1 deficiency can be studied.

Generation of a homozygous COX6A2 knockout human embryonic stem cell line (WAe009-A-47) via an epiCRISPR/Cas9 system.

COX6A2 protein is a structural subunit of Complex IV (CIV/Cytochrome c oxidase/COX) in the mitochondrial respiratory chain. It is mainly expressed in the heart and skeletal muscle, also in some interneurons, regulating the assembly and catalytic activity of CIV. Its mutations can lead to COX deficiency, causing human myopathies, and maybe a potential cause of neurological abnormalities. Here, we used the CRISPR/Cas9 editing system to establish a homozygous COX6A2 knockout (COX6A2-KO) human embryonic stem cell (hESC) line. This COX6A2-KO hESC has normal morphology, pluripotency, and karyotype, which can differentiate into three germ layers in vivo.