hERG-deficient human embryonic stem cell-derived cardiomyocytes for modelling QT prolongation

Crispr-Based Editing of Human Pluripotent Stem Cells for Disease Modeling

The CRISPR system, as an effective genome editing technology, has been extensively utilized for the construction of disease models in human pluripotent stem cells. Establishment of a gene mutant or knockout stem cell line typically relies on Cas nuclease-generated double-stranded DNA breaks and exogenous templates, which can produce uncontrollable editing byproducts and toxicity. The recently developed adenine base editors (ABE) have greatly facilitated related research by introducing A/T > G/C mutations in the coding regions or splitting sites (AG-GT) of genes, enabling mutant gene knock-in or knock-out without introducing DNA breaks. In this study, we edit the AG bases in exons anterior to achieve gene knockout via the ABE8e-SpRY, which recognizes most expanded protospacer adjacent motif to target the genome. Except for gene-knockout, ABE8e-SpRY can also efficiently establish disease-related A/T-to-G/C variation cell lines by targeting coding sequences. The method we generated is simple and time-saving, and it only takes two weeks to obtain the desired cell line. This protocol provides operating instructions step-by-step for constructing knockout and point mutation cell lines.

Phosphoproteomics reveals a novel mechanism underlying the proarrhythmic effects of nilotinib, vandetanib, and mobocertinib

The use of tyrosine kinase inhibitors (TKIs) has resulted in significant occurrence of arrhythmias. However, the precise mechanism of the proarrhythmic effect is not fully understood. In this study, we found that nilotinib (NIL), vandetanib (VAN), and mobocertinib (MOB) induced the development of "cellrhythmia" (arrhythmia-like events) in a concentration-dependent manner in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Continuous administration of NIL, VAN, or MOB in animals significantly prolonged the action potential durations (APD) and increased susceptibility to arrhythmias. Using phosphoproteomic analysis, we identified proteins with altered phosphorylation levels after treatment with 3 μM NIL, VAN, and MOB for 1.5 h. Using these identified proteins as substrates, we performed kinase-substrate enrichment analysis to identify the kinases driving the changes in phosphorylation levels of these proteins. MAPK and WNK were both inhibited by NIL, VAN, and MOB. A selective inhibitor of WNK1, WNK-IN-11, induced concentration- and time-dependent cellrhythmias and prolonged field potential duration (FPD) in hiPSC-CMs in vitro; furthermore, administration in guinea pigs confirmed that WNK-IN-11 prolonged ventricular repolarization and increased susceptibility to arrhythmias. Fingding indicated that WNK1 inhibition had an in vivo and in vitro arrhythmogenic phenotype similar to TKIs. Additionally,three of TKIs reduced hERG and KCNQ1 expression at protein level, not at transcription level. Similarly, the knockdown of WNK1 decreased hERG and KCNQ1 protein expression in hiPSC-CMs. Collectively, our data suggest that the proarrhythmic effects of NIL, VAN, and MOB occur through a kinase inhibition mechanism. NIL, VAN, and MOB inhibit WNK1 kinase, leading to a decrease in hERG and KCNQ1 protein expression, thereby prolonging action potential repolarization and consequently cause arrhythmias.

Effects of macrophages on the proliferation and cardiac differentiation of human induced pluripotent stem cells

Background

Macrophage phenotypes switch from proinflammatory (M1) to anti-inflammatory (M2) following myocardial injury. Implanted stem cells (e.g., induced pluripotent stem cells (iPSCs)) for cardiomyogenesis will inevitably contact the inflammatory environment at the myocardial infarction site. To understand how the macrophages affect the behavior of iPSCs, therefore, improve the therapeutic efficacy, we generated three macrophage subtypes and assessed their effects on the proliferation, cardiac differentiation, and maturation of iPSCs.

Methods

M0, M1, and M2 macrophages were polarized using cytokines, and their properties were confirmed by the expression of specific markers using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence. The effects of macrophages on iPSCs were studied using Transwell co-culture models. The proliferative ability of iPSCs was investigated by cell counting and CCK-8 assays. The cardiac differentiation ability of iPSCs was determined by the cardiomyocyte (CM) yield. The maturation of CM was analyzed by the expression of cardiac-specific genes using RT-qPCR, the sarcomere organization using immunofluorescence, and the mitochondrial function using oxidative respiration analysis.

Results

The data showed that the co-culture of iPSCs with M0, M1, or M2 macrophages significantly decreased iPSCs’ proliferative ability. M2 macrophages did not affect the CM yield during the cardiac differentiation of iPSCs. Still, they promoted the maturation of CM by improving sarcomeric structures, increasing contractile- and ion transport-associated gene expression, and enhancing mitochondrial respiration. M0 macrophages did not significantly affect the cardiomyogenesis ability of iPSCs during co-culture. In contrast, co-culture with M1 macrophages significantly reduced the cardiac differentiation and maturation of iPSCs.

Conclusions

M1- or M2-polarized macrophages play critical roles in the proliferation, cardiac differentiation, and maturation of iPSCs, providing knowledge to improve the outcomes of stem cell regeneration therapy.

Deciphering Common Long QT Syndrome Using CRISPR/Cas9 in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes

From carrying potentially pathogenic genes to severe clinical phenotypes, the basic research in the inherited cardiac ion channel disease such as long QT syndrome (LQTS) has been a significant challenge in explaining gene-phenotype heterogeneity. These have opened up new pathways following the parallel development and successful application of stem cell and genome editing technologies. Stem cell-derived cardiomyocytes and subsequent genome editing have allowed researchers to introduce desired genes into cells in a dish to replicate the disease features of LQTS or replace causative genes to normalize the cellular phenotype. Importantly, this has made it possible to elucidate potential genetic modifiers contributing to clinical heterogeneity and hierarchically manage newly identified variants of uncertain significance (VUS) and more therapeutic options to be tested in vitro. In this paper, we focus on and summarize the recent advanced application of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) combined with clustered regularly interspaced short palindromic repeats/CRISPR-associated system 9 (CRISPR/Cas9) in the interpretation for the gene-phenotype relationship of the common LQTS and presence challenges, increasing our understanding of the effects of mutations and the physiopathological mechanisms in the field of cardiac arrhythmias.

Human Engineered Heart Tissue Models for Disease Modeling and Drug Discovery

The emergence of human induced pluripotent stem cells (hiPSCs) and efficient differentiation of hiPSC-derived cardiomyocytes (hiPSC-CMs) induced from diseased donors have the potential to recapitulate the molecular and functional features of the human heart. Although the immaturity of hiPSC-CMs, including the structure, gene expression, conduct, ion channel density, and Ca²⁺ kinetics, is a major challenge, various attempts to promote maturation have been effective. Three-dimensional cardiac models using hiPSC-CMs have achieved these functional and morphological maturations, and disease models using patient-specific hiPSC-CMs have furthered our understanding of the underlying mechanisms and effective therapies for diseases. Aside from the mechanisms of diseases and drug responses, hiPSC-CMs also have the potential to evaluate the safety and efficacy of drugs in a human context before a candidate drug enters the market and many phases of clinical trials. In fact, novel drug testing paradigms have suggested that these cells can be used to better predict the proarrhythmic risk of candidate drugs. In this review, we overview the current strategies of human engineered heart tissue models with a focus on major cardiac diseases and discuss perspectives and future directions for the real application of hiPSC-CMs and human engineered heart tissue for disease modeling, drug development, clinical trials, and cardiotoxicity tests.

Gene Editing in Pluripotent Stem Cells and Their Derived Organoids

With the rapid rise in gene-editing technology, pluripotent stem cells (PSCs) and their derived organoids have increasingly broader and practical applications in regenerative medicine. Gene-editing technologies, from large-scale nucleic acid endonucleases to CRISPR, have ignited a global research and development boom with significant implications in regenerative medicine. The development of regenerative medicine technologies, regardless of whether it is PSCs or gene editing, is consistently met with controversy. Are the tools for rewriting the code of life a boon to humanity or a Pandora's box? These technologies raise concerns regarding ethical issues, unexpected mutations, viral infection, etc. These concerns remain even as new treatments emerge. However, the potential negatives cannot obscure the virtues of PSC gene editing, which have, and will continue to, benefit mankind at an unprecedented rate. Here, we briefly introduce current gene-editing technology and its application in PSCs and their derived organoids, while addressing ethical concerns and safety risks and discussing the latest progress in PSC gene editing. Gene editing in PSCs creates visualized in vitro models, providing opportunities for examining mechanisms of known and unknown mutations and offering new possibilities for the treatment of cancer, genetic diseases, and other serious or refractory disorders. From model construction to treatment exploration, the important role of PSCs combined with gene editing in basic and clinical medicine studies is illustrated. The applications, characteristics, and existing challenges are summarized in combination with our lab experiences in this field in an effort to help gene-editing technology better serve humans in a regulated manner. Current preclinical and clinical trials have demonstrated initial safety and efficacy of PSC gene editing; however, for better application in clinical settings, additional investigation is warranted.

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.