<div><h4>Maresin-1 protects against pulmonary arterial hypertension by improving mitochondrial homeostasis through ALXR/HSP90α axis.</h4><i>Liu M, He H, Fan F, Qiu L, ... Yang G, Chen L</i><br /><b>Aims</b><br />Pulmonary arterial hypertension (PAH) is a progressive and lethal disease characterized by continuous proliferation of pulmonary arterial smooth muscle cell (PASMCs) and increased pulmonary vascular remodeling. Maresin-1 (MaR1) is a member of pro-resolving lipid mediators and exhibits protective effects on various inflammation-related diseases. Here we aimed to study the role of MaR1 in the development and progression of PAH and to explore the underlying mechanisms.<br /><b>Methods and results</b><br />We evaluated the effect of MaR1 treatment on PAH in both monocrotaline (MCT)-induced rat and hypoxia+SU5416 (HySu)-induced mouse models of pulmonary hypertension (PH). Plasma samples were collected from patients with PAH and rodent PH models to examine MaR1 production. Specific shRNA adenovirus or inhibitors were used to block the function of MaR1 receptors. The data showed that MaR1 significantly prevented the development and blunted the progression of PH in rodents. Blockade of the function of MaR1 receptor ALXR, but not LGR6 or RORα, with BOC-2, abolished the protective effect of MaR1 against PAH development and reduced its therapeutic potential. Mechanistically, we demonstrated that the MaR1/ALXR axis suppressed hypoxia-induced PASMCs proliferation and alleviated pulmonary vascular remodeling by inhibiting mitochondrial accumulation of heat shock protein 90α (HSP90α) and restoring mitophagy.<br /><b>Conclusion</b><br />MaR1 protects against PAH by improving mitochondrial homeostasis through ALXR/HSP90α axis and represents a promising target for PAH prevention and treatment.<br /><br />Copyright © 2023 Elsevier Ltd. All rights reserved.<br /><br /><small>J Mol Cell Cardiol: 25 May 2023; 181:15-30</small></div>

<div><h4>Suppression of myeloid YAP antagonizes adverse cardiac remodeling during pressure overload stress.</h4><i>Francisco J, Guan J, Zhang Y, Nakada Y, ... Sadoshima J, Del Re DP</i><br /><AbstractText>Inflammation is an integral component of cardiovascular disease and is thought to contribute to cardiac dysfunction and heart failure. While ischemia-induced inflammation has been extensively studied in the heart, relatively less is known regarding cardiac inflammation during non-ischemic stress. Recent work has implicated a role for Yes-associated protein (YAP) in modulating inflammation in response to ischemic injury; however, whether YAP influences inflammation in the heart during non-ischemic stress is not described. We hypothesized that YAP mediates a pro-inflammatory response during pressure overload (PO)-induced non-ischemic injury, and that targeted YAP inhibition in the myeloid compartment is cardioprotective. In mice, PO elicited myeloid YAP activation, and myeloid-specific YAP knockout mice (YAP<sup>F/F</sup>;LysM<sup>Cre</sup>) subjected to PO stress had better systolic function, and attenuated pathological remodeling compared to control mice. Inflammatory indicators were also significantly attenuated, while pro-resolving genes including Vegfa were enhanced, in the myocardium, and in isolated macrophages, of myeloid YAP KO mice after PO. Experiments using bone marrow-derived macrophages (BMDMs) from YAP KO and control mice demonstrated that YAP suppression shifted polarization toward a resolving phenotype. We also observed attenuated NLRP3 inflammasome priming and function in YAP deficient BMDMs, as well as in myeloid YAP KO hearts following PO, indicating disruption of inflammasome induction. Finally, we leveraged nanoparticle-mediated delivery of the YAP inhibitor verteporfin and observed attenuated PO-induced pathological remodeling compared to DMSO nanoparticle control treatment. These data implicate myeloid YAP as an important molecular nodal point that facilitates cardiac inflammation and fibrosis during PO stress and suggest that selective inhibition of YAP may prove a novel therapeutic target in non-ischemic heart disease.</AbstractText><br /><br />Copyright © 2023 Elsevier Ltd. All rights reserved.<br /><br /><small>J Mol Cell Cardiol: 24 May 2023; 181:1-14</small></div>

<div><h4>Distinct effects of cardiac mitochondrial calcium uniporter inactivation via EMRE deletion in the short and long term.</h4><i>Villanueva HC, Sung JH, Stevens JA, Zhang MJ, ... Townsend D, Liu JC</i><br /><AbstractText>Transport of Ca<sup>2+</sup> into mitochondria is thought to stimulate the production of ATP, a critical process in the heart\'s fight or flight response, but excess Ca<sup>2+</sup> can trigger cell death. The mitochondrial Ca<sup>2+</sup> uniporter complex is the primary route of Ca<sup>2+</sup> transport into mitochondria, in which the channel-forming protein MCU and the regulatory protein EMRE are essential for activity. In previous studies, chronic Mcu or Emre deletion differ from acute cardiac Mcu deletion in response to adrenergic stimulation and ischemia/reperfusion (I/R) injury, despite equivalent inactivation of rapid mitochondrial Ca<sup>2+</sup> uptake. To explore this discrepancy between chronic and acute loss of uniporter activity, we compared short-term and long-term Emre deletion using a novel conditional cardiac-specific, tamoxifen-inducible mouse model. After short-term Emre deletion (3 weeks post-tamoxifen) in adult mice, cardiac mitochondria were unable to take up Ca<sup>2+</sup>, had lower basal mitochondrial Ca<sup>2+</sup> levels, and displayed attenuated Ca<sup>2+</sup>-induced ATP production and mPTP opening. Moreover, short-term EMRE loss blunted cardiac response to adrenergic stimulation and improved maintenance of cardiac function in an ex vivo I/R model. We then tested whether the long-term absence of EMRE (3 months post-tamoxifen) in adulthood would lead to distinct outcomes. After long-term Emre deletion, mitochondrial Ca<sup>2+</sup> handling and function, as well as cardiac response to adrenergic stimulation, were similarly impaired as in short-term deletion. Interestingly, however, protection from I/R injury was lost in the long-term. These data suggest that several months without uniporter function are insufficient to restore bioenergetic response but are sufficient to restore susceptibility to I/R.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 23 May 2023; epub ahead of print</small></div>

<div><h4>Prediction of Kv11.1 potassium channel PAS-domain variants trafficking via machine learning.</h4><i>Fang X, Immadisetty K, Ramon GS, Hartle CM, ... Delisle BP, Kekenes-Huskey PM</i><br /><AbstractText>Congenital long QT syndrome (LQTS) is characterized by a prolonged QT-interval on an electrocardiogram (ECG). An abnormal prolongation in the QT-interval increases the risk for fatal arrhythmias. Genetic variants in several different cardiac ion channel genes, including KCNH2, are known to cause LQTS. Here, we evaluated whether structure-based molecular dynamics (MD) simulations and machine learning (ML) could improve the identification of missense variants in LQTS-linked genes. To do this, we investigated KCNH2 missense variants in the Kv11.1 channel protein shown to have wild type (WT) like or class II (trafficking-deficient) phenotypes in vitro. We focused on KCNH2 missense variants that disrupt normal Kv11.1 channel protein trafficking, as it is the most common phenotype for LQTS-associated variants. Specifically, we used computational techniques to correlate structural and dynamic changes in the Kv11.1 channel protein PAS domain (PASD) with Kv11.1 channel protein trafficking phenotypes. These simulations unveiled several molecular features, including the numbers of hydrating waters and hydrogen bonding pairs, as well as folding free energy scores, that are predictive of trafficking. We then used statistical and machine learning (ML) (Decision tree (DT), Random forest (RF), and Support vector machine (SVM)) techniques to classify variants using these simulation-derived features. Together with bioinformatics data, such as sequence conservation and folding energies, we were able to predict with reasonable accuracy (≈75%) which KCNH2 variants do not traffic normally. We conclude that structure-based simulations of KCNH2 variants localized to the Kv11.1 channel PASD led to an improvement in classification accuracy. Therefore, this approach should be considered to complement the classification of variant of unknown significance (VUS) in the Kv11.1 channel PASD.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 13 May 2023; epub ahead of print</small></div>

<div><h4>NLRP3 inflammasome-driven IL-1β and IL-18 contribute to lipopolysaccharide-induced septic cardiomyopathy.</h4><i>Fujimura K, Karasawa T, Komada T, Yamada N, ... Kario K, Takahashi M</i><br /><AbstractText>Sepsis is a life-threatening syndrome, and its associated mortality is increased when cardiac dysfunction and damage (septic cardiomyopathy [SCM]) occur. Although inflammation is involved in the pathophysiology of SCM, the mechanism of how inflammation induces SCM in vivo has remained obscure. NLRP3 inflammasome is a critical component of the innate immune system that activates caspase-1 (Casp1) and causes the maturation of IL-1β and IL-18 as well as the processing of gasdermin D (GSDMD). Here, we investigated the role of the NLRP3 inflammasome in a murine model of lipopolysaccharide (LPS)-induced SCM. LPS injection induced cardiac dysfunction, damage, and lethality, which was significantly prevented in NLRP3<sup>-/-</sup> mice, compared to wild-type (WT) mice. LPS injection upregulated mRNA levels of inflammatory cytokines (Il6, Tnfa, and Ifng) in the heart, liver, and spleen of WT mice, and this upregulation was prevented in NLRP3<sup>-/-</sup> mice. LPS injection increased plasma levels of inflammatory cytokines (IL-1β, IL-18, and TNF-α) in WT mice, and this increase was markedly inhibited in NLRP3<sup>-/-</sup> mice. LPS-induced SCM was also prevented in Casp1/11<sup>-/-</sup> mice, but not in Casp11<sup>mt</sup>, IL-1β<sup>-/-</sup>, IL-1α<sup>-/-</sup>, or GSDMD<sup>-/-</sup> mice. Notably, LPS-induced SCM was apparently prevented in IL-1β<sup>-/-</sup> mice transduced with adeno-associated virus vector expressing IL-18 binding protein (IL-18BP). Furthermore, splenectomy, irradiation, or macrophage depletion alleviated LPS-induced SCM. Our findings demonstrate that the cross-regulation of NLRP3 inflammasome-driven IL-1β and IL-18 contributes to the pathophysiology of SCM and provide new insights into the mechanism underlying the pathogenesis of SCM.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 10 May 2023; epub ahead of print</small></div>

<div><h4>Cardiac protein kinase D1 ablation alters the myocytes β-adrenergic response.</h4><i>Hernandez JM, Ko CY, Mandel AR, Shen EY, ... Bossuyt J, Bers DM</i><br /><AbstractText>β-adrenergic (β-AR) signaling is essential for the adaptation of the heart to exercise and stress. Chronic stress leads to the activation of Ca<sup>2+</sup>/calmodulin-dependent kinase II (CaMKII) and protein kinase D (PKD). Unlike CaMKII, the effects of PKD on excitation-contraction coupling (ECC) remain unclear. To elucidate the mechanisms of PKD-dependent ECC regulation, we used hearts from cardiac-specific PKD1 knockout (PKD1 cKO) mice and wild-type (WT) littermates. We measured calcium transients (CaT), Ca<sup>2+</sup> sparks, contraction and L-type Ca<sup>2+</sup> current in paced cardiomyocytes under acute β-AR stimulation with isoproterenol (ISO; 100 nM). Sarcoplasmic reticulum (SR) Ca<sup>2+</sup> load was assessed by rapid caffeine (10 mM) induced Ca<sup>2+</sup> release. Expression and phosphorylation of ECC proteins phospholambam (PLB), troponin I (TnI), ryanodine receptor (RyR), sarcoendoplasmic reticulum Ca<sup>2+</sup> ATPase (SERCA) were evaluated by western blotting. At baseline, CaT amplitude and decay tau, Ca<sup>2+</sup> spark frequency, SR Ca<sup>2+</sup> load, L-type Ca<sup>2+</sup> current, contractility, and expression and phosphorylation of ECC protein were all similar in PKD1 cKO vs. WT. However, PKD1 cKO cardiomyocytes presented a diminished ISO response vs. WT with less increase in CaT amplitude, slower [Ca<sup>2+</sup>]<sub>i</sub> decline, lower Ca<sup>2+</sup> spark rate and lower RyR phosphorylation, but with similar SR Ca<sup>2+</sup> load, L-type Ca<sup>2+</sup> current, contraction and phosphorylation of PLB and TnI. We infer that the presence of PKD1 allows full cardiomyocyte β-adrenergic responsiveness by allowing optimal enhancement in SR Ca<sup>2+</sup> uptake and RyR sensitivity, but not altering L-type Ca<sup>2+</sup> current, TnI phosphorylation or contractile response. Further studies are necessary to elucidate the specific mechanisms by which PKD1 is regulating RyR sensitivity. We conclude that the presence of basal PKD1 activity in cardiac ventricular myocytes contributes to normal β-adrenergic responses in Ca<sup>2+</sup> handling.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 04 May 2023; epub ahead of print</small></div>

<div><h4>Comparing the effects of chemical Ca dyes and R-GECO on contractility and Ca transients in adult and human iPSC cardiomyocytes.</h4><i>Robinson P, Sparrow AJ, Psaras Y, Steeples V, ... Redwood C, Daniels MJ</i><br /><AbstractText>We compared commonly used BAPTA-derived chemical Ca<sup>2+</sup> dyes (fura2, Fluo-4, and Rhod-2) with a newer genetically encoded indicator (R-GECO) in single cell models of the heart. We assessed their performance and effects on cardiomyocyte contractility, determining fluorescent signal-to-noise ratios and sarcomere shortening in primary ventricular myocytes from adult mouse and guinea pig, and in human iPSC-derived cardiomyocytes. Chemical Ca<sup>2+</sup> dyes displayed dose-dependent contractile impairment in all cell types, and we observed a negative correlation between contraction and fluorescence signal-to-noise ratio, particularly for fura2 and Fluo-4. R-GECO had no effect on sarcomere shortening. BAPTA-based dyes, but not R-GECO, inhibited in vitro acto-myosin ATPase activity. The presence of fura2 accentuated or diminished changes in contractility and Ca<sup>2+</sup> handling caused by small molecule modulators of contractility and intracellular ionic homeostasis (mavacamten, levosimendan, and flecainide), but this was not observed when using R-GECO in adult guinea pig left ventricular cardiomyocytes. Ca<sup>2+</sup> handling studies are necessary for cardiotoxicity assessments of small molecules intended for clinical use. Caution should be exercised when interpreting small molecule studies assessing contractile effects and Ca<sup>2+</sup> transients derived from BAPTA-like chemical Ca<sup>2+</sup> dyes in cellular assays, a common platform for cardiac toxicology testing and mechanistic investigation of cardiac disease physiology and treatment.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 29 Apr 2023; epub ahead of print</small></div>

<div><h4>Reduced O-GlcNAcylation diminishes cardiomyocyte Ca dependent facilitation and frequency dependent acceleration of relaxation.</h4><i>Ednie AR, Paul-Onyia CD, Bennett ES</i><br /><AbstractText>Ca<sup>2+</sup> dependent facilitation (CDF) and frequency dependent acceleration of relaxation (FDAR) are regulatory mechanisms that potentiate cardiomyocyte Ca<sup>2+</sup> channel function and increase the rate of Ca<sup>2+</sup> sequestration following a Ca<sup>2+</sup>-release event, respectively, when depolarization frequency increases. CDF and FDAR likely evolved to maintain EC coupling at increased heart rates. Ca<sup>2+</sup>/calmodulin-dependent kinase II (CaMKII) was shown to be indispensable to both; however, the mechanisms remain to be completely elucidated. CaMKII activity can be modulated by post-translational modifications but if and how these modifications impact CDF and FDAR is unknown. Intracellular O-linked glycosylation (O-GlcNAcylation) is a post-translational modification that acts as a signaling molecule and metabolic sensor. In hyperglycemic conditions, CaMKII was shown to be O-GlcNAcylated resulting in pathologic activity. Here we sought to investigate whether O-GlcNAcylation impacts CDF and FDAR through modulation of CaMKII activity in a pseudo-physiologic setting. Using voltage-clamp and Ca<sup>2+</sup> photometry we show that cardiomyocyte CDF and FDAR are significantly diminished in conditions of reduced O-GlcNAcylation. Immunoblot showed that CaMKIIδ and calmodulin expression are increased but the autophosphorylation of CaMKIIδ and the muscle cell-specific CaMKIIβ isoform are reduced by 75% or more when O-GlcNAcylation is inhibited. We also show that the enzyme responsible for O-GlcNAcylation (OGT) can likely be localized in the dyad space and/or at the cardiac sarcoplasmic reticulum and is precipitated by calmodulin in a Ca<sup>2+</sup> dependent manner. These findings will have important implications for our understanding of how CaMKII and OGT interact to impact cardiomyocyte EC coupling in normal physiologic settings as well as in disease states where CaMKII and OGT may be aberrantly regulated.</AbstractText><br /><br />Copyright © 2023 Elsevier Ltd. All rights reserved.<br /><br /><small>J Mol Cell Cardiol: 28 Apr 2023; 180:10-21</small></div>

<div><h4>The role of P21-activated kinase (Pak1) in sinus node function.</h4><i>Pereira CH, Bare DJ, Rosas PC, Dias FAL, Banach K</i><br /><AbstractText>Sinoatrial node (SAN) dysfunction (SND) and atrial arrhythmia frequently occur simultaneously with a hazard ratio of 4.2 for new onset atrial fibrillation (AF) in SND patients. In the atrial muscle attenuated activity of p21-activated kinase 1 (Pak1) increases the risk for AF by enhancing NADPH oxidase 2 dependent production of reactive oxygen species (ROS). However, the role of Pak1 dependent ROS regulation in SAN function has not yet been determined. We hypothesize that Pak1 activity maintains SAN activity by regulating the expression of the hyperpolarization activated cyclic nucleotide gated cation channel (HCN). To determine Pak1 dependent changes in heart rate (HR) regulation we quantified the intrinsic sinus rhythm in wild type (WT) and Pak1 deficient (Pak1<sup>-/-</sup>) mice of both sexes in vivo and in isolated Langendorff perfused hearts. Pak1<sup>-/-</sup> hearts displayed an attenuated HR in vivo after autonomic blockage and in isolated hearts. The contribution of the Ca<sup>2+</sup> clock to pacemaker activity remained unchanged, but Ivabradine (3 μM), a blocker of HCN channels that are a membrane clock component, eliminated the differences in SAN activity between WT and Pak1<sup>-/-</sup> hearts. Reduced HCN4 expression was confirmed in Pak1<sup>-/-</sup> right atria. The reduced HCN activity in Pak1<sup>-/-</sup> could be rescued by class II HDAC inhibition (LMK235), ROS scavenging (TEMPOL) or attenuation of Extracellular Signal-Regulated Kinase (ERK) 1/2 activity (SCH772984). No sex specific differences in Pak1 dependent SAN regulation were determined. Our results establish Pak1 as a class II HDAC regulator and a potential therapeutic target to attenuate SAN bradycardia and AF susceptibility.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 20 Apr 2023; epub ahead of print</small></div>

<div><h4>OGFOD1 modulates the transcriptional and proteomic landscapes to alter isoproterenol-induced hypertrophy susceptibility.</h4><i>Rodriguez R, Harris M, Murphy E, Kennedy LM</i><br /><AbstractText>Cardiac hypertrophy is associated with increased translation. However, little is known of the mechanisms that regulate translation in hypertrophy. Members of the 2-oxoglutarate-dependent dioxygenase family regulate several aspects of gene expression, including translation. An important member of this family is OGFOD1. Here, we show OGFOD1 accumulates in failing human hearts. Upon OGFOD1 deletion, murine hearts showed transcriptomic and proteomic changes, with only 21 proteins and mRNAs (0.6%) changing in the same direction. Additionally, OGFOD1-KO mice were protected from induced hypertrophy, supporting a role for OGFOD1 in the cardiac response to chronic stress.</AbstractText><br /><br />Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 19 Apr 2023; 179:42-46</small></div>

<div><h4>The selective RyR2 inhibitor ent-verticilide suppresses atrial fibrillation susceptibility caused by Pitx2 deficiency.</h4><i>Kim K, Blackwell DJ, Yuen SL, Thorpe MP, ... Cornea RL, Knollmann BC</i><br /><AbstractText>Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and a major cause of stroke and morbidity. The strongest genetic risk factors for AF in humans are variants on chromosome 4q25, near the paired-like homeobox transcription factor 2 gene PITX2. Although mice deficient in Pitx2 (Pitx2+/-) have increased AF susceptibility, the mechanism remains controversial. Recent evidence has implicated hyperactivation of the cardiac ryanodine receptor (RyR2) in Pitx2 deficiency, which may be associated with AF susceptibility. We investigated pacing-induced AF susceptibility and spontaneous Ca2+ release events in Pitx2 haploinsufficient (+/-) mice and isolated atrial myocytes to test the hypothesis that hyperactivity of RyR2 increases susceptibility to AF, which can be prevented by a potent and selective RyR2 channel inhibitor, ent-verticilide. Compared with littermate wild-type Pitx2+/+, the frequency of Ca2+ sparks and spontaneous Ca2+ release events increased in permeabilized and intact atrial myocytes from Pitx2+/- mice. Atrial burst pacing consistently increased the incidence and duration of AF in Pitx2+/- mice. The RyR2 inhibitor ent-verticilide significantly reduced the frequency of spontaneous Ca2+ release in intact atrial myocytes and attenuated AF susceptibility with reduced AF incidence and duration. Our data demonstrate that RyR2 hyperactivity enhances SR Ca2+ leak and AF inducibility in Pitx2+/- mice via abnormal Ca2+ handling. Therapeutic targeting of hyperactive RyR2 in AF using ent-verticilide may be a viable mechanism-based approach to treat atrial arrhythmias caused by Pitx2 deficiency.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 18 Apr 2023; epub ahead of print</small></div>

<div><h4>Endothelial cell direct reprogramming: Past, present, and future.</h4><i>Cho S, Aakash P, Lee S, Yoon YS</i><br /><AbstractText>Ischemic cardiovascular disease still remains as a leading cause of morbidity and mortality despite various medical, surgical, and interventional therapy. As such, cell therapy has emerged as an attractive option because it tackles underlying problem of the diseases by inducing neovascularization in ischemic tissue. After overall failure of adult stem or progenitor cells, studies attempted to generate endothelial cells (ECs) from pluripotent stem cells (PSCs). While endothelial cells (ECs) differentiated from PSCs successfully induced vascular regeneration, differentiating volatility and tumorigenic potential is a concern for their clinical applications. Alternatively, direct reprogramming strategies employ lineage-specific factors to change cell fate without achieving pluripotency. ECs have been successfully reprogrammed via ectopic expression of transcription factors (TFs) from endothelial lineage. The reprogrammed ECs induced neovascularization in vitro and in vivo and thus demonstrated their therapeutic value in animal models of vascular insufficiency. Methods of delivering reprogramming factors include lentiviral or retroviral vectors and more clinically relevant, non-integrative adenoviral and episomal vectors. Most studies made use of fibroblast as a source cell for reprogramming, but reprogrammability of other clinically relevant source cell types has to be evaluated. Specific mechanisms and small molecules that are involved in the aforementioned processes tackles challenges associated with direct reprogramming efficiency and maintenance of reprogrammed EC characteristics. After all, this review provides summary of past and contemporary methods of direct endothelial reprogramming and discusses the future direction to overcome these challenges to acquire clinically applicable reprogrammed ECs.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 18 Apr 2023; epub ahead of print</small></div>

<div><h4>Btg1 and Btg2 regulate neonatal cardiomyocyte cell cycle arrest.</h4><i>Velayutham N, Calderon MU, Alfieri CM, Padula SL, ... Scheijen B, Yutzey KE</i><br /><AbstractText>Rodent cardiomyocytes undergo mitotic arrest in the first postnatal week. Here, we investigate the role of transcriptional co-regulator Btg2 (B-cell translocation gene 2) and functionally-similar homolog Btg1 in postnatal cardiomyocyte cell cycling and maturation. Btg1 and Btg2 (Btg1/2) are expressed in neonatal C57BL/6 mouse left ventricles coincident with cardiomyocyte cell cycle arrest. Btg1/2 constitutive double knockout (DKO) mouse hearts exhibit increased pHH3+ mitotic cardiomyocytes compared to Wildtype at postnatal day (P)7, but not at P30. Similarly, neonatal AAV9-mediated Btg1/2 double knockdown (DKD) mouse hearts exhibit increased EdU+ mitotic cardiomyocytes compared to Scramble AAV9-shRNA controls at P7, but not at P14. In neonatal rat ventricular myocyte (NRVM) cultures, siRNA-mediated Btg1/2 single and double knockdown cohorts showed increased EdU+ cardiomyocytes compared to Scramble siRNA controls, without increase in binucleation or nuclear DNA content. RNAseq analyses of Btg1/2-depleted NRVMs support a role for Btg1/2 in inhibiting cell proliferation, and in modulating reactive oxygen species response pathways, implicated in neonatal cardiomyocyte cell cycle arrest. Together, these data identify Btg1 and Btg2 as novel contributing factors in mammalian cardiomyocyte cell cycle arrest after birth.</AbstractText><br /><br />Copyright © 2023 Elsevier Ltd. All rights reserved.<br /><br /><small>J Mol Cell Cardiol: 14 Apr 2023; 179:30-41</small></div>

<div><h4>Splicing factors in the heart: Uncovering shared and unique targets.</h4><i>Montañés-Agudo P, Pinto YM, Creemers EE</i><br /><AbstractText>Alternative splicing generates specialized protein isoforms that allow the heart to adapt during development and disease. The recent discovery that mutations in the splicing factor RNA-binding protein 20 (RBM20) cause a severe form of familial dilated cardiomyopathy has sparked a great interest in alternative splicing in the field of cardiology. Since then, identification of splicing factors controlling alternative splicing in the heart has grown at a rapid pace. Despite the intriguing observation that a certain overlap exists between the targets of some splicing factors, an integrated and systematic analysis of their splicing networks is missing. Here, we compared the splicing networks of individual splicing factors by re-analyzing original RNA-sequencing data from eight previously published mouse models, in which a single splicing factor has been genetically deleted (i.e. HNRNPU, MBNL1/2, QKI, RBM20, RBM24, RBPMS, SRSF3, SRSF4). We show that key splicing events in Camk2d, Ryr2, Tpm1, Tpm2 and Pdlim5 require the combined action of the majority of these splicing factors. Additionally, we identified common targets and pathways among splicing factors, with the largest overlap between the splicing networks of MBNL, QKI and RBM24. We also re-analyzed a large-scale RNA-sequencing study on hearts of 128 heart failure patients. Here, we observed that MBNL1, QKI and RBM24 expression varied greatly. This variation in expression correlated with differential splicing of their downstream targets as found in mice, suggesting that aberrant splicing by MBNL1, QKI and RBM24 might contribute to the disease mechanism in heart failure.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 12 Apr 2023; epub ahead of print</small></div>

<div><h4>Regulation of endogenous cardiomyocyte proliferation: The known unknowns.</h4><i>Secco I, Giacca M</i><br /><AbstractText>Myocardial regeneration in patients with cardiac damage is a long-sought goal of clinical medicine. In animal species in which regeneration occurs spontaneously, as well as in neonatal mammals, regeneration occurs through the proliferation of differentiated cardiomyocytes, which re-enter the cell cycle and proliferate. Hence, the reprogramming of the replicative potential of cardiomyocytes is an achievable goal, provided that the mechanisms that regulate this process are understood. Cardiomyocyte proliferation is under the control of a series of signal transduction pathways that connect extracellular cues to the activation of specific gene transcriptional programmes, eventually leading to the activation of the cell cycle. Both coding and non-coding RNAs (in particular, microRNAs) are involved in this regulation. The available information can be exploited for therapeutic purposes, provided that a series of conceptual and technical barriers are overcome. A major obstacle remains the delivery of pro-regenerative factors specifically to the heart. Improvements in the design of AAV vectors to enhance their cardiotropism and efficacy or, alternatively, the development of non-viral methods for nucleic acid delivery in cardiomyocytes are among the challenges ahead to progress cardiac regenerative therapies towards clinical application.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 06 Apr 2023; epub ahead of print</small></div>

<div><h4>CRaTER enrichment for on-target gene-editing enables generation of variant libraries in hiPSCs.</h4><i>Friedman CE, Fayer S, Pendyala S, Chien WM, ... Fowler DM, Yang KC</i><br /><AbstractText>Standard transgenic cell line generation requires screening 100-1000s of colonies to isolate correctly edited cells. We describe CRISPRa On-Target Editing Retrieval (CRaTER) which enriches for cells with on-target knock-in of a cDNA-fluorescent reporter transgene by transient activation of the targeted locus followed by flow sorting to recover edited cells. We show CRaTER recovers rare cells with heterozygous, biallelic-editing of the transcriptionally-inactive MYH7 locus in human induced pluripotent stem cells (hiPSCs), enriching on average 25-fold compared to standard antibiotic selection. We leveraged CRaTER to enrich for heterozygous knock-in of a library of variants in MYH7, a gene in which missense mutations cause cardiomyopathies, and recovered hiPSCs with 113 different variants. We differentiated these hiPSCs to cardiomyocytes and show MHC-β fusion proteins can localize as expected. Additionally, single-cell contractility analyses revealed cardiomyocytes with a pathogenic, hypertrophic cardiomyopathy-associated MYH7 variant exhibit salient HCM physiology relative to isogenic controls. Thus, CRaTER substantially reduces screening required for isolation of gene-edited cells, enabling generation of functional transgenic cell lines at unprecedented scale.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 03 Apr 2023; epub ahead of print</small></div>

<div><h4>InsPR-RyR channel crosstalk augments sarcoplasmic reticulum Ca release and arrhythmogenic activity in post-MI pig cardiomyocytes.</h4><i>Jin X, Meletiou A, Chung J, Tilunaite A, ... Sipido K, Roderick HL</i><br /><AbstractText>Ca<sup>2+</sup> transients (CaT) underlying cardiomyocyte (CM) contraction require efficient Ca<sup>2+</sup> coupling between sarcolemmal Ca<sup>2+</sup> channels and sarcoplasmic reticulum (SR) ryanodine receptor Ca<sup>2+</sup> channels (RyR) for their generation; reduced coupling in disease contributes to diminished CaT and arrhythmogenic Ca<sup>2+</sup> events. SR Ca<sup>2+</sup> release also occurs via inositol 1,4,5-trisphosphate receptors (InsP<sub>3</sub>R) in CM. While this pathway contributes negligeably to Ca<sup>2+</sup> handling in healthy CM, rodent studies support a role in altered Ca<sup>2+</sup> dynamics and arrhythmogenic Ca<sup>2+</sup> release involving InsP<sub>3</sub>R crosstalk with RyRs in disease. Whether this mechanism persists in larger mammals with lower T-tubular density and coupling of RyRs is not fully resolved. We have recently shown an arrhythmogenic action of InsP<sub>3</sub>-induced Ca<sup>2+</sup> release (IICR) in end stage human heart failure, often associated with underlying ischemic heart disease (IHD). How IICR contributes to early stages of disease is however not determined but highly relevant. To access this stage, we chose a porcine model of IHD, which shows substantial remodelling of the area adjacent to the infarct. In cells from this region, IICR preferentially augmented Ca<sup>2+</sup> release from non-coupled RyR clusters that otherwise showed delayed activation during the CaT. IICR in turn synchronised Ca<sup>2+</sup> release during the CaT but also induced arrhythmogenic delayed afterdepolarizations and action potentials. Nanoscale imaging identified co-clustering of InsP<sub>3</sub>Rs and RyRs, thereby allowing Ca<sup>2+</sup>-mediated channel crosstalk. Mathematical modelling supported and further delineated this mechanism of enhanced InsP<sub>3</sub>R-RyRs coupling in MI. Our findings highlight the role of InsP<sub>3</sub>R-RyR channel crosstalk in Ca<sup>2+</sup> release and arrhythmia during post-MI remodelling.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 30 Mar 2023; epub ahead of print</small></div>

<div><h4>Reprogramming of cardiac cell fate as a therapeutic strategy for ischemic heart disease.</h4><i>Garry GA, Olson EN</i><br /><AbstractText>Direct reprogramming of resident cardiac fibroblasts to induced cardiomyocytes is an attractive therapeutic strategy to restore function and remuscularize the injured heart. The cardiac transcription factors Gata4, Mef2c, and Tbx5 have been the mainstay of direct cardiac reprogramming strategies for the past decade. Yet, recent discoveries have identified alternative epigenetic factors capable of reprogramming human cells in the absence of these canonical factors. Further, single-cell genomics evaluating cellular maturation and epigenetics in the setting of injury and heart failure models following reprogramming have continued to inform the mechanistic underpinnings of this process and point toward future areas of discovery for the field. These discoveries and others covered in this review have provided complementary approaches that further enhance the effectiveness of reprogramming as a means of promoting cardiac regeneration following myocardial infarction and heart failure.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 28 Mar 2023; epub ahead of print</small></div>

<div><h4>High-quality nuclei isolation from postmortem human heart muscle tissues for single-cell studies.</h4><i>Araten S, Mathieu R, Jetly A, Shin H, ... Chen MH, Choudhury S</i><br /><AbstractText>Single-cell approaches have become an increasingly popular way of understanding the genetic factors behind disease. Isolation of DNA and RNA from human tissues is necessary to analyze multi-omic data sets, providing information on the single-cell genome, transcriptome, and epigenome. Here, we isolated high-quality single-nuclei from postmortem human heart tissues for DNA and RNA analysis. Postmortem human tissues were obtained from 106 individuals, 33 with a history of myocardial disease, diabetes, or smoking, and 73 controls without heart disease. We demonstrated that the Qiagen EZ1 instrument and kit consistently isolated genomic DNA of high yield, which can be used for checking DNA quality before conducting single-cell experiments. Here, we provide a method for single-nuclei isolation from cardiac tissue, otherwise known as the SoNIC method, which allows for the isolation of single cardiomyocyte nuclei from postmortem tissue by nuclear ploidy status. We also provide a detailed quality control measure for single-nuclei whole genome amplification and a pre-amplification method for confirming genomic integrity.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 26 Mar 2023; epub ahead of print</small></div>

<div><h4>Role and therapeutic potential of gelsolin in atherosclerosis.</h4><i>Zhang Q, Xiao-HuiWen , Tang SL, Zhao ZW, Tang CK</i><br /><AbstractText>Atherosclerosis is the major pathophysiological basis of a variety of cardiovascular diseases and has been recognized as a lipid-driven chronic inflammatory disease. Gelsolin (GSN) is a member of the GSN family. The main function of GSN is to cut and seal actin filaments to regulate the cytoskeleton and participate in a variety of biological functions, such as cell movement, morphological changes, metabolism, apoptosis and phagocytosis. Recently, more and more evidences have demonstrated that GSN is Closely related to atherosclerosis, involving lipid metabolism, inflammation, cell proliferation, migration and thrombosis. This article reviews the role of GSN in atherosclerosis from inflammation, apoptosis, angiogenesis and thrombosis.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 24 Mar 2023; epub ahead of print</small></div>

<div><h4>Indoxyl-sulfate activation of the AhR- NF-κB pathway promotes interleukin-6 secretion and the subsequent osteogenic differentiation of human valvular interstitial cells from the aortic valve.</h4><i>Candellier A, Issa N, Grissi M, Brouette T, ... Boudot C, Hénaut L</i><br /><b>Background</b><br />Calcific aortic stenosis (CAS) is more prevalent, occurs earlier, progresses faster and has worse outcomes in patients with chronic kidney disease (CKD). The uremic toxin indoxyl sulfate (IS) is powerful predictor of cardiovascular mortality in these patients and a strong promoter of ectopic calcification whose role in CAS remains poorly studied. The objective of this study was to evaluate whether IS influences the mineralization of primary human valvular interstitial cells (hVICs) from the aortic valve.<br /><b>Methods</b><br />Primary hVICs were exposed to increasing concentrations of IS in osteogenic medium (OM). The hVICs\' osteogenic transition was monitored by qRT-PCRs for BMP2 and RUNX2 mRNA. Cell mineralization was assayed using the o-cresolphthalein complexone method. Inflammation was assessed by monitoring NF-κB activation using Western blots as well as IL-1β, IL-6 and TNF-α secretion by ELISAs. Small interfering RNA (siRNA) approaches enabled us to determine which signaling pathways were involved.<br /><b>Results</b><br />Indoxyl-sulfate increased OM-induced hVICs osteogenic transition and calcification in a concentration-dependent manner. This effect was blocked by silencing the receptor for IS (the aryl hydrocarbon receptor, AhR). Exposure to IS promoted p65 phosphorylation, the blockade of which inhibited IS-induced mineralization. Exposure to IS promoted IL-6 secretion by hVICs, a phenomenon blocked by silencing AhR or p65. Incubation with an anti-IL-6 antibody neutralized IS\'s pro-calcific effects.<br /><b>Conclusion</b><br />IS promotes hVIC mineralization through AhR-dependent activation of the NF-κB pathway and the subsequent release of IL-6. Further research should seek to determine whether targeting inflammatory pathways can reduce the onset and progression of CKD-related CAS.<br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 24 Mar 2023; epub ahead of print</small></div>

<div><h4>Cellular reprogramming of fibroblasts in heart regeneration.</h4><i>Chi C, Song K</i><br /><AbstractText>Myocardial infarction causes the loss of cardiomyocytes and the formation of cardiac fibrosis due to the activation of cardiac fibroblasts, leading to cardiac dysfunction and heart failure. Unfortunately, current therapeutic interventions can only slow the disease progression. Furthermore, they cannot fully restore cardiac function, likely because the adult human heart lacks sufficient capacity to regenerate cardiomyocytes. Therefore, intensive efforts have focused on developing therapeutics to regenerate the damaged heart. Several strategies have been intensively investigated, including stimulation of cardiomyocyte proliferation, transplantation of stem cell-derived cardiomyocytes, and conversion of fibroblasts into cardiac cells. Resident cardiac fibroblasts are critical in the maintenance of the structure and contractility of the heart. Fibroblast plasticity makes this type of cells be reprogrammed into many cell types, including but not limited to induced pluripotent stem cells, induced cardiac progenitor cells, and induced cardiomyocytes. Fibroblasts have become a therapeutic target due to their critical roles in cardiac pathogenesis. This review summarizes the reprogramming of fibroblasts into induced pluripotent stem cell-derived cardiomyocytes, induced cardiac progenitor cells, and induced cardiomyocytes to repair a damaged heart, outlines recent findings in utilizing fibroblast-derived cells for heart regeneration, and discusses the limitations and challenges.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 23 Mar 2023; epub ahead of print</small></div>

<div><h4>Optogenetic termination of atrial tachyarrhythmias by brief pulsed light stimulation.</h4><i>Nakao M, Watanabe M, Miquerol L, Natsui H, ... de Vries AAF, Anzai T</i><br /><b>Aims</b><br />The most efficient way to acutely restore sinus rhythm from atrial fibrillation (AF) is electrical cardioversion, which is painful without adequate sedation. Recent studies in various experimental models have indicated that optogenetic termination of AF using light-gated ion channels may provide a myocardium-specific and potentially painless alternative future therapy. However, its underlying mechanism(s) remain(s) incompletely understood. As brief pulsed light stimulation, even without global illumination, can achieve optogenetic AF termination, besides direct conduction block also modulation of action potential (AP) properties may be involved in the termination mechanism. We studied the relationship between optogenetic AP duration (APD) and effective refractory period (ERP) prolongation by brief pulsed light stimulation and termination of atrial tachyarrhythmia (AT).<br /><b>Methods and results</b><br />Hearts from transgenic mice expressing the H134R variant of channelrhodopsin-2 in atrial myocytes were explanted and perfused retrogradely. AT induced by electrical stimulation was terminated by brief pulsed blue light stimulation (470 nm, 10 ms, 16 mW/mm<sup>2</sup>) with 68% efficacy. The termination rate was dependent on pulse duration and light intensity. Optogenetically imposed APD and ERP changes were systematically examined and optically monitored. Brief pulsed light stimulation (10 ms, 6 mW/mm<sup>2</sup>) consistently prolonged APD and ERP when light was applied at different phases of the cardiac action potential. Optical tracing showed light-induced APD prolongation during the termination of AT.<br /><b>Conclusion</b><br />Our results directly demonstrate that cationic channelrhodopsin activation by brief pulsed light stimulation prolongs the atrial refractory period suggesting that this is one of the key mechanisms of optogenetic termination of AT.<br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 23 Mar 2023; epub ahead of print</small></div>

<div><h4>Direct cardiac reprogramming: A new technology for cardiac repair.</h4><i>Brlecic PE, Bonham CA, Rosengart TK, Mathison M</i><br /><AbstractText>Cardiovascular disease is one of the leading causes of morbidity and mortality worldwide, with myocardial infarctions being amongst the deadliest manifestations. Reduced blood flow to the heart can result in the death of cardiac tissue, leaving affected patients susceptible to further complications and recurrent disease. Further, contemporary management typically involves a pharmacopeia to manage the metabolic conditions contributing to atherosclerotic and hypertensive heart disease, rather than regeneration of the damaged myocardium. With modern healthcare extending lifespan, a larger demographic will be at risk for heart disease, driving the need for novel therapeutics that surpass those currently available in efficacy. Transdifferentiation and cellular reprogramming have been looked to as potential methods for the treatment of diseases throughout the body. Specifically targeting the fibrotic cells in cardiac scar tissue as a source to be reprogrammed into induced cardiomyocytes remains an appealing option. This review aims to highlight the history of and advances in cardiac reprogramming and describe its translational potential as a treatment for cardiovascular disease.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 23 Mar 2023; epub ahead of print</small></div>

<div><h4>RyR2-targeting therapy prevents left ventricular remodeling and ventricular tachycardia in post-infarction heart failure.</h4><i>Fujii S, Kobayashi S, Chang Y, Nawata J, ... Yamamoto T, Yano M</i><br /><b>Background</b><br />Dantrolene binds to the Leu<sup>601</sup>-Cys<sup>620</sup> region of the N-terminal domain of cardiac ryanodine receptor (RyR2), which corresponds to the Leu<sup>590</sup>-Cys<sup>609</sup> region of the skeletal ryanodine receptor, and suppresses diastolic Ca<sup>2+</sup> leakage through RyR2.<br /><b>Objective</b><br />We investigated whether the chronic administration of dantrolene prevented left ventricular (LV) remodeling and ventricular tachycardia (VT) after myocardial infarction (MI) by the same mechanism with the mutation V3599K of RyR2, which indicated that the inhibition of diastolic Ca<sup>2+</sup> leakage occurred by enhancing the binding affinity of calmodulin (CaM) to RyR2.<br /><b>Methods and results</b><br />A left anterior descending coronary artery ligation MI model was developed in mice. Wild-type (WT) were divided into four groups: sham-operated mice (WT-Sham), sham-operated mice treated with dantrolene (WT-Sham-DAN), MI mice (WT-MI), and MI mice treated with dantrolene (WT-MI-DAN). Homozygous V3599K RyR2 knock-in (KI) mice were divided into two groups: sham-operated mice (KI-Sham) and MI mice (KI-MI). The mice were followed for 12 weeks. Survival was significantly higher in the WT-MI-DAN (73%) and KI-MI groups (70%) than the WT-MI group (40%). Echocardiography, pathological tissue, and epinephrine-induced VT studies showed that LV remodeling and VT were prevented in the WT-MI-DAN and KI-MI groups compared to the WT-MI group. An increase in diastolic Ca<sup>2+</sup> spark frequency and a decrease in the binding affinity of CaM to the RyR2 were observed at 12 weeks after MI in the WT-MI group, although significant improvements in these values were observed in the WT-MI-DAN and KI-MI groups.<br /><b>Conclusions</b><br />Pharmacological or genetic stabilization of RyR2 tetrameric structure improves survival after MI by suppressing LV remodeling and proarrhythmia.<br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 22 Mar 2023; epub ahead of print</small></div>

<div><h4>Cardiomyocyte hyperplasia and immaturity but not hypertrophy are characteristic features of patients with RASopathies.</h4><i>Drenckhahn JD, Nicin L, Akhouaji S, Krück S, ... Dimmeler S, Rupp S</i><br /><b>Aims</b><br />RASopathies are caused by mutations in genes that alter the MAP kinase pathway and are marked by several malformations with cardiovascular disorders as the predominant cause of mortality. Mechanistic insights in the underlying pathogenesis in affected cardiac tissue are rare. The aim of the study was to assess the impact of RASopathy causing mutations on the human heart.<br /><b>Methods and results</b><br />Using single cell approaches and histopathology we analyzed cardiac tissue from children with different RASopathy-associated mutations compared to age-matched dilated cardiomyopathy (DCM) and control hearts. The volume of cardiomyocytes was reduced in RASopathy conditions compared to controls and DCM patients, and the estimated number of cardiomyocytes per heart was ~4-10 times higher. Single nuclei RNA sequencing of a 13-year-old RASopathy patient (carrying a PTPN11 c.1528C > G mutation) revealed that myocardial cell composition and transcriptional patterns were similar to <1 year old DCM hearts. Additionally, immaturity of cardiomyocytes is shown by an increased MYH6/MYH7 expression ratio and reduced expression of genes associated with fatty acid metabolism. In the patient with the PTPN11 mutation activation of the MAP kinase pathway was not evident in cardiomyocytes, whereas increased phosphorylation of PDK1 and its downstream kinase Akt was detected.<br /><b>Conclusion</b><br />In conclusion, an immature cardiomyocyte differentiation status appears to be preserved in juvenile RASopathy patients. The increased mass of the heart in such patients is due to an increase in cardiomyocyte number (hyperplasia) but not an enlargement of individual cardiomyocytes (hypertrophy).<br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 20 Mar 2023; epub ahead of print</small></div>

<div><h4>Development of direct cardiac reprogramming for clinical applications.</h4><i>Yamada Y, Sadahiro T, Ieda M</i><br /><AbstractText>The incidence of cardiovascular diseases is increasing worldwide, and cardiac regenerative therapy has great potential as a new treatment strategy, especially for ischemic heart disease. Direct cardiac reprogramming is a promising new cardiac regenerative therapy that uses defined factors to induce transdifferentiation of endogenous cardiac fibroblasts (CFs) into induced cardiomyocyte-like cells (iCMs). In vivo reprogramming is expected to restore lost cardiac function without necessitating cardiac transplantation by converting endogenous CFs that exist abundantly in cardiac tissues directly into iCMs. Indeed, we and other groups have demonstrated that in vivo cardiac reprogramming improves cardiac contractile function and reduces scar area after acute myocardial infarction (MI). Recently, we demonstrated that in vivo cardiac reprogramming is an innovative cardiac regenerative therapy that not only regenerates the myocardium, but also reverses fibrosis by inducing the quiescence of pro-fibrotic fibroblasts, thereby improving heart failure in chronic MI. In this review, we summarize the recent progresses in in vivo cardiac reprogramming, and discuss its prospects for future clinical applications and the challenges of direct human reprogramming, which has been a longstanding issue.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 12 Mar 2023; epub ahead of print</small></div>

<div><h4>The utility of zebrafish cardiac arrhythmia model to predict the pathogenicity of KCNQ1 variants.</h4><i>Cui S, Hayashi K, Kobayashi I, Hosomichi K, ... Yamagishi M, Takamura M</i><br /><AbstractText>Genetic testing for inherited arrhythmias and discriminating pathogenic or benign variants from variants of unknown significance (VUS) is essential for gene-based medicine. KCNQ1 is a causative gene of type 1 long QT syndrome (LQTS), and approximately 30% of the variants found in type 1 LQTS are classified as VUS. We studied the role of zebrafish cardiac arrhythmia model in determining the clinical significance of KCNQ1 variants. We generated homozygous kcnq1 deletion zebrafish (kcnq1<sup>del/del</sup>) using the CRISPR/Cas9 and expressed human Kv7.1/MinK channels in kcnq1<sup>del/del</sup> embryos. We dissected the hearts from the thorax at 48-72 h post-fertilization and measured the transmembrane potential of the ventricle in the zebrafish heart. Action potential duration was calculated as the time interval between peak maximum upstroke velocity and 90% repolarization (APD90). The APD90 of kcnq1<sup>del/del</sup> embryos was 280 ± 47 ms, which was significantly shortened by injecting KCNQ1 wild-type (WT) cRNA and KCNE1 cRNA (168 ± 26 ms, P < 0.01 vs. kcnq1<sup>del/del</sup>). A study of two pathogenic variants (S277L and T587M) and one VUS (R451Q) associated with clinically definite LQTS showed that the APD90 of kcnq1<sup>del/del</sup> embryos with these mutant Kv7.1/MinK channels was significantly longer than that of Kv7.1 WT/MinK channels. Given the functional results of the zebrafish model, R451Q could be reevaluated physiologically from VUS to likely pathogenic. In conclusion, functional analysis using in vivo zebrafish cardiac arrhythmia model can be useful for determining the pathogenicity of loss-of-function variants in patients with LQTS.</AbstractText><br /><br />Copyright © 2023. Published by Elsevier Ltd.<br /><br /><small>J Mol Cell Cardiol: 08 Mar 2023; epub ahead of print</small></div>