Human Ventricle Research Articles

Geometry Does Impact on the Plane Strain Directions of the Human Left Ventricle, Irrespective of Disease.

The directions of primary strain lines of local deformation in Epicardial and Endocardial layers have been the subject of debate in recent years. Different methods led to different conclusions and a complete assessment of strain direction patterns in large and variable (in terms of pathology) cohorts of healthy and diseased patients is still lacking. Here, we use local deformation tensors in order to evaluate the angle of strain lines with respect to the horizontal circumferential direction in both Epi- and Endo-layers. We evaluated this on a large group of 193 subjects including 82 healthy control and 111 patients belonging to a great variety of pathological conditions. We found that Epicardial strain lines obliquely directed while those of Endocardium are almost circumferential. This result occurs irrespective of pathological condition. We propose that the geometric vinculum characterizing Endocardium and Epicardium in terms of different lever arm length and orientation of muscular fibers during contraction inescapably requires Endocardial strain lines to be circumferentially oriented and this is corroborated by experimental results. Further investigations on transmural structure of myocytes could couple results presented here in order to furnish additional experimental explanations.

InsP3R-RyR Ca2+ channel crosstalk facilitates arrhythmias in the failing human ventricle.

Dysregulated intracellular Ca2+ handling involving altered Ca2+ release from intracellular stores via RyR channels underlies both arrhythmias and reduced function in heart failure (HF). Mechanisms linking RyR dysregulation and disease are not fully established. Studies in animals support a role for InsP3 receptor Ca2+ channels (InsP3R) in pathological alterations in cardiomyocyte Ca2+ handling but whether these findings translate to the divergent physiology of human cardiomyocytes during heart failure is not determined. Using electrophysiological and Ca2+ recordings in human ventricular cardiomyocytes, we uncovered that Ca2+ release via InsP3Rs facilitated Ca2+ release from RyR and induced arrhythmogenic delayed after depolarisations and action potentials. InsP3R-RyR crosstalk was particularly increased in HF at RyR clusters isolated from the T-tubular network. Reduced SERCA activity in HF further facilitated the action of InsP3. Nanoscale imaging revealed co-localisation of InsP3Rs with RyRs in the dyad, which was increased in HF, providing a mechanism for augmented Ca2+ channel crosstalk. Notably, arrhythmogenic activity dependent on InsP3Rs was increased in tissue wedges from failing hearts perfused with AngII to promote InsP3 generation. These data indicate a central role for InsP3R-RyR Ca2+ signalling crosstalk in the pro-arrhythmic action of GPCR agonists elevated in HF and the potential for their therapeutic targeting.

Abstract 13146: Cardioprotective Effects of Mtss1 Reduction in Dilated Cardiomyopathy

Introduction: MTSS1 is an I-BAR protein that interacts with the actin cytoskeleton and the cell membrane and is speculated to play a role in cell motility, tumor metastasis, and cardiogenesis. Enhancer variants that reduce the expression of MTSS1 in the human left ventricle have been associated with cardioprotective traits in genome-wide association studies. However, the effect of MTSS1 downregulation on the development of heart disease has not been studied in experimental models. Here we tested the hypothesis that reduction of MTSS1 protects against dilated cardiomyopathy (DCM) in vitro and in vivo. Methods: We used CRISPR-Cas9 to knock out MTSS1 in induced pluripotent stem cells (iPSCs) harboring pathogenic variants from patients with severe DCM. DCM iPSC lines with and without MTSS1 were then differentiated into cardiomyocytes and phenotyped in vitro. A DCM mouse model containing a TPM1 D230N transgene was crossed with a mouse model heterozygous for Mtss1 knockout. Progeny from this F1 cross were assessed for differences in cardiac structure and function via echocardiography. Results: MTSS1 deletion restored the beta-adrenergic response in DCM iPSC cardiomyocytes. In parallel, Mtss1 deletion partially rescued DCM-associated phenotypes including left ventricular dilation and reduced ejection fraction in mice. Conclusions: Our initial results suggest a causal link between MTSS1 reduction and cardioprotection in DCM. Inhibiting cardiac MTSS1 may hold therapeutic potential for DCM, though the cellular mechanisms through which MTSS1 affects cardiac phenotypes remain under investigation.

Abstract 12618: Human And Mouse Demonstration Of The Reticulum-Mitochondria Ca 2+ Coupling As A New Therapeutic Target In Metabolic HFpEF

Context: Metabolic heart failure with preserved ejection fraction (HFpEF) is a frequent and disabling disease with yet no therapy and limited knowledge on the cardiac underlying molecular mechanisms. Ca 2+ transfer at mitochondria-associated reticular membranes (MAM) is crucial in the cardiomyocyte to tightly regulate mitochondrial Ca 2+ content and assure the excitation-energetics coupling. We aimed to specify the role of the MAM Ca 2+ coupling in both human and mouse hearts with metabolic HFpEF. Results: Mass spectrometry analysis of cardiac MAM showed an upregulation of cellular response to stress and lipid metabolism processes in two obesogenic T2D mouse models (16 weeks of high-fat high-sucrose diet, HFHSD vs standard diet, SD; 12-week old leptin-deficient ob/ob vs WT), while Ca 2+ transport was downregulated only in the HFHSD MAM. MAM Ca 2+ coupling assessment by adenoviral infection of a FRET-based mitochondrial Ca 2+ sensor, revealed a MAM Ca 2+ uncoupling in the HFHSD cardiomyocyte, leading to reduced mitochondrial Ca 2+ content and bioenergetics, while no change was measured in the ob/ob cell. HFHSD mice exhibited cardiac hypertrophy, diastolic dysfunction and mild strain rate reduction with preserved EF. Ob/ob mice only displayed strain rate reduction and concentric hypertrophy. Principal component analysis (PCA) demonstrated a divergence between the HFHSD group and the three others, as displayed by their scattering along the first PC (61% of variance) contributed mainly by strain rate, wall thickness, body weight and Ca 2+ peak amplitude. Proximity ligation assay revealed a decreased proximity between the reticular IP3-receptor and the mitochondrial porin VDAC in human left ventricle biopsies from T2D versus non-diabetic patients, obtained during valve replacement surgery: this suggests a reduced formation of the IP3R-driven Ca 2+ channeling complex. Conclusion: The ob/ob model does not recapitulate the main hallmarks of metabolic HFpEF and does not display any change in MAM Ca 2+ coupling. On the contrary, a MAM Ca 2+ uncoupling was detected both in the human T2D heart and in the heart of the HFHSD-induced metabolic HFpEF mouse, suggesting the reticulum-mitochondria Ca 2+ coupling as a critical therapeutic target in metabolic HFpEF.

Abstract 15753: Comparative Transcriptomics Analysis of Histone (De)acetylases and Cardiac Ion Channels in Human Induced Pluripotent Stem-Cell-Derived Cardiomyocytes vs. the Adult Human Heart

Epigenetic regulation is critical for cardiac electrophysiology and pathology. Epigenetic modulators, such as histone deacetylases (HDACs) and histone acetyltransferases (HATs) are known master regulators of gene expression. Recently, novel pharmacological agents, HDAC inhibitors, have been developed as treatments for cancer and immune diseases. The effects of HDAC inhibitors on cardiac ion channels (ICs) are of great interest. To exert specific gene modulation, we used small interfering RNAs against the known HDACs, including sirtuins, and deployed them in human induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs). Follow-up RNAseq data (n = 61) were compared to identically processed and normalized RNAseq data from human left ventricle (LV) from the GTEx database (n = 84). Gene expression of cardiac ICs displayed similar patterns, with some differences. For example, hiPSC-CMs showed upregulated CACNA1C, SLC8A1 and downregulated KCNJ2 and RYR2 compared to the adult LV, most of which are known distinctions (Fig. 1A). Correlative analysis (Fig. 1B) and partial least square regression models helped visualize links between HDACs/HATs, key transcription factors (TFs) and cardiac ICs. Powerful TFs, including MEF2A, GATA4, 6 exerted positive effect on ICs in hiPSC-CM and the adult LV. In the hiPSC-CMs, HDAC1, HDAC10 and SIRT6 were found to be the strongest predictors of the expression of individual cardiac ICs, as revealed by permutation importance. Further studies will involve determination of the role of different cell types using single-cell sequencing data from the adult LV. Our analysis offers new insights about the role of epigenetic modifiers on cardiac electrophysiology and informs the utility of hiPSC-CM as a scalable, experimental model for cardiotoxicity testing of HDAC inhibitors.

Abstract 11270: SGLT2 Expression in the Coronary Microvessel Endothelium and Cardiomyocytes of Cardiac Patients: Determinant Role of Low-Grade Inflammation and Induction of Endothelial Dysfunction

Introduction: Sodium-glucose co-transporter2 inhibitors (SGLT2i) showed benefit in major cardiovascular diseases characterized by low-grade inflammation. However, the role and function of SGLT2 in the heart remain unclear. Hypothesis: This study evaluated whether SGLT1/2 are expressed in the heart of patients with cardiac diseases, and determined the role of low-grade inflammation and the functional consequences. Methods: Human left ventricle (LV) biopsies were collected from 17 patients with aortic and mitral valves stenosis or hypertrophic cardiomyopathy at Strasbourg Hospital. Cultured endothelial cells (EC) were from pig coronary arteries. Expression levels were assessed by RT-qPCR, Western blot analysis and immunofluorescence staining, and the level of oxidative stress and nitric oxide (NO) using fluorescent probes. Results: SGLT1/2 protein levels were observed in the LV of cardiac patients and correlated p-p65 NFκB levels. SGLT2, VCAM-1 and TNF-α staining was observed in the endothelium of coronary microvessels and, to some extent, cardiomyocytes. TNF-α upregulated SGLT1 and 2, VCAM-1, AT1R and ACE expression and decreased that of eNOS and the bradykinin-stimulated NO formation in EC. The stimulatory effect of TNF-α was inhibited by an NF-kB inhibitor and SGLT2 siRNA but not by SGLT1 siRNA. Oxidative stress in LV sections and TNF-α-treated EC was inhibited by VAS-2870 (NADPH oxidase inhibitor), losartan (AT1R antagonist) and empagliflozin (SGLT2i), and in LV by infliximab (TNF-α receptor inhibitor). Conclusions: The findings indicate that SGLT2 is expressed in the LV of cardiac patients in the coronary endothelium and cardiomyocytes, and associated with their low-grade inflammatory status. Moreover, TNF-α upregulated the AT1R/NAPDH oxidase/SGLT2 crosstalk to sustain oxidative stress promoting endothelial dysfunction. Thus, SGLT2 appears as an interesting target to protect the coronary microcirculation.

Computational analysis of arrhythmogenesis in KCNH2 T618I mutation-associated short QT syndrome and the pharmacological effects of quinidine and sotalol

Short QT syndrome (SQTS) is a rare but dangerous genetic disease. In this research, we conducted a comprehensive in silico investigation into the arrhythmogenesis in KCNH2 T618I-associated SQTS using a multi-scale human ventricle model. A Markov chain model of IKr was developed firstly to reproduce the experimental observations. It was then incorporated into cell, tissue, and organ models to explore how the mutation provided substrates for ventricular arrhythmias. Using this T618I Markov model, we explicitly revealed the subcellular level functional alterations by T618I mutation, particularly the changes of ion channel states that are difficult to demonstrate in wet experiments. The following tissue and organ models also successfully reproduced the changed dynamics of reentrant spiral waves and impaired rate adaptions in hearts of T618I mutation. In terms of pharmacotherapy, we replicated the different effects of a drug under various conditions using identical mathematical descriptions for drugs. This study not only simulated the actions of an effective drug (quinidine) at various physiological levels, but also elucidated why the IKr inhibitor sotalol failed in SQT1 patients through profoundly analyzing its mutation-dependent actions.

Direct observation of a stable spiral wave reentry in ventricles of a whole human heart using optical mapping for voltage and calcium.

From the studies of Gordon Moe in the 1960s, functional reentry has been investigated as a mechanism for tachycardia and fibrillation; however, it was not until 1990 that optical mapping (OM) experiments using sheep hearts verified the existence of reentrant spiral waves.1 Eventually, it was shown that electromechanical 3-dimensional vortex filaments drive cardiac fibrillation.2 To date, only multiple complex and short-lived reentrant waves have been recorded using OM on human ventricles.3 The presence of single spiral waves in human ventricles has only been demonstrated using low-resolution intracardiac electrocardiograms (ECGs).

Spiral wave breakup: Optical mapping in an explanted human heart shows the transition from ventricular tachycardia to ventricular fibrillation and self-termination.

Since the first demonstration of ventricular fibrillation induction by electrical stimulation in 1850 by Hoffa and Ludwig, 1 Hoffa M. Ludwig C. Einige neue Versuche uber Herzbewegung. Zeitschr Rat Med. 1850; 9: 107-144 Google Scholar many mechanisms 2 Jalife J. Ventricular fibrillation: mechanisms of initiation and maintenance. Annu Rev Physiol. 2000; 62: 25-50 Crossref PubMed Scopus (288) Google Scholar ,3 Fenton F.H. Cherry E.M. Hastings H.M. Evans S.J. Multiple mechanisms of spiral wave breakup in a model of cardiac electrical activity. Chaos. 2002; 12: 852-892 Crossref PubMed Scopus (504) Google Scholar have been identified that initiate the complex dynamics of fibrillation. We report a high-resolution visualization of a spiral wave transitioning into multiple waves in human ventricles by using optical mapping (voltage and calcium) from the posterior epicardial surface (∼7 × 7 cm2) of an explanted heart from a 38-year-old female transplant recipient.

Comparative gross anatomy of epicardiac ganglionated nerve plexi on the human and sheep cardiac ventricles.

This study aimed to examine the distribution and quantitative parameters of the epicardiac ventricular neural ganglionated plexus in the hearts of humans and sheep, highlighting the differences of this plexus in humans and large models. Five non-sectioned pressure distended whole hearts of the human newborns and 10 hearts of newborn German black-faced lambs were investigated applying a histochemical method for acetylcholinesterase to stain epicardiac neural structures with their subsequent stereomicroscopic examination. In humans, the ventricular nerves are spread by four epicardiac nerve subplexuses, that is, the left and right coronary as well as the left and middle dorsal. In sheep, the ventricular nerves are spread by five epicardiac nerve subplexuses, that is, the left and right coronary, the left and middle dorsal and the right ventral ones. The ventricular epicardium involved up to 129 ganglia in humans and up to 198-in sheep. The largest number of the ventricular ganglionic cells in humans were located on the ventral side, in front of the conus arteriosus, while on sheep ventricles, the most numerous neurons distributed on the dorsal wall of the left ventricle. This comparative study of the morphological patterns of the human and sheep ventricles demonstrates that the sheep heart is neuroanatomically distinct from the human one and this must be taking into consideration using the sheep model for the heart physiology experiments.

Regulation of APD and Force by the Na+/Ca2+ Exchanger in Human-Induced Pluripotent Stem Cell-Derived Engineered Heart Tissue.

The physiological importance of NCX in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) is not well characterized but may depend on the relative strength of the current, compared to adult cardiomyocytes, and on the exact spatial arrangement of proteins involved in Ca2+ extrusion. Here, we determined NCX currents and its contribution to action potential and force in hiPSC-CMs cultured in engineered heart tissue (EHT). The results were compared with data from rat and human left ventricular tissue. The NCX currents in hiPSC-CMs were larger than in ventricular cardiomyocytes isolated from human left ventricles (1.3 ± 0.2 pA/pF and 3.2 ± 0.2 pA/pF for human ventricle and EHT, respectively, p < 0.05). SEA0400 (10 µM) markedly shortened the APD90 in EHT (by 26.6 ± 5%, p < 0.05) and, to a lesser extent, in rat ventricular tissue (by 10.7 ± 1.6%, p < 0.05). Shortening in human left ventricular preparations was small and not different from time-matched controls (TMCs; p > 0.05). Force was increased by the NCX block in rat ventricle (by 31 ± 5.4%, p < 0.05) and EHT (by 20.8 ± 3.9%, p < 0.05), but not in human left ventricular preparations. In conclusion, hiPSC-CMs possess NCX currents not smaller than human left ventricular tissue. Robust NCX block-induced APD shortening and inotropy makes EHT an attractive pharmacological model.

Effect of cilia-induced surface velocity on cerebrospinal fluid exchange in the lateral ventricles.

Ciliary motility disorders are known to cause hydrocephalus. The instantaneous velocity of cerebrospinal fluid (CSF) flow is dominated by artery pulsation, and it remains unclear why ciliary dysfunction results in hydrocephalus. In this study, we investigated the effects of cilia-induced surface velocity on CSF flow using computational fluid dynamics. A geometric model of the human ventricles was constructed using medical imaging data. The CSF produced by the choroid plexus and cilia-induced surface velocity were given as the velocity boundary conditions at the ventricular walls. We developed healthy and reduced cilia motility models based on experimental data of cilia-induced velocity in healthy wild-type and Dpcd-knockout mice. The results indicate that there is almost no difference in intraventricular pressure between healthy and reduced cilia motility models. Additionally, it was found that newly produced CSF from the choroid plexus did not spread to the anterior and inferior horns of the lateral ventricles in the reduced cilia motility model. These findings suggest that a ciliary motility disorder could delay CSF exchange in the anterior and inferior horns of the lateral ventricles.

Toward Hierarchical Assembly of Aligned Cell Sheets into a Conical Cardiac Ventricle Using Microfabricated Elastomers.

Despite current efforts in organ-on-chip engineering to construct miniature cardiac models, they often lack some physiological aspects of the heart, including fiber orientation. This motivates the development of bioartificial left ventricle models that mimic the myofiber orientation of the native ventricle. Herein, an approach relying on microfabricated elastomers that enables hierarchical assembly of 2D aligned cell sheets into a functional conical cardiac ventricle is described. Soft lithography and injection molding techniques are used to fabricate micro-grooves on an elastomeric polymer scaffold with three different orientations ranging from -60° to +60°, each on a separate trapezoidal construct. The width of the micro-grooves is optimized to direct the majority of cells along the groove direction and while periodic breaks are used to promote cell-cell contact. The scaffold is wrapped around a central mandrel to obtain a conical-shaped left ventricle model inspired by the size of a human left ventricle 19 weeks post-gestation. Rectangular micro-scale holes are incorporated to alleviate oxygen diffusional limitations within the 3D scaffold. Cardiomyocytes within the 3D left ventricle constructs showed high viability in all layers after 7 days of cultivation. The hierarchically assembled left ventricle also provided functional readouts such as calcium transients and ejection fraction.

Comparative Study of Transcriptome in the Hearts Isolated from Mice, Rats, and Humans.

The heart is a significant organ in mammalian life, and the heartbeat mechanism has been an essential focus of science. However, few studies have focused on species differences. Accordingly, challenges remain in studying genes that have universal functions across species and genes that determine species differences. Here, we analyzed transcriptome data in mouse, rat, and human atria, ventricles, and sinoatrial nodes (SA) obtained from different platforms and compared them by calculating specificity measure (SPM) values in consideration of species differences. Among the three heart regions, the species differences in SA were the greatest, and we searched for genes that determined the essential characteristics of SA, which was SHOX2 in our criteria. The SPM value of SHOX2 was prominently high across species. Similarly, by calculating SPM values, we identified 3 atrial-specific, 11 ventricular-specific, and 17 SA-specific markers. Ontology analysis identified 70 cardiac region- and species-specific ontologies. These results suggest that reanalyzing existing data by calculating SPM values may identify novel tissue-specific genes and species-dependent gene expression. This study identified the importance of SHOX2 as an SA-specific transcription factor, a novel cardiac regional marker, and species-dependent ontologies.

Bioinformatics and Experimental Analyses Reveal NFIC as an Upstream Transcriptional Regulator for Ischemic Cardiomyopathy.

Ischemic cardiomyopathy (ICM) caused by coronary artery disease always leads to myocardial infarction and heart failure. Identification of novel transcriptional regulators in ICM is an effective method to establish new diagnostic and therapeutic strategies. In this study, we used two RNA-seq datasets and one microarray dataset from different studies, including 25 ICM and 21 non-failing control (NF) samples of human left ventricle tissues for further analysis. In total, 208 differentially expressed genes (DEGs) were found by combining two RNA-seq datasets with batch effects removed. GO and KEGG analyses of DEGs indicated that the response to wounding, positive regulation of smooth muscle contraction, chromatin, PI3K-Akt signaling pathway, and transporters pathways are involved in ICM. Simple Enrichment Analysis found that NFIC-binding motifs are enriched in promoter regions of downregulated genes. The Gene Importance Calculator further proved that NFIC is vital. NFIC and its downstream genes were verified in the validating microarray dataset. Meanwhile, in rat cardiomyocyte cell line H9C2 cells, two genes (Tspan1 and Hopx) were confirmed, which decreased significantly along with knocking down Nfic expression. In conclusion, NFIC participates in the ICM process by regulating TSPAN1 and HOPX. NFIC and its downstream genes may be marker genes and potential diagnostic and therapeutic targets for ICM.

Towards advanced cardiac miRNA therapies through DNA-based nanostructures

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Proyecto MINECO-Ministerio de Ciencia e Innovación (Spain)- PID2019-105674RB-I00 Proyecto DGA- Diputación General de Aragón (Spain)- LMP128_21 Introduction Cardiac microRNAs (miRNAs) have been found to be dysregulated in cardiac disease and aging both in animal models and humans. Thanks to their pleiotropic effects, miRNAs are spotlighted as promising therapeutic targets to treat cardiac conditions. However, their low stability and potential off-target effects in vivo difficult the development of effective and safe miRNA therapies. Nanotechnology enables the fabrication of biocompatible carriers to perform targeted delivery of both conventional and advanced therapies. In particular, nanostructures built with DNA (DNS) have been successfully developed for miRNA therapies in cancer, but they have not been applied in cardiac therapy yet [1]. Purpose The main goal of this study is to demonstrate the capacity of DNS to deliver miRNA therapies in human cardiomyocytes. Methods Our group has identified MIR24-2 upregulated with age in the human left ventricle and miR24-2-5p to interact with genes related with the cardiac function, such as SERCA2 [2]. Different versions of DNS were designed and generated by self-assembly of DNA strands containing anti-miR24-2-5p capture segments. Physicochemical characterization of DNS was then conducted to determine their auto-assembling capacity, size, morphology and thermal stability. The characterization of the biological effect of the DNS was also conducted in vitro and in cell culture of HEK293 and human induced pluripotent stem cells (iPSC)-derived cardiomyocytes (iCM) to assess their cytotoxicity and internalization capacity. Results DNS were assembled correctly and reproducibly into carriers of around 30-50 nm. In vitro, the DNS showed thermal stability at physiological temperature, proper stability in serum and they disassembled specifically in the presence of the target miR24-2-5p sequence. In HEK293 and iCM cultures, the DNS showed lack of cytotoxicity demonstrating in vitro biocompatibility. DNS were efficiently internalized by HEK293, but the uptake capacity of DNS by iCM was remarkably lower. Conclusions We created and characterized biocompatible anti-miR-loaded DNS that effectively captured the target miR-24-2-5p in vitro. DNS internalized in iCM, but with lower efficiency than in HEK293 cells. Our results indicate that DNS are suitable candidates to carry miRNA therapies to human cardiac cells in vitro, but the observed cell-type specific differences suggest that future efforts need to be directed towards developing DNS functionalization capable of promoting efficient and specific carrier uptake in vivo by primary cardiac cells in vivo.

EP News: Basic and Translational

Pabel et al (Circ Res 2022;130:994, PMID 35193397) investigated the effects of atrial fibrillation (AF) on the human left ventricle (LV) by using ventricular tissues from patients with aortic stenosis and preserved LV function with sinus rhythm or rate-controlled AF. There were no differences in fibrosis; however, systolic Ca2+ transient amplitude was reduced in patients with AF. The results were confirmed in nonfailing donors with sinus rhythm compared with AF. Moreover, after 24 hours of AF simulation in vitro using arrhythmic pacing, human LV cardiomyocytes from nonfailing donors showed an impaired Ca2+ transient amplitude.

Establishing safe, effective ablation in the diseased human ventricle: an analysis of generator impedance and electrogram attenuation

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Biosense Webster Inc Background Predictors of effective and safe lesion delivery in the human left ventricle have not been established. Generator impedance (GI) drop and electrogram (EGM) attenuation are indices which can be used as surrogates for ablation lesion parameters. Tissue pops are a complication of myocardial overheating preceded by a rise in GI and can have adverse consequences. Purpose To establish the relationships between Ablation Index (AI), Force Time Integral (FTI) and contact force with GI and EGM attenuation. To establish factors early in ablation that are predictive of a GI rise. Methods Patients undergoing ventricular tachycardia ablation were recruited. All ablations were performed with contact force sensing surround flow catheters. Electrograms were collected pre and post ablation, with GI, AI, FTI measured during. Ablations were divided into low (LVM, &amp;lt; 0.50mV), intermediate (IVM, 0.51 – 1.50mV) and normal voltage (NVM, &amp;gt; 1.50mV) based upon pre-ablation bipolar EGM amplitude. Ablations with a 5% rise in GI from maximal drop were noted and predictors of this explored. Results In 15 patients, 402 ablations were analysed. Filtered percentage GI drop correlated with AI and FTI, (p &amp;lt; 0.0005, Spearman’s ρ = 0.522 and 0.524) and reached a plateau at 763AI and 713gs, a filtered GI drop of 7.5% (Figure 1). Shallower curves occurred progressively from NVM to IVM to LVM, (p &amp;lt; 0.0005), (Figure 2) The bipolar EGM significantly attenuated with ablation, (median attenuation 0.14mV, [29.3%], p &amp;lt;0.0005), but percentage attenuation did not correlate with AI or FTI. Parameters associated with a GI rise during ablation were greater mean CF to maximum GI drop, (p = 0.002), greater initial percentage GI drop at 5 seconds, (p &amp;lt; 0.0005), power of 50W (p = 0.005), and perpendicular orientation, (p = 0.006). Percentage GI drop at 5 seconds was the best predictor of ablations with a GI rise, (AUCROC 0.773; 95% CI 0.708 – 0.838; optimal cut-off 2.44%). Mean contact force to maximum GI drop was a poor predictor of a GI rise (AUCROC 0.647; 95% CI 0.577 – 0.718, optimal cut-off 14.7g). Conclusion During left ventricular ablation, AI of 763 and FTI of 713gs should be targeted, with a lower impedance drop observed for more scarred myocardium. A GI drop of &amp;lt;2.5% at 5 seconds and contact force &amp;lt; 15g should be used to optimise ablation safety.

Regulation of APD and force by Na+/Ca2+ exchanger in hiPSC-cardiomyocytes

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): BMBF Introduction Human induced pluripotent stem cell-derived cardiomyocytes (HiPSC-CM) are an emerging, powerful tool to study human cardiac physiology, pharmacology and toxicology, to model cardiovascular diseases or even to use for cardiac repair. Understanding the similarities and differences between hiPSC-CM and adult human cardiomyocytes is critical for their use. Here we focus on sodium calcium exchanger (NCX) who plays a crucial role in the Ca2+-homeostasis in the mammalian heart. Importantly, alterations in NCX expression in human heart are associated with various cardiac pathologies such as heart failure or arrhythmias. In order to investigate whether hiPSC-CM could serve as model for adult human heart NCX we measured the properties of NCX in hiPSC-CM and human ventricular tissue. Rat ventricular tissue was used for comparison. Methods HiPSC-CM were differentiated from a healthy iPSC line and dissociated from engineered heart tissue (EHT). Adult human and rat cardiomyocytes were digested from ventricular samples. We measured NCX current by the whole-cell patch clamp technique at 37 °C. Standard sharp microelectrodes were used to record action potentials (AP). Contractile force in human and rat ventricular samples was measured isometrically. A video-optical contractility test system was used to measure force in EHT. SEA0400 (10 µM) was used to block NCX. Results NCX currents could be measured in every hiPSC-CM. The NCX current densities in hiPSC-CM were larger than in human ventricular cardiomyocytes (3.2±0.2 pA/pF n=28 vs. 1.3±0.2 pA/pF n=15, p&amp;lt;0.05), but lower than reported for rat left ventricular cardiomyocytes using the same protocol. SEA0400 shortened APD90 markedly in EHT (264.1±24.9 ms to 191±31.6 ms, n=4) and to a lesser extent in rat ventricular tissue (54.4±3.9 ms to 48.9±4.2 ms, n=7). Shortening in human left ventricular preparations was tiny (320±22.1 ms to 305.5±20.3 ms, n=6) and not different from time-matched controls (TMC). Resting membrane potential, action potential amplitude and upstroke velocity were not affected neither in EHT nor in left ventricular preparations (rat and human). Force was significantly increased by NCX block in rat ventricle (by 31±5.4%, n=18) and EHT (by 20.8±3.9%, n=4), but in human left ventricular preparations there was only a tendency to attenuate spontaneous run-down (-3.7±4.3% n=8 with SEA vs. -6.2±3.7% n=12 in TMC). Conclusion HiPSC-CM possess NCX in the physiological range. HiPSC-CM show NCX-effects on APD and force as predicted from rat ventricle and in full accordance with cardiac physiology. Lack of NCX effect in human adult ventricles that had been already reported previously needs further investigations.

Ginsenoside Rh2 mitigates doxorubicin-induced cardiotoxicity by inhibiting apoptotic and inflammatory damage and weakening pathological remodelling in breast cancer-bearing mice.

ObjectivesThere are presently a few viable ways to reduce cardiotoxicity of doxorubicin (Dox). The combination of chemotherapy agents with natural compounds delivers greater efficacy and reduces adverse effects in recent researches for cancer treatment. Here, we examined the potential effect of ginsenoside Rh2 on a Dox‐based regimen in chemotherapy treatment.Materials and MethodsHuman breast tumour (MDA‐MB‐231) xenograft nude mice, human cardiac ventricle fibroblasts, and human umbilical vein endothelial cells (HUVEC) were employed in the present study. Histology, immunohistochemistry, immunofluorescence, western blot, antibody array, and RNA‐sequencing analyses were utilized to assess the protective effect of Rh2 on cardiotoxicity induced by Dox and the underlying mechanisms.ResultsRh2‐reduced cardiotoxicity by inhibiting the cardiac histopathological changes, apoptosis and necrosis, and consequent inflammation. Pathological remodelling was attenuated by reducing fibroblast to myofibroblast transition (FMT) and endothelial–mesenchymal transition (EndMT) in hearts. RNA‐sequencing analysis showed that Dox treatment predominantly targets cell cycle and attachment of microtubules and boosted tumour necrosis, chemokine and interferon‐gamma production, response to cytokine and chemokine, and T cell activation, whereas Rh2 regulated these effects. Intriguingly, Rh2 also attenuated fibrosis via promoting senescence in myofibroblasts and reversing established myofibroblast differentiation in EndMT.ConclusionsRh2 regulates multiple pathways in the Dox‐provoked heart, proposing a potential candidate for cancer supplement and therapy‐associated cardiotoxicity.