BACKGROUND: Pulsed-field ablation (PFA) of atrial fibrillation (AF) is a new method in clinical practice. Despite a favorable safety profile of PFA in AF ablation, rare cases of renal failure, probably due to hemolysis, have been recently reported.
OBJECTIVE: The aim of this study was to determine the rate of hemolysis and cardiac cell death during in vitro PFA with different electric field intensities.
METHODS: Blood samples from healthy volunteers and mouse HL-1 cardiomyocyte cell lines were subjected to in vitro irreversible electroporation (IRE) using 216 bipolar pulses, each lasting 2 μs with 5 μs intervals, repeated 20 times at a frequency of 1 Hz. These pulses varied in from 500 to 1500 V. Cell-free hemoglobin levels were assessed spectrophotometrically, and red blood cell microparticles (RBCμ) were evaluated using flow cytometry. Cardiomyocyte death was quantified using propidium iodide.
RESULTS: PF energy (1000 V/cm, 1250 V/cm, and 1500 V/cm) was associated with a significant increase in cell-free hemoglobin (0.31 ± 0.16 g/l, 2.33 ± 0.90 g/l, and 5.7 ± 0.20 g/l, p< 0.05), and similar increase in the concentration of RBCμ. Significant rates of cardiomyocyte death were observed at electric field strengths of 750 V/cm, 1000 V/cm, 1250 V/cm and 1500 V/cm (26.5 ± 5.9%, 44.3 ± 6.2%, 55.5 ± 6.9% and 74.5 ± 17.8% of cardiomyocytes, p < 0.05).
CONCLUSIONS: The most effective induction of cell death in vitro was observed at 1500 V/cm. This intensity was also associated with a significant degree of hemolysis.

Short electric field pulses represent a novel potential approach for achieving uniform electroporation within tissue containing elongated cells oriented in various directions, such as electroporation-based cardiac ablation procedures. In this study, we investigated how electroporation with nanosecond pulses with respect to different pulse shapes (unipolar, bipolar, and asymmetric) influences cardiomyocyte permeabilization and gene transfer. For this purpose, rat cardiomyocytes (H9c2) were used. The efficacy of the pulsed electric field protocols was assessed by flow cytometry and electrogene transfer by fluorescent and holotomographic microscopy. The response of the cells was assessed by the metabolic activity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide [MTT] assay), F-actin distribution in cells by confocal microscopy, and muscle atrophy F-box (MAFbx) marker. We show nano- and microsecond pulse protocols, which are not cytotoxic for cardiac muscle cells and can be efficiently used for gene electrotransfection. Asymmetric nanosecond pulsed electric fields were similarly efficient in plasmid delivery as microsecond and millisecond protocols. However, the millisecond protocol induced a higher MAFbx expression in H9c2 cells.

[This corrects the article DOI: 10.3389/fcell.2021.646575.].

Intracellular molecules are transported by motor proteins or move by diffusion resulting from random molecular motion. Cardiomyocytes are packed with structures that are crucial for function, but also confine the diffusional spaces, providing cells with a means to control diffusion. They form compartments in which local concentrations are different from the overall, average concentrations. For example, calcium and cyclic AMP are highly compartmentalized, allowing these versatile second messengers to send different signals depending on their location. In energetic compartmentalization, the ratios of AMP and ADP to ATP are different from the average ratios. This is important for the performance of ATPases fuelling cardiac excitation-contraction coupling and mechanical work. A recent study suggested that compartmentalization modulates the activity of creatine kinase and adenylate kinase in situ. This could have implications for energetic signaling through, for example, AMP-activated kinase. It highlights the importance of taking compartmentalization into account in our interpretation of cellular physiology and developing methods to assess local concentrations of AMP and ADP to enhance our understanding of compartmentalization in different cell types.

While classical molecular biology assays can provide a measure of cellular response to chemical challenges, they rely on a single biological phenomenon to infer a broader measure of cellular metabolic response. These methods do not always afford the necessary sensitivity to answer questions of sub-cytotoxic effects, nor do they work for all cell types. Likewise, boutique assays such as cardiomyocyte beat rate may indirectly measure cellular metabolic response, but they too, are limited to measuring a specific biological phenomenon and are often limited to a single cell type. For these reasons, toxicological researchers need new approaches to determine metabolic changes across various doses in differing cell types, especially within the low-dose regime. The data collected herein demonstrate that LC-MS/MS-based untargeted metabolomics with a feature-agnostic view of the data, combined with a suite of statistical methods including an adapted environmental threshold analysis, provides a versatile, robust, and holistic approach to directly monitoring the overall cellular metabolomic response to pesticides. When employing this method in investigating two different cell types, human cardiomyocytes and neurons, this approach revealed separate sub-cytotoxic metabolomic responses at doses of 0.1 µM and 1 µM of chlorpyrifos and carbaryl. These findings suggest that this agnostic approach to untargeted metabolomics can provide a new tool for determining effective dose by metabolomics (EDm) of chemical challenges, such as pesticides, in a direct measurement of metabolomic response that is not cell type-specific or observable using traditional assays.

Cardiomyocytes (CMs) derived from human-induced pluripotent stem cells (hiPSCs) are considered a promising platform for multiple applications, including disease modeling, regenerative medicine, screening of drug toxicity and investigation of cardiomyogenesis. Despite remarkable improvement in methodology enabling differentiation of hiPSCs into CMs, applied protocols generate heterogeneous cell populations composed of CMs along with differentiated non-cardiac cell-types and undifferentiated hiPSCs. Here we describea procedure of automated Magnetic-Activated Cell Sorting (autoMACS) for the purification of hiPSCs-derived CMs under sterile culture conditions. We illustrate that this approach led to a robust depletion of non-cardiac cells and enrichment of CMs, a result particularly crucial for hiPSC lines with poor cardiac differentiation efficiencies.

Cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) offer an attractive platform to evaluate the mechanisms of cardiovascular-related incidents and to develop and test new drugs for heart diseases. This work focuses on the comparison of two hiPSC-CM differentiation protocols: the GiWi method based on temporal modulation of the Wnt/β-catenin pathway and the commercially available PSC Cardiomyocyte Differentiation Kit. We underlined the need to optimize several parameters such as cell density or small molecule concentration (CHIR-99021, IWR-1) to obtain functional hiPSC-CMs. Both protocols yield a similar differentiation efficiency; therefore, the choice of a particular procedure may depend on the preferences of the experimenter.

BACKGROUND: COVID-19 can cause cardiac complications and the latter are associated with poor prognosis and increased mortality. SARS-CoV-2 variants differ in their infectivity and pathogenicity, but how they affect cardiomyocytes (CMs) is unclear.
METHODS: The effects of SARS-CoV-2 variants were investigated using human induced pluripotent stem cell-derived (hiPSC-) CMs in vitro and Golden Syrian hamsters in vivo.
RESULTS: Different variants exhibited distinct tropism, mechanism of viral entry and pathology in the heart. Omicron BA.2 most efficiently infected and injured CMs in vitro and in vivo, and induced expression changes consistent with increased cardiac dysfunction, compared to other variants tested. Bioinformatics and upstream regulator analyses identified transcription factors and network predicted to control the unique transcriptome of Omicron BA.2 infected CMs. Increased infectivity of Omicron BA.2 is attributed to its ability to infect via endocytosis, independently of TMPRSS2, which is absent in CMs.
CONCLUSIONS: In this study, we reveal previously unknown differences in how different SARS-CoV-2 variants affect CMs. Omicron BA.2, which is generally thought to cause mild disease, can damage CMs in vitro and in vivo. Our study highlights the need for further investigations to define the pathogenesis of cardiac complications arising from different SARS-CoV-2 variants.

暂无摘要。

Cardiotoxicity can be defined as \"chemically induced heart disease\", which can occur with many different drug classes treating a range of diseases. It is the primary cause of drug attrition during pre-clinical development and withdrawal from the market. Drug induced cardiovascular toxicity can result from both functional effects with alteration of the contractile and electrical regulation in the heart and structural changes with morphological changes to cardiomyocytes and other cardiac cells. These adverse effects result in conditions such as arrhythmia or a more serious reduction in left ventricular ejection fraction (LVEF), which can lead to heart failure and death. Anticancer drugs can adversely affect cardiomyocyte function as well as cardiac fibroblasts and cardiac endothelial cells, interfering in autocrine and paracrine signalling between these cell types and ultimately altering cardiac cellular homeostasis. This review aims to highlight potential toxicity mechanisms involving cardiomyocytes and non-cardiomyocyte cells by first introducing the physiological roles of these cells within the myocardium and secondly, identifying the physiological pathways perturbed by anticancer drugs in these cells.