Cell Electrophysiology Research Articles

Berberine ameliorates inflammation by inhibiting MrgprB2 receptor-mediated activation of mast cell in mice

BackgroundBerberine, an isoquinoline alkaloid, is known for anti-inflammatory activities. However, the research on the anti-inflammatory mechanism of berberine is not comprehensive. Recently, studies have shown that MrgprB2 (Mas-related G-protein-coupled receptor B2) in mice and MrgprX2 (Mas-related G-protein-coupled receptor X2) in humans play vital roles in inflammation. Therefore, this study aims to investigate whether the anti-inflammatory activity of berberine is related to MrgprB2 receptor. MethodsThe anti-inflammatory activity of BH (berberine hydrochloride) was evaluated by hindpaw edema analysis, pathological analysis and RT-qPCR. Transgenic mice (MrgprB2−/− mice), HEK293T cell transfection, calcium imaging, electrophysiology, molecular docking and other methods were employed to investigate the potential relationship between the anti-inflammatory activity of BH and the MrgprB2 receptor. ResultsThe results demonstrated that BH significantly alleviated C48/80 (compound 48/80)-induced local inflammation in vivo. This was evidenced by a decrease in paw edema, reduced infiltration of inflammatory cells, inhibition of mast cell activation, and down-regulation of inflammatory factors such as CXCL13 (CXC subfamily 13) and TNF-α (tumor necrosis factor-α). It was also found that knockout of MrgprB2 receptor could block the anti-inflammatory activity of BH in mice. Furthermore, calcium imaging revealed that BH effectively inhibited the activity of MrgprB2 receptor in overexpressed HEK293T cells in vitro. Additionally, it was observed that BH also inhibited MrgprB2-mediated voltage-dependent current changes in mouse peritoneal mast cells. Molecular docking results further indicated that BH had affinity with MrgprX2 protein. ConclusionsThe anti-inflammatory mechanism of BH may be partially attributed to the inhibition of MrgprB2 receptor-mediated mast cell activation.

Indoxyl sulfate deteriorates cardiac electrophysiological function and increases the likelihood of arrhythmias in human ventricular myocardial cells

Abstract Background Approximately 10% of the world population is suffering from chronic kidney disease (CKD). In these patients, an increased mortality and morbidity, predominantly derived from cardiovascular diseases, can be observed. Purpose The impact of CKD on myocardial cell mechanisms is only partially understood. This study aims to investigate the impact of the uremic toxin indoxyl sulfate (IS) on human ventricular myocardial cells. Methods Human left ventricular myocardium was obtained from patients with severe aortic stenosis who underwent surgical valve replacement. In addition, human ventricular induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) obtained from donors without any known cardiovascular disease were used. Before measurements were conducted, isolated single primary human cardiomyocytes were incubated for 15 minutes with an IS concentration of 120 mg/l (highest measured IS-level in dialysis patients). Further, iPSC-CM were incubated for one week with IS 45 mg/l and IS 120 mg/l, with IS 45 mg/l representing the average dialysis patients IS-level. Epifluorescence and confocal microscopy were performed to investigate Ca2+hemostasis and patch clamp measurements assessed cardiac action potentials and the occurrence of arrythmias. Results Experiments were conducted using human ventricular myocardium from 10 patients with a mean left ventricular ejection fraction of 51.5±12% and a mean glomerular filtration rate of 66.3±22.7 ml/min. Compared to the control group, higher systolic Ca2+ transient amplitudes were observed after acute incubation with IS 120 mg/l in single primary human cardiomyocytes. Measurements after 7 days of IS incubation (IS 45 mg/l and 120 mg/l) in iPSC-CM confirmed these previous results by showing higher Ca2+ transient amplitudes (Figure 1). Additionally, cells showed a diminished diastolic Ca2+ level compared to controls. An increased Ca2+ spark frequency in IS-treated iPSC-CM versus the control group was unveiled by confocal microscopy measurements. While an increased number of delayed afterdepolarizations could be observed, IS seemed to have no effect on cardiac action potential duration in iPSC-CM. Conclusion For the first time, we could reveal the impact of IS on cellular electrophysiology of primary human myocardium cells and iPSC-CM and identify IS as a proarrhythmogenic trigger. Therefore, IS may be of relevance in explaining the high cardiovascular mortality in end-stage CKD patients. To improve the outcome of these patients, new therapeutic approaches will be necessary since IS, a protein-bound uremic toxin, is only insufficiently removed by dialysis.

Low conduction velocity is a key factor for localisation of reentrant drivers for atrial fibrillation

Abstract Background Atrial Fibrillation (AF) is a prevalent cardiac arrhythmia globally, associated with heightened risks of stroke, dementia, and heart failure. Catheter ablation, the sole curative therapy for AF, yields suboptimal success rates for persistent AF cases. Understanding the mechanisms and dynamics of AF remains challenging, hindering treatment advancements. Novel ablation strategies aimed at targeting substrates harbouring AF reentrant drivers (RD), such as low-voltage ablation and rotor-based ablation, have yet to demonstrate superiority over the gold standard ablation strategy – pulmonary vein isolation. Purpose The purpose of the study is to integrate in-silico 3D left atrial (LA) simulations and explainable artificial intelligence (AI) to pinpoint key factors for RD localisation in persistent AF, aiming to improve the mechanistic understanding of AF and help develop a more effective ablation strategy. Methods 3D LA models were derived from magnetic resonance images of 41 patients and combined with atrial cell electrophysiology models. Persistent AF was initiated in each patient-specific LA model with fast pacing, and five functional features (action potential duration (APD), conduction velocity (CV), wavelength, APD spatial gradient, CV spatial gradient, and wavelength spatial gradient) and three structural features (fibrotic density, fibrotic entropy, and image intensity ratio) were evaluated. A random forest AI model was trained to classify phase singularities corresponding to the RDs (PS-RD) in five distinct tissue classes (total LA tissue, healthy tissue, fibrotic border zone, dense fibrotic tissue, and PS-RD tissue) based on the functional and structural features. Shapley additive explanations (SHAP) analysis was then used to find the most influential feature in the AI model’s decision process. Results Simulations of the patient-specific LA models revealed that RDs were typically localised in regions with the lowest atrial CV, which often coincided with patches of dense fibrotic tissue. In a five-fold cross-validation, the random forest AI model achieved high accuracy in classifying PS-RD regions: a mean ROC AUC of 0.99 ± 0.010, a mean F1 score of 0.86 ± 0.034, a mean recall of 0.95 ± 0.058, and a mean precision score of 0.79 ± 0.085. The further SHAP analysis revealed that low CV was the key determinant in classifying the PS-RD regions. Conclusion Our study combined AF computational modelling and explainable AI to identify the key factors in RD localisation. Both the computational and AI models concluded that low CV was the most important determinant in localising RDs. These findings provide mechanistic evidence for the efficacy of ablation strategies that target low CV atrial areas for persistent AF patients.

Invasive neurophysiological recordings in human basal ganglia. What have we learned about non-motor behaviour?

Research into the function of deep brain structures has benefited greatly from microelectrode recordings in animals. This has helped to unravel physiological processes in the healthy and malfunctioning brain. Translation to the human is necessary for improving basic understanding of subcortical structures and their implications in diseases. The use of microelectrode recordings as a standard component of deep brain stimulation surgery offers the most viable route for studying the electrophysiology of single cells and local neuronal populations in important deep structures of the human brain. Most of the studies in the basal ganglia have targeted the motor loop and movement disorder pathophysiology. In recent years, however, research has diversified to include limbic and cognitive processes. This review aims to provide an overview of advances in neuroscience made using intraoperative and post-operative recordings with a focus on non-motor activity in the basal ganglia.

Evolution of Bioelectric Membrane Potentials: Implications in Cancer Pathogenesis and Therapeutic Strategies.

Electrophysiology typically deals with the electrical properties of excitable cells like neurons and muscles. However, all other cells (non-excitable) also possess bioelectric membrane potentials for intracellular and extracellular communications. These membrane potentials are generated by different ions present in fluids available in and outside the cell, playing a vital role in communication and coordination between the cell and its organelles. Bioelectric membrane potential variations disturb cellular ionic homeostasis and are characteristic of many diseases, including cancers. A rapidly increasing interest has emerged in sorting out the electrophysiology of cancer cells. Compared to healthy cells, the distinct electrical properties exhibited by cancer cells offer a unique way of understanding cancer development, migration, and progression. Decoding the altered bioelectric signals influenced by fluctuating electric fields benefits understanding cancer more closely. While cancer research has predominantly focussed on genetic and molecular traits, the delicate area of electrophysiological characteristics has increasingly gained prominence. This review explores the historical exploration of electrophysiology in the context of cancer cells, shedding light on how alterations in bioelectric membrane potentials, mediated by ion channels and gap junctions, contribute to the pathophysiology of cancer.

Telomerase Reverse Transcriptase Regulates Intracellular Ca2+ Homeostasis and Mitochondrial Function via the p53/PGC-1α Pathway in HL-1 Cells.

Telomere shortening is strongly associated with cardiovascular aging and disease, and patients with shorter telomeres in peripheral blood leukocytes are at higher risk of cardiovascular diseases such as heart failure and atrial fibrillation (AF). Telomerase reverse transcriptase (TERT) maintains telomere length, and overexpression of TERT has been shown to reduce cardiomyocyte apoptosis and myocardial infarct size, and extend the lifespan of aged mice. However, the specific impact of TERT on the electrophysiology of cardiomyocytes remains to be elucidated. The aims of this study were to evaluate the role of TERT in Ca2+ homeostasis and mitochondrial function in atrial myocytes as well as the underlying mechanisms. TERT overexpressed and silenced HL-1 cells were constructed with lentiviruses, and the respective empty lentiviral vectors were used as negative controls. Then the patch clamp technique was used to record the electrophysiological characteristics such as cell action potential duration (APD) and L-type Ca2+ currents (ICa,L), flow cytometry was used to detect intracellular Ca2+ concentration and mitochondrial membrane potential (MMP), and the Seahorse assay was used to measure the oxygen consumption rate (OCR). TERT silencing led to intracellular Ca2+ overload, shortened APD, decreased ICa,L current density, altered Ca2+ gating mechanism, decreased MMP and OCR, and increased reactive oxygen species (ROS), whereas TERT overexpression led to the reverse effects. Additionally, TERT silencing resulted in intracellular Ca2+ overload with decreased expression of the SERCA2a, CaV1.2, and NCX1.1, whereas TERT overexpression had opposing effects. Furthermore, we discovered that TERT could regulate the expression of p53 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). The expression of PGC-1α was downregulated by the p53 agonist Tenovin-6 but upregulated by the p53 inhibitor PFTα. The effects of the PGC-1α inhibitor SR-18292 on intracellular Ca2+ and cell electrophysiology were similar to those of silencing TERT, whereas the PGC-1α agonist ZLN005 produced comparable outcomes to TERT overexpression. TERT silencing-induced Ca2+ overload and mitochondrial dysfunction may be one mechanism of age-related AF. Overexpression of TERT reduced the basis for arrhythmia formation such as AF, suggesting a favorable safety profile for TERT therapy. TERT regulated intracellular Ca2+ homeostasis and mitochondrial function through the p53/PGC-1α pathway. In addition, PGC-1α might be a novel target for AF, suggesting that intervention for AF should be not limited to abnormal cation handling.

Presynaptic hyperexcitability reversed by positive allosteric modulation of a GABABR epilepsy variant.

GABABRs are key membrane proteins that continually adapt the excitability of the nervous system. These G-protein coupled receptors are activated by the brain's premier inhibitory neurotransmitter GABA. They are obligate heterodimers composed of GABA-binding GABABR1 and G-protein-coupling GABABR2 subunits. Recently, three variants (G693W, S695I, I705N) have been identified in the gene (GABBR2) encoding for GABABR2. Individuals that harbour any of these variants exhibit severe developmental epileptic encephalopathy and intellectual disability, but the underlying pathogenesis that is triggered in neurons, remains unresolved. Using a range of confocal imaging, flow cytometry, structural modelling, biochemistry, live cell Ca2+ imaging of presynaptic terminals, whole-cell electrophysiology of HEK-293T cells and neurons, and two-electrode voltage clamping of Xenopus oocytes we have probed the biophysical and molecular trafficking and functional profiles of G693W, S695I and I705N variants. We report that all three point mutations impair neuronal cell surface expression of GABABRs, reducing signalling efficacy. However, a negative effect evident for one variant perturbed neurotransmission by elevating presynaptic Ca2+ signalling. This is reversed by enhancing GABABR signalling via positive allosteric modulation. Our results highlight the importance of studying neuronal receptors expressed in nervous system tissue and provide new mechanistic insights into how GABABR variants can initiate neurodevelopmental disease whilst highlighting the translational suitability and therapeutic potential of allosteric modulation for correcting these deficits.

Electrophysiology and Morphology of Human Cortical Supragranular Pyramidal Cells in a Wide Age Range.

The basic excitatory neurons of the cerebral cortex, the pyramidal cells, are the most important signal integrators for the local circuit. They have quite characteristic morphological and electrophysiological properties that are known to be largely constant with age in the young and adult cortex. However, the brain undergoes several dynamic changes throughout life, such as in the phases of early development and cognitive decline in the aging brain. We set out to search for intrinsic cellular changes in supragranular pyramidal cells across a broad age range: from birth to 85 years of age and we found differences in several biophysical properties between defined age groups. During the first year of life, subthreshold and suprathreshold electrophysiological properties changed in a way that shows that pyramidal cells become less excitable with maturation, but also become temporarily more precise. According to our findings, the morphological features of the three-dimensional reconstructions from different life stages showed consistent morphological properties and systematic dendritic spine analysis of an infantile and an old pyramidal cell showed clear significant differences in the distribution of spine shapes. Overall, the changes that occur during development and aging may have lasting effects on the properties of pyramidal cells in the cerebral cortex. Understanding these changes is important to unravel the complex mechanisms underlying brain development, cognition and age-related neurodegenerative diseases.

Electrophysiology of Human iPSC-derived Vascular Smooth Muscle Cells and Cell-autonomous Consequences of Cantú Syndrome Mutations.

Cantú syndrome (CS), a multisystem disease with a complex cardiovascular phenotype, is caused by gain-of-function (GoF) variants in the Kir6.1/SUR2 subunits of ATP-sensitive potassium (KATP) channels and is characterized by low systemic vascular resistance, as well as tortuous, dilated, vessels, and decreased pulse-wave velocity. Thus, CS vascular dysfunction is multifactorial, with both hypomyotonic and hyperelastic components. To dissect whether such complexities arise cell autonomously within vascular smooth muscle cells (VSMCs) or as secondary responses to the pathophysiological milieu, we assessed electrical properties and gene expression in human induced pluripotent stem cell-derived VSMCs (hiPSC-VSMCs), differentiated from control and CS patient-derived hiPSCs, and in native mouse control and CS VSMCs. Whole-cell voltage clamp of isolated aortic and mesenteric arterial VSMCs isolated from wild-type (WT) and Kir6.1[V65M] (CS) mice revealed no clear differences in voltage-gated K+ (Kv) or Ca2+ currents. Kv and Ca2+ currents were also not different between validated hiPSC-VSMCs differentiated from control and CS patient-derived hiPSCs. While pinacidil-sensitive KATP currents in control hiPSC-VSMCs were similar to those in WT mouse VSMCs, they were considerably larger in CS hiPSC-VSMCs. Under current-clamp conditions, CS hiPSC-VSMCs were also hyperpolarized, consistent with increased basal K conductance and providing an explanation for decreased tone and decreased vascular resistance in CS. Increased compliance was observed in isolated CS mouse aortae and was associated with increased elastin mRNA expression. This was consistent with higher levels of elastin mRNA in CS hiPSC-VSMCs and suggesting that the hyperelastic component of CS vasculopathy is a cell-autonomous consequence of vascular KATP GoF. The results show that hiPSC-VSMCs reiterate expression of the same major ion currents as primary VSMCs, validating the use of these cells to study vascular disease. Results in hiPSC-VSMCs derived from CS patient cells suggest that both the hypomyotonic and hyperelastic components of CS vasculopathy are cell-autonomous phenomena driven by KATP overactivity within VSMCs .

TBX3 transfection and nodal signal pathway inhibition promote differentiation of adipose mesenchymal stem cell to cardiac pacemaker-like cells.

Mesenchymal stem cells (MSCs) are known as one of the best candidate cells to produce cardiac pacemaker-like cells (CPLCs). Upregulation of TBX3 transcription factor and inhibition of the nodal signal pathway have a significant role in the formation of cardiac pacemaker cells such as sinoatrial and atrioventricular nodes, which initiate the heartbeat and control the rhythm of heart contractions. This study aimed to confirm the effects of transfection of TBX3 transcription factor and inhibition of the nodal signal pathway on differentiating adipose-derived MSCs (AD-MSCs) to CPLCs. AD-MSCs were characterized using flow cytometry and three-lineage differentiation staining. The transfection of TBX3 plasmid was carried out using lipofectamine, and inhibition of the nodal signal pathway was done using the small-molecule SB431542. The morphology of the cells was observed using a light microscope. Pacemaker-specific markers, including TBX3, Cx30, HCN4, HCN1, HCN3, and KCNN4, were evaluated using the qRT-PCR method. For protein level, TBX3 and Cx30 were evaluated using ELISA and immunofluorescence staining. The electrophysiology of cells was evaluated using a patch clamp. The TBX3 expression in the TBX3, SM, and TBX + SM groups significantly higher (p < 0.05) compared to the control group and cardiomyocytes. The expression of Cx40 and Cx43 genes were lower in TBX3, SM, TBX + SM groups. In contrast, Cx30 gene showed higher expression in TBX3 group. The expression HCN1, HCN3, and HCN4 genes are higher in TBX3 group. The transfection of TBX3 and inhibition of the nodal signal pathway by small-molecule SB431542 enhanced differentiation of AD-MSCs to CPLCs.

Conductive and Enhanced Mechanical Strength of Mo2Ti2C3 MXene-Based Hydrogel Promotes Neurogenesis and Bone Regeneration in Bone Defect Repair.

Bone defects are common with increasing high-energy fractures, tumor bone invasion, and implantation revision surgery. Bone is an electroactive tissue that has electromechanical interaction with collogen, osteoblasts, and osteoclasts. Hydrogel provides morphological plasticity and extracellular matrix (ECM) 3D structures for cell survival, and is widely used as a bone engineering material. However, the hydrogels have poor mechanical intensity and lack of cell adhesion, slow gelation time, and limited conductivity. MXenes are novel nanomaterials with hydrophilic groups that sense cell electrophysiology and improve hydrogel electric conductivity. Herein, gelatin had multiple active groups (NH2, OH, and COOH) and an accelerated gelation time. Acrylamide has Schiff base bonds to cross-link with gelatin and absorb metal ions. Deacetylated chitosan improved cell adhesion and active groups to connect MXene and acrylamide. We constructed Mo2Ti2C3 MXene hydrogel with improved elastic modulus and viscosity, chemical cross-linking structure, electric conductivity, and good compatibility. Mo2Ti2C3 MXene hydrogel exhibits outstanding osteogenesis in vitro. Mo2Ti2C3 MXene hydrogel promotes osteogenesis via alkaline phosphatase (ALP) and alizarin red S (ARS) staining, improving osteogenic marker genes and protein expressions in vitro. Mo2Ti2C3 MXene hydrogel aids new bone formation in the in vivo calvarial bone defect model via micro-CT and histology. Mo2Ti2C3 MXene hydrogel facilitates neurogenesis factors nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) expression, and aids newly born neuron marker Tuj-1 and sensory neuron marker serotonin (5-HT) and osteogenesis pathway proteins, runt-related transcription factor 2 (Runx2), osteocalcin (OCN), SMAD family member 4 (SMAD4), and bone morphogenetic protein-2 (BMP2) in the bone defect repair process. Mo2Ti2C3 MXene hydrogel promotes osteogenesis and neurogenesis, which extends its biomedical application in bone defect reconstruction.

Dielectric properties of human macrophages are altered by Mycobacterium tuberculosis infection.

The analysis of cell electrophysiology for pathogenic samples at BSL3 can be problematic. It is virtually impossible to isolate infected from uninfected without a label, for example green fluorescent protein, which can potentially alter the cell electrical properties. Furthermore, the measurement of highly pathogenic organismsoften requires equipment dedicated only for use with these organisms due to safety considerations. To address this, we have used dielectrophoresis to study the electrical properties of the human THP-1 cell line and monocyte-derived macrophages before and after infection with non-labelled Mycobacterium tuberculosis. Infection with these highly pathogenic bacilli resulted in changes including a raised surface conductance (associated with reduced zeta potential) and increased capacitance, suggesting an increase in surface roughness. We have also investigated the effect of fixation on THP-1 cells as a means to enable study on fixed samples in BSL1 or 2 laboratories, which suggests that the properties of these cells are largely unaffected by the fixation process. This advance results in a novel technique enabling the isolation of infected and non-infected cells in a sample without labelling.

Neurite Growth and Electrical Activity in PC-12 Cells: Effects of H3 Receptor-Inspired Electromagnetic Fields and Inherent Schumann Frequencies

Cells are continually exposed to a range of electromagnetic fields (EMFs), including those from the Schumann resonance to radio waves. The effects of EMFs on cells are diverse and vary based on the specific EMF type. Recent research suggests potential therapeutic applications of EMFs for various diseases. In this study, we explored the impact of a physiologically patterned EMF, inspired by the H3 receptor associated with wakefulness, on PC-12 cells in vitro. Our hypothesis posited that the application of this EMF to differentiated PC-12 cells could enhance firing patterns at specific frequencies. Cell electrophysiology was assessed using a novel device, allowing the computation of spectral power density (SPD) scores for frequencies between 1 Hz and 128 Hz. T-tests comparing SPD at certain frequencies (e.g., 29 Hz, 30 Hz, and 79 Hz) between the H3-EMF and control groups showed a significantly higher SPD in the H3 group (p &lt; 0.050). Moreover, at 7.8 Hz and 71 Hz, a significant correlation was observed between predicted and percentages of cells with neurites (R = 0.542). Key findings indicate the efficacy of the new electrophysiology measure for assessing PC-12 cell activity, a significant increase in cellular activity with the H3-receptor-inspired EMF at specific frequencies, and the influence of 7.8 Hz and 71 Hz frequencies on neurite growth. The overall findings support the idea that the electrical frequency profiles of developing cell systems can serve as an indicator of their progression and eventual cellular outcomes.

Enhanced Methodologies forInvestigating the Electrophysiological Characteristics of Endogenous Pannexin 1 Intercellular Cell-Cell Channels.

Gap junctions, pivotal intercellular conduits, serve as communication channels betweenadjacent cells, playing a critical role in modulating membrane potential distribution across cellular networks. The family ofPannexin (Panx) proteins, in particular Pannexin1 (Panx1), are widelyexpressed in vertebrate cells and exhibit sequence homology with innexins, the invertebrate gap junction channelconstituents. Despite being ubiquitously expressed, detailed functional and pharmacological properties ofPanx1 intercellular cell-cell channelsrequire further investigation. In this chapter, we introduce optimized cell culture methodologies and electrophysiology protocols to expedite the exploration of endogenous Panx1 cell-cell channels in TC620 cells, a human oligodendroglioma cell line that naturally expresses Panx1. We anticipate theserefined protocols will significantly contributeto future characterizations of Panx1-based intercellularcell-cell channelsacross diverse cell types andoffer valuable insights into both normalcellular physiology and pathophysiology.

Machine learning classification of cellular states based on the impedance features derived from microfluidic single-cell impedance flow cytometry.

Mitosis is a crucial biological process where a parental cell undergoes precisely controlled functional phases and divides into two daughter cells. Some drugs can inhibit cell mitosis, for instance, the anti-cancer drugs interacting with the tumor cell proliferation and leading to mitosis arrest at a specific phase or cell death eventually. Combining machine learning with microfluidic impedance flow cytometry (IFC) offers a concise way for label-free and high-throughput classification of drug-treated cells at single-cell level. IFC-based single-cell analysis generates a large amount of data related to the cell electrophysiology parameters, and machine learning helps establish correlations between these data and specific cell states. This work demonstrates the application of machine learning for cell state classification, including the binary differentiations between the G1/S and apoptosis states and between the G2/M and apoptosis states, as well as the classification of three subpopulations comprising a subgroup insensitive to the drug beyond the two drug-induced states of G2/M arrest and apoptosis. The impedance amplitudes and phases used as input features for the model training were extracted from the IFC-measured datasets for the drug-treated tumor cells. The deep neural network (DNN) model was exploited here with the structure (e.g., hidden layer number and neuron number in each layer) optimized for each given cell type and drug. For the H1650 cells, we obtained an accuracy of 78.51% for classification between the G1/S and apoptosis states and 82.55% for the G2/M and apoptosis states. For HeLa cells, we achieved a high accuracy of 96.94% for classification between the G2/M and apoptosis states, both of which were induced by taxol treatment. Even higher accuracy approaching 100% was achieved for the vinblastine-treated HeLa cells for the differentiation between the viable and non-viable states, and between the G2/M and apoptosis states. We also demonstrate the capability of the DNN model for high-accuracy classification of the three subpopulations in a complete cell sample treated by taxol or vinblastine.

ASCL1 induces neurogenesis in human Müller glia

In mammals, loss of retinal cells due to disease or trauma is an irreversible process that can lead to blindness. Interestingly, regeneration of retinal neurons is a well established process in some non-mammalian vertebrates and is driven by the Müller glia (MG), which are able to re-enter the cell cycle and reprogram into neurogenic progenitors upon retinal injury or disease. Progress has been made to restore this mechanism in mammals to promote retinal regeneration: MG can be stimulated to generate new neurons invivo in the adult mouse retina after the over-expression of the pro-neural transcription factor Ascl1. In this study, we applied the same strategy to reprogram human MG derived from fetal retina and retinal organoids into neurons. Combining single cell RNA sequencing, single cell ATAC sequencing, immunofluorescence, and electrophysiology we demonstrate that human MG can be reprogrammed into neurogenic cells invitro.

Numerical investigation of a graphene-on-semiconductor device for optical monitoring of cell electrophysiology

Spatially resolved sensing devices for electrostatic potentials are extremely useful for characterization of living cells, however, many current techniques lack the speed necessary to capture spatially resolved, functional information of cells in real-time. Here, an optical sensing technique is proposed based on graphene on a semiconductor stack operating in the near-infrared spectrum. By modeling coherent interference of multiply reflected beam paths within the semiconductor stack, we demonstrate how the device produces a continuous reflectivity change in response to graphene Fermi energy which is ideal for sensing changes in local electrostatic fields produced by action potentials of living cells. By coupling the device with a high-speed camera, we propose this platform will allow for high-speed imaging of action potentials over a large sensing area with micron scale resolution.

A non-coding SCN5A variant that reduces sodium channel function in hiPSC-derived cardiomyocytes is significantly enriched in Brugada syndrome patients from Thailand

Abstract Background/Introduction Brugada syndrome (BrS) is an inherited arrhythmia condition that can cause sudden cardiac death. Rare coding and common non-coding genetic variation in the Nav1.5 cardiac sodium channel-encoding SCN5A gene is robustly associated with BrS, but the role of rare and low frequency non-coding variants remains unexplored. BrS is several times more prevalent in Southeast Asia compared to other populations, indicating ancestry-specific genetic risk factors remain to be discovered. Purpose To identify and characterise novel genetic risk factors in BrS patients from Southeast Asia. Methods We performed genome sequencing in 231 BrS probands from Thailand and 500 population-matched controls to identify novel disease associated variants across the entire SCN5A locus. The candidate variant was engineered into human induced pluripotent stem cells (hiPSCs) by CRISPR-Cas9 and its effect was evaluated by single cell electrophysiology analysis on hiPSC-derived cardiomyocytes. Results We identified a rare (absent in gnomAD), non-coding variant in a regulatory element of the SCN5A gene (GRCh38:3-38580380-A-C) that was significantly enriched in cases (3.9%) vs controls (0.2%) (OR=20.2[2.5-160.6], p=2e-04). Transcription factor motif scanning analysis suggested the variant is likely to disrupt a Mef2 site that is conserved across species (Figure 1) – the MEF2 family of transcription factors play a critical role in cardiac transcriptional regulation. In hiPSC-derived cardiomyocytes, a significant reduction of peak Nav1.5-mediated sodium-current (INa) density (30% decrease at -20mV, p=8e-03), without changes in gating properties, was observed in cardiomyocytes carrying the variant in heterozygosity compared to isogenic controls (Figure 2). The variant also significantly reduced luciferase activity of the candidate regulatory element in HEK cells in the presence of cardiac transcription factors (Tbx5, Gata4, Mef2A, Mef2D). Conclusion A novel, non-coding variant in an SCN5A enhancer region is associated with BrS and was functionally validated using single cell electrophysiology in hiPSC-derived cardiomyocytes. This variant is found in ∼1 in every 25 BrS patients from Thailand and therefore may at least partially explain the increased prevalence of BrS in this region. Our study highlights the importance of research in understudied populations to understand the genetic aetiology of disease in diverse ancestries and to identify novel disease risk factors.

Sites and mechanisms of action of colokinetics at dopamine, ghrelin and serotonin receptors in the rodent lumbosacral defecation centre.

Agonists of dopamine D2 receptors (D2R), 5-hydroxytryptamine (5-HT, serotonin) receptors (5-HTR) and ghrelin receptors (GHSR) activate neurons in the lumbosacral defecation centre, and act as 'colokinetics', leading to increased propulsive colonic motility, in vivo. In the present study, we investigated which neurons in the lumbosacral defecation centre express the receptors and whether dopamine, serotonin and ghrelin receptor agonists act on the same lumbosacral preganglionic neurons (PGNs). We used whole cell electrophysiology to record responses from neurons in the lumbosacral defecation centre, following colokinetic application, and investigated their expression profiles and the chemistries of their neural inputs. Fluorescence in situ hybridisation revealed Drd2, Ghsr and Htr2C transcripts were colocalised in lumbosacral PGNs of mice, and immunohistochemistry showed that these neurons have closely associated tyrosine hydroxylase and 5-HT boutons. Previous studies showed that they do not receive ghrelin inputs. Whole cell electrophysiology in adult mice spinal cord revealed that dopamine, serotonin, α-methylserotonin and capromorelin each caused inward, excitatory currents in overlapping populations of lumbosacral PGNs. Furthermore, dopamine caused increased frequency of both IPSCs and EPSCs in a cohort of D2R neurons. Tetrodotoxin blocked the IPSCs and EPSCs, revealing a post-synaptic excitatory action of dopamine. In lumbosacral PGNs of postnatal day 7-14 rats, only dopamine's postsynaptic effects were observed. Furthermore, inward, excitatory currents evoked by dopamine were reduced by the GHSR antagonist, YIL781. We conclude that lumbosacral PGNs are the site where the action of endogenous ligands of D2R and 5-HT2R converge, and that GHSR act as a cis-modulator of D2R expressed by the same neurons. KEY POINTS: Dopamine, 5-hydroxytryptamine (5-HT, serotonin) and ghrelin (GHSR) receptor agonists increase colorectal motility and have been postulated to act at receptors on parasympathetic preganglionic neurons (PGNs) in the lumbosacral spinal cord. We aimed to determine which neurons in the lumbosacral spinal cord express dopamine, serotonin and GHSR receptors, their neural inputs, and whether agonists at these receptors excite them. We show that dopamine, serotonin and ghrelin receptor transcripts are contained in the same PGNs and that these neurons have closely associated tyrosine hydroxylase and serotonin boutons. Whole cell electrophysiology revealed that dopamine, serotonin and GHSR receptor agonists induce an inward excitatory current in overlapping populations of lumbosacral PGNs. Dopamine-induced excitation was reversed by GHSR antagonism. The present study demonstrates that lumbosacral PGNs are the site at which actions of endogenous ligands of dopamine D2 receptors and 5-HT type 2 receptors converge. Ghrelin receptors are functional, but their role appears to be as modulators of dopamine effects at D2 receptors.

Orange/far-red hybrid voltage indicators with reduced phototoxicity enable reliable long-term imaging in neurons and cardiomyocytes

Hybrid voltage indicators (HVIs) are chemogenetic sensors that combines the superior photophysical properties of organic dyes and the genetic targetability of protein sensors to report transient membrane voltage changes. They exhibit boosted sensitivity in excitable cells such as neurons and cardiomyocytes. However, the voltage signals recorded during long-term imaging are severely diminished or distorted due to phototoxicity and photobleaching issues. To capture stable electrophysiological activities over a long time, we employ cyanine dyes conjugated with a cyclooctatetraene (COT) molecule as the fluorescence reporter of HVI. The resulting orange-emitting HVI-COT-Cy3 enables high-fidelity voltage imaging for up to 30 min in cultured primary neurons with a sensitivity of ~ -30% ΔF/F0 per action potential (AP). It also maximally preserves the signal of individual APs in cardiomyocytes. The far-red-emitting HVI-COT-Cy5 allows two-color voltage/calcium imaging with GCaMP6s in neurons and cardiomyocytes for 15 min. We leverage the HVI-COT series with reduced phototoxicity and photobleaching to evaluate the impact of drug candidates on the electrophysiology of excitable cells.