The biochemical and electrophysiological profiles of amniotic fluid-derived stem cells following Wnt signaling modulation cardiac differentiation

Investigating the influence of XAV-939, a tankyrase inhibitor, on the density and gating of erg-mediated K+ currents in mouse MA-10 Leydig tumor cells

XAV-939(XAV) is a chemical compound that inhibits the activity of tankyrase. However, the precise way in which XAV alters membrane ionic currents is not well understood. In this study,our goal was to examine the impact of XAV on the ionic currents in mouse MA-10 Leydig cells, specifically focusing on the magnitude, gating properties,and voltage-dependent hysteresis of erg-mediated K+currents(IK(erg)). In our whole-cell current recordings we observed that the addition of XAV inhibited the density of IK(erg) in a concentration-dependent manner with an IC50 of 3.1 μM. Furthermore we found that continued exposure to XAV, further addition of neither liraglutide nor insulin-like growth factor-1 counteracted XAV-mediated inhibition of IK(erg). Additionally the presence of XAV suppressed the mean current versus voltage relationship of IK(erg) across the entire voltage-clamp step analyzed. This compound shifted the steady-state activation curve of IK(erg) to a less negative potential by approximately 12 mV. The presence of XAV increased the time constant of deactivating IK(erg) in MA-10 cells. The voltage-dependent clockwise hysteresis of IK(erg) responding to prolonged upright isosceles-triangular ramp voltage became diminished by adding XAV; moreover subsequent addition of NS3623 effectively reversed XAV-induced decrease of hysteretic area of IK(erg). XAV also inhibited the proliferation of this cell line and the IC50 value of XAV-induced inhibition of cell proliferation was 2.8M. Overall the suppression of IK(erg) by XAV may serve as a significant ionic mechanism that contribute to the functional properties of MA-10 cells. However, it is important to note that this effect cannot be attributed solely to the inhibition of tankyrase.

Exploring the Impact of BKCa Channel Function in Cellular Membranes on Cardiac Electrical Activity

This review paper delves into the current body of evidence, offering a thorough analysis of the impact of large-conductance Ca2+-activated K+ (BKCa or BK) channels on the electrical dynamics of the heart. Alterations in the activity of BKCa channels, responsible for the generation of the overall magnitude of Ca2+-activated K+ current at the whole-cell level, occur through allosteric mechanisms. The collaborative interplay between membrane depolarization and heightened intracellular Ca2+ ion concentrations collectively contribute to the activation of BKCa channels. Although fully developed mammalian cardiac cells do not exhibit functional expression of these ion channels, evidence suggests their presence in cardiac fibroblasts that surround and potentially establish close connections with neighboring cardiac cells. When cardiac cells form close associations with fibroblasts, the high single-ion conductance of these channels, approximately ranging from 150 to 250 pS, can result in the random depolarization of the adjacent cardiac cell membranes. While cardiac fibroblasts are typically electrically non-excitable, their prevalence within heart tissue increases, particularly in the context of aging myocardial infarction or atrial fibrillation. This augmented presence of BKCa channels' conductance holds the potential to amplify the excitability of cardiac cell membranes through effective electrical coupling between fibroblasts and cardiomyocytes. In this scenario, this heightened excitability may contribute to the onset of cardiac arrhythmias. Moreover, it is worth noting that the substances influencing the activity of these BKCa channels might influence cardiac electrical activity as well. Taken together, the BKCa channel activity residing in cardiac fibroblasts may contribute to cardiac electrical function occurring in vivo.

HLA-Ehigh /HLA-Ghigh /HLA-IIlow Human iPSC-Derived Cardiomyocytes Exhibit Low Immunogenicity for Heart Regeneration

Although human pluripotent stem cells (hPSCs)-derived cardiomyocytes (hPSC-CMs) can remuscularize infarcted hearts and restore post-infarct cardiac function, post-transplant rejection resulting from human leukocyte antigen (HLA) mismatching is an enormous obstacle. It is crucial to identify hypoimmunogenic hPSCs for allogeneic cell therapy. This study is conducted to demonstrate the immune privilege of HLA-Ehigh /HLA-Ghigh /HLA-IIlow human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs). Ischemia-reperfusion surgery is done to create transmural myocardial infarction in rats. At post-infarct 4 days, hPSC-CMs (1.0×107 cells per kg), including human embryonic stem cell-derived cardiomyocytes (hESC-CMs), HLA-Elow/HLA-Glow/HLA-IIhigh hiPSC-CMs, and HLA-Ehigh /HLA-Ghigh /HLA-IIlow hiPSC-CMs, are injected into the infarcted myocardium. Under the treatment of very low dose cyclosporine A (CsA), only HLA-Ehigh /HLA-Ghigh /HLA-IIlow hiPSC-CMs survive in vivo and improved post-infarct cardiac function with infarct size reduction. HLA-Ehigh /HLA-Ghigh /HLA-IIlow hiPSC-CMs activate the SHP-1 signaling pathway of natural killer (NK) cells and cytotoxic T cells to evade attack by NK cells and cytotoxic T cells. Herein, it is demonstrated that using a clinically relevant CsA dose, HLA-Ehigh /HLA-Ghigh /HLA-IIlow hiPSC-CMs repair the infarcted myocardium and restore the post-infarct heart function. HLA-Ehigh /HLA-Ghigh /HLA-IIlow hiPSCs are less immunogenic and may serve as platforms for regeneration medicine.

Spontaneous Ca2+ events are linked to the development of neuronal firing during maturation in mice primary hippocampal culture cells

Calcium is one of the most vital intracellular secondary messengers that tightly regulates a variety of cell physiology processes, especially in the brain. Using a fluorescent Ca²⁺-sensitive Oregon Green probe, we revealed three different amplitude distributions of spontaneous Ca²⁺ events (SCEs) in neurons between 15 and 26 days in vitro (DIV) culture maturation. We detected a series of amplitude events: micro amplitude SCE (microSCE) 25% increase from the baseline, intermediate amplitude SCE (interSCE) as 25-75%, and macro amplitude SCE (macroSCE) - over 75%. The SCEs were fully dependent on extracellular Ca²⁺ and neuronal network activity and vanished in the Ca²⁺-free solution, 10 mM Mg²⁺-block, or in the presence of voltage-gated Na⁺-channel blocker, tetrodotoxin. Combined patch-clamp and Ca²⁺-imaging techniques revealed that microSCE match single action potential (AP), interSCE - burst of 3-12 APs, and macroSCE - 'superburst' of 10+ APs. MicroSCEs were blocked by a common α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid (KA) receptor antagonist, CNQX. The γ-aminobutyric acid (GABA) A-type receptor (GABAAR) picrotoxin blockade and L-type voltage-dependent Ca²⁺-channel inhibitor diltiazem significantly reduced microSCE frequency. InterSCEs were inhibited by CNQX, but picrotoxin treatment significantly increased its amplitude. The N-methyl-d-aspartate (NMDA) receptor antagonist, D-APV, voltage-gated K⁺-channel blocker, tetraethylammonium, noticeably suppressed interSCE amplitude. We also demonstrate that macroSCEs were AMPA/KA receptor-independent.

Progress and Challenges of Amniotic Fluid Derived Stem Cells in Therapy of Ischemic Heart Disease

Cardiovascular disease is the leading cause of deaths worldwide, claiming an estimated total of 17.9 million lives each year, of which one-third of the people are under the age of 70 years. Since adult cardiomyocytes fail to regenerate, the heart loses the ability to repair itself after an injury, making patients with heart disease suffer from poor prognosis. Pluripotent stem cells have the ability to differentiate into cardiomyocytes in vitro through a well-established process, which is a new advancement in cardiac regeneration therapy. However, pluripotent stem cell-derived cardiomyocytes have certain drawbacks, such as the risk of arrhythmia and immune incompatibility. Thus, amniotic fluid stem cells (AFSCs), a relatively novel source of stem cells, have been exploited for their ability of pluripotent differentiation. In addition, since AFSCs are weakly positive for the major histocompatibility class II molecules, they may have high immune tolerance. In summary, the possibility of development of cardiomyocytes from AFSCs, as well as their transplantation in host cells to produce mechanical contraction, has been discussed. Thus, this review article highlights the progress of AFSC therapy and its application in the treatment of heart diseases in recent years.

Efficient Cardiac Differentiation of Human Amniotic Fluid-Derived Stem Cells into Induced Pluripotent Stem Cells and Their Potential Immune Privilege

Mature mammalian hearts possess very limited regenerative potential. The irreversible cardiomyocyte loss after heart injury can lead to heart failure and death. Pluripotent stem cells (PSCs) can differentiate into cardiomyocytes for cardiac repair, but there are obstacles to their clinical application. Among these obstacles is their potential for post-transplant rejection. Although human amniotic fluid-derived stem cells (hAFSCs) are immune privileged, they cannot induce cardiac differentiation. Thus, we generated hAFSC-derived induced PSCs (hAFSC-iPSCs) and used a Wnt-modulating differentiation protocol for the cardiac differentiation of hAFSC-iPSCs. In vitro studies using flow cytometry, immunofluorescence staining, and patch-clamp electrophysiological study, were performed to identify the characteristics of hAFSC-iPSC-derived cardiomyocytes (hAFSC-iPSC-CMs). We injected hAFSC-iPSC-CMs intramuscularly into rat infarcted hearts to evaluate the therapeutic potential of hAFSC-iPSC-CM transplantation. At day 21 of differentiation, the hAFSC-iPSC-CMs expressed cardiac-specific marker (cardiac troponin T), presented cardiomyocyte-specific electrophysiological properties, and contracted spontaneously. Importantly, these hAFSC-iPSC-CMs demonstrated low major histocompatibility complex (MHC) class I antigen expression and the absence of MHC class II antigens, indicating their low immunogenicity. The intramyocardial transplantation of hAFSC-iPSC-CMs restored cardiac function, partially remuscularized the injured region, and reduced fibrosis in the rat infarcted hearts. Therefore, hAFSC-iPSCs are potential candidates for the repair of infarcted myocardium.

High Efficacy by GAL-021: A Known Intravenous Peripheral Chemoreceptor Modulator that Suppresses BKCa-Channel Activity and Inhibits IK(M) or Ih

GAL-021 has recently been developed as a novel breathing control modulator. However, modifications of ionic currents produced by this agent remain uncertain, although its efficacy in suppressing the activity of big-conductance Ca²⁺-activated K⁺ (BK_Ca) channels has been reported. In pituitary tumor (GH₃) cells, we found that the presence of GAL-021 decreased the amplitude of macroscopic Ca²⁺-activated K⁺ current (I_K(Ca)) in a concentration-dependent manner with an effective IC₅₀ of 2.33 μM. GAL-021-mediated reduction of I_K(Ca) was reversed by subsequent application of verteporfin or ionomycin; however, it was not by that of diazoxide. In inside-out current recordings, the addition of GAL-021 to the bath markedly decreased the open-state probability of BK_Ca channels. This agent also resulted in a rightward shift in voltage dependence of the activation curve of BK_Ca channels; however, neither the gating charge of the curve nor single-channel conductance of the channel was changed. There was an evident lengthening of the mean closed time of BK_Ca channels in the presence of GAL-021, with no change in mean open time. The GAL-021 addition also suppressed M-type K⁺ current with an effective IC₅₀ of 3.75 μM; however, its presence did not alter the amplitude of erg-mediated K⁺ current, or mildly suppressed delayed-rectifier K⁺ current. GAL-021 at a concentration of 30 μM could also suppress hyperpolarization-activated cationic current. In HEK293T cells expressing α-hSlo, the addition of GAL-021 was also able to suppress the BK_Ca-channel open probabilities, and GAL-021-mediated suppression of BK_Ca-channel activity was attenuated by further addition of BMS-191011. Collectively, the GAL-021 effects presented herein do not exclusively act on BK_Ca channels and these modifications on ionic currents exert significant influence on the functional activities of electrically excitable cells occurring in vivo.

Characterization of Perturbing Actions by Verteporfin, a Benzoporphyrin Photosensitizer, on Membrane Ionic Currents

Verteporfin (VP), a benzoporphyrin derivative, has been clinically tailored as a photosensitizer and recently known to suppress YAP-TEAD complex accompanied by suppression of the growth in an array of neoplastic cells. However, the detailed information is little available regarding possible modifications of it and its related compounds on transmembrane ionic currents, despite its growing use in clinical settings. In this study, from whole cell recordings, VP (0.3-100 μM) increased the amplitude of Ca²⁺-activated K⁺ currents (I _K(Ca)) in pituitary tumor (GH₃) cells in a concentration-dependent manner with an EC₅₀ value of 2.4 μM. VP-stimulated I _K(Ca) in these cells was suppressed by further addition of either paxilline, iberiotoxin, or dithiothreitol, but not by that of tobultamide or TRAM-39. VP at a concentration of 10 μM mildly suppressed the amplitude of delayed-rectifier K⁺ current; however, it had minimal effects on M-type K⁺ current. In cell-attached current recordings, addition of VP to the recording medium enhanced the activity of large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels. In the presence of VP, additional illumination with light intensity of 5.5 mW/cm² raised the probability of BK_Ca-channel openings further. Addition of VP decreased the peak amplitude of L-type Ca²⁺ current together with slowed inactivation time course of the current; however, it failed to modify voltage-gated Na⁺ current. Illumination of GH₃ cells in continued presence of VP also induced a non-selective cation current. Additionally, VP increased the activity of BK_Ca channels in human 13-06-MG glioma cells with an EC₅₀ value of 1.9 μM. Therefore, the effects of VP on ionic currents described herein tend to be upstream of its inhibition of YAP-TEAD complex and they are conceivably likely to contribute to the underlying mechanisms through which it and its structurally similar compounds effect the modifications in functional activities of pituitary or glial neoplastic cells, if the in vivo findings occur.