Ilanit Itzhaki

Bio: Ilanit Itzhaki is an academic researcher from Technion – Israel Institute of Technology. The author has contributed to research in topics: Embryonic stem cell & Induced pluripotent stem cell. The author has an hindex of 10, co-authored 11 publications receiving 2367 citations.

Modelling the long QT syndrome with induced pluripotent stem cells

Abstract: The ability to generate patient-specific human induced pluripotent stem cells (iPSCs) offers a new paradigm for modelling human disease and for individualizing drug testing. Congenital long QT syndrome (LQTS) is a familial arrhythmogenic syndrome characterized by abnormal ion channel function and sudden cardiac death. Here we report the development of a patient/disease-specific human iPSC line from a patient with type-2 LQTS (which is due to the A614V missense mutation in the KCNH2 gene). The generated iPSCs were coaxed to differentiate into the cardiac lineage. Detailed whole-cell patch-clamp and extracellular multielectrode recordings revealed significant prolongation of the action-potential duration in LQTS human iPSC-derived cardiomyocytes (the characteristic LQTS phenotype) when compared to healthy control cells. Voltage-clamp studies confirmed that this action-potential-duration prolongation stems from a significant reduction of the cardiac potassium current I(Kr). Importantly, LQTS-derived cells also showed marked arrhythmogenicity, characterized by early-after depolarizations and triggered arrhythmias. We then used the LQTS human iPSC-derived cardiac-tissue model to evaluate the potency of existing and novel pharmacological agents that may either aggravate (potassium-channel blockers) or ameliorate (calcium-channel blockers, K(ATP)-channel openers and late sodium-channel blockers) the disease phenotype. Our study illustrates the ability of human iPSC technology to model the abnormal functional phenotype of an inherited cardiac disorder and to identify potential new therapeutic agents. As such, it represents a promising paradigm to study disease mechanisms, optimize patient care (personalized medicine), and aid in the development of new therapies.

Mechanism of spontaneous excitability in human embryonic stem cell derived cardiomyocytes.

Abstract: Human embryonic stem cells are capable of unlimited proliferation in culture in the undifferentiated state and under the proper conditions can differentiate into different cell types including spontaneously beating cardiac myocytes (Kehat et al. 2001, 2002). Spontaneous beating or automaticity is not normally exhibited by mature atrial or ventricular myocytes. In contrast, embryonic heart cells display spontaneous activity (DeHaan & Gottlieb, 1968). The main requirement for automaticity is the presence of inward current at diastolic potentials. Although two recent reports of human embryonic stem cell-derived cardiac myocytes (hES-CMs) document action potentials (He et al. 2003; Mummery et al. 2003), there are no studies of ionic currents in hES-CMs. Moreover, the more thoroughly studied mouse ES-derived CMs exhibit AP morphologies that broadly reflect either atrial-like, ventricular-like, or nodal-like parameters (Hescheler et al. 1999; Sachinidis et al. 2003) that differ markedly from their human counterparts. The cardiac Na+ channel (termed NaV1.5) is expressed in relatively high density on surface membrane of mature heart cells in atria and ventricle. Despite the high NaV1.5 expression these cell types are not normally automatic because a high density of inward rectifier K+ channels (Kir) clamps the membrane potential to a value near the K+ reversal potential. At such hyperpolarized potentials the NaV1.5 channel's open probability approaches 0. In quiescent, mature heart cells, the initiating depolarization originates from neighbouring cells via gap junctions. Depolarization of membrane potential (Vm) activates NaV1.5 rapidly, driving the rapid AP upstroke, and within a few milliseconds of sustained depolarization NaV1.5 inactivates. Thus, NaV1.5 serves the role of generating a pathway for a rapid influx of depolarizing current. The maximum diastolic potential (MDP) is a key control point for NaV1.5, if MDP is relatively depolarized then NaV1.5 will be largely inactivated and unable to contribute to the AP upstroke. For this reason, there is a correlation between Na+ channel current density (not simply channel density), and the maximum upstroke velocity of the cellular AP (dV/dtmax). Moreover, in the developing heart there is a an increase in dV/dtmax from < 20 to 100–150 V s−1 that is concomitant with the onset of TTX sensitivity (McDonald et al. 1973), an increase in Na+ current density (Fujii et al. 1988), and a negative shift in the MDP (McDonald et al. 1973; DeHaan, 1980; Sperelakis, 1984). Given the exciting potential use of hES-CMs as replacement tissue in diseased heart (Gepstein, 2002; Kehat & Gepstein, 2003), and as an in vitro model for the study of early human cardiac development it is important to characterize their functional properties. We assessed the electrical properties of these cells in spontaneously beating embryoid bodies (EBs) using a multielectrode array mapping technique and detailed patch-clamp recordings and pharmacologically dissected the critical pathways in these structures. Our results provide the first description of the ionic currents in hES-CMs and show that the basis for spontaneous electrical activity in these cells is the absence of Kir conductance, a phenomenon that provides the substrate for a relatively large voltage-gated Na+ current to drive activity.

Identification and selection of cardiomyocytes during human embryonic stem cell differentiation

Abstract: Human embryonic stem cells (hESC) are pluripotent lines that can differentiate in vitro into cell derivatives of all three germ layers, including cardiomyocytes. Successful application of these unique cells in the areas of cardiovascular research and regenerative medicine has been hampered by difficulties in identifying and selecting specific cardiac progenitor cells from the mixed population of differentiating cells. We report the generation of stable transgenic hESC lines, using lentiviral vectors, and single-cell clones that express a reporter gene (eGFP) under the transcriptional control of a cardiac-specific promoter (the human myosin light chain-2V promoter). Our results demonstrate the appearance of eGFP-expressing cells during the differentiation of the hESC as embryoid bodies (EBs) that can be identified and sorted using FACS (purity>95%, viability>85%). The eGFP-expressing cells were stained positively for cardiac-specific proteins (>93%), expressed cardiac-specific genes, displayed cardiac-spec...

In vitro electrophysiological drug testing using human embryonic stem cell derived cardiomyocytes.

Abstract: Pro-arrhythmia (development of cardiac arrhythmias as a pharmacological side effect) has become the single most common cause of the withdrawal or restrictions of previously marketed drugs. The deve...

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Stem-cell therapy for cardiac disease

Abstract: Heart failure is the leading cause of death worldwide, and current therapies only delay progression of the disease. Laboratory experiments and recent clinical trials suggest that cell-based therapies can improve cardiac function, and the implications of this for cardiac regeneration are causing great excitement. Bone-marrow-derived progenitor cells and other progenitor cells can differentiate into vascular cell types, restoring blood flow. More recently, resident cardiac stem cells have been shown to differentiate into multiple cell types present in the heart, including cardiac muscle cells, indicating that the heart is not terminally differentiated. These new findings have stimulated optimism that the progression of heart failure can be prevented or even reversed with cell-based therapy.

Embryonic stem cells.

Abstract: Embryonic stem cells have huge potential in the field of tissue engineering and regenerative medicine as they hold the capacity to produce every type of cell and tissue in the body. In theory, the treatment of human disease could be revolutionized by the ability to generate any cell, tissue, or even organ, 'on demand' in the laboratory. This work reviews the history of murine and human ES cell lines, including practical and ethical aspects of ES cell isolation from pre-implantation embryos, maintenance of undifferentiated ES cell lines in the cell culture environment, and differentiation of ES cells in vitro and in vivo into mature somatic cell types. Finally, we discuss advances towards the clinical application of ES cell technology, and some of the obstacles which must be overcome before large scale clinical trials can be considered.

The promise of induced pluripotent stem cells in research and therapy

Abstract: The field of stem-cell biology has been catapulted forward by the startling development of reprogramming technology. The ability to restore pluripotency to somatic cells through the ectopic co-expression of reprogramming factors has created powerful new opportunities for modelling human diseases and offers hope for personalized regenerative cell therapies. While the field is racing ahead, some researchers are pausing to evaluate whether induced pluripotent stem cells are indeed the true equivalents of embryonic stem cells and whether subtle differences between these types of cell might affect their research applications and therapeutic potential.