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Biomedical subjects

Joseph Itskovitz-Eldor

Publications and source records attributed to Joseph Itskovitz-Eldor.

At least 55 records · Page 3Linked to original sources
PubMed2004

Controlled, scalable embryonic stem cell differentiation culture.

Embryonic stem (ES) cells are of significant interest as a renewable source of therapeutically useful cells. ES cell aggregation is important for both human and mouse embryoid body (EB) formation and the subsequent generation of ES cell derivatives. Aggregation between EBs (agglomeration), however, inhibits cell growth and differentiation in stirred or high-cell-density static cultures. We demonstrate that the agglomeration of two EBs is initiated by E-cadherin-mediated cell attachment and followed by active cell migration. We report the development of a technology capable of controlling cell-cell interactions in scalable culture by the mass encapsulation of ES cells in size-specified agarose capsules. When placed in stirred-suspension bioreactors, encapsulated ES cells can be used to produce scalable quantities of hematopoietic progenitor cells in a controlled environment.

Animals↗
PubMed2004

LIF/STAT3 signaling fails to maintain self-renewal of human embryonic stem cells.

Murine embryonic stem (mES) cells remain undifferentiated in the presence of leukemia inhibitory factor (LIF), and activation of signal transducer and activator of transcription 3 (STAT3) via LIF receptor (LIFR) signaling appears sufficient for maintenance of mES cell pluripotency. Anecdotal and contradictory accounts exist for the action of LIF in the culture of human embryonic stem cells, and the nature of LIF signaling and whether the LIF-STAT3 pathway is conserved in human embryonic stem cells (hESCs) has not been systematically explored. In this study, we show that the LIFRbeta and the signaling subunit gp130 are expressed in hESCs and that human LIF can induce STAT3 phosphorylation and nuclear translocation in hESCs. Nevertheless, despite the functional activation of the LIF-STAT3 signaling pathway, human LIF is unable to maintain the pluripotent state of hESCs. Feeder-free culture conditions that maintain hESCs in an undifferentiated state do not show activation of STAT3, suggesting that distinct signaling mechanisms govern the self-renewal of hESCs.

Active Transport, Cell Nucleus↗
PubMed2003

Gene expression in human embryonic stem cell lines: unique molecular signature.

Human embryonic stem (huES) cells have the ability to differentiate into a variety of cell lineages and potentially provide a source of differentiated cells for many therapeutic uses. However, little is known about the mechanism of differentiation of huES cells and factors regulating cell development. We have used high-quality microarrays containing 16 659 seventy-base pair oligonucleotides to examine gene expression in 6 of the 11 available huES cell lines. Expression was compared against pooled RNA from multiple tissues (universal RNA) and genes enriched in huES cells were identified. All 6 cell lines expressed multiple markers of the undifferentiated state and shared significant homology in gene expression (overall similarity coefficient > 0.85).A common subset of 92 genes was identified that included Nanog, GTCM-1, connexin 43 (GJA1), oct-4, and TDGF1 (cripto). Gene expression was confirmed by a variety of techniques including comparison with databases, reverse transcriptase-polymerase chain reaction, focused cDNA microarrays, and immunocytochemistry. Comparison with published "stemness" genes revealed a limited overlap, suggesting little similarity with other stem cell populations. Several novel ES cell-specific expressed sequence tags were identified and mapped to the human genome. These results represent the first detailed characterization of undifferentiated huES cells and provide a unique set of markers to profile and better understand the biology of huES cells.

Animals↗
PubMed2003

Differentiation of human embryonic stem cells on three-dimensional polymer scaffolds.

Human embryonic stem (hES) cells hold promise as an unlimited source of cells for transplantation therapies. However, control of their proliferation and differentiation into complex, viable 3D tissues is challenging. Here we examine the use of biodegradable polymer scaffolds for promoting hES cell growth and differentiation and formation of 3D structures. We show that complex structures with features of various committed embryonic tissues can be generated, in vitro, by using early differentiating hES cells and further inducing their differentiation in a supportive 3D environment such as poly(lactic-co-glycolic acid)/poly(L-lactic acid) polymer scaffolds. We found that hES cell differentiation and organization can be influenced by the scaffold and directed by growth factors such as retinoic acid, transforming growth factor beta, activin-A, or insulin-like growth factor. These growth factors induced differentiation into 3D structures with characteristics of developing neural tissues, cartilage, or liver, respectively. In addition, formation of a 3D vessel-like network was observed. When transplanted into severe combined immunodeficient mice, the constructs continue to express specific human proteins in defined differentiated structures and appear to recruit and anastamose with the host vasculature. This approach provides a unique culture system for addressing questions in cell and developmental biology, and provides a potential mechanism for creating viable human tissue structures for therapeutic applications.

Animals↗
PubMed2003

Human embryonic stem cells for cardiovascular repair.

The critical loss of functional cardiomyocytes causes severe deterioration of pump function, resulting in heart failure. The possibility to regenerate or repair damaged or ischemic cardiac tissue is a great challenge for the future treatment of end-stage heart failure. As cardiomyocytes cannot be regenerated in adults, current therapeutic modalities for the treatment of end-stage heart failure are limited and include medical therapy, mechanical left ventricular assist devices, and cardiac transplantation. This review will focus on the potential use of human embryonic stem (hES) cell-derived cardiomyocytes and vascular cells, as a therapeutic tool for the treatment of myocardial infarction and end-stage heart failure.

Cardiomyopathies↗
PubMed2003

Influence of maternal carbohydrate intake on fetal movements at 14 to 16 weeks of gestation.

OBJECTIVE: Ultrasonographic assessment of fetal movements at 14 to 16 weeks of gestation before and after maternal oral intake of carbohydrate. DESIGN: Thirty consecutive healthy pregnant women between 14 and 16 weeks of gestation were scanned transvaginally. Real-time ultrasound recordings of 20 min duration were performed in the fasting state and after an oral intake of 110 g of glucose. The number of fetal movements, body and limb movements and breathing movements were evaluated. Fetal movements were quantified using a digital chronometer, and the percentage of time spent moving and the rate of movements per minute were then calculated. Data was statistically analyzed using the simple and Wilcoxon paired t-test. RESULTS: Absolute number of fetal movements, body movements, rotation movements, time spent moving and rate of movements per minute showed a statistically significant increase after maternal intake of carbohydrate (p < 0.0001). CONCLUSIONS: Maternal oral intake of 110 g of carbohydrate significantly increases fetal movements at 14 to 16 weeks of gestation, thus allowing better ultrasonographic viewing of the fetus.

Adult↗
PubMed2003

Lower levels of inhibin A and pro-alphaC during the luteal phase after triggering oocyte maturation with a gonadotropin-releasing hormone agonist versus human chorionic gonadotropin.

OBJECTIVE: To investigate the effect of triggering oocyte maturation with GnRH agonist on corpus luteum function by measuring luteal phase levels of inhibin A and pro-alphaC. DESIGN: Prospective randomized trial. SETTING: In vitro fertilization (IVF) program at a university hospital. PATIENT(S): Infertile women undergoing IVF-ET treatment. INTERVENTION(S): Controlled ovarian hyperstimulation with FSH and GnRH antagonist, triggering of final oocyte maturation with either hCG (n = 8) or GnRH agonist (n = 8), IVF-ET, and collection of blood samples every 2-3 days during the luteal phase. MEASUREMENTS AND MAIN RESULTS: Luteal phase serum levels of inhibin A and pro-alphaC, P, and E(2). RESULT(S): Levels of inhibin A, pro-alphaC, estrogen, and P were significantly lower from day 4 to day 14 after triggering final oocyte maturation by GnRH agonist compared with hCG. Maximal luteal serum inhibin A and pro-alphaC levels were 91.5 +/- 23.6 and 184.1 +/- 23.5 pg/mL in the GnRH agonist-treated women compared with 464.7 +/- 209.1 and 7,351.6 +/- 934.3 pg/mL in women treated with hCG. CONCLUSION(S): Triggering final oocyte maturation with GnRH agonist instead of hCG in IVF cycles dramatically decreases luteal levels of inhibins, reflecting significant inhibition of the corpus luteum function. This effect may explain, at least in part, the mechanism of ovarian hyperstimulation syndrome prevention by the use of GnRH agonist.

Adult↗
PubMed2003

Human embryonic stem cells as an in vitro model for human vascular development and the induction of vascular differentiation.

Early embryonic blood vessels are typically composed of fragile tubes of endothelial cells encircled by vascular smooth muscle cells. Early human vasculogenesis was explored in spontaneous and directed differentiation models derived from human embryonic stem (HES) cells. In a 3-dimensional (3D) model, HES cells were studied for their potential for vascular differentiation during the spontaneous formation of embryoid bodies. Directed differentiation was investigated by means of a 2-dimensional (2D) differentiation method to promote vascular differentiation from HES cells (without the formation of embryoid bodies). Using this latter approach, up-regulation of early lineage markers of endothelial progenitors were induced. Additional culture under strict conditions and exposure to angiogenic growth factors resulted in a prolonged differentiation pathway into mature endothelial cells and up-regulation of vascular smooth muscle cell markers. The use of 3D collagen gels and Matrigel assays for the induction and inhibition of human vascular sprouting in vitro further established the vascular potential of the cells generated by the 2D differentiation system. Our study shows that HES cells can provide useful models to study early differentiation and development of blood vessels. Moreover, the 2D differentiation model facilitates both the production of vascular lineage cells from HES cells for various potential therapeutic applications and also provides a model for studying the mechanisms involved in early human embryonic blood vessel development.

Becaplermin↗
PubMed2003

Assessment of the ultrastructural and proliferative properties of human embryonic stem cell-derived cardiomyocytes.

Assessment of early ultrastructural development and cell-cycle regulation in human cardiac tissue is significantly hampered by the lack of a suitable in vitro model. Here we describe the possible utilization of human embryonic stem cell (ES) lines for investigation of these processes. With the use of the embryoid body (EB) differentiation system, human ES cell-derived cardiomyocytes at different developmental stages were isolated and their histomorphometric, ultrastructural, and proliferative properties were characterized. Histomorphometric analysis revealed an increase in cell length, area, and length-to-width ratio in late-stage EBs (>35 days) compared with early (10-21 days) and intermediate (21-35 days) stages. This was coupled with a progressive ultrastructural development from an irregular myofibrillar distribution to an organized sarcomeric pattern. Cardiomyocyte proliferation, assessed by double labeling with cardiac-specific antibodies and either [3H]thymidine incorporation or Ki-67 immunolabeling, demonstrated a gradual withdrawal from cell cycle. Hence, the percentage of positively stained nuclei in early-stage cardiomyocytes ([3H]thymidine: 60 +/- 10%, Ki-67: 54 +/- 23%) decreased to 36 +/- 7% and 9 +/- 16% in intermediate-stage EBs and to <1% in late-stage cardiomyocytes. In conclusion, a reproducible temporal pattern of early cardiomyocyte proliferation, cell-cycle withdrawal, and ultrastructural maturation was noted in this model. Establishment of this unique in vitro surrogate system may allow to examine the molecular mechanisms underlying these processes and to assess interventions aiming to modify these properties. Moreover, the detailed characterization of the ES cell-derived cardiomyocyte may be crucial for the development of future cell replacement strategies aiming to regenerate functional myocardium.

Cell Differentiation↗
PubMed2003

Selective ablation of human embryonic stem cells expressing a "suicide" gene.

Over the past few years, technological procedures have been developed for utilizing stem cells in transplantation medicine. Human embryonic stem (ES) cells can produce an unlimited number of differentiated cells and are, therefore, considered a potential source of cellular material for use in transplantation medicine. However, serious clinical problems can arise when uncontrolled cell proliferation occurs following transplantation. To avoid these potential problems, we genetically engineered human ES cell lines to express the herpes simplex virus thymidine kinase (HSV-tk) gene. Expression of the HSV-tk protein renders the ES cells sensitive to the U.S. Food and Drug Administration-approved drug ganciclovir, inducing destruction of HSV-tk(+) cells at ganciclovir concentrations that are nonlethal to other cell types. The reversion rate of engineered cells was low even under prolonged selection with ganciclovir. The HSV-tk(+) clones retained a normal karyotype and the ability to differentiate to cells from all three germ layers. Most importantly, tumors that arose in mice following subcutaneous injection of HSV-tk(+) human ES cells could be ablated in vivo by administration of ganciclovir. By utilizing these cell lines, safety levels can be improved in transplantations involving tissues derived from human ES cells.

Animals↗
PubMed2002

High-resolution electrophysiological assessment of human embryonic stem cell-derived cardiomyocytes: a novel in vitro model for the study of conduction.

The goal of the present report was to establish a new in vitro model for the study of impulse propagation in human cardiac tissue. By using the human embryonic stem cell differentiating system, spontaneously contracting areas were generated in three-dimensional differentiating cell aggregates (embryoid bodies). Morphological analysis revealed an isotropic tissue of early-stage cardiac phenotype. Gap junctions, assessed by immunostaining of connexin43 and connexin45, were distributed along the cell borders. High-resolution activation maps demonstrated the presence of a functional syncytium with stable focal activation and conduction properties. Conduction was significantly slower in narrow bands of contracting tissue compared with broad cardiomyocyte regions. Establishment of this unique in vitro human model may be used for the assessment of long-term structure-function relationships, for pharmacological studies, for tissue engineering, and may permit the study of genetically modified cardiomyocytes.

Action Potentials↗
PubMed2002

Characterization of the expression of MHC proteins in human embryonic stem cells.

Human embryonic stem (ES) cells are pluripotent cells that may be used in transplantation medicine. These cells can be induced to differentiate into cells from the three embryonic germ layers both in vivo and in vitro. To determine whether human ES cells might be rejected after transplantation, we examined cell surface expression of the MHC proteins in these cells. Our results show very low expression levels of MHC class I (MHC-I) proteins on the surface of human ES cells that moderately increase on in vitro or in vivo differentiation. A dramatic induction of MHC-I proteins was observed when the cells were treated with IFN-gamma but not with IFN-alpha or -beta. However, all three IFNs induced expression of MHC-I proteins in differentiated human ES cells. MHC-II proteins and HLA-G were not expressed on the surface of undifferentiated or differentiated cells. Ligands for natural killer cell receptors were either absent or expressed in very low levels in human ES cells and in their differentiated derivatives. In accordance, natural killer cytotoxic assays demonstrated only limited lysis of both undifferentiated and differentiated cells. To initiate a histocompatibility databank of human ES cells, we have isotyped several of the published ES cell lines for their human leukocyte antigens. In conclusion, our results demonstrate that human ES cells can express high levels of MHC-I proteins and thus may be rejected on transplantation.

Cell Differentiation↗
PubMed2002

Endothelial cells derived from human embryonic stem cells.

Human embryonic stem cells have the potential to differentiate into various cell types and, thus, may be useful as a source of cells for transplantation or tissue engineering. We describe here the differentiation steps of human embryonic stem cells into endothelial cells forming vascular-like structures. The human embryonic-derived endothelial cells were isolated by using platelet endothelial cell-adhesion molecule-1 (PECAM1) antibodies, their behavior was characterized in vitro and in vivo, and their potential in tissue engineering was examined. We show that the isolated embryonic PECAM1+ cells, grown in culture, display characteristics similar to vessel endothelium. The cells express endothelial cell markers in a pattern similar to human umbilical vein endothelial cells, their junctions are correctly organized, and they have high metabolism of acetylated low-density lipoprotein. In addition, the cells are able to differentiate and form tube-like structures when cultured on matrigel. In vivo, when transplanted into SCID mice, the cells appeared to form microvessels containing mouse blood cells. With further studies, these cells could provide a source of human endothelial cells that could be beneficial for potential applications such as engineering new blood vessels, endothelial cell transplantation into the heart for myocardial regeneration, and induction of angiogenesis for treatment of regional ischemia.

Cell Differentiation↗
PubMed2002

Derivation and spontaneous differentiation of human embryonic stem cells.

Embryonic stem (ES) cells are unique cells derived from the inner cell mass of the mammalian blastocyst. These cells are immortal and pluripotent, retain their developmental potential after prolonged culture, and can be continuously cultured in an undifferentiated state. Many in vitro differentiation systems have been developed for mouse ES cells, including reproducible methods for mouse ES cell differentiation into haematopoietic and neural precursors, cardiomyocytes, insulin-secreting cells, endothelial cells and various other cell types. The derivation of new human ES cell lines provides the opportunity to develop unique models for developmental research and for cell therapies. In this review we consider the derivation and spontaneous differentiation of human ES cells.

Blastocyst↗
PubMed2002

Menstrual cycle effects on the neurohumoral and autonomic nervous systems regulating the cardiovascular system.

Gonadal hormones may affect homeostatic mechanisms regulating the cardiovascular system. We investigated this relationship at five different crucial hormonal time points along the menstrual cycle. Eight eumenorrheic healthy subjects underwent a battery of autonomic tests, hemodynamics, and volume-regulatory hormone measurements. Fluid-regulatory hormones, plasma renin activity, and aldosterone increased along the luteal phase (P = 0.003 and 0.02, respectively), whereas rest supine-corrected hematocrit declined in the course of the menstrual cycle (P = 0.001). Plasma norepinephrine decreased from 1.4 +/- 0.2 to 0.95 +/- 0.1 nmol/liter (P < 0.02) [early follicular (EF) to late follicular]. Thereafter, concentrations gradually returned to EF levels. Lf to Hf domain ratio (spectral analysis of electrocardiogram) showed a difference from that of norepinephrine. The cardiovagal baroreflex sensitivity increased significantly along the luteal phase (P = 0.04). The dose of isoproterenol required to increase heart rate (HR) 15 beats per minute was 0.19 +/- 0.04 microg during the EF time point, and it increased to 0.39 +/- 0.06 microg during the late luteal time point (P = 0.05). However, blood pressure, HR, and their responses to orthostatic stress remained unchanged. Fluctuations in the ovarian hormones along the menstrual cycle are associated with unchanged blood pressure and HR, despite the significant variations in the different homeostatic mechanisms regulating the cardiovascular system.

Adrenergic beta-Agonists↗