Biomedical subjects

Neta Lavon

Publications and source records attributed to Neta Lavon.

4 recordsLinked to original sources

PubMed2006

The effect of overexpression of Pdx1 and Foxa2 on the differentiation of human embryonic stem cells into pancreatic cells.

Human embryonic stem cells (HESCs) are pluripotent cells that may serve as a source of cells for transplantation medicine and as a tool to study human embryogenesis. Using genetic manipulation methodologies, we have investigated the potential of HESCs to differentiate into the various pancreatic cell types. We initially created various HESCs carrying the enhanced green fluorescent protein (eGFP) reporter gene under the control of either the insulin promoter or the pancreatic and duodenal homeobox factor-1 (Pdx1) promoter. Our analysis revealed that during the differentiation of HESCs into embryoid bodies (EBs), we could detect green fluorescent cells when eGFP is regulated by Pdx1 promoter but not by insulin promoter. To examine whether we can induce differentiation into pancreatic cells, we have established human embryonic stem cell lines that constitutively express either Pdx1 or the endodermal transcription factor Foxa2. Following differentiation into EBs, the constitutive expression of Pdx1 enhanced the differentiation of HESCs toward pancreatic endocrine and exocrine cell types. Thus, we have demonstrated expression of several transcription factors that are downstream of Pdx1 and various molecular markers for the different pancreatic cell types. However, the expression of the insulin gene could be demonstrated only when the cells differentiated in vivo into teratomas. We conclude that although overexpression of Pdx1 enhanced expression of pancreatic enriched genes, induction of insulin expression may require additional signals that are only present in vivo.

Animals↗

PubMed2005

Study of hepatocyte differentiation using embryonic stem cells.

The liver has many crucial functions including metabolizing dietary molecules, detoxifying compounds, and storing glycogen. The hepatocytes, comprising most of the liver organ, progressively modify their gene expression profile during the fetal development according to their roles in the different phases of development. Embryonic stem (ES) cells serve as a major tool in understanding liver development. These cells may also serve as a source of hepatic cells for cellular therapy. In this review, we aim to summarize the research that has been performed in the field of hepatocyte differentiation from mouse and human ES cells. We discuss the various methodologies for the differentiation of ES cells towards hepatic cells using either spontaneous or directed differentiation protocols. Although many protocols for differentiating ES cells to hepatic cells have been developed, the analysis of their status is not trivial and can lead to various conclusions. Hence, we discuss the issues of analyzing hepatocytes by means of the specificity of the markers for hepatocytes and the status of the cells as fetal or adult hepatocytes.

Animals↗

PubMed2004

Differentiation and isolation of hepatic-like cells from human embryonic stem cells.

Human embryonic stem cells are pluripotent cells that can serve as a cell source for transplantation medicine, and as a tool to study human embryogenesis. We investigate here the potential of human embryonic stem cells to differentiate into hepatic cells. We have characterized the expression level of liver-enriched genes in undifferentiated and differentiated human embryonic stem cells by DNA microarrays. Our analysis revealed a subset of fetal hepatic enriched genes that are expressed in human embryonic stem cells upon differentiation into embryoid bodies. In order to isolate the hepatic-like cells, we introduced a reporter gene regulated by a hepatocyte-specific promoter into human embryonic stem cells. We isolated clones of human embryonic stem cells that express enhanced green fluorescent protein upon in vitro differentiation. Through immunostaining, we showed that most of these cells express albumin, while some cells still express the earlier expressed protein alpha-fetoprotein. Using fluorescence activated cell sorter, we were able to sort out the fluorescent differentiated cells and expand them for a few more weeks. This is the first report to demonstrate the possibility of purifying differentiated derivatives of human embryonic stem cells and culturing them further. Through confocal microscopy, we detected clusters of hepatic-like cells in 20-day-old embryoid bodies and in teratomas. As observed during embryonic development, we showed that in teratomas, the hepatic-like endodermal cells develop next to cardiac mesodermal cells. In order to examine the secreted factors involved in the induction of hepatic differentiation, human embryonic stem cells were grown in the presence of various growth factors, demonstrating the potential involvement of acidic fibroblast growth factor in the differentiation. In conclusion, given certain growth conditions and genetic manipulation, we can now differentiate and isolate hepatic-like cells from human embryonic stem cells.

Cell Differentiation↗

PubMed2003

Differentiation and genetic manipulation of human embryonic stem cells and the analysis of the cardiovascular system.

Human embryonic stem (ES) cells are pluripotent cells derived from blastocyst-stage embryos. The cells are characterized by their self-renewal capability and by their ability to differentiate into a wide range of cell types. In vivo, injection of the human ES cells into immune-deficient mice generates teratomas harboring derivatives of all three embryonic germ layers. In vitro, spontaneous aggregation of human ES cells results in the formation of embryoid bodies (EBs) comprised of differentiated cells from the three embryonic germ layers. Induced differentiation of ES cells into specific subsets of cells may be generated by treatment with several growth factors. Cardiomyocytes and endothelial cells were among the tissue types identified in vitro, and one of the most dramatic examples for the differentiation of human ES cells is the formation of rhythmic contractions of EBs containing pulsing cardiac muscle cells. Cells of the cardiovascular system were characterized by many molecular markers and by their structural and functional properties. The ability to genetically manipulate human ES cells now allows for the purification of specific cell types. Human ES cells have tremendous value as an in vitro model to study embryonic differentiation and as a source of cells for cellular transplantation in various pathologies among them cardiovascular diseases.

Animals↗