Tissue-specific progenitor cells are characterized by proliferation and differentiation, but, in contrast to embryonic stem (ES) cells, have limited capacities for self-renewal and no tumourigenic potential. These latter traits make progenitor cells an ideal source for regenerative cell therapies. In this review, we describe what is currently known about nestin, an intermediate filament first identified in neuroepithelial stem cells. During embryogenesis, nestin is expressed in migrating and proliferating cells, whereas in adult tissues, nestin is mainly restricted to areas of regeneration. We show that nestin is abundant in ES-derived progenitor cells that have the potential to develop into neuroectodermal, endodermal and mesodermal lineages. Although it remains unclear what factors regulate in vitro and in vivo expression of nestin, we conclude that nestin represents a characteristic marker of multi-lineage progenitor cells and suggest that its presence in cells may indicate multi-potentiality and regenerative potential.

Mouse embryonic stem (ES) cells were used as an experimental model to study the effects of electromagnetic fields (EMF). ES-derived nestin-positive neural progenitor cells were exposed to extremely low frequency EMF simulating power line magnetic fields at 50 Hz (ELF-EMF) and to radiofrequency EMF simulating the Global System for Mobile Communication (GSM) signals at 1.71 GHz (RF-EMF). Following EMF exposure, cells were analyzed for transcript levels of cell cycle regulatory, apoptosis-related, and neural-specific genes and proteins; changes in proliferation; apoptosis; and cytogenetic effects. Quantitative RT-PCR analysis revealed that ELF-EMF exposure to ES-derived neural cells significantly affected transcript levels of the apoptosis-related bcl-2, bax, and cell cycle regulatory "growth arrest DNA damage inducible" GADD45 genes, whereas mRNA levels of neural-specific genes were not affected. RF-EMF exposure of neural progenitor cells resulted in down-regulation of neural-specific Nurr1 and in up-regulation of bax and GADD45 mRNA levels. Short-term RF-EMF exposure for 6 h, but not for 48 h, resulted in a low and transient increase of DNA double-strand breaks. No effects of ELF- and RF-EMF on mitochondrial function, nuclear apoptosis, cell proliferation, and chromosomal alterations were observed. We may conclude that EMF exposure of ES-derived neural progenitor cells transiently affects the transcript level of genes related to apoptosis and cell cycle control. However, these responses are not associated with detectable changes of cell physiology, suggesting compensatory mechanisms at the translational and posttranslational level.

Here, we describe the generation of viable and dopamine-producing neurons derived from pluripotent mouse embryonic stem cells. Neurotrophic factors in combination with survival-promoting factors, such as interleukin-1beta, glial cell line-derived neurotrophic factor, neurturin, transforming growth factor-beta(3) and dibutyryl-cyclic AMP, significantly enhanced Nurr1 and tyrosine hydroxylase (TH) mRNA levels, whereas En-1, mash-1 and dopamine-2-receptor mRNA levels were not upregulated. In parallel, mRNA levels of the anti-apoptotic gene bcl-2 were found to be upregulated at terminal stages. Double immunofluorescence analysis revealed increased numbers of TH- and dopamine transporter-, but not gamma-aminobutyric acid- and serotonin-positive neurons in relation to synaptophysin-labeled cells by survival-promoting factors. Moreover, high-performance liquid chromatography analysis showed detectable levels of intracellular dopamine. We conclude that survival-promoting factors enhance differentiation, survival and maintenance of dopaminergic neurons derived from embryonic stem cells.

Here, we describe a basic protocol for the in vitro differentiation of mouse embryonic stem (ES) cells into insulin-producing cells. The three-step protocol comprises (i) the formation of embryoid bodies, (ii) the spontaneous differentiation of embryoid bodies into progenitor cells of ecto-, meso- and endodermal lineages, and (iii) the induction of differentiation of early progenitors into the pancreatic lineage. Differentiated cells can be obtained within approximately 33 d. Differentiation induction by growth and extracellular-matrix factors, including laminin, nicotinamide and insulin, leads to the formation of ES-derived progeny that resembles cells committed to the pancreatic lineage. During differentiation, transcript levels of genes expressed in early pancreatic cells are upregulated. Continued differentiation results in the development of C-peptide/insulin-positive islet-like clusters that release insulin upon glucose stimulation. Differentiated ES cells that overexpress the pancreatic developmental control gene Pax4 develop insulin-secretory granules and reveal functional properties with respect to the pancreas-specific ATP-modulated K+ channel and the normalization of glycemia of streptozotocin-treated diabetic mice.

Background: P53 is a key tumor suppressor protein. In response to DNA damage, p53 accumulates to high levels in differentiated cells and activates target genes that initiate cell cycle arrest and apoptosis. Since stem cells provide the proliferative cell pool within organisms, an efficient DNA damage response is crucial.