Murine brain progenitor cells have the ability to differentiate into functional neurons and integrate into the CNS

Article Commentary: Stem Cell Research in Cell Transplantation: An Analysis of Geopolitical Influence by Publications

One of the fastest growing fields in researching treatments for neurodegenerative and other disorders is the use of stem cells. These cells are naturally occurring and can be obtained from three different stages of an organism's life: embryonic, fetal, and adult. In the US, political doctrine has restricted use of federal funds for stem cells, enhancing research towards an adult source. In order to determine how this legislation may be represented by the stem cell field, a retrospective analysis of stem cell articles published in the journal Cell Transplantation over a 2-year period was performed. Cell Transplantation is considered a translational journal from preclinical to clinical, so it was of interest to determine the publication outcome of stem cell articles 6 years after the US regulations. The distribution of the source of stem cells was found to be biased towards the adult stage, but relatively similar over the embryonic and fetal stages. The fetal stem cell reports were primarily neural in origin, whereas the adult stem cell ones were predominantly mesenchymal and used mainly in neural studies. The majority of stem cell studies published in Cell Transplantation were found to fall under the umbrella of neuroscience research. American scientists published the most articles using stem cells with a bias towards adult stem cells, supporting the effect of the legislation, whereas Europe was the leading continent with a bias towards embryonic and fetal stem cells, where research is “controlled” but not restricted. Japan was also a major player in the use of stem cells. Allogeneic transplants (where donor and recipient are the same species) were the most common transplants recorded, although the transplantation of human-derived stem cells into rodents was the most common specific transplantation performed. This demonstrates that the use of stem cells is an increasingly important field (with a doubling of papers between 2005 and 2006), which is likely to develop into a major therapeutic area over the next few decades and that funding restrictions can affect the type of research being performed.

Effects of acute hypoxia/acidosis on intracellular pH in differentiating neural progenitor cells

The response of differentiating mouse neural progenitor cells, migrating out from neurospheres, to conditions simulating ischemia (hypoxia and extracellular or intracellular acidosis) was studied. We show here, by using BCECF and single cell imaging to monitor intracellular pH (pH(i)), that two main populations can be distinguished by exposing migrating neural progenitor cells to low extracellular pH or by performing an acidifying ammonium prepulse. The cells dominating at the periphery of the neurosphere culture, which were positive for neuron specific markers MAP-2, calbindin and NeuN had lower initial resting pH(i) and could also easily be further acidified by lowering the extracellular pH. Moreover, in this population, a more profound acidification was seen when the cells were acidified using the ammonium prepulse technique. However, when the cell population was exposed to depolarizing potassium concentrations no alterations in pH(i) took place in this population. In contrast, depolarization caused an increase in pH(i) (by 0.5 pH units) in the cell population closer to the neurosphere body, which region was positive for the radial cell marker (GLAST). This cell population, having higher resting pH(i) (pH 6.9-7.1) also responded to acute hypoxia. During hypoxic treatment the resting pH(i) decreased by 0.1 pH units and recovered rapidly after reoxygenation. Our results show that migrating neural progenitor cells are highly sensitive to extracellular acidosis and that irreversible damage becomes evident at pH 6.2. Moreover, our results show that a response to acidosis clearly distinguishes two individual cell populations probably representing neuronal and radial cells.

Transplantation of embryonic small hepatocytes induces regeneration of injured liver in adult rat

Small hepatocytes as hepatic stem cells or progenitors may be transplanted to treat several end-stage liver diseases. To identify the characteristics of epithelial cells enriched from fetal liver, we used immunocytochemistry and electron micrography. All cells in the colonies were immunocytochemically positive for alpha fetoprotein and cytokeratins (CK) 7, CK8, and CK18, which are markers of hepatic progenitor. Under transmission electron microscopy, we observed the cultured cells to show naive characteristics of stem cells and to be significantly distinct from mature hepatocytes. To identity whether these small hepatocytes were able to proliferate and differentiate into mature hepatocytes, we cultured them in vitro, and, through the portal vein, and transplanted elements whose membrane were stained with red fluorescence using PKH26 linker dye, into the livers of CCl(4)-treated rats that had been subjected to two-thirds partial hepatectomy. Significant liver regeneration was observed 30 days later in rats that did or did not receive the cells. The livers of hepatocytes recipients showed sharper edges and smoother surfaces than the control group. Diffused cells labeled with red fluorescence were observed in the portal area, with branch-like red fluorescence in regions near portal areas of some lobules, suggesting that these elements were involved in the repair of liver lobules and differentiation into mature hepatocytes. Our results revealed that small hepatocytes not only have characteristics of hepatic stem cells, but also may be a source of cellular transplantation to treat liver diseases.

Differentiation of nonhuman primate embryonic stem cells along neural lineages

The differentiation of embryonic stem cells (ESCs) into neurons and glial cells represents a promising cell-based therapy for neurodegenerative diseases. Because the rhesus macaque is physiologically and phylogenetically similar to humans, it is a clinically relevant animal model for ESC research. In this study, the pluripotency and neural differentiation potential of a rhesus monkey ESC line (ORMES6) was investigated. ORMES6 was derived from an in vitro produced blastocyst, which is the same way human ESCs have been derived. ORMES6 stably expressed the embryonic transcription factors POU5F1 (Oct4), Sox2 and NANOG. Stage-specific embryonic antigen 4 (SSEA 4) and the glycoproteins TRA-1-60 and TRA-1-81 were also expressed. The embryoid bodies (EBs) formed from ORMES6 ESCs spontaneously gave rise to cells of three germ layers. After exposure to basic fibroblast growth factor (bFGF) for 14-16 days, columnar rosette cells formed in the EB outgrowths. Sox2, microtubule-associated protein (MAP2), beta-tublinIII and glial fibrillary acidic protein (GFAP) genes and Nestin, FoxD3, Pax6 and beta-tublinIII antigens were expressed in the rosette cells. Oct4 and NANOG expression were remarkably down-regulated in these cells. After removal of bFGF from the medium, the rosette cells differentiated along neural lineages. The differentiated cells expressed MAP2, beta-tublinIII, Neuro D and GFAP genes. Most differentiated cells expressed early neuron-specific antigen beta-tublinIII (73+/-4.7%) and some expressed intermediate neuron antigen MAP2 (18+/-7.2%). However, some differentiated cells expressed the glial cell antigens A2B5 (7.17%+/-1.2%), GFAP (4.93+/-1.9%), S100 (7+/-3.5%) and O4 (0.27+/-0.2%). The rosette cells were transplanted into the striatum of immune-deficient NIHIII mice. The cells persisted for approximately 2 weeks and expressed Ki67, NeuN, MAP2 and GFAP. These results demonstrate that the rhesus monkey ESC line ORMES6 retains the pluripotent characteristics of ESCs and can be efficiently induced to differentiate along neural lineages.