Neuroectodermal Cell

Abstract: The histogenesis of retinoblastoma, the most common intraocular neoplasm of childhood, remains controversial. Previous studies have attributed the origin of the tumour to neuronal, glial or primitive stem cells of retina. In the study described here we have used immunofluorescence to search for the presence of a neuronal marker, neurone-specific enolase (NSE) and a glial marker, glial fibrillary acidic protein (GFAP), in the cells of the human retinoblastoma line Y-79 (ref. 4), before and after successful differentiation into neuronal and glial-like cells. We found that all undifferentiated cells contain both NSE and GFAP, whereas the differentiating neuronal and glial-like cells gradually lose one marker and selectively express the marker that correlates with their morphology. Our results support the notion that retinoblastoma originates from a primitive bipotential (or multipotential) neuroectodermal cell.

Abstract: Human adult bone marrow-derived mesodermal stromal cells (hMSCs) are able to differentiate into multiple mesodermal tissues, including bone and cartilage. There is evidence that these cells are able to break germ layer commitment and differentiate into cells expressing neuroectodermal properties. There is still debate about whether this results from cell fusion, aberrant marker gene expression or real neuroectodermal differentiation. Here we extend our work on neuroectodermal conversion of adult hMSCs in vitro by evaluating various epigenetic conversion protocols using quantitative RT-PCR and immunocytochemistry. Undifferentiated hMSCs expressed high levels of fibronectin as well as several neuroectodermal genes commonly used to characterize neural cell types, such as nestin, beta-tubulin III, and GFAP, suggesting that hMSCs retain the ability to differentiate into neuroectodermal cell types. Protocols using a direct differentiation of hMSCs into a neural phenotype failed to induce significant changes in morphology and/or expression of markers of early and mature glial/neuronal cells types. In contrast, a multistep protocol with conversion of hMSCs into a neural stem cell-like population and subsequent terminal differentiation in mature glia and neurons generated relevant morphological changes as well as significant increase of expression levels of marker genes for early and late neural cell types, such as nestin, neurogenin2, MBP, and MAP2ab, accompanied by a loss of their mesenchymal properties. Our data provide an impetus for differentiating hMSCs in vitro into mature neuroectodermal cells. Neuroectodermally converted hMSCs may therefore ultimately help in treating acute and chronic neurodegenerative diseases. Analysis of marker gene expression for characterization of neural cells derived from MSCs has to take into account that several early and late neuroectodermal genes are already expressed in undifferentiated MSCs.

Abstract: Neuroepithelial cell lines were established from cerebral vesicles of 9-day-old mouse embryos lacking functional p53 genes (Livingstone et al: Cell 70:923-935, 1992). All-trans retinoic acid (RA) induced bulk formation of neurons both in several p53-deficient neuroepithelial cell lines and in wild-type neural cells derived from early embryonic (E9-E12) forebrain vesicles. Forty-eight-hour treatment with 10(-6) M RA was necessary and sufficient to initiate neuron formation by p53(-/-)-progenitors, but neuronal characteristics appeared with a delay of 3-4 days. The first appearance of cells with astroglial features followed that of neurons with a further delay of 4-5 days. The establishment of neuronal phenotypes involved minimally three rounds of cell cycle. Future neurons were sorted out from substrate-attached cells and were characterized by a specific rearrangement of nestin-immunoreactive filaments. The formation of neuronal phenotypes was not synchronized within the RA-treated cell populations. The data indicate that RA, which promotes the initiation of neural differentiation, cannot function as a direct regulator of cell-fate decisions made by neural progenitor cells.