Early, middle, and late stages of neural cells from ovine embryo in primary cultures

Autophagic processes increase during senescence in cultured sheep neurons and astrocytes

A possible response to aging is autophagy, a self-digestion process in which portions of cytoplasm are encapsulated by double-membrane-bound structures and delivered to lysosome for degradation. A previous work of our group showed that astrocytes under starving conditions are characterized by a higher upregulation of the marker of autophagy LC3 II than neurons. Aim of the present work was to evaluate LC3 II expression in an aging model consisting in fetal sheep neurons and astrocytes at 10, 20 and 30 days of culture. Such model has been validated by a remarkable activity of β-galactosidase, commonly used to reveal cell aging. LC3 II immunoreactivity in neurons and astrocytes progressively increased with time but differences were observed on the basis of cell density. Indeed, LC3 II immunoreactivity is higher in clusters of neurons and astrocytes and this may be due to the fact that cell-cell contact would represent a second stress in addition to aging itself. Both cell types displayed a reduction in LC3 II signal in nuclei, and a corresponding strengthening in the cytoplasm with time. This may be due to the need of aged cells to remove damaged cytoplasmic components through autophagic processes. Such variation in LC3 II localization could be caused by migration from the nucleus to cytoplasm as well as possible de novo intracytoplasmic production. The present work based on sheep neural cells in vitro may represent a helpful tool in the studies on aging processes in which autophagy plays a remarkable role.

Characterization of an established endothelial cell line from primary cultures of fetal sheep hypothalamus

Immortalized cell lines from fetal brain are an experimental model for studying the in vitro molecular pathways regulating neural cell differentiation and the development of neural networks. The procedures are described to obtain an established cell line from the 90-day old fetal sheep hypothalamus. Viral oncogene LT-SV40 transformation was used to isolate a stable cell line (ENOS-01) that was characterized immunocytochemically. Immortalized cells can be classified as an endothelial cell line of hypothalamic microvasculature. Furthermore, mRNA expression and immunocytochemical of estrogen receptors α and β were also evaluated. Since it is known that cerebral vessels are directly targeted by sex steroids, our established cell line represents an alternative system to study estradiol/receptor interactions during brain development. Our in vitro model can provide a tool to investigate the complex relationships among the cell types forming the blood-brain barrier, which is known to be involved in the pathogenesis of sheep transmissible neurological diseases.

A multiplexed quantitative proteomics approach for investigating protein expression in the developing central nervous system

Cell transplantation using stem cell-derived neurons is commonly viewed as a candidate therapy for neurodegenerative diseases. However, methods for differentiating stem cells into homogenous populations of neurons suitable for transplant remain elusive. This suggests that there are as yet unknown signalling factors working in vivo to specify neuronal cell fate during development. These factors could be manipulated to better differentiate stem cells into neural populations useful for therapeutic transplantation. Here a quantitative proteomics approach is described for investigating cell signalling in the developing central nervous system (CNS), using the embryonic ventral mesencephalon as a model. Briefly, total protein was extracted from embryonic ventral midbrain tissue before, during and after the birth of dopaminergic neurons, and digested using trypsin. Two-dimensional liquid chromatography, coupled with tandem mass spectrometry, was then used to identify proteins from the tryptic peptides. Isobaric tagging for relative and absolute quantification (iTRAQ) reagents were used to label the tryptic peptides and facilitate relative quantitative analysis. The success of the experiment was confirmed by the identification of proteins known to be expressed in the developing ventral midbrain, as well as by Western blotting, and immunolabelling of embryonic tissue sections. This method of protein discovery improves upon previous attempts to identify novel signalling factors through microarray analysis. Importantly, the methods described here could be applied to virtually any aspect of development.

Effects of Mandrax and Cannabis on the cellular function of chick embryonic neurons

Cannabis and Mandrax abuse is unique to South Africa; and most research has focused on the socio-economic impact rather than the adverse effects on the developing brain. Therefore, the aim of this study is to determine the effects of Mandrax and Cannabis alone and in combination on the developing brain by using primary and suspension cultures of the chick embryo brain. Exposure of primary chick embryo neuronal (CEN) cultures to the carrier ethanol, Mandrax and Cannabis, for 24h resulted in a significant dose dependent decrease in cell number for Mandarx alone. Increasing concentrations of Cannabis in combination with Mandrax inhibited the toxic effect of Mandrax. In CEN suspensions, Mandrax alone induced a significant time-concentration dependent decrease in esterase activity following 1 and 4h exposure. In combination with Cannabis, a significant increase in esterase activity was observed after 4h exposure. In conclusion Mandrax is toxic to CEN cells in vitro while Cannabis seemed to have a protective effect; however, this study does not investigate the abuse of these drugs in the form commonly abused, namely inhaled smoke.

Abnormal organelles in cultured astrocytes are largely enhanced by streptomycin and intensively by gentamicin

The effects of two aminoglycoside antibiotics on cultured astrocyte organelles were investigated in rat, sheep, and human cultured astrocytes using transmission electron microscopy. Marked changes in mitochondrial shapes were observed in cultured or subcultured astrocytes obtained from three species, including humans. As well, new types of organelles were observed: (i) numerous concentric membranes forming vesicles, which were termed multilamellar vesicles; and (ii) many vesicles gathering into membranous structures, which were termed multivesicular myeloid bodies. The number of abnormalities increased proportionally with increasing concentrations of the two aminoglycosides (streptomycin and gentamicin). The incorporation of peroxidase or albumin-gold complex in the abnormal vesicles showed that the endolysosomal system was involved in the formation of these vesicles. Our results show that: abnormal organelles are present in cultured astrocytes; these abnormalities are enhanced by streptomycin and gentamicin; and gentamicin induces more abnormalities than streptomycin. The binding of aminoglycosides to membrane phospholipids may explain the formation of the observed abnormalities in rat, sheep, and human cultured astrocytes.

The development and characterisation of complex ovine neuron cultures from fresh and frozen foetal neurons

Cultures of ovine cerebral and cerebellar neurons from mid-term sheep foetal brains, 9-15 weeks old, have been established for the first time. These foetal brains are relatively mature, being at similar stages of development as peri and post-natal rodent brains. Cultures were routinely maintained for 3-4 weeks, and longer. Nearly all the cells from the younger foetuses adhered as neurons. The proportion of glial cells increased with age, as did the risk of cultures being overtaken by glial cells. Cultured neurons were bipolar, tripolar and multipolar, similar to the morphologies of neurons in vivo. Older foetuses also yield more complex neurons, notably giant cells. Other properties of the cultured neurons also mimic in vivo observations, including neurite beading, complexity in neurotransmitter class (GABAergic and glutamatergic) and calcium binding protein (calbindin and calretinin) content. Single cell divisions of neurons were observed in younger cultures by time-lapse photography and the occurrence of telophase nuclei. The advantage of the high yield of genetically identical cells obtained from a single sheep foetus, 150 million, was extended by cryopreservation of neurons after snap freezing, and later culture. These cultures showed the same characteristics as cultures from the freshly plated cells.

Primary cultures from fetal bovine brain

This study describes a method of obtaining primary cultures from the cerebral cortex and the hypothalamus of bovine fetuses. We describe here the influence of tissue origin, developmental stage and culture medium conditions on cell differentiation and prevalence of neurons vs glial cells. To identify optimal conditions for obtaining and growing viable neurons and astrocytes in culture, we tested early, middle and late stages of development. Explants from cortex, early stages (week 10 of pregnancy out of 36) and low fetal calf serum concentration (1%) yielded maximum amounts of neurons. Fresh and thawed tissues gave comparable results.

Primary culture of neural precursors from the ovine central nervous system (CNS)

The present study demonstrates that bipotential neural precursors isolated from an early developmental stage of the sheep embryo nervous system can be maintained in vitro in an undifferentiated state for a long period. These precursors multiplied under the action of epidermal growth factor and basic fibroblast growth factor and formed free-floating aggregates of nestin-immunoreactive cells, called neurospheres. These precursors can undergo predominantly neural or glial differentiation according to the culture conditions. Medium supplemented with foetal calf serum mainly favoured cell differentiation predominantly into astrocytes, whereas the defined SATO medium favoured neuronal differentiation. Using various immunomarkers of neurones and astroglial cells, we described the course of differentiation of neuronal and astroglial cells in different culture conditions. The ability to grow neural precursors from common laboratory animals has been useful for studying the cellular and molecular mechanisms underlying the development of the central nervous system. Furthermore, neural progenitors are already being used for in vivo cell therapy in various neurodegenerative disorders. The ovine species is a well-known model for prion diseases, since scrapie is endemic in most countries and has been studied for a long time. In this respect, the availability of ovine neural precursors will add a new perspective to the study of the pathogenicity of prion diseases.

Establishment of astrocyte cell lines from sheep genetically susceptible to scrapie

Primary cultures of the brain from sheep embryos were used to establish cell lines after transfection by the simian virus 40 (SV40) large T gene. Two of the lines (A15 and 4A6) displayed astroglial properties. They expressed the glial fibrillary acidic protein (GFAP), intermediate filament protein vimentin, and S-100 (beta-subunit) protein. While numerous rodent and human glial cell lines are available, this is to our knowledge the first description of ovine cell lines with astrocyte features. In addition, these cell lines were derived from sheep embryos chosen for their genetic susceptibility to scrapie (PrP genotype: VV136, QQ171). Therefore, they could be attractive tissue culture models for the study of propagation and pathogenesis of the scrapie agent ex vivo.