Identification of Neurocan and Phosphacan as Early Biomarkers for Open Neural Tube Defects

Open neural tube defects (NTDs) such as myelomeningocele (MMC) are debilitating and the most common congenital defects of the central nervous system. Despite their apparent clinical importance, the existing early prenatal diagnostic options for these defects remain limited. Using a well-accepted retinoic-acid-induced model of MMC established in fetal rats, we discovered that neurocan and phosphacan, the secreted chondroitin sulfate proteoglycans of the developing nervous system, are released into the amniotic fluid (AF) of fetal rats displaying spinal cord defects. In contrast to normal controls, elevated AF levels of neurocan and phosphacan were detected in MMC fetuses early in gestation and continued to increase during MMC progression, reaching the highest level in near-term fetuses. The molecular forms of neurocan and phosphacan identified in the AF of MMC fetuses and those found in MMC spinal cords were qualitatively similar. In summary, this is the first report demonstrating the presence of neurocan and phosphacan in the AF of MMC fetuses. The identification of elevated levels of neurocan and phosphacan in the AF of MMC fetuses provides two prospective biomarkers with the potential for early prenatal diagnosis of open NTDs.

Viral expression of constitutively active AKT3 induces CST axonal sprouting and regeneration, but also promotes seizures

Increasing the intrinsic growth potential of neurons after injury has repeatedly been shown to promote some level of axonal regeneration in rodent models. One of the most studied pathways involves the activation of the PI3K/AKT/mTOR pathways, primarily by reducing the levels of PTEN, a negative regulator of PI3K. Likewise, activation of signal transducer and activator of transcription 3 (STAT3) has previously been shown to boost axonal regeneration and sprouting within the injured nervous system. Here, we examined the regeneration of the corticospinal tract (CST) after cortical expression of constitutively active (ca) Akt3 and STAT3, both separately and in combination. Overexpression of caAkt3 induced regeneration of CST axons past the injury site independent of caSTAT3 overexpression. STAT3 demonstrated improved axon sprouting compared to controls and contributed to a synergistic improvement in effects when combined with Akt3 but failed to promote axonal regeneration as an individual therapy. Despite showing impressive axonal regeneration, animals expressing Akt3 failed to show any functional improvement and deteriorated with time. During this period, we observed progressive Akt3 dose-dependent increase in behavioral seizures. Histology revealed increased phosphorylation of ribosomal S6 protein within the unilateral cortex, increased neuronal size, microglia activation and hemispheric enlargement (hemimegalencephaly).

Fourier transform infrared spectroscopy of developing bone mineral: from amorphous precursor to mature crystal

Bone mineral development has been described to proceed through an amorphous precursor prior to apatite crystallization. However, further analytical approaches are necessary to identify specific markers of amorphous mineral components in bone. Here, we establish an original Fourier transform infrared (FTIR) spectroscopy approach to allow the specific identification of the amorphous and/or crystalline nature of bone mineral. Using a series of standards, our results demonstrate that obtaining the second derivative of the FTIR spectra could reveal a peak specifically corresponding to amorphous calcium phosphate (ACP) at ∼992 cm-1. The intensity of this peak was strongly correlated to ACP content in standard mixtures. The analysis of a variety of bones showed that a clear ACP peak could be identified as a specific marker of the existence of an amorphous mineral component in developing bones. In contrast, the ACP peak was not detected in the mature bones. Moreover, subjecting developing bones to ex vivo crystallization conditions led to a clear reduction of the ACP peak, further substantiating the conversion of amorphous mineral precursor into mature apatite crystals. Analysis of mineralization in osteogenic cell cultures corroborated our observations, showing the presence of ACP as a major transient component in early mineralization, but not in the mature matrix. Additionally, FTIR imaging revealed that ACP was present in areas of matrix development, distributed around the edges of mineralizing nodules. Using an original analytical approach, this work provides strong evidence to support that bone mineral development is initiated by an amorphous precursor prior to apatite crystallization.

Spinal Cord Injury in Myelomeningocele: Prospects for Therapy

Myelomeningocele (MMC) is the most common congenital defect of the central nervous system and results in devastating and lifelong disability. In MMC, the initial failure of neural tube closure early in gestation is followed by a progressive prenatal injury to the exposed spinal cord, which contributes to the deterioration of neurological function in fetuses. Prenatal strategies to control the spinal cord injury offer an appealing therapeutic approach to improve neurological function, although the definitive pathophysiological mechanisms of injury remain to be fully elucidated. A better understanding of these mechanisms at the cellular and molecular level is of paramount importance for the development of targeted prenatal MMC therapies to minimize or eliminate the effects of the injury and improve neurological function. In this review article, we discuss the pathological development of MMC with a focus on in utero injury to the exposed spinal cord. We emphasize the need for a better understanding of the causative factors in MMC spinal cord injury, pathophysiological alterations associated with the injury, and cellular and molecular mechanisms by which these alterations are induced.

Altered Amniotic Fluid Levels of Hyaluronic Acid in Fetal Rats with Myelomeningocele: Understanding Spinal Cord Injury

Myelomeningocele (MMC) is a devastating congenital neural tube defect that results in the exposure of spinal cord to the intrauterine environment, leading to secondary spinal cord injury and severe impairment. Although the mechanisms underlying the secondary pathogenesis are clinically relevant, the exact cause of in utero-acquired spinal cord damage remains unclear. The objective of this study was to determine whether the hyaluronic acid (HA) concentration in amniotic fluid (AF) in the retinoic acid-induced model of MMC is different from that in normal controls and whether these differences could have an impact on the viscosity of AF. Our data shows that the concentration of HA in AF samples from fetuses with MMC (MMC-AF) and normal control samples (Norm-AF) were not significantly different at embryonic day 18 (E18) and E20. Thereafter, the HA concentration significantly increased in Norm-AF but not in MMC-AF. Compared with Norm-AF, the concentration of HA in MMC-AF and the viscosity of MMC-AF were significantly lower at E21. Agarose gel electrophoresis confirmed a significant reduction in the HA level of MMC-AF compared with Norm-AF at E21. No HA-degrading activity was detected in MMC-AF. In summary, we identified a deficiency in the AF level of HA and the viscosity of AF in fetal rats with MMC. These data are discussed in relation to a potential role the reduction in the AF viscosity due to the low level of HA may play in the exacerbating effects of mechanical trauma on spinal cord damage at the MMC lesion site.

Clusters of amniotic fluid cells and their associated early neuroepithelial markers in experimental myelomeningocele: Correlation with astrogliosis

Myelomeningocele (MMC) is the most common and severe disabling type of spina bifida resulting in the exposure of vulnerable spinal cord to the hostile intrauterine environment. In this study, we sought to examine the cellular content of fetal amniotic fluid (AF) in MMC and explore a correlation between these cells and pathological development of MMC. MMC was induced in fetal rats by exposing pregnant mothers to all-trans retinoic acid and AF samples were collected before term. Cells were isolated from AF samples and morphologically and phenotypically characterized in short-term cultures. In addition, the spinal cord injury in MMC fetuses was assessed by immunohistochemical examination of astrogliosis. We identified a population of cells from the AF of MMC fetuses (MMC-AF) that formed adherent clusters of tightly packed cells, which were absent from the AF of normal control fetuses (norm-AF). MMC-AF clusters contained cells co-expressing adherens junction associated proteins (ZO-1), N-cadherin and F-actin at sites of cell-cell contacts. In addition, they expressed markers of early neuroepithelial cells such as SOX-1 and Pax-6 along with other stem/progenitor cell markers such as SOX-2 and nestin. Subpopulations of cells in MMC-AF clusters also expressed more advanced differentiation markers such as doublecortin and GFAP. We found that the appearance of cluster forming cells in cultures from MMC-AF correlated with activation of astrogliosis associated with the spinal cord injury in MMC fetuses. In summary, we identified a neuroepithelial cell population in the AF of MMC fetuses that formed adherent clusters in culture and we characterized cellular markers of these cells. Our data suggests that the phase of the disease is a crucial factor in the emergence of these cells into the AF and that these cells may provide a new and important platform for studying the progression of MMC and development of improved strategies for the repair and diagnosis of MMC prenatally.

IDH1R132H in Neural Stem Cells: Differentiation Impaired by Increased Apoptosis

BACKGROUND

The high frequency of mutations in the isocitrate dehydrogenase 1 (IDH1) gene in diffuse gliomas indicates its importance in the process of gliomagenesis. These mutations result in loss of the normal function and acquisition of the neomorphic activity converting α-ketoglutarate to 2-hydroxyglutarate. This potential oncometabolite may induce the epigenetic changes, resulting in the deregulated expression of numerous genes, including those related to the differentiation process or cell survivability.

METHODS

Neural stem cells were derived from human induced pluripotent stem cells following embryoid body formation. Neural stem cells transduced with mutant IDH1R132H, empty vector, non-transduced and overexpressing IDH1WT controls were differentiated into astrocytes and neurons in culture. The neuronal and astrocytic differentiation was determined by morphology and expression of lineage specific markers (MAP2, Synapsin I and GFAP) as determined by real-time PCR and immunocytochemical staining. Apoptosis was evaluated by real-time observation of Caspase-3 activation and measurement of PARP cleavage by Western Blot.

RESULTS

Compared with control groups, cells expressing IDH1R132H retained an undifferentiated state and lacked morphological changes following stimulated differentiation. The significant inhibitory effect of IDH1R132H on neuronal and astrocytic differentiation was confirmed by immunocytochemical staining for markers of neural stem cells. Additionally, real-time PCR indicated suppressed expression of lineage markers. High percentage of apoptotic cells was detected within IDH1R132H-positive neural stem cells population and their derivatives, if compared to normal neural stem cells and their derivatives. The analysis of PARP and Caspase-3 activity confirmed apoptosis sensitivity in mutant protein-expressing neural cells.

CONCLUSIONS

Our study demonstrates that expression of IDH1R132H increases apoptosis susceptibility of neural stem cells and their derivatives. Robust apoptosis causes differentiation deficiency of IDH1R132H-expressing cells.

A Novel Dynamic Neonatal Blood-Brain Barrier on a Chip

Studies of neonatal neural pathologies and development of appropriate therapeutics are hampered by a lack of relevant in vitro models of neonatal blood-brain barrier (BBB). To establish such a model, we have developed a novel blood-brain barrier on a chip (B³C) that comprises a tissue compartment and vascular channels placed side-by-side mimicking the three-dimensional morphology, size and flow characteristics of microvessels in vivo. Rat brain endothelial cells (RBEC) isolated from neonatal rats were seeded in the vascular channels of B³C and maintained under shear flow conditions, while neonatal rat astrocytes were cultured under static conditions in the tissue compartment of the B³C. RBEC formed continuous endothelial lining with a central lumen along the length of the vascular channels of B³C and exhibited tight junction formation, as measured by the expression of zonula occludens-1 (ZO-1). ZO-1 expression significantly increased with shear flow in the vascular channels and with the presence of astrocyte conditioned medium (ACM) or astrocytes cultured in the tissue compartment. Consistent with in vivo BBB, B³C allowed endfeet-like astrocyte-endothelial cell interactions through a porous interface that separates the tissue compartment containing cultured astrocytes from the cultured RBEC in the vascular channels. The permeability of fluorescent 40 kDa dextran from vascular channel to the tissue compartment significantly decreased when RBEC were cultured in the presence of astrocytes or ACM (from 41.0±0.9 x 10⁻⁶ cm/s to 2.9±1.0 x 10⁻⁶ cm/s or 1.1±0.4 x 10⁻⁶ cm/s, respectively). Measurement of electrical resistance in B³C further supports that the addition of ACM significantly improves the barrier function in neonatal RBEC. Moreover, B³C exhibits significantly improved barrier characteristics compared to the transwell model and B³C permeability was not significantly different from the in vivo BBB permeability in neonatal rats. In summary, we developed a first dynamic in vitro neonatal BBB on a chip (B³C) that closely mimics the in vivo microenvironment, offers the flexibility of real time analysis, and is suitable for studies of BBB function as well as screening of novel therapeutics.

Micro-computed tomography assessment of vertebral column defects in retinoic acid-induced rat model of myelomeningocele

BACKGROUND

Myelomeningocele (MMC) is a common congenital malformation and the most severe form of spina bifida characterized by the protrusion of spinal cord and meninges through the spinal defect. Our objective was to improve the assessment of congenital vertebral defects in animal models of MMC using three-dimensional high resolution micro-computed tomography (micro-CT) imaging and quantitative digital analyses methods.

METHODS

Lumbosacral MMC was induced in fetal rats by exposure of pregnant mothers at embryonic day 10 (E10) to all-trans retinoic acid, and rats were examined at term (embryonic day 22). The axial skeleton was examined in an MMC model for the first time using ex vivo micro-CT at 10 μm voxel resolution to allow high resolution two-dimensional and three-dimensional characterization of anomalies in lumbosacral vertebrae, and quantitative assessment of distances between dorsal vertebral arches in lumbosacral regions in MMC rats, compared with normal controls.

RESULTS

We observed, in detail, skeletal defects in lumbosacral vertebra of MMC rats, including in the morphology of individual dorsal vertebral arches. Use of high resolution micro-CT has also enabled us to identify the delayed (nonfused) or absent ossification in vertebral bodies, increased fusion of adjacent lateral vertebral elements, and quantify the extent of dorsal arch widening. Distances between dorsal vertebral arches showed statistically significant increases from L5 through S4 in MMC rats, compared with normal controls.

CONCLUSION

High-resolution micro-CT combined with digital quantification methods is a powerful technique ideally suited for precise assessment of complex congenital skeletal abnormalities such as examined in this rodent model of MMC.

Targeted delivery of vascular endothelial growth factor improves stem cell therapy in a rat myocardial infarction model

Rebuilding of infarcted myocardium by mesenchymal stem cells (MSCs) has not been successful because of poor cell survival due in part to insufficient blood supply after myocardial infarction (MI). We hypothesize that targeted delivery of vascular endothelial growth factor (VEGF) to MI can help regenerate vasculature in support of MSC therapy in a rat model of MI. VEGF-encapsulated immunoliposomes targeting overexpressed P-selectin in MI tissue were infused by tail vein immediately after MI. One week later, MSCs were injected intramyocardially. The cardiac function loss was moderated slightly by targeted delivery of VEGF or MSC treatment. Targeted VEGF+MSC combination treatment showed highest attenuation in cardiac function loss. The combination treatment also increased blood vessel density (80%) and decreased collagen content in post-MI tissue (33%). Engraftment of MSCs in the combination treatment group was significantly increased and the engrafted cells contributed to the restoration of blood vessels.

FROM THE CLINICAL EDITOR

VEGF immunoliposomes targeting myocardial infarction tissue resulted in significantly higher attenuation of cardiac function loss when used in combination with mesenchymal stem cells. MSCs were previously found to have poor ability to restore cardiac tissue, likely as a result of poor blood supply in the affected areas. This new method counterbalances that weakness by the known effects of VEGF, as demonstrated in a rat model.

JCV agnoprotein-induced reduction in CXCL5/LIX secretion by oligodendrocytes is associated with activation of apoptotic signaling in neurons

An indispensable role for oligodendrocytes in the protection of axon function and promotion of neuronal survival is strongly supported by the finding of progressive neuron/axon degeneration in human neurological diseases that affect oligodendrocytes. Imaging and pathological studies of the CNS have shown the presence of neuroaxonal injury in progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the CNS, resulting from destruction of oligodendrocytes upon productive replication of the pathogenic neurotropic polyomavirus JC. Here, we examined the extracellular factors involved in communication between oligodendrocytes and neurons. Culturing cortical neurons with conditioned medium (CM) from rat CG4 oligodendrocytic cells that express the JCV agnoprotein showed that CXCL5/LIX, which is a chemokine closely related to the human CXCL5/ENA78 and CXCL6/GCP-2 chemokines, is essential for neuronal cell survival. We found that in CM from agnoprotein-producing CG-4 cells level of CXC5/LIX is decreased compared to control cells. We also demonstrated that a reduced expression of CXCL5/LIX by CG4 GFP-Agno cells triggered a cascade of signaling events in cortical neurons. Analysis of mitogen-activated protein kinases (MAPK) and glycogen synthase kinase (GSK3) pathways showed that they are involved in mechanisms of neuronal apoptosis in response to the depletion of CXCL5/LIX signaling. These data suggest that agnoprotein-induced dysregulation of chemokine production by oligodendrocytes may contribute to neuronal/axonal injury in the pathogenesis of PML lesions.

Bone marrow-derived mesenchymal stem cells undergo JCV T-antigen mediated transformation and generate tumors with neuroectodermal characteristics

There is now accumulating evidence showing that some tumors may arise from transformed stem cells. In this study we demonstrate that adult bone marrow- derived mesenchymal stem cells (MSCs) undergo neoplastic transformation induced by the human polyomavirus JCV, early protein, T-antigen, and are tumorigenic when transplanted into the flanks of Nude mice as compared to non-transformed MSCs. Histologically, the tumors are heterogeneous with mesenchymal and neural crest characteristics as evidenced by expression of the neural crest markers p75, SOX-10, and S-100, with populations of tumor cells exhibiting characteristics of primitive neuroectodermal cells. In addition, a subset of T-antigen positive tumor cells exhibit a high proliferation index as detected by Ki-67 labeling, and co-express CD133, a marker which is expressed on cancer stem cells. These results show that tumors with neuroectodermal characteristics may arise from transformation of MSCs, a globally accessible adult stem cell with multipotent differentiation capacity. In light of earlier reports on the association of JCV with a broad variety of human tumors, our data suggests that T-antigen transformation of adult stem cells with a multipotent capacity can serve as a possible common origin for some of these cancers, and offers a novel model for oncogenesis.

Binding and Internalization of Iron Oxide Nanoparticles Targeted to Nuclear Oncoprotein

A targeted nanoconjugate is being developed for non-invasive detection of gene expression in cells expressing the JC virus oncoprotein, T-antigen, which has been associated with medulloblastoma and other cancers. JC virus T-antigen localizes predominantly to the nucleus via a classical monopartite nuclear localization signal (NLS). An antibody fragment which recognizes JC virus T-antigen was attached to cross-linked dextran coated iron oxide nanoparticles. Radiolabeled conjugates were added to mouse medulloblastoma cells expressing the target T-antigen to test their ability to bind to tumor cells and be internalized by the cells. All conjugates containing targeting antibody bound to cells and were internalized, with increasing levels over time. There was no difference in cell binding or internalization among conjugates containing 2, 4, 6 or 8 antibody fragments per nanoparticle. Conjugates with only nonspecific antibody on nanoparticles, or unconjugated nonspecific antibody, had significantly lower total binding and internalization than conjugates with targeting antibody. Unconjugated targeting antibody had equivalent or lower cell uptake compared with targeted nanoparticle conjugates. Specificity of uptake was demonstrated by >80% reduction of nanoconjugate uptake in the presence of 100 fold excess of unconjugated antibody. The presence of a membrane translocation peptide (Tat) on the nanoparticles in addition to targeting antibody did not improve nanoconjugate internalization over the internalization caused by the antibody alone. This antibody nanoconjugate demonstrates feasibility of targeting a nuclear protein and suggests that a minimum number of antibody fragments per nanoparticle are sufficient for achieving binding specificity and efficient uptake into living cells.

A physiologically realistic in vitro model of microvascular networks

Existing microfluidic devices, e.g. parallel plate flow chambers, do not accurately depict the geometry of microvascular networks in vivo. We have developed a synthetic microvascular network (SMN) on a polydimethalsiloxane (PDMS) chip that can serve as an in vitro model of the bifurcations, tortuosities, and cross-sectional changes found in microvascular networks in vivo. Microvascular networks from a cremaster muscle were mapped using a modified Geographical Information System, and then used to manufacture the SMNs on a PDMS chip. The networks were cultured with bovine aortic endothelial cells (BAEC), which reached confluency 3-4 days after seeding. Propidium iodide staining indicated viable and healthy cells showing normal behavior in these networks. Anti-ICAM-1 conjugated 2-mum microspheres adhered to BAEC cells activated with TNF-alpha in significantly larger numbers compared to control IgG conjugated microspheres. This preferential adhesion suggests that cultured cells retain an intact cytokine response in the SMN. This microfluidic system can provide novel insight into characterization of drug delivery particles and dynamic flow conditions in microvascular networks.

Arrested neural and advanced mesenchymal differentiation of glioblastoma cells-comparative study with neural progenitors

BACKGROUND

Although features of variable differentiation in glioblastoma cell cultures have been reported, a comparative analysis of differentiation properties of normal neural GFAP positive progenitors, and those shown by glioblastoma cells, has not been performed.

METHODS

Following methods were used to compare glioblastoma cells and GFAP+NNP (NHA): exposure to neural differentiation medium, exposure to adipogenic and osteogenic medium, western blot analysis, immunocytochemistry, single cell assay, BrdU incorporation assay. To characterize glioblastoma cells EGFR amplification analysis, LOH/MSI analysis, and P53 nucleotide sequence analysis were performed.

RESULTS

In vitro differentiation of cancer cells derived from eight glioblastomas was compared with GFAP-positive normal neural progenitors (GFAP+NNP). Prior to exposure to differentiation medium, both types of cells showed similar multilineage phenotype (CD44+/MAP2+/GFAP+/Vimentin+/Beta III-tubulin+/Fibronectin+) and were positive for SOX-2 and Nestin. In contrast to GFAP+NNP, an efficient differentiation arrest was observed in all cell lines isolated from glioblastomas. Nevertheless, a subpopulation of cells isolated from four glioblastomas differentiated after serum-starvation with varying efficiency into derivatives indistinguishable from the neural derivatives of GFAP+NNP. Moreover, the cells derived from a majority of glioblastomas (7 out of 8), as well as GFAP+NNP, showed features of mesenchymal differentiation when exposed to medium with serum.

CONCLUSION

Our results showed that stable co-expression of multilineage markers by glioblastoma cells resulted from differentiation arrest. According to our data up to 95% of glioblastoma cells can present in vitro multilineage phenotype. The mesenchymal differentiation of glioblastoma cells is advanced and similar to mesenchymal differentiation of normal neural progenitors GFAP+NNP.

Successful elimination of non-neural cells and unachievable elimination of glial cells by means of commonly used cell culture manipulations during differentiation of GFAP and SOX2 positive neural progenitors (NHA) to neuronal cells

BACKGROUND

Although extensive research has been performed to control differentiation of neural stem cells - still, the response of those cells to diverse cell culture conditions often appears to be random and difficult to predict. To this end, we strived to obtain stabilized protocol of NHA cells differentiation - allowing for an increase in percentage yield of neuronal cells.

RESULTS

Uncommitted GFAP and SOX2 positive neural progenitors - so-called, Normal Human Astrocytes (NHA) were differentiated in different environmental conditions to: only neural cells consisted of neuronal [MAP2+, GFAP-] and glial [GFAP+, MAP2-] population, non-neural cells [CD44+, VIMENTIN+, FIBRONECTIN+, MAP2-, GFAP-, S100beta-, SOX2-], or mixture of neural and non-neural cells.In spite of successfully increasing the percentage yield of glial and neuronal vs. non-neural cells by means of environmental changes, we were not able to increase significantly the percentage of neuronal (GABA-ergic and catecholaminergic) over glial cells under several different cell culture testing conditions. Supplementing serum-free medium with several growth factors (SHH, bFGF, GDNF) did not radically change the ratio between neuronal and glial cells--i.e., 1,1:1 in medium without growth factors and 1,4:1 in medium with GDNF, respectively.

CONCLUSION

We suggest that biotechnologists attempting to enrich in vitro neural cell cultures in one type of cells - such as that required for transplantology purposes, should consider the strong limiting influence of intrinsic factors upon extracellular factors commonly tested in cell culture conditions.

Neuronal and astrocytic cells, obtained after differentiation of human neural GFAP-positive progenitors, present heterogeneous expression of PrPc

PrP(c) is a cellular isoform of the prion protein with an unknown normal function. One of the putative physiological roles of this protein is its involvement in cell differentiation. Recently, in vitro and in vivo studies showed that GFAP-positive cells have characteristics of stem/progenitor cells that generate neurons and glia. We used an in vitro model of human neurogenesis from GFAP-positive progenitor cells to study the expression of PrP(c) during neural differentiation. Semi-quantitative multiplex-PCR assay and Western blot analysis revealed a significant increase of PRNP expression level in differentiated cells compared to undifferentiated cell population. As determined by immunocytochemistry followed by a quantitative image analysis, the PrP(c) level increased significantly in neuronal cells and did not increase significantly in glial cells. Of note, glial and neuronal cells showed a very large heterogeneity of PrP(c) expression. Our results provide the basis for studying the role of PrP(c) in cell differentiation and neurogenesis from human GFAP-positive progenitor cells.

A population of human brain parenchymal cells express markers of glial, neuronal and early neural cells and differentiate into cells of neuronal and glial lineages

Glial fibrillary acidic protein (GFAP)-positive cells derived from the neurogenic areas of the brain can be stem/progenitor cells and give rise to new neurons in vitro and in vivo. We report here that a population of GFAP-positive cells derived from fetal human brain parenchyma coexpress markers of early neural and neuronal cells, and have neural progenitor cell characteristics. We used a monolayer culture system to expend and differentiate these cells. During the initial proliferative phase, all cells expressed GFAP, nestin and low levels of betaIII-tubulin. When these cells were cultured in serum and then basic fibroblast growth factor, they generated two distinct progenies: (i) betaIII-tubulin- and nestin-positive cells and (ii) GFAP- and nestin-positive cells. These cells, when subsequently cultured in serum-free media without growth factors, ceased to proliferate and differentiated into two major neural cell classes, neurons and glia. In the cells of neuronal lineage, nestin expression was down-regulated and betaIII-tubulin expression became robust. Cells of glial lineage differentiated by down-regulating nestin expression and up-regulating GFAP expression. These data suggest that populations of parenchymal brain cells, initially expressing both glial and neuronal markers, are capable of differentiating into single neuronal and glial lineages through asymmetric regulation of gene expression in these cells, rather than acquiring markers through differentiation.

Human fibroblast-derived cell lines have characteristics of embryonic stem cells and cells of neuro-ectodermal origin

Fibroblasts are the most ubiquitous cells in complex organisms. They are the main cells of stromal tissue and play an important role in repair and healing of damaged organs. Here we report new data-initially serendipitous findings-that fibroblast-derived cell line (human fetal lung derived cells, MRC-5) have the morphology, growth rate and gene expression pattern characteristic of embryonic stem cells and cells of neuro-ectodermal origin. We have developed a serum-free culture system to maintain these cells in proliferative state. We discovered that, at proliferative state, these cells express transcription factors of pluripotent cells, OCT-3/4 and REX-1, and embryonic cell surface antigens SSEA-1, SSEA-3, and SSEA-4, as well as TRA-1-60 and TRA-1-81. In addition to embryonic cell markers, the fibroblasts expressed neuroectodermal genes: Musashi-1, nestin, medium neurofilament, and beta-III tubulin. RT-PCR data revealed that mesencephalic transcription factors, Nurr-1 and PTX-3, were also expressed in MRC-5 cells, and that these cells could be induced to express tyrosine hydroxylase (TH). Expression of TH followed down-regulation of genes associated with cell proliferation, OCT-3/4, REX-1, and beta-catenin. These data indicate that the cells commonly known as fibroblasts have some of the characteristics of stem cells, and can be induced to become neuroectodermal cells and perhaps even mature neurons.

Oncogenic potential of human neurotropic virus: laboratory and clinical observations

Cancer is a multi-step disease involving a series of genetic alterations that result in the loss of control of cell proliferation and differentiation. Such genetic alterations could emerge from the activation of oncogenes and the loss or malfunctioning of tumor suppressor gene activity. Our understanding of cancer has greatly increased through the use of DNA tumor viruses and their transforming proteins as a biological tool to decipher a cascade of events that lead to deregulation of cell proliferation and subsequent tumor formation. For the past ten years our laboratory has focused on the molecular biology of the human neurotropic papovavirus, JCV. This virus causes progressive multifocal leukoencephalopathy, a fatal neurodegenerative disease of the central nervous system in immunocompromised patients. JCV is a common human virus that infects more than 80% of humans but does not induce any obvious clinical symptoms. The increased incidence of acquired immune deficiency syndrome and the use of immunosuppressive chemotherapy have dramatically raised the incidence of PML. The coincidental occurrence of malignant astrocytes and oligodendrocytes in PML patients, coupled with the induction of glioblastoma in JCV-infected nonhuman primates, provides intriguing speculation on the association between JCV and CNS malignancies. In this report we discuss clinical data and laboratory observations pointing to the direct involvement of JCV in cancer.

Association of SV40 with human tumours

SV40 was discovered as a contaminant of poliovirus vaccines that were inadvertently administered to millions of people in Europe and the United States between 1955 and 1963. Shortly afterwards, SV40 was proven to be oncogenic in rodents and capable of transforming human and animal cells in vitro. The possibility that SV40 might cause tumours in humans thus became a subject of scientific and public interest and scrutiny. However, largely due to a lack of significant epidemiological evidence, interest in assessing SV40's potential carcinogenic role in humans diminished. Recently, many laboratories have reported the presence of SV40-like DNA in a high proportion of human mesotheliomas, ependymomas and osteosarcoma (the three main types of tumours caused by virus in hamsters), renewing the question whether SV40 might be a human tumour virus. Molecular data from these studies are reviewed to re-evaluate the potential role of SV40 as a human carcinogen.

Reactivation of human neurotropic JC virus expressing oncogenic protein in a recurrent glioblastoma multiforme

Examination of the primary tumor of glioblastoma multiforme and its recurrence for their association with JC virus revealed that, while the viral genome is present in both initial and recurrent tumors, expression of the viral oncoprotein T-antigen occurs only in the recurrent tumor cells. Accordingly, the level of inducible cellular transcription factors, including the p65 subunit of NF-kappaB and YB-1, which have the ability to stimulate JCV gene expression, was found to be higher in the recurrent tumor cells. These observations suggest that induction of the regulatory factors after resection of the primary tumor may have reactivated JC virus gene expression and led to redevelopment of the tumor in brain.

Identification of a novel p53 mutation in JCV-induced mouse medulloblastoma

Medulloblastoma, a malignant invasive tumor of the cerebellum, is one of the most common neoplasms of the nervous system in children. Utilization of the human neurotropic virus JC virus (JCV) early gene T-antigen allowed the development of a transgenic animal that models human medulloblastoma. Here we describe the characterization of two distinct populations of cells derived from the JCV-induced mouse medulloblastoma. Results from immunohistochemical and biochemical studies revealed the expression of T-antigen in some but not all tumor cells. In T-antigen-producing cells, T-antigen was found in association with wild-type p53 and pRb, two tumor suppressors that control cell growth and differentiation. In cells that lack expression of T-antigen, a novel mutant p53 with a deletion between residues 35 and 123 was detected. Morphological differences were observed between the two populations of cells, though there was no significant difference in their growth rates. However, subcutaneous transplantation of the T-antigen-positive, but not T-antigen-negative, cells resulted in the development of massive tumors in experimental animals. In light of earlier reports on the association of JCV with human medulloblastoma, the mouse cell lines described in this study may provide a valuable tool for deciphering the pathways involved in the formation and progression of medulloblastoma.

Detection of human neurotropic JC virus DNA sequence and expression of the viral oncogenic protein in pediatric medulloblastomas

Medulloblastoma represents greater than 25% of childhood intracranial neoplasms and is considered a highly malignant tumor. This tumor, which arises predominantly in the cerebellar vermis, preferentially affects children between the ages of 5 and 15. Although the etiology of medulloblastomas in humans remains unknown, results from several experiments have indicated that the human neurotropic JC virus (JCV) is able to induce cerebellar neoplasms in rodents that exhibit a phenotype similar to that of human medulloblastomas. JCV is a polyomavirus that is widespread in the human population, with infection occurring most frequently in early childhood. In this study, we have examined the possible association of JCV with human medulloblastomas. By using PCR techniques we demonstrate that 11 of 23 samples of tumor tissue contain DNA sequences corresponding to three different regions of the JCV genome. More importantly, we demonstrate the presence of DNA sequences encoding the N- and C-terminal regions of the JCV oncogenic protein, T antigen, in 11 of 23 samples and the production of T antigen in the nuclei of 4 samples of tumor tissue. These observations provide evidence for a possible association of JCV with human medulloblastomas.

Human neurotropic JC virus early protein deregulates glial cell cycle pathway and impairs cell differentiation

Progressive multifocal leukoencephalopathy (PML), a human demyelinating disease of the central nervous system (CNS), is induced upon replication of the human neurotropic virus, JCV, in glial cells. Similar to other polyomaviruses, replication of JCV is initiated and orchestrated by the viral early protein, T-antigen, and results in the cytolytic destruction of oligodendrocytes, the subset of glial cells responsible for myelin production, and the appearance of bizarre astrocytic glial cells in affected individuals. Earlier results from studies in transgenic animals have suggested that in the absence of viral replication, expression of JCV T-antigen induces pathology consistent with hypomyelination of the brain. These observations suggest that JCV T-antigen has the ability to deregulate oligodendrocyte and perhaps astrocyte function in the CNS. Here we demonstrate that expression of JCV T-antigen in the bipotential glial cell line, CG-4, severely affects the ability of these cells to differentiate toward oligodendrocyte and astrocyte lineages as evidenced by their distinct morphological changes. Examination of the activity of cell cycle regulatory proteins including cyclins and their associated kinases reveals that in the absence of T-antigen, differentiation of CG-4 cells toward astrocytes and oligodendrocytes is accompanied by a decline in cyclin E, cdk2, cyclin A, and cyclin B activity. In contrast, cdc2 activity increased upon CG-4 differentiation. In T-antigen-producing cells, distinct variations in the activity of several cyclins was observed. For example, while the activity of cdk2 and cyclin E was enhanced in T-antigen expressing astrocytes compared to their levels in control cells, the activity of cdc2 was decreased in this cell type. In oligodendrocytes, expression of T-antigen decreased the activity of several cyclins and cdks including cyclin E and cdc2. On the other hand, the level of expression and activity of cyclin A was increased. Thus, it is evident that JCV T-antigen deregulates several important cell cycle regulators during CG-4 differentiation, and these alterations may contribute to the process of cell growth and differentiation in glial cells. The importance of our findings with regard to the neuropathogenesis of PML is discussed.

Human ubiquitous JCV(CY) T-antigen gene induces brain tumors in experimental animals

JCV is a papovavirus which is widespread in the human population. The prototype Mad-1 variant of JCV induces a fatal demyelinating disease of the central nervous system (CNS) called Progressive Multifocal Leukoencephalopathy (PML) in immunosuppressed individuals. The unique tropism of JCV (Mad-1) to the CNS is attributed to the tissue-specific regulation of the viral early promoter which is responsible for the production of the viral regulatory protein, T-antigen. The archetype form of this virus, JCV(CY), which has been repeatedly isolated from the urine of PML and non-PML individuals, is distinct from JCV(Mad-1) in the structural organization of the regulatory sequence. To characterize the tissue specific expression of JCV(CY) and to investigate its potential in inducing disease, transgenic mice containing the early region of JCV(CY) were generated. Some of these mice between 9-13 months of age exhibited signs of illness as manifested by paralysis of rear limbs, hunched posture, and poor grooming. Neuropathological examination indicated no sign of hypomyelination of the brain, but surprisingly, revealed the presence of primitive tumors originating from the cerebellum and the surrounding brain stem. The tumor masses also infiltrated the surrounding tissue. Results from RNA and protein studies revealed a high level of T-antigen mRNA expression in hindbrains of clinically normal and affected transgenic mice. However, higher levels of T-antigen RNA and protein were detected in brains of the animals exhibiting severe illness. The close resemblance of JCV(CY) induced tumor in transgenic mice to the human medulloblastoma/primitive neuroectodermal tumor (PNETs) in location, histologic appearance, and expression of marker proteins strongly suggests the utility of this novel animal model for the study of human brain tumors.

Oncogenic potential of human neurotropic papovavirus, JCV, in CNS

The human polyomavirus, JCV, is the causative agent of Progressive Multifocal Leukoencephalopathy (PML), a fatal human demyelinating disease. PML results from the cytolytic destruction of oligodendrocytes, the myelin-producing cells of the nervous system. JCV has also been shown to be tumorigenic in several animal models. Transgenic mice expressing the JCV early protein, T-antigen, develop poorly differentiated neural crest origin tumours. Intracerebral inoculation of JCV into newborn hamsters induces medulloblastomas, astrocytomas, and primitive neuroectodermal tumours. Further, inoculation of the virus into the brains of non-human primates, owl and squirrel monkeys, results in astrocytomas and glioblastoma multiforme. Several case reports have associated JCV with human CNS tumours in patients with concomitant PML, and one such report has detected JCV in a glial tumour in the absence of PML. The induction of neural origin tumours by JCV has been studied in transgenic mice harbouring the early genome of the virus. Alterations in the level and function of tumour suppressor proteins p53 and Rb, as well as associated cell cycle regulators, have been detected in tumour tissue from JCV T-antigen transgenic mice. Possible mechanisms by which JCV may exert its oncogenic potential by alteration of cellular growth control pathways in both humans and experimental animals are discussed.

A multi-institutional study confirms the presence and expression of simian virus 40 in human malignant mesotheliomas

Exposure to the carcinogen asbestos is a major factor in the development of malignant mesothelioma. However, not all mesotheliomas are associated with asbestos exposure, and only a small minority of people exposed to asbestos develop mesothelioma. Therefore, the identification of the cofactors that render certain individuals more susceptible to asbestos or that cause mesothelioma in people not exposed to asbestos has been a major priority of the International Mesothelioma Interest Group. The possible association of SV40 with mesothelioma was recently discussed in a special session at the Fourth International Mesothelioma Interest Group Conference, and it was decided to conduct a multi-institutional study to independently verify the presence of this tumor virus in mesotheliomas. We report the results of this investigation: (a) DNA and protein analyses revealed SV40 sequences and SV40 large T antigen expression in 10 of 12 mesotheliomas tested (83%); and (b) electron microscopy demonstrated variable amounts of asbestos fibers in 5 (71%) of 7 corresponding lung tissues available for analysis. Our results demonstrate that SV40 DNA is frequently present and expressed in mesotheliomas in the United States. Because our data demonstrate that some patients test positive for both SV40 and asbestos, the possibility that these two carcinogens interact should be investigated in future studies.

MyEF-3, a developmentally controlled brain-derived nuclear protein which specifically interacts with myelin basic protein proximal regulatory sequences

Myelin basic protein (MBP) gene contains the upstream regulatory sequence that confers cell type- and stage-specific transcription to MBP expression in oligodendrocytes during brain development. The MB1 regulatory motif located between -14 to -50 with respect to transcription start site binds to a brain derived nuclear protein and plays an important role in transcriptional activation of the MBP promoter in transfection assay. Here, we report the isolation of a recombinant cDNA clone, termed myelin expression factor-3, (MyEF-3) from a mouse brain expression library that encodes a novel protein which interacts with the MBP MB1 domain. Computer assisted evaluations of the MyEF-3 sequence revealed several interesting features including four sites for phosphorylation by casein kinase II, a transmembrane domain at the N-terminus, a nuclear localization signal and a Zinc finger domain at the carboxyl terminal. Results from Western and band shift assays indicate that MyEF-3 binds efficiently to double-stranded MB1 as well as the single-stranded non-coding strand of MB1. The use of short DNA fragments encompassing the nucleotide base substitutions across the MB1 domain in competition band shift assay revealed that the ten nucleotide sequence, 5'-GCCTGTCTTT-3' is important for binding of MyEF-3 to DNA. Results from Northern blot studies demonstrate that expression of MyEF-3 is restricted to brain and developmentally regulated during brain maturation. The biological importance of MyEF-3 in the cell type- and stage-specific expression of MBP during brain development is discussed.

Role of cell cycle regulators in tumor formation in transgenic mice expressing the human neurotropic virus, JCV, early protein

Transgenic mice harboring the early genome from the human neurotropic JC virus, JCV, develop massive abdominal tumors of neural crest origin during 6-8 months after birth and succumb to death a few weeks later. The viral early protein, T-antigen, which possesses the ability to transform cells of neural origin, is highly expressed in the tumor cells. Immunoblot analysis of protein extract from tumor tissue shows high level expression of the tumor suppressor protein, p53, in complex with T-antigen. Expression of p21, a downstream target for p53, which controls cell cycle progression by regulating the activity of cyclins and their associated kinases during the G1 phase, is extremely low in the tumor cells. Whereas the level of expression and activity of cyclin D1 and its associated kinase, cdk6, was modest in tumor cells, both cyclin A and E, and their kinase partners, cdk2 and cdk4, were highly expressed and exhibited significant kinase activity. The retinoblastoma gene product, pRb, which upon phosphorylation by cyclins:cdk induces rapid cell proliferation, was found in the phosphorylated state in tumor cell extracts, and was detected in association with JCV T-antigen. The transcription factor, E2F-1, which dissociates from the pRb-E2F-1 complex and stimulates S phase-specific genes upon phosphorylation of pRb and/or complexation of pRb with the viral transforming protein, was highly expressed in tumor cells. Accordingly, high level expression of the E2F-1-responsive gene, proliferating cell nuclear antigen (PCNA), was detected in the tumor cells. These observations suggest a potential regulating pathway that, upon expression of JCV T-antigen, induces formation and progression of tumors of neural origin in a whole animal system.