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Biomedical subjects

Vittorio Gallo

Publications and source records attributed to Vittorio Gallo.

At least 19 recordsLinked to original sources
PubMed2007

Astrogliosis in EAE spinal cord: derivation from radial glia, and relationships to oligodendroglia.

A prominent feature of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) is the accumulation of enlarged, multipolar glial fibrillary acidic protein (GFAP) and brain lipid binding protein (BLBP) immunoreactive astroglia within and at the margins of the inflammatory demyelinative lesions. Whether this astrogliosis is due to both astroglial hyperplasia and hypertrophy or solely to astroglial hypertrophy is controversial. We now report that coincident with the first appearance of inflammation and clinical deficits in mice with myelin oligodendrocyte glycoprotein peptide (MOG peptide)-induced EAE, the radially oriented, bipolar, GFAP, and BLBP positive cells (adult radial glia) present in normal spinal cord white matter undergo mitosis and phenotypic transformation to hypertrophic astroglia. To facilitate visualization of relationships between these hypertrophic astroglia and dying and regenerating oligodendroglia, we used mice that express enhanced green fluorescent protein (EGFP) in cells of the oligodendroglial lineage. During the first week after onset of illness, markedly swollen EGFP+ cells without processes were seen within lesions, whereas EGFP+ cells that expressed immunoreactive cleaved caspase-3 were uncommon. These observations support the hypothesis that necrosis contributes to oligodendroglial loss early in the course of EAE. Later in the illness, EGFP+ cells accumulated amongst hypertrophic astroglia at the margins of the lesions, while the lesions themselves remained depleted of oligodendroglia, suggesting that migration of oligodendroglial lineage cells into the lesions was retarded by the intense perilesional gliosis.

Animals↗
PubMed2006

Identification of Sox17 as a transcription factor that regulates oligodendrocyte development.

Microarray analysis of oligodendrocyte lineage cells purified by fluorescence-activated cell sorting (FACS) from 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP)-enhanced green fluorescent protein (EGFP) transgenic mice revealed Sox17 (SRY-box containing gene 17) gene expression to be coordinately regulated with that of four myelin genes during postnatal development. In CNP-EGFP-positive (CNP-EGFP+) cells, Sox17 mRNA and protein levels transiently increased between postnatal days 2 and 15, with white matter O4+ preoligodendrocytes expressing greater Sox17 levels than Nkx2.2+ (NK2 transcription factor related, locus 2) NG2+, or GalC+ (galactocerebroside) cells. In spinal cord, Sox17 protein expression was undetectable in the primary motor neuron domain between embryonic days 12.5 and 15.5 but was evident in Nkx2.2+ and CC1+ cells. In cultured oligodendrocyte progenitor cells (OPCs), Sox17 levels were maximal in O4+ cells and peaked during the phenotypic conversion from bipolar to multipolar. Parallel increases in Sox17 and p27 occurred before MBP protein expression, and Sox17 upregulation was prevented by conditions inhibiting differentiation. Sox17 downregulation with small interfering RNAs increased OPC proliferation and decreased lineage progression after mitogen withdrawal, whereas Sox17 overexpression in the presence of mitogen had opposite effects. Sox17 overexpression enhanced myelin gene expression in OPCs and directly stimulated MBP gene promoter activity. These findings support important roles for Sox17 in controlling both oligodendrocyte progenitor cell cycle exit and differentiation.

Animals↗
PubMed2006

Inflammation in white matter: clinical and pathophysiological aspects.

While the central nervous system (CNS) is generally thought of as an immunopriviledged site, immune-mediated CNS white matter damage can occur in both the perinatal period and in adults, and can result in severe and persistent neurological deficits. Periventricular leukomalacia (PVL) is an inflammatory white matter disease of premature infants that frequently results in cerebral palsy (CP). Clinical and experimental studies show that both hypoxic/ischemic and innate immune mechanisms contribute to the destruction of immature oligodendroglia and of axons in the deep cerebral white matter in PVL. No data are yet available as to whether there is any genetic predisposition to PVL or to its neurological sequelae. Multiple sclerosis (MS) is an inflammatory white matter disease that often begins in young adulthood, causes multifocal destruction of mature oligodendroglia and of axons, and eventually leads to substantial cumulative neurological disability. Certain genetic polymorphisms contribute to susceptibility to MS, and adaptive immune responses to myelin-associated self antigens, or to exogenous antigens that mimic these self antigens, play a central role in the pathophysiology of this disease.

Axons↗
PubMed2006

The Yin and Yang of cell cycle progression and differentiation in the oligodendroglial lineage.

In white matter disorders such as leukodystrophies (LD), periventricular leucomalacia (PVL), or multiple sclerosis (MS), the hypomyelination or the remyelination failure by oligodendrocyte progenitor cells involves errors in the sequence of events that normally occur during development when progenitors proliferate, migrate through the white matter, contact the axon, and differentiate into myelin-forming oligodendrocytes. Multiple mechanisms underlie the eventual progressive deterioration that typifies the natural history of developmental demyelination in LD and PVL and of adult-onset demyelination in MS. Over the past few years, pathophysiological studies have mostly focused on seeking abnormalities that impede oligodendroglial maturation at the level of migration, myelination, and survival. In contrast, there has been a strikingly lower interest for early proliferative and differentiation events that are likely to be equally critical for white matter development and myelin repair. This review highlights the Yin and Yang principles of interactions between intrinsic factors that coordinately regulate progenitor cell division and the onset of differentiation, i.e. the initial steps of oligodendrocyte lineage progression that are obviously crucial in health and diseases.

Adult↗
PubMed2005

Galactocerebrosidase-deficient oligodendrocytes maintain stable central myelin by exogenous replacement of the missing enzyme in mice.

Globoid cell leukodystrophy (GLD) is a lysosomal storage disease caused by genetic deficiency of galactocerebrosidase (GALC) activity. Failure in catalyzing the degradation of its major substrate, galactocerebroside, in oligodendrocytes (OLs) and Schwann cells leads to death of these myelinating cells, progressive demyelination, and early demise of GLD patients. Transplantation of bone marrow cells and umbilical cord blood have been attempted as a means of enzyme replacement and have shown limited success. It remains unknown whether or how these therapies support survival of GALC-deficient OLs and myelin maintenance. We report that, upon transplantation, GALC-deficient OLs from the twitcher mouse, a model of GLD, achieved widespread myelination in the brain and spinal cord of the myelin-deficient shiverer mouse, which was preserved for the life of the host. GALC immunohistochemistry showed direct evidence for GALC transfer from the shiverer environment to the engrafted mutant OLs in vivo. These findings suggest that the mutant OLs can internalize exogenous GALC and maintain stable myelin, demonstrating that exogenous enzyme replacement will be a key strategy in the therapy of GLD.

Animals↗
PubMed2005

Overexpression of the epidermal growth factor receptor confers migratory properties to nonmigratory postnatal neural progenitors.

Approaches to successful cell transplantation therapies for the injured brain involve selecting the appropriate neural progenitor type and optimizing the efficiency of the cell engraftment. Here we show that epidermal growth factor receptor (EGFR) expression enhances postnatal neural progenitor migration in vitro and in vivo. Migratory NG2-expressing (NG2+) progenitor cells of the postnatal subventricular zone (SVZ) express higher EGFR levels than nonmigratory, cortical NG2+ cells. The higher endogenous EGFR expression in SVZ NG2+ cells is causally related with their migratory potential in vitro as well as in vivo after cell engraftment. EGFR overexpression in cortical NG2+ cells by transient transfection converted these cells to a migratory phenotype in vitro and in vivo. Finally, cortical NG2+ cells purified from a transgenic mouse in which the EGFR is overexpressed under the CNP promoter exhibited enhanced migratory capability. These findings reveal a new role for EGFR in the postnatal brain and open new avenues to optimize cell engraftment for brain repair.

Animals↗
PubMed2005

Interferon-gamma inhibits cell cycle exit in differentiating oligodendrocyte progenitor cells.

The developmental processes of the oligodendrocyte progenitor cell (OPC) lineage that are targeted by interferon-gamma (IFN-gamma) were studied in primary rat OPC cultures. Under conditions of thyroid hormone-mediated oligodendrocyte differentiation, IFN-gamma produced a dose-dependent apoptotic response in OPCs. The lowest dose tested (15 ng/ml or 75 U/ml) was nonapoptotic, but activated detectable STAT1 DNA-binding. At this dose, IFN-gamma reduced the percentage of mature O1+ cells and increased the percentage of immature A2B5+ OPCs. This was observed without significant change in total cell number and cytotoxicity, and was accompanied by an increase in BrdU-labeled A2B5+ and O4+ cells. FACS analysis confirmed a lack of apoptotic sub-G1 cells and revealed a greater percentage of S- and G2/M-phase OPCs with IFN-gamma treatment. Dual immunostaining with Ki-67 and Olig2 showed a smaller percentage of Olig2+ cells in G0 phase in IFN-gamma-treated OPCs, indicating loss of G1 control. Instead, increased levels and phosphorylation of the checkpoint protein p34cdc2 by IFN- suggested increased partial arrest in G2. IFN-gamma not only sustained expression of PCNA and the G1-S regulators retinoblastoma protein, cyclin D1, cyclin E, and cdk2, but also decreased p27 levels. In addition to changes in cell proliferation and differentiation, IFN-gamma attenuated myelin basic protein (MBP) expression significantly, which was associated with decreased expression of both MBP and Sox10 RNAs. These findings indicate that IFN-gamma not only maintains cell cycle activity that could predispose OPCs to apoptosis, but also overrides G1-G0 signals leading to thyroid hormone-mediated terminal differentiation and myelin gene expression.

Animals↗
PubMed2005

Downregulation of platelet-derived growth factor-alpha receptor-mediated tyrosine kinase activity as a cellular mechanism for K+-channel regulation during oligodendrocyte development in situ.

Oligodendrocyte maturation has been defined based on expression of developmentally regulated antigens. However, transitions at early stages of the lineage have not been functionally characterized fully in situ. Combining 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP)-promoter driven enhanced green fluorescent protein expression and whole-cell capacitance measurements permitted a reliable distinction between subcortical white matter NG2+ oligodendrocyte progenitors (OPs) and O4+ preoligodendrocytes (pre-OLs) in situ. We focused on K+ channels because their expression has been associated previously with the proliferation and differentiation potential of OPs. Using whole-cell patch clamp, we observed a downregulation of the delayed outward-rectifying current (IKDR) between the NG2+ and O4+ stages but no significant changes in transient K+-channel current (IKA) amplitude. Tyrosine kinase inhibition in NG2+ cells reduced IKDR amplitude with no effect on IKA, which mimicked the endogenous changes observed between OPs and pre-OLs. Tyrosine kinase inhibition also reduced the proliferative capacity of NG2+ OPs in slice cultures. Conversely, acute platelet-derived growth factor receptor-alpha (PDGFR-alpha) activation caused an increase of IKDR in NG2+ but not in O4+ cells. Consistent with this finding, PDGFR-alpha immunoreactivity was confined to NG2+ cells with undetectable levels in O4+ cells, suggesting that PDGFR-alpha signaling is absent in pre-OLs in situ. Importantly, the PDGF-induced increase of IKDR in NG2+ cells was prevented by tyrosine kinase inhibition. Together, these data indicate that PDGFR-alpha and tyrosine kinase activity act via a common pathway that influences functional expression of K+ channels and proliferative capacity of OPs in situ.

Animals↗
PubMed2004

Postnatal neurogenesis and gliogenesis in the olfactory bulb from NG2-expressing progenitors of the subventricular zone.

We used a 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP)-enhanced green fluorescent protein (EGFP) transgenic mouse to study postnatal subventricular zone (SVZ) progenitor fate, with a focus on the olfactory bulb (OB). The postnatal OB of the CNP-EGFP mouse contained EGFP+ interneurons and oligodendrocytes. In the anterior SVZ, the majority of EGFP+ progenitors were NG2+. These NG2+/EGFP+ progenitors expressed the OB interneuron marker Er81, the neuroblast markers doublecortin (DC) and Distalless-related homeobox (DLX), or the oligodendrocyte progenitor marker Nkx2.2. In the rostral migratory stream (RMS), EGFP+ cells displayed a migrating phenotype. A fraction of these cells were either NG2-/Er81+/DC+/DLX+ or NG2+/Nkx2.2+. DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) injection into the lateral ventricle (LV) of early postnatal mice demonstrated that NG2+/EGFP+ progenitors migrate from the SVZ through the RMS into the OB. Moreover, fluorescence-activated cell-sorting-purified NG2+/CNP-EGFP+ or NG2+/beta-actin-enhanced yellow fluorescent protein-positive (EYFP+) progenitors transplanted into the early postnatal LV displayed extensive rostral and caudal migration. EYFP+ or EGFP+ graft-derived cells within the RMS were DLX+/Er81+ or Nkx2.2+, migrated to the OB, and differentiated to interneurons and oligodendrocytes. In the subcortical white matter (SCWM), grafted cells differentiated to either oligodendrocytes or astrocytes. Transplantation of NG2+/EYFP+ progenitors selectively purified from the SVZ showed that these cells were migratory and generated glia and neurons in the OB, hippocampus, and striatum. In contrast, cortical, OB, or cerebellar NG2+ cells had a very limited migratory potential and gave rise to glia in the SCWM and striatum. Our findings indicate region-specific differences between NG2+ progenitor cells and show that NG2+ cells can migrate throughout the RMS and contribute to both gliogenesis and neurogenesis in the postnatal OB.

Animals↗
PubMed2004

Synaptic and extrasynaptic neurotransmitter receptors in glial precursors' quest for identity.

It is widely established that neurotransmitter receptors are expressed in non-neuronal cells, and particularly in neural progenitor cells in the postnatal central nervous system. The functional role of these receptors during development is unclear, but it needs to be revisited now that cells previously considered restricted to glial lineages have been shown to generate neurons. The present review integrates recent advances, to shed new light on how neurotransmitter receptors may, alternatively, serve as excitable mediators of neuron-glia and neuron-neuroblast interactions.

Animals↗
PubMed2004

Metallothionein I and II mitigate age-dependent secondary brain injury.

Both the immediate insult and delayed apoptosis contribute to functional deficits after brain injury. Secondary, delayed apoptotic death is more rapid in immature than in adult CNS neurons, suggesting the presence of age-dependent protective factors. To understand the molecular pathobiology of secondary injury in the context of brain development, we identified changes in expression of oxidative stress response genes during postnatal development and target deprivation-induced neurodegeneration. The antioxidants metallothionein I and II (MT I/II) were increased markedly in the thalamus of adult C57BL/6 mice compared to mice <15 days old. Target deprivation generates reactive oxygen species that mediate neuronal apoptosis in the central nervous system; thus the more rapid apoptosis observed in the immature brain might be due to lower levels of MT I/II. We tested this hypothesis by documenting neuronal loss after target-deprivation injury. MT I/II-deficient adult mice experienced greater thalamic neuron loss at 96 hr after cortical injury compared to that in controls (80 +/- 2% vs. 57 +/- 4%, P < 0.01), but not greater overall neuronal loss (84 +/- 4% vs. 79 +/- 3%, MT I/II-deficient vs. controls). Ten-day-old MT I/II-deficient mice, however, experienced both faster onset of secondary neuronal death (30 vs. 48 hr) and greater overall neuronal loss (88 +/- 2% vs. 69 +/- 4%, P = 0.02). MT I/II are thus inhibitors of age-dependent secondary brain injury, and the low levels of MT I/II in immature brains explains, in part, the enhanced susceptibility of the young brain to neuronal loss after injury. These findings have implications for the development of age-specific therapeutic strategies to enhance recovery after brain injury.

Age Factors↗
PubMed2004

Determining the fetal inflammatory response in an experimental model of intrauterine inflammation in rats.

Intrauterine infection is a risk factor for developmental brain injuries in childhood. A variety of cytokines known to be toxic to developing brain cells have been isolated from mothers or children at risk for developmental disabilities, and these cytokines have been proposed as mediators of these injuries. We have developed a model of intrauterine inflammation that damages the developing white matter and we now hypothesize that selected cytokines are increased after our experimental inflammatory stimulus. Timed-pregnant Fischer 344 and Lewis rats were injected with 0.1 mg/kg of lipopolysaccharide (LPS) into the cervix at E15. Tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-6, and IL-10 were measured in homogenates of fetal brain and placenta at serial time periods within the first 24 h after the inflammatory stimulus. TNF-alpha was increased 20-fold in the placenta and more than 5-fold in the fetal brain after the stimulus. IFN-gamma was only increased within the fetal brain (20-fold) and IL-6 was only increased in the placenta (10-fold). IL-10 was mildly increased in the placenta and was decreased slightly in the fetal brain. Our observations show that an intrauterine inflammatory stimulus can cause large increases in Th1 cytokines within the fetal brain. The placenta can produce selected cytokines but fails to produce IFN-gamma, suggesting that the fetal immune system produces this cytokine in response to our stimulus. By studying placental and brain cytokine responses in models such as ours, the mechanisms responsible for the damage to developing white matter can be determined.

Animals↗
PubMed2004

NG2-expressing cells in the subventricular zone are type C-like cells and contribute to interneuron generation in the postnatal hippocampus.

The subventricular zone (SVZ) is a source of neural progenitors throughout brain development. The identification and purification of these progenitors and the analysis of their lineage potential are fundamental issues for future brain repair therapies. We demonstrate that early postnatal NG2-expressing (NG2+) progenitor cells located in the SVZ self-renew in vitro and display phenotypic features of transit-amplifier type C-like multipotent cells. NG2+ cells in the SVZ are highly proliferative and express the epidermal growth factor receptor, the transcription factors Dlx, Mash1, and Olig2, and the Lewis X (LeX) antigen. We show that grafted early postnatal NG2+ cells generate hippocampal GABAergic interneurons that propagate action potentials and receive functional glutamatergic synaptic inputs. Our work identifies Dlx+/Mash1+/LeX+/NG2+/GFAP-negative cells of the SVZ as a new class of postnatal multipotent progenitor cells that may represent a specific cellular reservoir for renewal of postnatal and adult inhibitory interneurons in the hippocampus.

Action Potentials↗
PubMed2004

Expression of a catalytically inactive transmembrane protein tyrosine phosphatase epsilon (tm-PTP epsilon) delays optic nerve myelination.

Reversible tyrosine phosphorylation is integral to the process of oligodendrocyte differentiation. To interfere with the subset of the phosphorylation cycle overseen by protein tyrosine phosphatase epsilon (PTP epsilon) in oligodendrocytes, we applied a substrate-trapping approach in the development of transgenic mice overexpressing a catalytically inactive, transmembrane PTP epsilon-hemaglutinin (tm-PTP epsilon-HA) from the dual promoter element of the gene encoding the myelin protein 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP). Transgene expression peaked during the active myelinating period, at 2-3 weeks postnatal. Two tyrosine phosphoproteins, alpha-enolase and beta-actin, were phosphorylated to a greater degree in transgenic mice. Despite a high degree of tm-PTP epsilon-HA expression, myelin was grossly normal in nearly all axonal tracts. Phenotypic abnormalities were limited to optic nerve, where a decrease in the degree of myelination was reflected by reduced levels of myelin proteins on postnatal day 21 (PND21), as well as a decrease in the density of differentiated oligodendrocytes. The optic chiasm was reduced in thickness in transgenic mice; optic nerves similarly exhibited a reduction in transverse width. Further analyses of the optic pathway demonstrated that transgenic protein was unexpectedly present in retinal ganglion cells, whose axons are the targets of myelination by optic nerve oligodendrocytes. On PND28, transgenic protein declined dramatically in both oligodendrocytes and retinal ganglion cells contributing to the recovery of optic nerve myelination. Thus, delayed myelination arises only when tm-PTP epsilon-HA is simultaneously expressed in myelin-forming glia and their neuronal targets. While tm-PTP epsilon related signaling pathways may figure in axon-glial interactions, interfering with tm-PTP epsilon activity does not perceptibly affect the development or myelinating capacity of most oligodendrocytes.

Animals↗
PubMed2004

Shaker-type potassium channel subunits differentially control oligodendrocyte progenitor proliferation.

Oligodendrocyte precursor (OP) cells are exposed to multiple extrinsic signals that control their proliferation and differentiation. Previous cell proliferation studies and electrophysiological analysis in cultured cells and in brain slices have suggested that outward potassium channels, particularly Kv1 subunits, may have a prominent role in OP cell proliferation. In the present study, we assessed to what extent overexpression of Kv1.3, Kv1.4, Kv1.5, and Kv1.6 can affect OP cell proliferation and differentiation in culture. We observed that overexpression of Kv1.3 or Kv1.4 increased OP cell proliferation in the absence of mitogens, whereas Kv1.6 overexpression inhibited mitogen-induced OP cell cycle progression. Interestingly, Kv1.3, Kv1.4, Kv1.5, and Kv1.6 overexpression did not interfere with the kinetics of oligodendrocyte differentiation. This study represents the first demonstration that the activity of potassium channels containing distinct Kv1 subunit proteins directly controls oligodendroglial proliferation in the presence of mitogens, as well as in growth factor-free conditions.

Animals↗
PubMed2003

Postnatal NG2 proteoglycan-expressing progenitor cells are intrinsically multipotent and generate functional neurons.

Neurogenesis is known to persist in the adult mammalian central nervous system (CNS). The identity of the cells that generate new neurons in the postnatal CNS has become a crucial but elusive issue. Using a transgenic mouse, we show that NG2 proteoglycan-positive progenitor cells that express the 2',3'-cyclic nucleotide 3'-phosphodiesterase gene display a multipotent phenotype in vitro and generate electrically excitable neurons, as well as astrocytes and oligodendrocytes. The fast kinetics and the high rate of multipotent fate of these NG2+ progenitors in vitro reflect an intrinsic property, rather than reprogramming. We demonstrate in the hippocampus in vivo that a sizeable fraction of postnatal NG2+ progenitor cells are proliferative precursors whose progeny appears to differentiate into GABAergic neurons capable of propagating action potentials and displaying functional synaptic inputs. These data show that at least a subpopulation of postnatal NG2-expressing cells are CNS multipotent precursors that may underlie adult hippocampal neurogenesis.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗