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H Villarroya

Publications and source records attributed to H Villarroya.

At least 19 recordsLinked to original sources
PubMed2001

Distribution in ocular structures and optic pathways of immunocompetent and glial cells in an experimental allergic encephalomyelitis (EAE) relapsing model.

Relapsing experimental allergic encephalomyelitis (EAE) was induced in DA rats and the ocular pathologic events were examined at the various phases of the illness. About 80% of EAE rats presented anterior uveitis (AU), even after complete EAE recovery. We studied the phenotype and localization of immunocompetent cells, the major histocompatibility complex (MHC) class I and II antigen expression, as well as the chemokine monocyte chemoattractant protein-1 (MCP-1) appearance. In control animals, there were many glial fibrillary acidic protein (GFAP)(+) cells and OX42(+) cells in the ciliary body, retina, optic nerve and chiasma. Except in retina, we observed constitutive MHC class I and II expression. During the EAE acute phase, there was up-regulation of MHC class II and GFAP antigens in iris, ciliary body, limbus, and optic pathways. MHC class I and ED2 antigens were expressed in meninges and in the prechiasmatic cisterna, by cells which could have a role in immune surveillance. MCP-1 mRNA was highly expressed in optic pathways during the acute phase and the protein was expressed by astrocytes, macrophages, and lymphocytes. During the relapsing phase, MCP-1 was weakly expressed to disappear almost completely during the final recovery phase. The expression of MHC class II on astrocytes was increased during the relapsing and final recovery phase in which the inflammatory lesions persisted. These findings suggest that ocular areas and optic pathways, mainly optic chiasma, are important targets in the relapsing EAE.

Animals↗
PubMed2000

Distribution of albumin nanoparticles in animals induced with the experimental allergic encephalomyelitis.

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease characterised by a disruption of the blood-brain barrier (BBB), demyelination and a relevant inflammatory reaction with an intense infiltration of macrophages. These neurological disorders are similar to those observed in the multiple sclerosis (MS) disease. The use of different liposomes and adeno-associated virus has been proposed for improving the treatment of this pathogenesis. The aim of this work was to evaluate the potential and capacity of albumin nanoparticles to reach the central nervous system (CNS) in EAE-induced rats. For this purpose, the distribution of biotinylated nanoparticles within the CNS was studied. Albumin carriers were mainly found in the lumbar portion of the spinal cord, overlying the meningeal and perivascular areas. The optic chiasma, iris and the area of the Purkinje cells of the cerebellum revealed also an intense presence of these carriers. Finally, immunohistochemical studies also revealed that circulating macrophages (ED1), which migrate to damaged sites, and resident activated microglial cells (OX42) were involved in the distribution of albumin nanoparticles. In summary, the use of nanoparticles may be useful for the design of new pharmaceutical dosage forms able to target the lesions associated with alterations of the BBB.

Animals↗
PubMed1999

Fas system up-regulation in experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a T-cell-mediated disorder characterized by infiltration of the central nervous system (CNS) by mononuclear cells and macrophages, and serves as a model for multiple sclerosis. In acute monophasic and relapsing remitting forms of EAE, the CNS inflammatory infiltrates are cleared within a few days and, simultaneously, animals recover from their clinical disability. The mechanisms for rapid disappearance of the inflammatory cells are not fully understood. Fas and Fas-ligand (Fas-L) molecules are thought to play an important role in the deletion of autoimmune reactive T cells through apoptosis. However, recent observations in transgenic lpr and gld mice show that mutations inactivating Fas and Fas-L respectively ameliorate signs of EAE despite persistence of immune cell infiltrates into the CNS. In the current study, the expression of Fas and Fas-L was investigated by immunochemistry and in situ hybridization during the course of EAE in DA rats that were actively immunized with syngenic spinal cord homogenate. CNS apoptotic cells were simultaneously examined using terminal transferase dUTP nick end-labeling techniques. During the acute phase of the disease, a significant proportion of CNS CD4+ cells (80%) and macrophages (50%) expressed Fas and Fas-L (80 and 60%, respectively). Simultaneously, about 20% of CD4+ cells and 30% of macrophages were found to be apoptotic. Some astrocytes and neurons also expressed Fas and Fas-L, although they did not appear to be apoptotic. These results further support a role for Fas-mediated lymphocyte and macrophage apoptosis in this model of CNS autoimmune disease but they also suggest a more complex role for Fas/Fas-L interactions in CNS autoimmunity, including resident cells.

Animals↗
PubMed1997

Expression of TNF alpha in central neurons of Lewis rat spinal cord after EAE induction.

Experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS), is a demyelinating autoimmune disease of the central nervous system (CNS). The proinflammatory cytokine TNF alpha, as an endogenous mediator of inflammation, plays an important role in the pathogenesis of EAE disease. In this study, we demonstrate the presence of TNF alpha in spinal cord of Lewis rats, during the critical phase of EAE. The expression of TNF alpha is observed mainly in the gray matter of thoracic and lumbar levels of the spinal cord, in the motoneurons and interneurons of the ventral horn. Surprisingly, one month after recovery, we still found an intense TNF alpha-neuronal expression, including in the cervical region, and this positivity lasted up to 40 days after recovery, with, however, a decrease in its intensity. These results suggest that central neurons respond directly to massive infiltration of lymphocytes and macrophages after the breakdown of the blood-brain barrier (BBB), by producing TNF alpha cytokine. In addition, neuronal-TNF alpha detection in the recovery stage of EAE may suggest a role other than its classical action in promoting inflammatory processes.

Animals↗
PubMed1996

Myelin-induced experimental allergic encephalomyelitis in Lewis rats: tumor necrosis factor alpha levels in serum and cerebrospinal fluid immunohistochemical expression in glial cells and macrophages of optic nerve and spinal cord.

Tumor necrosis factor alpha (TNFalpha) activity was measured in serum and cerebrospinal fluid (CSF) of Lewis rats after experimental allergic encephalomyelitis (EAE) induction and during the clinical course of acute disease. TNFalpha bioactivity expression preceded the clinical symptoms and paralleled the severity of disease. We further investigated the identity of the central nervous system (CNS) cells involved in TNFalpha expression and their regional localization during EAE. Tissue sections of brain, cerebellum, dorsal spinal cord and optic nerve were studied by indirect double labelling immunofluorescence. Spinal cord white matter and optic nerve showed a widespread TNFalpha immunoreactivity at critical stages of EAE in macrophages/microglia and astrocytes. We have shown changes in CSF/serum albumin ratio and immunoglobulin G index during EAE. Our results confirm the very important role of TNFalpha in EAE.

Animals↗
PubMed1994

Transplanted transgenically marked oligodendrocytes survive, migrate and myelinate in the normal mouse brain as they do in the shiverer mouse brain.

The dye Hoechst 33342 was combined with an immunodetectable transgene product (chloramphenicol acetyltransferase, CAT) expressed in differentiated oligodendrocytes to trace their fate after transplantation in the normal and the shiverer mouse brain. In the shiverer brain, the technique allowed us to visualize grafted cells inside myelin basic protein-positive myelin patches. Most of these cells were CAT-positive/Hoechst 33342-negative, reinforcing our hypothesis that cell division probably follows migration of grafted oligodendrocytes. Correlation of their morphology and distribution with their location in the host CNS suggested a local effect on the cell division and morphogenesis of the grafted material. When compared with transplantation of fragments of normal newborn donor tissue into the newborn shiverer brain, no difference could be seen between the behaviour of normal and transgenic oligodendrocytes. In the normal brain, transgenic oligodendrocytes survived at least 150 days and successfully myelinated the host axons. The timing of differentiation of grafted cells was similar in both types of recipient brains. Migration occurred rostrally and caudally. Although migrating cells could be observed along the meninges and the blood vessels, migration occurred preferentially along white matter tracts. The extent of migration was influenced by the site of implantation, and grafted cells could be found up to 6 mm from the grafting point. No differences in the timing of differentiation or the pattern or extent of migration could thus be demonstrated when transgenic oligodendrocytes were transplanted in the normal or the shiverer brain. This validates our previous studies using the newborn shiverer mouse as recipient.

Animals↗
PubMed1994

Cellular expression of an HMGCR promoter-CAT fusion gene in transgenic mouse brain: evidence for a developmental regulation in oligodendrocytes.

The HMGCR gene encodes the 3-hydroxy-3-methylglutaryl coenzyme A reductase, which is the key enzyme for cholesterol synthesis. Mice transgenic for the prokaryotic chloramphenicol acetyl transferase (CAT) reporter gene fused with a 5' Bam H1 fragment including the promoter sequence for murine HMGCR gene have been obtained. Homozygote transgenic mice were derived from a particular line selected for similar regulation of endogenous HMGCR and the transgene expression by nutritional conditions in different tissue. In addition, high expression of the transgene was evidenced in the brain. Cellular expression of the CAT gene in the central nervous system (CNS) was investigated by immunohistochemistry (IHC). This study was performed on frozen sections of the developing and adult brain, using a rabbit anti-CAT antiserum especially raised for that purpose. CAT expression was observed in some rare individuals in different neural cell types including Purkinje cells and astrocytes. But the most outstanding observation was the high level of CAT expression correlated with differentiated pattern of oligodendrocyte (Ol) distribution observed in white-matter tracts. Double and triple labeling for CAT and stage-specific antigens were performed on transgenic Ol-enriched preparations and cultures. This study showed a normal sequence of differentiation in the transgenic oligodendroglial cell lineage and demonstrated a strict correlation between late differentiation and activation of the CAT gene in these cells: CAT expression started in transgenic Ols between galactocerebroside (GC)-positive and myelin basic protein (MBP)-positive stages and was detected in MBP-positive cells during the myelination period. After myelination, the number of CAT-positive Ols decreased in the adult brain. These observations demonstrate a developmental regulation of the CAT transgene in Ols during myelination in CNS and reinforce the hypothesis of endogenous synthesis as major source of cholesterol during myelination.

Animals↗
PubMed1993

Even in culture, oligodendrocytes myelinate solely axons.

Cerebral hemispheres from mouse embryos at 15 days of gestation were dissociated and maintained in culture for several weeks in a medium which permitted homochronic and homotypic oligodendrocytes and neurons to interact in the presence of other central nervous system cells. After 13-14 days in culture a few oligodendrocytes changed from highly branched, "sun-like," nonmyelinating cells to sparcely branched myelinating cells. The number of fibers myelinated per oligodendrocyte ranged from 1 to 10, similar to that described previously in vivo in the corpus callosum. When an oligodendrocyte began to myelinate, it immediately myelinated a maximum number of fibers, suggesting that the number of axons to be myelinated by the oligodendrocyte was predetermined. When only one fiber was in the vicinity of a myelinating oligodendrocyte, whorls of myelin-like figures were seen at the tip of oligodendrocyte processes that had not reached an axon. Myelinated fibers were unambiguously identified as axons both by immunostaining and by electron microscopy. Myelin was not observed around astrocyte processes or around dendrites. The exclusive myelination of axons suggests the existence of a specific axonal recognition signal which attracts oligodendrocyte processes.

Animals↗
PubMed1993

Mercury-induced autoreactive anti-class II T cell line protects from experimental autoimmune encephalomyelitis by the bias of CD8+ antiergotypic cells in Lewis rats.

Brown-Norway (BN) rats injected with HgCl2 develop a systemic autoimmune disease associated with a polyclonal B cell activation, due to autoreactive T cells specific for self-class II molecules, while Lewis (LEW) rats injected with HgCl2 do not exhibit autoimmunity and develop a non-antigen-specific, CD8-mediated immunosuppression assessed by a depression of T cell functions, and a protection against experimental autoimmune encephalomyelitis (EAE). Resistance to HgCl2-induced autoimmunity is not due to these suppressor cells since treatment with an anti-CD8 monoclonal antibody (mAb) did not allow autoimmunity to appear. The absence of autoimmunity in this strain could result from the absence of autoreactive T cells, or from quantitative or qualitative differences of these cells between susceptible and resistant strains. In the present study, we show that CD4+ anti-class II T cells are present in HgCl2-injected LEW rats and are as frequent as in BN rats when assessed by limiting dilution analysis. LEW CD4+ autoreactive T cell lines were derived. They proliferated in the presence of normal class II-bearing cells, secreted interleukin 2, and did not induce B cells to produce immunoglobulins. Transfer of one of these lines, LEW Hg A, into normal LEW rats led to the appearance of CD8+ cells responsible for a non-antigen-specific immunosuppression that induced complete protection from EAE. Immunosuppression was abrogated after treatment with an anti-CD8 mAb. In vitro, CD8+ cells from rats injected with the LEW Hg A T cell line proliferated in the presence of activated T cells whatever their origin. We conclude that HgCl2 induces CD4+ autoreactive T cells that proliferate in the presence of class II+ cells in susceptible BN as well as in resistant LEW rats. But while these cells collaborate with B cells to produce autoantibodies in BN rats, they initiate in LEW rats a suppressor circuit involving antiergotypic CD8+ suppressor cells.

Animals↗
PubMed1993

Migration pathways, differentiation and survival of macroglial cells from a xenograft implanted into the thalamus of newborn mice.

Embryonic rabbit corpus callosum transplants were grafted into thalamus of newborn shiverer mice in order to compare the fates of oligodendroglial and astroglial cells derived from the transplants. Our model allowed the identification of the two populations of macroglial cells. The thalamus was chosen as site of implantation because of its situation at a crossroad of numerous neuronal fascicles. Previous studies, where the dorsal striatum was used as site of implantation, had shown that corpus callosum was one of the favorite routes of migration for both populations of macroglial cells. In the present study special attention was given to the comparison of the migration pathways and areas of settlement of implanted astroglia and oligodendroglia. The internal capsule, the medial lemniscus, the crus cerebri and the thalamic radiations were used by both populations of transplant derived macroglial cells for their migrations through the host parenchyma. They integrated into the host tissue on these routes or further away in areas such as the putamen, the mesencephalon or the colliculi. Signs of degeneration of the implanted astroglia were often observed after 1 month post-implantation.

Animals↗
PubMed1992

Carbohydrate moieties of myelin-associated glycoprotein, major glycoprotein of the peripheral nervous system myelin and other myelin glycoproteins potentially involved in cell adhesion.

The myelin-associated glycoprotein (MAG) and the major glycoprotein of the peripheral nervous system myelin (P0) are two members of the family of cell adhesion molecules (CAMs). A role in cell adhesion of the carbohydrate moiety of these molecules has been attributed to the presence of N-glycans bearing the HNK-1 carbohydrate epitope. On the other hand, it has been suggested that these glycoproteins could be ligands of an endogenous mannose-binding lectin present in myelin, the cerebellar soluble lectin (CSL). In order to further document the heterogeneity of the glycans of these two CAMs, we have used several probes: an anti-carbohydrate antibody of the HNK-1 type, called Elec-39, the plant lectin concanavalin A (ConA), and the endogenous lectin CSL involved in myelin compaction. This study shows that CSL binds to a small proportion of the polypeptide chains of MAG found in adult CNS of rats and man and the polypeptide chains of P0 molecules from adult human and rat sciatic nerve. For MAG from adult rat brain, the binding of CSL is restricted to glycans of polypeptide chains which could be separated from the others according to their solubility properties. These MAG molecular entities react also with the Elec-39 antibody and with ConA. These results confirm that P0 and MAG are heterogeneous in their carbohydrate moieties.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Comparative migration and development of astroglial and oligodendroglial cell populations from a brain xenograft.

In previous studies of brain transplantation, the fate of the implanted glial cells has been investigated separately; that is, the interest has been focused either on the astroglia or on the oligodendroglia. However, the two populations of implanted glial cells may interact with each other, for example by secreting species-specific factors or by inducing reactions by the host. We have used two different models of brain transplantation: one that allows the identification of the implanted astrocytes, and another that allows the identification of the implanted oligodendroglia. The present model is a combination of both; it consists of the grafting of embryonic rabbit brain fragments into the brains of neonatal Shiverer mice. The myelin made by the implanted oligodendrocytes is identified by anti-myelin basic protein immunohistochemistry. The implanted astrocytes are identified by a monoclonal antibody that combines with rabbit but not with mouse glial fibrillary acidic protein. This study shows that although they use the same major routes of migration, both populations of glial cells tend to move differently. They demonstrate areas of common settlement but also areas where only one population of implanted glia is present. From the site of implantation in the dorsal striatum, the major routes of migration are the corpus callosum, the white matter fascicles in the striatum, and the internal capsule. After a delay of 6 weeks, no significant prevalence of one population of implanted glial cells over the other was observed.

Animals↗
PubMed1991

HgCl2-induced perturbation of the T cell network in experimental allergic encephalomyelitis. I. In vitro characterization of T cells involved.

Mercuric chloride (HgCl2) induces in Lewis (LEW) rats a non-antigen-specific immunosuppression and is able to down-modulate experimental allergic encephalomyelitis in about 70% of the rats. The aim of the present study was to determine the frequencies of lymph node cells involved in the proliferative response to myelin basic protein in rats injected with HgCl2 and immunized with myelin by using limiting dilution analysis (LDA). Highly frequent CD8+ T suppressor cells and at least 10-fold less frequent protein basic-specific T helper cells were detected in these rats. A third cell type allowing the proliferative response of Th cells in spite of Ts cells was also demonstrated. These cells, which could act as contrasuppressor cells, were CD4+ and adhered to Vicia villosa lectin; their frequency was in the same range as that of T helper cells. These data illustrate the potential role of different levels of T cell immunoregulatory activity in autoimmunity and the major interest of LDA in their analysis.

Animals↗
PubMed1991

HgCl2-induced perturbation of the T cell network in experimental allergic encephalomyelitis. II. In vivo demonstration of the role of T suppressor and contrasuppressor cells.

In the companion paper (J. Rossert et al., Cell. Immunol. 137, 1991), we showed by using limiting dilution analysis that Lewis (LEW) rats injected with HgCl2 and immunized with myelin (LEWHg/MYE) exhibit anti-basic protein CD4+ T helper cells (Th), at least 10-fold more frequent CD8+ T suppressor cells (Ts), and T contrasuppressor cells (Tcs). These Tcs cells were shown to be CD4+ T cells adhering to Vicia villosa (VV) lectin and allowed Th cells to proliferate despite the presence of Ts cells. The CD8+ Ts cells might be responsible for the protection from experimental allergic encephalomyelitis (EAE) observed in about 70% of LEW rats injected with HgCl2. The concomitant presence of CD4+ Tcs cells might explain that 30% of the rats escaped this protection. The aim of this work is to demonstrate in vivo the roles of CD8+ Ts cells and Tcs cells in mercury-induced protection from EAE. It will be shown that LEWHg/MYE rats depleted of CD8+ cells as well as LEWHg/MYE rats transferred with VV lectin-adherent Tcs cells develop EAE. These data demonstrate that CD8+ Ts cells are responsible for HgCl2-induced protection and that Tcs cells are involved in the control of Ts cells in vivo.

Animals↗
PubMed1990

Patchy myelination pattern in the jimpy mouse brain: immunohistochemical study.

The jimpy (jp) mutation of the mouse leads to a dramatic decrease of myelination in the hemizygous mutant central nervous system (CNS). Several descriptions based on classical histology, immunohistochemistry, and electron microscopy (EM) have demonstrated the scarcity of myelin formation in the different parts of the CNS. The immunohistochemical study presented here showed a very singular patchy pattern of myelin distribution in the different areas of the whole mutant brain. The myelin patches are randomly dispersed without bilateral symmetry, and their density and location vary from one animal to another. No reproducible pattern of myelination could be found among the population observed. This distribution has been compared with observations on young heterozygotes and wild-type homozygotes from the same strain. A similar patchy and random distribution of myelin could be observed in heterozygotes, which present an intermediate level of myelination. This strongly suggests that a migration of precursors or immature oligodendrocytes (ODCs) from the periventricular zone followed by local multiplication of colonies of ODCs before myelination is a general feature in normal as well as pathological conditions.

Animals↗
PubMed1990

Glial fibrillary acidic protein and beta A4 protein deposits in temporal lobe of aging brain and senile dementia of the Alzheimer type: relation with the cognitive state and with quantitative studies of senile plaques and neurofibrillary tangles.

The aim of this study was to compare brain glial fibrillary acidic protein (GFAP) levels to the modifications of cognitive functions (Blessed test score [BTS]), the density of the main neuropathological lesions (senile plaques [SP] and neurofibrillary tangles [NFT]), and the density of the two main subtypes of beta A4 deposits (classic plaques and diffuse deposits) in a series of patients with normal aging and senile dementia of the Alzheimer type of various degrees of severity. GFAP levels (enzyme-linked immunosorbent assay [ELISA] technique) and the densities of changes were measured in the temporal lobe of 12 women over 75 years of age. Under these conditions, the ELISA assay could determine GFAP in brain homogenates (aqueous-Triton buffer soluble extract) in a range from 2.5 ng to 600 ng per assay. Least affected patients (with a BTS of 19 and over) all ranged below 60 micrograms/mg protein. Most affected patients (with a BTS under 6) ranged above 150 micrograms/mg protein. However, interindividual variations were wide. A significant correlation between the BTS and the amount of GFAP could be found only when using the non parametric test of Spearman. There was a significant positive correlation between the amount of GFAP and the density of 1) SP, 2) NFT both revealed by Bodian's silver stain, and 3) classic beta A4 plaques shown by immunocytochemistry. On the contrary, no correlation was observed with diffuse beta A4 deposits. One case with very large amounts of diffuse beta A4 deposits without SP or NFT showed no associated GFAP reactivity. This suggests that GFAP production is a critical event in the formation of classic SP.

Aged↗
PubMed1990

Differential susceptibility to experimental allergic encephalomyelitis (EAE) in genetically defined A+ and A- rabbits.

Only one out of 57 A-/A- rabbits immunized with rat or guinea-pig myelin developed clinical signs suggestive of EAE. On the contrary, clinical signs of acute or chronic EAE were found in two thirds of the 102 A+/A+ and A+/A- rabbits immunized in the same way. About one third of the diseased animals had reversible acute EAE, another third died paralysed and the last third developed chronic progressive or relapsing EAE. Incidence and severity of EAE symptoms were positively correlated with age and no significant difference was observed between males and females. Cellular and humoral anti-myelin responses were stronger in A+ than in A- rabbits. Anti-A antibodies, on the contrary, were only detected in A- rabbits. The A+ rabbits did not make Anti-A at any time. Anti-A antibodies increased early, in A- rabbits, after immunization with myelin (11-30 days) and were later replaced by a low, but specific, anti-myelin response (60-90 days). The gene responsible for the susceptibility to EAE is autosomal and dominant over resistance. This gene must be closely linked to the A locus or might be the A gene itself. The low susceptibility of A- rabbits to the disease could be, in this last case, a consequence of the competition between the early anti-A and the normal anti-myelin immune responses, both induced by the injection of myelin.

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