Specific features of chronic astrocyte gliosis after experimental central nervous system (CNS) xenografting and in Wobbler neurological mutant CNS

This study sets out to compare and contrast the astrocyte reaction in two unrelated experimental designs both resulting in marked chronic astrogliosis and natural motoneuron death in the wobbler mutant mouse and brain damage in the context of transplantation of xenogeneic embryonic CNS tissue into the striatum of newborn mice. The combined use of GFAP-labeling and confocal imaging allows the morphological comparison between these two different types of astrogliosis. Our findings demonstrate that, in mice, after tissue transplantation in the striatum, gliosis is not restricted to the regions of damage: it occurs not only near the site of transplantation, the striatum, but also in more distant regions of the CNS and particularly in the spinal cord. In the wobbler mutant mouse, a strong gliosis is observed in the spinal cord, site of motoneuronal cell loss. However, moderate astrocytic reaction (increased GFAP-immunoreactivity) can also be found in other wobbler CNS regions, remote from the spinal cord. In the wobbler ventral horn, where neurons degenerate, the hypertrophied reactive astrocytes exhibit a dramatic increase of glial fibrils and surround the motoneuron cell bodies, occupying most of the motoneuron environment. The striking and specific presence of hypertrophic astrocytes in wobbler mice accompanied by a dramatic increase of glial fibrils located in the vicinity of motoneuron cell bodies suggests that short astrogliosis fills the space left by degenerating motoneurons and interferes with their survival. In the spinal cord of xenografted mice, chronic astrogliosis is also observed, but only glial processes without hypertrophied cell bodies are found in the neuronal micro-environment. It is tempting to speculate that gliosis in the wobbler spinal cord, the local accumulation of astrocyte cell bodies, and high density of astrocytic processes may interfere with the diffusion of neuroactive substances in gliotic tissue, some of which are neurotoxic, and cooperate or even trigger neuronal death.

Cytokine signals propagate through the brain

Interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha) are proinflammatory cytokines that are constitutively expressed in healthy, adult brain where they mediate normal neural functions such as sleep. They are neuromodulators expressed by and acting on neurons and glia. IL-1 and TNFalpha expression is upregulated in several important diseases/disorders. Upregulation of IL-1 and/or TNFalpha expression, elicited centrally or systemically, propagates through brain parenchyma following specific spatio-temporal patterns. We propose that cytokine signals propagate along neuronal projections and extracellular diffusion pathways by molecular cascades that need to be further elucidated. This elucidation is a prerequisite for better understanding of reciprocal interactions between nervous, endocrine and immune systems.

"Inflammatory" cytokines: neuromodulators in normal brain?

If cytokines are constitutively expressed by and act on neurons in normal adult brain, then we may have to modify our current view that they are predominantly inflammatory mediators. We critically reviewed the literature to determine whether we could find experimental basis for such a modification. We focused on two "proinflammatory" cytokines, interleukin (IL)-1 and tumor necrosis factor-alpha (TNFalpha) because they have been most thoroughly investigated in shaping our current thinking. Evidence, although equivocal, indicates that the genes coding for these cytokines and their accessory proteins are expressed by neurons, in addition to glial cells, in normal brain. Their expression is region- and cell type-specific. Furthermore, bioactive cytokines have been extracted from various regions of normal brain. The cytokines' receptors selectively are present on all neural cell types, rendering them responsive to cytokine signaling. Blocking their action modifies multiple neural "housekeeping" functions. For example, blocking IL-1 or TNFalpha by several independent means alters regulation of sleep. This indicates that these cytokines likely modulate in the brain behavior of a normal organism. In addition, these cytokines are likely involved in synaptic plasticity, neural transmission, and Ca2+ signaling. Thus, the evidence strongly suggests that these cytokines perform neural functions in normal brain. We therefore propose that they should be thought of as neuromodulators in addition to inflammatory mediators.

Astrocyte proliferation induced by wobbler astrocyte conditioned medium is blocked by tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) neutralizing antibodies in vitro

The wobbler mutant mouse (wr/wr) displays motoneuron degeneration and astrocyte reactivity in the spinal cord. We have previously reported that, in vitro, primary wobbler astrocytes display morphological and biochemical changes. In this report, we show that wobbler astrocyte conditioned medium enhances the in vitro proliferation of normal neonatal primary astrocytes. This stimulated proliferation is correlated with high levels of IL1-beta and TNF-alpha cytokines in the conditioned medium of wobbler astrocytes. Neutralizing antibodies directed against both IL1-beta and TNF-alpha block the wobbler astrocyte conditioned medium-enhanced astrocyte proliferation. Moreover, IL1-beta and TNF-alpha mRNAs are elevated in the wobbler spinal cord. All these data suggest that diffusible IL1-beta and TNF-alpha are involved in the processus of astrogliosis observed in the wobbler spinal cord.

Expression of interleukin-1 genes and interleukin-1 receptors in the mouse brain after hippocampal injury

In order to evaluate the role of IL-1 production in post-traumatic brain, transcripts for IL-1 (alpha, beta, RA) have been quantified following RT-PCR, in hippocampus and cortex after injury of either hippocampus (Hip) or striatum (Stri). Moreover, 125I IL-1alpha binding sites have been directly quantified using binding experiments on brain sections and quantitative autoradiography. Under basal conditions, levels of PCR products were very low. On day 1, IL-1RA transcripts only were strongly increased in the hippocampus after Hip-lesions and in cortex after Stri lesion. Transcripts were back to control values on day 7 post-lesion. IL-1 receptor densities in the hippocampus (dentate gyrus) were decreased at day 1 around the site of the lesion (but not on the contralateral side) and were back to controls on day 7 indicating a transient and local IL-1 production in the surroundings of the lesion. No changes were found following Stri lesion. This study provides further evidence of the role of the IL-1 molecules family, notably IL-1RA, in the brain reaction to trauma.

Specific pattern of nitric oxide synthase expression in glial cells after hippocampal injury

In the central nervous system (CNS), nitric oxide (NO) is thought to be involved in a variety of functions including synaptic plasticity, long term potentiation, and neurotoxicity. The aim of the present study was to investigate the expression of nitric oxide synthase (NOS) in the mouse CNS, following surgical injury to the hippocampus. NOS expression was assessed by histochemical detection of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) activity and immunohistochemistry of the inducible NOS (iNOS). Two days after injury to the CA1 hippocampal field, NADPH-diaphorase activity was detected in pyramidal and granular neurons and also in glial cells in the hippocampus, in contrast to the non-injured one where NADPH-diaphorase staining was observed only in a few interneurons. NADPH-diaphorase histochemistry combined with immunolabelling for GFAP and F4/80 demonstrated that these glial cells were astrocytes and microglia. This pattern of NOS expression is induced specifically after a hippocampal injury since lesion to the prefrontal or cerebellar cortex leads to NOS activity only in monocytes/macrophages like cells. Despite the large expression of NOS detected by NADPH-diaphorase histochemistry after lesioning the hippocampus, immunostaining for iNOS was confined to microglia. The fact that induction of high levels of NOS activity are detected in glial cells after a lesion to the hippocampus could be accounted for by the sensitivity of this structure to a high release of glutamate.

Widespread neuronal expression of c-Fos throughout the brain and local expression in glia following a hippocampal injury

Fos oncoprotein is an immediate early gene product and a marker of cell activation following a variety of insults. We have previously shown that a mechanical lesion to the hippocampus of adult mice induces a neuronal expression of the cytokines interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF alpha) whereas a lesion to the striatum does not. The role of these inflammatory cytokines in the pathophysiology of central neurons is still unclear. The present work was undertaken to study a possible correlation between the central expression patterns of c-Fos on the one hand and IL-1alpha and TNF alpha on the other hand. We show that Fos is expressed in a majority of brain neurons after a unilateral lesion to the hippocampus whereas it is confined to the site of injury when applied to the striatum, as previously described for the expression of the cytokines.

Gene transfer to the central nervous system by transplantation of cerebral endothelial cells

A cerebral endothelial immortalized cell line was used in transplantation experiments to deliver gene products to the adult rat brain. Survival of grafted cells was observed for at least 1 year, without any sign of tumor formation. When genetically modified to express bacterial beta-galactosidase and transplanted into the striatum, these cells were shown, by light and electron microscope analysis, to integrate into the host brain parenchyma and microvasculature. Following implantation into the striatum and nucleus basalis of adult rats, endothelial cells engineered to secrete mouse beta-nerve growth factor (NGF) induced the formation of a dense network of low-affinity NGF receptor-expressing fibers near the implantation sites. This biological response was observed from 3 to 8 weeks after engraftment. The present study establishes the cerebral endothelial cell as an efficient vector for gene transfer to the central nervous system.

Identification and topography of neuronal cell populations expressing TNF alpha and IL-1 alpha in response to hippocampal lesion

In previous studies, we have shown that a traumatic lesion to the hippocampus of adult mice induces the transitory expression of TNF alpha and IL-1 alpha by neurons of different brain areas and also by glial cells at the site of injury. The aim of the present study was to establish whether the expression of TNF alpha and IL-1 alpha is restricted to defined subpopulations, or else is common to most of the central neuronal populations. Using polyclonal anti-GAD 67, anti-TH and monoclonal anti-ChAT, and anti-5-HT antibodies in a double-labeling immunohistochemical procedure in combination with murine anti-TNF alpha and anti-IL-1 alpha polyclonal antibodies, we show that most GABAergic, catecholaminergic, and serotoninergic neurons, and a subgroup of the cholinergic neurons, express these cytokines. Although not immunohistochemically characterized, neurons in some glutamatergic structures such as the hippocampus and the prefrontal cortex also express these cytokines. Thus, we conclude that the capacity of central neurons to express cytokines like TNF alpha and IL-1 alpha in reaction to a brain injury is not restricted to peculiar neuronal subtypes, but could include most of the neuronal populations of the brain.

Differential oligodendroglial expression of the tumor necrosis factor receptors in vivo and in vitro

The cytokine tumor necrosis factor-alpha (TNF alpha) has been proposed to play a key role in the degenerative processes observed in demyelinating diseases such as multiple sclerosis (MS). In the immune system the cellular responses to TNF are mediated by two different receptors: TNF-RI, which is involved in cell death, and TNF-RII, which has been shown to mediate cell proliferation. We investigated the oligodendroglial expression of TNF-RI and -RII. In vivo, in normal adult rodent brain, oligodendrocytes express TNF-RII but not TNF-RI. However, after 3 days in culture, both types of receptors were expressed by mature oligodendrocytes, purified from 4-week-old rats, suggesting that expression of TNF-RI was induced by either the isolation process or the culture conditions. This inducibility of TNF-RI may explain the differences in oligodendrocyte cell death reported in various experimental conditions and in the pathology of MS lesions.

[New concepts on the role of cytokines in the central nervous system]

Initially described as modulatory molecules in the peripheral immune system and during haematopoiesis, several cytokines also play a role in the brain. Their synthesis in the central nervous system (CNS) is not due solely to glial cell activation or invading immune cells. On the one hand, several functions of central neurons are modulated by cytokines such as IL-1, TNF alpha, IL-2 and IL-6. Thus, IL-1 and TNF alpha modulate the synthesis of several neuromediators and modify ion influxes. IL-2 regulates the effects of central dopaminergic neurons on cholinergic, noradrenergic, serotoninergic and glutamatergic functions. On the other hand, neurons have recently been shown to be able to synthesize some of these cytokines under specific traumatic conditions. For example, a lesion to the hippocampus induces neuronal synthesis of IL-1 alpha and TNF alpha. This induction through neuronal circuits may operate at a distance in contrast to the glial reaction operating only locally. The recent demonstration of the expression by central neurons of receptors specific for these cytokines support a potentially crucial role for these molecules in brain function. Some data emerge in the literature demonstrating a potent expression of cytokines in the central nervous system in numerous pathological situations. Then, it appears that, at the interface between nervous and immune systems, cytokines may bear a pivotal role in the development of specific symptoms in neuroimmune diseases.

TNF alpha gene expression is induced in neurones after a hippocampal lesion

The tumour necrosis factor alpha (TNF alpha) protein is normally absent in the brain. Its production in the nervous tissue during pathological processes is commonly attributed to cells of the macrophage or astroglial lineages. However, an immunoreactivity for TNF alpha has been observed recently in adult mouse brain after a lesion to the hippocampus. The identification, in the present study, of the cells responsible for this synthesis demonstrates a neuronal localization of the TNF alpha messenger RNA. We propose that neurone-produced TNF alpha acts as a modulatory effector in post-traumatic regenerative attempts of the brain.

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.

Regional and developmental variations of GFAP and actin mRNA levels in the CNS of jimpy and shiverer mutant mice

Gliosis is a common reaction to brain damage. Glial fibrillary acidic protein (GFAP) is a classical astrocytic marker. We have undertaken to measure the level of GFAP-mRNA as an index of gliosis in the brain of jimpy (jp) and shiverer (shi) murine mutants, in which hypomyelination is either severe or moderate, respectively. This study was conducted in five different CNS regions and at different ages. In young jp mutant, the amount of GFAP-mRNA was either normal or lower than in control animals; but after 3 wk of age, the level of GFAP-transcript increased dramatically in all regions examined. A parallel increase in actin-mRNA was also observed, mostly in the diencephalon and to a lesser extent in cortex and spinal cord, but not in the cerebellum and brainstem. In the shi mutant, variations in the amount of GFAP-mRNA were less important than in the jp with two exceptions: In brainstem of 3-wk-old animals, a 2.5-fold increase was observed, and in all the regions but the spinal cord of 12-d-old shi, the levels of GFAP-transcript were 2-5 times lower than in controls. In this mutant, the levels of actin message were usually close to normal, or slightly lower than in controls.

Glial biology and disorders

Much work has been devoted this year to the localization and mode of expression of growth factors and cytokines. Although it is not possible to extrapolate directly from in vitro to in vivo conditions, the plasticity of glial cells seems to be very influenced by growth factors. Astrocytes in vivo do not express many growth factors during normal conditions, but a pathologic event can lift these restrictions. Cytokines and their receptors have been localized on neuronal or glial cell types. The programmed cell death, well identified in neurons, seems to occur also in oligodendrocytes and may be influenced by survival factors. In the adult brain, glial progenitors are present and may be a potential source to generate myelinating oligodendrocytes for myelin repair. In the peripheral nervous system, axonal-Schwann cell signaling may function in both directions during development. Some animal neurologic mutants are models for human diseases; one of them, the Trembler mouse, has effectively led to the genetic characterization of Charcot-Marie-Tooth disease type 1a. As for myelin destruction, the relationship between demyelination and inflammation is still not very clear.

Localization of TNF alpha and IL-1 alpha immunoreactivities in striatal neurons after surgical injury to the hippocampus

Since the inflammatory process develops after transplantation to the brain, we sought to determine the presence of cytokines following a surgical trauma to the brain of an adult mouse. We report the early and marked presence of tumor necrosis factor-alpha and interleukin-1 alpha in neuronal somata of the striatum following a surgical injury to the hippocampus. The expression of cytokines later extends to neuronal cells of the hippocampus, thalamus, cerebral cortex, brain stem, and cerebellum and to glial cells of the corpus callosum. By contrast, these cytokines are not expressed by neuronal cells following injury to other regions, such as the striatum, cerebellum, and cortex. This study suggests a possible role for certain neurons in the brain's early reaction to a penetrating injury.

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.

Human Schwann cells in culture: characterization and reactivity with human anti-sulfated glucuronyl glycolipid monoclonal IgM antibodies

Schwann cells in cultures derived from human fetal peripheral nervous system were characterized by their morphology and indirect immunofluorescence with anti-galactocerebroside and anti-laminin antibodies. They stained strongly with human monoclonal IgM anti-sulfated glucuronyl glycolipid antibodies in double labeling experiments.

In situ transformation of striatal glia into cerebellar-like glia after brain transplantation

Transplants of striatum from rabbit embryo were implanted into the colliculus posterior of newborn mice. After 4 weeks, astroglial cells derived from the transplant had migrated into the cerebellum of the host. Whenever they had settled in the cerebellum they presented forms similar to local glia. Some migrated glial cells were found to transform into forms of glia, such as radial-like glia, which are not present in the striatum. This observation confirms that glial precursor cells are highly plastic. It is an in vivo demonstration that local conditions alone define the morphology of glial cells. After grafting in an heterotopic location they take on forms that they were not destined to express in the region of origin.

Xenogenic transplantation into newborn rodent brain: neovascularization of the graft by the host

Neoangiogenesis of transplants implanted into the brains of newborn rodent hosts was evaluated by immunohistochemistry for 2 weeks after the operation. The use of species-specific antibodies directed against mouse endothelial cells demonstrated the respective participation of the host and the donor in the formation of new vessels in the graft after crossed rabbit into mouse and mouse into rat transplantation experiments. We show that blood vessels made by host endothelial cells begin to penetrate the transplant 24 h after grafting, and cross it completely by 72 h. Simultaneously, host astrocytes invade the transplant.

Developmental expression of glial fibrillary acidic protein and actin-encoding messages in quaking and control mice

Quaking is a neurological mutation leading to pleiotropic phenotypic expression, the most prominent being disturbed myelin formation in the central nervous system (CNS) with minor abnormalities in the peripheral nervous system. Previous immunochemical measurements of glial fibrillary acidic protein (GFAP) revealed a marked increase in the protein in several areas of the CNS. To further characterize the regulation parameters of GFAP synthesis, we analyzed the levels of GFAP mRNA in 5 regions of the CNS, some with elevated levels of GFAP and some without. This was compared to the developmental expression of GFAP transcripts in the same regions in normal mice. To establish the specificity of the variations observed with this astroglial specific message, we conducted a similar investigation with actin RNA which is expressed by several cell types in the CNS. Both the actin and the GFAP message were found to be increased in the adult mutant throughout the CNS. In 2-year-old normal mice the messengers for both cytoskeleton proteins were expressed in a higher amount than in young adults.

Host response during successful engraftment of fetal xenogenic astrocytes: predominance of microglia and macrophages

Grafting of fetal rabbit brain fragments into the brains of newborn mice results in the successful establishment and migration of xenogenic astrocytes in the majority of recipients. This can be demonstrated by the use of Tp-GFAP1 monoclonal antibody which binds with rabbit, but not with murine glial fibrillary acidic protein. In the first phase, donor astrocytes are found in more than 80% of recipients 3 and 4 weeks after grafting. In the second phase, there is a decline and disappearance of donor astrocytes by the tenth week. We have recently demonstrated that the decline and disappearance of donor astrocytes was co-incident with infiltration of T cells into the brain, compatible with T-cell-mediated graft rejection. In the present studies, we wished to characterize the types of host cells responding during the period of graft success, in the first 4 weeks after transplantation. It was found that responses by microglia, macrophages, and astrocytes occurred promptly and were sustained throughout this period. Host responses occurred at the graft site and at sites of migration. Examination of sham transplanted control mice revealed responses by the same types of cells. No expression of donor Ia antigen was observed, and the expression of Ia antigen by the host was variable and of low magnitude. T cells were rarely present in transplanted brains during this period. Taken together with previous findings, the present studies demonstrate a clear difference in the host response in the brain at the time when xenogenic astrocytes migrate and survive compared to the period when they disappear.(ABSTRACT TRUNCATED AT 250 WORDS)

Migration of xenogenic astrocytes in myelinated tracts: a novel probe for immune responses in white matter

Experimental brain transplantation allows the study of the development of the immune response against brain antigens within the brain itself. This laboratory has developed a transplantation model in which rabbit embryo brain fragments are placed in the brains of newborn mice. The migration of xenogenic astrocytes is traced by a monoclonal antibody which combines with donor but not host glial fibrillary acidic protein. In the first 4 weeks after transplantation, the donor astrocytes successfully migrate, often within myelinated tracts. Following this period, T cells make their appearance and xenogenic astrocytes disappear by 10 weeks. The propensity for clearly identified foreign astrocytes to migrate in myelinated tracts coupled with a well-defined time course of host-vs-graft interaction suggested that the model could be used to study the immune response in white matter. The studies reported here provide sequential examples of the relationship between migration by foreign astrocytes in myelinated tracts and the development of the host immune response. Extensive migration in white matter tracts was first observed in the absence of any T cell response. Subsequently T cells were found at the transplantation site. Finally Ia was found to be expressed on blood vessels and microglia were strongly reactive in white matter that contained T cells but no foreign astrocytes. These observations support the suggestion that the model can be used to more precisely define cellular immune events that occur within white matter.

Migration patterns of donor astrocytes after reciprocal striatum-cerebellum transplantation into newborn hosts

Fragments of striatum or cerebellum from E 25 rabbit embryo were implanted into either the striatum or the mesencephalon of newborn mice. Implanted rabbit astrocytes were selectively identified by monoclonal antibodies to the GFAP which are unable to combine with mouse GFAP. Previous investigations had shown that xenogenic astrocytes have the capacity to migrate in host CNS. The purpose of this study was to compare the patterns of migration of transplant-derived astroglial cells according to the topographic origin of the transplant and location of the grafting site. We found that the migration pattern of the grafted cells from any of both selected sites of implantation was independent from the topographic origin of the transplant. The routes as well as the distances of migration were similar after homo- or heterotopic transplantation. We conclude that astroglial cells or their precursors do not express information which would direct them to move specifically toward a defined region in the host brain according to the region of origin in the donor.

Disappearance of xenogenic astrocytes transplanted into newborn mice is associated with a T-cell response

Following transplantation of fragments of embryonic rabbit brain into the brains of newborn mice, the proportion of mice bearing detectable xenogenic astrocytes increases to over 80% in the first 3-4 weeks. Recent studies have demonstrated that the host response at this time was dominated by non-specific elements of host defense: macrophages, microglia and astrocytes. In the second phase, the proportion of mice bearing xenogenic astrocytes declines rapidly after 4 weeks and reaches zero by 10 weeks. In the present experiments, designed to characterize the host defense during this period, a dramatic increase in the proportion of mice displaying T-cells in the brain in the fourth and fifth weeks after transplantation was found. This corresponded with a marked decline of xenogenic astrocytes. Both subsets of T-cell, helper-inducer (L3T4) and cytotoxic-suppressor (Lyt2), were found, with L3T4 more numerous in many samples. T-cells were found at the site of transplantation and at sites of migration. The division of the host-defense response in this model into a phase of antigen non-specific cells followed by a period when T-cells appear and transplanted astrocytes disappear, should facilitate kinetic studies into the mechanisms of brain-graft rejection.

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.

Short-term post-grafting morphological alterations of glia from an adult brain transplant

Fragments of corpus callosum from adult rabbit have been implanted into the brain of newborn mice. Previous studies had shown that under such conditions transplant-derived astroglial cells differentiate in the host and survive for at least 2 months. The present study was devised to clarify the fate of the differentiated astrocytes present in the adult transplant by using combined ultrastructural and immunohistochemical approaches. These mature cells are shown to degenerate and die within 2 days after the implantation. Therefore, we suggest that stem cells present in adult tissue would account for the surviving population of transplant-derived glial cells.

Developmental expression of myelin proteins by oligodendrocytes in the CNS of trout

Using immunohistochemical techniques, the pattern of cytoplasmic staining and the temporal order of expression of 5 major myelin components of oligodendrocytes were studied in the developing central nervous system of trout. The two myelin glycoproteins, IP1 and IP2, in the cytoplasm of glial cells showed a granular pattern of immunostaining, whereas the 36K protein was homogeneously distributed. Analysis of freshly dissociated cells during early stages of myelinogenesis revealed a constant chronological sequence of expression of myelin proteins by the oligodendrocytes: glycoprotein IP2 was the first protein to appear during glial development together with the galactocerebroside GalC at stage 28 followed by the 36K at stage 30 and finally IP1 at stage 32. The deposition of myelin proteins into the nascent myelin sheath occurred in the same chronological order as their expression by oligodendrocytes. Moreover myelin basic protein, which was not detectable in glial cells, on tissue sections was found to appear in parallel with IP2.

Cerebrospinal myelin basic protein in multiple sclerosis. Identification of two groups of patients with acute exacerbation

The myelin basic protein concentration in the cerebrospinal fluid (CSF) of 125 patients with multiple sclerosis was measured using a radioimmunoassay technique with a detection level of 200 pg/mL and was correlated with the clinical course of the disease. Myelin basic protein was detected in the CSF of some patients with an active progressive form of the disease and in the CSF obtained during exacerbations with the presence of signs or symptoms not previously experienced by the patient (26 of 29 cases were positive during the period of maximal symptoms). Myelin basic protein was not detected in any patient with an inactive or slowly progressive form of the disease, nor in any patient during exacerbations with only recurrence of old signs or symptoms. These results are consistent with the hypothesis that the two clinical forms of exacerbation defined above may be associated respectively with the absence or presence of an acute demyelination.

Absence of correlations between glutamine-synthetase activity and dysmyelination-associated modifications of astroglia in the brain of murine mutants

Glutamine Synthetase (GS) activity was investigated in cerebellum (ce), cerebral cortex (cc), olfactory bulb (ob), and medulla oblongata (mo) of murine dysmyelinating mutants for correlations with modifications of astroglia associated with genetic dysmyelination. One of these mutants, jimpy, develops a strong gliosis throughout the CNS. The other three mutants: shiverer, mld, and quaking, exhibit various astrocytic responses to dysmyelination, but reduced gliosis if any. Comparison between CNS areas in control animals showed a higher GS activity in the olfactory bulb than in the cerebral cortex, medulla, and cerebellum. The developmental patterns of GS activity were similar in mutants and in controls in all four areas investigated. Data on Jimpy suggest that GS activity is not associated with reactive astrocytes.

Are anti-brain antibodies in multiple sclerosis directed to myelin basic protein? Studies employing the Shiverer mouse mutant

The dysmyelinating mouse mutant Shiverer has a severe and relatively selective deficiency of myelin basic protein (MBP) in the central and peripheral nervous system. Nevertheless, Shiverer brain and control-mouse brain showed similar antigenic titers when tested by a complement fixation assay against a panel of 14 multiple sclerosis (MS) sera and 6 MS CSF samples known to represent several specificities of antibrain antibodies. By analogy with experimental allergic encephalomyelitis, a sensitization to MBP has been proposed in MS. Our results, however, show that antibodies to other CNS antigens are quantitatively more important in this disease.

Double ligand ELISA technique for the estimation of antibodies to brain tissue antigens in patients with neurological disorders

A double ligand enzyme-linked immunosorbent assay (ELISA) has been developed to detect antibodies against brain tissue antigens in the sera of patients with neurological diseases. The sera were tested on human white matter homogenate. The technique consists of successive incubations with the human serum to be tested, rabbit immunoglobulin G (IgG) to human immunoglobulins (Ig), alkaline phosphate-labeled protein A and alkaline phosphatase substrate. This procedure has the advantage of increased sensitivity compared to the classical ELISA. Application of this procedure to the sera of patients with neurological diseases showed that the unspecific binding is very low and the results are reliable. Moreover the test allows the detection of antibodies to chemically different antigenic structures that can occur in a variety of neurological diseases.

Immunocytochemical characterization of pulmonary histiocytosis X cells in lung biopsies

Morphologic and immunohistochemical studies were made of open lung biopsies from 9 patients with pulmonary histiocytosis X (HX) and 12 patients with other conditions, and of skin biopsies from patients with cutaneous sarcoidosis, Chester-Erdheim disease, and eruptive histiocytoma. The monoclonal antibody OKT6 was detected with the use of goat anti-mouse IgG labeled with fluorescein (FITC) for light microscopy, and sheep antimouse Fab'2 fragment of IgG labeled with horseradish peroxidase (HRP) for immunoelectron microscopy. The presence of S-100 protein was revealed by an antibody prepared against bovine S-100 protein, using sheep anti-rabbit IgG labeled with FITC for light microscopy and with HRP for immunoelectron microscopy. OKT6 antibody and S-100 protein were detected simultaneously by double labeling with FITC and rhodamine. In all patients with pulmonary HX, the major cellular components (HX cells) of the granulomas showed labeling of the plasma membranes by OKT6 and of the cytoplasm by the anti S-100 protein antibody. The double-labeling technique demonstrated that the same cells carried both reactivities. Immunoelectron microscopy showed that the reactive cells had all the structural characteristics of Langerhans cells, including Langerhans cell granules. Cells reacting with OKT6 showed discrete internal labeling in some of the Langerhans granules, especially those in continuity with the plasma membranes. However, internal labeling of Langerhans granules was not demonstrated in preparations for the localization of S-100 protein. Control samples of sarcoid lesions and other pulmonary lesions unrelated to HX did not show any reactivity except in Langerhans cells; a skin lesion from a patient with eruptive histiocytoma contained OKT6-positive cells which did not have Langerhans granules.

Immunohistochemical localization of myelin basic protein in the developing optic system of trout

Immunofluorescent localization of basic protein (BP) in the CNS of trout was performed using a heterologous antiserum raised against human BP. Bright specific fluorescence was confined to the myelin sheath of axons in most regions of the brain, whereas neuronal pericarya and dendrites as well as glial cells were entirely negative. In the tectum immunofluorescence was characteristically distributed in two rows of horizontally aligned patches, most evidently reflecting the orderly array of myelinated fiber bundles in the stratum opticum and stratum album. During development of the retino-tectal pathway, the appearance of BP followed a distinct rostro-caudal gradient firstly reaching the anterior ventral border of the tectum by larval stage 34. Furthermore, on cross sections through the optic nerve a specifically organized pattern of myelin formation was revealed by immunohistochemistry, which strikingly coincided with the pattern of fiber outgrowth.

Cell-free synthesis of myelin basic proteins in normal and dysmyelinating mutant mice

Total polyribosomes were isolated from the brains of 16-20 day C57BL/6 mice, four neurological mutants (qk/qk, shi/shi, mld/mld, and jp/Y), and four heterozygote or littermate controls (qk/+, shil/+, mld, and jp littermates) and translated in a homologous, cell-free system. No differences were observed among the nine genotypes in either the yield of polysomes (32.2 +/- 0.6 A260/g brain) or in the incorporation of [35S]methionine into trichloroacetic acid-precipitable protein. However, when the four myelin basic proteins (BPs) were isolated from the translation mixtures little incorporation of [35S]methionine into the BPs was noted in those assays directed by polysomes from mld/mld or from shi/shi animals. Compared with C57BL/6 polysomes, mld littermate and shi/+ polysomes incorporated approximately half the levels of label into the four BPs while qk/+ and qk/qk incorporated normal and close-to-normal levels. Polysomes from jp littermates and jp/Y brains synthesized 66% and less than 15% of the levels of the 14K BP compared with C57BL/6 polysomes. Incorporation of label into the other three BPs was normal with jp littermate polysomes and about half the control levels with jp/Y polysomes. The data indicate that shi/shi and mld/mld mutants either produce altered BPs not recognized by our antibody or synthesize very low levels of BP. The data provide additional support for the notion that the qk/qk mutant synthesizes much higher levels of MBP than are incorporated into myelin. They also indicate that in the jimpy mutant the synthesis of the four BPs is affected to differing extents; thus, the mutant cannot be easily characterized as either an "assembly" or "synthesis" defect.

Tamm-Horsfall protein, a kidney marker is expressed on brain sulfogalactosylceramide-positive astroglial structures

The Tamm-Horsfall (TH) glycoprotein and the acidic glycosphingolipid sulfogalactosylceramide (SGC) have a strictly superimposable localization on kidney tissue sections. The fact that SGC is a prevalent glycolipid in mammalian brain, prompted us to look for the presence of TH in the rat central nervous system (CNS). An antiserum raised against human TH was found to react with rat CNS homogenate in the complement fixation assay. This anti-TH antiserum recognized a rat CNS protein having an identical electrophoretical mobility on SDS polyacrylamide gel electrophoresis (PAGE). Indirect immunofluorescence on rat brain tissue sections allowed us to localize this brain TH cross-reacting material to ependymal cells and astrocytic processes such as the Bergmann fibers or astrocytic feet in contact with either the blood vessels or the meninges. All these astroglial structures are also SGC-positive. Since TH and SGC in the kidney are localized on a membrane that possesses an electrogenic Cl-pump, we propose that the astroglial structures which contain these two molecules are also the site of a Cl-transport system.

[Recent data on Schwann cells]

Because of the role they play in the physiopathology of peripheral neuropathies, Schwann cells have been the subject of numerous studies for some ten years. Schwann cells originate in the ectoderm. They migrate along the myelinated and the unmyelinated axons of peripheral nerves, and lie on a basal lamina. They are responsible for the myelination of peripheral nerves; whether the Schwann cell does or does not form a myelin sheath is determined by the type of axon with which it associates. Recent techniques, such as chimaeric quail-chick embryos, biochemical analysis of human peripheral nerve biopsies, Schwann-cell cultures, nerve grafts, mouse mutants, have permitted some progress. The biochemical composition of peripheral myelin is almost completely known. In vitro, Schwann cells can synthesize myelin-specific molecules. Interactions between axons, Schwann-cells and extra-cellular space have been observed.

Myelin basic protein deposition in the optic and sciatic nerves of dysmyelinating mutants quaking, jimpy, Trembler, mld, and shiverer during development

An ontogenetic survey of the basic protein of myelin, common to both central and peripheral nervous systems, was carried out on normal C57Bl and five dysmyelinating mutant mice. Myelin basic protein (MBP) was quantified by radioimmunoassay in the optic and sciatic nerves of mice from birth to adult stages, giving special attention to the premyelinating and early myelination periods. In the optic nerves of normal mice, MBP was already detectable at birth but the active period of myelin deposition was shown to occur after day 10 postnatal. The timing and rate of accumulation of MBP were normal in Trembler. In contrast, they were abnormal in the other mutants. In the quaking mouse, the active period of MBP deposition was delayed, and its final concentration represented no more than 12% of normal in the adult. No active period of MBP deposition was observed in the other mutants. In the jimpy mouse, a slow accumulation of MBP resulted in a final concentration reaching 2% of the normal value at 25 days. In mild and shiverer mice, the MBP was hardly detectable. In the sciatic nerves of normal mice, the active period of MBP deposition occurred between days 3 and 12 postnatal. No substantial changes occurred in the period of 2 months--2 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Myelin in normal and diseased states

A general outline of the morphologic structure and biochemistry of myelin, its mode of development and assembly, and its alterations in diseased states, including diagnoses and prognoses of diseases affecting myelin, is given.

Survival and differentiation of oligodendrocytes from neural tissue transplanted into new-born mouse brain

Fragments of new-born mouse central nervous system have been transplanted into new-born mice host brains, under conditions in which the myelin synthesized by the oligodendrocytes included in the graft, could be distinguished from the host myelin. The work demonstrates that transplanted oligodendrocytes survive in the host brain, migrate out of the graft and synthesize myelin. No sign of rejection was observed during the time of the experiment.

[Prognostic value of gliofibrillary protein assay in malignant gliomas treated with chemo- and radiotherapy]

The value of GFA determination for predicting the survival of patients after surgical treatment of a malignant brain tumor was studied. GFA was measured on a histologically controlled fragment of the tumor. No significant correlation was found between the level of GFA and the survival time of patients treated by chemotherapy and radiotherapy.

Transplantation of CNS fragments into the brain of shiverer mutant mice: extensive myelination by implanted oligodendrocytes. I. Immunohistochemical studies

Solid fragments of olfactory bulb from new-born normal (B6CBA and C57BL6) mice were implanted into new-born shiverer (shi/shi) brains. The shiverer mouse being characterized by the absence of myelin basic protein (MBP), myelination due to implanted oligodendrocytes can be detected in the shiverer brain using an antiserum anti-MBP. Observation of sagittal sections of the host brains revealed very extensive areas of normal myelination from the level of the graft (rostral thalamus) up to the caudal brain (diencephalon, cerebellum, pons). Thus, oligodendrocytes contained in the implant migrate out of the graft over long distances in the host brain, before they differentiate and synthesize myelin. These results raise the question of the behaviour of oligodendrocytes in normal development.

Myelin basic protein in CSF and blood. Relationship between its presence and the occurrence of a destructive process in the brains of encephalitic patients

Serum and CSF levels of myelin basic protein (MBP) were measured in 50 patients with encephalitis of various origins and severity. In nearly 50%, the CSF samples were found to display immunoreactivity of MBP. Positivity was found to be correlated with the severity of the clinical signs. More precisely, it corresponded to cases with suspected extensive brain destruction. No relationship could be observed with the cause of disease. Positive tests of sera were infrequent, even from patients whose CSF was rich in MBP. Longitudinal studies performed on 20 patients who were serially investigated during periods ranging from three weeks to 18 months demonstrated that after an attack, MBP liberation into the CSF persists for one to three weeks. The MBP assay should serve as an index for destruction of nervous tissue.

Similarities and dissimilarities between two myelin deficient mutant mice, Shiverer and mld

In the brain of Shiverer and mld mutant mice, myelin is poorly compacted and the major dense line of the myelin is practically missing. Major biochemical differences were detected between mutations. In mld myelin, myelin basic proteins are mainly affected and 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNP) exhibits a very high specific activity. In Shiverer myelin, in addition to basic proteins, all major myelin proteins are also decreased while CNP specific activity is moderately increased.

[Evaluation of the degree of malignancy of human gliomas by means of the determination of their GFA content (author's transl)]

The quantitative immunochemical determination of the GFA protein in a large number of brain tumors has shown a correlation between the malignancy of a glioma and its content in GFA. This dosage should help to establish the diagnosis, in addition to routine histological examinations. Its prognostic interest is currently debated.

Regional distribution of myelin basic protein in the central nervous system of quaking, jimpy, and normal mice during development and aging

Myelin basic protein (MBP) was quantified using a RIA technique in the spinal cord, cerebellum, diencephalon plus brainstem region and cerebral hemispheres of two dysmyelinating murine mutants, quaking (qk) and jimpy (jp) mice. Comparison was made with normal control values. The whole life-span has been investigated: ie, ages ranging from 0 to 26 days for the jp, O to one year for the qk, and prenatal stage to three years for the control animals. Assays in the mutants at early ages were rendered feasible by the use of marker genes, which has allowed the diagnosis of the mutation at birth, 12 days before the expression of their typical tremor phenotype. Special care was given to the period of early myelinogenesis in order to clarify the dysynchrony between the various parts of the central nervous system. In normal mice, MBP was already detected in the brain of 19-day-old embryos. During development, rapid accumulation of MBP first occurred in the spinal cord then in the diencephalon, the brainstem, the cerebellum, and finally in the cerebral hemispheres. In the 25-day-old jimpy mutant, levels of MBP were found dramatically decreased, never exceeding 6% of the normal controls in any of the areas investigated. The situation for the quaking mouse was quite different. This mutant could be investigated up to one year old. At that age, a high discrepancy was observed between the values found in the brain and in the spinal cord (respectively, 10% and 35%) compared to normal controls. In both mutants, not only were the levels of MBP decreased, but also its appearance during development was delayed. Nevertheless, in both mutants the caudo-rostral timing of myelination as assayed by MBP levels was maintained. Furthermore, the later myelination occurred, the stronger weas the deficit in MBP. Interestingly, in the quaking mutant, the specific plasticity of the spinal cord was exemplified by its ability to reduce constantly, even at an advanced age, its initial deficit of MBP.