The relationship between enzyme activity and neuroglia in plaques of multiple sclerosis

Cerebral ependymoma in a patient with multiple sclerosis case report and critical review of the literature

BACKGROUND

The concurrence of multiple sclerosis (MS) and brain tumors is a rare but well-recognized condition. The radiologic evidence of the progressive evolution of a mega-plaque in a tumor has never been described. We report the first case of such an occurrence.

METHODS

A 27-year-old woman with a diagnosis of MS was referred to us for an intense frontal headache. Magnetic resonance imaging showed a mass lesion in correspondence of a black hole lesion previously diagnosed. The patient was operated on, with complete removal of the tumor documented by an intraoperative MRI. The histologic examination evidenced an ependymoma. Postoperative radiotherapy was performed.

RESULTS

The patient is well and recurrence-free at 2 years follow-up.

CONCLUSIONS

The present case, documenting the transformation of a mega-plaque into a tumor, suggests a cause-effect relationship between MS and brain tumors.

Oligodendroglioma and multiple sclerosis. A case report

BACKGROUND

The concurrence of multiple sclerosis (MS) and glioma is uncommon. Approximately 30 cases have been reported, but in only six of them the tumour was pure or mixed oligodendroglioma. The appearance of new neurological symptoms and signs in a patient with multiple sclerosis is usually attributed to a relapse of this disease and neuroradiological studies are not always performed. When done, the finding of a new focal mass lesion is usually interpreted as a pseudotumoural plaque.

CASE REPORT

A 37-year-old man was admitted because of partial simple seizures and an enlarging intracranial mass. He had been diagnosed of MS eleven years earlier. A MRI study performed eight years before admission showed a large mass in the right frontal lobe which was thought to be a pseudotumoural plaque. Two years later, he developed simple partial motor seizures that were initially controlled with valproic acid. He remained well until three months before admission, when seizures reappeared with a poor response to valproic acid. A new MRI study showed an heterogeneous right frontal enlarging mass lesion. A primary neoplasm was suspected and a subtotal removal was performed. The pathological diagnosis was oligodendroglioma with a periferic demyelinating area.

CONCLUSION

Atypical MRI lesions in a patient with MS must be carefully interpreted. Pseudotumoural plaques have been described both clinically and radiologically to be hardly distinguishable from a tumoural lesion and histological confirmation is often required. The association between MS and glioma is uncommon but it must be kept in mind when a mass lesion develops in a patient with MS.

Stimulation of in vitro myelin synthesis by microglia

Central nervous system myelin is elaborated by oligodendrocytes, which have been studied extensively in cell culture. Dissociated brain cultures allow in vitro analysis of events in myelinogenesis, including cell-cell interactions. Microglia, the primary phagocytic cell of the central nervous system, appear in developing fiber tracts prior to the onset of myelination in vivo. To gain insight into potential oligodendrocyte-microglial interactions during development, these cells were co-cultured and various parameters of myelin synthesis were measured. In co-culture, microglia stimulated the synthesis of sulfatide, a myelin-specific galactolipid, in oligodendrocytes, as well as the expression of the myelin-specific proteins myelin basic protein and proteolipid protein. Activity of the oligodendrocyte cytoplasm-specific enzyme 2',3'-cyclic nucleotide 3'-phosphohydrolase was not elevated, suggesting that the effects of microglia were not due to stimulation of oligodendrocyte proliferation. This was confirmed by the inability of microglia to induce significant DNA synthesis. Conditioned medium from cultured microglia provided a similar stimulatory activity, suggesting that the increase in myelin synthesis does not require contact between oligodendrocytes and microglia. These findings suggest a stimulatory role for microglia during myelinogenesis.

Oligodendrocyte reactions and cell proliferation markers in human demyelinating diseases

We have carried out immunocytochemical reactions using antibodies to markers of oligodendrocytes, astrocytes, microglia and proliferating cells (PCNA) in sections of human brain in a variety of demyelinating conditions and human immunodeficiency virus (HIV) infection. In the acute phases of demyelinating diseases we found marked reactive changes in oligodendrocytes with hyperplasia and an increased cytoplasmic reaction using antibodies to enzymes involved in myelin formation. Proliferative responses were implied by the hyperplasia and the common finding of clusters of two or three adjacent oligodendrocytes at sites of acute myelin damage. This was borne out by studies using the PCNA antibody which gave negative reactions in normal brain but positive reactions in acute demyelination. Double staining for PCNA and cell markers showed that cells that had entered the cell proliferation cycle were to be found among astrocytes, microglia/macrophages and oligodendrocytes. In chronic demyelinating conditions, numbers of oligodendrocytes were reduced and cells in the proliferative cycle were not present, suggesting that the reactive potential of oligodendrocytes or their precursors and their capacity to respond to demyelination is limited.

Oligodendrocytes in the early course of multiple sclerosis

The neuropathology of demyelinating lesions in multiple sclerosis was studied in specimens obtained by diagnostic needle biopsy during early stages of the disease. The lesions were characterized by a chronic inflammatory reaction dominated by lymphocytes and macrophages, plaque-like demyelination, and astroglial sclerosis. Oligodendrocytes within the lesions were studied by immunocytochemistry using antibodies against various myelin and oligodendroglia components. The expression of messenger RNA for proteolipid protein was determined by in situ hybridization. Our studies revealed that myelin-oligodendrocyte glycoprotein is a sensitive and reliable marker for identification of oligodendrocytes in demyelinated plaques. The results suggest that in the early course of the disease in some patients, oligodendrocytes may largely be preserved, whereas in others oligodendroglial loss is pronounced. Loss of oligodendrocytes was only marginally related to the stage of demyelinating activity within the lesions. These findings indicate that the pathogenesis of demyelination may vary within different multiple sclerosis patients.

Multiple sclerosis: remyelination of nascent lesions

The relationship between plaque pathology and disease duration was examined in 15 patients with multiple sclerosis who died early in the course of their illness. Myelin-stained sections revealed that most plaques examined in patients who died during the first month of their illness showed evidence of ongoing myelin destruction accompanied by a loss of oligodendrocytes. Plaques containing large numbers of oligodendrocytes were not observed in these patients, but were relatively common in patients who died more than 1 month after clinical onset. Remyelination affecting more than 10% of the plaque area was observed in 3 of 82 plaques in 5 patients who died within 10 weeks of clinical onset, in 38 of 105 plaques in 5 patients who died 3 to 10 months after clinical onset, and in 19 of 92 plaques in 5 patients who died 18 months or longer after clinical onset. The study provides new evidence that both oligodendrocytes and myelin are destroyed in new lesions, that this activity ceases completely in many lesions within a few weeks, and that remyelination frequently ensues following repopulation of the plaque by oligodendrocytes. The findings suggest that new lesions normally remyelinate unless interrupted by recurrent activity and that remyelinated shadow plaques are the outcome of a single previous episode of focal demyelination.

Pathology, histochemistry and immunocytochemistry of lesions in acute multiple sclerosis

Twenty cases of acute or early multiple sclerosis have been examined using staining, histochemical or immunocytochemical methods. They had died within 6 months after initial clinical onset (12) or commencement of an "anatomically-remote" acute relapse (8). Plaques in these acute cases showed the following characteristics: lymphocytic perivascular infiltration, plaque hypercellularity, plaque macrophage infiltration and intra-macrophage myelin debris. In most cases of clinical duration of less than 12 weeks, some macrophages showed characteristic formaldehyde-resistant markers for haematogenous macrophages (muramidase, anti-alpha 11-antitrypsin, MAC and HAM56) but, with the exception of the last, these markers subsequently declined indicating a haematogenous origin for macrophages in the early lesion. Lymphocytes were prominent in perivascular (perivenous) regions but, except in one case, were only scanty in or at the demyelinating edge of plaques. Oligodendroglial hyperplasia, indicative of remyelinating activity, was seen at the edge of plaques in one quarter of these acute cases (7 times the rate seen in chronic lesions). Astrocytic activation was not apparent in the earliest stages but was usually seen from about 6 weeks onwards. The conclusion from these observations is that the prime inflammatory process is around blood vessels with usually only scanty initial inflammatory activity in the parenchyma of the brain. Macrophages emigrating from blood vessels digest myelin either as a response to inflammatory damage to the myelin or as a response to activation signals produced in either the perivascular region or plaque.

Growth of human oligodendrocytes in vitro on extracellular matrix

Based on the successful use of a basement membrane-like extracellular matrix (ECM) as a physiological substrate for the growth of adult rat oligodendrocytes, we have applied the system to oligodendroglia of human origin. ECM is excreted and deposited on a culture dish by endothelia cells. Glial cells isolated from fresh human brains by a Percoll density gradient were maintained on ECM for several weeks in vitro. Cells identified as oligodendrocytes by anti-galactocerebroside (GalC) could be transferred and replated on ECM-coated plates. In one case, GalC-positive cells isolated from a biopsy of an 8-year old girl were able to incorporate [3H]thymidine as revealed by autoradiography. ECM can be used successfully for the growth and in vitro maintenance of human oligodendrocytes.

Continual breakdown and regeneration of myelin in progressive multiple sclerosis plaques

Plaques with lipid macrophages and macrophages containing undigested myelin fragments from five multiple sclerosis patients were studied by light microscopy of epoxy-embedded tissue (five cases) and electron microscopy (one case). Cell counts determined electron microscopically revealed that oligodendrocytes were reduced in number in areas of commencing myelin breakdown. The major mechanism of myelin destruction was phagocytosis by macrophages of intact myelin sheaths in the presence of very small numbers of lymphocytes and plasma cells. When plaques were orientated to allow examination of whole myelin internodes, it was found that most lesions, including lesions known to have been present for less than ten months, contained remyelinating internodes, sometimes in numbers large enough to form shadow plaques. It is concluded that the two processes of sometimes massive remyelination and active demyelination frequently coexist in "fatty" subacute plaques filled with lipid-containing macrophages, and that myelin breakdown at the edges of progressive lesions includes destruction of remyelinating internodes.

Adult rat oligodendrocytes grown in vitro upon an extracellular matrix have the ability to proliferate

The use of extracellular matrix (ECM) as a natural substrate for cell culture has markedly improved the growth and morphological differentiation of isolated adult rat oligodendrocytes. ECM-grown oligodendrocytes exhibited cyclic nucleotide phosphodiesterase (CNP)-activity which increased with time in culture and network formation. As much as 50-70% of the cells incorporated [3H]thymidine as visualized by the high labeling index of galactocerebroside (GalC)-positive cells. Chemical and enzymatic modifications of the ECM suggested that laminin in conjunction with other ECM constituents, plays a role in the induction of proliferation and/or differentiation responses in mature oligodendrocytes.

Survival of oligodendrocytes in chronic relapsing experimental autoimmune encephalomyelitis

Demyelinated plaques of chronic relapsing experimental autoimmune encephalomyelitis (EAE) have been examined in Strain 13 guinea pigs. Oligodendrocytes could be identified within these lesions adjacent to naked axons and astrocytic processes. Oligodendrocytes were identified both ultrastructurally and immunocytochemically. Many of these cells showed bizarre shapes and myelin within their cytoplasm. The survival of oligodendrocytes within these lesions suggests that the myelin sheath, not the oligodendrocyte, is the primary target in autoimmune demyelination. A similar sequence of events has been proposed in multiple sclerosis, for which chronic relapsing EAE serves as a laboratory model. The persistence of myelinating cells in areas of chronic demyelination and gliosis might have significant reparatory implications.

Chronic relapsing experimental allergic encephalomyelitis: its value as an experimental model for multiple sclerosis

Comparison of the pathohistology of chronic relapsing experimental allergic encephalomyelitis (CR-EAE) and multiple sclerosis (MS) reveals a close similarity. Thus, CR-EAE appears to be a valuable model for the study of pathogenetic factors leading to the formation of MS lesions, although the induction of the disease may be different (active sensitization with CNS antigens and adjuvant in CR-EAE versus unknown etiology in MS). CR-EAE furthermore mimicks the pathohistological patterns of other related human inflammatory demyelinating diseases (i.e., acute perivenous leukoencephalomyelitis and acute hemorrhagic leukoencephalomyelitis). The expression of an acute, predominantly inflammatory versus chronic inflammatory demyelinating disease in this model depends upon the time interval between sensitization and sampling of the animals. Recent evidence is discussed that a cooperation between cellular and humoral immune mechanisms, directed against multiple CNS antigens, is responsible for the formation of large demyelinated plaques in EAE and MS.

Abnormal glutamic acid metabolism in multiple sclerosis

We have found extensive amino acid abnormalities in multiple sclerosis sera. The most consistent abnormality is an elevation in serum glutamate, which is most striking during relapses. The increase in glutamate in the patients does not occur sharply during the onset of the relapse. Instead it appears to rise gradually within a month or two prior to the onset of the clinical relapse, to reach a peak during the relapse and then to slowly decline.

Observations on remyelination in the rabbit spinal cord following demyelination induced by lysolecithin

The extent and type of remyelination that occurred following demyelination induced by intraspinal injection of small volumes of lysolecithin was examined in 24 rabbits. Unlike the rat and cat following this procedure remyelination is not complete even after 6 months' survival and little Schwann cell invasion occurs. The cellular environment around remyelinated and persistently demyelinated axons differed. Remyelination was associated with a good astrocytic presence and removal of myelin debris, while persistently demyelinated axons were surrounded by myelin debris and a poor astrocytic presence. It was conluded that the environment around the demyelinated axon influences oligodendrocyte remyelination.

Regeneration of oligodendroglia during recovery from demyelinating disease

Infection of mice with the JHM strain of mouse hepatitis virus causes demyelination as a result of a cytolytic infection of oligodendroglia. In recovery, animals show remyelination, which could result either from surviving oligodendrocytes extending their territory or by generation of new oligodendroglia. Electron microscopic autoradiographic studies with 3H-labeled thymidine demonstrate that the cells associated with remyelination are newly generated oligodendroglia.

Pathology of the early lesion in multiple sclerosis

Ideas concerning the nature of multiple sclerosis continue to be strongly influenced by the unusual morphology of the disease. A review of classic histology studies, however, reveals that there is less agreement than might be supposed concerning several important histiological features of the early lesion. Electron microscopy of brain biopsies, of immersion fixed autopsy tissue and of autopsy tissue fixed by early in situ brain perfusion suggests that the mechanism of demyelination in multiple sclerosis may be an unusual one that involves a progressive reduction in the number of myelin lamellae around nerve fibers in the vicinity of cells of uncertain origin that contain filamentous and multilamellated cytoplasmic inclusions unlike the usual pleomorphic inclusions seen in myelin phagocytes. Lymphocytes are not directly involved in this process but are observed to contact the inclusion material following its delivery to the Virchow-Robin spaces. The putative neurogenic or viral antigen in multiple sclerosis may be contained in this material. The occurrence of filamentous nuclei in early lesions fixed by immersion is an unrelated phenomenon, which may be an autolytic or drug induced artifact although this has not yet been established.

The onset and progression of the lesion in multiple sclerosis

The active established plaque in multiple sclerosis is characterized by hypercellularity at its edge and lipid phagocytosis (gitter cells). The hyperactive early plaque shows cells throughout the lesion. Active plaques seems to extend at their edges; proteolysis of myelin basic protein is perhaps an important factor in the myelin breakdown at the rim of these lesions. The hyperactive early plaque usually shows infiltration with monocytes, lymphocytes and plasma cells around its central vein. The phagocytic element is presumably a response to myelin breakdown but the significance of the lymphocytes in these lesions in uncertain. Perivenular infiltrates that are predominantly composed of lymphocytes are seen around veins and venules in the vicinity of established lesions in some patients who died during an acute episode...

Concurrence of multiple sclerosis and glioma

Three cases are reported of concurrence of malignant gliomas (astrocytomas and glioblastomas) with multiple sclerosis (MS). This situation may lead to considerable diagnostic difficulties, yet an accurate appraisal is of prognostic, if not therapeutic, value. There is suggestive but inconclusive evidence that the two conditions may be causally related, malignant astrocytic tumours arising from plaques of MS. The small number of reported cases makes statistical analysis impossible, but the scanty literature may not reflect the true incidence.

Histochemistry of enzyme response to trauma in the neocortex and corpus callosum of developing rat brain

The enzyme response to injury of the brain was well localized and limited. Some enzymes, even in 12 day old brain, increased rapidly, mainly in neocortical glial cells. In the corpus callosum enzymes were not significantly hyperactive before the light myelination stage. Some hyperactivity declined after 21 days. Oxidative processes and phosphate metabolism were most disturbed.

HISTOCHEMISTRY OF THE NEUROGLIA AND MYELIN IN EXPERIMENTAL CEREBRAL OEDEMA

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THE RELATIONSHIP BETWEEN ENZYME ACTIVITY AND NEUROGLIA IN THE PRODROMAL AND DEMYELINATING STAGES OF CYANIDE ENCEPHALOPATHY IN THE RAT

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