Objective
Multiple sclerosis (MS) is a demyelinating disease of the central nervous system, leading to memory impairment in up to 65% of patients. Memory dysfunction in MS has been associated with ...loss of synapses in the hippocampus, but its molecular basis is unknown. Accumulating evidence suggests that components of the complement system, C1q and C3, can mediate elimination of synapses.
Methods
To investigate the involvement of complement in synaptic changes in MS, gene and protein expression and localization of C1q and C3 were analyzed in relation to neuropathological changes in myelinated and demyelinated hippocampi from postmortem MS brains. Findings were compared to hippocampi of Alzheimer disease (AD) and non‐neurological controls.
Results
C1q expression and C3 activation were increased in myelinated and demyelinated MS hippocampi, mainly in the CA3/2 and CA1 subfields, which also showed a marked decrease in synaptic density and increased neuronal staining for the mitochondrial heat shock protein 70 (mtHSP70) stress marker. Neurons were the major source of C1q mRNA. C1q protein and activated C3 localized at synapses within human leukocyte antigen–positive cell processes and lysosomes, suggesting engulfment of complement‐tagged synapses by microglia. A significant association (p < 0.0001) between the density of C1q and synaptophysin‐positive synapses or mtHSP70 was seen in myelinated MS hippocampi, further pointing toward a link between the complement pathway and synaptic changes. In contrast to AD, MS hippocampi were consistently negative for the terminal complement activation complex C5b9.
Interpretation
These data support a role for the C1q‐C3 complement axis in synaptic alterations in the MS hippocampus. Ann Neurol 2015;77:1007–1026
Abstract In Alzheimer's disease (AD), amyloid plaques are surrounded by reactive astrocytes with an increased expression of intermediate filaments including glial fibrillary acidic protein (GFAP). ...Different GFAP isoforms have been identified that are differentially expressed by specific subpopulations of astrocytes and that impose different properties to the intermediate filament network. We studied transcript levels and protein expression patterns of all known GFAP isoforms in human hippocampal AD tissue at different stages of the disease. Ten different transcripts for GFAP isoforms were detected at different abundancies. Transcript levels of most isoforms increased with AD progression. GFAPδ-immunopositive astrocytes were observed in subgranular zone, hilus, and stratum–lacunosum–moleculare. GFAPδ-positive cells also stained for GFAPα. In AD donors, astrocytes near plaques displayed increased staining of both GFAPα and GFAPδ. The reading-frame–shifted isoform, GFAP+1 , staining was confined to a subset of astrocytes with long processes, and their number increased in the course of AD. In conclusion, the various GFAP isoforms show differential transcript levels and are upregulated in a concerted manner in AD. The GFAP+1 isoform defines a unique subset of astrocytes, with numbers increasing with AD progression. These data indicate the need for future exploration of underlying mechanisms concerning the functions of GFAPδ and GFAP+1 isoforms in astrocytes and their possible role in AD pathology.
Microglial clusters with C3d deposits are observed in the periplaque of multiple sclerosis (MS) brains and were proposed as early stage of lesion formation. As such they should appear in the brain of ...MS donors with acute disease but thus far this has not been shown. Using postmortem brain tissue from acute (n = 10) and chronic (n = 15) MS cases we investigated whether C3d+ microglial clusters are part of an acute attack against myelinated axons, which could have implications for disease pathogenesis. The specificity of our findings to MS was tested in ischemic stroke cases (n = 8) with initial or advanced lesions and further analyzed in experimental traumatic brain injury (TBI, n = 26), as both conditions are primarily nondemyelinating but share essential features of neurodegeneration with MS lesions. C3d+ microglial clusters were found in chronic but not acute MS. They were not associated with antibody deposits or terminal complement activation. They were linked to slowly expanding lesions, localized on axons with impaired transport and associated with neuronal C3 production. C3d+ microglial clusters were not specific to MS as they were also found in stroke and experimental TBI. We conclude that C3d+ microglial clusters in MS are not part of an acute attack against myelinated axons. As such it is unlikely that they drive formation of new lesions but could represent a physiological mechanism to remove irreversibly damaged axons in chronic disease. GLIA 2017;65:264–277
Main Points
C3d+ microglial clusters occur in chronic but not acute MS.
They are not specific to MS, occur on injured axons and are associated with neuronal C3 production.
They likely represent a physiological mechanism to remove irreversibly damaged axons.
In brain tissues from multiple sclerosis (MS) patients, clusters of activated HLA-DR-expressing microglia, also referred to as preactive lesions, are located throughout the normal-appearing white ...matter. The aim of this study was to gain more insight into the frequency, distribution and cellular architecture of preactive lesions using a large cohort of well-characterized MS brain samples.
Here, we document the frequency of preactive lesions and their association with distinct white matter lesions in a cohort of 21 MS patients. Immunohistochemistry was used to gain further insight into the cellular and molecular composition of preactive lesions.
Preactive lesions were observed in a majority of MS patients (67%) irrespective of disease duration, gender or subtype of disease. Microglial clusters were predominantly observed in the vicinity of active demyelinating lesions and are not associated with T cell infiltrates, axonal alterations, activated astrocytes or blood-brain barrier disruption. Microglia in preactive lesions consistently express interleukin-10 and TNF-α, but not interleukin-4, whereas matrix metalloproteases-2 and -9 are virtually absent in microglial nodules. Interestingly, key subunits of the free-radical-generating enzyme NADPH oxidase-2 were abundantly expressed in microglial clusters.
The high frequency of preactive lesions suggests that it is unlikely that most of them will progress into full-blown demyelinating lesions. Preactive lesions are not associated with blood-brain barrier disruption, suggesting that an intrinsic trigger of innate immune activation, rather than extrinsic factors crossing a damaged blood-brain barrier, induces the formation of clusters of activated microglia.
Cortical lesions (CLs) are an important component of multiple sclerosis (MS) pathology; they correlate better with physical disability and cognitive impairment than white matter lesions (WMLs). ...Because remyelination can be extensive in CLs, we quantified remyelination in gray matter (GM) and white matter (WM), addressing oligodendrocyte (OGD) maturation state and clinical relevance of remyelination. Brain tissue samples from 21 chronic MS patients were immunohistochemically stained for myelin proteolipid protein, Olig2, which is strongly expressed in OGD precursor cells (OPCs), but weakly expressed in mature OGDs and other OGD markers. Sections were scored for the presence of normal-appearing WM and GM, de- and remyelination, and OPC and OGD cell counts. Remyelination was significantly more extensive in CLs than in WMLs with a trend toward more GM remyelination in primary progressive MS (PPMS) vs relapse-onset MS patients. More OPCs were found in remyelinated and nonremyelinated CLs vs remyelinated WMLs and nonremyelinated WMLs. Thus, there is more remyelination in the GM than in the WM in MS patient brains, with a trend toward more remyelination in those with PPMS. There does not seem to be a significant OPC recruitment failure in the GM, which casts new light on the process of remyelination failure.
Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS). Microarray‐based global gene expression profiling is a promising method, used to study potential genes involved ...in the pathogenesis of the disease. In the present study, we have examined global gene expression in normal‐appearing gray matter and gray matter lesions from the cortex of MS patients, and compared them with cortical gray matter samples from controls. We observed a massive upregulation of immunoglobulin (Ig)‐related genes in cortical sections of MS patients. Using immunohistochemistry, the activation of Ig genes seems to occur within plasma cells in the meninges. As synthesis of oligoclonal IgGs has been hypothesized to be caused by the activation of Epstein–Barr virus (EBV)‐infected B‐cells, we screened the brain samples for the presence of EBV by real‐time quantitative polymerase chain reaction (qPCR) and immunohistochemistry, but no evidence of active or latent EBV infection was detected. This study demonstrates that genes involved in the synthesis of Igs are upregulated in MS patients and that this activation is caused by a small number of meningeal plasma cells that are not infected by EBV. The findings indicate that the Ig‐producing B‐cells found in the cerebrospinal fluid (CSF) of MS patients could have meningeal origin.
Hippocampal pathology was shown to be extensive in multiple sclerosis (MS) and is associated with memory impairment. In this post-mortem study, we investigated hippocampal tissue from MS and ...Alzheimer’s disease (AD) patients and compared these to non-neurological controls. By means of biochemical assessment, (immuno)histochemistry and western blot analyses, we detected substantial alterations in the cholinergic neurotransmitter system in the MS hippocampus, which were different from those in AD hippocampus. In MS hippocampus, activity and protein expression of choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme, was decreased, while the activity and protein expression of acetylcholinesterase (AChE), the acetylcholine degrading enzyme, was found to be unaltered. In contrast, in AD hippocampus both ChAT and AChE enzyme activity and protein expression was decreased. Our findings reveal an MS-specific cholinergic imbalance in the hippocampus, which may be instrumental in terms of future treatment options for memory problems in this disease.
Here we present the case of a 28-year-old man with X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection and neoplasia (XMEN) disease. He presented with immune ...thrombocytopenia within 1 year after successful autologous hematopoietic stem cell transplantation for recurrent EBV-associated classical Hodgkin lymphoma (CHL). The combination of EBV- associated malignancy, autoimmunity, recurrent airway infections at young age and bronchiectasis, prompted immunological investigation for an inborn error of immunity (IEI). Genetic testing revealed XMEN disease. XMEN disease is characterized by a glycosylation defect due to mutations in the MAGT1 gene. Germline mutations in the MAGT1 gene disrupt glycosylation of the NKG2D receptor in immune cells, including natural killer and CD8-positive T cells, vital for immune surveillance, especially against EBV. Consequently, individuals with XMEN disease, are prone to EBV-associated lymphoproliferative disorders in addition to auto-immunity. Early recognition of adult onset IEI-related B-lymphoproliferative disorders, including CHL is of vital importance for treatment decisions, including (allogeneic) haematopoietic stem cell transplantation and family screening.
Background: Cortical lesions (CLs) occur frequently in multiple sclerosis (MS), but only few CLs are observed on conventional magnetic resonance imaging (MRI). Why some CLs are visible and others are ...not is currently unknown. Here, we investigated whether CLs that are visible on conventional MRI differ from MRI-invisible CLs in terms of underlying histopathology and quantitative MRI (qMRI) measures.
Methods: A total of 16 brain slices from 10 patients with chronic MS were analysed histopathologically and with conventional and qMRI. A region-of-interest approach was used to compare MRI-visible CLs with MRI-invisible CLs.
Results: Although under-powering cannot be completely excluded in this study, MRI-visible CLs did not seem to differ from MRI-invisible CLs in terms of histopathology or qMRI measures. They were, however, significantly larger than their invisible counterparts (mean 13.3 ± 1.7 mm2 versus 6.9 ± 1.3 mm2; p = 0.001). Furthermore, the number of MRI-visible lesions correlated with the overall number of CLs in the brain slice (r = 0.96, p < 0.01) and with the overall percentage of demyelination (r = 0.78, p < 0.01) per hemispheric brain slice.
Conclusion: MRI visibility of CLs is determined by lesion size, and not by any distinctive underlying pathology. Visible CLs are associated with a higher total cortical lesion load, which suggests that when CLs in patients with MS become detectable on MRI, they merely represent ‘the tip of the pathological iceberg’.
Autopsy cases show that cortical lesions (CLs) in multiple sclerosis (MS) lack lymphocyte/macrophage influx, blood-brain barrier breakdown, and complement activation. However, some CLs were ...demonstrated to harbor activated microglia. Here, we assessed the clinical significance of microglia activation in CLs in a large autopsy sample, and we investigated possible interrelationships with other pathologic characteristics.
We cross-sectionally investigated the clinicopathologic characteristics of 22 patients with MS with extensive subpial demyelination (CL group) and 19 patients with MS with only little demyelination of the cerebral cortex (non-CL group).
A subset of the patients in the CL group (12 patients) showed rims of activated microglia (RAM) at the border of the CLs (RAM-CL group), whereas the other 10 patients in this group did not show microglia activation (non-RAM-CL group). A subsequent comparison between groups showed that patients with MS harboring RAM-CLs were significantly younger at the time of their death (53.5 years) than patients harboring mainly non-RAM-CLs (68.7 years; p < 0.05) or patients without extensive numbers of CLs (66.9 years; p < 0.01). In addition, a significantly shorter disease duration was found for the RAM-CL group (mean 20.9 years) than for the non-CL group (mean 34.5 years; p < 0.05). We also found that the presence of RAM-CLs is associated with a higher number of chronic active white matter (WM) lesions (Spearman ρ = 0.74; p < 0.0001).
RAM-CLs were found in a subset of patients with MS who also have more active WM inflammation and a less favorable disease course.
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