Regionally diverse astrocyte subtypes and their heterogeneous response to EAE

Astrocytes fulfil many functions in the central nervous system (CNS), including contribution to the blood brain barrier, synapse formation, and trophic support. In addition, they can mount an inflammatory response and are heterogeneous in morphology and function. To extensively characterize astrocyte subtypes, we FACS-isolated and gene expression profiled distinct astrocyte subtypes from three central nervous system regions; forebrain, hindbrain and spinal cord. Astrocyte subpopulations were separated based on GLAST/SLC1A3 and ACSA-2/ATP1B2 cell surface expression. The local brain environment proved key in establishing different transcriptional programs in astrocyte subtypes. Transcriptional differences between subtypes were also apparent in experimental autoimmune encephalomyelitis (EAE) mice, where these astrocyte subtypes showed distinct responses. While gene expression signatures associated with blood-brain barrier maintenance were lost, signatures involved in neuroinflammation and neurotoxicity were increased in spinal cord astrocytes, especially during acute disease stages. In chronic stages of EAE, this reactive astrocyte signature was slightly decreased, while obtaining a more proliferative profile, which might be relevant for glia scar formation and tissue regeneration. Morphological heterogeneity of astrocytes previously indicated the presence of astrocyte subtypes, and here we show diversity based on transcriptome variation associated with brain regions and differential responsiveness to a neuroinflammatory insult (EAE)

Characterizing microglial gene expression in a model of secondary progressive multiple sclerosis

Multiple sclerosis (MS) is the most common inflammatory, demyelinating and neurodegenerative disease of the central nervous system in young adults. Chronic-relapsing experimental autoimmune encephalomyelitis (crEAE) in Biozzi ABH mice is an experimental model of MS. This crEAE model is characterized by an acute phase with severe neurological disability, followed by remission of disease, relapse of neurological disease and remission that eventually results in a chronic progressive phase that mimics the secondary progressive phase (SPEAE) of MS. In both MS and SPEAE, the role of microglia is poorly defined. We used a crEAE model to characterize microglia in the different phases of crEAE phases using morphometric and RNA sequencing analyses. At the initial, acute inflammation phase, microglia acquired a pro-inflammatory phenotype. At the remission phase, expression of standard immune activation genes was decreased while expression of genes associated with lipid metabolism and tissue remodeling were increased. Chronic phase microglia partially regain inflammatory gene sets and increase expression of genes associated with proliferation. Together, the data presented here indicate that microglia obtain different features at different stages of crEAE and a particularly mixed phenotype in the chronic stage. Understanding the properties of microglia that are present at the chronic phase of EAE will help to understand the role of microglia in secondary progressive MS, to better aid the development of therapies for this phase of the disease

HSPA1A-Independent Suppression of PARK2 C289G Protein Aggregation by Human Small Heat Shock Proteins

The C289G mutation of the parkin E3-ubiquitin protein ligase (PARK2) is associated with autosomal recessive juvenile onset Parkinson's disease and was found to be associated with protein aggregation. Members of the human small heat shock proteins (HSPBs) have been implicated in protein degradation and prevention of protein aggregation. In this study, we show that of the 10 HSPB members, individual overexpression of HSPB1, HSPB2, HSPB4, and HSPB7 suppresses PARK2 C289G-associated protein aggregation. Intriguingly, the protective actions of these HSPBs are not impaired upon inactivation of the ATP-dependent HSP70 chaperone machines. Depending on the HSPB member the protective actions involve either autophagic or proteasomal degradation pathways

VISTA expression by microglia decreases during inflammation and is differentially regulated in CNS diseases

V-type immunoglobulin domain-containing suppressor of T-cell activation (VISTA) is a negative checkpoint regulator (NCR) involved in inhibition of T cell-mediated immunity. Expression changes of other NCRs (PD-1, PD-L1/L2, CTLA-4) during inflammation of the central nervous system (CNS) were previously demonstrated, but VISTA expression in the CNS has not yet been explored. Here, we report that in the human and mouse CNS, VISTA is most abundantly expressed by microglia, and to lower levels by endothelial cells. Upon TLR stimulation, VISTA expression was reduced in primary neonatal mouse and adult rhesus macaque microglia in vitro. In mice, microglial VISTA expression was reduced after lipopolysaccharide (LPS) injection, during experimental autoimmune encephalomyelitis (EAE), and in the accelerated aging Ercc1 Δ/- mouse model. After LPS injection, decreased VISTA expression in mouse microglia was accompanied by decreased acetylation of lysine residue 27 in histone 3 in both its promoter and enhancer region. ATAC-sequencing indicated a potential regulation of VISTA expression by Pu.1 and Mafb, two transcription factors crucial for microglia function. Finally, our data suggested that VISTA expression was decreased in microglia in multiple sclerosis lesion tissue, whereas it was increased in Alzheimer's disease patients. This study is the first to demonstrate that in the CNS, VISTA is expressed by microglia, and that VISTA is differentially expressed in CNS pathologies.</p

Targeted Diet Modification Reduces Multiple Sclerosis-like Disease in Adult Marmoset Monkeys from an Outbred Colony

Experimental autoimmune encephalomyelitis (EAE) in common marmosets is a translationally relevant model of the chronic neurologic disease multiple sclerosis. Following the introduction of a new dietary supplement in our purpose-bred marmoset colony, the percentage of marmosets in which clinically evident EAE could be induced by sensitization against recombinant human myelin oligodendrocyte glycoprotein in IFA decreased from 100 to 65%. The reduced EAE susceptibility after the dietary change coincided with reduced Callitrichine herpesvirus 3 expression in the colony, an EBV-related gamma 1-herpesvirus associated with EAE. We then investigated, in a controlled study in marmoset twins, which disease-relevant parameters were affected by the dietary change. The selected twins had been raised on the new diet for at least 12 mo prior to the study. In twin siblings reverted to the original diet 8 wk prior to EAE induction, 100% disease prevalence (eight out of eight) was restored, whereas in siblings remaining on the new diet the EAE prevalence was 75% (six out of eight). Spinal cord demyelination, a classical hallmark of the disease, was significantly lower in new-diet monkeys than in monkeys reverted to the original diet. In new-diet monkeys, the proinflammatory T cell response to recombinant human myelin oligodendrocyte glycoprotein was significantly reduced, and RNA-sequencing revealed reduced apoptosis and enhanced myelination in the brain. Systematic typing of the marmoset gut microbiota using 16S rRNA sequencing demonstrated a unique, Bifidobacteria-dominated composition, which changed after disease induction. In conclusion, targeted dietary intervention exerts positive effects on EAE-related parameters in multiple compartments of the marmoset's gutimmune-CNS axis

Targeted Diet Modification Reduces Multiple Sclerosis-like Disease in Adult Marmoset Monkeys from an Outbred Colony

Experimental autoimmune encephalomyelitis (EAE) in common marmosets is a translationally relevant model of the chronic neurologic disease multiple sclerosis. Following the introduction of a new dietary supplement in our purpose-bred marmoset colony, the percentage of marmosets in which clinically evident EAE could be induced by sensitization against recombinant human myelin oligodendrocyte glycoprotein in IFA decreased from 100 to 65%. The reduced EAE susceptibility after the dietary change coincided with reduced Callitrichine herpesvirus 3 expression in the colony, an EBV-related gamma 1-herpesvirus associated with EAE. We then investigated, in a controlled study in marmoset twins, which disease-relevant parameters were affected by the dietary change. The selected twins had been raised on the new diet for at least 12 mo prior to the study. In twin siblings reverted to the original diet 8 wk prior to EAE induction, 100% disease prevalence (eight out of eight) was restored, whereas in siblings remaining on the new diet the EAE prevalence was 75% (six out of eight). Spinal cord demyelination, a classical hallmark of the disease, was significantly lower in new-diet monkeys than in monkeys reverted to the original diet. In new-diet monkeys, the proinflammatory T cell response to recombinant human myelin oligodendrocyte glycoprotein was significantly reduced, and RNA-sequencing revealed reduced apoptosis and enhanced myelination in the brain. Systematic typing of the marmoset gut microbiota using 16S rRNA sequencing demonstrated a unique, Bifidobacteria-dominated composition, which changed after disease induction. In conclusion, targeted dietary intervention exerts positive effects on EAE-related parameters in multiple compartments of the marmoset's gutimmune-CNS axis.</p