Characterisation of early ultrastructural changes in the cerebral white matter of CADASIL small vessel disease using high-pressure freezing/freeze-substitution

Oligodendrocyte-derived laminin-γ1 regulates the blood-brain barrier and CNS myelination in mice

Although oligodendrocytes (OLs) synthesize laminin-γ1, the most widely used γ subunit, its functional significance in the CNS remains unknown. To answer this important question, we generated a conditional knockout mouse line with laminin-γ1 deficiency in OL lineage cells (γ1-OKO). γ1-OKO mice exhibit weakness/paralysis and die by post-natal day 33. Additionally, they develop blood-brain barrier (BBB) disruption in the cortex and striatum. Subsequent studies reveal decreased major facilitator superfamily domain containing 2a expression and increased endothelial caveolae vesicles, but unaltered tight junction protein expression and tight junction ultrastructure, indicating a transcellular, rather than a paracellular, mechanism of BBB breakdown. Furthermore, significantly reduced OL lineage cells, OL precursor cells (OPCs), proliferating OPCs, and mature OLs are observed in γ1-OKO brains in a region-specific manner. Consistent with this finding, various defects in myelination are detected in γ1-OKO brains at biochemical and ultrastructural levels. Overall, these results highlight important roles of OL-derived laminin-γ1 in BBB maintenance and OL biology (proliferation, differentiation, and myelination).

Treatment with Cerebrolysin Prolongs Lifespan in a Mouse Model of Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare familial neurological disorder caused by mutations in the NOTCH3 gene and characterized by migraine attacks, depressive episodes, lacunar strokes, dementia, and premature death. Since there is no therapy for CADASIL the authors investigate whether the multi-modal neuropeptide drug Cerebrolysin may improve outcome in a murine CADASIL model. Twelve-month-old NOTCH3R169C mutant mice (n=176) are treated for nine weeks with Cerebrolysin or Vehicle and histopathological and functional outcomes are evaluated within the subsequent ten months. Cerebrolysin treatment improves spatial memory and overall health, reduces epigenetic aging, and prolongs lifespan, however, CADASIL-specific white matter vacuolization is not affected. On the molecular level Cerebrolysin treatment increases expression of Calcitonin Gene-Related Peptide (CGRP) and Silent Information Regulator Two (Sir2)-like protein 6 (SIRT6), decreases expression of Insulin-like Growth Factor 1 (IGF-1), and normalizes the expression of neurovascular laminin. In summary, Cerebrolysin fosters longevity and healthy aging without specifically affecting CADASIL pathology. Hence, Cerebrolysin may serve a therapeutic option for CADASIL and other disorders characterized by accelerated aging.

Chronic changes in oligodendrocyte sub-populations after middle cerebral artery occlusion in neonatal mice

Neonatal stroke is common and causes life-long motor and cognitive sequelae. Because neonates with stroke are not diagnosed until days-months after the injury, chronic targets for repair are needed. We evaluated oligodendrocyte maturity and myelination and assessed oligodendrocyte gene expression changes using single cell RNA sequencing (scRNA seq) at chronic timepoints in a mouse model of neonatal arterial ischemic stroke. Mice underwent 60 min of transient right middle cerebral artery occlusion (MCAO) on postnatal day 10 (p10) and received 5-ethynyl-2'-deoxyuridine (EdU) on post-MCAO days 3-7 to label dividing cells. Animals were sacrificed 14 and 28-30 days post-MCAO for immunohistochemistry and electron microscopy. Oligodendrocytes were isolated from striatum 14 days post-MCAO for scRNA seq and differential gene expression analysis. The density of Olig2+ EdU+ cells was significantly increased in ipsilateral striatum 14 days post-MCAO and the majority of oligodendrocytes were immature. Density of Olig2+ EdU+ cells declined significantly between 14 and 28 days post-MCAO without a concurrent increase in mature Olig2+ EdU+ cells. By 28 days post-MCAO there were significantly fewer myelinated axons in ipsilateral striatum. scRNA seq identified a cluster of "disease associated oligodendrocytes (DOLs)" specific to the ischemic striatum, with increased expression of MHC class I genes. Gene ontology analysis suggested decreased enrichment of pathways involved in myelin production in the reactive cluster. Oligodendrocytes proliferate 3-7 days post-MCAO and persist at 14 days, but fail to mature by 28 days. MCAO induces a subset of oligodendrocytes with reactive phenotype, which may be a therapeutic target to promote white matter repair.

Roles of NG2 Glia in Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) is one of the most prevalent pathologic processes affecting 5% of people over 50 years of age and contributing to 45% of dementia cases. Increasing evidence has demonstrated the pathological roles of chronic hypoperfusion, impaired cerebral vascular reactivity, and leakage of the blood-brain barrier in CSVD. However, the pathogenesis of CSVD remains elusive thus far, and no radical treatment has been developed. NG2 glia, also known as oligodendrocyte precursor cells, are the fourth type of glial cell in addition to astrocytes, microglia, and oligodendrocytes in the mammalian central nervous system. Many novel functions for NG2 glia in physiological and pathological states have recently been revealed. In this review, we discuss the role of NG2 glia in CSVD and the underlying mechanisms.

Research Progress and Direction of Novel Organelle-Migrasomes

Migrasomes are organelles that are similar in structure to pomegranates, up to 3 μm in diameter, and contain small vesicles with a diameter of 50-100 nm. These membranous organelles grow at the intersections or tips of retracting fibers at the back of migrating cells. The process by which cells release migrasomes and their contents outside the cell is called migracytosis. The signal molecules are packaged in the migrasomes and released to the designated location by migrasomes to activate the surrounding cells. Finally, the migrasomes complete the entire process of information transmission. In this sense, migrasomes integrate time, space, and specific chemical information, which are essential for regulating physiological processes such as embryonic development and tumor invasion and migration. In this review, the current research progress of migrasomes, including the discovery of migrasomes and migracytosis, the structure of migrasomes, and the distribution and functions of migrasomes is discussed. The migratory marker protein TSPAN4 is highly expressed in various cancers and is associated with cancer invasion and migration. Therefore, there is still much research space for the pathogenesis of migratory bodies and cancer. This review also makes bold predictions and prospects for the research directions of the combination of migrasomes and clinical applications.

Genetics of common cerebral small vessel disease

Cerebral small vessel disease (cSVD) is a leading cause of ischaemic and haemorrhagic stroke and a major contributor to dementia. Covert cSVD, which is detectable with brain MRI but does not manifest as clinical stroke, is highly prevalent in the general population, particularly with increasing age. Advances in technologies and collaborative work have led to substantial progress in the identification of common genetic variants that are associated with cSVD-related stroke (ischaemic and haemorrhagic) and MRI-defined covert cSVD. In this Review, we provide an overview of collaborative studies - mostly genome-wide association studies (GWAS) - that have identified >50 independent genetic loci associated with the risk of cSVD. We describe how these associations have provided novel insights into the biological mechanisms involved in cSVD, revealed patterns of shared genetic variation across cSVD traits, and shed new light on the continuum between rare, monogenic and common, multifactorial cSVD. We consider how GWAS summary statistics have been leveraged for Mendelian randomization studies to explore causal pathways in cSVD and provide genetic evidence for drug effects, and how the combination of findings from GWAS with gene expression resources and drug target databases has enabled identification of putative causal genes and provided proof-of-concept for drug repositioning potential. We also discuss opportunities for polygenic risk prediction, multi-ancestry approaches and integration with other omics data.

Pathologic sequelae of vascular cognitive impairment and dementia sheds light on potential targets for intervention

Vascular contributions to cognitive impairment and dementia (VCID) is one of the leading causes of dementia along with Alzheimer's disease (AD) and, importantly, VCID often manifests as a comorbidity of AD(Vemuri and Knopman 2016; Schneider and Bennett 2010)(Vemuri and Knopman 2016; Schneider and Bennett 2010). Despite its common clinical manifestation, the mechanisms underlying VCID disease progression remains elusive. In this review, existing knowledge is used to propose a novel hypothesis linking well-established risk factors of VCID with the distinct neurodegenerative cascades of neuroinflammation and chronic hypoperfusion. It is hypothesized that these two synergistic signaling cascades coalesce to initiate aberrant angiogenesis and induce blood brain barrier breakdown trough a mechanism mediated by vascular growth factors and matrix metalloproteinases respectively. Finally, this review concludes by highlighting several potential therapeutic interventions along this neurodegenerative sequalae providing diverse opportunities for future translational study.