Regulation of stress granule formation in human oligodendrocytes

ObjectiveMultiple sclerosis is an inflammatory demyelinating disorder associated with blood-brain-barrier breakdown, where myelin repair is reduced and ultimately fails. Our aim was to investigate the effect of a systemically circulating molecule fibrinogen, which is abnormally present in the central nervous system as a result of blood-brain barrier breakdown on human oligodendrocyte lineage cells.MethodsIn situ immunofluorescence was performed using anti-fibrinogen and anti-SOX10 antibodies. Mature oligodendrocytes and late progenitors were derived from brain tissue from pediatric and adult donors. Early progenitors were generated from human induced pluripotent stem cells. Following fibrinogen addition to each of these cultures, cell viability and functional capacity was evaluated. Downstream signalling following fibrinogen exposure was confirmed by immunofluorescence microscopy and bulk RNA sequencing.ResultsIn situ studies showed fibrinogen on SOX10-positive oligodendrocytes in multiple sclerosis, both in plaques and normal-appearing white matter, and white matter in amyotrophic lateral sclerosis. In response to in vitro exposure to fibrinogen, mature oligodendrocytes showed increased ensheathment capacity and upregulation of lipid synthesis, whereas pediatric-age late oligodendrocyte precursors showed a decrease. Early precursors were unable to differentiate but expressed astrocytic markers and increased proliferation. Fibrinogen-exposed cells show bone morphogenetic protein signalling, more prominently in mature oligodendrocytes.InterpretationWe demonstrate that fibrinogen is deposited on oligodendrocytes in multiple sclerosis and has distinct functional consequences dependent on cell lineage stage. Our findings derived using human OL lineage cells suggest fibrinogen may be beneficial for myelin maintenance by mature oligodendrocytes, while preventing earlier lineage cells from differentiating and repairing multiple sclerosis lesions.

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Pro-Inflammatory Molecules Implicated in Multiple Sclerosis Divert the Development of Human Oligodendrocyte Lineage Cells

Blaszczyk,

Mohammadnia,

Piscopo

et al. 2024

Preprint

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Background and ObjectivesOligodendrocytes (OL) and their myelin-forming processes are targeted and lost during the disease course of Multiple Sclerosis (MS), targeted by infiltrating leukocytes and their effector cytokines. Myelin repair is considered to be dependent on recruitment and differentiation of oligodendrocyte precursor cells (OPCs). The basis of failure of re-myelination during the disease course of MS remains to be defined. The aim of this study is to determine the impact of pro-inflammatory molecules tumor necrosis factor ⍰ (TNF⍰) and interferon gamma (IFNγ) on the differentiation of human OPCs.MethodsWe generated human OPCs from induced pluripotent stem cells with a reporter gene under the OL-specific transcription factor SOX10. We treated the cellsin vitrowith TNF⍰ or IFNγand evaluated effects in terms of cell viability, expression of OL-lineage markers, and co- expression of astrocyte markers. To relate our findings to the molecular properties of OPCs as found in the MS brain we re-analyzed publicly available single nuclear RNAseq datasets.ResultsOur analysis indicated that both TNF⍰ and IFNγdecreased the proportion of cells differentiating into the OL-lineage; consistent with previous reports. We now observe the TNF⍰ effect is linked to aberrant OPC differentiation. A subset of O4+, reporter-positive cells co- expressed the astrocytic marker Aquaporin-4 (AQP4). On the transcriptomic level, the cells acquire an astrocyte-like signature alongside a conserved reactive phenotype. Analysis of single- nuclear RNAseq datasets from human MS brain revealed a subset of OPCs expressing an astrocytic signature.DiscussionIn the context of MS, these results imply that OPCs are present but inhibited from differentiating along the OL-lineage, with a subset acquiring a reactive and stem-cell like phenotype, reducing their capacity to contribute towards repair. These findings help define a potential basis for the impaired myelin repair in MS and provide a prospective route for regenerative treatment.

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Regulation of stress granule formation in human oligodendrocytes

Cited by 4 publications

References 75 publications

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The mitochondria chronicles of melatonin and ATP: Guardians of phase separation

The functional and pathogenic consequences of fibrinogen on human oligodendroglia

Pro-Inflammatory Molecules Implicated in Multiple Sclerosis Divert the Development of Human Oligodendrocyte Lineage Cells

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