Ferroptosis in oligodendrocyte progenitor cells mediates white matter injury after hemorrhagic stroke
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ABSTRACT: Oligodendrocyte progenitor cells (OPCs) differentiate to myelin-producing mature oligodendrocytes and enwrap growing or demyelinated axons during development and post central nervous diseases. Failure of remyelination due to cell death or undifferentiation of OPC contributes to severe neurologic deficits and motor dysfunction. However, how to prevent the cell death of OPCs is still poorly understood, especially in hemorrhagic diseases. In this current study, we injected autologous blood into the mouse lateral ventricular to study the hemorrhage induced OPC cell death in vivo. The integrity of the myelin sheath of the corpus callosum was disrupted post intraventricular hemorrhage (IVH) assessed by using magnetic resonance imaging, immunostaining, and transmission electron microscopy. Consistent with the severe demethylation, we observed massive cell death of oligodendrocyte lineages in the periventricular area. In addition, we found that ferroptosis is the major cell death form in Hemin-induced OPC death by using RNA-seq analysis, and the mechanism was glutathione peroxidase 4 (GPx4) expression and activity reduction-resulted lipid peroxide accumulation. Furthermore, inhibition of ferroptosis rescued OPC cell death in vitro, and in vivo attenuated IVH-induced white matter injury and promoted recovery of neurological function. These data demonstrate that ferroptosis is an essential form of OPC cell death in hemorrhagic stroke, and rescuing ferroptotic OPCs could serve as a therapeutic target for stroke and related diseases.
Project description:A subset of infants and adults with hemorrhagic stroke and intraventricular hemorrhage (IVH) ultimately develop a life-threatening accumulation of cerebrospinal fluid (CSF), termed post-hemorrhagic hydrocephalus (PHH). An incomplete understanding of this variably progressive condition has hampered the development of new therapies beyond serial neurosurgical interventions. We describe an adeno-associated viral (AAV) gene augmentation approach leveraging the Na-K-Cl cotransporter, NKCC1, to enhance a choroid plexus (ChP) mechanism of CSF surveillance, potassium homeostasis, and water movement to drive decreases in ventricle size in embryonic, neonatal, and adult mouse models of IVH. Intraventricular blood led to increased CSF [K+], triggered cytosolic calcium in ChP epithelial cells, and was followed by NKCC1 activation. ChP-targeted AAV-NKCC1 rapidly reversed blood-induced ventriculomegaly and led to persistently increased CSF clearance capacity, validating the model and treating the most salient clinical features of PHH. NKCC1 is a bi-directional cotransporter, and these data demonstrate that NKCC1 activation triggered a trans-choroidal, NKCC1-dependent CSF ion/water clearance out of the ventricle. Inactive, phosphodeficient AAV-NKCC1-NT51 failed to mitigate ventriculomegaly, indicating that the beneficial effects of NKCC1 augmentation required both elevated CSF [K+] and upstream activation via phosphorylation. Excessive CSF [K+] fluctuations correlated with permanent shunting outcome in humans following hemorrhagic stroke, suggesting potential therapeutic benefits. Collectively, these data highlight a novel role for the ChP in rapid compensation for alterations in CSF homeostasis following IVH and demonstrate the utility of targeted gene therapy to mitigate intracranial fluid accumulation following hemorrhage.
Project description:Tissue progenitors maintain the integrity of organ systems through aging and stress. The brain’s white matter regions experience ischemic lesions and age-dependent degeneration. Brain white matter contains progenitors, oligodendrocyte precursor cells (OPCs), which can repair some insults. The response of OPCs to white matter ischemia and aging is not known. We characterized the response of OPCs to white matter stroke using OPC reporter mice, cell migration tracking, OPC specific RNA sequencing, and mechanistic studies in candidate biochemical pathways in the aged brain. White matter stroke induces initial proliferation of local OPCs but blocks differentiation, shunting a portion into astrocytes. Candidate signaling pathways for this differentiation block including novel interactions of inhibin and matrilin-2 and new roles of NgR1 ligands following white matter stroke. Stroke induces inhibin expression in astrocytes and downregulates OPC matrilin-2 that contributes into OPC differentiation block. Antagonism of NgR1 ligands promotes OPC differentiation by attenuating the OPC astrocytic transformation and enhances functional recovery from stroke in aged animals.
Project description:Following CNS demyelination, adult oligodendrocyte progenitor cells (OPCs) can differentiate into new myelin-forming oligodendrocytes in a regenerative process called remyelination. While remyelination is very efficient in young adults, its efficiency declines progressively with ageing. Here we performed proteomic analysis on OPCs isolated acutely from the brains of neonate, young and aged female rats. Approximately 60% of the proteins are expressed at different levels in OPCs from neonates compared to their adult counterparts. The amount of myelin-associated and cell adhesion proteins are increased with age, while cholesterol-biosynthesis, transcription factors and cell cycle proteins decreased. Our experiments provide the first ageing OPC rodent proteome, revealing the distinct features of neonatal and adult OPCs, and providing new insights into why remyelination efficiency declines with ageing and potential roles for aged OPCs in other neurodegenerative diseases.
Project description:Following CNS demyelination, adult oligodendrocyte progenitor cells (OPCs) can differentiate into new myelin-forming oligodendrocytes in a regenerative process called remyelination. While remyelination is very efficient in young adults, its efficiency declines progressively with ageing. Here we performed proteomic analysis on OPCs isolated acutely from the brains of neonate, young and aged female rats. Approximately 60% of the proteins are expressed at different levels in OPCs from neonates compared to their adult counterparts. The amount of myelin-associated and cell adhesion proteins are increased with age, while cholesterol-biosynthesis, transcription factors and cell cycle proteins decreased. Our experiments provide the first ageing OPC rodent proteome, revealing the distinct features of neonatal and adult OPCs, and providing new insights into why remyelination efficiency declines with ageing and potential roles for aged OPCs in other neurodegenerative diseases.
Project description:We hypothesized that activation of PPARg would enhance myelination, reduce hydrocephalus, and promote neurological recovery in newborns with IVH. These hypotheses were tested in preterm rabbit model of IVH; autopsy brain samples from premature infants with and without IVH were analyzed. We found that IVH augmented PPARg expression in microglia of both preterm human infants and rabbit kits. The treatment with PPARg agonist or PPARg overexpression by adenovirus delivery further elevated PPARg levels in microglia, reduced pro-inflammatory cytokines, increased microglial phagocytosis, and improved oligodendrocyte progenitor cell (OPC) maturation in kits with IVH. Transcriptomic analyses of OPCs identified previously unrecognized PPARg-induced novel genes for purinergic signaling, cAMP generation, and antioxidant production, which would reprogram these progenitors toward promoting myelination. RNA-seq analyses of microglia revealed PPARg-triggered downregulation of several pro-inflammatory genes and transcripts having roles in Parkinson’s disease and amyotrophic lateral sclerosis, contributing to neurological recovery in kits with IVH. Accordingly, PPARg activation enhanced myelination and neurological function in kits with IVH.
Project description:Myelination depends on maintenance of oligodendrocytes that arise from oligodendrocyte precursor cells (OPCs). We show that OPC-specific proliferation, morphology, and BMAL1 are time-of-day dependent. Knock out of Bmal1 in OPCs during development disrupts expression of genes associated with circadian rhythms, proliferation, density, morphology, and migration, leading to changes in OPC dynamics in a spatio-temporal manner. Furthermore, these deficits translate into thinner myelin, dysregulated cognitive and motor function, and increased sleep fragmentation. OPC-specificBmal1loss in adulthood does not alter OPC density at baseline but impairs remyelination of a demyelinated lesion driven by changes in OPC morphology and migration. Lastly, we show sleep fragmentation is associated with increased prevalence of the demyelinating disorder multiple sclerosis (MS), suggesting a link between MS and sleep that requires further investigation. These findings have broad mechanistic and therapeutic implications for brain disorders that include both myelin and sleep phenotypes.
Project description:Overexpression of VEGF (vascular endothelial growth factor) in the germinal matrix of the brain causes GMH-IVH-like anomalies (Germinal matrix hemorrhage [GMH]; intraventricular hemorrhage [IVH]). This dataset provides the list of differentially expressed genes in the brain cortices of embryos with transgene directed overexpression of VEGF. Eight samples were analyzed, including four control and four with induced over expression of VEGF. A simple unpaired T-test was used for analysis, with GeneSpring software,
Project description:Neuronal activity can regulate the formation of new myelin by controlling division and differentiation of oligodendrocyte precursor cells (OPCs). If activity directly instructs OPCs to differentiate or whether this process underlies a more complex regulation in unclear, because it is not known if OPCs with different functions exist. By following lineage formation of individual OPC clones, single cell RNA sequencing, in vivo calcium imaging and manipulation of neural activity, we show that OPCs in the zebrafish spinal cord can be divided into two functional entities. One subgroup forms elaborate process networks and exhibits a high degree of calcium signalling activity, but infrequently differentiates, despite contact with permissive axons. Instead, these OPCs can divide in an activity and calcium dependent manner to produce another subgroup of OPCs, which readily differentiates and which shows less elaborate, more dynamic processes, and less calcium signaling activity. Our data reveal functional diversity within the OPC population in responding to neural activity and show that activity regulates proliferation of a subset of OPCs that is distinct from the cells that will differentiate, with implications for myelin development, plasticity, and repair.
Project description:Remyelination after white matter injury (WMI) often fails in diseases such as multiple sclerosis due to improper recruitment and repopulation of oligodendrocyte precursor cells (OPCs) in lesions. How OPCs elicit specific intracellular programs in response to a chemically and mechanically diverse environment to properly regenerate myelin remains unclear. OPCs construct primary cilia, specialized signaling compartments that transduce Hh and GPCR signals. We investigated the role of primary cilia in the OPC response to WMI. Removing cilia from OPCs genetically via deletion of Ift88 results in OPCs failing to repopulate WMI lesions due to reduced proliferation. Interestingly, loss of cilia does not affect Hh signaling in OPCs or their responsiveness to Hh signals, but instead leads to dysfunctional cAMP-dependent CREB-mediated transcription. As inhibition of CREB activity in OPCs reduces proliferation, we propose that a GPCR/cAMP/CREB signaling axis initiated at OPC cilia orchestrates OPC proliferation during development and in response to WMI.
Project description:Overexpression of VEGF (vascular endothelial growth factor) in the germinal matrix of the brain causes GMH-IVH-like anomalies (Germinal matrix hemorrhage [GMH]; intraventricular hemorrhage [IVH]). This dataset provides the list of differentially expressed genes in the brain cortices of embryos with transgene directed overexpression of VEGF.