RESUMEN
Perinatal white matter injury (WMI) is the leading cause of long-term neurological morbidity in infants born preterm. Neuroinflammation during a critical window of early brain development plays a key role in WMI disease pathogenesis. The mechanisms linking inflammation with the long-term myelination failure that characterizes WMI, however, remain unknown. Here, we investigate the role of astrocyte reactivity in WMI. In an experimental mouse model of WMI, we demonstrate that WMI disease outcomes are improved in mutant mice lacking secretion of inflammatory molecules TNF-α, IL-1α, and C1q known, in addition to other roles, to induce the formation of a neuroinflammatory reactive astrocyte substate. We show that astrocytes express molecular signatures of the neuroinflammatory reactive astrocyte substate in both our WMI mouse model and human tissue affected by WMI, and that this gene expression pattern is dampened in injured mutant mice. Our data provide evidence that a neuroinflammatory reactive astrocyte substate correlates with adverse WMI disease outcomes, thus highlighting the need for further investigation of these cells as potential causal players in WMI pathology.
Asunto(s)
Animales Recién Nacidos , Astrocitos , Sustancia Blanca , Animales , Astrocitos/metabolismo , Astrocitos/patología , Sustancia Blanca/patología , Sustancia Blanca/metabolismo , Ratones , Humanos , Enfermedades Neuroinflamatorias/patología , Enfermedades Neuroinflamatorias/metabolismo , Ratones Endogámicos C57BL , Femenino , Modelos Animales de Enfermedad , Ratones Noqueados , Recién NacidoRESUMEN
Multiple sclerosis (MS) is a progressive inflammatory demyelinating disease of the CNS. Increasing evidence suggests that vulnerable neurons in MS exhibit fatal metabolic exhaustion over time, a phenomenon hypothesized to be caused by chronic hyperexcitability. Axonal Kv7 (outward-rectifying) and oligodendroglial Kir4.1 (inward-rectifying) potassium channels have important roles in regulating neuronal excitability at and around the nodes of Ranvier. Here, we studied the spatial and functional relationship between neuronal Kv7 and oligodendroglial Kir4.1 channels and assessed the transcriptional and functional signatures of cortical and retinal projection neurons under physiological and inflammatory demyelinating conditions. We found that both channels became dysregulated in MS and experimental autoimmune encephalomyelitis (EAE), with Kir4.1 channels being chronically downregulated and Kv7 channel subunits being transiently upregulated during inflammatory demyelination. Further, we observed that pharmacological Kv7 channel opening with retigabine reduced neuronal hyperexcitability in human and EAE neurons, improved clinical EAE signs, and rescued neuronal pathology in oligodendrocyte-Kir4.1-deficient (OL-Kir4.1-deficient) mice. In summary, our findings indicate that neuron-OL compensatory interactions promoted resilience through Kv7 and Kir4.1 channels and identify pharmacological activation of nodal Kv7 channels as a neuroprotective strategy against inflammatory demyelination.
Asunto(s)
Encefalomielitis Autoinmune Experimental , Esclerosis Múltiple , Ratones , Animales , Humanos , Nódulos de Ranvier/metabolismo , Potasio/metabolismo , Neuronas/metabolismo , Oligodendroglía/metabolismo , Encefalomielitis Autoinmune Experimental/genética , Encefalomielitis Autoinmune Experimental/metabolismo , Esclerosis Múltiple/genética , Esclerosis Múltiple/metabolismoRESUMEN
BACKGROUND: Neonatal stroke affects 1 in 2800 live births and is a major cause of neurological injury. The Sonic hedgehog (Shh) signaling pathway is critical for central nervous system (CNS) development and has neuroprotective and reparative effects in different CNS injury models. Previous studies have demonstrated beneficial effects of small molecule Shh-Smoothened agonist (SAG) against neonatal cerebellar injury and it improves Down syndrome-related brain structural deficits in mice. Here we investigated SAG neuroprotection in rat models of neonatal ischemia-reperfusion (stroke) and adult focal white matter injury. METHODS: We used transient middle cerebral artery occlusion at P10 and ethidium bromide (EB) injection in adult rats to induce damage. Following surgery and SAG or vehicle treatment, we analyzed tissue loss, cell proliferation and fate, and behavioral outcome. RESULTS: We report that a single dose of SAG administered following neonatal stroke preserved brain volume, reduced gliosis, enhanced oligodendrocyte progenitor cell (OPC) and EC proliferation, and resulted in long-term cognitive improvement. Single-dose SAG also promoted proliferation of OPCs following focal demyelination in the adult rat. CONCLUSIONS: These findings indicate benefit of one-time SAG treatment post insult in reducing brain injury and improving behavioral outcome after experimental neonatal stroke. IMPACT: A one-time dose of small molecule Sonic hedgehog agonist protected against neonatal stroke and improved long-term behavioral outcomes in a rat model. This study extends the use of Sonic hedgehog in treating developing brain injury, previously shown in animal models of Down syndrome and cerebellar injury. Sonic hedgehog agonist is one of the most promising therapies in treating neonatal stroke thanks to its safety profile and low dosage.
Asunto(s)
Proteínas Hedgehog/antagonistas & inhibidores , Fármacos Neuroprotectores/uso terapéutico , Bibliotecas de Moléculas Pequeñas/uso terapéutico , Accidente Cerebrovascular/prevención & control , Animales , Conducta Animal , Proliferación Celular , Modelos Animales de Enfermedad , Humanos , Recién Nacido , Infarto de la Arteria Cerebral Media/complicaciones , Ratones , Ratas , Ratas Sprague-Dawley , Accidente Cerebrovascular/etiologíaRESUMEN
Recent studies have indicated oligodendroglial-vascular crosstalk during brain development, but the underlying mechanisms are incompletely understood. We report that oligodendrocyte precursor cells (OPCs) contact sprouting endothelial tip cells in mouse, ferret, and human neonatal white matter. Using transgenic mice, we show that increased or decreased OPC density results in cognate changes in white matter vascular investment. Hypoxia induced increases in OPC numbers, vessel density and endothelial cell expression of the Wnt pathway targets Apcdd1 and Axin2 in white matter, suggesting paracrine OPC-endothelial signaling. Conditional knockout of OPC Wntless resulted in diminished white matter vascular growth in normoxia, whereas loss of Wnt7a/b function blunted the angiogenic response to hypoxia, resulting in severe white matter damage. These findings indicate that OPC-endothelial cell interactions regulate neonatal white matter vascular development in a Wnt-dependent manner and further suggest this mechanism is important in attenuating hypoxic injury.
Asunto(s)
Células Endoteliales/metabolismo , Hipoxia/metabolismo , Oligodendroglía/metabolismo , Sustancia Blanca/irrigación sanguínea , Vía de Señalización Wnt/fisiología , Animales , Proteína Axina/metabolismo , Diferenciación Celular/fisiología , Endotelio Vascular/metabolismo , Hurones , Humanos , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas de la Membrana/metabolismo , Ratones , Ratones Transgénicos , Sustancia Blanca/metabolismoRESUMEN
Pelizaeus-Merzbacher disease (PMD) is an X-linked leukodystrophy caused by mutations in Proteolipid Protein 1 (PLP1), encoding a major myelin protein, resulting in profound developmental delay and early lethality. Previous work showed involvement of unfolded protein response (UPR) and endoplasmic reticulum (ER) stress pathways, but poor PLP1 genotype-phenotype associations suggest additional pathogenetic mechanisms. Using induced pluripotent stem cell (iPSC) and gene-correction, we show that patient-derived oligodendrocytes can develop to the pre-myelinating stage, but subsequently undergo cell death. Mutant oligodendrocytes demonstrated key hallmarks of ferroptosis including lipid peroxidation, abnormal iron metabolism, and hypersensitivity to free iron. Iron chelation rescued mutant oligodendrocyte apoptosis, survival, and differentiationin vitro, and post-transplantation in vivo. Finally, systemic treatment of Plp1 mutant Jimpy mice with deferiprone, a small molecule iron chelator, reduced oligodendrocyte apoptosis and enabled myelin formation. Thus, oligodendrocyte iron-induced cell death and myelination is rescued by iron chelation in PMD pre-clinical models.
Asunto(s)
Deferiprona/uso terapéutico , Células Madre Pluripotentes Inducidas/fisiología , Quelantes del Hierro/uso terapéutico , Hierro/metabolismo , Proteína Proteolipídica de la Mielina/metabolismo , Oligodendroglía/fisiología , Enfermedad de Pelizaeus-Merzbacher/terapia , Animales , Diferenciación Celular , Células Cultivadas , Ferroptosis , Humanos , Células Madre Pluripotentes Inducidas/efectos de los fármacos , Células Madre Pluripotentes Inducidas/trasplante , Peroxidación de Lípido , Ratones , Ratones Mutantes , Mutación/genética , Proteína Proteolipídica de la Mielina/genética , Oligodendroglía/efectos de los fármacos , Oligodendroglía/trasplante , Enfermedad de Pelizaeus-Merzbacher/genética , Enfermedad de Pelizaeus-Merzbacher/patología , Trasplante de Células Madre , Reparación del Gen BlancoRESUMEN
The human early postnatal brain contains late migratory streams of immature interneurons that are directed to cortex and other focal brain regions. However, such migration is not observed in rodent brain, and whether other small animal models capture this aspect of human brain development is unclear. Here, we investigated whether the gyrencephalic ferret cortex possesses human-equivalent postnatal streams of doublecortin positive (DCX+) young neurons. We mapped DCX+ cells in the brains of ferrets at P20 (analogous to human term gestation), P40, P65, and P90. In addition to the rostral migratory stream, we identified three populations of young neurons with migratory morphology at P20 oriented toward: (a) prefrontal cortex, (b) dorsal posterior sigmoid gyrus, and (c) occipital lobe. These three neuronal collections were all present at P20 and became extinguished by P90 (equivalent to human postnatal age 2 years). DCX+ cells in such collections all expressed GAD67, identifying them as interneurons, and they variously expressed the subtype markers SP8 and secretagogin (SCGN). SCGN+ interneurons appeared in thick sections to be oriented from white matter toward multiple cortical regions, and persistent SCGN-expressing cells were observed in cortex. These findings indicate that ferret is a suitable animal model to study the human-relevant process of late postnatal cortical interneuron integration into multiple regions of cortex.
Asunto(s)
Encéfalo/citología , Encéfalo/crecimiento & desarrollo , Hurones/anatomía & histología , Interneuronas/citología , Animales , Encéfalo/metabolismo , Caspasa 3/metabolismo , Movimiento Celular , Proteínas de Dominio Doblecortina , Proteína Doblecortina , Hurones/metabolismo , Humanos , Interneuronas/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Neuropéptidos/metabolismo , Secretagoginas/metabolismo , Sustancia Blanca/citología , Sustancia Blanca/crecimiento & desarrollo , Sustancia Blanca/metabolismoRESUMEN
Adult neural stem cells (NSCs) reside in a specialized microenvironment, the subventricular zone (SVZ), which provides them with unique signaling cues to control their basic properties and prevent their exhaustion. While the signaling mechanisms that regulate NSC lineage progression are well characterized, the molecular mechanisms that trigger the activation of quiescent NSCs during homeostasis and tissue repair are still unclear. Here, we uncovered that the NSC quiescent state is maintained by Rho-GTPase Cdc42, a downstream target of non-canonical Wnt signaling. Mechanistically, activation of Cdc42 induces expression of molecules involved in stem cell identity and anchorage to the niche. Strikingly, during a demyelination injury, downregulation of non-canonical Wnt-dependent Cdc42 activity is necessary to promote activation and lineage progression of quiescent NSCs, thereby initiating the process of tissue repair.
Asunto(s)
Enfermedades Desmielinizantes , Homeostasis , Células-Madre Neurales/citología , Transducción de Señal , Proteínas Wnt/metabolismo , Animales , Proteína de Unión al GTP cdc42/metabolismoRESUMEN
NG2-expressing glia (NG2 glia) are a uniformly distributed and mitotically active pool of cells in the central nervous system (CNS). In addition to serving as progenitors of myelinating oligodendrocytes, NG2 glia might also fulfill physiological roles in CNS homeostasis, although the mechanistic nature of such roles remains unclear. Here, we report that ablation of NG2 glia in the prefrontal cortex (PFC) of the adult brain causes deficits in excitatory glutamatergic neurotransmission and astrocytic extracellular glutamate uptake and induces depressive-like behaviors in mice. We show in parallel that chronic social stress causes NG2 glia density to decrease in areas critical to Major Depressive Disorder (MDD) pathophysiology at the time of symptom emergence in stress-susceptible mice. Finally, we demonstrate that loss of NG2 glial secretion of fibroblast growth factor 2 (FGF2) suffices to induce the same behavioral deficits. Our findings outline a pathway and role for NG2 glia in CNS homeostasis and mood disorders.
Asunto(s)
Antígenos/metabolismo , Depresión/patología , Factor 2 de Crecimiento de Fibroblastos/metabolismo , Neuroglía/metabolismo , Corteza Prefrontal/patología , Proteoglicanos/metabolismo , Estrés Psicológico/fisiopatología , Sistema de Transporte de Aminoácidos X-AG/genética , Sistema de Transporte de Aminoácidos X-AG/metabolismo , Animales , Antígenos/genética , Depresión/etiología , Toxina Diftérica/administración & dosificación , Modelos Animales de Enfermedad , Regulación hacia Abajo/genética , Conducta Exploratoria/fisiología , Factor 2 de Crecimiento de Fibroblastos/genética , Factor de Crecimiento Similar a EGF de Unión a Heparina/genética , Humanos , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Fosfopiruvato Hidratasa/metabolismo , Transporte de Proteínas/efectos de los fármacos , Transporte de Proteínas/genética , Proteoglicanos/genética , Receptores de Glutamato/genética , Receptores de Glutamato/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/genéticaRESUMEN
Discrete cellular microenvironments regulate stem cell pools and their development, as well as function in maintaining tissue homeostasis. Although the signaling elements modulating neural progenitor cells (NPCs) of the adult subventricular zone (SVZ) niche are fairly well understood, the pathways activated following injury and the resulting outcomes, are less clear. In the present study, we used mouse models of demyelination and proteomics analysis to identify molecular cues present in the adult SVZ niche during injury, and analyzed their role on NPCs in the context of promoting myelin repair. Proteomic analysis of SVZ tissue from mice with experimental demyelination identified several proteins that are known to play roles in NPC proliferation, adhesion, and migration. Among the proteins found to be upregulated were members of the N-cadherin signaling pathway. During the onset of demyelination in the subcortical white matter (SCWM), activation of epidermal growth factor receptor (EGFR) signaling in SVZ NPCs stimulates the interaction between N-cadherin and ADAM10. Upon cleavage and activation of N-cadherin signaling by ADAM10, NPCs undergo cytoskeletal rearrangement and polarization, leading to enhanced migration out of the SVZ into demyelinated lesions of the SCWM. Genetically disrupting either EGFR signaling or ADAM10 inhibits this pathway, preventing N-cadherin regulated NPC polarization and migration. Additionally, in vivo experiments using N-cadherin gain- and loss-of-function approaches demonstrated that N-cadherin enhances the recruitment of SVZ NPCs into demyelinated lesions. Our data revealed that EGFR-dependent N-cadherin signaling physically initiated by ADAM10 cleavage is the response of the SVZ niche to promote repair of the injured brain.