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Endothelin-1 (ET-1) is up-regulated in astrocytes under ischemia. Our previous studies suggest that astrocytic ET-1 has deleterious effects on water homeostasis, cerebral edema and BBB integrity, which contribute to more severe ischemic brain injury. We also found that astrocytic ET-1 plays a deleterious role in cognitive function and neurodegeneration associated with Alzheimer’s disease (AD) and mild ischemic stroke. However, as a vasoconstrictor and mitogenic factor, it is unclear whether the astrocytic ET-1 also plays a role in neurogenesis after cerebral ischemia. Up to now, it is still largely unknown the role of astrocytic ET-1 in regulating neuronal progenitor cell proliferation, migration, and differentiation after stroke. Here, we investigate the effects of astrocytic endothelin-1 overexpression on neurogenesis after stroke.
Non-transgenic (Ntg) and GET-1 mice were subjected to 1h ischemia and longtime reperfusion(7d and 28d) tMCAO model. Neurological function test were performed at 1, 7, 28 days after the onset of MCAO, brain infarct area and volume were calculated using TTC staining. To identify newly formed DNA in ischemic brain, BrdU (50 mg/kg, ip) was dissolved in saline and given intraperitoneally twice daily at 8 hour intervals for five consecutive days, starting 24 hours after initiating MCAO, SVZ progenitor cell proliferation in the ischemic brain after tMCAO were detected by BrdU co- immunostaining with Sox2, Nestin, and GFAP in GET-1 and Ntg mice. SVZ progenitor cell differentiation in the ischemic brain after tMCAO were detected by BrdU co- immunostaining with NeuN and GFAP.
The result showed that GET-1 mice exhibited more severe neurological functional deficit than that of Ntg mice at 1d and 7d after tMCAO, there were Increased SVZ progenitor cell proliferation in the ischemic brain after stroke in GET-1 mice, measured using bromodeoxyuridine(BrdU), Sox2, Nestin, and GFAP immunostaining in the ischemic brain, however, the numbers of BrdU labeled cells coexpressed with the migrating neuroblast marker doublecortin (DCX) didn’t show significant difference in SVZ region. In addition, the numbers of BrdU labeled cells coexpressed with GFAP were significantly increased at 28d after tMCAO, while only a few BrdU labeled cells co-stained with mature neuronal marker neuronal nuclei (NeuN).
These data indicate that astrocytic endothelin-1 overexpression promoted progenitor stem cell proliferation and astrocytic differentiation but inhibit neuronal differentiation, which may affect neurological functional outcome after stroke.