Targeted deletion of astrocytic Nhe1 stimulates Wnt/β-catenin-mediated BBB repair and angiogenesis after ischemic stroke

ABSTRACT: Roles of reactive perivascular astrocytes in dysregulation of the blood-brain barrier (BBB) function and cerebral perfusion are not well defined. Here, we investigated transformation of reactive astrocyte function for vascular repair after ischemic stroke by targeted deletion of astrocytic Na+/H+ exchanger isoform 1 in Gfap-CreERT2+/-;Nhe1f/f (Nhe1 Astro-KO) mice. Control Gfap-CreERT2+/-;Nhe1f/f (wild-type) mice displayed BBB damage (elevated endothelial transcytosis and intracellular vesicles) and persistent cerebral hypoperfusion in an ischemic stroke model (transient middle cerebral artery occlusion). In contrast, Nhe1 Astro-KO mice exhibited significantly less endothelial transcytosis and vesicle formation, and increased angiogenesis and cerebral blood perfusion (CBF) post-stroke. Bulk RNA-sequencing transcriptome analysis of isolated GFAP+ reactive astrocytes from wild-type and Nhe1 Astro-KO ischemic brains revealed that ~177 genes were differentially upregulated, with the Wnt7a mRNA among the top upregulated genes, along with additional Wnt pathway genes (Wnt7b, Fzd9, Fzd10, and Ndp). Abundant Wnt7a/b and β-catenin protein expression was detected in cerebral vessels of Nhe1 Astro-KO ischemic brains but not in the wild-type brains. Selective activation of Wnt/β-catenin pathway in cerebral vessels of Nhe1 Astro-KO ischemic brains was further validated using the Wnt reporter line TCF/LEF::H2B-eGFP; Gfap-CreERT2+/-;Nhe1f/f mice. Lastly, the role of Wnt/β-catenin pathway in resistance of Nhe1 Astro-KO mice to stroke-mediated BBB damage was tested by administration of Wnt/β-catenin inhibitor XAV-939. Taken together, we report that transforming reactive astrocyte function by upregulating astrocytic Wnt/β-catenin signaling activity is a novel mechanism to reduce the BBB endothelial damage, stimulate vascular repair, and restore cerebral blood flow after ischemic stroke.

ORGANISM(S): Mus musculus

PROVIDER: GSE145839 | GEO | 2020/12/08

REPOSITORIES: GEO