Molecular activation of gliovascular signaling precedes blood‐brain barrier disruption and neuronal loss in a mouse model of tauopathy

Abstract

AbstractBackgroundIncreasing evidence points to disruption of the blood‐brain barrier (BBB) as an inciting event in the pathogenesis of Alzheimer’s disease. The contribution of tau‐mediated pathways driving blood‐brain dysfunction are comparatively understudied.MethodUsing the P301S mouse model of tauopathy, we employed dynamic contrast enhanced MRI (DCE‐MRI) and quantitative spatial analysis using gadolinium‐based mass spectrometry imaging to demonstrate widespread BBB dysfunction in late stage tauopathy. To identify molecular pathways regulating intercellular signaling between neurons and gliovascular support cells that are dysregulated in advance of BBB disruption, we developed a cell‐specific viral approach for transcriptional profiling of novel pathways within the multicellular environment of the neurovascular unit (NVU) in tauopathy. Viral constructs using cell‐type specific promoters (hSynapsin, GFAP, or PDGFRb) to drive expression of antigen‐tagged ribosomes (TRAP) were used to study variance in spatial and temporal gene expression patterns in NVU cell types in P301S transgenic mice prior to widespread BBB disruption.ResultRegional disruption of BBB integrity involving the hippocampus, lateral temporal, and frontal cortices is prominent in 11 month‐old P301S mice. Cell‐specific profiling of early symptomatic 6 month‐old P301S mice identified a defined gene expression profile antecedent to BBB disruption in NVU cells comprised of 29 shared and 3299 unique genes across all cell types. In this early symptomatic stage of tauopathy, pericytes (1021 genes) and astrocytes (1717 genes) were remarkably more transcriptionally active than neurons (561 genes). Gene ontology analysis indicates that multiple molecular programs driving neuronal differentiation, neurite outgrowth, and synaptogenesis are expressed in gliovascular cells in the prodromal stage.ConclusionThe specific and temporally regulated coordination of pathways in pericytes and astrocytes in advance of BBB dysfunction implicates the neurovascular unit as a potential driver in the development of tauopathy. This suggests a paradigm exists for gliovascular rescue of neurodegeneration and implicates numerous novel perivascular molecular pathways in the pathogenesis of tauopathy and Alzheimer’s disease.