Endothelial Cells Are Heterogeneous in Different Brain Regions and Are Dramatically Altered in Alzheimer's Disease

Abstract

Vascular endothelial cells play an important role in maintaining brain health, but their contribution to Alzheimer’s disease (AD) is obscured by limited understanding of the cellular heterogeneity in normal aged brain and in disease. To address this, we performed single nucleus RNAseq on tissue from 32 human AD and non-AD donors (19 female, 13 male) each with five cortical regions: entorhinal cortex, inferior temporal gyrus, prefrontal cortex, visual association cortex and primary visual cortex. Analysis of 51,586 endothelial cells revealed unique gene expression patterns across the five regions in non-AD donors. Alzheimer’s brain endothelial cells were characterized by upregulated protein folding genes and distinct transcriptomic differences in response to amyloid beta plaques and cerebral amyloid angiopathy (CAA). This dataset demonstrates previously unrecognized regional heterogeneity in the endothelial cell transcriptome in both aged non-AD and AD brain.SIGNIFICANCE STATEMENT:In this work, we show that vascular endothelial cells collected from five different brain regions display surprising variability in gene expression. In the presence of Alzheimer's disease pathology, endothelial cell gene expression is dramatically altered with clear differences in regional and temporal changes. These findings help explain why certain brain regions appear to differ in susceptibility to disease-related vascular remodeling events that may impact blood flow.

Patient-Derived Blood-Brain Barrier Model for Screening Copper Bis(thiosemicarbazone) Complexes as Potential Therapeutics in Alzheimer’s Disease

“…This provides important evidence for the evolutionary-unique, human-specific role of BEC and cerebrovasculature in brain neuroimmunity in AD and justifies efforts of antineuroinflammatory drug candidate screening in BEC. Simultaneously, disease-associated neuroinflammation has been shown to contribute to BBB dysfunction in AD, ,,− and a single nucleus transcriptomic analysis of AD patients’ brain revealed the upregulation of genes related to immune responses and cytokine secretion in BEC, − all suggesting that reducing inflammation in BEC could prove therapeutically useful in AD.…”

“…Interestingly, as opposed to BEC isolated from the AD patient’s brain, − in our model, we did not observe vast differences in the expression of inflammatory marker genes in AD iBEC as compared to control iBEC, suggesting a lack of a strong disease-associated inflammatory phenotype in those AD cells in vitro. Intriguingly, recently reported transcriptomic analysis demonstrated striking molecular heterogeneity of human BEC found in different brain regions, distinct segments of the arteriovenous axis and disease stages, also in relation to immune responses. ,, Therefore, it is possible that our AD hiPSC-derived iBEC could represent the BEC subpopulation with only a moderately altered immune profile in AD, highlighting the complexity of BBB neuroinflammation in AD.…”

“…Under baseline conditions, the expression of oxidative stress markers also was not altered in AD iBEC compared to control cells (Figure S6B). Collectively, these results suggest a minimal inflammatory response in AD patient-derived iBEC under normal conditions, which contrasts with previous observations for BEC in the human AD brain. − This discrepancy may be due to the specific platform and culture conditions employed for AD iBEC. To address this, we aimed to mimic the disease-associated inflammatory microenvironment observed in the AD brain by stimulating AD patient-derived iBEC with neurologically relevant proinflammatory mediators TNFα and IFNγ ,− for 24 h before conducting a range of assays (Figure A).…”

“…Interestingly, as opposed to BEC isolated from the AD patient’s brain, − in our model, we did not observe vast differences in the expression of inflammatory marker genes in AD iBEC as compared to control iBEC, suggesting a lack of a strong disease-associated inflammatory phenotype in those AD cells in vitro. Intriguingly, recently reported transcriptomic analysis demonstrated striking molecular heterogeneity of human BEC found in different brain regions, distinct segments of the arteriovenous axis and disease stages, also in relation to immune responses. ,, Therefore, it is possible that our AD hiPSC-derived iBEC could represent the BEC subpopulation with only a moderately altered immune profile in AD, highlighting the complexity of BBB neuroinflammation in AD. Correspondingly, as it is not yet known which fraction of human in vivo BEC hiPSC-derived iBEC most closely represent, future comparative transcriptomic studies would be necessary to precisely map the position of iBEC within the human vasculature atlas and define their region-specific expression profile of genes related to cytokine production/immune response at various stages of AD.…”

Landscape of brain myeloid cell transcriptome along the spatiotemporal progression of Alzheimer’s disease reveals distinct sequential responses to Aβ and tau

“…While here, we focused on brain myeloid cells, our parent study included snRNA-seq of all brain cell types. We found that microglia are relatively uniform across the neocortex, whereas astrocytes and endothelial cells have brain region-specific signatures [ 6 , 46 ]. Astrocytes develop an apparent decreased activation (“burnt out”) phenotype in end-stage disease [ 46 ], whereas we see no evidence of an analogous state for microglia.…”