Pericyte and microglia reprogramming in hypertensive cerebral small vessel disease

Abstract

Cerebral small vessel disease (cSVD) is the leading cause of stroke and dementia, yet its cellular and molecular mechanisms remain incompletely understood. This dissertation investigates the roles of pericytes and microglia, crucial components of the neurovascular unit, in the pathogenesis of hypertensive cSVD. Utilizing the Spontaneously Hypertensive Stroke-Prone Rat (SHRSP) model and human post-mortem brain tissue, this thesis investigates the phenotypic and metabolic changes these cells undergo under chronic hypertension. This research posits that chronic hypertension induces significant transformations in pericytes and microglia, exacerbating cSVD pathology. The aims include characterizing pericyte phenotypic alterations, investigating the metabolic profile of pericytes and their effects on blood-brain barrier (BBB) integrity, defining microglial activation states, and examining the impact of microglial reactivity on BBB dysfunction and neuroinflammation. An array of techniques was employed, including vascular and microglial single-cell isolation, immunofluorescence, flow cytometric analysis, and Seahorse XP metabolic analyses, along with gene expression profiling of vessel fragments, in vitro pericyte expansion, and extracellular vesicle (EVs) analysis. The findings in this thesis reveal the upregulation of genes involved in lipid metabolism, angiogenesis, and inflammation during early hypertension, indicating active vascular remodeling, which declines in late stages, suggesting metabolic exhaustion. Pericytes exhibit profound phenotypic and metabolic reprogramming towards glycolysis, with hypertensive plasma-derived EVs impairing mitochondrial function in control pericytes, highlighting the role of EVs in vascular pathology. Microglia show diverse phenotypic characteristics and activation states, suggesting a synergistic relationship between endothelial alterations, microglial reactivity, and aging, which contributes to cSVD. Chronic hypertension induces morphological changes in microglia, modifies BBB permeability, and promotes neuroinflammation. This dissertation proposes a novel pericyte-microglia lactate shuttle in which pericytes under hypertensive stress increase glycolysis, producing lactate that may be transferred to microglia via the MCT4 receptor. This shuttle can be crucial for understanding the metabolic dynamics of hypertensive cSVD, and represents a potential therapeutic target. This dissertation advances our understanding of cSVD pathogenesis by highlighting the potential of targeting metabolic pathways and EVs to mitigate vascular complications.