Abstract TP298: Cellular Senescence and Microglial Dysfunction are Linked to Progressive Cognitive Deficits in the Chronic Phase of Ischemic Stroke

Abstract

Improvements in acute stroke treatment, including endovascular thrombectomy and critical care management, have increased survival rates after stroke. However, many survivors have significant neurological deficits, as stroke remains one of the leading causes of long-term disability. Despite this, the chronic progression and long-term sequelae of ischemic stroke pathology remains woefully understudied. This study examined long-term progressive deficits in young adult male C57Bl/6 mice at 3 and 6 months after a 60-minute transient middle cerebral artery occlusion (MCAO) or sham surgery to identify secondary injury processes, and neuropathology of chronic stroke human brains. Depressive-like behavior persisted for 6 months post-stroke (PS) (p= <0.0001). Cognitive function progressively worsened from 3 to 6 months as seen by a continual reduction in the discrimination index in the novel object recognition task (p=.0063). Deficits in memory retention in mice 6-months PS were observed using the fear-conditioning test (p=.0084). Brain atrophy was evident by MicroCT imaging. Histopathological assessment revealed increased microglial activation in the hippocampus and frontal cortex in both mouse and human brains chronically after stroke. Interestingly, we also observed microglia activation proximal to apoptotic neurons in the brains of stroke mice, as shown by TUNEL assay. TUNEL co-labeling with a neuronal marker showed the same neuronal apoptosis in human samples from patients with chronic stroke, in both the hippocampus and thalamus. Disease-associated microglial (DAM) phenotypes were marked by both increased proliferative status and senescent-like phenotypes, including elevated production of cytokines and other proinflammatory molecules. Our findings demonstrate that experimental stroke accelerates inflammaging in the brain, which induces premature senescence within the chronic infarct microenvironment. Cellular senescence and chronic neurodegenerative signatures likely contribute to progressive cognitive impairment following stroke. The chronic and evolving neurological consequences of stroke may offer viable targets for delayed treatment strategies to reduce risk of vascular dementia and neurodegenerative disease.