Abstract TP278: Stroke-Induced Premature Senescence Exacerbates Ischemic Injury in an Age-Dependent Manner

Age is the most influential co-morbidity in ischemic stroke. However, the mechanisms of age’s impact on stroke severity are not fully understood. In the aged brain, cells develop a senescence associated secretory phenotype (SASP) which induces neuroinflammation and further increases senescent cells (SC) via paracrine signaling. While there is a baseline amount of SC’s as one ages, evidence shows an outside insult, e.g. stroke, traumatic brain injury, infection, causes a stroke-induced premature senescent (SIPS) event. This forces healthy cells into SC’s, propagating brain injury and weakening neuroprotective mechanisms via SASP release. We have previously found that after a stroke there is a marked increase in markers of cellular senescence and senescent cells, especially in the ischemic penumbra. From this, we hypothesize that in addition to normal penumbra after stroke, there is also a critical senescent penumbra of senescent cells that directly underline stroke severity and rate of damage. To characterize the senescent penumbra and better understand its link to stroke severity and outcome, we conducted post-stroke spatiotemporal analysis in young vs aged mice. Middle cerebral artery occlusion was induced in young (8 week) and aged (18 month) C57BL/J6 male mice using the photothrombotic model. Brains were perfused and then the hemispheres were harvested and fresh frozen separately for protein and mRNA analysis of markers of SASP, senescence, and inflammation via western blot, qPCR, and immunofluorescence. Western blot and qPCR analysis of SASP and inflammatory markers demonstrated that the expression of SASP markers (CXCR2, CXCL1, IL-1α) showed age-based differential expression with a higher degree of senescence in the young-stroked animals. Additionally, this difference continued in inflammatory (IL-6, TNFa) and senescent markers (p16, p21, p53). Further temporal analysis of aged-stroked animals showed a distinct presentation of SASP, and inflammatory markers divided between the infarct formation and post-formed quasi sub-acute phase. We have found that ischemic stroke increases SASP and senescence in an age-dependent manner, acute inflammation and SASP correspond to increased senescent cells, and that stroke-induced premature senescence in aged mice is mainly derived via a DNA-damage mediated pathway further inducing nuclear damage. Further analysis on the impact of senescence on stroke severity is analyzed via intervention with the senomorphic ABT-263.