Abstract TP306: Anemia Causes Hematoma Expansion, Cerebral Hypoxia-Driven Microglial Activation, and Early Mortality in Mice with Intracerebral Hemorrhage

Anemic intracerebral hemorrhage (ICH) patients are observed to have poor clinical outcomes with increased risk of hematoma expansion (HE) and impaired cerebral oxygenation. To assess whether anemia causes these observations, we assessed neuroimaging evidence of HE and neuropathological changes of hypoxia and blood brain barrier (BBB) dysfunction in anemic vs non-anemic mice with ICH. Anemia was generated in 3 month old female C57/BL6 mice using iron-deficient chow. Age and sex-matched controls were fed iron-replete control diet. Anemia was verified using modified Drabkin assays. Collagenase was used to induce ICH. ICH volume and HE were quantified using serial T2-weighed MRI at 1, 4, and 24 hours after ICH. Early 24 hour mortality was recorded. After the last MRI, surviving mice were euthanized by intracardiac perfusion and the brain was processed for histological analysis of vascular permeability (IgG), microglia number and activation (Iba1 and CD68), and response to hypoxia (HIF1α). Statistical analyses were performed using two-tailed ANOVA. Compared to controls, anemic mice displayed larger final ICH lesion volumes (anemia: 7.7 mm 3 vs control: 6.1 mm 3 ), greater HE at 24 hours (anemia: 111.4% vs control: 23.6%) and increased early mortality (anemia: 30% vs control: 0%). Histological analyses revealed that, while microglial activation and BBB permeability to serum IgGs in control mice were restricted to the ipsilateral hemisphere and mostly localized perilesionally, anemic mice had increased immune infiltration and increased BBB permeability in both hemispheres. Similarly, non-ICH anemic mice showed increased and widespread immune cell infiltration and increased BBB permeability compared to non-ICH control mice, suggesting that consistently low hemoglobin concentrations may increase cerebrovascular susceptibility to injury.Future studies will be needed to further clarify cellular and molecular mechanisms driving our findings and whether anemia can be a treatable target to improve ICH outcomes.