Sex-specific cell death mechanisms in rodent sub-acute and chronic stroke

To characterize subacute and chronic effects of sex as a biological variable in the severity and pathophysiology of stroke, ten male and ten female animals (>230 g and 2-4 months old) underwent photothrombotic infarction at the sensorimotor cortex. Lesion volume was calculated two- and four-weeks post-stroke (5 animals/sex/timepoint). The perilesional area was stained for active caspase-8, apoptosis-inducing factor (AIF), and Iba-1 expression at each timepoint. Males demonstrated significantly larger lesion volume than females at both two- (male: 11.2 mm³ vs female: 7.3 mm³, p = 0.02) and four-week (male: 9.3 mm³ vs female: 4.7 mm³, p = 0.008). The median caspase-8/AIF ratio was significantly higher in females as compared to males at two weeks (male: 0.59 vs female: 2.1, p = 0.02), however this difference was no longer present at the four-week (male: 6.0 vs female: 6.2, p = 0.56). At two weeks post-stroke, Iba1 signal in males was significantly greater than in females (male: 13.7 % vs female: 3.2 %, p = 0.0008). Although expression decreased in males at four weeks (p = 0.008), there was still a trend towards greater Iba-1 signal in comparison to females (male: 5.2 vs female: 2.8, p = 0.06). In the subacute stage, males showed a pattern consistent with parthanatos and higher neuroinflammation, while females showed a pattern consistent with caspase-8-mediated apoptosis. In the chronic stage, both sexes exhibit reduction in neuroinflammation and caspase-predominant cell death. These exploratory findings highlight potential sex-based differences in neuronal death patterns that may be influenced by microglial activity and may warrant consideration in future treatment-related studies.