Source‐dependent variability in gut barrier disruption, bacterial translocation, and immune activation after ischemic stroke in Wistar rats

Stroke induces profound neuroinflammation and systemic immune dysregulation, including disturbances in gut homeostasis. Experimental evidence suggests that intestinal barrier permeability (IBP) and bacterial translocation (BT) critically influence stroke outcomes. However, biological variability among commonly used rodent substrains has received limited attention. In this pilot study, we compared poststroke immune responses in two Wistar rat substrains obtained from different suppliers: RccHan (Envigo) and RjHan (Janvier). Naive animals (n = 4) and rats subjected to permanent cerebral ischemia (n = 8 per substrain) were evaluated 72 h after middle cerebral artery occlusion and stratified according to the presence or absence of BT. Immune cell populations in blood and bone marrow were analyzed using flow cytometry, and leukocyte infiltration into ischemic brain tissue was quantified using immunohistochemistry. Differences were considered statistically significant when p < 0.05. Both substrains developed significant infarcts and neurological deficits. RccHan rats exhibited larger infarct volumes and more extensive BT across multiple organs. In contrast, RjHan rats exhibited BT mainly confined to mesenteric lymph nodes but exhibited greater IBP. Although dissemination was broader in RccHan rats, overall bacterial burden was slightly lower compared with RjHan, and extraintestinal bacterial composition differed between groups. Particularly, RjHan rats exhibited stronger systemic and central immune activation, with significant alterations in lymphocyte and monocyte populations and enhanced granulocyte and T-cell infiltration within ischemic lesions. These findings demonstrate that substrain origin profoundly influences poststroke intestinal barrier integrity, bacterial dissemination, and immune responses considering substrain-related variability is essential to improve reproducibility and translational relevance in preclinical stroke research.