Diabetes impairs post-stroke angiogenesis and BBB integrity accompanied by dysregulated Slit2/Robo-CRTC1 pathway

Diabetes Mellitus (DM) is a major comorbidity that exacerbates ischemic brain injury and hinders functional recovery following stroke. Given that angiogenesis and the maintenance of blood-brain barrier (BBB) integrity are essential for neurorestoration, understanding how DM influences these processes and the molecular mechanisms involved is critical for improving clinical outcomes. To investigate these effects, a type 1 DM model was established in six-week-old mice via intraperitoneal injections of streptozotocin (60 mg/kg/day for 5 days), with success confirmed by blood glucose testing two weeks later. Focal ischemic stroke was subsequently induced using a photothrombosis model. Functional recovery was assessed using neurological scoring, the Rotarod test, and the foot-fault test. Post-stroke neovascularization was quantified via lectin injection, while BBB integrity was evaluated through IgG leakage, pericyte coverage, and the expression of tight junction proteins (Zo-1, occludin, and claudin-5). Additionally, protein expression within the Slit2/Robo/CRTC1 pathway was analyzed 1, 7, and 14 days post-stroke using immunofluorescence and western blotting. Our results demonstrated that DM significantly impaired sensorimotor recovery and hindered reparative neovascularization in the peri-infarct area. Furthermore, DM exacerbated BBB disruption, as evidenced by increased IgG leakage, reduced expression of occludin and claudin-5, and diminished pericyte coverage. Mechanistically, DM led to a decrease in Robo1 and an increase in Robo4 expression without altering Slit2 levels. Additionally, DM further suppressed the expression of the co-transcription factor CRTC1 following the ischemic event. Our findings indicate that DM impairs post-stroke angiogenesis and BBB repair accompanied by the dysregulation of the Slit2/Robo/CRTC1 signalling pathway. These results highlight a potential therapeutic target for enhancing stroke recovery in diabetic populations.