Postischemic endothelial immune reprogramming in stroke.

Large-vessel recanalization is essential in acute ischemic stroke, but it does not guarantee microvascular reperfusion. Endothelial responses may contribute to persistent tissue hypoperfusion through leukocyte trafficking and immunothrombosis. Many of these responses may begin during ischemia and may continue or intensify when blood flow returns. We therefore use postischemic or ischemia/reperfusion-associated terminology unless experiments isolate the contribution of reperfusion. We propose that endothelial immune reprogramming requires a coordinated molecular program, localization to a defined vascular segment and time, and a corresponding change in immune-regulatory function. An isolated increase in an adhesion molecule or circulating biomarker indicates activation or injury but cannot identify such a state. Barrier/stress, adhesive/chemotactic, and prothrombotic responses overlap. Experimental studies implicate endothelial signaling, leukocyte arrest, and platelet interactions with neutrophil extracellular traps, but have not established a common sequence of endothelial states. Human evidence comes mainly from circulating biomarkers, thrombectomy thrombi, post-mortem tissue, and perfusion imaging. The available findings have yet to link a defined cerebral endothelial state to downstream perfusion and clinical outcome in the same patients. Prospective studies should combine serial vascular biomarkers, repeated perfusion imaging, and longitudinal follow-up, with endothelial-enriched molecular profiling when tissue is available. Therapeutic studies should test whether modifying a reversible endothelial program relieves no-reflow while preserving later immune resolution and vascular repair. These approaches remain investigational.