CO ₂ inhalation enhances pericyte-mediated neurovascular protection in ischemic stroke and remains safe in hemorrhagic stroke

Therapeutic options for acute ischemic stroke beyond reperfusion therapy are limited by narrow time windows and associated risks. Carbon dioxide (CO 2 ), a potent and adjustable vasodilator, may preserve ischemic brain tissue by enhancing cerebral blood flow (CBF) and stabilizing neurovascular components. We investigated whether CO 2 preconditioning prior to arterial occlusion confers neuroprotection in a transient middle cerebral artery occlusion (tMCAO) model and evaluated its safety in a collagenase-induced intracerebral hemorrhage (ICH) model. Adult male rats received 20% CO 2 before tMCAO or after ICH induction. In the tMCAO model, CO 2 preconditioning improved CBF, reduced infarct size, and enhanced neurological performance (Garcia score, modified Neurological Severity Score, and rotarod). At the cellular level, CO 2 preserved pericytes (platelet-derived growth factor receptor beta (PDGFRβ)), reduced oxidative stress (8-hydroxy-2′-deoxyguanosine (8-OHdG); matrix metalloproteinase-9 (MMP-9)), and maintained blood-brain barrier integrity (zonula occludens-1 (ZO-1), occludin, and claudin-5). In the ICH model, CO 2 did not exacerbate hematoma volume or neurological deficits, suggesting a favorable safety profile. Overall, these findings indicate that CO 2 preconditioning confers multifaceted neurovascular protection in ischemic stroke without increasing the risk of hemorrhagic complications. With its rapid onset, noninvasive delivery, and translational potential, CO 2 inhalation may serve as an early, prehospital intervention to improve stroke outcomes.