Phosphatidylserine (PS) exposes to the outer plasma membrane after a pathological insult (e.g., stroke) but not under normal conditions whereby PS remains within the inner plasma membrane. However, the reversibility and translational potential of PS exposure in damaged cells after stroke are still unknown. Here, we demonstrated that plasma Annexin V, which has a high affinity to membranes bearing PS, was increased in patients with salvage penumbra after endovascular therapy, and associated with early neurological improvement. Moreover, Annexin V treatment could decrease PS exposure and mitigate neurological impairments in transient ischemia/reperfusion mouse models, but not in permanent ischemia. Furthermore, we used a combination of cell, rodent, and nonhuman primate ischemia/reperfusion models and found that transmembrane protein 30A (Tmem30a) was increased in the ischemic penumbra after stroke and imperative for less PS exposure and better neurological functions. Mechanistically, mitigation of PS exposure mediated by Tmem30a/Annexin V connection led to decreased expression of apoptosis and necroptosis markers in neurons of penumbra. Overall, our findings reveal a previously unappreciated role of reducing PS exposure by Annexin V treatment in protecting the penumbra in a clinically relevant ischemia/reperfusion model. Tmem30a is essential for reducing PS exposure in the penumbra after ischemic stroke.

Keywords: Annexin V; Tmem30a; ischemic stroke; neuroprotection; penumbra; phosphatidylserine.

© 2025 The Author(s). MedComm published by Sichuan International Medical Exchange & Promotion Association (SCIMEA) and John Wiley & Sons Australia, Ltd.