Abstract DP072: Neuroprotective Effects of Tissue Kallikrein Against Acute Ischemic Injury in Experimental Stroke

Introduction: Tissue Kallikrein（TK）shows therapeutic potential in acute ischemic stroke (AIS) patients, but its mechanisms of action requires further exploration. This study aims to elucidate the mechanistic effects of TK in experimental ischemic stroke. Methods: Transient middle cerebral artery occlusion (tMCAO) was induced in male C57BL/6 mice using the intraluminal filament method (60-min occlusion). Human urinary kallidinogenase (HUK, a human urine-derived TK) was administered intravenously at 10 min post-perfusion. Regional cerebral blood flow (rCBF) was monitored before occlusion and throughout ischemia/reperfusion (I/R). Infarct volumes were quantified by 2,3,5-triphenyltetrazolium chloride (TTC) staining at 24 h and by T2-weighted MRI (T2W-MRI) at 48 h after ischemia. Neurological function was assessed using the modified Garcia score. Real-time in vivo arteriolar dynamics after I/R were evaluated by two-photon microscopy. Fluorescence micro-optical sectioning tomography (fMOST) in CX3cr1-2A-EGFP transgenic mice was used to image microvasculature and microglia in the ischemic hemisphere. Single-cell RNA sequencing (scRNA-seq) profiled transcriptomic changes following TK treatment. Results: TK significantly reduced infarct volumes at 24 h (TTC) and 48 h (T2W-MRI) post-ischemia and improved neurological deficits compared with vehicle-treated mice. TK enhanced rCBF at 24 h and 7 days after reperfusion. Two-photon imaging revealed greater cerebral arteriolar dilation in TK-treated mice, detectable as early as 3 h post-reperfusion. fMOST demonstrated increased total microvascular length with TK. scRNA-seq indicated increased endothelial and microglial cell abundance and reduced neutrophil levels in TK-treated mice. Conclusions: TK mitigates ischemic brain injury, improves cerebral perfusion, and modulates vascular and immune cellular responses in experimental stroke, supporting its potential as a therapeutic agent for AIS.