ABSTRACT NUMBER: ESOC2026A547 THROMBUS COMPOSITION, COMPLEMENT ACTIVATION AND LIPIDOMIC PROFILE IN ACUTE ISCHEMIC STROKE

Abstract Background and aims Complement plays a pivotal role in thrombus formation and progression. We investigated thrombus composition and complement activation in serum, plasma and thrombi from patients with acute ischemic stroke (AIS). Methods Peripheral blood samples from 25 AIS patients were analyzed for lipidomics and for complement components (C3, C4, and Terminal Complement Complex-TCC) with ELISA and were compared to 21 healthy controls. Thrombi from 15 patients who underwent mechanical thrombectomy were analyzed using MSB staining and immunohistochemical fibrin and platelet (CD42b) markers. Gene and protein expression of complement-related markers (C1qA, MBL, CFB, C3d, and C9) were evaluated using qPCR, immunohistochemistry and Western blot. Results Plasma C3 and C4 levels did not differ from controls, whereas activated fragments C3a, C4d (p<0.0001) and TCC (p<0.01) were significantly increased in patients. MSB staining demonstrated thrombus heterogeneity (26% fibrin-rich, 44% erythrocyte-rich, 30% mixed composition). C3 mRNA expression was significantly elevated in cardioembolic stroke (p=0.034), with trends towards higher expression of C1qA, MBL2, CFB and C9. CD42b protein expression in platelets reached 24.6% in atherosclerotic and 25% cardioembolic groups. C1qA, C3d and C9 protein expression was higher in atherosclerotic stroke (p<0.01), while MBL and CFB remained consistently low. Serum lipidomic analysis showed that ceramide C24:1/C24:0 ratio and selected fatty acids were elevated in cardioembolic stroke. Conclusions Our findings indicate enhanced complement activation in AIS patients, independent of etiology. Cardioembolic thrombi exhibit increased complement gene expression and distinct lipid profiles. Local complement activation within the microenvironment of thrombi may contribute to mechanisms of immunothrombosis. Conflict of interest Apostolos Bacharis: nothing to disclose