Abstract
INTRODUCTION: Recent literature suggests that innate immune system effectors may drive poor patient outcomes in acute ischemic stroke (AIS) through complications such as hemorrhagic transformation. Biomarkers for these effectors can be identified through study of retrieved stroke thrombus, but as of yet, there is little knowledge on specific pathways involved in post‐stroke hemorrhagic. OBJECTIVE: In this study, we explore how the proteomic composition of AIS thromboembolic material retrieved by mechanical thrombectomy differs between patients with and without parenchymal hemorrhage. METHODS: The proteomes of 59 retrieved AIS thromboemboli were determined with mass spectrometry. Hemorrhagic transformation was defined as either symptomatic or asymptomatic ECASS II grade PH‐1/2 hemorrhage on post‐embolectomy imaging. Differential enrichment analysis was conducted to determine how relative protein abundances differed between hemorrhage‐positive (H+) and hemorrhage‐negative (H‐) patients, with |log2(fold‐change)| > 0.5 and p < 0.05 (Mann‐Whitney) describing statistically enriched or depleted proteins. The functional implications of these differences were explored using the Gene Ontology, Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome dictionaries. RESULTS: 24 out of 59 included patients (41%) demonstrated some degree of hemorrhagic transformation of their ischemic stroke. Of the 2,790 proteins detected across all specimens, 152 and 40 proteins were enriched in H+ and H‐ specimens, respectively. Complement subunits C5‐9 accounted for 5 out of the top 10 proteins most enriched in H+ specimens. Functional analysis revealed significant over‐representation of terminal complement pathways involving the membrane attack complex (MAC) and immune‐based cell killing mechanisms. CONCLUSIONS: In this study, we report an over‐representation of MAC complement proteins in the thrombi of patients who developed ECASS II parenchymal hemorrhage. This may indicate a role for complement‐mediated cytotoxicity in hemorrhagic transformation, potentially through the disruption of blood‐brain barrier cellular components following thrombectomy. This suggests a specific and potentially targetable mechanism for hemorrhagic transformation, but should be validated in direct functional assays. [Image: see text]