C-reactive protein expression in acute ischemic stroke blood clots: Implications for etiology

C-reactive protein (CRP) is a prototypic inflammation marker, with elevated levels associated with an increased risk of cerebrovascular events. To determine whether CRP could be a useful biomarker of stroke etiology, we investigated CRP expression in acute ischemic stroke (AIS) clots from large-artery atherosclerosis (LAA), cardio-embolism (CE) and cryptogenic (Crypt) subtypes.

We analysed clot samples from AIS patients (LAA, CE, Crypt; n = 50 each), collected across five stroke centres in France, Serbia, Spain, and Japan between February 2021 and February 2024, as part of the prospective Clotbase International Registry of 460 patients who underwent mechanical thrombectomy. Clot components were assessed using Martius Scarlet Blue staining. CRP expression was examined using immunohistochemistry and its co-localisation with clot components was detected using immunofluorescence. Clinical parameters were compared across etiologies.

CRP expression varied significantly among clots. Most clots (65%) had minimal (⩽1%) CRP and 35% showed substantial (>1%) CRP. CE group had significantly more clots with substantial CRP than LAA and Crypt (48% vs 30% and 26%; p = 0.048). Clots with substantial CRP contained more fibrin (28.9%) than those with low CRP (20.6%; p = 0.005). Confocal microscopy showed CRP co-localised with fibrin and white blood cells (WBCs).

Significantly more AIS clots of CE expressed substantial CRP compared to those of LAA and Crypt, suggesting CE strokes may be more strongly linked to inflammation. Clots with substantial CRP expression displayed significantly more fibrin compared to those with minimal CRP expression, suggesting a potential association between inflammation and fibrin-rich clots. Further study of the relationship between CRP, fibrin and WBCs in clots may improve our understanding of the processes of thrombo-inflammation.