Immunolocalisation of fibrin in coronary atherosclerosis: implications for necrotic core development

SummaryBackgroundIntraplaque haemorrhage has been shown to be important in necrotic core enlargement. Immunolocalisation of fibrin within progressive stages of plaque progression has not been extensively studied.MethodsHistological sections (n = 74) of human coronary arteries were stained immunohistochemically for fibrin II, red blood cell antigen (glycophorin A), and CD31. Plaques were chosen to represent a range of lesions [6 adaptive intimal thickening, AIT (AHA grade I); 4 intimal xanthomas (AHA grade II), 19 pathologic intimal thickening, PIT (AHA grade III, or pre-atheroma); 34 fibroatheromas, FA (AHA grade IV and V); and 11 thin cap fibroatheromas (TCFA, AHA grade IV)]. Results: Fibrin was generally absent in the intima of AIT and PIT, with moderate staining in cores of early FA (2.6 ± 0.3). All late FA and TCFA demonstrated intracore fibrin, with mean scores of 2.9 ± 0.3 and 3.0 ± 0.3, respectively. Intimal vasa vasorum counts increased with intimal fibrin score (p < 0.0001); in 68% of cores with fibrin staining, there was minimal or no evidence of red cell breakdown.ConclusionsFibrin in necrotic cores is present proportional to intraplaque vasa vasorum and before red cells, suggesting leakage of vessels before frank intraplaque haemorrhage. Fibrin may play a role in the bridge between pre-atheroma and atheroma.