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

Abstract

Background: Intraplaque 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.

Methods: Histological 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.

Conclusions: Fibrin 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.