Platelets enter atherosclerotic plaque via intraplaque microvascular leakage and intraplaque hemorrhage: A histopathological study in carotid plaques

Background: Platelets foster an inflammatory environment that influences atherosclerotic lesion progression and facilitates plaque rupture, in addition to their role in acute thrombus formation. The route of entry of platelets into the atherosclerotic plaque and their exact location inside the plaque are however not completely understood. Methods and results: 188 carotid plaques were examined for the presence of platelets using immunohistochemistry (CD42b), and 76/188 (40.4%) were platelet positive. Platelets were observed in intraplaque hemorrhages, around plaque microvessels, mostly without leakage of erythrocytes; and in mural thrombi. Platelet positive staining was associated with a higher plaque microvessel density, and elevated plaque-levels of interleukin-8. Conclusion: Due to their short life span, platelets reflect recent bleeding. It can be hypothesized that platelets might serve as a marker for leaky microvessels inside atherosclerotic plaques that are at risk for development, or progression of plaque hemorrhage.