Circulating CD14+CD16− classical monocytes do not associate with a vulnerable plaque phenotype, and do not predict secondary events in severe atherosclerotic patients

Abstract

Mouse studies have established distinct monocyte subtypes that participate in the process of atherosclerotic lesion formation. The pro-inflammatory Ly6C high monocyte subtype actively contributes to murine plaque progression and destabilization. Also in humans, different peripheral monocyte subtypes have been identified, of which the CD14 + CD16 − classical monocyte is suggested to display similar pro-atherosclerotic properties as the murine Ly6C high subtype. We aimed to investigate if circulating CD14 + CD16 − classical monocytes associate with characteristics of a vulnerable carotid atherosclerotic plaque and if they associate with the risk of secondary adverse manifestations of atherosclerotic disease. Methods and results: We enrolled 175 carotid endarterectomy patients of the Athero-Express biobank in our study. Just prior to surgical procedure, blood was collected and peripheral blood mononuclear cells were isolated. Characterization of monocyte subsets was performed by flow cytometry. Plaque characteristics were semiquantitatively scored for the presence of fat, collagen, intraplaque hemorrhage and calcification. Vessel density, smooth muscle cells and macrophages were assessed quantitatively on a continuous scale. All features of a vulnerable plaque phenotype, including low amounts of collagen and smooth muscle cells, and increased fat content, vessel density, intraplaque hemorrhage and plaque macrophages were not significantly associated with differential levels of peripheral classical CD14 + CD16 − monocytes or other monocyte subsets. Using Cox regression models to evaluate the prognostic value of circulating monocyte subtypes, we found that total counts of peripheral monocytes, as well as CD14 + CD16 − classical and other monocyte subtypes were not associated with the risk of secondary cardiovascular events during 3 years follow-up. Conclusion: Circulating classical CD14 + CD16 − monocytes do not associate with specific vulnerable plaque characteristics. In addition, they do not predict secondary adverse manifestations. This suggests that in patients with established carotid artery disease, the circulating monocytes do not reflect plaque characteristics and have no value in identifying patients at risk for future cardiovascular events.

Relationship between Circulating Inflammatory Monocytes and Cardiovascular Disease Measures of Carotid Intimal Thickness

“…However, monocyte recruitment may be less crucial in more severe and advanced atherosclerotic plaque 20) . Monocytes' diverse roles in different stages of atherosclerosis development may account for the contradicting results of our study and the study by Meeuwsen et al 9) . HIV infection may also contribute to the different results presented by our study and the study by Chow et al 6) .…”

“…Our study contradicted the results from a previous report that did not associate monocytes and their subsets with the risk of atherosclerosis rupture in patients with severe atherosclerosis 9) . Additionally, our results contradicted another study, which stated that, unlike non-classical monocytes, there is no significant association between intermediate monocytes and only a fraction of the total monocyte population.…”

“…However, despite compelling data, another study did not associate monocyte subsets with increased risk of atherosclerosis rupture, rendering their specific role in atherosclerosis and CVD inconclusive 9) . This contradicting result may be explained by differences in the study population and CVD severity.…”

Monocyte-chemoattractant protein-1 Levels in Human Atherosclerosis Associate with Plaque Vulnerability

“…Plaques were divided in parallel segments of 5-mm thickness perpendicular to the arterial axis and the segment with the greatest plaque burden was subjected to histopathological examination, as previously described. 34,44,45 All stained sections were examined microscopically and digitally stored. For the purposes of the current study, we explored five plaque traits that are established hallmarks of plaque vulnerability: lipid content, collagen deposition, macrophages, smooth muscle cells, and intraplaque hemorrhage.…”

“…46,47 Two independent observers manually scored stainings for these traits using previously defined semi-quantitative methods. 34,41,44,45 In brief, plaque lipid content was quantified . CC-BY-NC 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.…”