Mass Spectrometry Imaging as a Tool to Investigate Region Specific Lipid Alterations in Symptomatic Human Carotid Atherosclerotic Plaques.

Francesco Greco,Mauro Ferrari,Fabio A Recchia,Liam A Mcdonnell,Laura Quercioli,Angela Pucci,Silvia Rocchiccioli

doi:10.3390/metabo11040250

Abstract

Atherosclerosis is characterized by fatty plaques in large and medium sized arteries. Their rupture can causes thrombi, occlusions of downstream vessels and adverse clinical events. The investigation of atherosclerotic plaques is made difficult by their highly heterogeneous nature. Here we propose a spatially resolved approach based on matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging to investigate lipids in specific regions of atherosclerotic plaques. The method was applied to a small dataset including symptomatic and asymptomatic human carotid atherosclerosis plaques. Tissue sections of symptomatic and asymptomatic human carotid atherosclerotic plaques were analyzed by MALDI mass spectrometry imaging (MALDI MSI) of lipids, and adjacent sections analyzed by histology and immunofluorescence. These multimodal datasets were used to compare the lipid profiles of specific histopathological regions within the plaque. The lipid profiles of macrophage-rich regions and intimal vascular smooth muscle cells exhibited the largest changes associated with plaque outcome. Macrophage-rich regions from symptomatic lesions were found to be enriched in sphingomyelins, and intimal vascular smooth muscle cells of symptomatic plaques were enriched in cholesterol and cholesteryl esters. The proposed method enabled the MALDI MSI analysis of specific regions of the atherosclerotic lesion, confirming MALDI MSI as a promising tool for the investigation of histologically heterogeneous atherosclerotic plaques.

Highlights

Atherosclerosis is a chronic inflammatory disease [1] characterized by the accumulation of a fatty or fibro-fatty plaque extending from the intima to the media layer of large and medium-sized arteries [2,3]
Resolved techniques provide a better insight into the biology of atherosclerotic plaques by enabling the analysis to focus on specific actors within specific regions of the plaque
We set up a pipeline including sample preparation, matrix-assisted laser desorption/ionization (MALDI) Mass spectrometry imaging (MSI) acquisition, histology and immunofluorescence for accurate region definition, annotation transfer to the MALDI MSI data, and regionwise multivariate data analysis

Summary

Introduction

Atherosclerosis is a chronic inflammatory disease [1] characterized by the accumulation of a fatty or fibro-fatty plaque extending from the intima to the media layer of large and medium-sized arteries [2,3]. The lesion is initiated by the accumulation of low density lipoproteins (LDL) in the subendothelial matrix [3], that cause inflammation and monocyte recruitment from the bloodstream [5]. The inability to export the cholesterol derived from LDL [5] causes the death of the macrophages, which accumulate in a lipid-rich necrotic core that sustains inflammation [6]. Vascular smooth muscle cells (VSMCs) from the media layer proliferate, migrate and differentiate to produce a fibrous cap that encapsulates the lesion [7,8]. The atherosclerotic plaque is a complex and heterogeneous environment, formed by different populations of cells that interact with each other

Methods

Results

Conclusion