Regression of atherosclerosis is characterized by broad changes in the plaque macrophage transcriptome.

We have developed a mouse model of atherosclerotic plaque regression in which an atherosclerotic aortic arch from a hyperlipidemic donor is transplanted into a normolipidemic recipient, resulting in rapid elimination of cholesterol and monocyte-derived macrophage cells (CD68+) from transplanted vessel walls. To gain a comprehensive view of the differences in gene expression patterns in macrophages associated with regressing compared with progressing atherosclerotic plaque, we compared mRNA expression patterns in CD68+ macrophages extracted from plaque in aortic aches transplanted into normolipidemic or into hyperlipidemic recipients. In CD68+ cells from regressing plaque we observed that genes associated with the contractile apparatus responsible for cellular movement (e.g. actin and myosin) were up-regulated whereas genes related to cell adhesion (e.g. cadherins, vinculin) were down-regulated. In addition, CD68+ cells from regressing plaque were characterized by enhanced expression of genes associated with an anti-inflammatory M2 macrophage phenotype, including arginase I, CD163 and the C-lectin receptor. Our analysis suggests that in regressing plaque CD68+ cells preferentially express genes that reduce cellular adhesion, enhance cellular motility, and overall act to suppress inflammation.

A gene expression signature that classifies human atherosclerotic plaque by relative inflammation status.

BACKGROUND: Atherosclerosis is a complex disease requiring improvements in diagnostic techniques and therapeutic treatments. Both improvements will be facilitated by greater exploration of the biology of atherosclerotic plaque. To this end, we carried out large-scale gene expression analysis of human atherosclerotic lesions. METHODS AND RESULTS: Whole genome expression analysis of 101 plaques from patients with peripheral artery disease identified a robust gene signature (1514 genes) that is dominated by processes related to Toll-like receptor signaling, T-cell activation, cholesterol efflux, oxidative stress response, inflammatory cytokine production, vasoconstriction, and lysosomal activity. Further analysis of gene expression in microdissected carotid plaque samples revealed that this signature is differentially expressed in macrophage-rich and smooth muscle cell-containing regions. A quantitative PCR gene expression panel and inflammatory composite score were developed on the basis of the atherosclerotic plaque gene signature. When applied to serial sections of carotid plaque, the inflammatory composite score was observed to correlate with histological and morphological features related to plaque vulnerability. CONCLUSIONS: The robust mRNA expression signature identified in the present report is associated with pathological features of vulnerable atherosclerotic plaque and may be useful as a source of biomarkers and targets of novel antiatherosclerotic therapies.

Imaging of lipids in atheroma by desorption electrospray ionization mass spectrometry.

One of the hallmarks of atherosclerosis is the accumulation of lipoproteins within the wall of blood vessels. The lipid composition can vary among atheroma, even within a single individual, and is also dynamic, changing as the lesion progresses. One desirable characteristic of atheroma is their stability, as the rupture of unstable plaques can interfere with normal blood flow to the brain or heart, leading to stroke or heart attack. Desorption electrospray ionization mass spectrometry (DESI-MS) was used in this study for the profiling and imaging of arterial plaques. DESI-MS is an ambient ionization method in which a charged, nebulized solvent spray is directed a surface. In the positive and negative ion modes, sodium and chloride adducts, respectively, of diacyl glycerophosphocholines (GPChos), sphingomyelins (SMs), and hydrolyzed GPChos were detected. Also, cholesteryl esters were detected via adduct formation with ammonium cations. Finally, cholesterol was imaged in the atheroma by doping the charge labeling reagent betaine aldehyde directly into the DESI solvent spray, leading to in situ chemical derivatization of the otherwise nonionic cholesterol. DESI imaging experiments, in which the spatial distribution of the various chemical species is determined by scanning the DESI probe across an entire sample surface, revealed that there are lipid rich regions within the arterial walls, and the lipid rich regions seem to have one of two different lipid profiles. These lipid rich regions likely correspond to the areas of the tissue where lipoprotein particles have accumulated. It is also possible that the different lipid distributions may correlate with the stability or vulnerability of that particular region of the plaque.