Transcriptome analysis of circulating monocytes from patients with stable plaques and patients with unstable plaques.

Multiple lines of evidence indicate an intense interaction between circulating
monocytes and atherosclerotic plaques. The role of monocyte infiltration in the
arterial wall and the differentiation into lipid-laden macrophage foam cells,
is well recognized in the pathogenesis of atherosclerosis. Macrophage foam
cells play a key role in disease progression, both as scavengers of lipid and
as inflammatory mediators. Moreover, recent literature indicates that a
substantial population of macrophage foam cells emigrates from atherosclerotic
plaques, which permits their re-entry into the blood and genes were identified
that are differentially expressed between the circulating monocytes of patients
undergoing carotid endarterectomy and normal subjects.
Studies of the mononuclear-phagocyte system using monoclonal antibodies for
cell-surface antigens (e.g. L-selectin, chemokine receptors), have shown
heterogeneity in the phenotype of monocytes and macrophages in atherosclerotic
plaques. In line with phenotypic heterogeneity, our lab has recently identified
differences between the gene expression profiles of macrophages from
atherosclerotic plaques and non-atherosclerotic macrophages isolated from
spleen, liver and lungs, demonstrating that heterogeneity is also present on
transcriptome level. Likewise, we hypothesize that an increased inflammatory
status, such as reported for vulnerable plaques, will go together with changes
in the transcriptome of blood monocytes.
Overlap between the expression profiles of the identified set of genes on the
pathway level, might give insights in the molecular mechanism of
atherosclerosis.

The primary objective is identification of a set of genes as candidate monocyte
markers for acute coronary complications and subsequent identification of a
prognosis classifier to discriminate vulnerable, stable, and control subjects,
based on the expression of the identified set of genes.

This study is an observational cross sectional study to study the differences
in the transcriptome of monocytes from stable and unstable patients using
rheumatoid arthritis patients as a control group. Unstable patients are
identified in the emergency room as highly suspected for the presence of
ruptured coronary plaques, because of a recent history of unstable angina (i.e.
with ECG abnormalities indicating subendocardial ischemia or postischemic
conditions, but without elevated levels of troponin-T), i.e. unstable angina
IIA, IIIA, IIB and IIIB-Tneg. Patients shown to have atherosclerotic lesions in
the past during coronary catheterization, treated for more than 3 months for
stable angina pectoris in the Hart-en Vaatcentrum Maastricht, but without any
history of previous AMI or cerebro-vascular event, are considered as stable
patients. As a control group for other inflammatory genes age- and gender
matched patients suffering from rheumatoide arthritis, without clinical
evidence of cardiovascular disease will be included in close cooperation with
Prof Dr P. Geussens, Internal Medicine, azM.
Monocytes will be isolated from blood that will be drawn from the patients by
venapunction. At first, of all groups at least 20 patients will be included for
transcriptome analysis on genome-wide micro-arrays. Secondly, the gene
expression results will be utilized in the design of a custom array containing
approximately 500 genes mostly related to the disease state. Then the
transcriptome of 250 patients of both the stable and unstable patient groups is
analysed. Subsequently a prognosis classifier gene-set will be designed based
on the gene-expression levels in 70% of the subjects. Finally the prognosis
classifier gene-set will be evaluated on the remaining 30% of the
gene-expression data.

The risk to and burden for the individual subjects is very low because a
venapunction is a standard procedure with negligible risks and low burden.