Relationship between regional aortic susceptibility to atherosclerosis and macromolecular structural stability

Pathophysiology of native coronary, vein graft, and in-stent atherosclerosis

Plaque rupture, usually of a precursor lesion known as a 'vulnerable plaque' or 'thin-cap fibroatheroma', is the leading cause of thrombosis. Less-frequent aetiologies of coronary thrombosis are erosion, observed with greatest incidence in women aged <50 years, and eruptive calcified nodules, which are occasionally identified in older individuals. Various treatments for patients with coronary artery disease, such as CABG surgery and interventional therapies, have led to accelerated atherosclerosis. These processes occur within months to years, compared with the decades that it generally takes for native disease to develop. Morphological identifiers of accelerated atherosclerosis include macrophage-derived foam cells, intraplaque haemorrhage, and thin fibrous cap. Foam-cell infiltration can be observed within 1 year of a saphenous vein graft implantation, with subsequent necrotic core formation and rupture ensuing after 7 years in over one-third of patients. Neoatherosclerosis occurs early and with greater prevalence in drug-eluting stents than in bare-metal stents and, although rare, complications of late stent thrombosis from rupture are associated with high mortality. Comparison of lesion progression in native atherosclerotic disease, atherosclerosis in saphenous vein grafts, and in-stent neoatherosclerosis provides insight into the pathogenesis of atheroma formation in natural and iatrogenic settings.

Correlation between carotid intimal/medial thickness and atherosclerosis: a point of view from pathology

A widely adopted surrogate for predicting rates of cardiovascular events involves measure of carotid intimal-medial thickness (CIMT) by B mode ultrasound, a technique available since the mid 1980s. The value of this modality remains in its ability to noninvasively assess cardiovascular risk beyond traditional factors identified by the Framingham risk score, and it is among the few available techniques for monitoring the effectiveness of pharmacotherapy on plaques. There are, however, existing limitations to this methodology. Perhaps the most important distinction is that IM thickness measurements are generally acquired in the common carotid artery, whereas advanced atherosclerotic disease occurs predominantly downstream in the internal carotid. Moreover, primary contributors to IM thickening are age and hypertension, which do not necessarily reflect the atherosclerotic process. Initiation of disease-related plaques begins as what is referred to as pathological intimal thickening; lesions characterized by the formation of lipid pools in the absence of a necrotic core. The eventual development of a necrotic core, however, is considered a key indicator of significant plaque advancement and recognized feature of lesion vulnerability. Necrotic cores are thought to arise from macrophage infiltration of lipid pools followed by secondary necrosis where defective clearance of debris, tissue disruption proteases, and intraplaque hemorrhage, likely contribute to its enlargement. Therefore, one of the primary limitations to CIMT is its inability to distinguish lesions with a necrotic core. Moreover, in most cases measures of plaque area or volume are generally considered better predictors of an inflammatory process consistent with atherosclerotic disease rather than intimal medial thickness.

RFXB and its splice variant RFXBSV mediate the antagonism between IFNgamma and TGFbeta on COL1A2 transcription in vascular smooth muscle cells

Cytokines secreted by infiltrating immune cells during atherogenesis modulate vascular remodeling. One exemplary event is the antagonism between transformed growth factor (TGF-β) and interferon gamma (IFN-γ) on the transcriptional control of type I collagen gene (COL1A2). Previously we have reported that IFN-γ up-regulates regulatory factor for X-box B (RFXB) to repress collagen transcription while down-regulates the expression of RFXBSV, a splice variant of RFXB that blocks collagen repression in fibroblasts. Here we demonstrate that TGF-β abrogated COL1A2 repression by IFN-γ through altering the relative expression of RFXB and RFXBSV. Unlike RFXB, RFXBSV did not bind to the collagen promoter and competed with RFXB for the co-repressor histone deacetylase 2 (HDAC2), limiting HDAC2 recruitment to the collagen transcription start site as evidenced by chromatin immunoprecipitation assays. Over-expression of RFXB by lentiviral infection in HASMCs enhanced HDAC2 enlistment, promoted histone deacetylation surrounding the collagen site by IFN-γ, and blocked the TGF-β antagonism, a pattern reversed by RFXBSV infection. On the contrary, silencing of RFXB, but not both RFXB and RFXBSV, expression promoted the TGF-β antagonism. Thus, we have identified a novel mechanism whereby TGF-β antagonizes the IFN-γ repression of collagen transcription in HASMCs and as such provided new insights into antiatherogenic strategies.

Heterogeneity in the composition and aggregation patterns of coronary intima acid mucopolysaccharides (glycosaminoglycans)

The thickened intima of human coronary arteries included acid mucopolysaccharides (glycosaminoglycans) with a large variety of patterns of composition and aggregation. This heterogeneity, detectable with histochemical methods, was related in our material to age, branching anatomical pattern, size of vessel, collateral or terminal character of the vessel, bifurcations, intimal histology, internal elastic membrane alterations, as well as to the onset of fatty streaks, gelatinous plaques and incorporated microthrombi.