oa Biochemical and cellular characterization of human atherosclerotic carotid plaque and blood flow: Implications for stroke prevention

Background and Objectives: The Arabian Gulf region is rapidly developing, with major changes in lifestyle that can increase the risk of cardiovascular diseases, including stroke. Stroke constitutes a major cause of morbidity and mortality in Qatar. This research focuses mainly on ischaemic stroke, aiming to study carotid plaque morphology at biochemical, cellular and molecular levels. The objectives are to identify markers that can be measured in surrogate tissues (e.g., blood) in order to identify patients at risk of developing the criteria for clinical intervention to prevent or reduce the risk of stroke. Methods: Fifteen carotid plaques were collected from routine carotid endarterectomy surgery. A range of laboratory techniques were used, including SDS-PAGE, Western blotting, histology, immuno-histochemistry, DD-PCR, flow-modelling, bright-field and laser scanning confocal microscopy (LSCM). Results: Levels of matrix metalloproteinase-3 (MMP-3) and its precursor (pro-MMP-3) were higher in echolucent than in echogenic plaques, especially near regions of ulceration, necrosis and where the fibrous cap was thin or torn. Isoforms of nitric oxide synthase (NOS) were seen in all carotid plaques irrespective of intraplaque features however, levels of inducible NOS (NOS-II) were higher in echolucent than in echogenic plaques. Higher levels of immunoreactive superoxide dismutase were observed in plaques with higher degree of stenosis (>75%-80% measured by ultrasonography). 3D imaging using LSCM showed evidence of carotid plaque vulnerability demonstrated by reduced fibrous cap thickness and a large lipid-necrotic core with evidence of cracking. Five PCR products were identified in echogenic plaques and three PCR products were identified in echolucent plaques which were absent from echogenic plaques. Some of these PCR bands are the products of genes which appear to be up- or down-regulated during plaque development. Blood flow simulation models showed how blood velocity changes could occur associated with reduction in lumen diameter caused by the plaque. Conclusions: Our findings could help in understanding factors affecting plaque morphology. The switching 'off or on' of genes and their encoded proteins may play an important role in stabilisation or destabilisation of carotid plaques. This may lead to digestion of fibrous tissue, leading to thinning or tearing of the fibrous cap and to plaque disruption, initiating embolization and stroke.