Common hepatic lipase gene promoter variant predicts the degree of neointima formation after carotid endarterectomy: impact of plaque composition and lipoprotein phenotype.

BACKGROUND: The common -514 C-T promoter polymorphism of the hepatic lipase gene (LIPC) and the cholesteryl ester transfer protein (CETP) gene TaqIB polymorphism affect atherogenesis. We investigated the potential relationship between these polymorphisms and the maximum-intima-media thickness (M-IMT) after carotid endarterectomy. METHODS: The LIPC and CETP genotypes were determined by PCR in 68 patients undergoing endarterectomy. Plaque specimens were analysed for cell composition by immunocytochemistry. Six month after surgery the M-IMT of the revascularized vessel was assessed by B-mode ultrasonography. RESULTS: The CC carriers had denser LDL particles (p<0.0005), an abundance of macrophages (p<0.0005), fewer SMCs in the carotid plaque (p<0.0005), and higher prevalence of cerebrovascular events (72% versus 28%, p=0.002) compared to CT/TT carriers. After endarterectomy, CC carriers showed a lower M-IMT than the CT/TT group (1.36 mm versus 1.76 mm, p=0.04). No association between the CETP polymorphism and either carotid plaque cellular composition or M-IMT was observed. In a multivariate analysis, M-IMT was associated with plaque cell composition (macrophages, r=-0.39; SMC, r=0.44; p<0.005 for both) but not with pre-operative LDL-C, HDL-C, triglycerides, or LDL density. CONCLUSIONS: The LIPC promoter -514 C-T polymorphism is associated with a significantly reduced development of neointima after surgery. This effect seems to be mediated by scarcity of SMC in the plaque of CC carriers who display an excess prevalence of cerebrovascular events prior endarterectomy but are at low risk for restenosis. The pre-operative lipid phenotype plays a marginal role in the neointima formation.

Prevalence of fetal-type smooth muscle cells in the media of microvessels from hypertensive patients.

Significant structural and functional changes in smooth muscle cells (SMCs) of microvessels (diameter 30 to 300 microm) occur in hypertension. However, in microvessels of hypertensive patients, the differentiation pattern of SMCs underlying such changes remains undefined. To analyze the differentiation pattern of SMCs (adult, postnatal, or fetal), 49 muscle biopsies (rectus abdominis) were analyzed: 16 from children (aged 11 months to 11 years), 15 from normotensive adults (aged 55 to 74 years), 18 from hypertensive adults (aged 55 to 74 years). Transverse cryosections of specimens were studied by immunocytochemistry using monoclonal antibodies SM-E7 and NM-F6, which recognize smooth muscle myosin heavy chain (MyHC) and A(pla1)-like nonmuscle MyHC, respectively. The total number of microvessels was assessed via SM-E7 staining. The number of NM-F6 positive (fetal-type SMC) or negative (adult-type SMC) microvessels was assessed. The number of microvessels per area unit was considerably lower (P<0.0005) in normotensive adults (0.22+/-0.17) than in children (0.98+/-0.61). Even more significant reduction was found in hypertensive adults compared with control adults (P=0.013) and children (P<0.0005). The qualitative immunocytochemistry analysis by NM-F6 revealed 2 differentiation patterns of the media layer of microvessels: positive or negative. In hypertensive subjects, the percentage of microvessels positive to NM-F6 was 49.8+/-35.6%, close to that found in children (50.6+/-12.6%), whereas in normotensive subjects it was significantly lower (24.4+/-21.1%). The following conclusions were drawn. (1) The medial layer of microvessels is heterogeneous in terms of SMC differentiation. (2) In hypertension, a prevalence of fetal-type SMCs takes place in microvessels, resembling that of children. Compared with children, a rarefaction of microvessels is present in normotensive adults that is even more remarkable in hypertensive adults.

Role of platelet activation in catheter-induced vascular wall injury.

PURPOSE: To investigate the role of smooth muscle cell (SMC) response and platelet activation in peripheral venous catheterization using a model of catheter injury associated with thrombocytopenic treatment. METHODS: Silicon elastic catheters were inserted into New Zealand White rabbit external jugular veins from 24 hours to 60 days. Immunocytochemical procedures with antibodies to differentiation markers specific for SMCs, myofibroblasts, and endothelial cells were used to ascertain the phenotypic features of injured venous SMCs and the tissue sleeve formed around the catheter. Thrombocytopenia was induced in rabbits by busulfan treatment and the effect on catheter injury development examined after 15 days. The putative direct effect of this drug on the venous SMC proliferation, migration, and differentiation was assayed in vitro for 48 hours. RESULTS: Catheter injury is characterized by the progressive formation of (1) a neointima, containing differentiating SMCs, which are derived from the media and adventitial layer, and (2) by the organizing thrombus formed around the catheter, which contains myofibroblasts. In busulfan-treated thrombocytopenic animals, there was no evidence for either neointimal development or thrombus formation. A direct role of this drug in the unresponsiveness of vascular wall can be excluded by the unchanged proliferation and migration pattern of cultured venous SMCs treated with busulfan compared to control cultures. CONCLUSIONS: In our model, accumulation of differentiated SMCs in the neointima and myofibroblast appearance in the thrombus are linked, although distinct, events regulated by platelet activation, which is able to furnish the appropriate microenvironment for vascular SMC recruitment from the media/adventitial layer.

C-reactive protein and interleukin-6 in vascular disease: culprits or passive bystanders?

Recent advances in basic science have shown that atherosclerosis should be considered as a chronic inflammatory process, and that a pivotal role of inflammation is evident from initiation through progression and complication of atherosclerosis. In the past few years many studies have examined the potential for biochemical markers of inflammation to act as predictors of coronary heart disease (CHD) risk in a variety of clinical settings. Several large, prospective epidemiological studies have shown consistently that C-reactive protein (CRP) and interleukin-6 (IL-6) plasma levels are strong independent predictors of risk of future cardiovascular events, both in patients with a history of CHD and in apparently healthy subjects. These molecules could be useful to complement traditional risk factors, as well as to identify new categories of subjects prone to atherosclerosis development. An intriguing question is whether these inflammatory molecules simply represent sensitive markers of systemic inflammation or if they actively contribute to atherosclerotic lesion formation and instability. In this paper we will review the evidence concerning the cardiovascular prognostic value and the potential direct involvement of CRP and IL-6 in atherogenesis.

Cell characterization of porcine aortic valve and decellularized leaflets repopulated with aortic valve interstitial cells: the VESALIO Project (Vitalitate Exornatum Succedaneum Aorticum Labore Ingenioso Obtenibitur).

BACKGROUND: Heart valve bioprostheses for cardiac valve replacement are fabricated by xeno- or allograft tissues. Decellularization techniques and tissue engineering technologies applied to these tissues might contribute to the reduction in risk of calcification and immune response. Surprisingly, there are few data on the cell phenotypes obtained after cellularizing these naturally-derived biomaterials in comparison to those expressed in the intact valve. METHODS: Aortic valve interstitial cells (VIC) were used to repopulate the corresponding valve leaflets after a novel decellularization procedure based on the use of ionic and nonionic detergents. VIC from leaflet microexplants at the third passage were utilized to repopulate the decellularized leaflets. Intact, decellularized and repopulated valve leaflets and cultured VIC were examined by immunocytochemical procedures with a panel of antibodies to smooth muscle and nonmuscle differentiation antigens. Intact and cellularized leaflets were also investigated with Western blotting and transmission electron microscopy, respectively. RESULTS: Myofibroblasts and smooth muscle cells (SMC) were mostly localized to the ventricularis of the leaflet whereas fibroblasts were dispersed unevenly. Cultured VIC were comprised of myofibroblasts and fibroblasts with no evidence of endothelial cells and SMC. Two weeks after VIC seeding into decellularized leaflets, grafted cells were found penetrating the bioscaffold. The immunophenotypic and ultrastructural properties of the grafted cells indicated that a VIC heterogeneous mesenchymal cell population was present: fibroblasts, myofibroblasts, SMC, and endothelial cells. CONCLUSIONS: VIC seeding on detergent-treated valve bioscaffolds has the cellular potential to reconstruct a viable aortic valve.

New markers of accelerated atherosclerosis in end-stage renal disease.

Over the last two decades, several studies have reported a high prevalence of cardiovascular disease in patients with end-stage renal disease (ESRD). This population usually presents both the traditional and non-traditional risk factors for atherosclerosis. Inflammation as well as impaired nitric oxide production are pivotal, throughout the whole process of development of atherosclerotic lesions from the very start. C-reactive protein (CRP), a marker of systemic inflammation and an independent predictor of cardiovascular mortality in the general population, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase, are important risk factors for cardiovascular disease and mortality in the ESRD population. Increased CRP levels have been described in hemo-dialysis and peritoneal dialysis patients, probably due to concomitant diseases, recurrent infections and chronic dialytic therapy. CRP levels, however, are elevated even in predialysis patients, implying that factors related to uremia per se can promote CRP synthesis. Recent reports raise the question whether CRP could be more than just a sensitive marker of inflammation and may contribute actively to the development of the atherosclerotic lesion. ADMA accumulation in the ESRD population is a consequence of reduced renal excretion and impaired enzymatic degradation and is related to the progression of atherosclerosis. Both CRP and ADMA have been shown to be associated with increases in the incidence and progression of atherosclerotic lesions in carotid arteries, as evaluated by high-resolution Doppler ultrasonography.