Jason C. Kovacic

Impact of the everolimus-eluting stent on stent thrombosis: a meta-analysis of 13 randomized trials

OBJECTIVES We evaluated the impact of the everolimus-eluting stent (EES) on the frequency of stent thrombosis (ST), target vessel revascularization (TVR), myocardial infarction (MI), and cardiac death in randomized controlled trials comparing the EES to non-everolimus-eluting drug-eluting stents (EE-DES). BACKGROUND Whether or not the unique properties of the EES translate into reductions in ST remains unknown. METHODS We searched MEDLINE, Scopus, the Cochrane Library, and Internet sources for articles comparing outcomes between EES and non-EE-DES without language or date restriction. Randomized controlled trials reporting the frequency of ST were included. Variables relating to patient and study characteristics and clinical endpoints were extracted. RESULTS We identified 13 randomized trials (n = 17,101) with a weighted mean follow-up of 21.7 months. Compared with non-EE-DES, the EES significantly reduced ST (relative risk [RR]: 0.55; 95% confidence interval [CI]: 0.38 to 0.78; p = 0.001), TVR (RR: 0.77; 95% CI: 0.64 to 0.92; p = 0.004), and MI (RR: 0.78; 95% CI: 0.64 to 0.96; p = 0.02). There was no difference in cardiac mortality between the groups (RR: 0.92; 95% CI: 0.74 to 1.16; p = 0.38). The treatment effect was consistent by different follow-up times and duration of clopidogrel use. The treatment effects increased with higher baseline risks of the respective control groups with the strongest correlation observed for ST (R(2) = 0.89, p < 0.001). CONCLUSIONS Intracoronary implantation of the EES is associated with highly significant reductions in ST with concordant reductions in TVR and MI compared to non-EE-DES. Whether these effects apply to different patient subgroups and DES types merits further investigation.

Epithelial-to-Mesenchymal and Endothelial-to-Mesenchymal Transition From Cardiovascular Development to Disease

Cellular switching from an epithelial-to-mesenchymal phenotype, and conversely from a mesenchymal-to-epithelial phenotype, are important biological programs that are operative from conception to death in mammalian organisms. Indeed, the capacity of cells to switch between these states has been fundamental to the generation of complex body patterns throughout evolution. Phenotypic switching from an epithelial to mesenchymal cell, termed epithelial-to-mesenchymal transition (EMT), was a paradigm that evolved from numerous observations on early embryonic development, the foundations of which date back to the 1920s and the pioneering work of Johannes Holtfreter on embryo formation and differentiation.1,2 By the late 1960s, seminal chick embryo studies by Elizabeth Hay3 led to the first formal description that epithelial cells can undergo a dramatic phenotypic transformation and give rise to embryonic mesoderm.4 Subsequent studies have revealed that this process is reversible (mesenchymal-to-epithelial transition [MET]), and gradually the term ‘transition” has come to replace ‘transformation.” Given that EMT/MET was initially identified and described by developmental biologists, it is perhaps not surprising that these processes are best understood during embryonic implantation and development. As explored in this review, it is now known that successive waves of cellular transition, from an epithelial to mesenchymal and then back to an epithelial state, are required for normal embryonic patterning and organ formation. In addition, numerous studies that span a broad spectrum of physiological and pathological conditions have expanded our knowledge of EMT/MET and now provide evidence for the important role played by these processes in various adult conditions including fibrosis, wound repair, inflammation, and malignancy. Indeed, our conceptual framework now also encompasses several variations and subcategories of cellular phenotypic switching, including endothelial-to-mesenchymal transition (EndMT). In this review, epithelial, endothelial, and mesenchymal phenotypic cellular switching will be explored in the cardiovascular system, spanning cardiovascular development through to adult …

Cellular Senescence, Vascular Disease, and Aging: Part 2 of a 2-Part Review: Clinical Vascular Disease in the Elderly

The increasing prevalence of older-age people in our society represents the culmination of centuries of medical, scientific, and social endeavors. At least in Western society, now relatively freed from pestilence, abject poverty, gross malnutrition, and polluted water and food sources, an increasing proportion of the population can expect to make it to old age. However, although US age-adjusted death rates from cardiovascular disease, coronary heart disease, and stroke continue to fall, a disproportionate number of people who reach old age (80% of people aged 80 years) suffer from these diseases.1a In this 2-part review, we consider important pathobiological changes that occur with aging in the cardiovascular system, exploring promising areas of recent scientific progress and novel insights that may be translatable into targeted clinical strategies to help to alleviate the excess morbidity and mortality imposed by cardiovascular disease in the elderly. In this second installment, we focus specifically on vascular disease states of the elderly, including systolic hypertension, vascular calcification, and dementia, and we review relevant basic and clinical discoveries that further elucidate these conditions. Hardening of the Arteries: Calcification, Glycosylation, and the Vasculature in Old Age The Elderly Vascular Phenotype Aging is associated with various changes in the vascular system at differing structural and functional levels. At the macroscopic level, an increase in arterial lumen size and arterial wall thickening, mainly of the intima, are observed. 2 In addition, increased vascular calcification and a generalized stiffening of the arterial tree lead to increased arterial wave reflectance, increased systolic blood pressure, decreased diastolic blood pressure, and a widened pulse pressure. An interesting aspect of vascular biology in which significant inroads have been made is our understanding of pulse wave velocity, which is partly a consequence and partly a cause of the elderly vascular phenotype. In the healthy human arterial tree, the arterial pulse wave is reflected back toward the heart from branch points and other structures in the peripheral circulation, with the reflected wave arriving back at the aortic root during diastole. In older people, the stiffening of the vasculature results in higher forward and reflected pulse wave velocities, with the reflected wave arriving back at the aortic root in late systole, leading to an augmentation of the late systolic pressure (Figure 1). 3 This

TGF-β Signaling Mediates Endothelial-to-Mesenchymal Transition (EndMT) During Vein Graft Remodeling

In vivo endothelial cell fate mapping demonstrates that TGF-β signaling is a central pathway regulating the endothelial-to-mesenchymal transition (EndMT) during vein graft remodeling. Negative Remodeling In coronary bypass surgery, veins are grafted to arteries, in hopes of generating a functional vessel. Although a routine procedure, grafting can result in a negative remodeling process—with a poorly understood underlying mechanism. Here, Cooley and colleagues linked vein graft stenosis (blood vessel narrowing) and negative remodeling to a process called the endothelial-to-mesenchymal transition (EndMT). Although well known during development, the presence of EndMT in the vasculature is less documented and therefore represents a possible new target in preventing graft failure. The authors tracked endothelial cells in mice using yellow fluorescent protein (YFP), and saw that these cells lining the vessel walls contributed to arterial thickening (neointima formation) after vein grafting by first converting to mesenchymal cells. EndMT occurred via transforming growth factor–β (TGF-β) signaling, specifically through intermediates Smad2/3 and Slug. Knowing the pathway at play is important for translation to the clinic because therapeutics can be designed to target these signaling molecules. Indeed, the authors found that blocking TGF-β with an antibody or knocking down Smad2 in vivo in mice prevented EndMT. The mesenchymal transition was also noted in failed vein grafts taken from patients, suggesting that EndMT is also present in humans and contributes to graft failure and restenosis. More testing is required in human samples to confirm the mouse data, but EndMT appears to be a viable target for improving graft outcomes after surgery in patients. Veins grafted into an arterial environment undergo a complex vascular remodeling process. Pathologic vascular remodeling often results in stenosed or occluded conduit grafts. Understanding this complex process is important for improving the outcome of patients with coronary and peripheral artery disease undergoing surgical revascularization. Using in vivo murine cell lineage–tracing models, we show that endothelial-derived cells contribute to neointimal formation through endothelial-to-mesenchymal transition (EndMT), which is dependent on early activation of the Smad2/3-Slug signaling pathway. Antagonism of transforming growth factor–β (TGF-β) signaling by TGF-β neutralizing antibody, short hairpin RNA–mediated Smad3 or Smad2 knockdown, Smad3 haploinsufficiency, or endothelial cell–specific Smad2 deletion resulted in decreased EndMT and less neointimal formation compared to controls. Histological examination of postmortem human vein graft tissue corroborated the changes observed in our mouse vein graft model, suggesting that EndMT is operative during human vein graft remodeling. These data establish that EndMT is an important mechanism underlying neointimal formation in interpositional vein grafts, and identifies the TGF-β–Smad2/3–Slug signaling pathway as a potential therapeutic target to prevent clinical vein graft stenosis.

Cellular Senescence, Vascular Disease, and Aging Part 1 of a 2-Part Review

> Longevity is a vascular question, which has been well expressed in the axiom that man is only as old as his arteries. To a majority of men death comes primarily or secondarily through this portal. The onset of what may be called physiological arterio-sclerosis depends, in the first place, on the quality of arterial tissue which the individual has inherited, and secondarily on the amount of wear and tear to which he has subjected it. > > —Sir William Osler, 18911 In 2030, when all of the baby boomer generation will be ≥65 years of age, nearly 1 in 5 US residents is expected to be >65 years of age. By 2050, this age group is projected to more than double in number, from 38.7 million in 2008 to an estimated 88.5 million (Figure 1).2 Similarly, the population ≥85 years of age is expected to more than triple, from 5.4 million in 2008 to 19 million by 2050.2 With this aging of the population, the number of people at risk for adverse cardiovascular events, in particular atherothrombosis, stroke, myocardial infarction, and heart failure, will increase dramatically. The importance of these projections is underscored by the fact that currently, although octogenarians represent only 5% of the US population, they account for 20% of all hospitalizations for myocardial infarction and 30% of all myocardial infarction–related deaths.3 Figure 1. Projected US population demographics by age and sex in 2010 (top), 2030 (middle), and 2050 (bottom). The baby boomer cohort (Baby Boom) is also highlighted. Source: Population Division, US Census Bureau.2 Despite their increased risk of adverse cardiac events, elderly patients are less likely to receive appropriate therapy. This paradox is perhaps related to the fact that elderly patients with cardiovascular disease are more likely to be frail.4 Heightened concerns that frail older patients may be …

Effect of pravastatin on body composition and markers of cardiovascular disease in HIV-infected men--a randomized, placebo-controlled study.

Objectives:To determine the effect of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, pravastatin, on markers of cardiovascular risk and lipodystrophy in HIV-infected, protease inhibitor (PI)-treated men with hypercholesterolaemia. Methods:A randomized, placebo-controlled, 16-week study was carried out on 33 HIV-infected, hypercholesterolaemic men (fasting total cholesterol > 6.5mmol/L) on PI-containing therapy. Patients commenced dietary assessment and advice at week 0 and were randomized to 12 weeks pravastatin (40 mg each night) or placebo from week 4. The primary endpoint was the time-weighted change (TWAUC) in total cholesterol from week 0. Secondary endpoints included TWAUC cholesterol from week 4 (start of pravastatin), total and regional body fat, fasting lipids, glucose, insulin, and markers of cardiovascular risk. Results:Of 33 men randomized (pravastatin n = 16, mean age 48 years), 31 completed the study. Groups were matched for baseline cholesterol and body composition. Although there was no significant between-group difference in TWAUC cholesterol from week 0 (pravastatin −0.6 ± 1.0 versus placebo −0.4 ± 1.0 mmol/L/week; P = 0.8), TWAUC cholesterol from week 4 decreased more in the pravastatin group (−0.8 ± 1.0 versus −0.3 ± 0.9 mmol/L/week; P = 0.04). Neither triglycerides nor dietary intake changed. Subcutaneous fat increased significantly with pravastatin (+0.72 ± 1.55 versus +0.19 ± 0.48 kg change in limb fat, P < 0.04; +5.2 ± 8.7 versus −1.3 ± 13.7 cm2 change in abdominal subcutaneous fat, P = 0.02). Apart from homocystine, which decreased in the pravastatin group, there were no significant differences in other cardiovascular, lipid or glucose parameters. Conclusions:Despite limited effects on cholesterol, 12 weeks use of pravastatin 40 mg each night in HIV-infected men with hypercholesterolaemia resulted in significant increases in subcutaneous fat.

Stat3-dependent acute Rantes production in vascular smooth muscle cells modulates inflammation following arterial injury in mice

Inflammation is a key component of arterial injury, with VSMC proliferation and neointimal formation serving as the final outcomes of this process. However, the acute events transpiring immediately after arterial injury that establish the blueprint for this inflammatory program are largely unknown. We therefore studied these events in mice and found that immediately following arterial injury, medial VSMCs upregulated Rantes in an acute manner dependent on Stat3 and NF-kappaB (p65 subunit). This led to early T cell and macrophage recruitment, processes also under the regulation of the cyclin-dependent kinase inhibitor p21Cip1. Unique to VSMCs, Rantes production was initiated by Tnf-alpha, but not by Il-6/gp130. This Rantes production was dependent on the binding of a p65/Stat3 complex to NF-kappaB-binding sites within the Rantes promoter, with shRNA knockdown of either Stat3 or p65 markedly attenuating Rantes production. In vivo, acute NF-kappaB and Stat3 activation in medial VSMCs was identified, with acute Rantes production after injury substantially reduced in Tnfa-/- mice compared with controls. Finally, we generated mice with SMC-specific conditional Stat3 deficiency and confirmed the Stat3 dependence of acute Rantes production by VSMCs. Together, these observations unify inflammatory events after vascular injury, demonstrating that VSMCs orchestrate the arterial inflammatory response program via acute Rantes production and subsequent inflammatory cell recruitment.

Resident vascular progenitor cells: an emerging role for non- terminally differentiated vessel-resident cells in vascular biology

Throughout development and adult life the vasculature exhibits a remarkably dynamic capacity for growth and repair. The vasculature also plays a pivotal role in the execution of other diverse biologic processes, such as the provisioning of early hematopoietic stem cells during embryonic development or the regulation of vascular tone and blood pressure. Adding to this importance, from an anatomical perspective, the vasculature is clearly an omnipresent organ, with few areas of the body that it does not penetrate. Given these impressive characteristics, it is perhaps to be expected that the vasculature should require, or at least be associated with, a ready supply of stem and progenitor cells. However, somewhat surprisingly, it is only now just beginning to be broadly appreciated that the vasculature plays host to a range of vessel-resident stem and progenitor cells. The possibility that these vessel-resident cells are implicated in processes as diverse as tumor vascularization and adaptive vascular remodeling appears likely, and several exciting avenues for clinical translation are already under investigation. This review explores the various stem and progenitor cell populations that are resident in the microvasculature, endothelium, and vessel walls and vessel-resident cells capable of phenotypic transformation.

Considerations for pre-clinical models and clinical trials of pluripotent stem cell-derived cardiomyocytes

Pluripotent stem cells (PSCs) represent an appealing source from which to develop cell replacement therapies. Different initiatives have been launched to promote their development toward clinical applications. This article will review the main questions that should be considered before translating PSC-derived cardiomyocytes into clinical investigations, including the development of good manufacturing practice-level PSC lines, the development of efficient protocols to generate pure populations of cardiac myocytes, and the development of techniques to improve the retention and survival rate of transplanted cells.

Cardiometabolic risk loci share downstream cis- and trans-gene regulation across tissues and diseases

Genetic variation and coronary artery disease Most genetic variants lie outside protein-coding genes, but their effects, especially in human health, are not well understood. Franzén et al. examined gene expression in tissues affected by coronary artery disease (CAD). They found that individuals with loci that have been associated with CAD in genome-wide analyses had different patterns of tissue-specific gene expression than individuals without these genetic variants. Similarly, tissues not associated with CAD did not have CAD-like expression patterns. Thus, tissue-specific data can be used to dissect the genetic effects that predispose individuals to CAD. Science, this issue p. 827 A gene expression survey in patients with coronary artery disease reveals how genetic variation affects the risk of heart failure. Genome-wide association studies (GWAS) have identified hundreds of cardiometabolic disease (CMD) risk loci. However, they contribute little to genetic variance, and most downstream gene-regulatory mechanisms are unknown. We genotyped and RNA-sequenced vascular and metabolic tissues from 600 coronary artery disease patients in the Stockholm-Tartu Atherosclerosis Reverse Networks Engineering Task study (STARNET). Gene expression traits associated with CMD risk single-nucleotide polymorphism (SNPs) identified by GWAS were more extensively found in STARNET than in tissue- and disease-unspecific gene-tissue expression studies, indicating sharing of downstream cis-/trans-gene regulation across tissues and CMDs. In contrast, the regulatory effects of other GWAS risk SNPs were tissue-specific; abdominal fat emerged as an important gene-regulatory site for blood lipids, such as for the low-density lipoprotein cholesterol and coronary artery disease risk gene PCSK9. STARNET provides insights into gene-regulatory mechanisms for CMD risk loci, facilitating their translation into opportunities for diagnosis, therapy, and prevention.