Abstract
Advances in lineage-tracking techniques have provided new insights into the origins and fates of smooth muscle cells (SMCs) in atherosclerosis. Yet new tools present new challenges for data ...interpretation that require careful consideration of the strengths and weaknesses of the methods employed. At the same time, discoveries in other fields have introduced new perspectives on longstanding questions about steps in atherogenesis that remain poorly understood. In this article, we address both the challenges and opportunities for a better understanding of the mechanisms by which cells appearing as or deriving from SMCs accumulate in atherosclerosis.
Progerin, an aberrant protein that accumulates with age, causes the rare genetic disease Hutchinson-Gilford progeria syndrome (HGPS). Patients who have HGPS exhibit ubiquitous progerin expression, ...accelerated aging and atherosclerosis, and die in their early teens, mainly of myocardial infarction or stroke. The mechanisms underlying progerin-induced atherosclerosis remain unexplored, in part, because of the lack of appropriate animal models.
We generated an atherosclerosis-prone model of HGPS by crossing apolipoprotein E-deficient (
) mice with
mice ubiquitously expressing progerin. To induce progerin expression specifically in macrophages or vascular smooth muscle cells (VSMCs), we crossed
mice with
and
mice, respectively. Progerin expression was evaluated by polymerase chain reaction and immunofluorescence. Cardiovascular alterations were determined by immunofluorescence and histology in male mice fed normal chow or a high-fat diet. In vivo low-density lipoprotein retention was assessed by intravenous injection of fluorescently labeled human low-density lipoprotein. Cardiac electric defects were evaluated by electrocardiography.
mice with ubiquitous progerin expression exhibited a premature aging phenotype that included failure to thrive and shortened survival. In addition, high-fat diet-fed
mice developed a severe vascular pathology, including medial VSMC loss and lipid retention, adventitial fibrosis, and accelerated atherosclerosis, thus resembling most aspects of cardiovascular disease observed in patients with HGPS. The same vascular alterations were also observed in
mice expressing progerin specifically in VSMCs, but not in
mice with macrophage-specific progerin expression. Moreover,
mice had a shortened lifespan despite the lack of any overt aging phenotype. Aortas of ubiquitously and VSMC-specific progerin-expressing mice exhibited increased retention of fluorescently labeled human low-density lipoprotein, and atheromata in both models showed vulnerable plaque features. Immunohistopathological examination indicated that
mice, unlike
mice, die of atherosclerosis-related causes.
We have generated the first mouse model of progerin-induced atherosclerosis acceleration, and demonstrate that restricting progerin expression to VSMCs is sufficient to accelerate atherosclerosis, trigger plaque vulnerability, and reduce lifespan. Our results identify progerin-induced VSMC death as a major factor triggering atherosclerosis and premature death in HGPS.
Circulating PCSK9 destines low-density lipoprotein receptor for degradation in lysosomes, resulting in increased LDL cholesterol. Accordingly, it is an attractive drug target for ...hypercholesterolemia, and results from clinical trials are promising. While the physiological role of PCSK9 in cholesterol metabolism is well described, its complex mechanism of action remains poorly understood, although it is known to depend on intracellular trafficking. We here identify sortilin, encoded by the hypercholesterolemia-risk gene SORT1, as a high-affinity sorting receptor for PCSK9. Sortilin colocalizes with PCSK9 in the trans-Golgi network and facilitates its secretion from primary hepatocytes. Accordingly, sortilin-deficient mice display decreased levels of circulating PCSK9, while sortilin overexpression in the liver confers increased plasma PCSK9. Furthermore, circulating PCSK9 and sortilin were positively correlated in a human cohort of healthy individuals, suggesting that sortilin is involved in PCSK9 secretion in humans. Taken together, our findings establish sortilin as a critical regulator of PCSK9 activity.
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•Sortilin is a PCSK9 sorting receptor•PCSK9 secretion from hepatocytes depends on sortilin•Sortilin knockout or overexpression affects plasma PCSK9 and hepatic LDLR levels•Circulating PCSK9 levels positively correlate with sortilin in a human cohort
PCSK9 targets the LDL receptor for degradation, resulting in increased LDL, and its inhibition looks clinically promising for hypercholesterolemia. Gustafsen et al. show that sortilin, a coronary artery disease risk factor, is a regulator of PCSK9 secretion. Circulating PCSK9 levels correlate with that of sortilin in humans.
Targeting Inflammation in Atherosclerosis Bentzon, Jacob F., MD, PhD
Journal of the American College of Cardiology,
12/2016, Letnik:
68, Številka:
25
Journal Article
Background Low plasma testosterone, either spontaneous or as a result of androgen deprivation therapy for prostate cancer, is associated with an increased risk of cardiovascular events. The ...underlying mechanism in humans is not understood. Experimental studies in mice have shown that castration facilitates atherogenesis and may increase signs of plaque vulnerability. Pigs used for translational atherosclerosis research have frequently been castrated for practical or commercial reasons, but the effect of castration on atherosclerosis has never been systematically evaluated in pigs. Objective To study the effect of castration on atherosclerotic plaque burden and type in genetically modified minipigs with hypercholesterolemia. Methods Newborn male Yucatan minipigs with transgenic overexpression of a human gain-of-function mutant of proprotein convertase subtilisin/kexin type 9 were randomized to undergo orchiectomy (n = 8) or serve as controls (n = 6). Minipigs were started on high-fat diet at 3 months of age and the amount and composition of atherosclerotic lesions were analyzed at 12 months of age. Plasma lipid profiles and behavioral parameters were also assessed. Results Plasma lipids were slightly affected to a more atherogenic profile by orchiectomy, but atherosclerotic lesion size was unaltered in the LAD, thoracic aorta, abdominal aorta, and iliac arteries. The distribution of lesion types (xanthomas, pathological intimal thickening and fibroatheromas) were also not statistically different between groups in any of the examined vascular territories. The abdominal aorta developed the most advanced stages of disease with reproducible fibroatheroma formation, and here it was found that the area of necrotic core was significantly increased in orchiectomized pigs compared with controls. Orchiectomy also reduced aggressive behavior. Conclusions Castration does not alter the burden of atherosclerosis in hypercholesterolemic Yucatan minipigs, but may increase necrotic core area in fibroatheromas.
To provide a comprehensive histopathological validation of cardiac magnetic resonance (CMR) and endocardial voltage mapping of acute and chronic atrial ablation injury.
16 pigs underwent pre-ablation ...T2-weighted (T2W) and late gadolinium enhancement (LGE) CMR and high-density voltage mapping of the right atrium (RA) and both were repeated after intercaval linear radiofrequency ablation. Eight pigs were sacrificed following the procedure for pathological examination. A further eight pigs were recovered for 8 weeks, before chronic CMR, repeat RA voltage mapping and pathological examination. Signal intensity (SI) thresholds from 0 to 15 SD above a reference SI were used to segment the RA in CMR images and segmentations compared with real lesion volumes. The SI thresholds that best approximated histological volumes were 2.3 SD for LGE post-ablation, 14.5 SD for T2W post-ablation and 3.3 SD for LGE chronically. T2-weighted chronically always underestimated lesion volume. Acute histology showed transmural injury with coagulative necrosis. Chronic histology showed transmural fibrous scar. The mean voltage at the centre of the ablation line was 3.3 mV pre-ablation, 0.6 mV immediately post-ablation, and 0.3 mV chronically.
This study presents the first histopathological validation of CMR and endocardial voltage mapping to define acute and chronic atrial ablation injury, including SI thresholds that best match histological lesion volumes. An understanding of these thresholds may allow a more informed assessment of the underlying atrial substrate immediately after ablation and before repeat catheter ablation for atrial arrhythmias.
Induction of atherosclerosis in mice with one or more genetic alterations (e.g., conditional deletion of a gene of interest) has traditionally required crossbreeding with Apoe or Ldlr deficient mice ...to achieve sufficient hypercholesterolemia. However, this procedure is time consuming and generates a surplus of mice with genotypes that are irrelevant for experiments. Several alternative methods exist that obviate the need to work in mice with germline-encoded hypercholesterolemia. In this chapter, we detail an efficient and increasingly used method to induce hypercholesterolemia in mice through adeno-associated virus-mediated transfer of the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene.
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