http://repub.eur.nl/res/aut/22886/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/34741/ 2012-01-01T00:00:00Z Detailed evaluation of coronary function early in diabetes mellitus (DM)-associated coronary artery disease (CAD) development is difficult in patients. Therefore, we investigated coronary conduit and small artery function in a preatherosclerotic DM porcine model with type 2 characteristics. Streptozotocin-induced DM pigs on a saturated fat/cholesterol (SFC) diet (SFC + DM) were compared with control pigs on SFC and standard (control) diets. SFC + DM pigs showed DM-associated metabolic alterations and early atherosclerosis development in the aorta. Endothelium-dependent vasodilation to bradykinin (BK), with or without blockade of nitric oxide (NO) synthase, endothelium-independent vasodilation to an exogenous NO-donor (S-nitroso-N-acetylpenicillamine), and vasoconstriction to endothelin (ET)-1 with blockade of receptor subtypes, were assessed in vitro. Small coronary arteries, but not conduit vessels, showed functional alterations including impaired BK-induced vasodilatation due to loss of NO (P < 0.01 vs. SFC and control) and reduced vasoconstriction to ET-1 (P < 0.01 vs. SFC and control), due to a decreased ETa receptor dominance. Other vasomotor responses were unaltered. In conclusion, this model demonstrates specific coronary microvascular alterations with regard to NO and ET-1 systems in the process of early atherosclerosis in DM. In particular, the altered ET-1 system correlated with hyperglycemia in atherogenic conditions, emphasizing the importance of this system in DM-associated CAD development. http://repub.eur.nl/res/pub/28732/ 2010-07-01T00:00:00Z Objectives The aim of this study was to compare the effects of single drug-eluting stents (DES) on porcine coronary function distal to the stent in vivo and in vitro. Background The mechanism of endothelial dysfunction occurring in human coronary conduit arteries up to 9 months after DES implantation is unknown. Methods A sirolimus-eluting stent (SES), paclitaxel-eluting stent (PES), and a bare-metal stent (BMS) were implanted in the 3 coronary arteries of 11 pigs. After 5 weeks, in vivo responses in distal coronary flow to different doses of bradykinin (BK) and nitrates were measured. In vitro, vasodilation to BK and nitrates, as well as vasoconstriction to endothelin (ET)-1 were assessed in both distal coronary conduit and small arteries. In addition, contributions of nitric oxide (NO) and endotheliumderived hyperpolarizing factors (EDHFs) and cyclic guanosine monophosphate (cGMP) responses to BK-stimulation were determined in vitro. Results Both DES did not alter in vivo distal vasomotion. In vitro distal conduit and small arterial responses to BK were also unaltered; DES did not alter the BK-induced increase in cGMP. However, after NO synthase blockade, PES showed a reduced BK-response in distal small arteries as compared with BMS and SES (p < 0.05). The ET-1-induced vasoconstriction and vascular smooth muscle cell function were unaltered. Conclusions In this study of single stenting in healthy porcine coronaries for 5 weeks, SES did not affect distal coronary vascular function, whereas PES altered distal endothelial function of small arteries under conditions of reduced NO bioavailability. Therefore, specifically the EDH-component of microvascular function seems affected by PES. http://repub.eur.nl/res/pub/24408/ 2009-04-01T00:00:00Z Objectives: The aim of this study was to compare efficacy of low- and high-dose sirolimus release (25, 40, or 100 μg) from hydroxyapatite (HAp) with Cypher (Cordis, Johnson & Johnson, Warren, New Jersey) (111 μg sirolimus) in porcine coronary arteries. Background: Polymer-based sirolimus-eluting stents such as Cypher interfere with vascular healing, probably due to the permanent presence of the polymer coating and the high sirolimus dose. The use of low-dose sirolimus and inert nonpolymeric but biodegradable coatings such as HAp might be more appropriate. Methods: Stents (n = 68) were implanted, guided by quantitative coronary angiography. All swine received clopidogrel and acetylsalicylic acid during 28 days follow-up. Safety of the coating in absence of drugs was studied by comparing HAp with and without a lipid-based release regulating layer (HApR) with bare-metal stents. Efficacy was studied by comparing the release of 25, 40, and 100 μg sirolimus with Cypher. Results: The safety study (without drug) revealed no differences in neointimal thickening in response to HAp and HApR with complete healing in all groups. Dose response analysis showed that neointimal thickening was similar in all groups regardless of sirolimus dose, with a normal appearance of the endothelium. There was, however, a dose-dependent increase in fibrinoid (p = 0.028), considered to be a marker of delayed healing. The Cypher stent induced the highest amount of fibrinoid. Conclusions: Reducing the dose of sirolimus eluting from a biocompatible HAp coated stent reduces signs of delayed vascular healing, without affecting neointimal hyperplasia. http://repub.eur.nl/res/pub/19331/ 2009-01-01T00:00:00Z Endothelial dysfunction has been implicated in the pathological process of coronary artery disease as well as an adverse event after coronary drug eluting stent (DES) implantation. In this review, an overview will be given of the evidence to date regarding the effects of coronary DES on endothelial function obtained from both clinical and experimental studies. Stenting in general and DES seem to impair several aspects of endothelial function: provision of a permeable barrier function; modulation of adhesion, thrombosis and inflammation; and regulation of vascular tone. However, new insights show that the effects of DES can extend beyond the stent and peri-stent area: the vascular bed distal to the stent, starting with the distal conduit vessels up to the distal microvasculature, might be at risk. In addition, insight into the mechanism of DES induced endothelial dysfunction has been gained. To finalize this review, clinical complications and solutions of DES associated endothelial dysfunction will be discussed. http://repub.eur.nl/res/pub/29635/ 2008-05-01T00:00:00Z Several studies have indicated an interaction between the renin-angiotensin (ANG II) system and endothelin (ET) in the regulation of vascular tone. Previously, we have shown that both ET and ANG II exert a vasoconstrictor influence on the coronary resistance vessels of awake normal swine. Here, we investigated whether the interaction between ANG II and ET exists in the control of coronary resistance vessel tone at rest and during exercise using single and combined blockade of angiotensin type 1 (AT1) and ETA/ETBreceptors. Since both circulating ANG II and ET levels are increased after myocardial infarction (MI), we investigated if the interaction between these systems is altered after MI. In awake healthy swine, coronary vasodilation in response to ETA/ETBreceptor blockade in the presence of AT1 blockade was similar to vasodilation produced by ETA/ETBblockade under control conditions. In awake swine with a 2- to 3-wk-old MI, coronary vasodilator responses to individual AT1and ETA/ETBreceptor blockade were virtually abolished, despite similar coronary arteriolar AT1and ETAreceptor expression compared with normal swine. Unexpectedly, in the presence of AT1blockade (which had no effect on circulating ET levels), ETA/ETBreceptor blockade elicited a coronary vasodilator response. These findings suggest that in normal healthy swine the two vasoconstrictor systems contribute to coronary resistance vessel control in a linear additive manner, i.e., with negligible cross-talk. In contrast, in the remodeled myocardium, cross-talk between ANG II and ET emerges, resulting in nonlinear redundant control of coronary resistance vessel tone. Copyright http://repub.eur.nl/res/pub/29104/ 2008-04-01T00:00:00Z Distal to a chronic coronary artery stenosis, structural remodeling of the microvasculature occurs. The microvascular functional changes distal to the stenosis have not been studied in detail. We tested the hypothesis that microvascular structural remodeling is accompanied by altered regulation of coronary vasomotor tone with increased responsiveness to endothelin-1. Vasomotor tone was studied in coronary microvessels from healthy control swine and from swine 3 to 4 months after implantation of an occluder that causes a progressive coronary narrowing, resulting in regional left ventricular dysfunction and blunted myocardial vasodilator reserve. Arterioles (≈200-μm passive inner diameter at 60 mm Hg) were isolated from regions perfused by the stenotic left anterior descending and normal left circumflex coronary arteries and studied in vitro. Passive pressure-diameter curves demonstrated reduced distensibility of subendocardial left anterior descending compared with subendocardial left circumflex or control arterioles, suggestive of structural remodeling. Myogenic responses were blunted in subendocardial left anterior descending compared with left circumflex arterioles, reflecting altered smooth muscle function. However, vasodilator responses to nitroprusside and bradykinin were not different in the endocardium, suggesting preserved endothelium and smooth muscle responsiveness. Finally, vasoconstrictor responses to endothelin-1 were enhanced in left anterior descending arterioles compared with left circumflex or control arterioles. Regional myocardial vascular conductance responses to bradykinin and endothelin in vivo confirmed the in vitro observations. In conclusion, inward remodeling of coronary microvessels distal to a stenosis is accompanied by exaggerated vasoconstrictor responses to endothelin-1. These structural and functional alterations may aggravate flow abnormalities distal to a chronic coronary artery stenosis.