Somatostatin receptors and the potential use of Sandostatin to interfere with vascular remodelling

Graft vessel disease (GVD) is a major cause of graft loss after the first year following transplantation. GVD is a complex, multifunctional process that involves immunological as well as non-immunological events such as ischaemia/reperfusion injury. An important target cell to interfere with the development of GVD is the smooth muscle cell (SMC). Somatostatin (SRIF) analogues have been shown previously to inhibit the proliferation of SMC in vitro and in vivo. We provide evidence that Sandostatin, an octapeptide SRIF analogue that is known to have anti-proliferative properties on SMC proliferation, inhibits vascular remodelling in a rat angioplasty model. Furthermore, in two allotransplantation models, Sandostatin effectively interferes with the development of signs of chronic rejection/GVD. The role of the different SRIF receptor subtypes in chronic graft rejection is currently under investigation.     

Apoptosis of vascular smooth muscle cells in vascular remodelling and atherosclerotic plaque rupture.

Apoptosis (programmed cell death) of vascular smooth muscle cells (VSMCs) has recently been identified as an important process in a variety of human vascular diseases, including atherosclerosis, arterial injury, and restenosis after angioplasty. VSMC apoptosis is regulated by interactions between the local cell-cell and cytokine environment within the arterial wall, and the expression of pro- and anti-apoptotic proteins by the cell, including death receptors, proto-oncogenes and tumour suppressor genes. This review summarises our current knowledge of the occurrence and mechanisms underlying VSMC apoptosis in atherosclerosis and arterial remodelling.     

Reactive oxygen species and vascular remodelling in hypertension: still alive

Reactive oxygen species (ROS) are reactive derivatives of O2 metabolism, including superoxide anion, hydrogen peroxide, hydroxyl radical and nitric oxide. All types of vascular cells produce ROS, primarily via cell membrane-associated NAD(P)H oxidase. Cardiovascular diseases, such as hypertension, are associated with increased ROS formation (oxidative stress). Oxidative excess in the vasculature reduces levels of the vasodilator nitric oxide, causes tissue injury, promotes protein oxidation and DNA damage, and induces proinflammatory responses. ROS are also important intracellular signalling molecules that regulate vascular function by modulating vascular cell contraction/dilation, migration, growth/apoptosis, and extracellular matrix protein turnover, which contribute to vascular remodelling. Interventions to decrease ROS bioavailability regress remodelling and reduce blood pressure in experimental hypertension. Such strategies may have therapeutic potential in cardiovascular diseases.     

Bone marrow-derived vascular cells in response to injury

Intimal hyperplasia is a key lesion for various vascular disorders such as atherosclerosis, postangioplasty restenosis and transplant arteriopathy. It has widely been accepted that intimal smooth muscle cells (SMC) originate from the medial layer in the same artery. However, recent studies suggest that bone marrow can also provide circulating progenitors for vascular SMC. Bone marrow-derived SMC participate in neointimal formation in animal models of allotransplantation, severe mechanical injury and hyperlipidemia-induced atherosclerosis. In human, transplantation arteriopathy also seems to involve circulating SMC, but their role in atherosclerosis and restenosis remains to be elucidated. Mobilization, differentiation and proliferation steps of SMC progenitors will provide promising targets for novel therapeutic approaches against proliferative vascular diseases.     

Confocal myography for the study of hypertensive vascular remodelling

Hypertension is associated with vascular structural alterations known as "vascular remodelling", which initially are adaptive but in the long run, lead to vascular damage and loss of function. Despite decades of study, there is still modest information on the 3-dimensional (3D) arrangement of vascular cells and extracellular matrix (ECM) and how they change under pathological situations. To address this problem we developed a technique which combines fluorescence confocal microscopy, pressure myography and image analysis, "confocal myography", which permits the study of intact resistance-sized vessels at cellular level and at physiological pressure. With the aid of this method, we have identified, in arteries from hypertensive rats, abnormal orientation of endothelial, smooth muscle cells (SMC) and elastic fibres; elongation and denudation of endothelial cells, and adventitial hypercellularity. Confocal myography offers a new approach to the study of vascular remodelling in intact small arteries from a 3D point of view.     

Region-specific patterns of vascular remodelling occur early in atherosclerosis and without loss of smooth muscle cell markers

BackgroundVascular remodelling is characterized by increased smooth muscle cell (SMC) proliferation and migration. Coincident with these events, SMC markers of differentiation are known to down-regulate in advanced stages of atherosclerosis, a process known as phenotypic modulation. However, it is not known when this first begins. Here we sought to determine if regions of the mouse aorta with varying susceptibilities for atherosclerosis display differential vascular remodelling and SMC gene expression at the earliest stages of disease.Methods and resultsLDLrKO mice were fed normal or high cholesterol diet for 0–98 days. In the latter, ORO and H&;E staining of arch, thoracic and abdominal aortic sections revealed infrequent occurrences of lipid deposition at d28, but significant region-specific vascular remodelling. Immunostaining for PCNA revealed increased cellular proliferation in the intima and inner media at d28 in all three regions. qRT-PCR of SMC revealed increased expression of SM22α and SM-MHC in the arch by d28, which subsequently decreased by d98. By contrast, eNOS gene expression was consistently decreased in the arch over these times. A temporal increase in macrophage-specific CD68 expression was observed in the arch but not thoracic or abdominal regions.ConclusionRemodelling of the vascular myocyte compartment due to cellular proliferation is an early event in atherosclerosis and is associated with increases in SMC-specific gene expression. These events precede subsequent lesion formation and SMC phenotypic modulation.     

c-Myc antisense oligonucleotides preserve smooth muscle differentiation and reduce negative remodelling following rat carotid arteriotomy

OBJECTIVES: The vascular biology of restenosis is complex and not fully understood, thus explaining the lack of effective therapy for its prevention in clinical settings. The role of c-Myc in arteriotomy-induced stenosis, smooth muscle cell (SMC) differentiation and apoptosis was investigated in rat carotids applying full phosphorothioate antisense (AS) oligonucleotides (ODNs). METHODS: Carotid arteries from WKY rats were submitted to arteriotomy and to local application of ODNs through pluronic gel. Apoptosis (deoxynucleotidyl transferase-mediated dUTP nick end-labelling), SMC differentiation (SM22 immunofluorescence) and vessel morphology and morphometry (image analysis) were determined 2, 5 and 30 days after injury, respectively. RESULTS: AS ODNs induced a 60% decrease of target c-Myc mRNA 4 h after surgery in comparison to control sense (S) and scrambled ODN-treated carotids (p < 0.05). A significant 37 and 50% decrease in SM22 protein in the media of S ODN-treated and untreated carotids was detected when compared to uninjured contralateral arteries (p < 0.05). This reduction in SM22 expression was prevented in AS ODN-treated carotids. Stenosis was mainly due to adventitial constrictive remodelling. Lumen area in AS ODN-treated carotids was 35% greater than in control arteries 30 days after surgery (p < 0.05). TUNEL assay revealed increased apoptosis in AS ODN-treated carotids (p < 0.05). CONCLUSIONS: c-Myc AS ODNs reduce arteriotomy-induced negative remodelling. This is accompanied by maintained SMC differentiation and greater apoptosis. The combination of reduced c-Myc-induced proliferation and increased apoptosis may thus underlie the less severe remodelling upon treatment with c-Myc mRNA AS ODN.     

Hypercholesterolemia impairs vascular remodelling after porcine coronary angioplasty

OBJECTIVE: To assess the effect of hypercholesterolemia on neointima formation and vascular remodelling after porcine coronary angioplasty. METHODS: Left anterior descending coronary angioplasty was carried out in five control and 16 age-matched hypercholesterolemic miniature pigs. Vascular remodelling was measured by intravascular ultrasound. Neointima size and composition were assessed by quantitative image analysis. Coronary smooth muscle cells (SMC) from control and diet pigs were collected 1 h after angioplasty for in vitro study of the effect of hypercholesterolemic serum on SMC migration and of macrophage-induced matrix degradation on SMC adhesion. RESULTS: Twenty-eight days after angioplasty, lumen increase was 0.08+/-1.7 mm(2) in diet and 2.7+/-2.7 mm(2) (P=0.016) in control pigs. Lumen increase correlated with vascular remodelling (IEL(post)/IEL(pre); R(2)=0.59; P<0.001) and with the circumferential gain relative to the neointima (R(2)=0.32; P<0.01) but not with neointimal area that was similar in control and diet pigs. Circumferential gain correlated with VSMC deposition at the site of the injury (R(2)=0.28; P<0.01) that correlated with organized collagen (R(2)=0.34; P<0.01). The VSMC and collagen content of neointima in diet pigs was lower whereas the macrophage content was higher. Hypercholesterolemic serum and oxidised LDL reduced migration of VSMC from diet pigs. Macrophage-induced degradation of VSMC extracellular matrix reduced VSMC adhesion (P=0.015). CONCLUSION: Hypercholesterolemia impairs vascular remodelling of balloon-treated coronary arteries. It decreases VSMC and collagen accumulation at the site of injury. Our in vitro data suggest that this decrease can be due to macrophage-induced matrix degradation and reduced VSMC adhesion and to impaired VSMC migration. Oxidised LDL mimics the inhibitory effect of hypercholesterolemic serum.     

Rapamycin reduces neointima formation during vascular injury

BACKGROUND: Proliferation and migration of vascular smooth muscle cells (SMCs) mark the key processes in the development of bypass graft disease and during neointima formation in restenosis after angioplasty. Growth factors are potent SMC mitogens as they are involved in SMC proliferation and in extracellular matrix (ECM) synthesis. Based on these premises, we examined the effect of the proliferation inhibitor rapamycin in human SMC culture and in a rabbit vascular injury model. MATERIALS AND METHODS: Injection of rapamycin or its vehicle was performed with an infusion-balloon catheter directly into the vessel wall during vascular injury. The intima/media ratio was determined histologically whereas the protein expression was analysed using the powerful two-dimensional gel electrophoresis (2D page) technique. Inhibition of proliferation after rapamycin application was estimated in a human SMC culture for time and dose dependent effects. RESULTS: Rapamycin treatment resulted in a significant reduction of intima media ratio compared to vehicle treated animals after three weeks (0.65 +/- 0.1 vs. 1.2 +/- 0.2 intima-media-ratio, p < 0.05). 2D electrophoresis analysis proved increased ECM synthesis following angioplasty (i.e., lamin, vimentin) in vehicle treated animals. Local rapamycin administration resulted in profound reduction of ECM synthesis after vascular injury. In in-vitro experiments exposure of cultured human SMCs to rapamycin resulted in a significant and dose-dependent (1 nm-100 nm) reduction of human smooth muscle cell proliferation measured by cell counting. CONCLUSION: These above mentioned results suggest that protein synthesis in addition to reduction of cellular proliferation plays an important role following vascular injury, since application of rapamycin resulted in the reduction of SMC proliferation and ECM-synthesis.     

microRNA调节血管钙化

在冠状动脉疾病的患者中血管钙化是非常普遍的,血管钙化与主要不良心血管事件发生有关,可增加心血管死亡风险。血管钙化的发病机制复杂,目前公认的是类似于骨骼的形成。血管平滑肌细胞(SMC)转分化为成骨样细胞、钙磷平衡的失调、破骨细胞活性和矿物质吸收能力的降低,在血管钙化过程中都扮演着不可或缺的角色。最近的研究发现,microRNA(miRNA)作为一个血管钙化的重要调控物,是通过引起SMC复杂的基因重组和其他相关细胞的功能反应而参与这个过程的。本文将详细介绍miRNA在血管钙化中的调节作用。     

Regulation of lysyl oxidase in vascular cells: lysyl oxidase as a new player in cardiovascular diseases

Lysyl oxidase (LOX) plays a crucial role in the maintenance of extracellular matrix stability and could participate in vascular remodelling associated with cardiovascular diseases. Evidence from in vitro and in vivo studies shows that LOX downregulation is associated with the endothelial dysfunction characteristic of earlier stages of the atherosclerotic process. Conversely, upregulation of this enzyme in vascular cells could induce neointimal thickening in atherosclerosis and restenosis. In fact, LOX is chemotactic for vascular smooth muscle cells and monocytes, is modulated by proliferative stimulus in these cells, and could control other cellular processes such as gene expression and cell transformation. Furthermore, it is conceivable that LOX downregulation could underlie plaque instability and contribute to the destructive remodelling that takes place during aneurysm development. Overall, LOX could play a key role in vascular homeostasis and, hence, it emerges as a new player in cardiovascular diseases. This review addresses the experimental evidence related to the role of LOX in vascular disorders and the potential benefits of controlling its expression and function.     

MicroRNAs在血管钙化中的作用

血管的钙化在冠心病患者是非常常见的,许多研究证实microRNAs(miRs)是血管钙化过程中一类重要的调节因子。人们对miRs的研究已取得一定进展,发现它可以通过调控平滑肌细胞的转分化、调节钙磷稳态、下调平滑肌细胞收缩表型等来引起血管钙化的发生。本文对miRs在血管钙化中所起的作用做一综述。     

Blood flow-dependent arterial remodelling is facilitated by inflammation but directed by vascular tone

AIMS: Altered blood flow affects vascular tone, attracts inflammatory cells, and leads to microvascular remodelling. We tested the hypothesis that inflammation facilitates the remodelling response, but that vascular tone determines its direction (inward or outward). METHODS AND RESULTS: Mouse mesenteric resistance arteries were ligated to create either increased blood flow or low blood flow in vivo. In vivo microscopy was used to determine changes in vascular tone. Structural remodelling was studied after 2 days, with or without macrophage depletion. In order to characterize the inflammatory response, immunostaining, confocal microscopy, and real-time PCR were used. To address the role of vascular tone in remodelling, arteries were treated with the vasodilator amlodipine during organ culture. Vessels exposed to high blood flow dilated, whereas low flow induced constriction. After 1 day, inflammatory markers showed a complex but remarkably similar increase in expression during high flow and low flow. Both high-flow and low-flow vessels showed an increase in the number of adventitial macrophages. Depletion of macrophages eliminated flow-induced remodelling. Manipulation of vascular tone reversed inward remodelling in response to low blood flow. CONCLUSION: Altered blood flow triggers an inflammatory response that facilitates remodelling. Vascular tone is a crucial determinant of the direction of the remodelling response.     

The role of perlecan in arterial injury and angiogenesis

Perlecan is a large heparan sulfate proteoglycan (HSPG), which is a major component of the vessel wall. In relation to vascular biology, perlecan has been shown to be a potent inhibitor of smooth muscle cell (SMC) activity. In vivo experiments in animal models of arterial injury have shown that perlecan may inhibit thrombosis and intimal hyperplasia. On the other hand, perlecan has been shown to have opposing effects on endothelial cells (ECs), where it promotes in vitro and in vivo angiogenesis and plays an important role in mediating tumor growth. These diverse biological effects, or "the perlecan paradox", are discussed in this review paper. The properties of perlecan including inhibition of SMC activity and thrombosis while enhancing EC proliferation are ideal for the prevention of in-stent restenosis. Perlecan's pro-angiogenic effects may be used for the treatment of various ischemic diseases such as intractable coronary artery disease and peripheral vascular disease.     

Allergen-induced airway remodelling.

Airway remodelling is associated with chronic asthma but it remains unclear whether it results from airway inflammation in response to allergens or immune-mediated events such as viral infections. Although the acute inflammation associated with asthma has been modelled extensively both in vitro and in vivo, the structural changes occurring in the lung have only recently been investigated. These in vitro, in vivo and in silico systems have been designed to examine the pathways leading to allergen-induced airway remodelling and have enabled investigators to draw conclusions about the participation of key cells and molecules in the development of allergen-induced airway remodelling. However, fundamental questions remain regarding the genesis of remodelling as well as the relationship between functional symptoms and pathological changes that occur. In this review the key questions relating allergen exposure to development of remodelling are discussed, as well as the steps that are being undertaken to investigate them.     

COPD and inflammation: statement from a French expert group: inflammation and remodelling mechanisms

The present study reviews the literature on inflammation and remodelling mechanisms in chronic obstructive pulmonary disease (COPD). The development of COPD is associated with chronic pulmonary inflammation. Immunity (innate or adaptive) plays a role in its onset and continuation. Airways inflammation alters bronchial structure/function relations: increased bronchial wall thickness, increased bronchial smooth muscle tone, seromucosal gland hypersecretion and loss of elastic structures. Circulating markers of pulmonary inflammation indicate its systemic dissemination. Oxidative stress plays a major role in the onset and persistence of tissue abnormalities. The determinants of extra- and intra-cellular redox control are only partially known. Susceptibility genes, antioxidant system insufficiency and reduced levels of anti-age molecules and of histone deacetylation are also involved. The molecular and cellular targets of inflammation and remodelling are numerous and complex. Currently, tools exist to limit inflammation in COPD but not to act on structural remodelling.