Elevated matrix metalloproteinase expression after stent implantation is associated with restenosis

Unveiling Dandy-Walker syndrome: A surprising twist in the tale of acute hydrocephalus and Down syndrome child

The correlation between Down syndrome and Dandy-Walker syndrome is an exceptionally uncommon occurrence. To date, only four cases have been documented. All previously reported cases involved individuals under the age of 37 months, with prenatal or birth diagnoses. Additionally, most of these cases displayed a limited life expectancy and experienced poor developmental outcomes. In this report, we present the first-ever instance of an 11-year-old male patient, previously undiagnosed with Dandy-Walker syndrome, who presented with acute intracranial hypertension. Magnetic Resonance Imaging revealed an active hydrocephalus caused by a Dandy-Walker malformation. The patient's condition was effectively managed through the implementation of a ventriculo-cysto-peritoneal shunt. This case highlights the coexistence of Dandy-Walker syndrome and Down syndrome in an asymptomatic young patient. Furthermore, it demonstrates that active hydrocephalus in such cases can be successfully addressed through either endoscopic third ventriculostomy or ventriculo-cysto-peritoneal shunt procedures.

The role of inflammation in percutaneous coronary intervention, from balloon angioplasty to drug eluting stents

The role of inflammation in percutaneous coronary intervention (PCI) has been investigated in numerous studies. Both pre-PCI and post-PCI inflammatory status have been demonstrated to be linked with patient outcomes. C-reactive protein continues to be the most studied inflammatory biomarker, while a growing number of additional biomarkers, including cytokines and immune cells, are being assessed. As insights are gained into the complexities of the inflammatory response to PCI, it becomes evident that a targeted approach is necessary to ensure optimal patient outcomes. Here, we review the biomarkers that can predict patient outcomes following PCI and specifically how they differ for balloon angioplasty, bare metal stents and drug eluting stents. A specific focus is given to human studies and periprocedural inflammation rather than inflammation associated with myocardial infarction.

Incidence, risk factors, and clinical sequelae of incomplete stent apposition after sirolimus-eluting stent

Incomplete stent apposition has been documented after sirolimus-eluting stent implantation. However, its clinical sequelae remain controversial. To identify the incidence and its clinical consequences of ISA, IVUS was performed on 78 patients. In spite of well apposition immediately after the deployment, late stent malapposition occurred after 6-months follow-up. A total of 7 patients who received SES showed ISA. There were no significant differences in IVUS measurements between patients with or without ISA. However, there was an increase in external elastic membrane area in ISA group than non-ISA group (19.69 ± 3.50 vs. 15.05 ± 2.56 mm2, P<0.05). There were positive clinical events for ISA cases at 6-months clinical follow-up. Univariate and multivariable analyses indicated that hs-CRP, miR-21, and MMP-2 were risk factor for ISA. ISA was observed in 9% of patients after SES implantation, which was related to vessel positive remodeling. The incidence of MACEs in patients with ISA was higher than those without ISA. However, careful long-term follow-up remains to be clarified.

Multilevel Assessment of Stent-Induced Inflammation in the Adjacent Vascular Tissue

A recent U.S. Food and Drug Administration report presented the currently available scientific information related to biological response to metal implants. In this work, a multilevel approach was employed to assess the implant-induced and biocorrosion-related inflammation in the adjacent vascular tissue using a mouse stent implantation model. The implications of biocorrosion on peri-implant tissue were assessed at the macroscopic level via in vivo imaging and histomorphology. Elevated matrix metalloproteinase activity, colocalized with the site of implantation, and histological staining indicated that stent surface condition and implantation time affect the inflammatory response and subsequent formation and extent of neointima. Hematological measurements also demonstrated that accumulated metal particle contamination in blood samples from corroded-stetted mice causes a stronger immune response. At the cellular level, the stent-induced alterations in the nanostructure, cytoskeleton, and mechanical properties of circulating lymphocytes were investigated. It was found that cells from corroded-stented samples exhibited higher stiffness, in terms of Young's modulus values, compared to noncorroded and sham-stented samples. Nanomechanical modifications were also accompanied by cellular remodeling, through alterations in cell morphology and stress (F-actin) fiber characteristics. Our analysis indicates that surface wear and elevated metal particle contamination, prompted by corroded stents, may contribute to the inflammatory response and the multifactorial process of in-stent restenosis. The results also suggest that circulating lymphocytes could be a novel nanomechanical biomarker for peri-implant tissue inflammation and possibly the early stage of in-stent restenosis. Large-scale studies are warranted to further investigate these findings.

Release of MMP-2 in the circulation of patients with acute coronary syndromes undergoing percutaneous coronary intervention: Role of platelets

INTRODUCTION

Matrix metalloproteinases (MMPs) of atherosclerotic tissue contribute to plaque rupture triggering acute coronary syndromes (ACS). Several MMPs, including MMP-2, are also contained in platelets and released upon activation. An increase in circulating levels of MMP-2 has been reported in patients undergoing percutaneous coronary interventions (PCI), but its time-course and origin remain unclear. Aims of our study were to assess the time-course of MMP-2 release in blood of stable and unstable coronary artery disease patients undergoing PCI and to unravel the possible contribution of platelets to its release.

METHODS

Peripheral blood samples were drawn immediately before, 4 and 24 h after PCI from patients with ACS (NSTEMI or STEMI, n = 21) or with stable angina (SA, n = 21). Platelet-poor plasma and washed platelet lysates were prepared and stored for subsequent assay of MMP-2 and β-thromboglobulin (β-TG), a platelet-specific protein released upon activation.

RESULTS

Plasma MMP-2 and β-TG increased significantly 4 h after PCI and returned to baseline at 24 h in ACS patients, while they did not change in SA patients. Platelet content of MMP-2 and β-TG decreased significantly 4 h after PCI in patients with ACS, compatible with intravascular platelet activation and release, while they did not change in patients with SA.

CONCLUSIONS

PCI triggers the release of MMP-2 in the circulation of ACS patients but not in that of patients with SA. Platelets activated by PCI contribute to the increase of plasma MMP-2 releasing their MMP-2 content. Given that previous mechanicistic studies have shown that MMP-2 may sustain platelet activation and unstabilize downstream-located plaques and in the long term favour restenosis and atherosclerosis progression, these data may encourage the search for therapeutic agents blocking MMP-2 release or activity in ACS.

Numerical Analysis for Non-Uniformity of Balloon-Expandable Stent Deployment Driven by Dogboning and Foreshortening

PURPOSE

Stenting is the most common intervention for arteriosclerosis treatment; however, the success of the treatment depends on the incidence of in-stent restenosis (ISR). Stent deployment characteristics are major influencers of ISR and can be measured in terms of dogboning, asymmetry, and foreshortening. This study aimed to analyse the implications of balloon and stent-catheter assembly parameters on the stent deployment characteristics.

METHODS

Experimental approach to analyse the impact of the balloon and stent-catheter assembly parameters on stent deployment characteristics is a time-consuming and complex task, whereas numerical methods prove to be quick, efficient, and reliable. In this study, eleven finite element models were employed to analyse non-uniform balloon stent expansion pattern, comprised of variation in, stent axial position on balloon, balloon length, balloon folding pattern, and balloon wall thickness.

RESULTS

Obtained results suggest that the axially noncentral position of the stent on balloon and variable balloon thickness lead to non-uniform stent deployment pattern. Also, it was proved that variation in balloon length and balloon folding pattern influence deployment process.

CONCLUSION

Improved positional accuracies, uniform balloon wall thickness, and selection of the appropriate length of a balloon for selected stent configuration will help to minimize dogboning, asymmetry, and foreshortening during non-uniform stent expansion, thereby reducing the risk of restenosis. The stated numerical approach will be helpful to optimize stent catheter assembly parameters thus minimizing in-vitro tests and product development time.

The role of extracellular vesicles in neointima formation post vascular injury

Pathological neointimal growth can develop in patients as a result of vascular injury following percutaneous coronary intervention and coronary artery bypass grafting using autologous saphenous vein, leading to arterial or vein graft occlusion. Neointima formation driven by intimal hyperplasia occurs as a result of a complex interplay between molecular and cellular processes involving different cell types including endothelial cells, vascular smooth muscle cells and various inflammatory cells. Therefore, understanding the intercellular communication mechanisms underlying this process remains of fundamental importance in order to develop therapeutic strategies to preserve endothelial integrity and vascular health post coronary interventions. Extracellular vesicles (EVs), including microvesicles and exosomes, are membrane-bound particles secreted by cells which mediate intercellular signalling in physiological and pathophysiological states, however their role in neointima formation is not fully understood. The purification and characterization techniques currently used in the field are associated with many limitations which significantly hinder the ability to comprehensively study the role of specific EV types and make direct functional comparisons between EV subpopulations. In this review, the current knowledge focusing on EV signalling in neointima formation post vascular injury is discussed.

Preventing treatment failures in coronary artery disease: what can we learn from the biology of in-stent restenosis, vein graft failure, and internal thoracic arteries?

Coronary artery disease (CAD) remains one of the most important causes of morbidity and mortality worldwide, and the availability of percutaneous or surgical revascularization procedures significantly improves survival. However, both strategies are daunted by complications which limit long-term effectiveness. In-stent restenosis (ISR) is a major drawback for intracoronary stenting, while graft failure is the limiting factor for coronary artery bypass graft surgery (CABG), especially using veins. Conversely, internal thoracic artery (ITA) is known to maintain long-term patency in CABG. Understanding the biology and pathophysiology of ISR and vein graft failure (VGF) and mechanisms behind ITA resistance to failure is crucial to combat these complications in CAD treatment. This review intends to provide an overview of the biological mechanisms underlying stent and VGF and of the potential therapeutic strategy to prevent these complications. Interestingly, despite being different modalities of revascularization, mechanisms of failure of stent and saphenous vein grafts are very similar from the biological standpoint.

Vitronectin and Urokinase-Type Plasminogen Activator Gene Expression Levels Are Increased in Patients with Coronary Artery In-Stent Restenosis

Neointimal hyperplasia is known as a main factor contributing to in-stent restenosis (ISR). Monocytes may play a central role in vessel restenosis process after stent implantation. The aim of this study was to investigate the relationships between the urokinase-type plasminogen activator (PLAU) and vitronectin (Vtn) gene expression levels in peripheral blood mononuclear cell samples isolated from whole blood of 66 patients undergoing coronary artery angiography (22 controls, stenosis < 0.05%; 22 with stent no-restenosis and stenosis < 70%; and 22 with ISR and stenosis > 70%). The Vtn and PLAU gene expression levels were measured by real-time quantitative polymerase chain reaction technique. The age- and gender-independent increases in the expression levels of Vtn (17-fold; p  < 0.001) and PLAU (27-fold; p  < 0.0001) genes were found in the patients with ISR as compared with the control group. The results suggested that the Vtn and PLAU genes may be involved in the coronary artery ISR.

Increased levels of MMP-3, MMP-9 and MPO represent predictors of in-stent restenosis, while increased levels of ADMA, LCAT, ApoE and ApoD predict bare metal stent patency

AIMS

We sought to identify biochemical predictors that indicate susceptibility to in-stent restenosis (ISR) after coronary artery bare-metal stenting.

METHODS

A total of 111 consecutive patients with post-percutaneous coronary intervention (PCI) in-stent restenosis of a target lesion within 12 months were matched for age, sex, vessel diameter, and diabetes with 111 controls without post-PCI ISR. Plasma or serum levels of biochemical markers were measured: matrix metalloproteinases (MMP) 2, 3, 9; myeloperoxidase (MPO); asymmetric dimethylarginine (ADMA); lipoprotein (a) (Lp[a]); apolipoproteins E and D (ApoE and D); and lecitin-cholesterol acyltransferase (LCAT). Multivariable logistic regression association tests were performed.

RESULTS

Increased plasma MMP-3 (OR: 1.013; 95% CI: 1.004-1.023; P = 0.005), MMP-9 (OR: 1.014; 95% CI: 1.008-1.020; P < 0.0001) or MPO (OR: 1,003; 95% CI: 1.001-1.005; P = 0.002) was significantly associated with increased risk of ISR. Increased levels of ADMA (OR: 0.212; 95% CI: 0.054-0.827; P = 0.026), ApoE (OR: 0.924; 95% CI: 0.899-0.951; P < 0.0001), ApoD (OR: 0.919; 95% CI: 0.880-0.959; P = 0.0001), or LCAT (OR: 0.927; 95% CI: 0.902-0.952; P < 0.0001) was associated with risk reduction. No correlation was found between plasma MMP-2 or Lp (a) and ISR risk.

CONCLUSIONS

Increased levels of MMP-3, MMP-9, and MPO represent predictors of ISR after bare-metal stent implantation. In contrast, increased ADMA, LCAT, and Apo E and D indicate a decreased in-stent restenosis occurrence.

Mmp-9 expression after metallic stent placement in patients with colorectal cancer: association with in-stent restenosis

PURPOSE

To verify the expression of matrix metalloproteinase (MMP)-9 in stent-induced hyperplastic tissue from patients with colorectal cancer who received colorectal stents as a bridge to surgery.

MATERIALS AND METHODS

This prospective study was institutional review board-approved, and informed consent was obtained from all patients. Eleven patients (nine men, two women; mean age, 67 years; age range, 53-82 years) with malignant colorectal obstructions who received a colorectal stent between May and December 2010 were included. Tissue specimens were analyzed for MMP-9 and MMP-2 expression. After resection, the tissue was segmented into three parts: tumor tissue, stent-induced tissue hyperplasia, and normal colon tissue. MMP-9 and MMP-2 expression were determined by using zymography, Western blot analysis, and real-time reverse-transcription (qRT) polymerase chain reaction (PCR). Significance of differences between groups was evaluated with Friedman analysis of variance test. Signed-rank test was used to determine differences between malignant tumor tissue and stent-induced hyperplastic tissue groups.

RESULTS

Stent placement was technically successful in all 11 patients. Stent-induced hyperplastic tissues were found in all patients. Zymography (P = .003) and Western blot analysis (P = .008) showed that expression of MMP-9 was higher in malignant tumor tissue and stent-induced hyperplastic tissue groups compared with normal colorectal tissue group, demonstrating significant differences between groups but no significant differences between malignant tumor and stent-induced hyperplastic tissues. As for results of qRT PCR analysis, the stent-induced hyperplastic tissue group showed increases in messenger RNA expression level of MMP-9 compared with the malignant tumor tissue group (50.42-fold ± 66.30 higher).

CONCLUSION

High expression of MMP-9 is closely associated with stent-induced colorectal tissue hyperplasia in patients with colorectal cancer.

Matrix metalloproteinases: inflammatory regulators of cell behaviors in vascular formation and remodeling

Abnormal angiogenesis and vascular remodeling contribute to pathogenesis of a number of disorders such as tumor, arthritis, atherosclerosis, restenosis, hypertension, and neurodegeneration. During angiogenesis and vascular remodeling, behaviors of stem/progenitor cells, endothelial cells (ECs), and vascular smooth muscle cells (VSMCs) and its interaction with extracellular matrix (ECM) play a critical role in the processes. Matrix metalloproteinases (MMPs), well-known inflammatory mediators are a family of zinc-dependent proteolytic enzymes that degrade various components of ECM and non-ECM molecules mediating tissue remodeling in both physiological and pathological processes. MMPs including MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-12, and MT1-MMP, are stimulated and activated by various stimuli in vascular tissues. Once activated, MMPs degrade ECM proteins or other related signal molecules to promote recruitment of stem/progenitor cells and facilitate migration and invasion of ECs and VSMCs. Moreover, vascular cell proliferation and apoptosis can also be regulated by MMPs via proteolytically cleaving and modulating bioactive molecules and relevant signaling pathways. Regarding the importance of vascular cells in abnormal angiogenesis and vascular remodeling, regulation of vascular cell behaviors through modulating expression and activation of MMPs shows therapeutic potential.

Intra-individual changes of active matrix metalloproteinase-9 are associated with clinical in-stent restenosis of bare metal stents

OBJECTIVES

Increased chronic postprocedural levels of active matrix metalloproteinase-9 (MMP-9) have been associated retrospectively with a history of in-stent restenosis (ISR). This study aimed to determine whether index or post-percutaneous coronary intervention (PCI) plasma levels of active MMP-9 are a predictor of subsequent clinical ISR, in a standard population of patients treated with bare metal coronary stents.

METHODS

Four hundred thirty-two patients were prospectively recruited and sampled at index and 3 and 6 months after PCI. Those who developed symptomatic angiographically confirmed ISR were compared to randomly selected, asymptomatic controls, stratified by index presentation in a nested case-control design. Plasma samples were analyzed for the active form of MMP-9.

RESULTS

In all, 35 patients (8.1%) developed ISR, and these were compared to 98 controls. The increase in active MMP-9 over 3 months was significantly greater in the ISR group (p = 0.030) and independent of the established risk factors. Index clinical presentation was not associated with acute changes in active MMP-9; however, patients with ST-elevation myocardial infarction had greater increases in active MMP-9 at 3 months.

CONCLUSIONS

The change in active MMP-9 over 3 months after bare metal coronary stent placement appears to be independently associated with the development of ISR in a standard PCI population.

Matrix metalloproteinases

Remodeling of extracellular matrix is crucial for many physiological (cell migration, proliferation, growth, and development) and pathological (remodeling of heart, carcinogenesis, metastasis, etc.) events. Thus, the interaction between cells and extracellular matrix plays a key role in normal development and differentiation of organism and many pathological states as well. Changes in extracellular matrix are regulated by a system of proteolytic enzymes that are responsible for proteolysis of huge quantity of extracellular matrix components. Matrix metalloproteinases (MMPs) represent the main group of regulating proteases in ECM. Ability of matrix metalloproteinases to modify the structural integrity of tissues is essential for certain aspects of normal physiology and pathology. The ability to process molecules such as growth factors, receptors, adhesion molecules, other proteinases, and proteinase inhibitors makes MMPs potent controllers of physiological and pathological events in the cell microenvironment. Overactivation of MMPs has been implicated in numerous disease states.

Restenosis after PCI. Part 1: pathophysiology and risk factors

Restenosis is a complex disease for which the pathophysiological mechanisms have not yet been fully elucidated, but are thought to include inflammation, proliferation, and matrix remodeling. Over the years, many predictive clinical, biological, (epi)genetic, lesion-related, and procedural risk factors for restenosis have been identified. These factors are not only useful in risk stratification of patients, they also contribute to our understanding of this condition. Furthermore, these factors provide evidence on which to base treatment tailored to the individual and aid in the development of novel therapeutic modalities. In this Review, we will evaluate the available evidence on the pathophysiological mechanisms of restenosis and provide an overview of the various risk factors, together with the possible clinical application of this knowledge.

The evolving role of inflammatory biomarkers in risk assessment after stent implantation

The main adverse reactions to coronary stents are in-stent restenosis (ISR) and stent thrombosis. Along with procedural factors, individual susceptibility to these events plays an important role. In particular, inflammatory status, as assessed by C-reactive protein levels, predicts the risk of ISR after bare-metal stent implantation, although it does not predict the risk of stent thrombosis. Conversely, C-reactive protein levels fail to predict the risk of ISR after drug-eluting stent (DES) implantation, although they appear to predict the risk of stent thrombosis. Of note, DES have abated ISR rates occurring in the classical 1-year window, but new concern is emerging regarding late restenosis and thrombosis. The pathogenesis of these late events seems to be related to delayed healing and allergic reactions to polymers, a process in which eosinophils seem to play an important role by enhancing restenosis and thrombosis. The identification of high-risk individuals based on biomarker assessment may be important for the management of patients receiving stent implantation. In this report, we review the evolving role of inflammatory biomarkers in predicting the risk of ISR and stent thrombosis.

Activation of matrix metalloproteinase-9 is associated with mobilization of bone marrow-derived cells after coronary stent implantation

BACKGROUND

After stent-related vascular injury, an inflammatory response triggers the mobilization of bone marrow-derived stem cells, including both endothelial and smooth muscle progenitors, leading to re-endothelialization as well as restenosis. It has been postulated that neutrophil-released matrix metalloproteinase-9 (MMP-9) induces stem cell mobilization.

AIM

To elucidate the mechanistic link between inflammation and stem cell mobilization after coronary stenting.

METHODS

In 31 patients undergoing coronary stenting, we serially measured activated Mac-1 on the surface of neutrophils and active MMP-9 levels in the coronary sinus blood plasma, and the number of circulating CD34-positive cells in the peripheral blood.

RESULTS

After bare-metal stent implantation (n=21), significant increases in the numbers of CD34-positive cells (maximum on post-procedure day 7, P<0.001), activated Mac-1 (at 48 h, P<0.001), and active MMP-9 levels (at 24h, P<0.001) were observed. However, these changes were absent after sirolimus-eluting stent implantation (n=10). In overall patients, the numbers of CD34-positive cells on day 7 (R=0.58, P<0.01) and activated Mac-1 at 48 h (R=0.58, P<0.01) were both correlated with active MMP-9 levels at 24h. Stimulation of activated Mac-1 on the surface of isolated human neutrophils produced active MMP-9 release in vitro.

CONCLUSIONS

These results suggest that stent-induced activation of Mac-1 on the surface of neutrophils might trigger their MMP-9 release, possibly leading to the mobilization of bone marrow-derived stem cells. These reactions were substantially inhibited by sirolimus-eluting stents.

Increased restenosis rate after implantation of drug-eluting stents in patients with elevated serum activity of matrix metalloproteinase-2 and -9

OBJECTIVES

Our aim was to test whether serum levels of matrix metalloproteinase (MMP)-2 and -9 are associated with the development of in-stent restenosis (ISR) after implantation of drug-eluting stents (DES).

BACKGROUND

With the introduction of DES coronary ISR could be reduced dramatically. However, it still plays a significant role, particularly after treatment of multiple, complex lesions.

METHODS

We studied 85 patients who were treated with 159 DES. Blood samples for measurement of MMP-2 and -9 antigen and activity were taken directly before and 24 h after percutaneous coronary intervention (PCI). Restenosis was evaluated at 6 to 8 months by coronary angiography.

RESULTS

During the follow-up period, 2 patients (2.4%) died of cardiovascular causes, and 12 patients developed angiographic ISR. Patients with ISR showed significantly higher serum activity of MMP-9 at baseline (p = 0.017) and of MMP-2 (p < 0.0001) and MMP-9 (p < 0.0001) after the procedure. The PCI increased serum activity of MMP-2 (p = 0.005) and MMP-9 (p = 0.008) only in patients with ISR. The restenosis rates of patients in the highest quartile of MMP-2 after and MMP-9 before and after PCI were 40.0%, 38.9%, and 42.9% compared with 6.3%, 7.7%, and 4.0% in the lower quartiles, respectively. This was independent of clinical and procedural characteristics.

CONCLUSIONS

Elevated serum activities of MMP-2 and -9 are associated with dramatically increased restenosis rates after PCI with implantation of DES. Determination of MMP levels might be useful for identification of patients who are at high risk for ISR despite implantation of DES.

Emerging drugs for coronary restenosis: the role of systemic oral agents the in stent era

Introduction of drug eluting stents (DES) during percutaneous coronary interventions significantly reduces the rate of angiographic restenosis, target lesion and vessel revascularization. In spite of these benefits, other clinical hard end points such as death or myocardial infarction were not reduced and, furthermore, new concerns associated with the presence of late and very late stent thrombosis have been raised. The requirement of long-term dual antiplatelet therapy is another limitation associated with DES. Conversely, in this decade, other options to DES have been simultaneously discussed in observational and randomized studies. Several registries and randomized trials using the systemic approach with anti-inflammatory, immunosuppressive or antiplatelet therapies have been identified and discussed in this manuscript. In spite of all randomized studies with oral therapies in the bare metal stent (BMS) era demonstrating positive reductions in coronary restenosis, this practice has not been introduced clinically. Furthermore, a recent randomized trial comparing oral sirolimus plus BMS versus DES demonstrated that the first approach was cost saving and of comparable efficacy to DES. Conclusive evidence of high incidence of late and very late stent thrombosis with DES, together with clinical limitations for its widespread use, has opened up a large opportunity to search for alternative therapies in coronary restenosis prevention.

Human lung parenchyma but not proximal bronchi produces fibroblasts with enhanced TGF-beta signaling and alpha-SMA expression

Given the contribution various fibroblast subsets make to wound healing and tissue remodeling, the concept of lung fibroblast heterogeneity is of great interest. However, the mechanisms contributing to this heterogeneity are unknown. To this aim, we compared molecular and biophysical characteristics of fibroblasts concurrently isolated from normal human proximal bronchi (B-FBR) and distal lung parenchyma (P-FBR). Using quantitative RT-PCR, spontaneous expression of more than 30 genes related to repair and remodeling was analyzed. All P-FBR lines demonstrated significantly increased basal α-smooth muscle actin (α-SMA) mRNA and protein expression levels when compared with donor-matched B-FBR. These differences were not associated with sex, age, or disease history of lung tissue donors. In contrast to B-FBR, P-FBR displayed enhanced transforming growth factor (TGF)-β/Smad signaling at baseline, and inhibition of either ALK-5 or neutralization of endogenously produced and activated TGF-β substantially decreased basal α-SMA protein in P-FBR. Both B-FBR and P-FBR up-regulated α-SMA after stimulation with TGF-β1, and basal expression levels of TGF-β1, TGF-βRI, and TGF-βRII were not significantly different between fibroblast pairs. Blockade of metalloproteinase-dependent activation of endogenous TGF-β did not significantly modify α-SMA expression in P-FBR. However, resistance to mechanical tension of these cells was significantly higher in comparison with B-FBR, and added TGF-β1 significantly increased stiffness of both cell monolayers. Our data suggest that in contrast with human normal bronchial tissue explants, lung parenchyma produces mesenchymal cells with a myofibroblastic phenotype by intrinsic mechanisms of TGF-β activation in feed-forward manner. These results also offer a new insight into mechanisms of human fibroblast heterogeneity and their function in the airway and lung tissue repair and remodeling.

A novel mouse model of in-stent restenosis

BACKGROUND AND AIMS

In-stent restenosis (ISR) is the major complication that occurs after percutaneous coronary interventions to facilitate coronary revascularization. Herein we described a simple and cost-effective model, which reproduces important features of ISR in the mouse.

METHODS AND RESULTS

Microvascular bare metal stents were successfully implanted in the abdominal aorta of atherosclerotic ApoE-null mice. Patency of implanted stents was interrogated using ultrasound biomicroscopy. Aortas were harvested at different time points after implantation and processed for histopathological analysis. Thrombus formation was histologically detected after 1 day. Leukocyte adherence and infiltration were evident after 7 days and decreased thereafter. Neointimal formation, neointimal thickness and luminal stenosis simultaneously increased up to 28 days after stent implantation. Using multichannel fluorescence molecular tomography (FMT) for spatiotemporal resolution of MMP activities, we observed that MMP activity in the stented aorta of Apo-E null mice was 2-fold higher than that of wild-type mice. Finally, we compared neointimal formation in response to stenting in two genetically different mouse strains. In-stent neointimas in FVB/NJ mice were 2-fold thicker than in C57BL/6J mice (p=0.002).

CONCLUSION

We have developed a model that can take advantage of the multiple genetic resources available for the mouse to study the mechanisms of in-stent restenosis.

Active matrix metalloproteinases 3 and 9 are independently associated with coronary artery in-stent restenosis

OBJECTIVE

This study aimed to determine whether plasma levels of active matrix metalloproteinases (MMP) are predictors of in-stent restenosis (ISR) in New Zealand patients treated with bare-metal coronary stents.

METHODS

A group of 152 patients with a history of ISR were compared with 151 symptom free 1-year post-stenting patients (non-ISR). Demographic and angiographic characteristics were collected. Plasma samples were analyzed for the active forms of MMP-1, -2, -3 and -9 as well as tissue inhibitor of metalloproteinases (TIMP-1) using ELISA-based isoform sensitive assays.

RESULTS

Both active MMP-9 and active MMP-3 were independently associated with history of ISR. Elevated levels of both active MMP-3 and -9 had an adjusted odds ratio of 11.8 (95% CI: 4-35, p<0.0001) for association with ISR, with 37% of ISR patients having such levels versus 11% on non-ISR. The addition of both of the MMP biomarkers significantly increased the area under the curve (AUC) of a receiver operator characteristic (ROC) analysis incorporating the significant demographic and angiographic variables (AUC 0.85 versus 0.78, p<0.005).

CONCLUSION

Measures of plasma active MMP isoforms appear to be independently associated with ISR, and assessment of multiple MMP markers yields cumulative utility.

Lack of widespread inflammation after contemporary PCI

BACKGROUND

The inflammatory response to percutaneous coronary intervention (PCI) contributes to restenosis. However, it is not known if advances in PCI have attenuated this response. This study sought to determine the prevalence of systemic inflammation immediately after contemporary PCI, and to identify the predictors of the acute proinflammatory response to PCI.

METHODS

Twenty seven consecutive eligible patients undergoing uncomplicated single lesion PCI were recruited. Clinical and procedural characteristics were collected. Neutrophil Mac-1 and plasma matrix metalloproteinase-9 (MMP-9) levels were measured by flow cytometry and ELISA.

RESULTS

Overall, neutrophils were de-activated post-procedure [median (IQR) Mac-1: 329(277-555) versus 423 (273-533) MFI, p=0.011] but MMP-9 was unchanged [2.6 (1.8-5.1) versus 2.0 (1.5-3.8) ng/ml, p=ns]. There was a heterogeneous inflammatory response: Neutrophils were activated in 6 (22%) patients, whilst plasma MMP-9 rose in 10 (37%) patients. Twelve (44%) patients had either neutrophil activation or increased MMP-9 level post-procedure. There was no relationship between these two biomarkers. Lesion length predicted both neutrophil activation (OR, 95%CI: 19.0, 2.0-178.0, p=0.010) and increased MMP-9 (16.0, 1.5-17.2, p=0.022), and lesion complexity predicted the latter (9.6, 1.5-62.2, p=0.018). Presentation with an acute coronary syndrome, diabetes mellitus, receipt of drug-eluting stent, and stent diameter were not associated with an acute inflammatory response to PCI.

CONCLUSIONS

In contrast to the balloon angioplasty era, widespread inflammation is absent in most patients after contemporary PCI. Lesion length and complexity predicted an inflammatory reaction, suggesting it to be primarily a response to vascular injury.

The application of multiscale modelling to the process of development and prevention of stenosis in a stented coronary artery

The inherent complexity of biomedical systems is well recognized; they are multiscale, multiscience systems, bridging a wide range of temporal and spatial scales. While the importance of multiscale modelling in this context is increasingly recognized, there is little underpinning literature on the methodology and generic description of the process. The COAST (complex autonoma simulation technique) project aims to address this by developing a multiscale, multiscience framework, coined complex autonoma (CxA), based on a hierarchical aggregation of coupled cellular automata (CA) and agent-based models (ABMs). The key tenet of COAST is that a multiscale system can be decomposed into N single-scale CA or ABMs that mutually interact across the scales. Decomposition is facilitated by building a scale separation map on which each single-scale system is represented according to its spatial and temporal characteristics. Processes having well-separated scales are thus easily identified as the components of the multiscale model. This paper focuses on methodology, introduces the concept of the CxA and demonstrates its use in the generation of a multiscale model of the physical and biological processes implicated in a challenging and clinically relevant problem, namely coronary artery in-stent restenosis.

Plasminogen activator inhibitor-1 predicts coronary in-stent restenosis of drug-eluting stents

BACKGROUND

We tested the hypothesis that plasma levels of plasminogen activator inhibitor-1 (PAI-1) are influenced by percutaneous coronary intervention (PCI) with the implantation of drug eluting stents (DES) and are able to predict the occurrence of in-stent restenosis (ISR).

METHODS AND RESULTS

PAI-1 active antigen plasma levels were determined in 75 patients before and 24 h after PCI with DES implantation. Patients with ISR after six to eight months (16%) showed significantly lower PAI-1 plasma levels before PCI (ISR, 11.7 +/- 8.1 ng mL(-1); non-ISR, 22.8 +/- 18.8 ng mL(-1); P <0.05). PAI-1 levels in the lowest tertile were associated with a 9.5-fold increased risk of ISR, independent of clinical risk factors, angiographic or procedural characteristics, compared to the highest tertile (P < 0.05). The induced change of PAI-1 active antigen 24 h after PCI was significantly higher in patients with ISR (ISR, +5.6 +/- 8.0 ng mL(-1); non-ISR, -3.2 +/- 12.1 ng mL(-1); P < 0.05) with positive correlation to late lumen loss (r = 0.30; P < 0.05).

CONCLUSIONS

ISR after DES implantation is significantly related to plasma levels of PAI-1 active antigen before and after PCI. If confirmed by larger multicenter studies, the determination of PAI-1 plasma levels might be clinically helpful in the identification of patients at high risk of developing of ISR, even after DES implantation.

Effect of folate on neointima formation and matrix metalloproteinase-9 expression after balloon injury in hyperhomocysteinemic rabbits

BACKGROUND

It is known that hyperhomocysteinemia (Hhcy) is associated with the risk of restenosis after angioplasty. Folate can lower plasma homocysteine (Hcy) level and alleviate the Hhcy-induced neointima formation after balloon injury. This study aims to explore the mechanisms of folate in inhibiting neointima formation.

METHODS

24 New Zealand White rabbits were randomly divided into three groups: Control, 2% methionine (Meth) and 2% methionine+folate (Meth+folate). At the end of 8 experimental weeks, all rabbits underwent the balloon injury in abdominal aorta. 4 weeks following this procedure, plasma Hcy concentration, aortic maximal neointimal thickness (NT), neointimal area (NA), medial area (MA), and ratio of neointimal area to medial area (NA/MA), ultrastructure of vascular smooth muscle cells (VSMCs), and matrix metalloproteinase-9 (MMP-9) expression were detected by high performance liquid chromatography, histomorphometric analysis, transmission electron microscope (TEM) and real-time PCR, respectively.

RESULTS

It was observed in our study that Hcy concentration, NT, NA, NA/MA and the expression of MMP-9 mRNA were higher in the Meth group than in the control. VSMCs in media exhibited typical synthetic phenotype in the Meth group compared with the transitional state between contractile phenotype and synthetic phenotype in the control group. However, in the rabbits treated with folate, Hcy concentration, NT, NA and MMP-9 mRNA expression were lower than those in the Meth group. The phenotype of VSMCs was close to that in the control group.

CONCLUSION

This study suggested that folate could decrease the level of Hcy, reverse the Hhcy-induced exacerbation of neointima formation in rabbits following balloon injury, and the mechanisms in it may be related to the suppressive effect of folate on the expression of MMP-9 mRNA in arterial wall.

Plasma metalloproteinase-12 and tissue inhibitor of metalloproteinase-1 levels and presence, severity, and outcome of coronary artery disease

Several matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) have been implicated in the development and outcome of coronary artery disease (CAD). We investigated whether MMP-12 and TIMP-1 levels were associated with risk, severity, and outcome of CAD. Plasma MMP-12 and TIMP-1 levels are measured in 50 and 44 patients with CAD, respectively, by enzyme-linked immunosorbent assay. Of all patients, 16 were taking statins. Patients who were not on statins were classified into 3 groups according to number of >50% stenotic vessels. Compared with 29 volunteers without CAD, patients without statins (n = 34) had higher MMP-12 concentrations (1.71 vs 1.08 ng/ml, p = 0.021). MMP-12 levels were significantly lower in patients with than in those without statin treatment (0.99 vs 1.71 ng/ml, p = 0.008). There was no association between MMP-12 levels and number of >50% stenotic vessels. MMP-12 concentrations were not associated with outcome of CAD. However, plasma TIMP-1 levels were associated with restenosis independently of number of stenotic vessels and age (p = 0.035) but not with risk or severity of CAD. In conclusion, plasma MMP-12 concentration was associated with the presence of CAD. Statin therapy decreases plasma MMP-12 levels in patients with CAD. Increased TIMP-1 levels may prevent restenosis after angioplasty.

Cyclic strain-mediated matrix metalloproteinase regulation within the vascular endothelium: a force to be reckoned with

The vascular endothelium is a dynamic cellular interface between the vessel wall and the bloodstream, where it regulates the physiological effects of humoral and biomechanical stimuli on vessel tone and remodeling. With respect to the latter hemodynamic stimulus, the endothelium is chronically exposed to mechanical forces in the form of cyclic circumferential strain, resulting from the pulsatile nature of blood flow, and shear stress. Both forces can profoundly modulate endothelial cell (EC) metabolism and function and, under normal physiological conditions, impart an atheroprotective effect that disfavors pathological remodeling of the vessel wall. Moreover, disruption of normal hemodynamic loading can be either causative of or contributory to vascular diseases such as atherosclerosis. EC-matrix interactions are a critical determinant of how the vascular endothelium responds to these forces and unquestionably utilizes matrix metalloproteinases (MMPs), enzymes capable of degrading basement membrane and interstitial matrix molecules, to facilitate force-mediated changes in vascular cell fate. In view of the growing importance of blood flow patterns and mechanotransduction to vascular health and pathophysiology, and considering the potential value of MMPs as therapeutic targets, a timely review of our collective understanding of MMP mechanoregulation and its impact on the vascular endothelium is warranted. More specifically, this review primarily summarizes our current knowledge of how cyclic strain regulates MMP expression and activation within the vascular endothelium and subsequently endeavors to address the direct and indirect consequences of this on vascular EC fate. Possible relevance of these phenomena to vascular endothelial dysfunction and pathological remodeling are also addressed.