Continuous subcutaneous angiopeptin treatment significantly reduces neointimal hyperplasia in a porcine coronary in-stent restenosis model

Impact of metabolic syndrome on re-stenosis development: role of drug-eluting stents

Metabolic syndrome (MetS) is defined as a cluster of numerous cardiovascular risk factors, which encompasses obesity, dyslipidaemia, insulin resistance and hypertension. Patients with MetS are more prone to developing cardiovascular events than other patients. To date, several approaches such as physical exercise, dietary control and invasive and non-invasive therapeutic interventions for dyslipidaemia, hypertension and insulin resistance have been used to manage MetS. However, there is a progressive elevation in the incidence of fatal and non-fatal cardiovascular events due to the increased prevalence of obesity and diabetes. Percutaneous coronary intervention has emerged over the last few years as an effective revascularisation strategy for those with coronary artery disease, in parallel with the development of effective anti-platelet medications and newer drug-eluting stents. In recent years, considerable research efforts have been undertaken to elucidate the pathophysiology of re-stenosis and develop strategies to prevent re-stenosis following percutaneous transluminal coronary angioplasty and stent implantation. Although the rate of stent re-stenosis and target-lesion revascularisation has been reduced, there is little information in the literature on the outcome of MetS in the pathophysiology of re-stenosis. In this review article, we summarise the recent development and progress on re-stenosis and the role of drug-eluting stents, particularly in MetS.

Preventing restenosis in early drug-eluting stent era: recent developments and future perspectives

Restenosis is the major limitation of the successful therapy of percutaneous coronary intervention (PCI) for patients with coronary artery disease. The problem was appreciated in the late 1970s to early 1980s. Only in recent years, anti-restenotic therapy has achieved a breakthrough with the development of drug-eluting stents. Here, we provide an overview about pathological mechanisms of restenosis after PCI. Present therapeutic approaches to overcome restenosis and recent clinical results are revisited, and some major concerns in the post-drug-eluting stent era are discussed.

First human experience with angiopeptin-eluting stent: a quantitative coronary angiography and three-dimensional intravascular ultrasound study

Angiopeptin has been shown to reduce in-stent restenosis in various animal models. Meanwhile, BiodivYsio DD phosphorylcholine (PC)-coated stent provides a platform for local delivery of antiproliferative agents to the coronary artery. We studied the feasibility, safety, and impact on tissue growth of angiopeptin-eluting BiodivYsio DD PC-coated stents in human native de novo coronary lesions. We enrolled 14 patients (16 lesions) who underwent intravascular ultrasound (IVUS)-guided angiopeptin-eluting stent implantation in native coronary arteries between 3.0 and 4.0 mm in diameter with lesion length<or=18 mm. We successfully implanted 13 stents loaded with 22 microg of angiopeptin and three stents with 126 microg of angiopeptin. No major adverse cardiac events or target vessel failure occurred at 1-year clinical follow-up. All patients underwent 6-month angiographic and volumetric IVUS follow-up. In-stent late loss was 0.46+/-0.32 mm in the low-dose group and 0.26+/-0.14 mm in the high-dose group. Binary restenosis rate was 0%. Follow-up percentage neointimal hyperplasia by IVUS was 18.4%+/-22.5% for the low-dose group and 10.2%+/-5.8% for the high-dose group, respectively. There were no edge effect and late stent malapposition. Angiopeptin-eluting BiodivYsio DD PC stent appears feasible and safe in treating native de novo coronary lesions with modest degree of neointimal hyperplasia.

Pharmacological treatment for prevention of restenosis

Coronary artery disease (CAD) is the leading cause of mortality and morbidity among adults in the Western world. Coronary artery bypass grafting and percutaneous coronary interventions (PCI) have gained widespread acceptance for the treatment of symptomatic CAD. There has been an explosive growth worldwide in the utilisation of PCI, such as balloon angioplasty and stenting, which now accounts for over 50% of coronary revascularisation. Despite the popularity of PCI, the problem of recurrent narrowing of the dilated artery (restenosis) continues to vex investigators. In recent years, significant advances have occurred in the understanding of restenosis. Two processes seem to contribute to restenosis: remodelling (vessel size changes) and intimal hyperplasia (vascular smooth muscle cell [VSMC] proliferation and extracellular matrix [ECM] deposition). Despite considerable efforts, pharmacological approaches to decrease restenosis have been largely unsuccessful and the only currently applied modality to reduce the restenosis rate is stenting. However, stenting only prevents remodelling and does not inhibit intimal hyperplasia. Several potential targets for inhibiting restenosis are currently under investigation including platelet activation, the coagulation cascade, VSMC proliferation and migration, and ECM synthesis. In addition, new approaches for local drug therapy, such as drug eluting stents, are currently being evaluated in preclinical and clinical studies. In this article, we critically review the current status of drugs that are being evaluated for restenosis at various stages of development (in vitro, preclinical animal models and human trials).

Site-specific intracoronary delivery of octreotide in humans: a pharmacokinetic study to determine dose-efficacy in restenosis prevention

Somatostatin analogues have been shown to inhibit smooth muscle cell proliferation after local administration in vivo in animal models and in vitro using human coronary smooth muscle cell cultures. However, the optimal dosage for attaining effective site-specific administration remains undefined. This study was performed to determine the required theoretical dose of the somatostatin analogue, octreotide, to be delivered site specifically, for prevention of restenosis after coronary angioplasty in humans using a previously described methodology to determine regional pharmacokinetics of site-specific intracoronary administrated compounds. In 7 patients, 111In-octreotide, a gamma-labeled somatostatin analogue, was infused post angioplasty at the site of dilatation via a coil-balloon and quantified using a radio-isotopic technique. Efficiency of delivery ranged from 0.1% to 2.7% of the total infused dose of 0.18 microg, corresponding to a mean peak delivered amount of 1.8 +/- 1.9 ng. Total locally bioavailable 111In-octreotide reached 2.28 +/- 2.15 ng h. Based on current in vitro bioavailability and peak concentration data to inhibit proliferation and thymidine incorporation in human coronary smooth muscle cells, a 4000x higher averaged dose (approximately 700 microg) should be infused site specifically to obtain a biologic efficacy in 50% of the treated patients (ED50). Quantification of regional pharmacokinetics enables the determination of a theoretical site-specific dose for achieving appropriate bioavailability above the therapeutic threshold concentration for smooth muscle cell inhibition. This approach is proposed for the determination of the appropriate site-specific coronary infusion dose for the inhibition of restenosis after balloon angioplasty.

Stent-induced restenosis in the swine coronary artery is inhibited by a platelet-derived growth factor receptor tyrosine kinase inhibitor, TKI963

Activities of vascular smooth muscle cells (SMCs) such as proliferation, migration, and matrix production contribute to restenosis following clinical interventions of angioplasty and stent placement. Because activation of platelet-derived growth factor (PDGF)-receptor tyrosine kinase (PDGFr-TK) influences these processes and promotes restenosis, TKI963, an inhibitor of the PDGFr-TK was discovered, and its efficacy was evaluated in blocking stent-induced restenosis as analyzed by intravascular ultrasound (IVUS). TKI963, a low-molecular-weight compound, inhibited the cell-free PDGFbetar-TK with a K(i) value of 56 +/- 14 nM. TKI963 also inhibited PDGF-dependent events in human aortic SMCs (e.g., in situ PDGFr autophosphorylation, mitogenesis, chemotaxis, and collagen production with median inhibitory concentration values of approximately 300 nM) without affecting the activity of a series of membrane receptor tyrosine kinases and intracellular serine/threonine kinases. In vivo, stent-induced restenosis in the swine coronary artery was reduced by oral administration of TKI963 (1.25, 2.5, and 5 mg/kg BID, for 28 days). Late lumen cross-sectional area (CSA) loss, plaque CSA growth, and plaque volume in the stent determined by IVUS were dose-relatedly decreased (33-62% at 1.25 mg/kg BID to 66-92% at 5 mg/kg BID, depending on the parameter) compared with controls. TKI963 treatment of </=1 week following stent placement had no effect on the prevention of restenosis. TKI963, a selective, orally bioavailable inhibitor of the PDGFr-TK, dose-relatedly reduced stent-induced restenosis and did so by inhibiting PDGF-dependent activities that occur as late events following stent placement.

Elimination of vascular fibrointimal hyperplasia by somatostatin receptor 1,4-selective agonist

The somatostatin analogs octreotide and lanreotide, selective to receptor subtypes 2 and 5, failed clinical efficacy for the prevention of restenosis after percutaneous transluminal angioplasty. These findings might have been the result of targeting a wrong subset of receptors. In rat arteries, subtypes 1 and 4 are expressed 3-4 times more prominently than 2 and 5, and subtype 1 is the nearly exclusive subtype in atherosclerotic human vessels. Here, we demonstrate that daily s.c. injections (50-500 microg/kg/d) of CH275 (DesAA1,2,5(D-W8,IAmp9)Somatostatine-14), selective to subtypes 1 and 4, dose-dependently inhibited intimal hyperplasia 14 days after rat carotid denudation injury (for intimal area P=0.0002 across the dose range). CH275 was more effective than somatostatin-14 (equal affinity to all five subtypes, P=0.03), or octreotide (selective to subtypes 2 and 5, P=0.098). When rats were given the peptides for 14 days with end-point at 28 days, CH275 still significantly inhibited intimal area expansion. Both CH275 and octreotide inhibited the outgrowth of cells from postinjury aortic tissue punch-explants and the distance migrated in vitro, but not cell replication, which indicated that the effects of somatostatin analogs were directed on the migration of intimal cell progenitors rather than on their proliferation.

Novel approaches for the prevention of restenosis

Restenosis, the re-narrowing of the lumen of the coronary artery, in the months following a successful percutaneous balloon angioplasty or stenting, remains the main limitation to percutaneous coronary revascularisation. Serial intravascular ultrasound studies have shown that restenosis after conventional balloon angioplasty represents a complex interplay between elastic recoil, smooth muscle proliferation and vascular remodelling, while restenosis after stent deployment is due almost entirely to smooth muscle hyperplasia and matrix proliferation. Despite intensive investigation in animal models and in clinical trials, most pharmacological agents have been found to be ineffective in preventing restenosis after percutaneous balloon angioplasty or stenting. Although studies frequently report success in the suppression of neointimal proliferation in animal models of balloon vascular injury, few of them have been successful in clinical trials. Lately, the advent of endovascular radiation, new antiproliferative agents, recombinant DNA, growth factor regulators and novel local drug delivery systems have shown promising results. In the past five years, intracoronary radiation with gamma- and beta-emitting sources has been evaluated intensively with very encouraging results. This is the first potent non-pharmacological approach that has been successful in a large number of patients in controlling excessive tissue proliferation. It is very likely that a combination of stents and pharmacological and/or non-pharmacological inhibition of neointimal hyperplasia will likely result in further reductions in the incidence if restenosis. The continued attractiveness of percutaneous coronary revascularisation, as an alternative to medical treatment or bypass surgery for patients with coronary artery disease, will depend upon our ability to control the restenotic process. Due to the vast literature on the subject, this review will focus mainly on clinical trials that show the most promise and will highlight those that warrant further investigation.

Hyperinsulinemia during oral glucose tolerance test is associated with increased neointimal tissue proliferation after coronary stent implantation in nondiabetic patients: a serial intravascular ultrasound study

OBJECTIVES

The purpose of this study was to determine whether hyperinsulinemia during the oral glucose tolerance test is associated with increased neointimal tissue proliferation after coronary stent implantation in nondiabetic patients.

BACKGROUND

Although hyperinsulinemia induces increased vascular smooth muscle cell proliferation in experimental models, it has not been determined whether hyperinsulinemia is associated with increased neointimal tissue proliferation after coronary stent implantation.

METHODS

Serial (postintervention and six-month follow-up) intravascular ultrasound (IVUS) was used to study 67 lesions treated with Palmaz-Schatz stents in 55 nondiabetic patients. Cross-sectional images within stents were taken at every 1 mm, using an automatic pullback, and a neointimal index was calculated as the ratio between the averaged neointimal area and averaged stent area. All patients underwent a 75-g oral glucose tolerance test. Plasma glucose (PG) and immunoreactive insulin (IRI) levels were measured at baseline and 1 and 2 h after the glucose load. The sum of PGs (sigmaPG) and the sum of IRIs (sigmaIRI) were calculated. Body mass index (BMI), lipid levels, and glycosylated hemoglobin levels were measured.

RESULTS

There were 27 patients with normal glucose tolerance, and 28 patients with impaired glucose tolerance (IGT). The neointimal index in patients with IGT was greater than that in patients with normal glucose tolerance (42.9 +/- 14% vs. 24.9 +/- 8.3%, respectively, p < 0.0001). Linear regression analysis showed that the neointimal index at follow-up correlated well with sigmaPG (p < 0.0001), fasting IRI (p < 0.0001), sigmaIRI (p < 0.0001), triglyceride level (p = 0.018), and BMI (p < 0.0001). Multiple regression analysis revealed that sigmaIRI (p = 0.0002) and sigmaPG (p = 0.0034) were the best predictors of the greater neointimal index at follow-up.

CONCLUSIONS

Serial IVUS assessment shows that hyperinsulinemia during an oral glucose tolerance test is associated with increased neointimal tissue proliferation after coronary stent implantation in nondiabetic patients.

Basic principles of angiogenesis for the interventional cardiologist

Despite tremendous advances in the management of coronary artery disease, there is a growing population of patients who remain symptomatic with residual myocardial ischemia. Therapeutic angiogenesis, designed to promote the development of endogenous conduits forming collateral blood vessels that serve to bypass coronary artery stenotic lesions, may constitute an alternative treatment strategy for patients with extensive tissue ischemia in whom contemporary therapies-antianginal medications, angioplasty, bypass surgery-have failed or are not feasible. Intensive investigation is now focused on methods that would have the potential to stimulate the development of collaterals in humans. In this review we summarize the physiology of angiogenesis and its role in development and adult life, its regulation, the effects of ischemia and hypoxia, the principles of gene therapy for angiogenesis, and an update on the current available trials data of angiogenic cytokines administration.

Expression of IGF-1, IGF-1 receptor and TGF-beta following balloon angioplasty in atherosclerotic and normal rabbit iliac arteries: an immunocytochemical study

Growth factors have been implicated in the pathogenesis of restenosis (myointimal hyperplasia after coronary interventions). In this study, we examined the expression of insulin-like growth factor-I (IGF-1), IGF-1 receptor, and transforming growth factor-beta (TGF-beta) in atherosclerotic and normal rabbit iliac arteries following overstretch balloon angioplasty of the iliac arteries to create a vascular lesion. Animals were sacrificed at 0, 3, 7, 15 and 42 days post angioplasty. The iliac arteries were processed for immunocytochemical localization of IGF-1, IGF-1 receptor and TGF-beta using colloidal gold and the data were quantitatively analyzed. IGF-1, IGF-1 receptor and TGF-beta immunoreactivity were all significantly increased in atherosclerotic arteries compared to control at all of the time points examined. Following balloon angioplasty, the levels of IGF-1 and IGF-1 receptor increased significantly in both control and even further in hypercholesterolemic vessels. In control vessels, the IGF-1 levels returned to preintervention levels, while in atherosclerotic vessels, the levels of IGF-1 and IGF-1 receptor remained elevated. In addition, TGF-beta levels in control vessels showed an initial rise in the first week following injury but then returned to baseline levels. In contrast, atherosclerotic vessels demonstrated a sustained expression of TGF-beta. Thus, IGF-1 and TGF-beta expression is different in normal vs. atherosclerotic vessels following vascular injury. The intensity of expression of IGF-1 and its receptor, which is not reduced at 42 days compared to 15 days following injury, support a role for IGF-1 in smooth muscle cell proliferation and migration. The sustained increase in TGF-beta could facilitate extracellular matrix (ECM) accumulation. Local vascular therapy that is directed towards modulating the effects of IGF-1 and TGF-beta could reduce restenosis.

[Pathophysiology and therapeutic concepts in coronary restenosis]

Demonstration of a reduced restenosis rate after stent implantation (Benestent, STRESS) has initiated rapid increase in stent implantation rates with widening indications. At present, the majority of stents are implanted in "none-Benestent/STRESS-lesions" with the consequence of a higher restenosis rate as previously expected. Stent restenosis has therefore become a relevant problem in interventional cardiology. In contrast to balloon angioplasty, where acute and subacute recoil represents the major mechanism of restenosis, stent restenosis is exclusively attributed to neointima proliferation. Morphological studies have demonstrated that neointima is caused by early smooth muscle cell ingrowth with a maximum after 7 days which is then gradually replaced by extracellular matrix. Systematic clinical, angiographic and intravascular ultrasound studies have identified several risk factors for increased stent restenosis such as: diabetes mellitus, treatment of restenosis, serial stent implantation, small and calcified vessels, ostial lesions, venous bypass grafts and complex stenosis morphology. In addition, there is increasing evidence that aggressive implantation techniques with high pressures and oversized balloons may also induce higher restenosis rates. Optimal treatment of instent restenosis has not been determined so far. Balloon angioplasty is at present considered the therapeutic option of choice. Several small studies have shown, that in short, discrete lesions (< 10 mm) results of simple PTCA are acceptable with re-restenosis rates between 15 and 35%. The intervention is considered safe with low complication rates. In 10 to 15% additional stent implantation is necessary, usually due to dissections proximal or distal to the treated stent. In long, diffuse stent restenosis (> or = 10 mm), however, PTCA results in high re-restenosis rates up to > 80%. This is most likely due to insufficient early balloon angioplasty results with minimal luminal diameters (MLD) significantly below the previous stent diameter. Therefore, debulking techniques have been used to reduce neointima burden within the stent. At present 3 techniques are available: directional coronary atherectomy (DCA), Excimerlaser angioplasty (ELCA) or high frequency rotablation. All of these techniques achieve a significant reduction in plaque volume within the stent and in combination with balloon angioplasty allow larger MLDs than PTCA alone. Limited experiences with ELCA and rotablation have shown that the techniques are safe without major periinterventional complications. DCA, however, has been accompanied with stent destruction and therefore should be considered with large care, especially in stents with coil design. At present, no randomized controlled trials for the comparison of debulking techniques with or without balloon angioplasty versus balloon angioplasty alone are available. Three multicenter trials have been initiated (LARS, ARTIST and TWISTER) to compare debulking techniques versus balloon angioplasty in diffuse stent restenosis. Adjunct medical treatment after interventions for stent restenosis is usually limited to ASS alone, indications for additional application of Ticlopidine have not been verified so far. Positive results are expected for the use of local radiation therapy either by radioactive stent implantation or afterloading techniques. With increasing stent implantation rates and indications, about 400,000 stents will be implanted in 1997 worldwide. Considering a low restenosis rate of 20%, 80,000 stent restenosis will occur within one year. Final recommendations for optimal treatment of these patients are not yet available.