Inhibition of intimal hyperplasia by an antisense oligonucleotide of farnesyl transferase delivered endoluminally during iliac angioplasty in a rabbit model

Gene Therapy for the Extension of Vein Graft Patency: A Review

The mainstay of treatment for long-segment small-vessel chronic occlusive disease not amenable to endovascular intervention remains surgical bypass grafting using autologous vein. The procedure is largely successful and the immediate operative results almost always favorable. However, the lifespan of a given vein graft is highly variable, and less than 50% will remain primarily patent after 5 years. The slow process of graft malfunction is a result of the vein's chronic maladaptive response to the systemic arterial environment, its primary component being the uncontrolled proliferation of vascular smooth muscle cells (SMCs). It has recently been suggested that this response might be attenuated through pre-implantation genetic modification of the vein, so-called gene therapy for the extension of vein graft patency. Gene therapy seems particularly well suited for the prevention or postponement of vein graft failure since: (1) the stimulation of SMC proliferation appears to largely be an early and transient process, matching the kinetics of current gene transfer technology; (2) most veins are relatively normal and free of disease at the time of bypass allowing for effective gene transfer using a variety of systems; and (3) the target tissue is directly accessible during operation because manipulation and irrigation of the vein is part of the normal workflow of the surgical procedure. This review briefly summarizes the current knowledge of the incidence and basic mechanisms of vein graft failure, the vector systems and molecular targets that have been proposed as possible pre-treatments, the results of experimental genetic modification of vein grafts, and the few available clinical studies of gene therapy for vascular proliferative disorders.

Inhibition of non-Ras protein farnesylation reduces in-stent restenosis

Ras has a key role in relation to cell proliferation, survival and migration and requires farnesylation for full activity. The effects of a Ras farnesyl transferase inhibitor, FPT III on human atherosclerotic vascular smooth muscle (VSM) cells proliferation and p42/p44 mitogen-activated protein kinase (p42/p44 MAPK) activity was measured. In addition the ability of FPT III to modify the development of neointimal growth was tested in cultured human arteries and in a rabbit model of in-stent restenosis. In human VSM cells FPT III (25 microM) inhibited FCS-stimulated cell proliferation through a ras-dependent mechanism (after 18 h exposure) and also a novel ras-independent mechanism (following 15 min exposure). FPT III incubation (18 h) inhibited platelet-derived growth factor (PDGF)-stimulated p42/p44 MAPK activation and p21 Ras membrane localization, whereas 15 min incubation had no effect on the activation of p42/p44 MAPK in response to PDGF (added at 18 h) or on membrane p21 Ras localization (measured at 18 h). In cultured human atherosclerotic arteries, the presence of 25 microM FPT III significantly reduced neointimal growth. In vivo, 15 min local infusion of 25 microM FPT III significantly reduced in-stent restenosis 28 days later without affecting vascular function in normal rabbit artery. This study demonstrates that brief administration of a farnesyl transferase inhibitor reduced in-stent restenosis in a rabbit model without deleterious effects on vascular function or endothelial regrowth. Acute application of FPT III was found to act through a novel mechanism to inhibit smooth muscle cell proliferation via a non-ras pathway, which may contribute to the prevention of in-stent restenosis.

Lipid-modified proteins as biomarkers for cardiovascular disease: a review

Lipid-modified proteins are classified based on the identity of the attached lipid, a post- or co-translational modification required for their biological function. At least five different lipid modifications of cysteines, glycines and other residues on the COOH- and NH(2)-terminal domains have been described. Cysteine residues may be modified by the addition of a 16-carbon saturated fatty acyl group by a labile thioester bond (palmitoylation) or by prenylation processes that catalyze the formation of thioether bond with mevalonate derived isoprenoids, farnesol and geranylgeraniol. The NH(2)-terminal glycine residues may undergo a quite distinct process involving the formation of an amide bond with a 14-carbon saturated acyl group (myristoylation), while glycine residues in the COOH-terminal may be covalently attached with a cholesterol moiety by an ester bond. Finally, cell surface proteins can be anchored to the membrane through the addition of glycosylphosphatidylinositol moiety. Several lines of evidence suggest that lipid-modified proteins are directly involved in different steps of the development of lesions of atherosclerosis, from leukocyte recruitment to plaque rupture, and their expression or lipid modification are likely altered during atherogenesis. This review will briefly summarize the different enzymatic pathways of lipid modification and propose a series of lipid-modified proteins that can be used as biomarkers for cardiovascular disease.

Local gene delivery to the vessel wall

This review will provide an overview of delivery strategies that are being evaluated for vascular gene therapy. We will limit our discussion to those studies that have been demonstrated, utilizing in vivo model systems, to limit post-interventional restenosis. We also discuss the efficacy of the vectors and methods currently being used to transfer genetic material to the vessel wall. The efficiency of these techniques is a critical issue for the successful application of gene therapy.

Downregulation of the ERK 1 and 2 mitogen activated protein kinases using antisense oligonucleotides inhibits proliferation of porcine vascular smooth muscle cells

The current model of the arterial response to injury suggests that proliferation of vascular smooth muscle cells is a central event. Mitogen activated protein kinases are part of the final common pathway of intracellular signalling involved in cell division and thus constitute an attractive target in attempting to inhibit this proliferation. We hypothesised that antisense oligonucleotides to mitogen activated protein kinase would inhibit serum induced smooth muscle cell proliferation by downregulating the protein. Porcine vascular smooth muscle cells were cultured and an antisense oligonucleotide sequence against the ERK family of mitogen activated protein kinases (AMK1) was introduced by liposomal transfection. Sense oligonucleotides and a random sequence were used as controls. Proliferation was inhibited by AMK1 versus the sense controls, as assessed by tritiated thymidine incorporation (P<0.01). Immunoblots revealed downregulation of the target protein by AMK1 by 63% versus the sense control (P<0.05). In conclusion, antisense oligonucleotides specifically inhibited proliferation and downregulated the target protein. This is consistent with a central role for mitogen activated protein kinases in vascular smooth muscle cell proliferation in the porcine model. In addition, the data suggest a possible role for antisense oligonucleotides in the modulation of the arterial injury response.

Gene Therapy for Cardiovascular Disease

During the past decade, gene therapy for the treatment of many inherited and acquired medical problems has become the subject of increasing focus in both the scientific litera ture and the lay press. This review examines the history and current status of gene therapy for advanced chronic periph eral and myocardial ischemia.

The mechanisms of coronary restenosis: insights from experimental models

Since its introduction into clinical practice, more than 20 years ago, percutaneous transluminal coronary angioplasty (PTCA) has proven to be an effective, minimally invasive alternative to coronary artery bypass grafting (CABG). During this time there have been great improvements in the design of balloon catheters, operative procedures and adjuvant drug therapy, and this has resulted in low rates of primary failure and short-term complications. However, the potential benefits of angioplasty are diminished by the high rate of recurrent disease. Up to 40% of patients undergoing angioplasty develop clinically significant restenosis within a year of the procedure. Although the deployment of endovascular stents at the time of angioplasty improves the short-term outcome, 'in-stent' stenosis remains an enduring problem. In order to gain an insight into the mechanisms of restenosis, several experimental models of angioplasty have been developed. These have been used together with the tools provided by recent advances in molecular biology and catheter design to investigate restenosis in detail. It is now possible to deliver highly specific molecular antagonists, such as antisense gene sequences, to the site of injury. The knowledge provided by these studies may ultimately lead to novel forms of intervention. The present review is a synopsis of our current understanding of the pathological mechanisms of restenosis.

Improving vascular grafts: the importance of mechanical and haemodynamic properties

In the last 40 years, as techniques and materials have improved, the success rate of vascular prostheses with a diameter greater than 6mm has risen steadily, 5-year survival rates exceeding 95% in most centres. With smaller grafts no comparable improvement has occurred, the majority failing within 5 years, usually as a result of intimal hyperplasia and, ultimately atherosclerosis, in and around the downstream anastomosis. Clinical evidence suggests that the patency rates of small grafts are improved by matching the elastic properties of the graft to that of the artery into which it is placed. Although there is little reliable evidence that 'elastic mismatch' per se is the cause of intimal hyperplasia, it is generally accepted that mechanical factors are important in its genesis. These include disturbed flow at the anastomosis leading to fluctuations in shear stress at the endothelium (a known cause of intimal hyperplasia in normal arteries), injury due to suturing and stress concentration at the anastomosis. Few suitable materials or techniques have yet been developed to improve the long-term survival rates of small grafts. Recent advances in tissue engineering in which prostheses are manufactured by culturing vascular smooth muscle cells on a tubular scaffold of biodegradable polymer may ultimately make it possible to manufacture biologically and haemodynamically compatible grafts with diameters as small as 1mm.

Effects of hydroxymethylglutaryl coenzyme A reductase inhibitor simvastatin on smooth muscle cell proliferation in vitro and neointimal formation in vivo after vascular injury

OBJECTIVES

We sought to evaluate the effects of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors on vascular smooth muscle cell (VSMC) proliferation in vitro and neointimal formation in vivo after vascular injury.

BACKGROUND

Neointimal hyperplasia after vascular injury is responsible for restenosis after arterial stenting, whereas arterial remodeling and neointimal formation are the causes of restenosis after percutaneous transluminal coronary angioplasty.

METHODS

We assessed the effect of simvastatin on in vitro VSMC proliferation. To study the effects of simvastatin in vivo, balloon injury and stent deployment were performed in the common carotid artery of rats. Neointimal area was measured two weeks later in the balloon injury model and three weeks after stent deployment.

RESULTS

Simvastatin markedly inhibits VSMC proliferation in vitro. In vivo, simvastatin reduced, in a dose-dependent manner, the neointimal area and the neointima-media ratio after balloon injury from 0.266 +/- 0.015 mm2 to 0.080 +/- 0.026 mm2 and from 1.271 +/- 0.074 to 0.436 +/- 0.158 (p < 0.001 vs. control rats) at the highest dose. Simvastatin also significantly reduced the neointimal formation and the neointima-media ratio after stenting from 0.508 +/- 0.035 mm2 to 0.362 +/- 0.047 mm2 (p < 0.05 vs. control rats) and from 2.000 +/- 0.136 to 1.374 +/- 0.180 (p < 0.05 vs. control rats). The vessel thrombosis rate after stent deployment was 30% in the control group and 11.1% in the treated group (p = NS). Moreover, the systemic administration of simvastatin did not affect hepatic and renal functions, blood pressure or heart rate.

CONCLUSIONS

Simvastatin potently inhibits VSMC proliferation in vitro and reduces neointimal formation in a rat model of vascular injury.

Gene therapy as a therapeutic intervention for vascular disease

Gene therapy for the treatment of many medical problems, including vascular disease, has become the subject of increasing discussion in both the scientific literature and the national press over the past decade. This review will examine the history and current status of gene therapy for vascular proliferative disorders and advanced chronic peripheral and cardiac ischemia.