Local adenovirus-mediated delivery of hirudin in a rabbit arterial injury 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.

Cardiovascular gene delivery: The good road is awaiting

Atherosclerotic cardiovascular disease is a leading cause of death worldwide. Despite recent improvements in medical, operative, and endovascular treatments, the number of interventions performed annually continues to increase. Unfortunately, the durability of these interventions is limited acutely by thrombotic complications and later by myointimal hyperplasia followed by progression of atherosclerotic disease over time. Despite improving medical management of patients with atherosclerotic disease, these complications appear to be persisting. Cardiovascular gene therapy has the potential to make significant clinical inroads to limit these complications. This article will review the technical aspects of cardiovascular gene therapy; its application for promoting a functional endothelium, smooth muscle cell growth inhibition, therapeutic angiogenesis, tissue engineered vascular conduits, and discuss the current status of various applicable clinical trials.

Inhibition of Intimal Hyperplasia by Direct Thrombin Inhibitors in an Animal Vein Bypass Model

Many functions of the coagulation system have nonthrombotic effects. The indirect thrombin inhibitor heparin has been previously shown to be effective in limiting intimal hyperplasia (IH). We sought to study the effect of thrombin on IH by using two direct thrombin inhibitors (DTIs), argatroban and lepirudin. Sprague-Dawley rats underwent interposition vein grafting to the carotid artery. Vein grafts were treated with either saline (n = 6) or one of the two DTIs (n = 6 for both). At 30 days, the rats were sacrificed and vessels were perfusion fixed. Sections of the proximal carotid artery, graft, and both anastomoses were stained with both hematoxlyin/eosin and von Gieson's elastin stain. Sections were examined and compared for luminal area and intima-to-media (IM) ratio. The vessels treated with DTIs had less (p < 0.05) IH (IM ratio for proximal anastomosis: control 1.036 +/- 0.857, lepirudin 0.373 +/- 0.21, argatroban 0.182 +/- 0.118) and better lumen preservation than the control vessels (lumen area of proximal anastomosis: control 1.69 +/- 0.9, lepirudin 2.45 +/- 0.74, argatroban 2.81 +/- 0.78). There were no thromboses in the DTI-treated vessels. Dilatation of the graft segment was noted in the argatroban group. Thus, DTIs are effective at reducing IH in a small-animal model, suggesting that inhibition of thrombin has a protective role in IH. In addition, a difference of action between DTIs is suggested by the dilatation seen only in the argatroban-treated graft sections.

Gene transfer therapy in vascular diseases

Somatic gene therapy of vascular diseases is a promising new field in modern medicine. Recent advancements in gene transfer technology have greatly evolved our understanding of the pathophysiologic role of candidate disease genes. With this knowledge, the expression of selective gene products provides the means to test the therapeutic use of gene therapy in a multitude of medical conditions. In addition, with the completion of genome sequencing programs, gene transfer can be used also to study the biologic function of novel genes in vivo. Novel genes are delivered to targeted tissue via several different vehicles. These vectors include adenoviruses, retroviruses, plasmids, plasmid/liposomes, and oligonucleotides. However, each one of these vectors has inherent limitations. Further investigations into developing delivery systems that not only allow for efficient, targeted gene transfer, but also are stable and nonimmunogenic, will optimize the clinical application of gene therapy in vascular diseases. This review further discusses the available mode of gene delivery and examines six major areas in vascular gene therapy, namely prevention of restenosis, thrombosis, hypertension, atherosclerosis, peripheral vascular disease in congestive heart failure, and ischemia. Although we highlight some of the recent advances in the use of gene therapy in treating vascular disease discovered primarily during the past two years, many excellent studies published during that period are not included in this review due to space limitations. The following is a selective review of practical uses of gene transfer therapy in vascular diseases. This review primarily covers work performed in the last 2 years. For earlier work, the reader may refer to several excellent review articles. For instance, Belalcazer et al. (6) reviewed general aspects of somatic gene therapy and the different vehicles used for the delivery of therapeutic genes. Gene therapy in restenosis and stimulation of angiogenesis in the cardiac muscle are discussed in reviews by several investigators (13,26,57,74,83). In another review, Meyerson et al. (43) discuss advances in gene therapy for vascular proliferative disorders and chronic peripheral and cardiac ischemia.

Prevention of restenosis by a herpes simplex virus mutant capable of controlled long-term expression in vascular tissue in vivo

Neointimal hyperplasia resulting from vascular smooth muscle cell (SMC) proliferation and luminal migration is the major cause of autologous vein graft failure following vascular coronary or peripheral bypass surgery. Strategies to attenuate SMC proliferation by the delivery of oligonucleotides or genes controlling cell division rely on the use of high concentrations of vectors, and require pre-emptive disruption of the endothelial cell layer. We report a genetically engineered herpes simplex virus (HSV-1) mutant that, in an in vivo rabbit model system, infects all vascular layers without prior injury to the endothelium; expresses a reporter gene driven by a viral promoter with high efficiency for at least 4 weeks; exhibits no systemic toxicity; can be eliminated at will by administration of the antiviral drug acyclovir; and significantly reduces SMC proliferation and restenosis in vein grafts in immunocompetent hosts.

Gene therapy for acute diseases

The use of gene transfer systems to study cell function makes it apparent that overexpression of a transgene can restore or improve the function of a protein and positively influence cell function in a predetermined manner for purposes of counterbalancing cellular pathophysiology. The ability of some gene transfer vehicles to produce transgene product within hours of delivery positions gene transfer as a unique pharmaceutical administration system that can quickly affect production of biologic response modifiers in a highly compartmentalized fashion. This approach can be expected to overcome many of the adverse effects and high costs of systemic delivery of recombinant pharmaceuticals. This review highlights recent advances toward development of gene therapies for acute illnesses with particular emphasis on preclinical models of disease. In this context, a growing body of data suggests that gene therapies for polygenic and non-genetic diseases such as asthma, cardiogenic and non-cardiogenic pulmonary edema, stroke, subarachnoid hemorrhage, seizures, acute myocardial infarction, endovascular thrombosis, and infections may someday be options for the treatment of patients.

Selective alpha(v)beta(3)-receptor blockade reduces macrophage infiltration and restenosis after balloon angioplasty in the atherosclerotic rabbit

BACKGROUND

alpha(v)beta(3)-Integrin receptors are upregulated in atherosclerotic arteries and play a key role in smooth muscle cell and possibly inflammatory cell migration. We hypothesized that after balloon angioplasty (BA) of atherosclerotic arteries, selective inhibition of the alpha(v)beta(3)-receptor by XT199, a small-molecule, non-peptide-selective alpha(v)beta(3)-receptor antagonist, would reduce restenosis.

METHODS AND RESULTS

After induction of focal atherosclerosis, rabbits underwent femoral BA and received XT199 (2.5 mg/kg IV bolus plus 2.5 mg. kg(-1). d(-1) IV; n=19) or vehicle (n=20) for 14 days. At 28 days after BA, the XT199 group had a larger lumen (0.75+/-0.26 versus 0.57+/-0.20 mm(2), P=0.03) and a smaller neointimal area (0.49+/-0.18 versus 0.68+/-0.25 mm(2), P=0.01) than the vehicle group. Angiographic analysis confirmed a 30% to 40% reduction in restenosis. Arteries harvested at 28 days after BA did not show a reduction in intima plus media smooth muscle cell content but did show a 50% reduction in macrophage cell density in the XT199 group (716+/-452 versus 1458+/-989 cells/mm(2), P<0.006). Neovessel density at 28 days was also reduced (23+/-42 versus 58+/-46 vessel cross sections/mm(2), P<0.02). Early after BA (ie, 3 to 7 days), there was a decrease in intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression, indicative of a reduction in vascular cell activation.

CONCLUSIONS

Selective alpha(v)beta(3)-receptor blockade for 14 days after BA in the focally atherosclerotic rabbit significantly reduced restenosis and limited macrophage infiltration and neovascularization in the vessel wall.

Nonviral in vivo gene therapy for tissue engineering of articular cartilage and tendon repair

Heretofore, nonviral methods have been used primarily for in vitro transfection of cultured cell lines. These methods were substantially less efficient when compared with the use of viruses, particularly when used in vivo. Herein a three-step, highly efficient method of nonviral gene delivery is presented. Using this method, genes have been delivered successfully into tissues of orthopaedic importance with high-efficiency by nonviral means. Transforming growth factor-beta 1, parathyroid hormone related protein, and a marker gene were transfected into primary perichondrium and cartilage cells with efficiencies in excess of 70%. They overexpressed their cognate gene products showing efficacy of expression in a rabbit model of osteochondral defect repair. Using the same method, a marker gene was delivered into a canine model for intrasynovial flexor tendon injury and repair. This was achieved by direct gene delivery during surgery. An estimated 5 additional minutes were required during surgery to complete the transfection steps. High efficiency gene delivery was achieved in the flexor tendons, tendon sheaths, tendon pulleys, surrounding tissues, and skin. The efficiency of transfection approached 100% in the exposed superficial tissue layers and transfected cells were found several layers below the exposed tissue surfaces. The data show the potential of direct nonviral gene therapy in orthopaedics for ex vivo and in vivo applications.