The advent of adenovirus. Gene therapy for cardiovascular disease

Delivery of human interferon-gamma via gene transfer in vitro: prolonged expression and induction of macrophage antimicrobial activity

Daily parenteral administration of exogenous interferon-gamma (IFN-gamma) induces or accelerates recovery in experimental and human infections. To develop an alternative delivery system, a replication-defective recombinant adenovirus expressing human IFN-gamma was constructed. The complete coding region of IFN-gamma was amplified by RT-PCR and inserted into an adenovirus cloning vector under the control of a human cytomegalovirus promoter. Recombinant adenovirus containing the IFN-gamma minigene (dAv-IFN-gamma) was isolated from 293 cells co-transfected with the linearized plasmid and an E1 region-deleted fragment of adenovirus genome. Following in vitro infection with dAv-IFN-gamma, dose-dependent and time-dependent expression of IFN-gamma, mRNA and production of soluble protein were demonstrated in human diploid fibroblat and HeLa cell cultures by Northern blot and ELISA, respectively. Extracellular protein secretion persisted for > = 4 weeks following initial transfection, and secreted IFN-gamma induced both antiviral activity (8000-25,000 U/ml) and macrophage activation with killing of intracellular Toxoplasma gondii and leishmania donovani. These results establish that dAv-IFN-gamma generates long-term secretion of biologically active IFN-gamma in vitro and suggest that this vector may be a useful delivery system for cytokine therapy.

Transvenous procurement of pulmonary artery smooth muscle and endothelial cells using a novel endoarterial biopsy catheter in a canine model

OBJECTIVES

The aim of this study was to evaluate the performance of a new arterial biopsy catheter in obtaining pulmonary endovascular samples in a canine model.

BACKGROUND

Percutaneous endomyocardial biopsy is a widely used and valuable procedure in the management of posttransplant rejection and selected cardiomyopathies. A similar method of obtaining endoarterial biopsy samples would aid in the study, diagnosis and management of arterial diseases.

METHODS

Catheterization was performed in 19 dogs, each weighing 20 to 30 kg, through an 8F sheath in the external jugular vein to obtain pulmonary endoarterial samples. The catheter consists of two sliding tubes: an inner one with a beveled opening that accommodates endoarterial tissue by means of a vacuum and an outer tube with a sharp distal edge that cuts the tissue when activated.

RESULTS

Overall, a total of 266 separate biopsy attempts were performed, and 161 tissue samples were obtained (success rate 61%). With modifications in technique in the last nine dogs, 54 (93%) of 58 attempts were successful. There were no deaths, extravasation of contrast material on angiography or thrombi. Of 20 vessels with prebiopsy and postbiopsy angiograms, 1 developed transient spasm (5%). On microscopic examination of cross sections of 50 separate pulmonary endoarterial biopsy samples, all had smooth muscle cells and 30 contained endothelial cells (60%). The arteries of origin showed small intimal and medial tears and mild perivascular hemorrhage. Angiographic and pathologic examination of previously biopsied arterial segments 2 weeks (two dogs) and 8 weeks (two dogs) after the procedure showed patent vessels and no thrombi. Histologically, the biopsy sites revealed mild neointimal and medial proliferation.

CONCLUSIONS

This new endoarterial biopsy catheter is safe and effective in obtaining pulmonary artery samples in normotensive dogs.

Adenovirus-mediated gene transfer into normal rabbit arteries results in prolonged vascular cell activation, inflammation, and neointimal hyperplasia

Adenovirus vectors are capable of high efficiency in vivo arterial gene transfer, and are currently in use as therapeutic agents in animal models of vascular disease. However, despite substantial data on the ability of viruses to cause vascular inflammation and proliferation, and the presence in current adenovirus vectors of viral open reading frames that are translated in vivo, no study has examined the effect of adenovirus vectors alone on the arterial phenotype. In a rabbit model of gene transfer into a normal artery, we examined potential vascular cell activation, inflammation, and neointimal proliferation resulting from exposure to replication-defective adenovirus. Exposure of normal arteries to adenovirus vectors resulted in: (a) pronounced infiltration of T cells throughout the artery wall; (b) upregulation of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in arterial smooth muscle cells; (c) neointimal hyperplasia. These findings were present both 10 and 30 d after gene transfer, with no evidence of a decline in severity over time. Adenovirus vectors have pleiotropic effects on the arterial wall and cause significant pathology. Interpretation of experimental protocols that use adenovirus vectors to address either biological or therapeutic issues should take these observations into account. These observations should also prompt the design of more inert gene transfer vectors.

Potential gene therapy strategies in the treatment of cardiovascular disease

Gene therapy is the introduction of new genetic material into somatic cells to synthesize missing or defective proteins. Efficient methods for the introduction of genetic material into cells are available, both in vitro and in vivo. These strategies involve chemical, physical, and viral-mediated mechanisms of gene transfer. Application of these gene transfer techniques has led to the development of potential gene-based treatment strategies that could combat vascular and myocardial disease. Gene therapy in the treatment of cardiovascular disease promises to alter atherosclerotic risk factors, prevent vascular thrombotic disease, retard progression of disease in the peripheral vasculature, provide drug delivery systems, and prevent myocardial infarction in patients with coronary artery disease. This exciting technology will eventually become the ultimate intervention in the treatment of cardiovascular disease.

Gene therapy for the vulnerable plaque

Acute coronary events result from the rupture of an atherosclerotic plaque, leading to formation of an occlusive coronary thrombus. Recent developments in the field of gene transfer provide the opportunity to genetically modify cells involved in plaque rupture as well as thrombus formation and thus prevent acute coronary syndromes. A first approach consists of transferring genes, the product of which may stabilize the vulnerable plaque by reducing the plaque content in lipids and macrophages. Alternatively, the introduction into the atherosclerotic plaque of genes encoding for thrombolytic proteins or growth factors able to restore physiologic antithrombotic functions of endothelial cells may inhibit thrombus formation should the plaque rupture. The success of such strategies depends on the efficiency with which the transgene is introduced and expressed into the target cell, the duration of transgene expression and the ability of the transgene product to ultimately prevent plaque rupture or thrombus formation, or both.

Low-efficiency of percutaneous adenovirus-mediated arterial gene transfer in the atherosclerotic rabbit

Recombinant adenoviruses are the most efficient vectors with which to perform arterial gene transfer. Previous in vivo studies of adenovirus-mediated arterial transfection, however, have been performed using normal or endothelium-denuded arteries. It is unclear whether these results can be extended to atherosclerotic arteries. Accordingly, this study was designed to (a) assess the feasibility of adenovirus-mediated gene transfer to atherosclerotic lesions, and (b) compare the transfection efficiency, anatomic distribution of transfected cells, and duration of transgene expression achieved in normal versus atherosclerotic arteries. A recombinant adenovirus including a nuclear-targeted beta-galactosidase gene was percutaneously delivered to the iliac artery of normal (n = 25) and atherosclerotic (n = 25) rabbits. Transgene expression, assessed by morphometric as well as chemiluminescent analyses, was documented in all normal and atherosclerotic arteries between 3 and 14 d after gene transfer, but was undetectable at later time points. Transfected cells were identified as smooth muscle cells located in the media of normal arteries, and in the neointima and the vasa-vasora of atherosclerotic arteries. Two percent of medial cells, but only 0.2% of medial and neointimal cells expressed the transgene in normal and atherosclerotic arteries, respectively (P = 0.0001). Similarly, nuclear beta-galactosidase activity was higher in normal than in atherosclerotic arteries (3.2 vs. 0.8 mU/mg protein, P = 0.02). These findings indicate that atherosclerosis reduces the transfection efficiency which can be achieved with adenoviral vectors, and thus constitutes a potential limitation to adenovirus-based, arterial gene therapy.

Modulation of connexin43 expression: effects on cellular coupling

INTRODUCTION

Gap junctions connect cardiac myocytes allowing propagation of action potentials. They contain intercellular channels formed by multiple different connexin proteins. The arrangement and type of gap junctions and the types, function, and interaction of connexin proteins determine intercellular resistance and can thereby influence conduction velocity and the potential for reentrant arrhythmias. Our goal was to develop genetically manipulable models to test the effects of altering expression of a major cardiac connexin (connexin43) on intercellular coupling and expression of other connexin proteins.

METHODS AND RESULTS

BHK cells that are poorly coupled and BWEM cells that are well coupled were stably transfected with plasmids containing connexin43 cDNA in antisense and sense orientations. RNA blots confirmed expression of the transfected transcripts. Immunoblots showed that connexin43 protein was reduced in the BHK antisense transfectants and increased in the BHK sense transfectants compared to the parental cells. It was not detectably changed in the BWEM antisense transfectant line compared to the BWEM parental cells. Transfection of connexin43 cDNA did not affect production of connexin45 mRNA and protein nor did transfection induce expression of other previously unexpressed connexin mRNAs. Cell coupling was assessed by intercellular diffusion of microinjected Lucifer yellow in confluent cell populations. Lucifer yellow passed to a mean of 3 +/- 3 neighboring parental BHK cells, to 8 +/- 8 neighbors in the sense connexin43 transfected BHK cells, and to only 2 +/- 2 neighbors in the antisense connexin43 transfected BHK cells (P < 0.05). In contrast, dye transfer did not differ significantly between the parental BWEM cells (mean transfer = 19 +/- 14 cells) and the BWEM connexin43 antisense transfectants (mean transfer = 15 +/- 12 cells) (P = 0.20).

CONCLUSIONS

These data demonstrate that stable transfection with connexin43 cDNA constructs can result in detectable changes in connexin43 expression and cellular coupling without inducing compensatory changes in the cell's connexin phenotype and, therefore, may provide a basis for future attempts at specifically modulating connexin expression and intercellular resistance in cardiac tissues.

Prevention of restenosis after coronary angioplasty: towards a molecular approach?

Restenosis after coronary angioplasty, the main limitation of interventional cardiology, remains an unsolved issue. The failure to-date of all pharmacological attempts at prevention has prompted the development of alternative strategies. A mechanistic approach to the problem of restenosis is based on the assumption that creating a more satisfactory acute angioplasty result would reduce the development of restenosis. With the exception of coronary stenting, however, none of the new angioplasty devices have convincingly reached this goal. Furthermore, recent advances in the field of vascular biology have opened new avenues for a molecular approach of restenosis. Better understanding of the pathophysiology of restenosis, in conjunction with high-pace development of catheter, polymer, and virus technologies, provide opportunities to deliver agents--drugs, genes, or antisense oligonucleotides--locally, at the site of angioplasty to interfere specifically with the restenosis process. Some of these molecular strategies are currently being investigated in animal models. Clinical application of a molecular approach to prevent restenosis, however, will require close collaboration between physicians, molecular biologists, and bio-engineers.

Vascular gene therapy

Gene therapy is emerging as a new and exciting therapeutic modality for cardiovascular pathology. The work reported here was carried out in the National Heart, Lung and Blood Institute (NHLBI) in Bethesda, MD, USA, where genetically engineered endothelial cells were used to seed endovascular prostheses and cell adhesion to the prostheses was tested both in vitro and in vivo. Two catheter based systems were used to deliver genes to the arterial wall cells in vivo, employing retroviral and adenoviral vectors. Efficient gene transfer to vascular cells in vivo was achieved with adenoviral vectors.