Percutaneous transluminal in vivo gene transfer by recombinant adenovirus in normal porcine coronary arteries, atherosclerotic arteries, and two models of coronary restenosis

Gene Therapy: A Lipofection Approach for Gene Transfer into Primary Endothelial Cells

Despite the great potential of gene therapy to become a new treatment modality in future medicine, there are still many limitations to overcome before this gene approach can pass to the stage of human trial. The foremost obstacle is the development of a safe, efficient, and efficacious vector system for in vivo gene application. This study evaluated the efficacy of lipofection as a gene delivery vehicle into primary endothelial cells. Transfection efficiency of several lipid-based reagents (Effectene, Fugene 6, DOTAP) was examined at experimental temperatures of 37°C, 24°C, and 6°C. Human umbilical vein endothelial cells (HUVECs) were transfected with the enhanced green fluorescent protein (EGFP) using precise amounts of DNA (Effectene, 0.2 μg; Fugene 6, 0.5 μg; DOTAP, 2.5 μg) and lipids (Effectene, 10 μl; Fugene 6, 6 μl; DOTAP, 15 μl) optimized in our laboratory. Duration of incubation in the DNA/lipid transfection mixture varied for each lipid transfectant as follows: 5 h for both Fugene 6 and DOTAP and 3 h for Effectene. Efficiency of transfection was quantified by microscopic evaluation of EFGP expression in a minimum of 100 cells per group. Transfection efficiencies achieved with these lipofection agents were 34 ± 1.3% (mean ± SEM), 33 ± 1.4%, and 18 ± 1.5% for Effectene, Fugene 6, and DOTAP, respectively, at 37°C. Transfection results were lower at 24°C with mean efficiencies of 26 ± 2.4% for Effectene, 14 ± 2.9% for Fugene 6, and 15 ± 3.2% for DOTAP. Furthermore, mean efficiencies at 6°C were 6 ± 0.5%, 8 ± 1.5%, and 6 ± 0.0% for Effectene, Fugene 6, and DOTAP, respectively. Efficiency of transfection appeared to be temperature dependent (ANOVA; p < 0.0001). In spite of a significant decrease (37°C vs. 24°C: p < 0.0001; 37°C vs. 6°C: p < 0.0001; 24°C vs. 6°C: p < 0.0115) in transfection efficiency at low temperatures, the successful in vitro gene manipulation renders lipofection a potential gene delivery strategy for in vivo gene therapy.

Targeting sarcoplasmic reticulum calcium ATPase by gene therapy

Although pharmacologic therapies have provided gains in reducing the mortality of heart failure, the rising incidence of the disease requires new approaches to combat its health burden. Twenty-five years ago, abnormal calcium cycling was identified as a characteristic of failing human myocardium. Sarcoplasmic reticulum calcium ATPase (SERCA2a), the sarcoplasmic reticulum calcium pump, was found to be a key factor in the alteration of calcium cycling. With the advancement of gene vectors, SERCA2a emerged as an attractive clinical target for gene delivery purposes. Using adeno-associated virus constructs, SERCA2a upregulation has been found to improve myocardial function in animal models. The clinical benefits of overexpressing SERCA2a have been demonstrated in the phase I study Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease (CUPID). This study has demonstrated that a persistent expression of the transgene SERCA2a is associated with a significant improvement in associated biochemical alterations and clinical symptoms of heart failure. In the coming years, additional targets will likely emerge that are amenable to genetic manipulations along with the development of more advanced vector systems with safer delivery approaches.

Gene targeting in ischemic heart disease and failure: translational and clinical studies

Alternative and innovative targeted strategies hold relevance in improving the current treatments for ischemic heart disease (IHD). One potential treatment modality, gene targeting, may provide a unique alternative to current IHD therapies. The principal function of gene targeting in IHD is to augment the expression of an endogenous gene through amplification of an exogenous gene, delivered by a plasmid or a viral vector to enhance myocardial perfusion, and limit the long-term sequelae. The initial clinical studies of gene targeting in IHD were focused upon induction of angiogenic factors and the outcomes were equivocal. Nevertheless, significant advancements have been made in viral vectors, mode of delivery, and potentially relevant targets for IHD. Several of these advancements, particularly with a focus on translational large animal studies, are the focus of this review. The development of novel vectors with prolonged transduction efficiency and minimal inflammation, coupled with hybrid perfusion-mapping delivery devices, and improving the safety of vector use and efficacy of gene systems are but a few of the exciting progresses that are likely to proceed to clinical studies in the near future.

Delivery of negatively charged liposomes into the atheromas of Watanabe heritable hyperlipidemic rabbits

Liposomes have been used as imaging and therapeutic agents in various tissues but only infrequently in the cardiovascular system. We prepared a liposome to target atheromas in a Watanabe heritable hyperlipidemic (WHHL) rabbit model. Liposomes labeled with rhodamine and nanogold were injected intra-arterially into the descending thoracic aortas of WHHL rabbits. The arterial segments of interest were perfusion-fixed and evaluated with immunohistochemistry, light microscopy, and electron microscopy. Deconvolution microscopy showed that rhodamine label was concentrated in the plaque shoulder regions of advanced-stage atheromas; however, rhodamine label was not found in adjacent, non-atherosclerotic aorta. Transmission electron microscopy revealed liposome remnants and the highest concentration of nanogold label in lipid-laden areas of atheromas. Liposomes were concentrated in areas of lipoprotein-associated phospholipase A2 expression. We conclude that modified liposomes can be delivered to the shoulder regions of advanced atheromas in WHHL rabbits and may be useful therapeutically for targeting metabolically active plaque.

Vascular targeting: recent advances and therapeutic perspectives

The ability to deliver therapeutics site—specifically in vivo—remains a major challenge for the treatment of malignant, inflammatory, cardiovascular, and degenerative diseases. The need to target agents safely, efficiently, and selectively has become increasingly evident because of progress in vascular targeting. The vascular endothelium is a central target for intervention, given its multiple roles in the physiology (in health) and pathophysiology (in disease) and its direct accessibility to circulating ligands. In cancer, the expression of specific molecules on the surface of vascular endothelial and perivascular cells might enable direct therapeutic targeting. The use of in vivo phage display has significantly contributed to the identification of such targets, which have been successfully used for directed vascular targeting in preclinical animal models. Several animal studies have been performed by using fused molecules between tumor endothelium-directed molecules and immunomodulatory, procoagulant, or cytotoxic molecules. In addition to delivery of therapeutic agents, vascular targeted gene therapies based on both ligand-directed delivery of gene vectors to tumor endothelium and transcriptional targeting have also emerged. In this review, we discuss ligand-directed vascular targeting strategies with an emphasis on recent developments related to phage-display-based screenings.

Transthoracic direct current shock facilitates intramyocardial transfection of naked plasmid DNA infused via coronary vessels in canines

Catheter-mediated, percutaneous, transluminal delivery of naked plasmid DNA (pDNA) into myocardium may offer a valuable strategy to heart diseases. Here, we examined whether clinically available transthoracic direct current (DC) shock improves intracoronary naked DNA transfection into myocardium. Plasmid vector encoding the GL3 luciferase was infused retrogradely into the coronary veins of beagle dogs, whereas another pDNA solution was infused into the left coronary artery. During and after these procedures, the coronary venous sinus was occluded by balloon, and transthoracic DC shock of 200 J was applied immediately after the infusions. Without DC shock, no remarkable increase in luciferase activity was demonstrated in any part of the left ventricular myocardium. In the presence of DC pulsation, significant luciferase expression was detected in the regions that were supplied by left anterior descending coronary artery (LAD), whereas the gene expression in the right coronary artery (RCA) regions was much less drastic. X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactoside) staining of cardiac cross-sections also revealed regional expression of beta-galactosidase. Immunohistochemical examinations of heart cryosections revealed that cardiomyocytes in LAD regions successfully expressed transgene product. The present system may enable a new strategy for myocardial gene therapy, without any special device or technique other than cardiac catheterization and DC cardioversion that are generally performed in ordinary hospitals.

Adeno-associated virus (AAV)-7 and -8 poorly transduce vascular endothelial cells and are sensitive to proteasomal degradation

Transduction of the vascular endothelium by adeno-associated virus (AAV) vectors would have broad appeal for gene therapy. However, levels of transduction by AAV serotype-2 are low, an observation linked to deficiencies in endothelial cell binding, sequestration of virions in the extracellular matrix and/or virion degradation by the proteasome. Strategies to improve transduction of endothelial cells include AAV-2 capsid targeting using small peptides isolated by phage display or the use of alternate serotypes. Previously, we have shown that AAV serotypes-3 through -6 transduce endothelial cells with poor efficiency. Recently, AAV serotypes-7 and -8 have been shown to mediate efficient transduction of the skeletal muscle and liver, respectively, although their infectivity profile for vascular cells has not been addressed. Here, we show that AAV-7 and -8 also transduce endothelial cells with poor efficiency and the levels of transgene expression are markedly enhanced by inhibition of the proteasome. In both cases proteasome blockade enhances the nuclear translocation of virions. We further show that this is vascular cell-type selective since transduction of smooth muscle cells is not sensitive to proteasome inhibition. Analysis in intact blood vessels corroborated these findings and suggests that proteasome degradation is a common limiting factor for endothelial cell transduction by AAV vectors.

Catheter-based antegrade intracoronary viral gene delivery with coronary venous blockade

The purpose of this study is to evaluate the feasibility of percutaneous antegrade myocardial gene transfer (PAMGT). A consistent and safe technique for in vivo gene transfer is required for clinical application of myocardial gene therapy. PAMGT with concomitant coronary venous blockade was performed in 12 swine. The myocardium was preconditioned with 1 min of occlusion of the left anterior descending and left circumflex arteries. The anterior interventricular vein was occluded during left anterior descending artery delivery, and the great cardiac vein at the entrance of the middle cardiac vein was occluded during left circumflex artery delivery. With arterial and venous balloons inflated (3 min) and after adenosine (25 mug) injection, PAMGT was performed by antegrade injection of an adenoviral solution (1 ml of 10(11) plaque-forming units in each coronary artery) carrying beta-galactosidase or saline through the center lumen of the angioplasty balloon. In one set of animals, PAMGT was performed with selective coronary vein blockade (n = 9); in another set of animals, PAMGT was performed without coronary vein blockade (n = 5). At 1 wk after gene delivery, the animals were killed. Quantitative beta-galactosidase analysis was performed in the left and right ventricular walls. PAMGT was successfully performed in all animals with and without concomitant occlusion of the coronary veins. Quantitative beta-galactosidase analysis showed that PAMGT with coronary blockade was superior to PAMGT without coronary blockade. beta-Galactosidase activity increased significantly in the beta-galactosidase group compared with the saline group: 1.34 +/- 0.18 vs. 0.81 +/- 0.1 ng (P </= 0.01) in the left ventricular wall and 0.91 +/- 0.1 vs. 0.66 +/- 0.07 ng (P </= 0.05) in the right ventricular wall. PAMGT with selective coronary venous blockade is feasible, reproducible, and safely achieved in a large-animal model.

Adenosine 5'-monophosphate-activated protein kinase and p38 mitogen-activated protein kinase participate in the stimulation of glucose uptake by dinitrophenol in adult cardiomyocytes

During metabolic stress, such as ischemia or hypoxia, glucose becomes the principal energy source for the heart. It has been shown that increased cardiac glucose uptake during metabolic stress has a protective effect on cell survival and heart function. Despite its physiological importance, only limited data are available on the molecular mechanisms regulating glucose uptake under these conditions. We used 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, as a model to mimic hypoxia and gain insight into the signaling pathway underlying metabolic stress-induced glucose uptake in primary cultures of rat adult cardiomyocytes. The results demonstrate that 0.1 mM DNP induces 2.2- and 9-fold increases in AMP-activated protein kinase (AMPK) and p38 MAPK phosphorylation, respectively. This is associated with a 2.3-fold increase in glucose uptake in these cells. To further delineate the role of AMPK in the regulation of glucose uptake, we used two complementary approaches: pharmacological inhibition of the enzyme with adenine 9-beta-D arabinofuranoside and adenoviral infection with a dominant-negative AMPK (DN-AMPK) mutant. Our results show that overexpression of DN-AMPK completely suppressed DNP-mediated phosphorylation of acetyl coenzyme A carboxylase, a downstream target of AMPK. Inhibition of AMPK with either 9-beta-D arabinofuranoside or DN-AMPK also abolished DNP-mediated p38 MAPK phosphorylation. Importantly, AMPK inhibition only partially decreased DNP-stimulated glucose uptake in cardiomyocytes. Inhibition of p38 MAPK with the pharmacological agent PD169316 also partially reduced (70%) glucose uptake in response to DNP. In conclusion, our results indicate that p38 MAPK acts downstream of AMPK in cardiomyocytes and that activation of the AMPK/p38 MAPK signaling cascade is essential for maximal stimulation of glucose uptake in response to DNP in adult cardiomyocytes.

Cell-selective viral gene delivery vectors for the vasculature

Clinical gene therapy for cardiovascular disease remains achievable. To date, however, preclinical studies and clinical trials have highlighted shortfalls in viral gene delivery to vascular cells. These include poor efficiency, poor target tissue selectivity, the presence of pre-existing neutralizing antibodies and immunogenicity generated by the host to vectors such as adenovirus. These important issues require careful consideration when applying viral vectors for gene therapy. Each delivery vector requires precise optimization and tailoring for each disease application since parameters relating to vector : tissue exposure time, route of delivery and target cell type vary considerably. Optimization can be achieved through modification of the structure of the virus capsid proteins and expression cassette to generate vectors that are highly selective and efficient for target cell binding and entry as well as instilling transcriptional control and/or longevity on transgene expression. This ultimately will improve the efficacy and toxicity profiles of gene delivery vectors and has become a very important area in gene therapy. Here, we review recent advances in the targeting of viral gene delivery vectors to the vasculature.

Gene expression profiling of E2F-1-induced apoptosis

It has been shown that adenovirus-mediated overexpression of E2F-1 can efficiently induce apoptosis in cancer cells with little effect on normal cells. However, the mechanisms by which E2F-1 induces apoptosis remains poorly understood. The goal of this study was to evaluate changes in gene expression in response to E2F-1 in order to help elucidate the mechanisms by which E2F-1 causes apoptosis. Therefore, we used a quantitative microarray assay to identify the genes regulated by E2F-1 in melanoma cells. By gene expression profiling, we first screened a proprietary list of about 12,000 genes. Overexpression of E2F-1 in melanoma cells resulted in two-fold or greater alteration in the level of expression of 452 genes compared to vehicle-treated control cells. Most of the affected genes were not known to be responsive to E2F-1 prior to this study. E2F-1 adenoviral infection of these cells was found to affect the expression of a diverse range of genes, including oncogenes, transcription factors and genes involved in signal transduction, cell cycle regulation, cell proliferation and apoptosis, as well as other genes with unknown function. Changes in expression of 17 of these genes were confirmed by quantitative real-time polymerase chain reaction (PCR). This is first application of the microarray technique in the study of the global profile of genes regulated by E2F-1 in melanoma cells. This study leads to an increased understanding of the biochemical pathways involved in E2F-1-induced apoptosis and possibly to the identification of new therapeutic targets.

Current concepts and applications of coronary venous retroinfusion

Retroinfusion of the coronary veins has gained attention for therapeutic approaches which target drugs, genes or cells to ischemic myocardium. Besides anatomy of the coronary venous system, the pressure flow relationship during retroinfusion and the efficacy of pressure-regulated selective retroinfusion for targeted delivery of drugs is reported. Moreover, we describe adenoviral and liposomal gene transfer into ischemic and nonischemic myocardium, outline studies in chronic ischemic preclinical models treated by retroinfusion of pro-angiogenic agents and discuss the impact of retroinfusion for cell-based regenerative therapy of the diseased myocardium.

Designing gene delivery vectors for cardiovascular gene therapy

Genetic therapy in the cardiovascular system has been proposed for a variety of diseases ranging from prevention of vein graft failure to hypertension. Such diversity in pathogenesis requires the delivery of therapeutic genes to diverse cell types in vivo for varying lengths of time if efficient clinical therapies are to be developed. Data from extensive preclinical studies have been compiled and a certain areas have seen translation into large-scale clinical trials, with some encouraging reports. It is clear that progress within a number of disease areas is limited by a lack of suitable gene delivery vector systems through which to deliver therapeutic genes to the target site in an efficient, non-toxic manner. In general, currently available systems, including non-viral systems and viral vectors such as adenovirus (Ad) or adeno-associated virus (AAV), have a propensity to transduce non-vascular tissue with greater ease than vascular cells thereby limiting their application in cardiovascular disease. This problem has led to the development and testing of improved vector systems for cardiovascular gene delivery. Traditional viral and non-viral systems are being engineered to increase their efficiency of vascular cell transduction and diminish their affinity for other cell types through manipulation of vector:cell binding and the use of cell-selective promoters. It is envisaged that future use of such technology will substantially increase the efficacy of cardiovascular gene therapy.

Targeting neuronal nitric oxide synthase with gene transfer to modulate cardiac autonomic function

Microdomains of neuronal nitric oxide synthase (nNOS) are spatially localised within both autonomic neurons innervating the heart and post-junctional myocytes. This review examines the use of gene transfer to investigate the role of nNOS in cardiac autonomic control. Furthermore, it explores techniques that may be used to improve upon gene delivery to the cardiac autonomic nervous system, potentially allowing more specific delivery of genes to the target neurons/myocytes. This may involve modification of the tropism of the adenoviral vector, or the use of alternative viral and non-viral gene delivery mechanisms to minimise potential immune responses in the host. Here we show that adenoviral vectors provide an efficient method of gene delivery to cardiac-neural tissue. Functionally, adenovirus-nNOS can increase cardiac vagal responsiveness by facilitating cholinergic neurotransmission and decrease beta-adrenergic excitability. Whether gene transfer remains the preferred strategy for targeting cardiac autonomic impairment will depend on site-specific promoters eliciting sustained gene expression that results in restoration of physiological function.

GATA-4 is a nuclear mediator of mechanical stretch-activated hypertrophic program

In overloaded heart the cardiomyocytes adapt to increased mechanical and neurohumoral stress by activation of hypertrophic program, resulting in morphological changes of individual cells and specific changes in gene expression. Accumulating evidence suggests an important role for the zinc finger transcription factor GATA-4 in hypertrophic agonist-induced cardiac hypertrophy. However, its role in stretch-induced cardiomyocyte hypertrophy is not known. We employed an in vitro mechanical stretch model of cultured cardiomyocytes and used rat B-type natriuretic peptide promoter as stretch-sensitive reporter gene. Stretch transiently increased GATA-4 DNA binding activity and transcript levels, which was followed by increases in the expression of B-type natriuretic peptide as well as atrial natriuretic peptide and skeletal alpha-actin genes. The stretch inducibility mapped primarily to the proximal 520 bp of the B-type natriuretic peptide promoter. Mutational studies showed that the tandem GATA consensus sites of the proximal promoter in combination with an Nkx-2.5 binding element are critical for stretch-activated B-type natriuretic peptide transcription. Inhibition of GATA-4 protein production by adenovirus-mediated transfer of GATA-4 antisense cDNA blocked stretch-induced increases in B-type natriuretic peptide transcript levels and the sarcomere reorganization. The proportion of myocytes with assembled sarcomeres in control adenovirus-infected cultures increased from 14 to 59% in response to stretch, whereas the values for GATA-4 antisense-treated cells were 6 and 13%, respectively. These results show that activation of GATA-4, in cooperation with a factor binding on Nkx-2.5 binding element, is essential for mechanical stretch-induced cardiomyocyte hypertrophy.

Emerging therapeutic targets in chronic heart failure: part II

Chronic heart failure is characterised by functional deficiencies of the myocardium. Structural abnormalities of the left ventricular wall occur in many cases as a consequence of myocardial infarction (MI). The overburdened postMI heart is characterised by an active reorganisation of the remaining myocardium. Increased expression and activity of matrix metalloproteinases lead to altered composition and arrangement of the extracellular matrix, which is accompanied by eccentric hypertrophy of cardiomyocytes. The altered geometry of the heart muscle fosters biomechanical stress, driving the heart into a dead-end situation. Clearly, novel therapeutic concepts must be developed to reverse this process. Part II of the current review will focus on emerging therapeutic targets for small molecule therapeutics in the fields of cardiac remodelling and impaired survival of cardiomyocytes in the diseased heart. Finally, innovative therapeutic concepts for heart gene therapy and replacement options for destroyed post-MI myocardium using embryonic and adult stem cells are described.

Gene transfer to arteries

This unit provides a set of protocols for introducing recombinant genes into normal, injured, and atherosclerotic arteries. The protocols include animal preparation, surgical techniques, and delivery systems. Protocols describe gene delivery to normal, injured, and stented porcine iliofemoral arteries, employing a double balloon infusion catheter to deliver the vector. Another basic protocol describes gene delivery to atherosclerotic arteries using a hyperlipidemic double-injury rabbit model, and requires surgical exposure of the artery and instillation of the gene vector via a catheter. Additional protocols describe gene delivery to normal and injured murine carotid and femoral arteries. An Alternate Protocol describes a percutaneous method for arterial gene delivery. These protocols may be adapted to deliver genes to either injured or noninjured atherosclerotic arteries.

Nonviral gene transfer strategies for the vasculature

Major attention has been focused on the development of gene therapy approaches for the treatment of vascular diseases. In this review, we focus on an alternative use of gene therapy: the use of genetic means to study vascular cell biology and physiology. Both viral and nonviral gene transfer strategies have limitations, but because of the overwhelming inflammatory responses associated with the use of viral vectors, nonviral gene transfer methods are likely to be used more abundantly for future applications in the vasculature. Researchers have made great strides in the advancement of gene delivery to the vasculature in vivo. However, the efficiency of gene transfer seen with most nonviral approaches has been exceedingly low. We discuss how to circumvent and take advantage of a number of the barriers that limit efficient gene delivery to the vasculature to achieve high-level gene expression in appropriate cell types within the vessel wall. With such levels of expression, gene transfer offers the ability to alter pathways at the molecular level by genetically modulating the activity of a gene product, thus obviating the need to rely on pharmacological agents and their foreseen and unforeseen side effects. This genetic ability to alter distinct gene products within a signaling or biosynthetic pathway or to alter structural interactions within and between cells is extremely useful and technologically possible today. Hopefully, with the availability of these tools, new advances in cardiovascular physiology will emerge.

Enhancement of Fas ligand-induced inhibition of neointimal formation in rabbit femoral and iliac arteries by coexpression of p35

Adenovirus-mediated gene transfer of Fas ligand (FasL) inhibits neointimal formation in balloon-injured rat carotid arteries. Vascular smooth muscle (VSM) cells coexpressing murine FasL and p35, a baculovirus gene that inhibits caspase activity, are not susceptible to FasL-mediated apoptosis in vitro but are capable of inducing apoptosis of VSM cells that do not express p35. We reasoned that coexpression of p35 in FasL-transduced VSM cells in vivo would promote their survival, enhance FasL-induced apoptosis of adjacent VSM cells, and thereby facilitate a greater inhibition of neointimal formation. In balloon-injured rabbit femoral arteries, either Ad2/FasL/p35 or Ad2/FasL was infused into the injured site and withdrawn 20 min later. Both vectors induced a dose-dependent reduction (p < 0.05) of the neointima-to-media ratio when assessed 14 days later. However, Ad2/FasL/p35 exhibited a significantly greater inhibition of neointimal formation than Ad2/FasL. In a more clinically relevant model of restenosis, rabbit iliac arteries were injured with an angioplasty catheter under fluoroscopic guidance. Adenoviral vectors were delivered locally to the injured site over a period of 2 min, using a porous infusion balloon catheter. Twenty-eight days after gene transfer angiographic and histologic assessments indicated a significant (p < 0.05) inhibition of iliac artery lumen stenosis and neointimal formation by Ad2/FasL/p35 (5 x 10(11) particles per artery). The extent of inhibition was comparable to that achieved with Ad2/TK, an adenoviral vector encoding thymidine kinase (5 x 10(11) particles per artery) and coadministration of ganciclovir for 7 days. These data suggest that coexpression of p35 in FasL-transduced VSM cells is more potent at inhibiting neointimal formation and as such represents an improved gene therapy approach for restenosis.

Tissue-specific GATA factors are transcriptional effectors of the small GTPase RhoA

Rho-like GTPases play a pivotal role in the orchestration of changes in the actin cytoskeleton in response to receptor stimulation, and have been implicated in transcriptional activation, cell growth regulation, and oncogenic transformation. Recently, a role for RhoA in the regulation of cardiac contractility and hypertrophic cardiomyocyte growth has been suggested but the mechanisms underlying RhoA function in the heart remain undefined. We now report that transcription factor GATA-4, a key regulator of cardiac genes, is a nuclear mediator of RhoA signaling and is involved in the control of sarcomere assembly in cardiomyocytes. Both RhoA and GATA-4 are essential for sarcomeric reorganization in response to hypertrophic growth stimuli and overexpression of either protein is sufficient to induce sarcomeric reorganization. Consistent with convergence of RhoA and GATA signaling, RhoA potentiates the transcriptional activity of GATA-4 via a p38 MAPK-dependent pathway that phosphorylates GATA-4 activation domains and GATA binding sites mediate RhoA activation of target cardiac promoters. Moreover, a dominant-negative GATA-4 protein abolishes RhoA-induced sarcomere reorganization. The identification of transcription factor GATA-4 as a RhoA mediator in sarcomere reorganization and cardiac gene regulation provides a link between RhoA effects on transcription and cell remodeling.

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.

Novel molecular therapeutic approach to cardiovascular disease based on hepatocyte growth factor

Gene therapy techniques are being developed as potential treatments for cardiovascular diseases. During the past decade, many gene transfer methods including viral transfer techniques have been developed, and some are being applied clinically in human gene therapy studies. Recently, we have developed a novel gene transfer method mediated by Hemagglutinating Virus of Japan (HVJ) liposome, with which we have already reported several cases of successful gene transfer in vivo. Since the virus is inactivated by ultraviolet light, there is little potential for biological hazard with this method as compared to other viral gene transfer approaches. We also developed a novel strategy of gene therapy for cardiovascular diseases utilizing hepatocyte growth factor (HGF) which is an endothelial cell specific growth factor and an angiogenic growth factor. Based on these facts, we hypothesized that HGF may prevent restenosis after angioplasty through re endothelialization and myocardial infarction through induction of angiogenesis. The present results provide evidence of the efficacy of supplemental therapy with HGF by gene transfer in cardiovascular diseases. These data suggest the efficacy of novel molecular therapeutic approaches as gene therapy for cardiovascular diseases such as restenosis and myocardial infarction.

Inhibition of neointimal formation in porcine coronary artery by a Ras mutant

BACKGROUND

Therapeutic approaches to reduce the neointimal formation caused by balloon injury have been focused mainly on experimental models of restenosis in the rat carotid artery. However, restenosis in rat carotid artery may not replicate the coronary arterial responses to injury in larger animals and humans.

METHODS

In this study, we used pig coronary arteries as an animal model to evaluate the preventive effects of a virus-mediated dominant negative mutant RasN17 on balloon injury-induced restenosis. The viral particles were delivered to the balloon-injured coronary arteries via a dispatch catheter to keep the virus in a confined arterial segment for 10 min to reach optimal transfection. Six weeks after balloon injury, the pigs were sacrificed and the left anterior descending arteries were isolated for histological analysis.

RESULTS

Neointima formation was prominent in the group receiving balloon injury as compared with the uninjured controls. A remodeling process with migration of collagen was also found in the injured coronary arteries. The application of AdRasN17 led to a 56% decrease in neointima formation and a 75% increase in lumen size, as compared with the balloon-injured vessels treated with AdLacZ control.

CONCLUSIONS

These results suggest that AdRasN17 is an effective therapeutic gene in preventing balloon injury-induced neointimal formation in pig coronary arteries.

Additive effect of adenovirus-mediated E2F-1 gene transfer and topoisomerase II inhibitors on apoptosis in human osteosarcoma cells

Recently, it has been demonstrated that Etoposide, a topoisomerase II inhibitor, can induce apoptosis in MDM2-overexpressing tumor cells by inhibition of MDM2 synthesis. We have previously shown that E2F-1 overexpression induces apoptosis of MDM2-overexpressing sarcoma cells, which is related to the inhibition of MDM2 expression. Therefore, the present study was designed to investigate the in vitro and in vivo effect of combined treatment of adenovirus-mediated E2F-1 and topoisomerase II inhibitors on the growth inhibition and apoptosis in human sarcoma cells. Two human sarcoma cell lines, OsACL and U2OS, were treated with topoisomerase II inhibitors (Etoposide and Adriamycin), alone or in combination with adenoviral vectors expressing beta-galactosidase (Ad-LacZ) or E2F-1 (Ad-E2F-1). E2F-1 expression was confirmed by Western blot analysis. Ad-E2F-1 gene transfer at a low dose (multiplicity of infection, 2) markedly increased the sensitivity of human sarcoma cells to topoisomerase II inhibitor treatment. This cooperative effect of E2F-1 and topoisomerase II inhibitors was less marked in SAOS-2 cells (p53 and pRb null). Topoisomerase II inhibitors also cooperated with E2F-1 overexpression to enhance tumor cell killing in an in vivo model using xenografts in nude mice. When combined with Adriamycin or Etoposide, E2F-1 adenovirus therapy resulted in approximately 95% and 85% decrease in tumor size, respectively, compared to controls (P<.05). These results suggest a new chemosensitization strategy that is effective in MDM2-overexpressing tumors and may have clinical utility.

Adventitial versus intimal liposome-mediated ex vivo transfection of canine saphenous vein grafts with endothelial nitric oxide synthase gene

PURPOSE

Experiments were designed (1) to evaluate liposome-mediated endothelial constitutive nitric oxide synthase (ecNOS) transfection in vein grafts and (2) to compare intimal and adventitial routes of transfection.

METHODS

Male mongrel dogs (N = 36) underwent bilateral femoral artery bypass grafting with the lateral saphenous vein. In each animal one vein was transfected with plasmid (pVR1012) containing the ecNOS gene, and another vein was transfected with plasmid alone (control). Gene transfer was performed from either the intimal surface (Group I, n = 18) or the adventitial surface (Group II, n = 18). In each group there were three transfection subgroups (n = 6 each): (a ) 10 microg/mL naked plasmid DNA, (b ) 10 microg/mL plasmid DNA + liposome (LipofectAMINE PLUS), and (c ) 100 microg/mL plasmid DNA + LipofectAMINE PLUS. Grafts were harvested on the third postoperative day, and the transfection was assessed with molecular techniques and enzyme assay for activity of NOS by conversion of tritiated l-arginine to tritiated l-citrulline. Proliferating cells were quantified with a digital analysis of histologic sections after nuclear antigen Ki-67 (MIB1) immunohistochemistry.

RESULTS

Transgene was identified with polymerase chain reaction in all ecNOS-transfected grafts, regardless of transfection modality. However, significant transcription of the ecNOS transgene was observed only in Group IIc (mean ecNOS messenger RNA, 8.7+/-1.7 vs. 3.1+/-0.7 x 10(-2) attomole/microL, in transfected compared with control grafts, respectively, P =.01). NOS activity increased approximately twofold in this group (11.58+/-2.1 and 6.3+/-1.0 pmol tritiated l-citrulline per milligram protein per hour in transfected and control grafts, respectively, P = .05). Numbers of proliferating cells did not differ among ecNOS-transfected and control grafts in any transfection group.

CONCLUSION

These results suggest that ecNOS transfection of vein grafts is feasible through intimal and adventitial routes with naked DNA or a liposomal vector. However, efficient transcription of the transgene is evident at postoperative day 3 only after adventitial transfection of 100 microg/mL of the gene.

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.

Catheter-delivered in vivo gene transfer into rat myocardium using the fusigenic liposomal mediated method

We compared the efficacy of four different in vivo hemagglutinating virus of Japan (HVJ)-liposome gene transfer methods, i.e., direct myocardial injection (i.m.), injection into the left ventricular cavity (LV), infusion at the level of the coronary cusps (CI), or injection into the left ventricular cavity with a balloon catheter blocking aortic flow (LV+B) to transfer beta-galactosidase, FlTC-labeled oligodeoxynucleotide (ODN), and/or luciferase genes into the rat heart. I.m. caused highly efficient gene transfer in the limited area around the injection site, which suggests that i.m. may be a suitable method for targeted treatment of focal lesion. In the LV+B group, all rats had myocardial beta-galactosidase staining and fluorescence of FITC-labeled ODN in the nuclei of cardiac myocytes around the coronary arteries and the vasa vasorum, and some transfected myocytes were observed in the middle of the myocardium without any evidence of injury. In contrast, in the CI group, only half of the animals had myocardial expression of beta-galactosidase. In contrast, fluorescence or luciferase activity was present throughout the left ventricle in the LV+B group. However, the percentage of myocytes that exhibited fluorescence was less than 1% of the total ventricular myocyte population and luciferase activity in the LV+B group was 1.6% of that in the i.m. group. No evidence of luciferase expression was observed in brain, lung, liver, kidney, or testis in either the i.m. or LV+B group. These results suggest that HVJ-liposome gene transfer into the myocardium through the coronary arteries using a balloon-catheter technique is safe and has the potential for causing widespread transgene expression with organ-specificity, although the efficiency of gene transfer should be improved.

Effect of percutaneous adenovirus-mediated Gax gene delivery to the arterial wall in double-injured atheromatous stented rabbit iliac arteries

Though the efficacy of intravascular gene transfer has been demonstrated in native vessels following acute injury, this methodology has not been validated in complex models of vascular injury that more closely mimic clinical angioplasty procedures. Previous studies have shown that Gax gene overexpression modulates the injury-induced remodeling of the vessel in rat carotid and normal rabbit iliac arteries. Here, we evaluated the effect of the Gax gene delivery in atheromatous stented vessels. Rabbits were fed 120 g daily of 1% cholesterol diet for 3 weeks. At 1 week they underwent initial injury on the external iliac artery, then balloon angioplasty was performed at 3 weeks at the same site with a 2.5 mm diameter channel balloon catheter (three times 1 min at 6 atm). Either saline (n = 4) or the control viral construct Ad-CMVluc (5 x 109 p.f.u.) (n = 5) or Ad-CMVGax (5 x 10(9) p.f.u.) (n = 4) was delivered with a poloxamer mixture via a channel balloon (6 atm, 30 min), and a 15 mm long Palmaz-Schatz stent (PS154) was then deployed at the site (1 min, 8 atm). Arteries were analyzed 1 month later. At 1 month, the Ad-CMVGax treated arteries exhibited a lower maximal intimal area (1. 15+/-0.1 mm2) than saline (1.87+/-0.15 mm2, P = 0.007) or Ad-CMVluc-treated vessels (1.98+/-0.31 mm2, P = 0.04). Likewise Ad-CMVGax-treated vessels displayed a lower maximal percentage cross-sectional area narrowing (35.1+/-3.5%) than saline (65.3+/-9.4%, P = 0.01) or Ad-CMVluc-treated vessels (62.7+/-6.7%, P = 0.02). Angiographic analysis revealed larger minimal lumen diameter in Ad-CMVGax treated arteries (2.0+/-0.1 mm) than saline (1.14+/-0.36 mm, P = 0.06) or Ad-CMVluc-treated vessels (1.23+/-0.25 mm, P = 0.02). Overexpression of the Gax gene inhibits neointimal hyperplasia and lumen loss in atheromatous stented rabbit iliac arteries.

Prospects for intravascular gene therapy

The goal of this review is to provide an overview of gene delivery systems and candidate genes currently being evaluated for genetic strategies in vascular gene therapy. We will discuss treatment strategies that have been shown by in vivo model systems to be efficacious in promoting neovascularization of ischemic tissue or limiting post-interventional restenosis by inhibiting smooth muscle cell proliferation and/or encouraging re-endothelialization.

Local adenovirus-mediated transfer of C-type natriuretic peptide suppresses vascular remodeling in porcine coronary arteries in vivo

OBJECTIVE

This study was designed to examine whether or not adenovirus-mediated gene transfer of C-type natriuretic peptide (CNP) can prevent coronary restenotic changes after balloon injury in pigs in vivo.

BACKGROUND

Gene therapy to prevent restenosis after percutaneous transluminal coronary angioplasty (PTCA) might be useful but requires a method applicable for in vivo gene delivery into the coronary artery as well as the efficient vector encoding a potent antiproliferative substance. We tested whether the adenovirus-mediated gene transfer of CNP by use of an infiltrator angioplasty balloon catheter (IABC) might prevent the coronary restenotic changes after balloon injury.

METHODS

Balloon angioplasty was performed in the left anterior descending and the left circumflex coronary artery in pigs. Immediately after the balloon injury, adenovirus solution encoding either CNP (AdCACNP) or beta-galactosidase (AdCALacZ) gene was injected with IABC into the balloon-injured coronary segments. Expression of CNP was assessed by immunohistochemical staining and cyclic guanosine 3',5'-monophosphate (cGMP) measurement. Coronary restenotic changes were evaluated by both angiographic and histological examinations.

RESULTS

CNP was highly expressed in the media and the adventitia of the coronary artery at the AdCACNP-transfected but not at the AdCALacZ-transfected segment. In the AdCALacZ-transfected segment, vascular cGMP levels tended to be reduced as compared with the untreated segment, whereas in the AdCACNP-transfected segment, vascular cGMP levels were restored. Angiographic coronary stenosis was significantly less at the AdCACNP-transfected than at the AdCALacZ-transfected segment. Histological examination revealed that this was achieved primarily by the marked inhibition of the geometric remodeling of the coronary artery by the CNP gene transfer.

CONCLUSIONS

Adenovirus-mediated CNP gene transfer with the IABC system may be a useful gene therapy to prevent restenosis after PTCA in vivo.

Myocardial gene transfer by selective pressure-regulated retroinfusion of coronary veins

Catheter-based percutaneous transluminal gene delivery (PTGD) into the coronary artery still falls behind the expectations of an efficient myocardial gene delivery system. In this study gene delivery was applied by selective pressure-regulated retroinfusion through the coronary veins to prolong adhesion of replication defective adenovirus within the targeted myocardium. Adenoviral vectors consisted either of luciferase (Ad.rsv-Luc) or beta-galactosidase (Ad.rsv-betaGal) reporter gene under control of an unspecific promotor derived from the Rous sarcoma virus (RSV). In this pig model, selective retrograde gene delivery into the anterior cardiac vein during a brief period of ischemia substantially increased reporter gene expression in the targeted myocardium (LAD region) compared with antegrade delivery as a control. Repeated retrograde delivery during two periods of brief ischemia resulted in a more homogeneous transmural expression predominantly observed in cardiomyocytes (X-gal-staining). In the nontargeted myocardium (CX region) there was no evidence for adenoviral transfection. From our data we infer that selective pressure-regulated retroinfusion is a promising approach for efficient percutaneous transluminal gene delivery to the myocardium. Gene Therapy (2000) 7, 232-240.

Adenovirus-mediated E2F-1 gene transfer efficiently induces apoptosis in melanoma cells

BACKGROUND

E2F-1 is a transcription factor that stimulates cellular proliferation and cell cycle progression from G(1) to S-phase. Somewhat paradoxically, E2F-1 also has the properties of a tumor suppressor. Overexpression of E2F-1 has been shown to induce apoptosis in some cancer cells. In the current study, the effect of adenovirus-mediated E2F-1 gene transfer on human melanoma cell growth was investigated.

METHODS

Two human melanoma cell lines, SK-MEL-28 (wild-type p53) and SK-MEL-2 (mutant p53), were treated by mock infection, infection with a control vector expressing the beta-galactosidase gene (Ad5CMV-LacZ), or infection with a vector expressing E2F-1 (Ad5CMV-E2F-1) at a multiplicity of infection of 100. Cell proliferation and viability were determined by WST-1 assay and trypan blue exclusion, respectively. Apoptosis was assessed by cell flow cytometry and confirmed by cell morphology, in situ terminal deoxynucleotidyl nick end labeling assay, and poly(ADP-ribose) polymerase cleavage assay.

RESULTS

Marked overexpression of E2F-1 was evident in both cell lines 24 hours after infection with Ad5CMVE2F-1 by Western blot analysis. E2F-1 overexpression resulted in growth inhibition and rapid loss of cell viability. Overexpression of E2F-1 also resulted in premature S-phase entry and G(2) arrest at 24 hours followed by apoptotic cell death at 48 hours. After Ad5CMVE2F-1 infection, expression of Bax and Bak was unchanged, whereas Mcl-1 levels decreased markedly. In SK-MEL-28 cells, Bcl-XL levels also declined after E2F-1 expression. Bcl-2 was undetectable in SK-MEL-28 cells but was increased in SK-MEL-2 cells in response to E2F-1 overexpression.

CONCLUSIONS

Adenovirus-mediated E2F-1 gene transfer efficiently induces widespread apoptosis in human melanoma cells. E2F-1 overexpression induced apoptosis in cell lines containing wild-type and mutant p53, suggesting that this effect does not require wild-type p53 function. Anti-apoptotic proteins of the Bcl-2 family, notably Mcl-1 and Bcl-XL, may be involved in mediating the response to E2F-1. These data suggest that adenovirus-mediated E2F-1 gene therapy may be effective in the treatment of melanoma.

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.

Cooperative interaction between GATA-4 and GATA-6 regulates myocardial gene expression

Two members of the GATA family of transcription factors, GATA-4 and GATA-6, are expressed in the developing and postnatal myocardium and are equally potent transactivators of several cardiac promoters. However, several in vitro and in vivo lines of evidence suggest distinct roles for the two factors in the heart. Since identification of the endogenous downstream targets of GATA factors would greatly help to elucidate their exact functions, we have developed an adenovirus-mediated antisense strategy to specifically inhibit GATA-4 and GATA-6 protein production in postnatal cardiomyocytes. Expression of several endogenous cardiac genes was significantly down-regulated in cells lacking GATA-4 or GATA-6, indicating that these factors are required for the maintenance of the cardiac genetic program. Interestingly, transcription of some genes like the alpha- and beta-myosin heavy-chain (alpha- and beta-MHC) genes was preferentially regulated by GATA-4 due, in part, to higher affinity of GATA-4 for their promoter GATA element. However, transcription of several other genes, including the atrial natriuretic factor and B-type natriuretic peptide (ANF and BNP) genes, was similarly down-regulated in cardiomyocytes lacking one or both GATA factors, suggesting that GATA-4 and GATA-6 could act through the same transcriptional pathway. Consistent with this, GATA-4 and GATA-6 were found to colocalize in postnatal cardiomyocytes and to interact functionally and physically to provide cooperative activation of the ANF and BNP promoters. The results identify for the first time bona fide in vivo targets for GATA-4 and GATA-6 in the myocardium. The data also show that GATA factors act in concert to regulate distinct subsets of genes, suggesting that combinatorial interactions among GATA factors may differentially control various cellular processes.

Percutaneous adenoviral gene transfer into porcine coronary arteries: is catheter-based gene delivery adapted to coronary circulation?

Recombinant adenoviral (Ad) vectors represent an efficient gene transfer system for targeting the cardiovascular system. Phenotypic modulation of coronary vascular cells in vivo is, however, critically dependent on the efficacy of local delivery devices. Four local drug delivery catheters were tested for intracoronary gene transfer efficiency: the Infiltrator (INF, n = 10), the Crescendo (CRE, n = 10), the Infusasleeve (SLE, n = 8), and the Remedy balloon (channel balloon [CHA], n = 8). After balloon injury of the LAD, Ad vector containing the firefly luciferase cDNA (AdCMVluc, 1.5 x 10(10) plaque-forming units) was administered at the site of injury. On day 4, tissue samples from different regions in the heart and from the liver were assayed for luciferase activity to evaluate local and systemic gene transfer. INF, CRE, and SLE catheters showed higher transduction levels of the target LAD segment than did the CHA catheter (median luciferase activity = 4.2 x 10(6), 11 x 10(6), and 1.3 x 10(6) light units [LU]/vessel versus 0.09 x 10(6) LU/vessel, respectively, p < 0.05). Luciferase activity was occasionally observed in nontarget tissues (right and left ventricular free wall, distal LAD, and liver) and was not significantly different between groups. The viral circulatory half-life was similar for the four groups (<1 min). Gene transfer efficiency was positively correlated with the degree of injury for the intralumenal catheters (CRE, SLE, and CHA) but was independent of the vessel wall injury for the intramural INF. Local drug delivery catheters enable efficient vascular gene transfer in balloon-injured coronary arteries, a prerequisite for further development of intracoronary gene therapy for restenosis.

Early cell loss after angioplasty results in a disproportionate decrease in percutaneous gene transfer to the vessel wall

Acute cell loss has been documented following angioplasty of normal rat and rabbit arteries. Here we analyzed the effects of balloon injury intensity on early cellular loss in single- and double-injury models and how it influences the efficiency of percutaneous gene delivery to the vessel wall. Rabbits underwent bilateral iliac angioplasties (n = 52) with 2.5-mm (balloon-to-artery [B/A] ratio, 1.08 to 1.13) and 3.0-mm (B/A ratio, 1.29 to 1.34) balloons. In the single-injury model, the 3.0-mm balloon induced a 61% reduction in medial cellularity at 3 days postinjury (p < 0.001) while the 2.5-mm balloon did not produce significant cell loss. In the double-injury model, the effects were more pronounced, with 35% (p < 0.01) and 91% (p < 0.001) reductions in medial cellularity at 3 days with the 2.5- and 3.0-mm balloons, respectively, but neointimal cellularity was decreased only with the 3.0-mm balloon (37% reduction, p = 0.025). Adenovirus-mediated beta-galactosidase gene delivery with a channel balloon (n = 24) revealed that larger balloon-to-artery ratios decreased both absolute levels and relative frequencies of transgene expression in the vessel wall. In the single-injury model, gene transfer efficiency was 4.2+/-1.1 and 1.3+/-0.25% (p < 0.05) for the small and large balloons, respectively. In the double-injury model, gene transfer efficiency was 6.6+/-1.6 and 2.3+/-0.8% (p < 0.05) in the neointima and 4.1+/-1.2 and 2.6+/-1.2% (p = NS) in the media for the small and large balloon, respectively. We conclude that early cell loss is dependent on the intensity of the injury in both single- and double-injury models of balloon angioplasty, with greater frequencies of cell loss occurring in the media than in the neointima. In both models, larger balloon-to-artery ratios result in disproportionate reductions in percutaneous adenovirus-mediated gene delivery.

Gene therapy for cerebrovascular disease

OBJECTIVE

To review the principles of and the experimental and clinical results of gene therapy for cerebrovascular disease.

METHODS

Literature review.

RESULTS

Vectors for gene transfer into the brain or into the cerebral vasculature include naked plasmid deoxyribonucleic acid, cationic liposomes, and viruses such as adenovirus, retrovirus, adeno-associated virus, and herpes simplex virus. Experiments using these vectors showed that intra- or perivascular application to systemic arteries can lead to transfection and expression of a foreign transgene in the adventitia and the endothelium. Intrathecal administration can lead to transfection and foreign transgene expression in leptomeningeal cells as well as in fibroblasts of blood vessel adventitia. Biological effects demonstrated thus far include increased nitric oxide production by transfection of cerebral arterial adventitia with adenovirus expressing nitric oxide synthase. Adenoviruses carrying foreign genes have been used to decrease neuronal damage in cerebral ischemia and to decrease blood pressure in spontaneously hypertensive rats. Vectors and therapeutic applications for gene therapy are evolving rapidly.

CONCLUSION

Gene therapy for cerebrovascular disease is likely to have clinical application in the near future and will have a major impact on neurosurgery. Neurosurgeons will need to be aware of the literature in this area.

Thrombus generation after adenovirus-mediated gene transfer into atherosclerotic arteries

Thrombosis represents a major issue during arterial local delivery. We evaluated the occurrence of thrombosis after adenovirus (Ad)-mediated gene transfer into normal and atherosclerotic arteries. A replication-deficient Ad vector expressing the beta-galactosidase reporter gene (Ad.RSV betagal; 4 x 10(9) PFU) was injected into normal and atherosclerotic arteries (n = 11 in both groups). The contralateral artery received either an Ad vector carrying no transgene (Ad.MLPnull) (n = 7 in both groups, 4 x 10(9) PFU) or vehicle buffer (n = 4 in normal group, n = 8 in atherosclerotic group). Animals were sacrificed 3 days following gene transfer for thrombus detection and assessment of beta-galactosidase activity. Thrombus was absent in normal arteries and in atherosclerotic arteries injected with vehicle buffer only. In contrast, nonocclusive thrombus was present in atherosclerotic arteries injected with either Ad.RSV betagal (5 of 11) or Ad.MLPnull (3 of 7). Beta-galactosidase activity was predominantly found in the endothelial layer of the transfected arteries. Gene transfer and expression occurred despite the presence of the thrombus (4 of 5), and its efficiency did not significantly differ regardless of the thrombus. We conclude that thrombus frequently occurred in atherosclerotic arteries after Ad-mediated gene transfer. Further studies are warranted to identify the mechanisms of thrombus generation after Ad-mediated gene transfer into atherosclerotic arteries.

Gene therapy for tissue repair and regeneration

This review presents a current overview of the discipline of human gene therapy. In addition, a gene therapy method is described in which plasmid genes are transferred from a structural matrix carrier into fresh wound sites so as to enhance tissue repair and regeneration. The potential to develop a gene therapy for bone regeneration is discussed in detail.

Effects of poloxamer 407 on transfection time and percutaneous adenovirus-mediated gene transfer in native and stented vessels

Reduction in transfection time and the ability to perform gene transfer in conjunction with endovascular stent implantation constitute two important challenges for percutaneous adenovirus-mediated gene transfer to vessel walls. Studies have suggested that the use of biocompatible polyol poloxamer 407 could be useful. We first evaluated the use of poloxamer 407 for percutaneous gene transfer in nonstented rabbit iliac arteries. A 200-microl mixture of Ad-RSVbetagal or Ad-CMVLuc in either phosphate-buffered saline (PBS) or 20% poloxamer was delivered. After 3 days, gene transfection was evaluated by X-Gal staining or measurement of luciferase activity. Poloxamer use resulted in a 3- to 15-fold increase in the percentage of transfected cells (X-Gal, p = 0.001) and a 16-fold increase in protein product (luciferase activity, p = 0.03), and allowed a decrease in transfection time from 30 to 5 min with minimal reduction in transfection efficiency. We then evaluated the feasibility of percutaneous gene transfer, using Ad-RSVbetagal diluted in pure PBS or 20% poloxamer, in conjunction with stent implantation. Gene delivery was performed either immediately before (pre-) or after (post-) stent implantation. When adenoviruses were diluted in PBS, gene transfer had a low efficiency (prestent, 0.3%; poststent, 0.2%; NS). With poloxamer, the efficacy was much higher (p = 0.0001) and similar "pre" (2.2%) or "post" (1.7%) stent delivery (NS).

CONCLUSIONS

(1) The use of poloxamer, rather than PBS, as a vehicle increases the efficacy of percutaneous adenovirus-mediated gene transfer and reduces transfection time; (2) gene transfer performed during stent implantation with poloxamer is feasible and achieves a significant level of gene expression. Thus percutaneous gene delivery is applicable to conventional stents and could present an attractive method by which to achieve local biological effects in a stent environment.

Basic fibroblast growth factor regulates extracellular matrix and contractile protein expression independent of proliferation in vascular smooth muscle cells

Basic fibroblast growth factor (bFGF) can influence proliferation and differentiation in vascular smooth muscle cells. Basic FGF promotes some features of the synthetic phenotype (proliferation) but is known to inhibit others (collagen synthesis). Whether bFGF availability influences smooth muscle cell phenotype independent of proliferation is not known. The purpose of this study was to determine if the effects of bFGF on extracellular matrix and contractile protein expression are dependent on changes in proliferation. Basic FGF availability was manipulated by adding bFGF to cultured cells or by inhibiting bFGF expression using antisense RNA, and adjusting culture conditions such that proliferation was held constant. Compared to cells cultured in serum alone, smooth muscle alpha-actin and myosin heavy chain expression was markedly reduced by added bFGF, but was not influenced by antisense inhibition of bFGF expression. Under the same conditions, collagen synthesis was inhibited by added bFGF, and was stimulated by reduced bFGF expression. These consequences of altering bFGF availability were not associated with changes in FGF receptor expression. These findings demonstrate that alterations in bFGF availability can regulate smooth muscle cell phenotype independent of proliferation, which may be related to the regulation of smooth muscle cell phenotype in vivo.

Gene therapy with bilirubin-UDP-glucuronosyltransferase in the Gunn rat model of Crigler-Najjar syndrome type 1

Crigler-Najjar syndrome type 1 (CN type 1) is an autosomal recessive disorder characterized by nonhemolytic jaundice resulting from mutations to the gene encoding bilirubin-UDP-glucuronosyltransferase (UDPGT). The Gunn rat is an accurate animal model of this disease because the bilirubin-UDPGT gene in this strain carries a premature stop codon. The primary objective of this study was to complement this deficiency in vivo using liver-directed gene therapy. The efficiency of adenovirus type 5 (Ad5)-mediated gene transfer to the neonatal rat liver was first assessed by intravenous (i.v.) injection of an Ad5 vector carrying a nuclear-localized LacZ gene. An Ad5 vector expressing the cDNA encoding human bilirubin-UDPGT (Ad5/CMV/hUG-Br1) was then generated and injected i.v. into neonatal Gunn rats. Plasma samples were collected and bilirubin levels were determined at regular intervals. Although the mean level of bilirubin in homozygous Gunn rats 1-2 days after birth was already 14.5-fold higher than that of heterozygous siblings, treatment with Ad5/CMV/hUG-Br1 reduced plasma bilirubin to normal levels within 1 week. Plasma bilirubin in the treated homozygous rats remained normal for 4 weeks before gradually climbing to intermediate levels that were approximately half that of untreated homozygotes by 12 weeks. Administration of Ad5-mediated gene therapy to neonatal Gunn rats effectively complemented the deficiency in bilirubin-UDPGT, resulting in substantial reductions in plasma bilirubin over a 3-month period. The efficacy of Ad5-mediated gene therapy in neonates suggests that this approach might be effective against other hepatic disorders, including autosomal recessive deficiencies in lipid metabolism and vascular homeostasis.

Increased in vitro and in vivo gene transfer by adenovirus vectors containing chimeric fiber proteins

Alteration of the natural tropism of adenovirus (Ad) will permit gene transfer into specific cell types and thereby greatly broaden the scope of target diseases that can be treated by using Ad. We have constructed two Ad vectors which contain modifications to the Ad fiber coat protein that redirect virus binding to either alpha(v) integrin [AdZ.F(RGD)] or heparan sulfate [AdZ.F(pK7)] cellular receptors. These vectors were constructed by a novel method involving E4 rescue of an E4-deficient Ad with a transfer vector containing both the E4 region and the modified fiber gene. AdZ.F(RGD) increased gene delivery to endothelial and smooth muscle cells expressing alpha(v) integrins. Likewise, AdZ.F(pK7) increased transduction 5- to 500-fold in multiple cell types lacking high levels of Ad fiber receptor, including macrophage, endothelial, smooth muscle, fibroblast, and T cells. In addition, AdZ.F(pK7) significantly increased gene transfer in vivo to vascular smooth muscle cells of the porcine iliac artery following balloon angioplasty. These vectors may therefore be useful in gene therapy for vascular restenosis or for targeting endothelial cells in tumors. Although binding to the fiber receptor still occurs with these vectors, they demonstrate the feasibility of tissue-specific receptor targeting in cells which express low levels of Ad fiber receptor.