Direct in vivo gene transfer into the coronary and peripheral vasculatures of the intact dog

Synthetic Vascular Grafts Seeded with Genetically Modified Endothelium in the Dog: Evaluation of the Effect of Seeding Technique and Retroviral Vector on Cell Persistence in Vivo

Unique characteristics of endothelium make it an attractive target cell for gene transfer. Genetically modified endothelial cells (ECs) seeded on synthetic vascular grafts offer the potential to control neointimal hyperplasia, decrease graft thrombogenicity and improve small diameter graft patency. This study addresses the issue of synthetic vascular graft colonization with endothelial cells transduced with noninducible retroviral marker genes in the dog. Autologous endothelial cells were enzymatically harvested and transduced with either the bacterial NeoR gene or human growth hormone gene using retroviral vectors. All transduced cells were positive by polymerase chain reaction (PCR) amplification for the transduced gene sequence prior to graft seeding. Transduced ECs were seeded on Dacron grafts (n = 3) pre-clotted with autologous blood. These grafts exhibited complete endothelialization at times from 250 to 360 days. Recovered DNA, however, was negative for the transduced gene sequence when analyzed by PCR and Southern blotting. Expanded polytetrafluoroethylene (ePTFE) was evaluated (n = 8) using several different cell seeding protocols. Grafts were seeded at 3 densities (ranging from 6 × 103 to 1.5 × 105 cells/cm2) and 2 different adherence times. Seeding substrate was also evaluated. Grafts were either preclotted with whole blood or incubated with 20 or 120 μg/ml fibronectin for 60 min. Graft biopsies were evaluated from 2 to 52 wk. Limited endothelialization was present in 4 dogs as early as 2 wk, but never progressed to full luminal coverage. The remaining dogs failed to ever exhibit any luminal EC adherence. Two dogs with limited EC coverage had positive DNA by PCR for the NeoR gene sequence at 2 and 3 wk. In contrast to transduced EC's, nontransduced EC colonization of ePTFE was complete at 2 wk when seeded under conditions that transduced cells had failed to persist. Neither seeding density, adherence time, seeding substrate or retroviral vector used influenced the uniformly poor graft coverage seen with transduced cells. Results of this study indicate that despite successful gene transfer using 4 different retroviral vectors, transduced endothelial cells seeded under varying conditions appear altered in their ability to stably adhere and colonize synthetic vascular grafts in vivo.

Efficient transgene expression from naked DNA delivered into an arterio-venous fistula model for kidney dialysis

BACKGROUND

Patients with kidney failure frequently require the formation of an arterio-venous fistula (AVF) in which a vein is connected to an artery resulting in arterialization of the vein to allow adequate blood flow into an external 'artificial kidney'. In most patients, neo-intimal hyperplasia (NIH) ensues, causing narrowing and subsequent occlusion of the vein, leading to significant morbidity. The cellular events causing venous NIH may serve as ideal targets for molecular-based therapies. However, therapeutic gene delivery into the vascular system is seriously impeded by problems related to the low efficacy and toxicity of targeted viral vector delivery.

MATERIALS AND METHODS

To explore the feasibility of a plasmid-based vascular gene delivery system, we established a rat AVF model that develops NIH. Plasmids encoding for reporter or therapeutic genes were delivered into the blood vessels at the time or after AVF formation.

RESULTS

Intra-luminal injection of plasmid into the AVF resulted in extensive and long-term reporter gene expression at the venous limb mainly at the site of NIH formation. Transgene expression was confined to endothelial cells and myofibroblasts that migrate inwards from the adventitia and form the NIH lesion. There was no detrimental tissue reaction to plasmid delivery, contrasting with the severe inflammatory response observed after adenovirus infection. Intra-vascular delivery of a plasmid carrying the endothelial nitric oxide synthase gene resulted in sustained production of nitric oxide, previously shown to mitigate NIH formation.

CONCLUSIONS

These findings open the possibility of vascular transduction with naked DNA bearing therapeutic genes in areas prone to NIH to ameliorate vein graft pathologies using simple and clinically applicable vector delivery methods.

Nanomedicine approaches in vascular disease: a review

Nanomedicine approaches have revolutionized the treatment of cancer and vascular diseases, where the limitations of rapid nonspecific clearance, poor biodistribution and harmful side effects associated with direct systemic drug administration can be overcome by packaging the agents within sterically stabilized, long-circulating nanovehicles that can be further surface-modified with ligands to actively target cellular/molecular components of the disease. With significant advancements in genetics, proteomics, cellular and molecular biology and biomaterials engineering, the nanomedicine strategies have become progressively refined regarding the modulation of surface and bulk chemistry of the nanovehicles, control of drug release kinetics, manipulation of nanoconstruct geometry and integration of multiple functionalities on single nanoplatforms. The current review aims to capture the various nanomedicine approaches directed specifically toward vascular diseases during the past two decades. Analysis of the promises and limitations of these approaches will help identify and optimize vascular nanomedicine systems to enhance their efficacy and clinical translation in the future.

FROM THE CLINICAL EDITOR

Nanomedicine-based approaches have had a major impact on the treatment and diagnosis of malignancies and vascular diseases. This review discusses various nanomedicine approaches directed specifically toward vascular diseases during the past two decades, highlighting their advantages, limitations and offering new perspectives on future applications.

Tubular cationized pullulan hydrogels as local reservoirs for plasmid DNA

In the present study, we measured the ability of various cationized pullulan tubular hydrogels to retain plasmid DNA, and tested the ability of retained plasmid DNA to transfect vascular smooth muscle cells (VSMCs). Cationized pullulans were obtained by grafting at different charge densities ethylamine (EA) or diethylaminoethylamine (DEAE) on the pullulan backbone. Polymers were characterized by elemental analysis, acid-base titration, size exclusion chromatography, Fourier-transform infrared spectroscopy, and proton nuclear magnetic resonance. The complexation of cationized pullulans in solution with plasmid DNA was evidenced by fluorescence quenching with PicoGreen. Cationized pullulans were then chemically crosslinked with phosphorus oxychloride to obtain tubular cationized pullulan hydrogels. Native pullulan tubes did not retain loaded plasmid DNA. In contrast, the ability of cationized pullulan tubes to retain plasmid DNA was dependent on both the amine content and the type of amine. The functional integrity of plasmid DNA in cationized pullulan tubes was demonstrated by in vitro transfection of VSMCs. Hence, cationized pullulan hydrogels can be designed as tubular structures with high affinity for plasmid DNA, which may provide new biomaterials to enhance the efficiency of local arterial gene transfer strategies.

Cationized pullulan 3D matrices as new materials for gene transfer

This study deals with the development of a novel biocompatible cationized pullulan three-dimensional matrix for gene delivery. A water-soluble cationic polysaccharide, diethylaminoethyl-pullulan (DEAE-pullulan), was first synthesized and characterized. Fluorescence quenching and gel retardation assays evidenced the complexation in solution of DNA with DEAE-pullulan, but not with neutral pullulan. On cultured smooth muscle cells (SMCs) incubated with DEAE-pullulan and a plasmid vector expressing a secreted form of alkaline phosphatase (pSEAP), SEAP activity was 150-fold higher than with pSEAP alone or pSEAP with neutral pullulan. DEAE-pullulan was then chemically crosslinked using phosphorus oxychloride. The resulting matrices were obtained in less than a minute and molded as discs of 12 mm diameter and 2 mm thickness. Such DEAE-pullulan 3D matrices were loaded with up to 50 microg of plasmid DNA, with a homogeneous plasmid loading observed with YOYO-1 fluorescence staining. Moreover, the DEAE-pullulan matrix was shown to protect pSEAP from DNase I degradation. Incubation of cultured SMCs with pSEAP-loaded DEAE-pullulan matrices resulted in significant gene transfer without cell toxicity. This study suggests that these cationized pullulan 3D matrices could be useful biomaterials for local gene transfer.

Transgene delivery of plasmid DNA to smooth muscle cells and macrophages from a biostable polymer-coated stent

Metallic stents coated with a polyurethane emulsion containing plasmid DNA were implanted in rabbit iliac arteries to evaluate transgene delivery and expression in the vessel wall. The expression of the plasmid-encoded marker genes, beta-galactosidase, luciferase and green fluorescence protein (GFP), were evaluated at 7 days after implantation. In all cases, plasmid transfer was confined to the vessel wall at the site of stent implantation, plasmid DNA was not observed in vessel segments immediately proximal or distal to the stent and dissemination of plasmid DNA to lung, liver or spleen was not observed. Expression of transgenes occurred only in vessel segments in contact with the stent and analysis of the GFP expression pattern revealed a high frequency of marker protein-positive cells occurring at or near the luminal surface. The extent of transgene expression was dependent upon the quantity of DNA loaded onto the stent and no signal was detected in vessel segments that received polymer-coated stents lacking plasmid DNA. Of significance, colocalization studies identified transgene expression not only in vascular smooth muscle cells but also in macrophages. Hence, polymer-coated stents provide a new capability for transgene delivery to immune cells that are believed to contribute to the development of in-stent restenosis.

Biochemical and biophysical characteristics of lipoplexes pertinent to solid tumour gene therapy

Cationic liposomes have become the reagent of choice for transfer of nucleic acids such as plasmids and oligodeoxynucleotides to cells in culture and in vivo. Whilst these reagents have several advantages over other forms of nucleic acid transfer methods, toxicity remains a significant problem, especially in vivo. Recent studies have also highlighted the immunostimulatory nature of these cationic vesicles when complexed to plasmid DNA, a phenomenon that may be harnessed for efficacious usage against tumours. Current research in this dynamic technological field is aimed at the development of cationic lipids that have negligible toxic effects and enhanced transfection capabilities.

Vehicles for oligonucleotide delivery to tumours

The vasculature of a tumour provides the most effective route by which neoplastic cells may be reached and eradicated by drugs. The fact that a tumour's vasculature is relatively more permeable than healthy host tissue should enable selective delivery of drugs to tumour tissue. Such delivery is relevant to carrier-mediated delivery of genetic medicine to tumours. This review discusses the potential of delivering therapeutic oligonucleotides (ONs) to tumours using cationic liposomes and cyclodextrins (CyDs), and the major hindrances posed by the tumour itself on such delivery. Cationic liposomes are generally 100-200 nm in diameter, whereas CyDs typically span 1.5 nm across. Cationic liposomes have been used for the introduction of nucleic acids into mammalian cells for more than a decade. CyD molecules are routinely used as agents that engender cholesterol efflux from lipid-laden cells, thus having an efficacious potential in the management of atherosclerosis. A recent trend is to employ these oligosaccharide molecules for delivering nucleic acids in cells both in-vitro and in-vivo. Comparisons are made with other ON delivery agents, such as porphyrin derivatives (< 1 nm), branched chain dendrimers (approximately 10 nm), polyethylenimine polymers (approximately 10 nm), nanoparticles (20-1,000 nm) and microspheres (> 1 microm), in the context of delivery to solid tumours. A discourse on how the chemical and physical properties of these carriers may affect the uptake of ONs into cells, particularly in-vivo, forms a major basis of this review.

Somatic gene therapy in the cardiovascular system

This review surveys a range of approaches using plasmid DNA encoding the 165-amino-acid isoform of vascular endothelial growth factor (phVEGF165) to therapeutically modulate micro- or macrovascular endothelial cells, focusing on strategies to augment postnatal collateral circulation in arterial insufficiency or to accelerate re-endothelialization after balloon angioplasty to prevent restenosis. We focus on intra-arterial and intramuscular/intramyocardial gene transfer of the VEGF165 gene, the options that have been most thoroughly studied to date in patients. We review developmental and postnatal significance of the endothelial-cell-specific mitogen VEGF that has stimulated these studies and present limitations of current knowledge as well as challenges for the future.

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.

Delivery of lipoplexes for genotherapy of solid tumours: role of vascular endothelial cells

The cells constituting a solid tumour may vary considerably due to biological disparities, but for a solid tumour to pose as a threat to its host, an adequate blood supply has to be established. Although neovascularisation may have dire consequences for the host, it provides a common route by which tumours in general may be reached and eradicated by drugs. The fact that a tumour's vasculature is relatively more permeable than healthy host tissue means that selective delivery of drugs may be achieved. A closer examination of the role played by the cells making up the tumour vascular bed, vascular endothelial cells (VECs), is required to facilitate design of ways for enhancing drug delivery to solid tumours via the vascular route. VECs have two major roles in the body, barrier and transport, both of which are highly pertinent to drug delivery. This review discusses the factors regulating VEC function, and how these cells may be manipulated in-vivo to improve the selective delivery of lipoplexes, carriers for gene therapy constructs, to solid tumours. It also discusses how genotherapeutic drugs may be targeted against tumour VECs on the premise that by killing these cells, the tumour itself will perish.

Myocardial injury-induced fibroblast proliferation facilitates retroviral-mediated gene transfer to the rat heart in vivo

BACKGROUND

Efficient and stable transfer of therapeutic DNA into injured myocardium would be an initial step towards a genetic treatment aimed at myocardial repair after myocardial infarction. Proliferating cardiac fibroblasts in the healing myocardium could be a compelling target for retroviral infection. We evaluated the feasibility of direct in vivo gene transfer into injured myocardium using a high-titer, stable retroviral vector.

METHODS

Using the TE-FLY-A-based MFG retroviral vector harboring nlsLacZ reporter, the gene transfer efficiency was assessed first in vitro in rat cardiac fibroblasts, followed by in vivo evaluation in healing rat myocardium after local freeze-thaw injury. A total of 2.5 x 10(7) infectious units of retrovirus were injected into the injured region of a beating rat heart. The transduced cells were identified by X-gal staining and immunohistochemistry.

RESULTS

Highly efficient transduction of cardiac fibroblasts was observed in vitro with 98% of the cells transduced with single infection. The cell proliferation index in the cardiac granulation tissue appeared maximal 3 days after cryoinjury. Retroviral injection into the injured beating heart induced gene expression localized to the wound repair region. One week after retrovirus injection, 14% of the cells in the reparative tissue were beta-gal-positive, while 4% were beta-gal-positive after 4 weeks. The transduced cells were mostly myofibroblasts.

CONCLUSIONS

Local gene transfer to the healing rat heart is feasible by retrovirus in vivo. This observation may serve as a useful guide for the development of gene therapy aimed at myocardial repair after myocardial infarction.

Vascular Applications of Human Gene Therapy

Complexing recombinant DNA with cationic liposomes is a convenient means of introducing foreign genes into cells (lipofection) and could potentially form the basis for genetically modifying diseased blood vessels in patients. The mechanism of lipofection is incompletely understood, but it is recognized that the degree of successful gene transfer is highly dependent on cell type. We have transfected primary cultures of human vascular smooth muscle cells with a plasmid expressing either firefly luciferase (Luc) or nuclear-localized beta-galactosidase (NL-beta-gal). Cells were derived from either normal human internal mammary arteries, fragments of primary atherosclerotic plaque, or fragments of restenotic lesion. Concurrent lipofection of rabbit vascular smooth muscle cells and NIH 3T3 cells was performed as well. Compared with NIH 3T3 cells, expression in human vascular smooth muscle cells was markedly reduced: In cells derived from internal mammary artery, Luc expression, normalized for protein content, was 123-fold lower than in NIH 3T3 cells, while the proportion of cells expressing NL-beta-gal was 30-fold lower. Luc expression in cells derived from restenotic tissue was significantly greater than from cells derived from primary plaque. Within a given population of cells, the mitotic index of cells expressing the recombinant gene was significantly higher than the mitotic index for the total population of cells (p < 0.05). Finally, cotransfection experiments, in which lipofection of smooth muscle cells was performed using genes for NL-beta-gal and for human growth hormone, showed that among positive transfectants a high proportion of cells (23-36%) coexpressed both genes. Thus, the efficiency of successful lipofection in human vascular smooth muscle cells in vitro is low. Transfection appears to be preferentially facilitated in cells derived from restenotic tissue and specific properties of smooth muscle cells, including growth rates, appear to be critical for successful transfection. Further elucidation of cell properties that promote transfection is required to augment the efficiency of liposome-mediated gene transfer in human vascular cells.

Selection of cell specific peptides in a rat carotid injury model using a random peptide-presenting bacterial library

Cell specific peptides are possible candidates to enable targeted delivery of drugs and therapeutic genes in vivo. This study explores the utility of using a peptide-presenting bacterial library (pFliTrx) for the selection of new cell specific peptides, which bind to vascular cells of perfused tissues or organs. The balloon-injured rat carotid artery served as a model. Following perfusion of injured vascular segments with pFliTrx, 36 single clones could be identified. In radioligand binding studies, one of them, peptide P36, binds predominantly to perfused injured versus control vessel segments. It was additionally found that P36 binds with a 700-fold higher affinity in vitro to endothelial cells stimulated by treatment with LPS and TNF-alpha compared with unstimulated endothelial cells. The amino acid sequence of P36 reveals high homology to alpha(4)beta(1)-integrin, which mediates leukocyte migration from the vasculature at sites of inflammation via binding to cellular adhesion molecules, such as VCAM. In summary, this study demonstrates, that high specific peptides directed against injured vascular cells can be selected using a random peptide-presenting bacterial library.

A pressure-mediated nonviral method for efficient arterial gene and oligonucleotide transfer

In this study, we report a method of controlled pressure-mediated delivery of "naked" DNA that achieves efficient and safe arterial gene and oligonucleotide transfer. We demonstrated a pressure-dependent uptake of fluorescein-labeled (FITC) oligonucleotide (ODN) in rabbit carotid arteries with preexisting neointimal hyperplasia, using nondistending intravascular delivery pressures ranging from 0 to 760 mm Hg. At an infusion pressure of 50 mm Hg, 10.5+/-5% of neointimal cell nuclei were positive for nuclear uptake of FITC-ODN 4 days after transfection. With an infusion pressure of 760 mm Hg, the transfection efficiency increased to 84.2+/-5.3% of neointimal cells, and to 64.5+/-11.6 and 92.4+/-5.5% of medial and adventitial cells, respectively. Similar patterns of FITC-ODN uptake were seen in atherosclerotic injured arteries. We also investigated the pressure-mediated delivery of plasmid DNA. Transfection of a luciferase expression plasmid, using an infusion pressure of 760 mm Hg, yielded luciferase expression of 816.6+/-108.6 fg/mg protein in normal rabbit carotid arteries, as compared with 38.9+/-23.7 fg/mg protein at 100 mm Hg. Luciferase expression was significantly higher in pressure-transfected injured atherosclerotic arteries (5467.3+/-1047.6 fg/mg protein at 760 mm Hg). Transfection of beta-galactosidase indicated that significant transgene expression occurred in the neointima and media. These data indicate that this pressure-mediated transfection method yields efficient oligonucleotide delivery and enhances transduction with plasmid DNA in normal as well as injured nonatherosclerotic or atherosclerotic arteries.

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.

Lipoplexes and tumours. A review

The need for genotherapy to refocus its attention on to laboratory evaluation of better methods rather than proceeding to the clinic with semi-apt tools for genetic transfer has been highlighted in clinical study reports documented to date. Quintessential for tumour genotherapy is the ability to target abnormal cells, hence reducing exposure of normal cells to genetic material whilst maximizing gene dosage to tumour cells. This becomes increasingly important as genotherapy establishes itself in the clinic alongside the older modes of treatment. This review has discussed the applicability of lipoplexes for genotherapy of solid tumours. Lipoplexes have been used extensively for gene transfer into cells, such as cancerous cells, deficient for a certain gene product. While cationic liposomes have many advantages over other forms of delivery mechanisms, several problems hinder their use in-vivo. A closer examination of the physical limitations of current lipoplex preparations, the development and testing of novel formulations, combined with more attention to the cellular processes of cell membrane breaching and nuclear entry, may enhance gene delivery. Essential for tumour genotherapy is the ability to target these lipoplexes into tumour sites whilst reducing gene dosage to other normal tissues. Development of a better lipofection agent may indeed require a collaboration of the fields of physiology, cell biology, molecular biology, biochemistry, chemistry and membrane physics.

Gene delivery to the myocardium by intrapericardial injection

Several studies have demonstrated the feasibility of gene transfer into the heart muscle. However, all the available data also indicate that the extent of transfection remains limited. As an alternative method to intravascular administration, we have developed a novel strategy which uses the pericardial sac. When a replication-deficient adenovirus containing the cDNA encoding a bacterial beta-galactosidase is injected into the pericardial sac of adult Wistar rats the staining is exclusively restricted to the pericardial cell layers. However, injecting a mixture of collagenase and hyaluronidase together with the virus, leads to a large diffusion of the transgene activity, reaching up to 40% of the myocardium. Transgene expression is predominant in the left ventricle and the interventricular septum but limited in the right ventricle. In vivo echocardiographic measurements of the left ventricular diameters at end diastolic and end systolic times show no difference between virus- and sham-injected animals, thus indicating a good clinical tolerance to this strategy of virus delivery. The same protocol has been used with the same efficiency in mice, which leads us to propose injection into the pericardial sac as an effective and harmless method for gene transfer into the heart muscle.

Histochemical discrimination of endogenous mammalian beta-galactosidase activity from that resulting from lac-Z gene expression

Minces of several organs from the transgenic mouse ROSAbeta-gal 26 (ROSA-26), which robustly expresses bacterial lac-Z in most tissues, were exposed to 4-bromo-5-chloro-3-indoyl-beta-D-galactopyrosanide (X-gal) at pH ranging from 7.5 to 9.5 to determine the optimal pH for in situ demonstration of bacterial beta-galactosidase activity (neutral pH optimum) while minimizing detection of potentially confounding endogenous mammalian beta-galactosidase (acidic pH optimum). Similar studies were performed with organ minces from C57BL/6 mice, Sprague-Dawley rats, New Zealand white rabbits, and macaques to confirm the effect of pH on minimizing detection of endogenous mammalian beta-galactosidase. In all organs evaluated; heart, liver, spleen, kidney, brain, and skeletal muscle, endogenous beta-galactosidase activity was rarely detected following incubation at pH greater than 7.5. In contrast, bacterial beta-galactosidase activity in the ROSA-26 mice was strongly detected in organ minces following incubation at pH 8.0-9.0. These findings are similar to previous observations we have made in lung minces and confirm that a simple alteration of a commonly used histochemical technique for detecting in situ beta-galactosidase activity, raising the reaction buffer pH to weakly alkaline range, can reliably distinguish between endogenous activity and that resulting from exogenous bacterial gene expression.

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.

Adenovirus-mediated gene transfer to lower limb artery of patients with chronic critical leg ischemia

Arterial gene transfer offers a promising new approach for the treatment of vascular disorders. However, no data are available about the gene transfer efficiency in human arteries in vivo. The aim of this study was to evaluate the safety and feasibility of catheter-mediated adenoviral gene transfer in human peripheral arteries. Ten patients (8 females, 2 males, mean age 80 +/- 8 years) suffering from chronic critical leg ischemia with a prior decision for amputation were recruited in the study. Gene transfer was performed in eight patients in conjunction with a conventional percutaneous transluminal angioplasty, using a perfusion coil balloon catheter. Two patients served as controls. Increasing concentrations of replication-deficient adenoviruses (titers from 1 x 10(8) to 4 x 10(10) PFU) containing a nuclear-targeted beta-galactosidase marker gene were administered into the arteries over 10 min via the catheter. Amputations were performed 20 to 51 hr after the procedures and gene transfer efficiency was evaluated in the transduced arteries using X-Gal staining for beta-galactosidase activity. Beta-galactosidase gene transfer was well tolerated and no adverse tissue responses or systemic complications were observed in any of the patients. Gene transfer was successful in six of the eight patients. Gene transfer efficiency varied between 0.04 and 5.0% of all arterial cells. Transgene expression was detected in smooth muscle cells, endothelial cells, and macrophages and in tunica adventitia. However, transgene activity was not evenly distributed in the arterial wall and no transgene activity was found beneath advanced atherosclerotic lesions. The safety and feasibility of in vivo gene transfer by adenoviral vectors to human peripheral arteries were established. Although improvements are still required in gene transfer efficiency, these findings suggest that adenoviruses can be used to deliver therapeutically active genes into human arteries.

Gene transfer into the carotid artery using an adventitial collar: comparison of the effectiveness of the plasmid-liposome complexes, retroviruses, pseudotyped retroviruses, and adenoviruses

We studied the efficiency of plasmid/liposome complexes, Moloney murine leukemia virus-derived (MMLV) retroviruses, pseudotyped vesicular stomatitis virus protein-G (VSV-G)-containing retroviruses, and adenoviruses in delivering genes into the rabbit carotid artery using a silastic collar applied to the adventitia. This method was used for gene transfer because (a) it provides a gene delivery reservoir; (b) no intraluminal manipulations are performed; (c) installation of the collar induces arterial smooth muscle cell (SMC) proliferation and enhances retroviral gene transfer efficiency where target cell proliferation is required. The transfer of the beta-galactosidase (lacZ) marker gene to the adventitia and media occurred with all gene transfer systems. Adenoviruses also transferred the beta-galactosidase gene to some endothelial cells. After 5 days, adenoviral vectors produced the highest gene transfer efficiency with up to 10%+/-6% of cells showing beta-galactosidase activity. Pseudotyped VSV-G retroviruses were also effective in achieving gene transfer in 0.05%+/-0.03% of cells in the adventitia and media. Plasmid/liposome complexes and MMLV retroviruses infected 0.05%+/-0.03% and <0.01%+/-0.01% of cells, respectively. It is concluded that replication-deficient adenoviruses, VSV-G pseudotyped retroviruses, and plasmid/liposome complexes can be used for gene transfer to the arterial wall using the collar method. Because the endothelium remains anatomically present throughout the experiments, the model may be useful for the gene transfer studies involving diffusible or secreted gene products that primarily act on the endothelium. Effects on medial SMC and even endothelium can be achieved from the adventitial side, suggesting an alternative route for the delivery of therapeutically useful genes into the arterial wall.

In situ histochemical detection of beta-galactosidase activity in lung: assessment of X-Gal reagent in distinguishing lacZ gene expression and endogenous beta-galactosidase activity

Bacterial lacZ is one of the most commonly used reporter genes for assessing gene transfer to lung. However, lung contains endogenous beta-galactosidase (beta-Gal), which can confound estimation of exogenous lacZ expression by histochemical techniques (i.e., X-Gal) for in situ demonstration of enzyme activity. We investigated several parameters of the X-Gal reaction, including time and temperature of X-Gal exposure as well as lung tissue processing and fixation techniques, and found that none of these could be used to distinguish between endogenous and exogenous beta-Gal activities. The mammalian and bacterial beta-Gal enzymes, however, have pH optima in the acidic and neutral ranges, respectively. Exposing whole lung, lung minces, or mounted frozen sections of lung to X-Gal at mildly alkaline pH (pH 8.0-8.5), minimized detection of endogenous activity in lungs from a variety of species while preserving that resulting from bacterial enzyme activity in a transgenic mouse expressing lacZ. This technique was also useful in distinguishing endogenous activity from that resulting from adenovirus-mediated lacZ gene transfer to diploid lung fibroblasts in primary culture. An appropriate buffer that maintains the desired pH throughout the duration of X-Gal exposure must be used.

Gene therapy for vascular disease

Atherosclerosis is a degenerative process characterized by endothelial cell dysfunction, inflammatory cell adhesion and infiltration, and the accumulation of cellular and matrix elements leading to the formation of fibrocellular plaques. In the end stages, advanced occlusive plaques limit blood flow and oxygen delivery resulting in the well-known ischemic syndromes of the coronary, skeletal muscle, mesenteric, and cerebrovascular circulation. Moreover, sudden critical ischemic events may be precipitated by plaque disturbance, rupture, hemorrhage, and/or thrombosis. Traditional pharmacologic approaches have been effective in reducing serum cholesterol and controlling thrombosis but, in the main, have had little impact on the treatment of advanced lesions. The purpose of this review is to examine the current status of gene therapy for vascular proliferation, aberrant endothelial function, thrombosis, peripheral ischemia, and modification of the blood/biomaterial interface.

Gene therapy and vascular disease: potential applications in vascular surgery

Advances in molecular biology have generated methods that are used to enhance diagnosis and treatment of a variety of human diseases. More recently modification of gene expression in cells by gene transfer has been introduced as a new therapeutic modality. The targeting of vascular cells with this method is appealing not only for anatomical reasons, but also because endovascular techniques provide access to the vasculature and makes site-specific delivery possible. Over the past few years, gene transfer has been widely used to explore the pathophysiology of vascular diseases in experimental models and available data suggests that this method may eventually become a therapeutic alternative for vascular disorders such as restenosis, graft failure, and critical ischaemia. In the following we discuss the methodology of gene transfer, its tentative use in vascular diseases related to vascular surgery, and the problems associated with this new technology.

Established immunity precludes adenovirus-mediated gene transfer in rat carotid arteries. Potential for immunosuppression and vector engineering to overcome barriers of immunity

Preclinical arterial gene transfer studies with adenoviral vectors are typically performed in laboratory animals that lack immunity to adenovirus. However, human patients are likely to have prior exposures to adenovirus that might affect: (a) the success of arterial gene transfer; (b) the duration of recombinant gene expression; and (c) the likelihood of a destructive immune response to transduced cells. We confirmed a high prevalence (57%) in adult humans of neutralizing antibodies to adenovirus type 5. We then used a rat model to establish a central role for the immune system in determining the success as well as the duration of recombinant gene expression after adenovirus-mediated gene transfer into isolated arterial segments. Vector-mediated recombinant gene expression, which was successful in naive rats and prolonged by immunosuppression, was unsuccessful in the presence of established immunity to adenovirus. 4 d of immunosuppressive therapy permitted arterial gene transfer and expression in immune rats, but at decreased levels. Ultraviolet-irradiated adenoviral vectors, which mimic advanced-generation vectors (reduced viral gene expression and relatively preserved capsid function), were less immunogenic than were nonirradiated vectors. A primary exposure to ultraviolet-irradiated (but not nonirradiated) vectors permitted expression of a recombinant gene after redelivery of the same vector. In conclusion, arterial gene transfer with current type 5 adenoviral vectors is unlikely to result in significant levels of gene expression in the majority of humans. Both immunosuppression and further engineering of the vector genome to decrease expression of viral genes show promise in circumventing barriers to adenovirus-mediated arterial gene transfer.

Pharmaceutical approach to somatic gene therapy

The pharmaceutical approach to somatic gene therapy is based on consideration of a gene as a chemical entity with specific physical, chemical and colloidal properties. The genes that are required for gene therapy are large molecules (> 1 x 10(6) Daltons, > 100 nm diameter) with a net negative charge that prevents diffusion through biological barriers such as an intact endothelium, the plasma membrane or the nuclear membrane. New methods for gene therapy are based on increasing knowledge of the pathways by which DNA may be internalized into cells and traffic to the nucleus, pharmaceutical experience with particulate drug delivery systems, and the ability to control gene expression with recombined genetic elements. This article reviews two themes in the development of gene therapies: first, the current approaches involving the administration of cells, viruses and plasmid DNA; second, the emerging pharmaceutical approach to gene therapy based on the pharmaceutical characteristics of DNA itself and methods for advanced drug delivery.

Inhibition of vascular contraction by intracisternal administration of preproendothelin-1 mRNA antisense oligoDNA in a rat experimental vasospasm model

To clarify the role of endothelin-1 (ET-1) in the etiology of hemolysate-induced contraction of vessels, the authors introduced antisense oligoDNA for preproendothelin-1 (ppET-1) messenger RNA in a rat model of vasospasm. Phosphorothioate antisense oligoDNAs for ppET-1 were injected into the cisterna magna. Fluorescein isothiocyanate-labeled phosphorothioate antisense oligoDNAs were proven by fluorescence chasing to be incorporated into the vascular wall. Striking inhibitory effects of experimental vasospasm were observed in the basilar artery (BA) in which the oligoDNAs were injected. The vascular contraction was significantly inhibited by oligoDNAs after 20 minutes of hemolysate exposure, which suggested that ET synthesis started approximately 20 minutes after hemolysate stimulation. Expression of ppET-1 in the BA in which the spasm was inhibited was markedly suppressed at the transcription level. The results indicate that ET-1 may play an important role in hemolysate-induced vasoconstriction in rats. In addition, the antisense approach in the cerebrospinal fluid might be a useful tool for preventing cerebral vasospasm.

Gene transfer by adenovirus in smooth muscle cells

We report adenovirus-mediated gene transfer into airway smooth muscle cells in cultured cells and organ-cultured tracheal segments. Incubation of cultured rat tracheal myocytes with virus (5 x 10(8) pfu/ml) for 6 h resulted in beta-galactosidase expression in 94.8 +/- 2.5% of cells (n = 4). Following incubation of thin (less than 200 microns diameter) equine trachealis muscle segments with virus in organ culture (5 x 10(8)-5 x 10(10) pfu/ml) the average expression of the Lac Z gene was approximately 19 +/- 10% (n = 9). Expression was markedly improved, however, in segments from neonatal rats (13-21 days). In two experiments in which the mucosa and serosa were removed, nearly all cells expressed beta-galactosidase, whereas in a third experiment in which the tissue was not dissected, about 40% of cells were stained. Viral infection had no effect on tension development of strips following organ culture. In vitro gene transfer may provide a useful method to alter protein expression and examine the effect of this alteration on excitation/contraction coupling in smooth muscle.

Cardiovascular gene therapy: current concepts

Gene therapy techniques are under development for many areas of medicine, including cardiovascular disease. Identifying appropriate gene targets will require more detailed knowledge of the molecular pathophysiology of these disorders, and choosing appropriate vectors and delivery systems will contribute significantly to the challenge of developing this approach for clinical use. The concepts of toxicology and therapeutic drug monitoring will need to be broadened to account for the unique chemical, biological, and genetic characteristics of gene therapeutic agents. This review will provide an overview of strategy development, currently available vectors, and examples of their application to cardiovascular gene transfer. Considerations of the potential toxicities associated with particular vectors and delivery systems, as well as the types of genetic modifications possible, will provide some guidelines regarding appropriate monitoring of their clinical application.

Adenovirus-assisted lipofection: efficient in vitro gene transfer of luciferase and cytosine deaminase to human smooth muscle cells

Smooth muscle cells (SMC) are a central cell type involved in multiple processes of coronary artery diseases including restenosis and therefore are major target cells for different aspects of gene transfer. Previous attempts to transfect primary arterial cells using different techniques like liposomes, CaPO4 and electroporation resulted in only low transfection efficiency. The development of recombinant adenoviruses dramatically improved the delivery of foreign genes into different cell types including SMC. However, cloning and identification of recombinants remain difficult and time-consuming techniques. The present study demonstrates that a complex consisting of reporter plasmid encoding firefly luciferase (pLUC), polycationic liposomes and replication-deficient adenovirus was able to yield very high in vitro transfection of primary human smooth muscle cells under optimized conditions. The technique of adenovirus-assisted lipofection (AAL) increases transfer and expression of plasmid DNA in human smooth muscle cells in vitro up to 1000-fold compared to lipofection. To verify the applicability of AAL for gene transfer into human smooth muscle cells we studied a gene therapy approach to suppress proliferation of SMC in vitro, using the prokaryotic cytosine deaminase gene (CD) which enables transfected mammalian cells to deaminate 5-fluorocytosine (5-FC) to the highly toxic 5-fluorouracil (5-FU). The effect of a transient CD expression on RNA synthesis was investigated by means of a cotransfection with a RSV-CD expression plasmid and the luciferase reporter plasmid. Western blot analysis demonstrated high expression of CD protein in transfected SMC. Cotransfected SMC demonstrated two-fold less luciferase activity in the presence of 5-FC (5 mmol/l) after 48 h compared to cells transfected with a non-CD coding plasmid. The data demonstrate that a transient expression of CD could be sufficient to reduce the capacity of protein synthesis in human SMC. This simple and effective in vitro transfection method may also be applicable to in vivo delivery of target genes to the vascular wall to inhibit SMC proliferation.

Arterial gene transfer for therapeutic angiogenesis in patients with peripheral artery disease

The age-adjusted prevalence of peripheral arterial disease (PAD) in the U.S. population has been estimated to approach 12%. The clinical consequences of occlusive peripheral arterial disease (PAD) include pain on walking (claudication), pain at rest, and loss of tissue integrity in the distal limbs; the latter may ultimately lead to amputation of a portion of the lower extremity. Surgical bypass techniques and percutaneous catheter-based interventions may be used to successfully revascularize the limbs of certain patients with PAD. In many patients, however, the anatomic extent and distribution of arterial occlusion is too severe to permit relief of pain and/or healing of ischemic ulcers. No effective medical therapy is available for the treatment of such patients. The purpose of this clinical protocol is to document the safety of therapeutic angiogenesis achieved in this case by percutaneous catheter-based delivery of the gene encoding vascular endothelial growth factor (VEGF) in patients with PAD; and, as secondary objectives, investigate the bioactivity of this strategy to relieve rest pain and heal ischemic ulcers of the lower extremities. The rationale for this human protocol is based upon preclinical studies performed in a rabbit model of hindlimb ischemia. These studies are described in detail below and in the manuscripts enclosed in the Appendix to this proposal. In brief, a single intra-arterial bolus of VEGF recombinant human protein, delivered percutaneously to the ischemic limb via an intravascular catheter, resulted in angiographic, hemodynamic, physiologic, and histologic evidence of augmented collateral artery development. Subsequently, similar results were achieved using an angioplasty catheter with a hydrogel-coated balloon to deliver 400 micrograms of a plasmid containing the cDNA for VEGF to the internal iliac artery in the same animal model. Accordingly, we propose to administer arterial gene (VEGF) therapy to patients with rest pain and/or ischemic leg ulcers considered not to be candidates for conventional revascularization techniques. The dose of plasmid to be administered will be progressively escalated beginning with 500 micrograms for the first four patients, 1000 micrograms for the following six patients, 2000 micrograms for the third group of six patients, and 400 micrograms for the fourth group of six patients.

Prevention of Restenosis by Local Drug Delivery

Local drug therapy for preventing restenosis after angioplasty has been investigated for over a decade. Biologically active agents ranging from drugs to genes can be delivered locally using a wide variety of catheters. Microspheres, liposomes, and polymers have been used to enhance drug retention at the delivery site. More recently stents have been investigated as devices to attain local drug delivery, either by coating with polymers, seeding with genetically modified cells or by using them as a source of local radiation. Though the best method of delivering agents locally remains undefined, this approach is likely to emerge as an essential mode of therapy in the near future.

Gene therapy in pediatric oncology

An increased understanding of the molecular mechanisms of cancer and the ability to introduce exogenous genes into mammalian cells has led to the development of oncologic treatment strategies based upon gene transfer. Preclinical animal models have suggested a variety of approaches which are now being tested in pediatric trials. Studies using marker genes to trace cell origin have already generated important information regarding autologous bone marrow transplantation for pediatric cancers. A variety of therapeutic genes are also being clinically tested. Trials are underway to determine if introduction of immunostimulatory genes into cancer cells can be used to enhance host antitumor immunity. Treatment of primary brain tumors with insertion of drug sensitization genes is a promising new therapy that is also being clinically evaluated. Other strategies such as insertion of drug resistance genes into hematopoietic cells, anti-oncogene therapy, and tumor suppressor gene replacement are being tested in adults and may find use in pediatric cancer treatment. Although gene transfer offers promising new approaches for the therapy of pediatric cancer, many technical problems remain which limit efficacy and widespread use. Further basic research in the molecular biology of cancer and in vector development will be required to realize the full potential of gene therapy strategies.

Cardiac gene transfer by intracoronary infusion of adenovirus vector-mediated reporter gene in the transplanted mouse heart

This study introduces a model for intracoronary gene transfer in murine cardiac isografts using adenovirus vectors. This approach may offer an opportunity to modulate alloreactivity after cardiac transplantation. Donor hearts were infected via the coronary arteries with a volume of 10(9) plaque-forming units per milliliter of a recombinant adenovirus containing the beta-galactosidase-encoding gene (Ad.CMVLacZ). In a control group, 200 microliters of normal saline solution was infused. The grafts were stored in 4 degrees C cold saline solution for 15 minutes, then transplanted heterotopically into syngeneic hosts (B10.BR). The grafts were harvested at 3, 7, 15, or 30 days (n = 5 for each group) after transplantation, and beta-galactosidase activity was assessed by histochemical staining (X-gal). All grafts were functioning when harvested. X-gal staining pattern was nonuniform with positive staining appearing in epicardial, myocardial, and endocardial cells, as well as in the vessel walls. The cells permissive to infection consisted predominantly of myocardial cells. The mean total numbers of beta-gal-positive staining cells per slice were 68.7 +/- 27.3 in the 3-day group, 330.4 +/- 53.8 in the 7-day group, 151.3 +/- 48.0 in the 15-day group, and 39.9 +/- 10.8 in the 30-day group, thus peaking in the 7-day group (p < 0.05). Control isografts (n = 5), retrieved at day 30, revealed no staining activity. In conclusion, our model demonstrates that intracoronary gene transfer to the transplanted murine cardiac grafts is feasible at the time of harvest. Adenovirus-mediated gene transfer produces widespread gene expression which, though perhaps transient, does not adversely affect myocardial structure or function. This technology may allow modification of graft immunogenicity in the future through the production of therapeutic proteins sufficient to modulate local immune responses.

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.

Directed endothelial differentiation of cultured embryonic yolk sac cells in vivo provides a novel cell-based system for gene therapy

Cultured murine yolk sac cells transfected with the cytomegalovirus immediate early promoter/human growth hormone (CMVIE-hGH) fusion gene, expressing high levels of hGH in culture, and suspended in Matrigel were subcutaneously (s.c.) injected into experimental mice. The injected cells were shown to form discrete vesicular structures within the Matrigel implant, suggesting directed differentiation of the embryonic yolk sac cells into endothelial tissue. Human growth hormone radioimmune assay of these mice showed sustained physiologically significant levels of hGH in their serum for beyond four months. These results confirmed that long-term cultured murine embryonic yolk sac cells can be induced to differentiate into endothelial cells both in vivo and in vitro and suggested a novel approach to the delivery to the circulation of therapeutic proteins for the treatment of inherited and acquired diseases.