Analysis of adenoviral transport mechanisms in the vessel wall and optimization of gene transfer using local delivery catheters

Local Endovascular Delivery, Gene Therapy, and Cell Transplantation for Peripheral Arterial Disease

Advances in catheter technology, gene identification, and cell biology may provide novel treatment options for patients with peripheral arterial disease (PAD) who are not candidates for standard revascularization procedures. Animal studies and recent results in human beings suggest that transfer of growth factors or regulatory genes and transplantation of progenitor cells may provide novel therapy options by inducing therapeutic angiogenesis or by inhibiting restenosis. This review will discuss the development of a variety of catheters for localized endovascular delivery, as well as the various cellular and genetic strategies that exist to restore blood flow to ischemic tissue and to reduce neointimal hyperplasia.

Construction and deconstruction of PLL/DNA multilayered films for DNA delivery: Effect of ionic strength

Through the layer-by-layer (LbL) self-assembly technique, DNA was incorporated into the multilayered films with poly-l-lysine (PLL). The effect of ionic strength on the construction and deconstruction of the PLL/DNA films was investigated. It was found that the salt concentration of the deposition solution had a significant effect on the construction of the films, which might attribute to the effect of salt ions on the conformation of polyelectrolytes and interaction between PLL and DNA molecules. A salt-induced deconstruction of the PLL/DNA films was observed. The extent of the deconstruction increased with the salt concentration in the incubation solution. The mechanism of the deconstruction was discussed. Taking the advantages of the LbL technique, the erasable PLL/DNA films could deposit onto a variety of surfaces, such as vascular stent, intervention catheter and tissue engineering scaffold, to serve as a novel DNA delivery system.

Local gene transduction of cyclooxygenase-1 increases blood flow in injured atherosclerotic rabbit arteries

BACKGROUND

Cyclooxygenase-1 (COX-1) is the rate-limiting component in the synthesis of prostacyclin (PGI2), an important vasodilator and antithrombotic molecule. In balloon-injured, atherosclerosis-free porcine arteries, COX-1 gene transduction increases PGI2 production, induces durable vasodilation, and reduces thrombus formation. We tested the effectiveness of COX-1 local gene transduction for the prevention of postangioplasty restenosis in atherosclerotic arteries in a hypercholesterolemic rabbit model.

METHODS AND RESULTS

We injured 1 carotid artery in 43 Watanabe heritable hyperlipidemic rabbits and performed local gene transduction using a viral vector containing the COX-1 gene (AdCOX-1, n=22) or no genes (Adnull, n=21). Three days later, AdCOX-1-treated arteries stimulated with arachidonic acid produced 100% more PGI2 (P<0.01), 400% more prostaglandin E2 (PGE2) (P<0.01), 400% more prostaglandin E1 (PGE1) (P<0.01), and 250% more cAMP (P<0.05) than Adnull-treated arteries. Twenty-eight days after treatment, Doppler sonography showed that blood flow velocity was preserved in AdCOX-1-treated arteries (ratio 0.92, injured compared with contralateral uninjured carotid artery) but reduced in Adnull-treated arteries (ratio 0.39), suggesting that AdCOX-1 prevented restenosis after injury. COX-1-transduced arteries also showed 80% greater lumen area 28 days after injury (P<0.01).

CONCLUSIONS

The effectiveness of COX-1 in preventing restenosis and preserving normal blood flow 28 days after injury results from increased lumen area caused by durable vasodilation. COX-1 efficacy correlates with an early increase in the production of PGI2, PGE2, PGE1 (known to cause vasodilation), and cAMP. These results demonstrate for the first time that COX-1 gene transduction is an effective treatment for the prevention of postangioplasty restenosis of atherosclerotic arteries under clinically relevant conditions.

Local endovascular delivery, gene therapy, and cell transplantation for peripheral arterial disease

Advances in catheter technology, gene identification, and cell biology may provide novel treatment options for patients with peripheral arterial disease (PAD) who are not candidates for standard revascularization procedures. Animal studies and recent results in human beings suggest that transfer of growth factors or regulatory genes and transplantation of progenitor cells may provide novel therapy options by inducing therapeutic angiogenesis or by inhibiting restenosis. This review will discuss the development of a variety of catheters for localized endovascular delivery, as well as the various cellular and genetic strategies that exist to restore blood flow to ischemic tissue and to reduce neointimal hyperplasia.

Catheter-mediated delivery of adenoviral vectors expressing beta-adrenergic receptor kinase C-terminus inhibits intimal hyperplasia and luminal stenosis in rabbit iliac arteries

BACKGROUND

Previous studies have shown that incubation of balloon-injured rat carotid arteries with adenoviral vectors encoding the carboxyl terminus of the beta-adrenergic receptor kinase (Ad2/betaARKct) for 30 min reduces neointima formation. However, it is unclear whether this beneficial effect of betaARKct could be achieved using a catheter-based vector delivery system and whether the observed inhibition of neointima formation translated into a reduction of vessel stenosis.

METHODS

In this study, Ad2/betaARKct was infused into the balloon-injured site of rabbit iliac arteries using a porous infusion catheter over 2 min. Twenty-eight days after gene transfer, angiographic and histological assessments were performed.

RESULTS

Angiographic and histological assessments indicate significant (p < 0.05) inhibition of iliac artery neointima formation and lumen stenosis by Ad2/betaARKct. Our studies demonstrate that an inhibitory effect of Ad2/betaARKct on neointima formation is achievable using a catheter-based vector delivery system and that the inhibition of neointima formation translates into a gain in the vessel minimal luminal diameter. The extent of inhibition (35%) was comparable to that observed with adenoviral-mediated expression of thymidine kinase plus ganciclovir treatment, a cytotoxic gene therapy approach for restenosis.

CONCLUSIONS

These results suggest that adenoviral-mediated gene transfer of betaARKct is a clinically viable cytostatic gene therapy strategy for the treatment of restenosis.

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.

A direct mechanical method for accurate and efficient adenoviral vector delivery to tissues

We describe a mechanical method for delivery of adenoviral vector to the adventitial surface of arteries and to other tissues. Our goal was to characterize, principally in intact carotid artery, the morphological, biochemical, and functional effects of mechanical delivery of a recombinant beta-galactosidase-expressing adenoviral vector following its direct application using a small paintbrush. Our ex vivo and in vivo data demonstrate efficient, accurate, and rapid transduction of arteries without compromise of their morphological, biochemical, and functional integrity. We also demonstrate the general applicability of this technique in vivo via transduction of skeletal muscle, fibrotendinous tissue, peritoneum, serosal surface of bowel, and wounded skin. We conclude that direct mechanical delivery of an adenoviral vector to tissues using a suitable paintbrush represents an intuitive, accurate, and effective means of augmenting gene transfer efficiency, and may be a useful adjunct to other delivery methods.

Inhibition of neointimal formation after stent placement with adenovirus-mediated gene transfer of I kappa B alpha in the hypercholesterolemic rabbit model: initial results

PURPOSE

To evaluate the feasibility and efficacy of the local application of a replication-defective adenovirus construct for the expression of the antiinflammatory protein I kappa B alpha, inhibitor of nuclear factor kappa B (NF-kappa B), to reduce neointimal formation after stent placement.

MATERIALS AND METHODS

Nitinol stents were implanted in the iliac arteries of hypercholesterolemic rabbits, followed by balloon dilation (30 seconds at 6 atm). Local adenovirus-mediated transfer of I kappa B alpha (3 mL of 10(9) plaque-forming units per milliliter at 6 atm) was performed and compared with three control groups: stent alone, stent plus local delivery of phosphate-buffered saline (PBS) (3 mL at 6 atm), and stent plus local delivery of control adenovirus coding for green fluorescent protein (GFP) (3 mL of 10(9) plaque-forming units per milliliter at 6 atm). A multichannel balloon was used for local drug delivery and balloon dilation. Animals were sacrificed 1 or 4 weeks after treatment. Effective transfection was demonstrated with immunofluorescence staining. Angiographic patency and luminal diameter were evaluated at quantitative angiography. Luminal and neointimal areas were measured on surface-stained ground sections with methylmethacrylate embedding and the cutting-grinding technique.

RESULTS

All vessels with stents were patent at angiography. Neointimal area was negligible in all groups 1 week after stent placement (range, 0.42-0.52 mm(2); P =.44; analysis of variance). Neointimal formation was demonstrated in all groups 4 weeks after implantation but was significantly reduced with I kappa B alpha treatment compared with treatment with stent alone (by 22%, from 2.80 mm(2) +/- 0.20 to 2.28 mm(2) +/- 0.14, P =.05), stent plus PBS (by 43%, from 3.26 mm(2) +/- 0.25 to 2.28 mm(2) +/- 0.14, P =.005), and stent plus GFP (by 53%, from 2.32 mm(2) +/- 0.19 to 1.51 mm(2) +/- 0.08, P <.005).

CONCLUSION

Local adenovirus-mediated I kappa B alpha gene transfer has the potential to reduce intimal hyperplasia after stent placement.

Molecular strategy using cis-element 'decoy' of E2F binding site inhibits neointimal formation in porcine balloon-injured coronary artery model

Transcription factor E2F plays a pivotal role in the transactivation of cell cycle regulatory genes, leading to vascular lesion formation. Double-stranded DNA with high affinity for E2F as 'decoy' cis elements may block the activation of genes mediating the cell cycle, resulting in an effective therapeutic agent for treating intimal hyperplasia. In this study, we tested the feasibility of E2F decoy therapy to treat neointimal formation in a porcine coronary artery balloon injury model. An angioplasty catheter was inserted in the left anterior descending coronary artery of pigs to cause vascular injury. Initially, we tested the feasibility of transfection of FITC-labeled E2F decoy ODN using a hydrogel balloon catheter. Fluorescence due to E2F decoy ODN could be detected throughout the medial layer. Therefore, we transfected E2F decoy ODN into the balloon-injured artery using hydrogel catheter. Of importance, intravascular ultrasound (IVUS) and histological evaluation demonstrated that plaque area in the balloon-injured artery was significantly reduced by E2F decoy ODN compared with mismatched decoy ODN at 1 month after a single transfection (P < 0.01). In contrast, luminal and total vessel areas were significantly increased in vessels treated with E2F decoy ODN as compared with mismatched decoy. Endothelial function after angioplasty was not affected by E2F decoy transfection. Finally, we tested the acute toxicity of E2F decoy ODN in monkeys, and no apparent side-effects were detected. Here, we report the successful in vivo transfer of E2F decoy ODN using a hydrogel catheter to inhibit vascular lesion formation in balloon-injured porcine coronary artery without any apparent side-effects.

Gene transfer for experimental saccular aneurysms

SUMMARY

Reinforcing an aneurysmal wall is one possible way to prevent from aneurysm rupture. We preliminarily tried focal gene transfer against the wall of experimental aneurysms to aim the transgene remodeling of aneurysmal wall. Two experimental saccular aneurysms were created on canine common carotid artery with an artificial dissecting method, which resemble clinical aneurysms. Adenovirus vector (AxCALacZ, 10(8) pfu) was slowly injected into the aneurysm cavity for over 30 minutes under the condition of intraaneurysmal flow arrest using balloon-assisted neck-plasty technique. The arteries and aneurysms were evaluated 48 hours after the transduction with X-gal staining, and beta-galactosidase expression was detected mainly in the intima in both cases. No adverse effects on the normal carotid wall and no systemic complications were observed after the procedure. This experimental study suggests the possibility of gene therapy for cerebral aneurysms.

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 expression of an anti-proliferative hybrid transgene from the human smooth muscle alpha-actin promoter suppresses smooth muscle cell proliferation and neointima formation

The retinoblastoma protein (Rb), a key regulator of cell cycle progression, can bind the transcription factor E2F converting it from a positive transcriptional factor capable of driving cells into S phase into a negative complex which arrests cells in G1. We have created a potent transcriptional repressor of E2F-dependent transcription by fusing the C-terminal fragment of Rb (p56) to the DNA and DP1-binding domains of E2F. Because the expression of E2F/56 fusion protein from a constitutive promoter was incompatible with virus growth, adenovirus constructs were prepared where transgenes were expressed from a fragment of the smooth muscle alpha-actin (SMA) promoter. Immunoblot and beta-galactosidase staining demonstrated smooth muscle-specific expression of this transcriptional element in vitro. The SMA-p56 and SMA-E2F/p56 adenoviral constructs also induced G0/G1 cell cycle arrest specifically in smooth muscle cells. Following administration to rat tissues, the SMA-beta-galactosidase construct exhibited expression in balloon-injured carotid arteries, but not in liver, bladder or skeletal muscle. Local delivery of the SMA-E2F/p56 adenoviral construct to balloon-injured carotid arteries inhibited intimal hyperplasia. Our results demonstrate that local delivery of the SMA-E2F/p56 adenoviral construct can limit intimal hyperplasia in balloon-injured vessels, while avoiding toxicity that could occur from the dissemination and expression of the viral transgene.

Combination of electroporation and DNA/dendrimer complexes enhances gene transfer into murine cardiac transplants

Electroporation is a new gene delivery method to increase gene transfer and expression in vivo. Starburst polyamidoamine dendrimers have been demonstrated to augment gene expression in vitro and in vivo. We hypothesized that the combination of electroporation and dendrimer could enhance the gene transfer and gene expression in cardiac transplants. After immersion in DNA/dendrimer complexes or intracoronary transfer of DNA/dendrimer complexes, both nonvascularized and vascularized syngeneic cardiac grafts, respectively, were subjected to serial electrical pulses before transplantation. beta-Galactosidase reporter gene expression in the graft was determined by X-Gal staining. Gene expression was enhanced 10- to 45-fold in grafts immersed in DNA/dendrimer complexes, or after intracoronary transfer of DNA/dendrimer complexes, and subjected to 20 square wave 25-ms pulses with a strength of 200 V/cm. The combination of electroporation and DNA/dendrimer complexes may provide a novel approach to enhance gene transfer and gene expression ex vivo.

Mutated p21/WAF/CIP transgene overexpression reduces smooth muscle cell proliferation, macrophage deposition, oxidation-sensitive mechanisms, and restenosis in hypercholesterolemic apolipoprotein E knockout mice

We have investigated whether by introducing a mutated p21 cyclin-dependent kinase inhibitor through a standard type 5 adenovirus (Ad), it would be possible to interfere with restenosis in hypercholesterolemic apolipoprotein E knockout mice. Restenosis is a clinically relevant, undesired effect of percutaneous transluminal coronary angioplasty (PTCA). A critical event underlying restenosis is smooth muscle cell (SMC) proliferation leading to neointimal formation and vessel reocclusion. Recent data demonstrated that it is possible to reduce restenosis by introducing various genes blocking the cell cycle through Ad vectors. Nonetheless, most experiments were conducted in the healthy carotid artery of rat, which is far from the condition of human disease. Therefore, we investigated whether antiproliferative or proapoptotic genes affect restenosis in a model of atherosclerosis closer to clinical settings. Ad-mutated(m)-p21WAF/CIP1 transgene overexpression induces a significant reduction of restenosis in hypercholesterolemic apolipoprotein E knockout mice subjected to injury of common carotid artery. This was associated with reduced SMC density and proliferation, macrophage deposition, and oxidation-sensitive mechanisms. Treatment with p21/WAF also enhanced TUNEL positivity of arterial cells. We show that in an experimental model of atherosclerosis, braking the cell proliferation through increased vascular apoptosis and reduced oxidation-sensitive signal transduction and macrophage accumulation can significantly ameliorate the deleterious effects of vascular injuries similar to those that occur during PTCA and related procedures.

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.

A genetically modified adenoviral vector exhibits enhanced gene transfer of human smooth muscle cells

Adenoviral vector-based gene therapy is a promising approach for the treatment of restenosis postangioplasty. However, a high concentration of adenoviral vector can cause cellular activation, damage, and an enhanced immune response. One approach to solving this problem is to increase gene transfer efficiency by directing adenoviral vector entry via an alternate receptor system. We have constructed an adenoviral vector, Av9LacZ, that encodes the beta-galactosidase gene and contains a chimeric fiber protein that redirects viral vector binding to the Ad3 adenoviral receptor on the host cell. We examined the ability of Av9LacZ to transduce primary human smooth muscle cells (SMC) and found that it showed a 10- to 15-fold higher transduction efficiency when compared to the prototypic adenoviral vector currently used for preclinical and clinical studies. While both vectors were able to transduce rabbit, pig and monkey SMCs, the genetically modified vector transduced human SMC with much higher efficiency. SMC obtained from the aorta, coronary, renal, popliteal and pulmonary arteries were all efficiently transduced by Av9LacZ. Consistent with the data obtained from cultured cells, Av9LacZ also transduced fresh human arterial tissues considerably more efficiently than Av1LacZ. We conclude that the large discrepancy between transduction of animal and human cells by conventional vectors supports a cautious extrapolation of the results of in vivo animal studies to man. Furthermore, the genetically modified AV9 vector may deliver better efficacy and studies in large animal models with this vector could be more predictive of therapeutic efficacy in the treatment of human restenosis.

Stability of adenoviral vectors following catheter delivery

Adenoviral vectors have shown promise in a variety of preclinical vascular disease models. Intravascular infusion is one methodology to introduce the adenoviral vector into the affected area of the blood vessel. The biocompatibility of the infusion catheter with the adenoviral vector is key for successful local transfer. It has been recently suggested that catheter-based delivery of adenoviral vectors may result in the loss of vector infectivity. We demonstrate here a catheter capable of delivering adenoviral vectors without the loss of viral particle or infectious titers. First- (DeltaE1) and second- (DeltaE1/DeltaE4) generation adenoviral vectors were tested for their biocompatibility with the Crescendo microporous infusion catheter, which is designed for local infusion of therapeutic agents to human coronary or peripheral arteries. We found that incubation of either the DeltaE1 or the DeltaE1/DeltaE4 viral vectors for up to 30 min in the catheter at 37 degrees C did not result in a loss of viral particles or of viral infectivity. Here, we show that the Crescendo catheter is biocompatible with adenoviral vectors and suitable for vascular gene therapy.

Intracoronary, adenovirus-mediated Akt gene transfer in heart limits infarct size following ischemia-reperfusion injury in vivo

BACKGROUND

Previous data have shown that enhanced Akt signaling inhibits cardiac myocyte apoptosis in vitro and in vivo. To elucidate the contribution of apoptosis to the pathogenesis of the infarct, we investigated whether intra-coronary Akt gene delivery could reduce gross infarct size following ischemia/reperfusion injury.

METHODS AND RESULTS

Replication-defective adenoviral constructs encoding a myristoylated, constitutively-active form of Akt (myrAkt) or beta -galactosidase were delivered to rat hearts by intracoronary perfusion. Twenty-four h after gene transduction, hearts in both groups underwent 45 min of ischemia followed by 4 h of reperfusion. A third group of animals also underwent ischemia-reperfusion injury but were not transduced with an adenoviral vector. The proportion of the left ventricle at risk was not different among the experimental groups. However, infarct size as a proportion of the area at risk was significantly lower in myrAkt-treated group than in the beta -galactosidase treated group or in the control group that was not subject to intracoronary perfusion (myrAkt=20.9+/-2.7%v beta -galactosidase=56.1+/-3.9% and control=46.2+/-4.6%, P<0.05), as was infarct size as a proportion of the total left ventricle (myrAkt=11.4+/-3.2 v beta -galactosidase=32. 9+/-3.3 and control=23.5+/-3.0, P<0.05).

CONCLUSIONS

These data demonstrate that Akt signaling limits infarct size following ischemia/reperfusion injury and they indicate that the activation of this pathway may be useful in protecting against myocardial loss in the diseased heart.

Biodistribution of adenoviral vector to nontarget tissues after local in vivo gene transfer to arterial wall using intravascular and periadventitial gene delivery methods

Expression of transgene other than in the target tissue may cause side effects and safety problems in gene therapy. We analyzed biodistribution of transgene expression after intravascular and periadventitial gene delivery methods using the first generation nuclear-targeted lacZ adenovirus. RT-PCR and X-Gal stainings were used to study transgene expression 14 days after the gene transfer. After intravascular catheter-mediated gene transfer to rabbit aorta mimicking angioplasty procedure, the target vessel showed 1.1% +/- 0. 5 gene transfer efficiency. Other tissues showed varying lacZ gene expression indicating a systemic leakage of the vector with the highest transfection efficiency in hepatocytes (0.7% +/- 0.5). X-Gal staining of blood cells 24 h after the intravascular gene transfer indicated that a significant portion (1.8% +/- 0.8) of circulating monocytes was transfected. X-Gal-positive cells were also found in testis. After periadventitial gene transfer using a closed silicon capsule placed around the artery, 0.1% +/- 0.1 lacZ-positive cells were detected in the artery wall. Positive cells were also found in the liver and testis (<0.01%), indicating that the virus escapes even from the periadventitial space, although less extensively than during the intravascular application. We conclude that catheter-mediated intravascular and, to a lesser extent, periadventitial gene transfer lead to leakage of adenovirus to systemic circulation, followed by expression of the transgene in several tissues. Possible consequences of the ectopic expression of the transgene should be evaluated in gene therapy trials even if local gene delivery methods are used.