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

Recent advance in treatment of atherosclerosis: Key targets and plaque-positioned delivery strategies

Atherosclerosis, a chronic inflammatory disease of vascular wall, is a progressive pathophysiological process with lipids oxidation/depositing initiation and innate/adaptive immune responses. The coordination of multi systems covering oxidative stress, dysfunctional endothelium, diseased lipid uptake, cell apoptosis, thrombotic and pro-inflammatory responding as well as switched SMCs contributes to plaque growth. In this circumstance, inevitably, targeting these processes is considered to be effective for treating atherosclerosis. Arriving, retention and working of payload candidates mediated by targets in lesion direct ultimate therapeutic outcomes. Accumulating a series of scientific studies and clinical practice in the past decades, lesion homing delivery strategies including stent/balloon/nanoparticle-based transportation worked as the potent promotor to ensure a therapeutic effect. The objective of this review is to achieve a very brief summary about the effective therapeutic methods cooperating specifical targets and positioning-delivery strategies in atherosclerosis for better outcomes.

The transcription factor Foxf1 binds to serum response factor and myocardin to regulate gene transcription in visceral smooth muscle cells

Smooth muscle cells (SMCs) modulate their phenotype from a quiescent contractile state to a dedifferentiated, proliferative and migratory state during the pathogenesis of many diseases, including intestinal pseudoobstruction. Understanding how smooth muscle gene expression is regulated in these different phenotypic states is critical for unraveling the pathogenesis of these diseases. In the current study we examined the specific roles of Foxf1 in visceral SMC differentiation. Data show that Foxf1 is specifically required for expression of several contractile and regulatory proteins such as telokin, smooth muscle γ-actin, and Cav1.2b in visceral SMCs. Mechanistically, Foxf1 directly binds to and activates the telokin promoter. Foxf1 also directly binds to serum response factor (SRF) and myocardin-related transcription factors (MRTFs). Unlike Foxo4 and Foxq1, which bind to MRTFs and block their interaction with SRF, Foxf1 acts synergistically with these proteins to regulate telokin expression. Knock-out of Foxf1 specifically in SMCs results in neonatal lethality, with mice exhibiting GI tract abnormalities. Mice heterozygous for Foxf1 in SMC exhibited impaired colonic contractility and decreased expression of contractile proteins. These studies together with previous studies, suggest that different forkhead proteins can regulate gene expression in SMCs through modulating the activity of the SRF-myocardin axis to either promote or inhibit differentiation and proliferation thereby altering gastrointestinal contractility and development.

Inhibition of intimal hyperplasia after stenting by over-expression of p15: a member of the INK4 family of cyclin-dependent kinase inhibitors

We evaluated the role of p15(Ink4), a member of the INK4 family of CDK inhibitors on vascular smooth muscle cells (VSMCs) proliferation, cell cycle progression and intimal hyperplasia after stenting. Aortic VSMCs transduced with either adenovirus encoding for p15(Ink4) or β-galactosidase were assessed for DNA synthesis, cell cycle progression, and pRb phosphorylation. Rabbit carotid arteries were stented and treated with peri-adventitial delivery of saline or adenovirus encoding for p15(Ink4) or β-galactosidase. p15(Ink4) transgene and protein expression were evaluated at 24 h and 72 h, respectively. In-stent cell proliferation was evaluated by BrdU at day 7. Histomorphometric analysis of in-stent intimal hyperplasia was performed at 10 weeks. Human p15(Ink4) DNA was detected in transduced VSMCs at 24h. p15(Ink4) over-expression reduced VSMCs DNA synthesis by 60%. Cell cycle progression was inhibited, with a 30% increase in G1 population accompanied by inhibition of pRb phosphorylation. Human p15(Ink4) transgene was identified in transduced stented arteries but not in control arteries. p15(Ink4) immunostaining was increased and cell proliferation significantly reduced by 50% in p15(Ink4) transduced arteries. Intimal cross-sectional area (CSA) of p15(Ink4)-treated group was significantly lower than the β-gal treated and non-transduced groups (p=0.008). There were no differences in the intimal or medial inflammatory response between groups. p15(Ink4) over-expression blocks cell cycle progression leading to inhibition of VSMCs proliferation. Peri-adventitial delivery of p15(Ink4) significantly inhibits in-stent intimal hyperplasia.

Efficiency of drug delivery to the coronary arteries in swine is dependent on the route of administration: assessment of luminal, intimal, and adventitial coronary artery and venous delivery methods

PURPOSE

To compare the efficiency of five different drug delivery methods to the coronary artery in swine.

MATERIALS AND METHODS

A nanoparticle-albumin-bound, nonradioactive isotopic marker was administered within the left anterior descending coronary artery (LAD) through a microinfusion catheter (MIC: adventitial, n = 8, and luminal, n = 4), a porous drug infusion balloon (DIB: intimal, n = 4), and a straight catheter (SC: luminal, n = 2) and within the superior vena cava (SC: intravenous, luminal, n = 2). The distribution of the marker in heart, lung, liver, kidney, muscle, blood, urine, and bile was determined 68-84 minutes after delivery. The heart was sectioned into six axial slices and each slice divided into four quadrants. The marker content was assayed by neutron bombardment and the total counts of disintegrations per minute (DPM) expressed as a percentage of the control for each device delivery control.

RESULTS

After luminal delivery with the nonactuated MIC (MIC-NA) or intimal delivery with the DIB, 0.17% ± 0.07 and 0.39% ± 0.09, respectively, less than 0.39% of the total marker was detected in the heart. After adventitial delivery with the actuated MIC (MIC-A), 63.1% ± 9.9 of the total marker was detected in the heart. Marker was only detected in quadrants containing the coronary LAD, with the highest level in the middle slice and lower marker levels in consecutive proximal and distal heart slices. The nonactuated MIC-NA and DIB drug infusion balloon patterns of marker distribution were similar to those of actuated MIC-A, although with reduced levels. These delivery methods were also associated with considerably more marker detected in the lungs and liver: at least 22% compared with 1.34% ± 1.34 for the actuated MIC-A There was one delivery failure with the actuated MIC.

CONCLUSIONS

Catheter-based adventitial delivery with the MIC-A represents a more efficient delivery method for retention of vascular therapeutics.

PKCδ mediates anti-proliferative, pro-apoptic effects of testosterone on coronary smooth muscle

Sex hormone status has emerged as an important modulator of coronary physiology and cardiovascular disease risk in both males and females. Our previous studies have demonstrated that testosterone increases protein kinase C (PKC) δ expression and activity in coronary smooth muscle (CSMC). Because PKCδ has been implicated in regulation of proliferation and apoptosis in other cell types, we sought to determine if testosterone modulates CSMC proliferation and/or apoptosis through PKCδ. Porcine CSMC cultures (passages 2–6) from castrated males were treated with testosterone for 24 h. Testosterone (20 and 100 nM) decreased [3H]thymidine incorporation in proliferating CSMC to 59 ± 5.3 and 33.1 ± 4.5% of control. Flow cytometric analysis demonstrated that testosterone induced G1arrest in CSMC with a concomitant reduction in the S phase cells. Testosterone reduced protein levels of cyclins D1and E and phosphorylation of retinoblastoma protein while elevating levels of p21cip1and p27kip1. There were no significant differences in the levels of cyclins D3, CDK2, CDK4, or CDK6. Testosterone significantly reduced kinase activity of CDK2 and -6, but not CDK4, -7, or -1. PKCδ small interfering RNA (siRNA) prevented testosterone-mediated G1arrest, p21cip1upregulation, and cyclin D1and E downregulation. Furthermore, testosterone increased CSMC apoptosis in a dose-dependent manner, which was blocked by either PKCδ siRNA or caspase 3 inhibition. These findings demonstrate that the anti-proliferative, pro-apoptotic effects of testosterone on CSMCs are substantially mediated by PKCδ.

Targeting microspheres and cells to polyethylene glycol-modified biological surfaces

It has previously been demonstrated that damaged arterial tissue can be acutely modified with protein-reactive polyethylene glycol (PEG) to block undesirable platelet deposition. This concept might be expanded by employing PEG-biotin and its strong interaction with avidin for site-specific targeted delivery. Toward this end, cultured endothelial cells (ECs) were surface modified with PEG-biotin and the available biotin was quantified with flow cytometry. NeutrAvidin-coated microspheres and PEG-biotin modified ECs with NeutrAvidin as a bridging molecule were delivered under arterial shear stress to PEG-biotin modified ECs on a coverslip as well as scrape-damaged bovine carotid arteries. After incubation with a 10 mM solution for 1 min, 8 x 10(7) PEG-biotin molecules/EC were found and persisted for up to 120 h. Perfused microspheres adhered to NHS-PEG-biotin treated bovine carotid arteries with 60 +/- 16 microspheres/mm(2) versus 11 +/- 4 microspheres/mm(2) for control arteries (p < 0.015). Similarly, 22 +/- 5 targeted ECs/mm(2) adhered to NHS-PEG-biotin treated bovine carotid arteries versus 6 +/- 2 ECs/mm(2) for control arteries (p < 0.01). The targeting strategy demonstrated here might ultimately find application for drug delivery, gene therapy, or cell therapy where localization to specific labeled vascular regions is desired following catheter-based or surgical procedures.

Targeted high-efficiency, homogeneous myocardial gene transfer

Myocardial gene therapy continues to show promise as a tool for investigation and treatment of cardiac disease. Progress toward clinical approval has been slowed by limited in vivo delivery methods. We investigated the problem in a porcine model, with an objective of developing a method for high efficiency, homogeneous myocardial gene transfer that could be used in large mammals, and ultimately in humans. Eighty-one piglets underwent coronary catheterization for delivery of viral vectors into the left anterior descending artery and/or the great cardiac vein. The animals were followed for 5 or 28 days, and then transgene efficiency was quantified from histological samples. The baseline protocol included treatment with VEGF, nitroglycerin, and adenosine followed by adenovirus infusion into the LAD. Gene transfer efficiency varied with choice of viral vector, with use of VEGF, adenosine, or nitroglycerin, and with calcium concentration. The best results were obtained by manipulation of physical parameters. Simultaneous infusion of adenovirus through both left anterior descending artery and great cardiac vein resulted in gene transfer to 78+/-6% of myocytes in a larger target area. This method was well tolerated by the animals. We demonstrate targeted, homogeneous, high efficiency gene transfer using a method that should be transferable for eventual human usage.

Catheter-based adenovirus-mediated anti-monocyte chemoattractant gene therapy attenuates in-stent neointima formation in cynomolgus monkeys

We have previously demonstrated great benefit from anti-monocyte chemoattractant protein-1 (MCP-1) gene therapy by "systemic" transfer of an N-terminal deletion mutant of human MCP-1 (called 7ND) gene into skeletal muscle for treatment of restenosis and atherosclerosis. However, recent evidence suggests that "local" gene transfer may be a clinically relevant approach. We therefore tested the hypothesis that catheter-based adenovirus-mediated anti-MCP-1 gene therapy attenuates stent-associated neointima formation. Bare metal stents were implanted in iliac arteries of cynomolgus monkeys fed a high cholesterol diet. Immediately after the stenting procedure, normal saline or recombinant adenoviral vector containing LacZ or the 7ND gene was administered locally into the stenting site through a Remedy channel-delivery catheter. Compared to saline infusion or LacZ gene transfer, 7ND gene transfer markedly reduced inflammatory changes at an early stage and attenuated neointima formation after 4 weeks. This strategy also reduced the increased production of pro-inflammatory and growth-promoting factors such platelet-derived growth factor. No systemic adverse effects of 7ND gene transfer were detected. There were no significant differences in serum cholesterol levels among the three groups. These data suggest that catheter-based adenovirus-mediated anti-MCP-1 gene therapy may be a clinically relevant and feasible strategy for treatment of in-stent restenosis.

Radiofrequency-enhanced vascular gene transduction and expression for intravascular MR imaging-guided therapy: feasibility study in pigs

PURPOSE

To evaluate the feasibility of radiofrequency (RF)-enhanced vascular gene transduction and expression by using a magnetic resonance (MR) imaging-heating guidewire as an intravascular heating vehicle during MR imaging-guided therapy.

MATERIALS AND METHODS

The institutional committee for animal care and use approved the experimental protocol. The study included in vitro evaluation of the use of RF energy to enhance gene transduction and expression in vascular cells, as well as in vivo validation of the feasibility of intravascular MR imaging-guided RF-enhanced vascular gene transduction and expression in pig arteries. For in vitro experiments, approximately 10(4) vascular smooth muscle cells were seeded in each of four chambers of a cell culture plate. Next, 1 mL of a green fluorescent protein gene (gfp)-bearing lentivirus was added to each chamber. Chamber 4 was heated at approximately 41 degrees C for 15 minutes by using an MR imaging-heating guidewire connected to a custom RF generator. At day 6 after transduction, the four chambers were examined and compared at confocal microscopy to determine the efficiency of gfp transduction and expression. For the in vivo experiments, a lentivirus vector bearing a therapeutic gene, vascular endothelial growth factor 165 (VEGF-165), was transferred by using a gene delivery balloon catheter in 18 femoral-iliac arteries (nine artery pairs) in domestic pigs and Yucatan pigs with atherosclerosis. During gene infusion, one femoral-iliac artery in each pig was heated to approximately 41 degrees C with RF energy transferred via the intravascular MR imaging-heating guidewire, while the contralateral artery was not heated (control condition). At day 6, the 18 arteries were harvested for quantitative Western blot analysis to compare VEGF-165 transduction and expression efficiency between RF-heated and nonheated arterial groups.

RESULTS

Confocal microscopy showed gfp expression in chamber 4 that was 293% the level of expression in chamber 1 (49.6% +/- 25.8 vs 16.8% +/- 8.0). Results of Western blot analysis showed VEGF-165 expression for normal arteries in the RF-heated group that was 300% the level of expression in the nonheated group (70.4 arbitrary units [au] +/- 107.1 vs 23.5 au +/- 29.8), and, for atherosclerotic arteries in the RF-heated group, 986% the level in the nonheated group (129.2 au +/- 100.3 vs 13.1 au +/- 4.9).

CONCLUSION

Simultaneous monitoring and enhancement of vascular gene delivery and expression is feasible with the MR imaging-heating guidewire.

Cardiovascular Gene Therapy: Angiogenesis and Beyond

Recent advances in understanding the mechanisms of disease have produced many new targets for gene therapy. However, it has been difficult to convert these new insights into clinically useful applications. In the field of cardiovascular medicine, most clinical studies of gene therapy have focused on angiogenesis as a treatment for ischemia. Initial enthusiasm was supported by small, uncontrolled, phase 1 trials. However, several large efficacy studies have recently been published that have not shown clinically significant improvement, and a few well-publicized complications of gene therapy have cast a pall over the entire field. In this review, we will summarize specific technical aspects of cardiovascular gene therapy, examine the recent series of clinical studies, and explore the direction of future work for the principal cardiovascular diseases.

Enhanced Therapeutic Angiogenesis by Cotransfection of Prostacyclin Synthase Gene or Optimization of Intramuscular Injection of Naked Plasmid DNA

Background— Although clinical trials of therapeutic angiogenesis by angiogenic growth factors with intramuscular injection of naked plasmid DNA have been successful, there are still unresolved problems such as low transfection efficiency. From this viewpoint, we performed the following modifications: (1) combination with vasodilation using prostacyclin and (2) changing the agents or volume of naked plasmid DNA in vivo.

Methods and Results— First, we examined cotransfection of the VEGF gene with the prostacyclin synthase gene in a mouse hindlimb ischemia model. Cotransfection of the VEGF gene with the prostacyclin synthase gene resulted in a further increase in blood flow and capillary density compared with single VEGF gene. Similar results were obtained with other angiogenic growth factors, such as hepatocyte growth factor (HGF). Alternatively, we changed the injection volume of the solution of plasmid DNA. Luciferase activity was increased in a volume-dependent manner. An increase in injection volume at 1 site rather than separate injections at multiple sites resulted in high transfection efficiency, which suggests that transfection of naked plasmid DNA is mediated by pressure. Interestingly, treatment with hyperbaric oxygen increased the transfection efficiency. Finally, we also examined the effects of different solutions. Saline and PBS, but not water, achieved high transfection efficiency. In addition, sucrose solution but not glucose solution resulted in high luciferase activity.

Conclusions— Overall, angiogenesis might be enhanced by cotransfection of prostacyclin synthase gene or an increase in injection volume and osmotic pressure. These data provide important information for the clinical application of therapeutic angiogenesis to treat peripheral arterial disease.

Imaging of vascular gene therapy

Gene therapy is an exciting frontier in medicine today. Many genes have been shown to be useful for treatment of various vascular diseases, including chronic cardiac and limb ischemia syndromes, vasculoproliferative disorder, hypercholesterolemia, atherosclerosis, thrombosis, and hypertension. Precise delivery of genes into target vessels, efficient transfer of genes into vascular cells of the target, and prompt assessment of gene expression over time are three challenging tasks for successful vascular gene therapy. Thus, in vivo imaging methods that can be used to monitor gene delivery and localize gene expression are needed. Modern imaging techniques provide an opportunity to monitor and direct vascular gene therapy. Radiologists play a key role not only in developing and mastering endovascular genetic interventions but also in assessing the success of vascular gene therapy and directing further refinement of vascular gene therapy technology. This article provides an overview of the current status of imaging of vascular gene therapy.

Local adenoviral-mediated inducible nitric oxide synthase gene transfer inhibits neointimal formation in the porcine coronary stented model

In this study the effect of local adenoviral-mediated delivery of inducible nitric oxide synthase on restenosis was evaluated in a porcine coronary stented model. Local gene transfer of recombinant adenoviral vectors that encode human inducible nitric oxide synthase (AdiNOS) was tested. Control vector (AdNull) lacked a recombinant transgene. Endoluminal delivery of 1.0 x 10(11) adenoviral particles was accomplished in 45 s using the Infiltrator catheter (Interventional Technologies, San Diego, CA). Coronary stents were deployed, oversized by a ratio of 1.2:1, in the treated segments immediately after gene transfer. Fourteen animals were sacrificed at day 28 to evaluate the effects of iNOS gene transfer on morphometric indices, and 4 animals were sacrificed at day 4 for detection of human iNOS expression by RT-PCR. iNOS mRNA was detected in six of eight iNOS-transferred arteries, whereas no expression of human iNOS was detected in the nontarget arteries. Morphometric analysis showed that iNOS transfer significantly reduced neointimal formation (3.41 +/- 1.12 mm(2) vs 2.14 +/- 0.68 mm(2), P < 0.05). We concluded that efficient intramural adenovirus-mediated iNOS transfer can be achieved by using Infiltrator catheters. iNOS gene transfer significantly reduces neointimal hyperplasia following stent injury.

Applied gene therapy in preclinical models of vascular injury

Atherosclerosis remains the major cause of morbidity and mortality in Western countries. Atherothrombotic complications, including vascular occlusions and severe narrowing of nutrient blood vessels in the cerebral, coronary, or peripheral circulation, usually require invasive revascularization strategies. As molecular mediators contributing to these complications are being identified in more representative experimental injury models, and as gene transfer platforms and vectors acquire improved safety and efficacy profiles, there is ground for cautious optimism that gene-based interventions will likely reduce the clinical burden of these diseases. Increased generation of reactive oxygen species in diseased atherosclerotic vessels has been implicated in vasospasm, exaggerated neointima formation, and enhanced thrombosis. Ex vivo pressurized vascular gene transfer in venous bypass grafts using antisense oligonucleotides directed against cell-cycle control genes can modify the venous graft's phenotype and confer clinical benefit with improved long-term graft survival. Alternatively, percutaneous intra-arterial gene transfer is feasible, but at relatively low transgene expression levels. Although this may suffice in the case of secreted gene products with marked paracrine or bystander effects, including nitric oxide synthase and heme oxygenase-1, drug- and gene-eluting stents may provide the preferred future vehicle for well-controlled, quantifiable, and safe vascular gene transfer. Continued efforts to improve gene transfer technology in diseased human vessels and to increase our understanding of molecular targets are required before the full therapeutic potential of vascular gene therapy can be realized.

Adenovirus-mediated gene transfer to the transplanted piglet heart after intracoronary injection

BACKGROUND

The advent of cardiac gene therapy in clinical practice requires a more efficient and safer myocardial gene delivery in large animals. A new approach to adenovirus-mediated intracoronary gene transfer in the piglet, using a heterotopic heart transplantation model, was designed to maximize the duration of contact between the vector and the heart in noncoronary flow conditions.

METHODS

Recombinant adenoviruses harboring a nucleus-localized beta-galactosidase gene under the control of a viral promoter were injected into the coronary vessels of the harvested hearts at a dose ranging from 10(10) to 2 x 10(11) pfu. The graft was maintained for 75 min in saline solution and then implanted in the abdomen of recipients. Gene transfer to allografts was evaluated 4 days after grafting by immunohistochemical and enzymatic analysis of beta-galactosidase expression.

RESULTS

Transgene expression was detected in all cardiac areas and up to 64, 44, 32, and 15% of positive nuclei were estimated in the left ventricle wall in four animals out of eleven. In the remaining animals, transgene expression was focally distributed, mainly in the left ventricle wall. PCR analysis revealed the presence of adenoviral sequences, albeit minimal, in exposed organs such as the liver and lung.

CONCLUSIONS

This procedure demonstrated that direct intracoronary gene transfer can be achieved using an ex vivo gene transfer strategy.

Preexisting antiadenoviral immunity and regional myocardial gene transfer: modulation by nitric oxide

The utility of adenoviral vectors, currently used in cardiovascular gene transfer protocols, is limited by the brevity of transgene expression and by antiadenoviral immune responses. The effect of preexisting antiadenoviral immunity on intracardiac gene transfer or its modulation by nitric oxide is unknown. Adenoviral vectors, expressing the firefly luciferase gene (AdLuc) or the human nitric oxide synthase 3 (NOS3) gene (AdNOS3), were infused into the great cardiac vein of naive pigs or immunized pigs. Pigs were immunized by intravenous injection of control virus AdRR5 and the resulting neutralizing antibody titers (median, 1:178; p < 0.0001 vs. baseline) were similar to preexisting titers in 54% of randomly selected coronary artery bypass graft patients. In naive animals distribution of transgene expression in the left ventricular free wall was focal. In immunized pigs myocardial luciferase expression 3 days after AdLuc gene transfer was more than 1000-fold lower than in naive pigs, whereas no change in NOS3 transcript levels was detected after AdNOS3 gene transfer. Severe, grade III-IV mononuclear cell infiltration and myocyte apoptosis were observed in four of five AdLuc-infected, immunized animals, compared with low-level inflammation and apoptosis in five of six AdNOS3-infected pigs. Coinfusion of AdLuc and AdNOS3 in immunized pigs resulted in spatially colocalized transgene expression, reduced T cell-mediated inflammation, and myocyte apoptosis and was associated with 200-fold greater median reporter transgene expression levels in the subendocardium (1.0 x 10(3) light units [LU]/mg protein, n = 8, vs. 4.5 x 10(1) LU/mg protein in AdLuc- and AdRR5-coinfected pigs, n = 7, p = 0.02). Preexisting antiadenoviral immunity abrogates myocardial gene expression in pigs and is associated with severe inflammation and myocyte apoptosis. Intracardiac NOS3 gene transfer may reduce these barriers to adenovirus-mediated myocardial gene transfer.

Gene therapy for restenosis: current status

Atherosclerosis is a major cause of morbidity and mortality in Western world. Vascular occlusion caused by atherosclerosis usually requires invasive treatment, such as surgical bypass or angioplasty. However, bypass graft failure and restenosis limit the usefulness of these procedures, with 20% of patients needing a new revascularisation procedure within 6 months of angioplasty. Numerous pharmacological agents have been investigated for the prevention of restenosis but none has shown undisputed efficacy in clinical medicine. Gene transfer offers a novel approach to the treatment of restenosis because of easy accessibility of vessels and already existing gene delivery methods. It can be used to overexpress therapeutically important proteins locally without high systemic toxicity, and the therapeutic effect can be targeted to a particular pathophysiological event. Promising results have been obtained from many pre-clinical experiments using therapeutic genes or oligonucleotides to prevent restenosis. Early clinical trials have shown that plasmid- and adenovirus-mediated vascular gene transfers can be conducted safely and are well tolerated. Ex vivo gene therapy with E2F-decoy succeeded in reducing graft occlusion rate after surgical bypass in a randomised, double-blind clinical trial. In the future, further development of gene delivery methods and vectors is needed to improve the efficacy and safety of gene therapy. Also, better knowledge of vascular biology at the molecular level is needed to find optimal strategies and gene combinations to treat restenosis. Provided that these difficulties can be solved, gene therapy offers an enormous potential for clinical medicine in the future.

Can we prevent in-stent restenosis?

Nowadays stent placement has replaced balloon angioplasty as the most commonly performed percutaneous coronary interventional procedure, mainly because of its better acute and chronic outcome. As a result, in-stent restenosis (ISR) has become a widespread problem. The incidence of ISR varies from 10% to 50% and depends on the absence or presence of several risk factors, such as small vessel size, longer lesions, and diabetes. Intravascular ultrasound studies have demonstrated that ISR is mainly caused by neointimal proliferation; consequently, this pathologic process has become the target of many preventive and therapeutic approaches. This article provides an overview of such management strategies, highlighting the rather disappointing experiences with mechanical and systemic drug therapies; the relative merits and disadvantages of intracoronary radiation; and the exciting yet realistic promise, embodied by the recent advancements in drug-eluting stent technology, of potentially eradicating ISR in the near future.

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.

Development of safe and efficient novel nonviral gene transfer using ultrasound: enhancement of transfection efficiency of naked plasmid DNA in skeletal muscle

Although clinical trials of stimulation of angiogenesis by transfection of angiogenic growth factors using naked plasmid DNA or adenoviral vector have been successful, there are still unresolved problems for human gene therapy such as low transfection efficiency and safety. From this viewpoint, it is necessary to develop safe and efficient novel nonviral gene transfer methods. As therapeutic ultrasound induces cell membrane permeabilization, ultrasound irradiation might increase the transfection efficiency of naked plasmid DNA into skeletal muscle. Thus, we examined the transfection efficiency of naked plasmid DNA using ultrasound irradiation with echo contrast microbubble (Optison) in vitro and in vivo experiments. First, we examined the feasibility of ultrasound-mediated transfection of naked plasmid DNA into skeletal muscle cells. Luciferase plasmid mixed with or without Optison was transfected into cultured human skeletal muscle cells using ultrasound (1 MHz; 0.4 W(2)) for 30 s. Interestingly, luciferase activity was markedly increased in cells treated with Optison, while little luciferase activity could be detected without Optison (P < 0.01). Electron microscopy demonstrated the transient formation of holes (less than 5 microM) in the cell surface, which could possibly explain the rapid migration of the transgene into the cells. Next, we studied the in vivo transfection efficiency of naked plasmid DNA using ultrasound with Optison into skeletal muscle. Two days after transfection, luciferase activity in skeletal muscle transfected with Optison using ultrasound was significantly increased about 10-fold as compared with plasmid alone. Successful transfection was also confirmed by beta-galactosidase staining. Finally, we examined the feasibility of therapeutic angiogenesis using naked hepatocyte growth factor (HGF) plasmid in a rabbit ischemia model using the ultrasound-Optison method. Five weeks after transfection, the angiographic score and the number of capillary density in rabbits transfected with Optison using ultrasound was significantly increased as compared with HGF plasmid alone (P < 0.01), accompanied by a significant increase in blood flow and blood pressure ratio (P < 0.01). Overall, the ultrasound transfection method with Optison enhanced the transfection efficiency of naked plasmid DNA in vivo as well as in vitro. Transfection of HGF plasmid by the ultrasound-Optison method could be useful for safe clinical gene therapy to treat peripheral arterial disease without a viral vector system.

Coronary in-stent restenosis: current status and future strategies

In-stent restenosis (ISR) is a novel pathobiologic process, histologically distinct from restenosis after balloon angioplasty and comprised largely of neointima formation. As percutaneous coronary intervention increasingly involves the use of stents, ISR is also becoming correspondingly more frequent. In this review, we examine the available studies of the histology and pathogenesis of ISR, with particular reference to porcine and other animal models. An overview of mechanical treatments is then provided, which includes PTCA, directional coronary atherectomy and high speed rotational atherectomy. Radiation-based therapies are discussed, including a summary of current problems associated with this modality of treatment. Finally, novel strategies for the prevention of ISR are addressed, including novel developments in stents and stent coatings, conventional drugs, nucleic acid-based drugs and gene transfer. Until recently, limited pharmacologic and mechanical treatment options have been available for both treatment and prevention of ISR. However, recent advances in gene modification and gene transfer therapies and, more particularly, in local stent-based drug delivery systems make it conceivable that the incidence of ISR will now be seriously challenged.

Recombinant Semliki Forest virus as a vector system for fast and selective in vivo gene delivery into balloon-injured rat aorta

Previously, we demonstrated that recombinant Semliki Forest virus (SFV) vector rapidly and selectively transfers genes into cultured vascular smooth muscle cells (VSMC), leaving endothelial cells (EC) unaffected. From this, we hypothesized that recombinant SFV in vivo only transfers genes into the media of balloon-injured but not intact vessel, that gene expression in VSMC is fast, and that the specificity of SFV for VSMC is caused by specific binding sites. To address these hypotheses, we studied the time course of in vivo SFV-LacZ and Ad-LacZ expression in balloon-injured rat aorta. In addition, the fusion characteristics of fluorescent pyrene-labeled SFV were explored in cultured VSMC and EC. In intact aorta, no LacZ expression was found in the intima or media at 24 h. In contrast, in denuded aorta, LacZ expression was detected in as early as 12 h after incubation. LacZ expression was predominantly present in the media. Ad-LacZ expression started after 12 h, but was predominantly present in the adventitia. Ad-LacZ expression in the media started after 72 h. In vitro transfection with SFV showed that fusion was higher and, moreover, saturable in VSMC as compared with EC, indicating the presence of specific SFV binding sites on VSMC, but not EC. From this we conclude that in vivo selectivity of SFV in balloon-injured vessels is based on the removal of the endothelium, which results in accessibility of VSMC in the media that carry specific binding sites for the SFV vector.

Gene therapy for acute diseases

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

Catalytic oligodeoxynucleotides define a key regulatory role for early growth response factor-1 in the porcine model of coronary in-stent restenosis

Early growth response factor-1 (Egr-1) controls the expression of a growing number of genes involved in the pathogenesis of atherosclerosis and postangioplasty restenosis. Egr-1 is activated by diverse proatherogenic stimuli. As such, this transcription factor represents a key molecular target in efforts to control vascular lesion formation in humans. In this study, we have generated DNAzymes targeting specific sequences in human EGR-1 mRNA. These molecules cleave in vitro transcribed EGR-1 mRNA efficiently at preselected sites, inhibit EGR-1 protein expression in human aortic smooth muscle cells, block serum-inducible cell proliferation, and abrogate cellular regrowth after mechanical injury in vitro. These DNAzymes also selectively inhibit EGR-1 expression and proliferation of porcine arterial smooth muscle cells and reduce intimal thickening after stenting pig coronary arteries in vivo. These findings demonstrate that endoluminally delivered DNAzymes targeting EGR-1 may serve as inhibitors of in-stent restenosis.

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.

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.

Cell cycle in vasculoproliferative diseases: potential interventions and routes of delivery

Atherosclerosis and restenosis of epicardial vessels are among the greatest challenges facing the clinical cardiologist, and phenotypic modulation and proliferation of smooth muscle cells are major components of the vasculoproliferative response. Proliferation is regulated by the interplay of regulatory proteins at checkpoints in the cell cycle that alter cellular growth. Activation of the cell cycle and the genetic control of its progression are final common pathways in this process. Investigators have postulated that cell-cycle inhibition using drugs and genetic or physical methods has the potential to reverse or prevent the vasculoproliferative process. The current challenge is to translate in vitro data demonstrating the efficacy of cell-cycle inhibition to clinical trials. At present, the steps that must be taken to meet this goal are (1) to design methods of delivery of these agents to specific sites, (2) to identify appropriate cellular targets to elicit cell-cycle arrest, and (3) to improve the therapeutic ratio by minimizing potential side effects. This review discusses current concepts of the cell cycle, target-regulating mechanisms, and possible interventions in vasculoproliferative diseases. We also discuss ongoing clinical trials that use antiproliferative agents in the hope of limiting the course of these diseases, as well as the promise that antiproliferative therapy holds in the coming decade.

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.

Development of a device for the delivery of agents to bone during distraction osteogenesis

Various agents have been theoretically and experimentally implicated as mediators of distraction osteogenesis (DO). The purpose of this study was to develop a vehicle for the potential delivery of these factors to the region of the distraction site in an attempt to manipulate this biologic process. Three adult mongrel dogs (12 months old) had oblique osteotomies performed bilaterally through the gonial regions. In group I, the external distracter was affixed to the right hemimandible of two dogs (n = 2 hemimandibles) with cannulated pins (external diameter = 1.5 mm; lumen diameter = 1.0 mm; length = 60 mm), whereas the distracter on the left was affixed with standard, noncannulated pins of the same dimensions. In group II, cannulated pins were used to affix the external distracter to both hemimandibles (n = 2 hemimandibles) of a dog. The devices were activated after a 5-day latency period and were lengthened at a rate of 1 mm/day for 20 days. During the distraction period, 0.1 ml/d of sterile india ink was injected into the cannulated pins, after which the sterile stylet was replaced. The activation protocol was followed by 28 days of fixation (consolidation period). The hemimandibles from group I underwent removal of soft tissues, acetone fixation, and gross examination/photography, whereas the hemimandibles from group II were prepared for histologic evaluation (whole mount, hematoxylin and eosin staining). All dogs survived to the end of the study and demonstrated successful DO without evidence of complications. Hemimandibles in group I displayed evidence of india ink on both the lingual and buccal cortex around the cannulated pin site, in the regenerate and on the neocortices of the distracted segment. Hemimandibles of group II showed histologic evidence of the india ink being deposited densely around the cannulated pin site and extending in a radial fashion around the pin site into the regenerate. This study demonstrates for the first time a vehicle device for the delivery of an inert dye to the regenerate site during distraction osteogenesis. This vehicle offers the potential of delivery of various factors implicated in distraction osteogenesis (i.e., mitogens) in an attempt to alter this process and also substances (i.e., chemotherapy, antibiotics, etc.) for use in the treatment of various osteopathies.

Recent developments in gene therapy for cardiac disease

Cardiovascular[TRACE;del] disease is the leading cause of death in the US and world-wide. Advances in molecular biology and the human genome project have revealed opportunities for novel strategies for cardiac gene therapy. This review discusses general and specific aspects of gene transfer strategies in cardiac tissues. These include 1) the selection and/or optimization of the vector for gene transfer; 2) the identification of the target gene(s); 3) the use of cardiac-specific promoters; and 4) the use of an appropriate delivery system for administration. Currently, several vectors (e.g., viral and nonviral vectors) have been developed and many target genes have been identified (e.g., VEGF, FGF, beta-AR, etc.). Many investigations have provided experimental models for gene delivery systems but the most efficient cardiac gene transfer was obtained from intramyocardial injection or perfusion of explanted myocardium. The data available thus far have suggested favorable immediate effects following gene transfer, but long-term value of cardiac gene therapy has not been proven. Further refinements in appropriate vectors that provide cell or tissue selectivity and long-lasting effects are necessary as well as the development of minimally invasive procedures for gene transfer.

Percutaneous gene therapy using recombinant adenoviruses encoding human herpes simplex virus thymidine kinase, human PAI-1, and human NOS3 in balloon-injured porcine coronary arteries

Local intracoronary delivery of recombinant adenoviruses expressing anti-migratory or anti-proliferative proteins including human constitutive endothelial nitric oxide synthase (NOS3), plasminogen activator inhibitor 1 (PAI-1), or herpesvirus thymidine kinase (TK) (combined with ganciclovir) was used to prevent neointimal formation in porcine coronary arteries. After balloon injury of the left anterior descending (LAD) coronary artery, animals received an intramural injection of adenovirus (1.5 X 10(9) PFU) carrying either the NOS3 cDNA (AdCMVNOS3, n = 12), the PAI-1 cDNA (AdCMVPAI-1, n = 12), the TK cDNA (AdMLPItk, n = 12), or no cDNA (AdpL+, n = 12). After 28 days, morphometric analysis was performed on coronary sections from all segments demonstrating injury. The internal elastic lamina (IEL) fracture length normalized to the IEL perimeter (initial injury) and the neointimal area normalized to the vessel area (response to injury) were used to generate linear regression lines and calculate an index of stenosis for the respective treatment groups. The response to injury was significantly smaller in AdCMVNOS3- and AdMLPItk-infected animals than in AdpL+-infected animals (slopes = 0.86 +/- 0.05 and 0.69 +/- 0.07 versus 1.11 +/- 0.06, p < 0.005 and p < 0.0001, respectively) but not in AdCMVPAI-1-infected animals (slope = 1.26 +/- 0.04, p = 0.04). No viral shedding was observed and there was no acute systemic toxicity after gene transfer. An increase in neutralizing antibody titers against Ad vectors was observed without any detectable response to the transgene products (NOS3, PAI-1). Local gene transfer of NOS3 and TK may hold promise as a safe and effective adjunctive treatment to reduce neointimal formation after percutaneous coronary intervention in humans.

Biocompatibility of cardiovascular gene delivery catheters with adenovirus vectors: an important determinant of the efficiency of cardiovascular gene transfer

Gene therapy approaches hold promise for the treatment of a wide variety of cardiovascular diseases. Many strategies for cardiovascular gene therapy involve catheter-mediated vector delivery via intramyocardial injection, intracoronary infusion, or direct gene transfer into the vessel wall. Several different gene delivery catheters have been developed and utilized in preclinical and clinical studies of cardiovascular gene therapy. However, rigorous studies of the biocompatibility of these catheters with gene therapy vectors have not yet been reported. In this report, we have examined the compatibility of cardiovascular gene therapy catheters and catheter constituents with first-generation E1/E3-deleted adenovirus vectors. We show that (i) currently available catheters rapidly and efficiently inactivate adenovirus vector infectivity; (ii) this inactivation is mediated by a variety of commonly used catheter constituents including stainless steel, nitinol, and polycarbonate; (iii) catheter-mediated inactivation of adenovirus vectors can be prevented by preflushing catheters with solutions of serum albumin; and (iv) it is possible to identify a set of catheter materials that are compatible with current adenovirus vectors. These results underscore the importance of catheter/vector compatibility and suggest methods for increasing the efficiency of catheter-mediated cardiovascular gene therapy.