Pharmacokinetics of adenoviral vector-mediated gene delivery to vascular smooth muscle cells: modulation by poloxamer 407 and implications for cardiovascular gene therapy

Atrial Gene Painting in Large Animal Model of Atrial Fibrillation

Gene therapy appears promising as a targeted treatment of cardiac diseases. Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and also a major contributor to stroke, heart failure, and death. Mechanisms that initiate and sustain AF are associated with structural and electrophysiological remodeling in the whole atria. Selection of the appropriate gene delivery method is critical for transduction efficacy. The ideal gene delivery method to manage AF should provide widespread and sufficient exposure to the transgene in atria only that safely maintains the homeostasis of the heart without off-target expression. All these requirements can be achieved using atrial gene painting that is directly applied to the atrial epicardial surface. In this chapter, we present the advantages of atrial gene painting and the experimental method, as applied to a large animal model of AF.

Materials promoting viral gene delivery

Therapeutic viral gene delivery is an emerging technology which aims to correct genetic mutations by introducing new genetic information to cells either to correct a faulty gene or to initiate cell death in oncolytic treatments. In recent years, significant scientific progress has led to several clinical trials resulting in the approval of gene therapies for human treatment. However, successful therapies remain limited due to a number of challenges such as inefficient cell uptake, low transduction efficiency (TE), limited tropism, liver toxicity and immune response. To adress these issues and increase the number of available therapies, additives from a broad range of materials like polymers, peptides, lipids, nanoparticles, and small molecules have been applied so far. The scope of this review is to highlight these selected delivery systems from a materials perspective.

MicroRNA-365 promotes the contractile phenotype of venous smooth muscle cells and inhibits neointimal formation in rat vein grafts

The high rate of autologous vein graft failure caused by neointimal hyperplasia remains an unresolved issue in the field of cardiovascular surgery; therefore, it is important to explore new methods for protecting against neointimal hyperplasia. MicroRNA-365 has been reported to inhibit the proliferation of vascular smooth muscle cells (SMCs). This study aimed to test whether adenovirus-mediated miR-365 was able to attenuate neointimal formation in rat vein grafts. We found that miR-365 expression was substantially reduced in vein grafts following engraftment. In vitro, overexpression of miR-365 promoted smooth muscle-specific gene expression and inhibited venous SMC proliferation and migration. Consistent with this, overexpression of miR-365 in a rat vein graft model significantly reduced grafting-induced neointimal formation and effectively improved the hemodynamics of the vein grafts. Mechanistically, we identified that cyclin D1 as a potential downstream target of miR-365 in vein grafts. Specially, to increase the efficiency of miR-365 gene transfection, a 30% poloxamer F-127 gel containing 0.25% trypsin was mixed with adenovirus and spread around the vein grafts to increase the adenovirus contact time and penetration. We showed that adenovirus-mediated miR-365 attenuated venous SMC proliferation and migration in vitro and effectively inhibited neointimal formation in rat vein grafts. Restoring expression of miR-365 is a potential therapeutic approach for the treatment of vein graft failure. © 2019 IUBMB Life, 2019.

Matrix Mediated Viral Gene Delivery: A Review

Polymeric matrices inherently protect viral vectors from pre-existing immune conditions, limit dissemination to off-target sites, and can sustain vector release. Advancing methodologies in development of particulate based vehicles have led to improved encapsulation of viral vectors. Polymeric delivery systems have contributed to increasing cellular transduction, responsive release mechanisms, cellular infiltration, and cellular signaling. Synthetic polymers are easily customizable, and are capable of balancing matrix retention with cellular infiltration. Natural polymers contain inherent biorecognizable motifs adding therapeutic efficacy to the incorporated viral vector. Recombinant polymers use highly conserved motifs to carefully engineer matrices, allowing for precise design including elements of vector retention and responsive release mechanisms. Composite polymer systems provide opportunities to create matrices with unique properties. Carefully designed matrices can control spatiotemporal release patterns that synergize with approaches in regenerative medicine and antitumor therapies.

PEO-PPO-PEO Tri-Block Copolymers for Gene Delivery Applications in Human Regenerative Medicine-An Overview

Lineal (poloxamers or Pluronic^®) or X-shaped (poloxamines or Tetronic^®) amphiphilic tri-block copolymers of poly(ethylene oxide) and poly(propylene oxide) (PEO-PPO-PEO) have been broadly explored for controlled drug delivery in different regenerative medicine approaches. The ability of these copolymers to self-assemble as micelles and to undergo sol-to-gel transitions upon heating has endowed the denomination of “smart” or “intelligent” systems. The use of PEO-PPO-PEO copolymers as gene delivery systems is a powerful emerging strategy to improve the performance of classical gene transfer vectors. This review summarizes the state of art of the application of PEO-PPO-PEO copolymers in both nonviral and viral gene transfer approaches and their potential as gene delivery systems in different regenerative medicine approaches.

Adenovirus-Mediated Gene Transfer of microRNA-21 Sponge Inhibits Neointimal Hyperplasia in Rat Vein Grafts

Background:Vein graft failure due to neointimal hyperplasia remains an important and unresolved complication of cardiovascular surgery. microRNA-21 (miR-21) plays a major role in regulating vascular smooth muscle cell (VSMC) proliferation and phenotype transformation. Thus, the purpose of this study was to determine whether adenovirus-mediated miR-21 sponge gene therapy was able to inhibit neointimal hyperplasia in rat vein grafts.

Methods:Adenovirus-mediated miR-21 sponge was used to inhibit VSMC proliferation in vitro and neointimal formation in vivo. To improve efficiency of delivery gene transfer to the vein grafts, 20% poloxamer F-127 gel was used to increase virus contact time and 0.25% trypsin to increase virus penetration. Morphometric analyses and cellular proliferation were assessed for neointimal hyperplasia and VSMC proliferation.

Results:miR-21 sponge can significantly decrease the expression of miR-21 and proliferation in cultured VSMCs. Cellular proliferation rates were significantly reduced in miR-21 sponge-treated grafts compared with controls at 28 days after bypass surgery (14.6±9.4 vs 34.9±10.8%, P=0.0032). miR-21 sponge gene transfer therapy reduced the intimal/media area ratio in vein grafts compared with the controls (1.38±0.08 vs. 0.6±0.10, P<0.0001). miR-21 sponge treatment also improved vein graft hemodynamics. We further identified that phosphatase and tensin homolog (PTEN) is a potential target gene that was involved in the miR-21-mediated effect on neointimal hyperplasia in vein grafts.

Conclusions:Adenovirus-mediated miR-21 sponge gene therapy effectively reduced neointimal formation in vein grafts. These results suggest that there is potential for miR-21 sponge to be used to prevent vein graft failure.

PEO-PPO-PEO micelles as effective rAAV-mediated gene delivery systems to target human mesenchymal stem cells without altering their differentiation potency

Recombinant adeno-associated viral (rAAV) vectors are clinically adapted gene transfer vectors for direct human cartilage regenerative medicine. Their appropriate use in patients is still limited by a relatively low efficacy of vector penetration inside the cells, by the pre-existing humoral immune responses against the viral capsid proteins in a large part of the human population, and by possible inhibition of viral uptake by clinical compounds such as heparin. The delivery of rAAV vectors to their targets using optimized vehicles is therefore under active investigation. Here, we evaluated the possibility of providing rAAV to human bone marrow-derived mesenchymal stem cells (hMSCs), a potent source of cartilage regenerative cells, via self-assembled poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as linear poloxamers or X-shaped poloxamines. Encapsulation in poloxamer PF68 and poloxamine T908 polymeric micelles allowed for an effective, durable, and safe modification of hMSCs via rAAV to levels similar to or even higher than those noted upon direct vector application. The copolymers were capable of restoring the transduction of hMSCs with rAAV in conditions of gene transfer inhibition, i.e. in the presence of heparin or of a specific antibody directed against the rAAV capsid, enabling effective therapeutic delivery of a chondrogenic sox9 sequence leading to an enhanced chondrocyte differentiation of the cells. The present findings highlight the value of PEO-PPO copolymers as powerful tools for rAAV-based cartilage regenerative medicine.

STATEMENT OF SIGNIFICANCE

While recombinant adeno-associated viral (rAAV) vectors are adapted vectors to treat a variety of human disorders, their clinical use is still restricted by pre-existing antiviral immune responses, by a low efficacy of natural vector entry in the target cells, and by inhibition of viral uptake by clinically used compounds like heparin. The search for alternative routes of rAAV delivery is thus becoming a new field of investigation. In the present study, we describe the strong benefits of providing rAAV to human mesenchymal stem cells, a potent source of cells for regenerative medicine, encapsulated in polymeric micelles based on poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as novel, effective and safe delivery systems for human gene therapy.

Addition of pluronics® to reducible disulfide-bond-containing Pluronic®-PEI-SS specifically enhances circulation time in vivo and transfection efficiency in vitro

To improve the circulation time and transfection efficiency of the polyplexes used in gene delivery, a series of Pluronic®/Pluronic®F127-PEI-SS/pDNA complexes (PFPS/pDNA), based on the addition of different kinds of Pluronics® to the reducible disulfide-bonds-containing Pluronic®F127-PEI-SS/pDNA (FPS/pDNA) polyplexes, was prepared and evaluated in Bcap and Hela cells in vitro and in vivo. The addition of Pluronics® with molecular weights and hydrophilic-lipophilic balance (HLBs) different from that in the FPS/pDNA complex resulted in five PFPS(1-5)/pDNA complexes, and the correlation between the structure of the free Pluronic® and the properties of the PFPS/pDNA complexes was investigated. The addition of Pluronics® resulted in slightly larger or same-sized nanoparticles of PFPS/pDNA at a constant N/P ratio. The PFPS copolymer displayed strong stability against DNase I digestion and serum degradation. PFPS-4 containing added Pluronic® L35, with an intermediate HLB of 19, showed a much higher transfection efficiency and less cytotoxicity than FPS or PEI-25 kDa in vitro. PFPS-4 also exhibited a considerably longer blood circulation time than FPS or PEI-25 kDa in vivo in mice, indicating that the addition of an intermediate Pluronic® can enhance the transfection efficiency of gene delivery systems.

Evidence of DNA transfer across a model membrane by a neutral amphiphilic block copolymer

BACKGROUND

Neutral amphiphilic triblock copolymers have been shown to be efficient for gene transfection in vivo, especially by direct injection into the muscle. To contribute to a better understanding of the underlying mechanisms, in the present study, we investigated the properties of a poly(ethylene oxide-b-4-vinylpyridine) diblock copolymer as vector for nucleic acid transfer, with the particular aim of shedding some light on a possible mechanism explaining the internalization of DNA by the transfected cells.

METHODS

Complexation of plasmid DNA with the PEO-b-P4VP diblock copolymer was investigated by ethidium bromide exclusion and gel electrophoresis assays. Interaction of the copolymer with a lipid model membrane was evaluated by electrophysiological assays and quantification of plasmid DNA was performed by quantitative polymerase chain reaction. In vivo luciferase transfection assays were finally performed.

RESULTS

The diblock copolymer was found to poorly interact with DNA up to a mass ratio (copolymer/DNA) as high as 150. At a concentration of 36 µg/ml, it induced the formation of mainly transient (but sometimes permanent) pores and the formation of those pores allowed the translocation of plasmid DNA across the model membrane. However, only low transgene expression was obtained; the luciferase levels observed with the diblock being of the same order of magnitude as those observed with the corresponding PEO and P4VP homopolymers.

CONCLUSIONS

These results strongly suggest that gene transfection by neutral block copolymers may involve the formation of cellular pores; in addition, they also highlight that in vivo gene transfection requires the use of adequately soluble block copolymers.

Rapid titration of adenoviral infectivity by flow cytometry in batch culture of infected HEK293 cells

There is a constant and growing interest in exploitingadenoviruses as vectors for gene therapy when transientexpression of a therapeutic protein is necessary. Therequirement for an increased viral titre has prompted asearch for techniques by which this virus may be assayedwith greater speed and simplicity. Conventional plaqueassay for quantification of adenoviral vectors titre incurrent use is laborious and time-consuming (up to 14days). We report herein a method for the monitoring ofadenovirus expressing green fluorescent protein thatincorporates rapid and easy sample handling by means offlow cytometric analysis. Cells (HEK293) were infectedwith adenovirus at various multiplicity of infection(MOI), harvested 17 to 20 h post infection and analysedby flow cytometry. Assumptions were made that onefluorescent cell was infected by a single infectiousparticle at a relatively low MOI. The adenoviral titrewas subsequently estimated from cell analysis in arelatively short time. The results obtained with an E1-complementing cell line (HEK293) were compared with thatobtained using a non-complementing cell line (A549). APoisson distribution successfully modelled the profile ofinfection as a function of MOI. This provided a betterunderstanding of adenoviral infection at the earlieststage possible. Monitoring of GFP fluorescence and viruspropagation in a batch culture of infected cells wassubsequently used as a practical application of thevalidated method.

The roles of cell surface attachment molecules and coagulation Factor X in adenovirus 5-mediated gene transfer in pancreatic cancer cells

Transduction of 11 pancreatic cancer cell lines with a replication-deficient adenovirus 5 expressing enhanced green fluorescent protein (Ad5EGFP) was analyzed and variable EGFP levels were observed, ranging from <1% to ∼40% of cells transduced, depending on the cell line. Efficient Ad5EGFP transduction was associated mainly with higher levels of cell surface Coxsackie and adenovirus receptor (CAR) but not with expression of α(v)β(3) and α(v)β(5) integrins and was fiber dependent. Reduction of CAR by RNA interference resulted in a corresponding decrease in Ad5EGFP transduction. Pre-treatment of Ad5EGFP with blood coagulation Factor X increased virus entry even in the presence of low CAR levels generated by RNA interference, suggesting a potential alternative route of Ad5 entry into pancreatic cancer cells. Immunohistochemistry carried out on 188 pancreatic ductal adenocarcinomas and 68 matched controls showed that CAR was absent in 102 (54%) of adenocarcinomas, whereas moderate and strong staining was observed in 58 (31%) and 28 (15%) cases, respectively. Weak or absent CAR immunolabeling correlated with poor histological differentiation of pancreatic cancer. In normal tissue, strong immunolabeling was detected in islet cells and in the majority of inter- and intralobular pancreatic ducts.

Inhibition of smooth muscle cell migration and neointima formation in vein grafts by overexpression of matrix metalloproteinase-3

OBJECTIVE

Saphenous vein grafts suffer from neointima formation following bypass surgery. Matrix metalloproteinases (MMPs) play important roles in this process. We examined MMP-3 for its therapeutic potential to prevent smooth muscle cell migration and neointima formation in venous bypass grafts using adenovirus-mediated gene transfer.

METHODS

Human aortic smooth muscle cells (HASMC) were transduced with adenoviral vectors encoding ss-galactosidase (Ad.ssgal) [corrected] or human MMP-3 (Ad.hMMP-(3)), [corrected] and characterized for migration in the amniotic membrane stroma as an in vitro model of the vascular wall. Cholesterol-fed New Zealand white rabbits underwent jugular vein bypass grafting into carotid arteries. Before insertion, grafts were incubated ex vivo with either Ad.ssgal [corrected] or hMMP-3. Transgene expression was characterized by immunohistochemistry and in situ zymography. Grafts (n = 6) were explanted after 28 days and intimal hyperplasia was quantified.

RESULTS

Migration of HASMC was significantly reduced when transduced with Ad.hMMP-(3) [corrected] compared to controls (P < .001). Immunocytochemistry of Ad.hMMP-(3) [corrected] transduced venous grafts localized this protein to the intima. In situ-zymography showed increased MMP activity in the intima of Ad.hMMP-(3) [corrected] transfected grafts. Stenosis degree (P = .001), intima/media-ratio (P = .023) and lesion thickness (P = .003) were significantly reduced in grafts transduced with Ad.MMP-3 in comparison to controls. There was no difference inside control groups.

CONCLUSION

MMP-3 overexpression inhibits formation of intimal hyperplasia in arterialized vein grafts. Adenovirus mediated gene transfer of MMP-3 may be of clinical use to prevent vein graft stenosis following bypass surgery.

The poloxamer P85 is protective against Listeria monocytogenes invasion

Listeria monocytogenes remains an important foodborne pathogen, and strategies designed to decrease the susceptibility of selected patient populations to foodborne pathogens are therefore desirable. Our objective was to determine if the poloxamer P85 was protective against L. monocytogenes infection. Caco-2 cells were treated with 0.1% (w/v) P85 and challenged with 10(7) L. monocytogenes EGD for 1 hour. A standard gentamicin protection assay was performed to determine invasion differences between the experimental groups. Effects of P85 on the pathogen were studied by measuring bacterial growth and ATP concentrations. In a murine model of listeriosis, FVB mice were administered 150 mg/kg P85 or vehicle control 45 minutes prior to intragastric inoculation of 10(7) L. monocytogenes. Dissemination of the pathogen from the gastrointestinal tract to the liver and spleen was determined 24 hours after bacterial challenge. Pretreatment of Caco-2 cells with P85 significantly decreased L. monocytogenes invasion compared to controls. Repletion of ATP reversed the protective effects of P85. No changes in bacterial ATP or growth profile were detected in P85-treated bacteria. Administration of P85 to mice prior to infection led to decreased dissemination to the liver and spleen compared to vehicle-treated mice. P85 is protective against L. monocytogenes infection when administered prior to bacterial challenge. Modulation of host ATP levels appears to be crucial for the protective effects of P85.

Efficient in vivo catheter-based pericardial gene transfer mediated by adenoviral vectors

Adenoviral vectors are promising agents for a number of in vivo gene therapy applications including diseases of the heart and coronary vessels. Efficient intravascular gene transfer to specific sites has been achieved in occluded vessels, but otherwise is hampered by the effect of blood flow on localized vector uptake in the vessel wall. An alternative delivery approach to coronary arteries is the expression of diffusible gene products into the pericardial space surrounding the heart and coronary arteries. However, in vivo pericardial access is comparatively difficult and has been limited to surgical approaches. We hypothesized that efficient adenovirus-mediated gene expression in pericardial lining mesothelium could be achieved by transmyocardial vector delivery to the pericardium. To evaluate this concept, a hollow, helical-tipped penetrating catheter was used to deliver vector-containing fluid directly into the intrapericardial space. The catheter was introduced percutaneously in anesthetized mongrel dogs, advanced into the right ventricle, and the tip passed through the apical right ventricular myocardium under direct radiographic visualization until the open end of the catheter tip resided in the intrapericardial space. Adenoviral vectors expressing either nuclear-localizing beta-galactosidase, cytoplasmic luciferase, or secreted human alpha 1AT reporters (Av1nBg, Av1Lu, or Av1Aa, respectively) were instilled through the catheter into the intrapericardial space. Three days later the animals were sacrificed and reporter gene expression was evaluated in pericardium, epicardium, and multiple other tissues. In animals receiving Av1nBg, beta-galactosidase activity was evident in most of the pericardial lining endothelium, up to 100% in many areas. In animals receiving Av1Lu, luciferase reporter activity was abundant in pericardial tissues, but near-background levels were observed in other organs. In animals receiving Av1Aa, human alpha 1AT was abundant (16-29 mg/ml) in pericardial fluid, but was undetectable in serum. All animals tolerated the procedure well with no electrocardiographic changes and no clinical sequelae. These observations demonstrate highly efficient adenovirus vector delivery and gene transfer and expression in the pericardium and support the feasibility of localized gene therapy via catheter-based pericardial approaches. We suggest that the pericardial sac may serve as a sustained-release protein delivery system for the generation of desired gene products or their metabolites for diffusion into the epicardial region.

Polymers for viral gene delivery

BACKGROUND

The development of viral vectors capable of providing efficient gene transfer in diseased tissues without causing any pathogenic effects is pivotal for overcoming the many challenges facing gene therapy.

OBJECTIVE

Immune responses against viral vectors, inadequate gene expression and inefficient targeting to specific cells in vivo are some of the major problems limiting the clinical utility of viral gene therapy.

METHODS

This review will focus on recent progress in strategic polymer-based modifications to improve the performance and biocompatibility of a variety of viral vectors. We will discuss the preclinical development of four approaches involving injectable polymers, polyelectrolytes, polymer microspheres and polymer-virus conjugates.

RESULTS/CONCLUSION

Much progress has been made in creating 'hybrid' gene delivery vectors that combine the strengths of polymers and viruses. With further optimization, these hybrid vectors, which may be safer and more effective, are likely to succeed in clinical applications.

Coating of adeno-associated virus with reactive polymers can ablate virus tropism, enable retargeting and provide resistance to neutralising antisera

BACKGROUND

Copolymers based on poly-[N-(2-hydroxypropyl) methacrylamide] (HPMA) have been used previously to enable targeted delivery of adenovirus. Here we demonstrate polymer-coating techniques can also be used to modify and retarget adeno-associated virus (AAV) types 5 and 8.

METHODS

Three strategies for modifying transductional targeting of AAV were employed. The first involved direct reaction of AAV5 or AAV8 with amino-reactive HPMA copolymer. The second approach used carbodiimide (EDC) chemistry to increase the number of surface amino groups on the AAV5 capsid, thereby improving coating efficiency. In the third approach, the AAV5 genome was isolated from capsid proteins and delivered in a synthetic polyplex consisting of polyethylenimine (PEI) and HPMA.

RESULTS

Efficient covalent attachment of HPMA copolymer to AAV5 could only be achieved following modification of the virus with EDC. Coating inhibited sialic acid dependent infection and provided a platform for retargeting via new ligands, including basic fibroblast growth factor. Retargeted infection was shown to be partially resistant to neutralising antisera. Delivery of AAV5 genomes using PEI and HPMA was efficient and provided absolute control of tropism and protection from antisera. In contrast AAV8 could be reacted directly with HPMA copolymer and allowed specific retargeting via the epidermal growth factor receptor, but gave no protection against neutralising antisera.

CONCLUSIONS

Reactive HPMA polymers can be used to ablate the natural tropism of both AAV8 and EDC-modified AAV5 and enable receptor-specific infection by incorporation of targeting ligands. These data show transductional targeting strategies can be used to improve the versatility of AAV vectors.

IL-4 gene transfer to the small bowel serosa leads to intestinal inflammation and smooth muscle hyperresponsiveness

Intestinal mucosal inflammation can lead to altered function of the underlying smooth muscle, which becomes hyperreactive to most contractile stimuli. Through nematode parasite infection models, T helper type 2 (Th2) cytokines have been implicated in intestinal muscle dysfunction; however, the mechanisms involved and the relevance of these findings to other forms of intestinal inflammation are unclear. Through gene transfer, we explored whether the Th2 cytokine IL-4 can mediate changes in longitudinal muscle function in the context of an adenoviral infection. Following abdominal surgery on mice, control beta-galactosidase-encoding recombinant adenoviruses and IL-4-encoding adenoviruses were applied to the serosal surface of the jejunum, leading to infection of cells in the serosa and in the mesentery. Marker transgene expression lasted for 3 wk and was accompanied by the recruitment of macrophages, lymphocytes, and neutrophils into the peritoneal cavity and mild inflammation at the site of infection. IL-4 transgene expression led to a stronger inflammatory response characterized by tissue eosinophilia and increased numbers of peritoneal mast cells and plasma cells. Whereas control virus infection had no effect on intestinal muscle function, infection with the IL-4 virus led to significant jejunal muscle hypercontractility, evident by day 7 postinfection. This modulation of smooth muscle function was shown to be IL-4 specific, since the application of an IL-5-encoding adenovirus induced tissue eosinophilia but did not alter muscle function. These results highlight an important causal role for IL-4 in the pathological regulation of enteric smooth muscle function and identify a novel strategy for gene transfer to the intestine.

Polyethylene Glycol (Molecular Weight 400 DA) Vehicle Improves Gene Expression of Adenovirus Mediated Gene Therapy

PURPOSE

A significant limitation of adenoviral mediated suicide gene therapy is poor gene distribution in vivo. The choice of vehicle has been demonstrated to affect the level of adenoviral delivered gene transduction. We examined the hypotheses that 1) adenovirus suspended in PEG400 improves gene expression in the naïve canine prostate model, 2) improved transgene expression with PEG400 results in improved tumor control and 3) vehicle affects the initial adenoviral spread from a single intratumor injection.

MATERIALS AND METHODS

The magnitude and volume of gene expression were measured 24 hours following intraprostatic injection of adenovirus suspended in PEG400 (12.5% weight per volume) or saline as vehicle. Tumor growth delay was measured in mice bearing human tumor xenografts following the injection of adenovirus in PEG400 and saline. The initial spread of adenovirus was measured by confocal microscopy following a single injection of fluorescently labeled adenoviral particles in human tumor xenografts using each vehicle.

RESULTS

Adenovirus suspended in PEG400 provided an average of twice the level of gene expression in the canine prostate and significantly better tumor control relative to saline in preclinical tumor models (p = 0.046 and 0.036, respectively). The initial spread of adenovirus with PEG400 was superior to that of adenovirus in saline and the latter was largely limited to the needle tract.

CONCLUSIONS

Adenoviral gene therapy vectors suspended in PEG400 results in improved tumor control because of greater initial adenoviral spread, and the increased volume and magnitude of gene expression in vivo.

Transcriptional Activation of Gene Expression by Pluronic Block Copolymers in Stably and Transiently Transfected Cells

Amphiphilic block copolymers of poly(ethylene oxide) and poly(propylene oxide) (Pluronics) enhance gene expression, but the mechanism remains unclear. We examined the effects of Pluronics on gene expression in murine cell models (NIH3T3 fibroblasts, C2C12 myoblasts, and Cl66 mammary adenocarcinoma cells) transfected with luciferase and green fluorescent protein. Addition of Pluronics to stably or transiently transfected cells enhanced transcription of the reporter genes. mRNA levels of the heat-shock protein hsp68 were also increased, whereas a housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase, was unaffected. Fibroblast and myoblast cells transfected with PathDetect cis-Reporting System constructs were used to examine the involvement of the nuclear factor-kappaB (NF-kappaB) and activating protein-1 (AP-1) in Pluronics enhancement. Pluronics enhanced reporter gene expression controlled by NF-kappaB in both cell models. They also increased expression of a gene under AP-1 in a fibroblast cell line, but not in a myoblast cell line. Activation of the inflammation signaling pathway in myoblast cells by Pluronics was shown by increased IkappaB phosphorylation. No cytotoxicity was observed at doses of Pluronics at which gene expression was increased. Overall, these results indicate that Pluronics can increase the transcription of genes, in part, through the activation of selected stress signaling pathways.

Adenovirus type 5 intrinsic adsorption rates measured by surface plasmon resonance

Intrinsic adsorption rates of whole adenovirus type 5 (Ad5) onto a diethylaminoethyl (DEAE) anion exchange surface are measured for the first time by surface plasmon resonance (SPR). Fitting SPR sensorgrams to a two-compartment mass transport reaction model distinguishes intrinsic adsorption rates from slow diffusive Ad5 mass transport. Ad5 is a widely used viral vector for gene therapy that binds electrostatically to surfaces of cells and synthetics such as membranes, chromatographic resins, and glass. Increasing NaCl concentration from 4.8 to 14.4mM shifts binding of whole Ad5 from diffusion control to a regime where both sorption and diffusion affect binding. Intrinsic adsorption rates for Ad5-DEAE interaction are 16 times faster than intrinsic adsorption rates for Ad5 fiber knob interacting with soluble extracellular domain of coxsackievirus adenovirus receptors (s-CAR).

Promoter- and strain-selective enhancement of gene expression in a mouse skeletal muscle by a polymer excipient Pluronic P85

Amphiphilic triblock copolymers of ethylene oxide and propylene oxide (Pluronic) significantly enhanced expression of plasmid DNA in the skeletal muscle. In the presence of Pluronic P85 (P85) high levels of expression of a reporter gene (luciferase) were sustained for at least 40 days and the area under the gene expression curve increased by at least 10 times compared to the DNA alone. The effect of Pluronic depended on the strain of the mouse and the type of the promoter used. Thus, P85 enhanced luciferase expression by 17 to 19-fold in immunocompetent C57Bl/6 and Balb/c mice, while no enhancement was observed with athymic Balb/c nu/nu mice. Furthermore, P85 activated the expression of luciferase gene driven by CMV promoter, NFkappaB and p53 response elements. There was much less or no effect on the gene driven by SV40 promoter or AP1 and CRE response elements. Overall, the promoter selectivity suggested that Pluronic induced transcriptional activation of gene expression by activating the p53 and NFkappaB signaling pathways. In addition Pluronic increased the number of DNA copies and thus affected initial stages of gene transfer in a promoter selective manner.

Targeted modification of atrial electrophysiology by homogeneous transmural atrial gene transfer

BACKGROUND

Safe and effective myocardial gene transfer remains elusive. Heterogeneous ventricular gene delivery has been achieved in small mammals but generally with methods not readily transferable to the clinic. Atrium-specific gene transfer has not yet been reported. We hypothesized that homogeneous atrial gene transfer could be achieved by direct application of adenoviral vectors to the epicardial surface, use of poloxamer gel to increase virus contact time, and mild trypsinization to increase virus penetration.

METHODS AND RESULTS

We "painted" recombinant adenovirus encoding the reporter gene Escherichia coli beta-galactosidase directly onto porcine atria. Investigational variables included poloxamer use, trypsin concentration, and safety. Using the painting method, we modified the atrial phenotype with an adenovirus expressing HERG-G628S, a long-QT-syndrome mutant. Our results showed that application of virus with poloxamer alone resulted in diffuse epicardial gene transfer with negligible penetration into the myocardium. Dilute trypsin concentrations allowed complete transmural gene transfer. After trypsin exposure, echocardiographic left atrial diameter did not change. Left atrial function decreased on postoperative day 3 but returned to baseline by day 7. Tissue tensile strength was affected only in the 1% trypsin group. HERG-G628S gene transfer prolonged atrial action potential duration and refractory period without affecting ventricular electrophysiology.

CONCLUSIONS

We show complete transmural atrial gene transfer by this novel painting method. Adaptation of the method could allow application to other tissue targets. Use with functional proteins in the atria could cure or even prevent diseases such as atrial fibrillation or sinus node dysfunction.

Pluronic Block Copolymers for Gene Delivery

Amphiphilic block copolymers of poly(ethylene oxide) and poly(propylene oxide) called Pluronic or poloxamer are commercially available pharmaceutical excipients. They recently attracted considerable attention in gene delivery applications. First, they were shown to increase the transfection with adenovirus and lentivirus vectors. Second, they were shown to increase expression of genes delivered into cells using non-viral vectors. Third, the conjugates of Pluronic with polycations, were used as DNA-condensing agents to form polyplexes. Finally, it was demonstrated that they can increase regional expression of the naked DNA after its injection in the skeletal and cardiac muscles or tumor. Therefore, there is substantial evidence that Pluronic block copolymers can improve gene expression with different delivery routes and different types of vectors, including naked DNA. These results and possible mechanisms of Pluronic effects are discussed. At least in some cases, Pluronic can act as biological adjuvants by activating selected signaling pathways, such as NF-kappaB, and upregulating the transcription of the genes.

Polymer genomics: shifting the gene and drug delivery paradigms

Pluronic, the A-B-A amphiphilic block copolymers of poly(ethylene oxide) and poly(propylene oxide), can up-regulate the expression of selected genes in cells and alter genetic responses to antineoplastic agents in cancer. Two key new findings are discussed in relation to current drug and gene delivery strategies. First, these block copolymers alone and in combination with a polycation, polyethyleneimine, can up-regulate the expression of reporter genes in stably transfected cells. This underscores the ability of selected synthetic polymers to enhance transgene expression through a mechanism that augments improved DNA delivery into a cell. Second, although, when used alone, Pluronic is "genetically benign," when combined with an antineoplastic agent, doxorubicin, it drastically alters pharmacogenomic responses to this agent and prevents the development of multidrug resistance in breast cancer cells. Collectively, these studies propose the need for a thorough assessment of pharmacogenomic effects of polymer therapeutics to maximize the clinical outcomes and understand the pharmacological and toxicological effects of polymer-based drugs and delivery systems.

A new method for recombinant adeno-associated virus vector delivery to murine diaphragm

Genetically modified mice are important models for evaluation of potential gene therapies for human diseases. However, their small size often precludes the use of clinically feasible methods for vector delivery, therefore, alternative methods must be used. We have developed a gel-based method for delivery of recombinant adeno-associated virus vectors to the mouse diaphragm, an important target organ for many myopathic diseases. We hypothesized that delivery of vectors in a viscous solution would increase transduction by providing a longer exposure time to target cells. We demonstrate that gel-mediated delivery of rAAV serotypes 1, 2, and 5 results in higher transduction efficiencies than free vectors alone when administered in vivo to mouse diaphragms. We further establish greater tropism of rAAV1 vectors for the diaphragm compared to serotypes 2 and 5. This report describes a novel method for efficient delivery of rAAV vectors to the mouse diaphragm and is the first demonstration of gene transfer to the diaphragm using recombinant adeno-associated virus vectors.

Design of the Del-1 for Therapeutic Angiogenesis Trial (DELTA-1), a Phase II Multicenter, Double-Blind, Placebo-Controlled Trial of VLTS-589 in Subjects with Intermittent Claudication Secondary to Peripheral Arterial Disease

The objective of this phase II investigation is to assess the safety and efficacy of a plasmid mediated approach to induce angiogenesis/arteriogenesis with the angiomatrix protein Del-1 (developmentally regulated endothelial locus 1), in subjects with intermittent claudication (IC) secondary to peripheral arterial disease (PAD). VLTS-589 is an investigational nonviral therapeutic comprising a plasmid-expressing Del-1 formulated with poloxamer 188 (facilitating agent). One hundred subjects with bilateral PAD and IC will be randomized after careful screening to bilateral intramuscular delivery of VLTS-589 or placebo. A total of 84 mg of plasmid or placebo will be delivered as 42 intramuscular injections (2 ml per injection, 21 injections or 42 ml in each extremity of either plasmid or placebo) in both lower extremities. The subjects in the study will be followed at regular intervals for a year after study drug administration (days 30, 90, 180, and 365) with the primary endpoint being the safety and tolerability of VLTS-589 and change in peak walking time (PWT) at day 90. The secondary endpoints include percent and absolute change in resting ankle brachial Index, claudication onset time, and quality of life measured at various time points. DELTA-1 represents the largest plasmid-based gene transfer trial designed to test the efficacy of a Del-1 as a therapeutic approach in patients with IC caused by PAD. The novel aspects of the protocol include the usage of a Del-1 plasmid-polaxamer formulation to enhance gene transfer at doses that are an order of magnitude different than other comparable trials in a unique bilateral intramuscular dosing pattern to maximize transfection/clinical efficacy and general applicability to patients with PAD.

Determination of infectious retrovirus concentration from colony-forming assay with quantitative analysis

The colony formation assay is the most commonly used titration method for defining the concentration of replication-incompetent murine leukemia virus-derived retroviral vectors. However, titer varies with target cell type and number, transduction time, and concentration of polycation (e.g., Polybrene). Moreover, because most of the viruses cannot encounter target cells due to Brownian motion, their short half-lives, and the requirement for target cell division for activity, the actual infectious retrovirus concentration in the collected supernatant is higher than the viral titer. Here we correlate the physical viral particle concentration with the infectious virus concentration and colony formation titer with the help of a mathematical model. Ecotropic murine leukemia retrovirus supernatant, collected from the GP+E86/LNCX retroviral vector producer cell line, was concentrated by centrifugation and further purified by a sucrose density gradient. The physical concentration of purified viral vectors was determined by direct particle counting with an electron microscope. The concentrations of fresh and concentrated supernatant were determined by a quantitative reverse transcriptase activity assay. Titration of all supernatants by neomycin-resistant colony formation assay was also performed. There were 767 +/- 517 physical viral particles per infectious CFU in the crude viral supernatant. However, the infectious viral concentration determined by mathematical simulation was 143 viral particles per infectious unit, which is more consistent with the concentration determined by particle counting in purified viral solution. Our results suggest that the mathematical model can be used to extract a more accurate and reliable concentration of infectious retrovirus.

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.

Widespread regional myocardial transfection by plasmid encoding Del-1 following retrograde coronary venous delivery

This study quantifies myocardial transfection following percutaneous retrograde coronary venous delivery (RCVD) of a plasmid encoding human Del-1. RCVD of Del-1, GFP plasmid, or marker dye was conducted in 14 pigs. After selective cannulation of a coronary vein, a delivery site was confirmed by contrast injection and myocardial blush. Ten milliliters of plasmid hDel-1 or GFP was administered. Animals were euthanized 3 and 7 days post-RCVD. hDel-1 gene expression was evaluated by quantitative RT-PCR. An average myocardial expression of 4.5 x 10(5) copies hDel-1/microg total RNA was observed within the approximately 5 x 5 cm(2) target tissue of the left ventricle. GFP expression was detected by fluorescent microscopy. hDel-1 protein expression was confirmed by immunohistochemistry. Regionalized myocardial expression was found in all pigs. hDel-1 RNA was not found in distant tissues except in the three pigs with prominent venovenous washout (PVW). These levels were 3 to 4 log unites lower than those found in myocardium. Single retrograde coronary venous administration resulted in efficient regional myocyte transfection of hDel-1 and GFP. This method may be useful and clinically feasible for myocardial angiogenesis therapy.

Improved method of recombinant AAV2 delivery for systemic targeted gene therapy

A major hurdle in most current gene therapy modalities is the ability to transduce target tissues at very high efficiencies that ultimately lead to therapeutic levels of transgene expression. We have developed a novel method of recombinant adeno-associated virus 2 (rAAV) delivery that results in increased vector transduction efficiencies using microspheres reversibly conjugated to rAAV vectors. We hypothesize that conjugation to microspheres should result in a higher effective concentration of vector as well as longer relative exposure time of vector to target cells as it moves through the tissue vasculature. In vitro experiments demonstrate that the same level of transduction seen with free vector can be achieved using 1% of vector when conjugated to microspheres. In addition, using magnetic microspheres, the region of infection can be targeted. In vivo, we demonstrate that microsphere-mediated delivery of rAAV vector results in higher transduction efficiencies than delivery with free vector alone when administered either intramuscularly or intravenously. Furthermore, we demonstrate targeting of transgene expression to specific tissues by retention of microsphere-bound vector in the capillary bed. These studies demonstrate a novel method to deliver rAAV vectors more effectively that could prove to be a successful alternative mode of virus-mediated human gene therapy.

Transduction rate constant as more reliable index quantifying efficiency of retroviral gene delivery

Although the efficiency of retrovirus-mediated gene delivery can be enhanced by several physicochemical approaches reported (e.g., addition of polycations and spinoculation), systematic analysis of retroviral transduction combined with experimental data remains to be challenged. With the aid of a reasonable mathematical description of an experimental system, we can therefore predict and optimize the retroviral gene delivery on a quantitative basis of understanding. In this study, we formulated a mathematical model involved with diffusion, decay and uptake of retroviral vectors onto the target cells resided on a solid culture surface. The model was solved analytically by the Laplace transform method. The analytical solutions were then fitted with experimental data to compute two unknown parameters: concentration of infectious retrovirus and transduction rate constant. Our results showed that the concentration of infectious retrovirus determined by the titration method was approximately hundred-fold lower than the one calculated by fitting experimental data with the mathematical solutions. More importantly, effects of polycation (i.e., Polybrene) on ex vivo retroviral transduction were illustrated in a quantitative way by estimating the transduction rate constant, which represents a more reliable parameter to determine the degree of transduction of a retroviral vector to a given target cell.

Gene delivery to pig coronary arteries from stents carrying antibody-tethered adenovirus

Deployment of coronary stents to relieve atherosclerotic obstruction has benefitted millions of patients. However, gene therapy to prevent in-stent restenosis, while promising in experimental studies, remains a challenge. Conventional strategies for viral vector administration utilize catheters that deliver infusions of viral suspensions, which result in suboptimal localization and potentially dangerous distal spread of vector. Stent-based gene delivery may circumvent this problem. We hypothesized that site-specific delivery of adenoviral gene vectors from a stent could be achieved through a mechanism involving anti-viral antibody tethering. Stents were formulated with a collagen coating. Anti-adenoviral monoclonal antibodies were covalently bound to the collagen surface. These antibodies enabled tethering of replication defective adenoviruses through highly specific antigen-antibody affinity. We report for the first time successful stent-based gene delivery using antibody-tethered adenovirus encoding green fluorescent protein (GFP), demonstrating efficient and highly localized gene delivery to arterial smooth muscle cells in both cell culture and pig coronary arteries. Overall arterial wall transduction efficiency in pigs was 5.9 +/- 1.1% of total cells. However, neointimal transduction was more than 17% of total cells in this region. Importantly, when specific antibody was used to tether adenovirus, no distal spread of vector was detectable by PCR, in either distal organs, or in the downstream segments of the stented arteries. Control adenovirus stents, with nonspecific antibody plus adenovirus, demonstrated only a few isolated foci of transduction, and poor site-specific transduction with distal spread of vector. We conclude that a vascular stent is a suitable platform for a localizable viral vector delivery system that also prevents systemic spread of vector. Gene delivery using stent-based anti-viral antibody tethering of vectors should be suitable for a wide array of single or multiple therapeutic gene strategies.

Ectopic expression of the coxsackievirus and adenovirus receptor increases susceptibility to adenoviral infection in the human cervical cancer cell line, SiHa

The expression level of the coxsackievirus and adenovirus receptor (CAR) gene in human cervical cancer cell lines (Hela, Caski, HT-3, and SiHa) appears to be correlated with their susceptibility to adenoviral vector-based gene transfer. Hela, Caski, and HT-3 cells, which express the CAR molecule on the cell surface, showed a higher susceptibility to infection of AdCMVGFP than SiHa cells with no detectable level of CAR expression. Transient expression of the CAR gene in SiHa cells dramatically enhanced the susceptibility to adenoviral infection. Furthermore, SiHa-CAR, a stable transfectant which expresses the CAR gene showed a highly increased susceptibility to adenoviral infection in contrast to SiHa. These results demonstrate that the low susceptibility of SiHa to adenoviral infection is closely related to its loss of the CAR gene expression. In addition, the low infection efficacy can be overcome by the ectopic expression of the CAR gene. These results also give insight into a possible application of the CAR gene to adenovirus-mediated gene delivery.

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.

Improvement of gene transfer to cervical cancer cell lines using non-viral agents

Virus-like particles (VLPs) composed of recombinant capsid protein L1 and L2 of human papillomavirus type 16 were conjugated with polylysine (PL) and gene transfer was performed using VLP-PL conjugates to allow the expression of targeted gene. When HeLa cells were incubated with VLP-PL conjugate coupled with plasmid cytomegalovirus beta-galactosidase (pCMVbeta-gal), about 10% of cells were transfected and demonstrated beta-galactosidase activity. Hence chloramphenicol acetyltransferase activity was also expressed significantly in VLP-PL-plasmid simian virus 2 chloramphenicol acetyl transferase (pSV2CAT)-transfected cells, VLP-PL conjugate was tested whether it could transfer a tumor suppressor gene, pCMVp53, to HeLa cells and the exogenously provided p53 gene complexed to VLP-PL conjugate was detected from HeLa cells by polymerase chain reaction (PCR) analysis. Interestingly, additional increase of transfection efficiency was demonstrated in the presence of poloxamer 407 when C-33A cells were transfected with VLP-PL-pCMVbeta-gal complex. The result support the notion that VLP-PL conjugate may be a promising vector to transfer genetic materials into cancer cells and poloxamer 407 can be used for enhancing the transfection efficiency of VLP-PL conjugate.

Qualitative and quantitative determination of poloxamer surfactants by mass spectrometry

Poloxamers are polyethylene-polypropylene glycol linear co-polymers. A simple matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) method has been developed for the determination of the average molecular weight of poloxamers. The molecular mass of five standard poloxamers determined by MALDI closely corresponds to that specified by the manufacturers, and no mass distribution effects were observed. Quantitation of distributions based on the molecular mass envelope using electrospray (ES) ionization was unsuccessful. To overcome this problem, quantitation was based on fragment ions (m/z 45 and 59) which gave reproducible signals using a very high orifice voltage ( approximately 200 eV). Poloxamer concentrations were determined accurately with a good linear response using the standard addition method. We believe that the use of very small fragment ions for quantitation of polymers may become a widely applicable general technique.

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

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

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

Local delivery devices have been used for adenovirus-mediated gene transfer to the arterial wall for the potential treatment of vascular proliferative diseases. However, low levels of adenoviral gene expression in vascular smooth muscle cells may pose a serious limitation to the success of these procedures in the clinic. In this study, we examined the mechanisms controlling adenoviral transport to the vessel wall, using both hydrogel-coated and infusion-based local delivery catheters, with the goal of enhancing in vivo gene transfer under clinically relevant delivery conditions. The following delivery parameters were tested in vivo: applied transmural pressure, viral solution volume and concentration, and delivery time. We found that viral particles are transported into the vessel wall in a manner consistent with diffusion rather than pressure-driven convection. Consistent with diffusion, viral concentration was shown to be the key variable for viral transport in the vessel wall and thus gene expression in vascular smooth muscle cells. A transduction level of 17.8+/-3.2% was achieved by delivering a low volume of concentrated adenoviral beta-galactosidase solution through an infusion balloon catheter at low pressure without an adverse effect on medial cellularity. Under these conditions, effective gene transfer was accomplished within a clinically relevant time frame of 2 min, indicating that longer delivery times may not be necessary to achieve efficient gene transfer.

Evaluation of polyether-polyethyleneimine graft copolymers as gene transfer agents

Cationic copolymers consisting of polycations linked to non-ionic polymers are evaluated as non-viral gene delivery systems. These copolymers are known to produce soluble complexes with DNA, but only a few studies have characterized the transfection activity of these complexes. This work reports the synthesis and characterization of a series of cationic copolymers obtained by grafting the polyethyleneimine (PEI) with non-ionic polyethers, poly (ethylene oxide) (PEO) or Pluronic 123 (P123). The PEO-PEI conjugates differ in the molecular mass of PEI (2 kDa and 25 kDa) and the degree of modification of PEI with PEO. All of these conjugates form complexes upon mixing with plasmids, which are stable in aqueous dispersion for several days. The sizes of the particles formed in these systems vary from 70 to 200 nm depending on the composition of the complex. However, transfection activity of these systems is much lower than that of PEI (25 kDa) or Superfect as assessed in in vitro transfection experiments utilizing a luciferase reporter expression in Cos-7 cells as a model system. In contrast, conjugate of P123 with PEI (2 kDa) mixed with free P123 (9:1(wt)) forms small and stable complexes with DNA (110 nm) that exhibit high transfection activity in vitro. Furthermore, gene expression is observed in spleen, heart, lungs and liver 24 h after i.v. injection of this complex in mice. Compared to 1,2-bis(oleoyloxy)-(trimethylammonio) propane:cholesterol (DOTAP:Chol) and PEI (25 kDa) transfection systems, the P123-PEI system reveals a more uniform distribution of gene expression between these organs, allowing a significant improvement of gene expression in liver.

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

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

Cationic polymer and lipids enhance adenovirus-mediated gene transfer to rabbit carotid artery

BACKGROUND AND PURPOSE

Improvement of efficiency of gene transfer to endothelium could be useful for several applications. We tested the hypothesis that cationic nonviral molecules augment adenovirus-mediated gene transfer to blood vessels, perhaps by alteration of the surface charge of adenovirus and facilitation of binding to endothelium.

METHODS

Carotid arteries from rabbits were incubated in vitro for 0.5 to 2 hours with an adenoviral vector alone or noncovalent complexes of adenovirus with poly-L-lysine (a cationic polymer) or lipofectin (a cationic lipid). Binding of adenovirus to the vessels was evaluated immediately after incubation with virus, and assay of transgene (ss-galactosidase) activity and histochemistry were performed 24 hours after gene transfer. To determine whether cationic molecules can be used to augment alteration of vascular function by adenovirus-mediated gene transfer, we also examined effects on gene transfer of endothelial nitric oxide synthase.

RESULTS

Assay of ss-galactosidase activity indicated that both cationic molecules increased transgene expression in vessels by approximately 5- to 6-fold. In contrast, when endothelium was removed from the vessels after gene transfer, poly-L-lysine and lipofectin did not significantly increase transgene activity. Histochemistry for ss-galactosidase also suggested that the adenovirus-cationic molecule complexes augmented transgene expression mainly in the endothelium. In addition, we found that complexing adenovirus with cationic molecules increased binding of adenovirus to the vessels. After gene transfer with recombinant adenovirus containing endothelial nitric oxide synthase, calcium ionophore (A23187) produced greater relaxation of vessels treated with adenovirus complexed with poly-L-lysine or lipofectin than those treated with adenovirus alone.

CONCLUSIONS

Cationic molecules improve the efficiency of adenovirus-mediated gene transfer to blood vessels.

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

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

CONCLUSIONS

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

Plasmid delivery to muscle: Recent advances in polymer delivery systems

Preclinical studies involving intramuscular injection of plasmid into animals have revealed at least four significant variables that effect levels of gene expression (i.e., >fivefold effect over controls), including the formulation, injection technique, species and pretreatment of the muscle with myotoxic agents to induce muscle damage. The uptake of plasmid formulated in saline has been shown to be a saturable process, most likely via a receptor-mediated event involving the T tubules and caveolae. Pharmacokinetic studies have demonstrated that the bioavailability of injected plasmid to muscle cells is very low, due to rapid and extensive plasmid degradation by extracellular nucleases. We have developed protective, interactive, non-condensing (PINC) delivery systems designed to complex plasmids and to (i) protect plasmids from rapid nuclease degradation, (ii) disperse and retain intact plasmid in the muscle and (iii) facilitate the uptake of plasmid by muscle cells. PINC systems result in up to at least a one log increase in both the extent and levels of gene expression over plasmid formulated in saline. We have combined the PINC delivery systems with two different muscle-specific expression plasmids. After direct intramuscular injection of these gene medicines, we have shown both local myotrophic and neurotrophic effects of expressed human insulin-like growth factor (hIGF-I) and the secretion of biologically active human growth hormone (hGH) into the systemic circulation.