Non‐Viral Vectors for Gene Therapy: Clinical Trials in Cardiovascular Disease

Vascular reconstruction of the decellularized biomatrix for whole-organ engineering-a critical perspective and future strategies

Whole-organ re-engineering is the most challenging goal yet to be achieved in tissue engineering and regenerative medicine. One essential factor in any transplantable and functional tissue engineering is fabricating a perfusable vascular network with macro- and micro-sized blood vessels. Whole-organ development has become more practical with the use of the decellularized organ biomatrix (DOB) as it provides a native biochemical and structural framework for a particular organ. However, reconstructing vasculature and re-endothelialization in the DOB is a highly challenging task and has not been achieved for constructing a clinically transplantable vascularized organ with an efficient perfusable capability. Here, we critically and articulately emphasized factors that have been studied for the vascular reconstruction in the DOB. Furthermore, we highlighted the factors used for vasculature development studies in general and their application in whole-organ vascular reconstruction. We also analyzed in detail the strategies explored so far for vascular reconstruction and angiogenesis in the DOB for functional and perfusable vasculature development. Finally, we discussed some of the crucial factors that have been largely ignored in the vascular reconstruction of the DOB and the future directions that should be addressed systematically.

The Power of Field-Flow Fractionation in Characterization of Nanoparticles in Drug Delivery

Asymmetric-flow field-flow fractionation (AF4) is a gentle, flexible, and powerful separation technique that is widely utilized for fractionating nanometer-sized analytes, which extend to many emerging nanocarriers for drug delivery, including lipid-, virus-, and polymer-based nanoparticles. To ascertain quality attributes and suitability of these nanostructures as drug delivery systems, including particle size distributions, shape, morphology, composition, and stability, it is imperative that comprehensive analytical tools be used to characterize the native properties of these nanoparticles. The capacity for AF4 to be readily coupled to multiple online detectors (MD-AF4) or non-destructively fractionated and analyzed offline make this technique broadly compatible with a multitude of characterization strategies, which can provide insight on size, mass, shape, dispersity, and many other critical quality attributes. This review will critically investigate MD-AF4 reports for characterizing nanoparticles in drug delivery, especially those reported in the last 10-15 years that characterize multiple attributes simultaneously downstream from fractionation.

Safeguards for Using Viral Vector Systems in Human Gene Therapy: A Resource for Biosafety Professionals Mitigating Risks in Health Care Settings

Introduction

Health care workers who work daily with human body fluids and hazardous drugs are among those at the highest risk of occupational exposure to these agents. The Occupational Safety and Health Administration's (OSHA) Bloodborne Pathogens Standard (29 CFR 1910.1030) prescribes safeguards to protect workers against health hazards related to bloodborne pathogens. Similarly, the United States Pharmacopeia General Chapter 800 (USP <800>), a standard first published in February 2016 and implementation required by December 2019, addresses the occupational exposure risks of health care workers at organizations working with hazardous drugs. With emerging technologies in the field of gene therapy, these occupational exposure risks to health care workers now extend beyond those associated with bloodborne pathogens and hazardous drugs and now include recombinant DNA. The fifth edition of the Biosafety in Microbiological and Biomedical Laboratories (BMBL) and the National Institutes of Health Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules (NIH Guidelines) mostly govern work with biohazardous agents and recombinant DNA in a laboratory research setting. When gene therapy products are utilized in a hospital environment, health care workers have very few resources to identify and reduce the risks associated with product use during and after the administration of treatments.

Methods

At the Abigail Wexner Research Institute at Nationwide Children's Hospital, a comprehensive gap analysis was executed between the research and health care environment to develop a program for risk mitigation. The BMBL, NIH Guidelines, World Health Organization Biosafety Manual, OSHA Bloodborne Pathogens Standard, and USP <800> were used to develop a framework for the gap analysis process.

Results

The standards and guidelines for working with viral vector systems in a research laboratory environment were adapted to develop a program that will mitigate the risks to health care workers involved in the preparation, transportation, and administration of gene therapies as well as subsequent patient care activities. The gap analysis identified significant differences in technical language used in daily operations, work environment, training and education, disinfection practices, and policy development between research and health care settings. These differences informed decisions and helped the organization develop a collaborative framework for risk mitigation when a gene therapy product enters the health care setting.

Discussion

With continuing advances in the field of gene therapy, the oversight structure needs to evolve for the health care setting. To deliver the best outcomes to the patients of these therapies, researchers, Institutional Biosafety Committees, and health care workers need to collaborate on training programs to safeguard the public trust in the use of this technology both in clinical trials and as FDA-approved therapeutics.

Viral Vector Systems for Gene Therapy: A Comprehensive Literature Review of Progress and Biosafety Challenges

INTRODUCTION

National Institutes of Health (NIH) defines gene therapy as an experimental technique that uses genes to treat or prevent disease. Although gene therapy is a promising treatment option for a number of diseases (including inherited disorders, some types of cancer, and certain viral infections), the technique remains risky and is still under study to make sure that it will be effective and safe.

METHODS

Applications of viral vectors and nonviral gene delivery systems have found an encouraging new beginning in gene therapy in recent years. Although several viral vectors and nonviral gene delivery systems have been developed in the past 3 decades, no one delivery system can be applied in gene therapy to all cell types in vitro and in vivo. Furthermore, the use of viral vector systems (both in vitro and in vivo) present unique occupational health and safety challenges. In this review article, we discuss the biosafety challenges and the current framework of risk assessment for working with the viral vector systems.

DISCUSSION

The recent advances in the field of gene therapy is exciting, but it is important for scientists, institutional biosafety committees, and biosafety officers to safeguard public trust in the use of this technology in clinical trials and make conscious efforts to engage the public through ongoing forums and discussions.

Non-viral Vector for Muscle-Mediated Gene Therapy

Non-viral gene delivery to skeletal muscle was one of the first applications of gene therapy that went into the clinic, mainly because skeletal muscle is an easily accessible tissue for local gene transfer and non-viral vectors have a relatively safe and low immunogenic track record. However, plasmid DNA, naked or complexed to the various chemistries, turn out to be moderately efficient in humans when injected locally and very inefficient (and very toxic in some cases) when injected systemically. A number of clinical applications have been initiated however, based on transgenes that were adapted to good local impact and/or to a wide physiological outcome (i.e., strong humoral and cellular immune responses following the introduction of DNA vaccines). Neuromuscular diseases seem more challenging for non-viral vectors. Nevertheless, the local production of therapeutic proteins that may act distantly from the injected site and/or the hydrodynamic perfusion of safe plasmids remains a viable basis for the non-viral gene therapy of muscle disorders, cachexia, as well as peripheral neuropathies.

Regenerating the Anal Sphincter: Cytokines, Stem Cells, or Both?

BACKGROUND

Healing of an anal sphincter defect at a time distant from injury is a challenge.

OBJECTIVE

We aimed to investigate whether re-establishing stem cell homing at the site of an anal sphincter defect when cytokine expression has declined using a plasmid engineered to express stromal derived factor 1 with or without mesenchymal stem cells can improve anatomic and functional outcome.

DESIGN

This was a randomized animal study.

SETTINGS

Thirty-two female age- and weight-matched Sprague Dawley rats underwent 50% excision of the anal sphincter complex. Three weeks after injury, 4 interventions were randomly allocated (n = 8), including no intervention, 100-μg plasmid, plasmid and 800,000 cells, and plasmid with a gelatin scaffold mixed with cells.

MAIN OUTCOME MEASURES

The differences in anal sphincter resting pressures just before and 4 weeks after intervention were used for functional analysis. Histology was analyzed using Masson staining. One-way ANOVA followed by the Tukey post hoc test was used for pressure and histological analysis.

RESULTS

All 3 of the intervention groups had a significantly greater change in resting pressure (plasmid p = 0.009; plasmid + cells p = 0.047; plasmid + cells in scaffold p = 0.009) compared with the control group. The plasmid-with-cells group showed increased organization of muscle architecture and increased muscle percentage, whereas the control group showed disorganized architecture at the site of the defect. Histological quantification revealed significantly more muscle at the site of defect in the plasmid-plus-cells group compared with the control group, which had the least muscle. Quantification of connective tissue revealed significantly less fibrosis at the site of defect in the plasmid and plasmid-plus-cells groups compared with the control group.

LIMITATIONS

Midterm evaluation and muscle morphology were not defined.

CONCLUSIONS

At this midterm follow-up, local delivery of a stromal derived factor 1 plasmid with or without local mesenchymal stem cells enhanced anal sphincter muscle regeneration long after an anal sphincter injury, thereby improving functional outcome. See Video Abstract at http://links.lww.com/DCR/A324.

Impact of transduction towards the proliferation and migration as well as the transduction efficiency of human umbilical cord-derived late endothelial progenitor cells with nine recombinant adeno-associated virus serotypes

OBJECTIVES

To evaluate the transduction efficiency of human umbilical cord-derived, late endothelial progenitor cells late (HUCB-late EPCs) with nine recombinant adeno-associated virus (rAAV) serotypes and the ability of proliferation and migration of the cells after transduction.

RESULTS

rAAV2 and rAAV6 showed a greater ability than other serotypes to transduce late EPCs (P < 0.05). After transduction, cell proliferation ability weakened (P < 0.05), but the ability of migration to stromal cell-derived factor (SDF-1) unchanged.

CONCLUSION

There is an advantage of choosing the optimal rAAV serotype as a gene vector to alter the biologic characteristics of late EPCs.

Functional and pathological improvements of the hearts in diabetes model by the combined therapy of bFGF-loaded nanoparticles with ultrasound-targeted microbubble destruction

Diabetic cardiomyopathy (DCM) is the leading cause of morbidity and mortality among the diabetic patients and currently there is no effective means to reverse its pathological progress. Basic fibroblast growth factor (bFGF) has shown promise as a molecular therapy for DCM, but its delivery is inefficient and non-specific. In the present study, a therapy combining nanoparticle (NP) carrier and ultrasound-targeted microbubble destruction (UTMD) was reported the first time for bFGF delivery to the heart of diabetic rats. bFGF-loaded NP (bFGF-NP) were prepared with Poloxamer 188-grafted heparin copolymer using water-in-water technique, and the morphology, encapsulation efficiency, and bioactivity of bFGF-NP were studied. The cellular uptake and cytotoxicity of bFGF-NP were evaluated with primary cultures of the left ventricular (LV) cardiomyocytes in vitro. Therapeutic effects of bFGF-NP/UTMD on the heart of DCM rats were studied by measuring LV systolic and diastolic functions, hemodynamic characteristics and indicators of cardiac remodeling including myocardial collagen volume fraction and capillary density. Results demonstrated that bFGF-NP showed good round morphology, efficient bFGF encapsulation and stable bioactivity of bFGF in vitro. bFGF-NP/UTMD combined treatment significantly enhanced the efficiency of bFGF cellular uptake (P<0.05) without obvious cytotoxicity. Significant improvements (P<0.05) in both cardiac functions and tissue morphology in the DCM rats were observed in bFGF-NP/UTMD group. These were not achievable using free bFGF, bFGF-NP or UTMD treatment alone. Our results show that combining a non-viral vector with UTMD technique is an effective strategy to deliver bFGF to the heart, and the resulting growth factor therapy has demonstrated potential to reverse the progress of DCM by restoring the cardiac functions and even the structure of damaged cardiac tissues.

Gene therapy for heart disease: molecular targets, vectors and modes of delivery to myocardium

Despite the numerous hurdles that gene therapy has encountered along the way, clinical trials over the last few years are showing promising results in many fields of medicine, including cardiology, where many targets are moving toward clinical development. In this review, the authors discuss the current state of the art in terms of clinical and preclinical development. They also examine vector technology and available vector-delivery strategies.

From bench to bedside: review of gene and cell-based therapies and the slow advancement into phase 3 clinical trials, with a focus on Aastrom's Ixmyelocel-T

There is a large body of preclinical research demonstrating the efficacy of gene and cellular therapy for the potential treatment of severe (limb-threatening) peripheral arterial disease (PAD), including evidence for growth and transcription factors, monocytes, and mesenchymal stem cells. While preclinical research has advanced into early phase clinical trials in patients, few late-phase clinical trials have been conducted. The reasons for the slow progression of these therapies from bench to bedside are as complicated as the fields of gene and cellular therapies. The variety of tissue sources of stem cells (embryonic, adult bone marrow, umbilical cord, placenta, adipose tissue, etc.); autologous versus allogeneic donation; types of cells (hematopoietic, mesenchymal stromal, progenitor, and mixed populations); confusion and stigmatism by the public and patients regarding gene, protein, and stem cell therapy; scaling of manufacturing; and the changing regulatory environment all contribute to the small number of late phase (Phase 3) clinical trials and the lack of Food and Drug Administration (FDA) approvals. This review article provides an overview of the progression of research from gene therapy to the cellular therapy field as it applies to peripheral arterial disease, as well as the position of Aastrom's cellular therapy, ixmyelocel-T, within this field.

Adipose-derived stem cells promote angiogenesis and tissue formation for in vivo tissue engineering

Adult mesenchymal stem cells secrete a variety of angiogenic cytokines and growth factors, so we proposed that these paracrine mechanisms may be used to promote vascularization and growth for tissue engineering in vivo. We tested whether or not human adipose-derived stem cells (ASCs) promote tissue formation in rats. ASCs were evaluated in vitro for mRNA expression of angiogenic factors, including the vascular endothelial growth factor, basic fibroblast growth factor, interleukin-8 (IL-8), and stromal cell-derived factor-1 (SDF-1) and proliferative activity on human microvascular endothelial cells. For in vivo analysis, CM-DiI-labeled ASCs were implanted with a rat cardiac extracellular matrix (ECM) extract-derived hydrogel into a chamber with a femoral arteriovenous loop in the groin of male nude rats for 7 days. Vascularization in newly generated tissue was estimated by histomorphometry after endothelial nitric oxide synthase (eNOS) immunostaining. ASCs expressed growth factor mRNA and produced an angiogenic activity in vitro. After implantation, ASCs survived, but remained suspended in the ECM and relatively few were incorporated into the newly formed tissue. The volume of newly generated tissue was significantly higher in chambers containing ASCs and it was enriched with vasculature when compared with the ECM alone. We conclude that human ASCs promote tissue growth and angiogenesis in the rat vascularized chamber, thereby showing promise for tissue-engineering applications for regenerative therapy.

An open-label dose escalation study to evaluate the safety of administration of nonviral stromal cell-derived factor-1 plasmid to treat symptomatic ischemic heart failure

RATIONALE

Preclinical studies indicate that adult stem cells induce tissue repair by activating endogenous stem cells through the stromal cell-derived factor-1:chemokine receptor type 4 axis. JVS-100 is a DNA plasmid encoding human stromal cell-derived factor-1.

OBJECTIVE

We tested in a phase 1, open-label, dose-escalation study with 12 months of follow-up in subjects with ischemic cardiomyopathy to see if JVS-100 improves clinical parameters.

METHODS AND RESULTS

Seventeen subjects with ischemic cardiomyopathy, New York Heart Association class III heart failure, with an ejection fraction ≤40% on stable medical therapy, were enrolled to receive 5, 15, or 30 mg of JVS-100 via endomyocardial injection. The primary end points for safety and efficacy were at 1 and 4 months, respectively. The primary safety end point was a major adverse cardiac event. Efficacy end points were change in quality of life, New York Heart Association class, 6-minute walk distance, single photon emission computed tomography, N-terminal pro-brain natruretic peptide, and echocardiography at 4 and 12 months. The primary safety end point was met. At 4 months, all of the cohorts demonstrated improvements in 6-minute walk distance, quality of life, and New York Heart Association class. Subjects in the 15- and 30-mg dose groups exhibited improvements in 6-minute walk distance (15 mg: median [range]: 41 minutes [3-61 minutes]; 30 mg: 31 minutes [22-74 minutes]) and quality of life (15 mg: -16 points [+1 to -32 points]; 30 mg: -24 points [+17 to -38 points]) over baseline. At 12 months, improvements in symptoms were maintained.

CONCLUSIONS

These data highlight the importance of defining the molecular mechanisms of stem cell-based tissue repair and suggest that overexpression of stromal cell-derived factor-1 via gene therapy is a strategy for improving heart failure symptoms in patients with ischemic cardiomyopathy.

Human hepatocyte growth factor (VM202) gene therapy via transendocardial injection in a pig model of chronic myocardial ischemia

BACKGROUND

Hepatocyte growth factor (HGF) may stimulate angiogenesis. We examined the safety and therapeutic potential of the HGF plasmid (VM202) in pigs with chronic myocardial ischemia.

METHODS AND RESULTS

We delivered VM202 or vehicle transendocardially to 4 groups of pigs: vehicle control (n = 9); high-dose VM202 (n = 9); low-dose VM202 (n = 3); and normal control (no ischemia; n = 1). Pigs were killed 3, 30, and 60 days after injection. No adverse events were associated with VM202 treatment or delivery. Quantitative polymerase chain reaction indicated that heart injection sites had the highest levels of VM202 (day 3), which became almost undetectable by 30-60 days. Most nontarget tissues showed clearance of VM202 plasmid by day 30. Control and VM202-treated pigs did not differ in global functional data. Dobutamine-stressed myocardial-contrast echocardiogram suggested that VM202 may help preserve microvascular perfusion at 30 days; reperfusion velocity in ischemic myocardium decreased significantly in control (baseline to follow-up, 5.1 ± 1.9 to 2.7 ± 1.0; P = .031) but not in VM202 groups (high-dose: 3.1 ± 1.1 vs 3.1 ± 1.5 [P = .511]; low-dose: 3.8 ± 1.1 vs 3.9 ± 1.5 [P = .559]). Linear local shortening increased significantly from day 0 to 30 in VM202-treated versus control pigs (5.0 ± 4.7% vs 9.2 ± 7.5% vs 0.9 ± 5.8% [high-dose, low-dose, control, respectively]; P = .021).

CONCLUSIONS

Transendocardial delivery of VM202 was safe and may help to preserve microcirculatory perfusion and improve wall motion.

Plasmid-based transient human stromal cell-derived factor-1 gene transfer improves cardiac function in chronic heart failure

We previously demonstrated that transient stromal cell-derived factor-1 alpha (SDF-1) improved cardiac function when delivered via cell therapy in ischemic cardiomyopathy at a time remote from acute myocardial infarction (MI) rats. We hypothesized that non-viral gene transfer of naked plasmid DNA-expressing hSDF-1 could similarly improve cardiac function. To optimize plasmid delivery, we tested SDF-1 and luciferase plasmids driven by the cytomegalovirus (CMV) promoter with (pCMVe) or without (pCMV) translational enhancers or α myosin heavy chain (pMHC) promoter in a rodent model of heart failure. In vivo expression of pCMVe was 10-fold greater than pCMV and pMHC expression and continued over 30 days. We directly injected rat hearts with SDF-1 plasmid 1 month after MI and assessed heart function. At 4 weeks after plasmid injection, we observed a 35.97 and 32.65% decline in fractional shortening (FS) in control (saline) animals and pMHC-hSDF1 animals, respectively, which was sustained to 8 weeks. In contrast, we observed a significant 24.97% increase in animals injected with the pCMVe-hSDF1 vector. Immunohistochemistry of cardiac tissue revealed a significant increase in vessel density in the hSDF-1-treated animals compared with control animals. Increasing SDF-1 expression promoted angiogenesis and improved cardiac function in rats with ischemic heart failure along with evidence of scar remodeling with a trend toward decreased myocardial fibrosis. These data demonstrate that stand-alone non-viral hSDF-1 gene transfer is a strategy for improving cardiac function in ischemic cardiomyopathy.

Adult stem cells: from new cell sources to changes in methodology

Cardiovascular diseases constitute the first cause of mortality and morbidity worldwide. Alternative treatments like transplantation of (stem) cell populations derived from several adult tissue sources, like the bone marrow, skeletal muscle, or even adipose tissue, have been already employed in diverse clinical trials. Results from these studies and previous animal studies have reached to the conclusion that stem cells induce a benefit in the treated hearts, which is exerted mainly through paracrine mechanisms and not through direct differentiation as it was initially expected. However, a strong technical limitation for the stem cell therapy, which is the low level of cell survival and engraftment, diminishes their potential. Thus, new strategies like combination of the cells with bioengineering techniques have been developed and are being subject of intense research, suggesting that new strategies may improve the efficacy of these therapies. In this review, we will discuss the different therapeutic approaches, drawbacks, and future expectations of new regenerative therapies for cardiovascular diseases.

Naked DNA delivery to whole pig cardiac tissue by coronary sinus retrograde injection employing non-invasive catheterization

BACKGROUND

Hydrodynamic injection has demonstrated to be very efficient in the liver of small animals, although this procedure must be translated to the clinical practice in a milder but no less efficient way. The present study evaluates the capacity of non-invasive interventional catheterization as a procedure for naked DNA delivery to the heart in large animals.

METHODS

Two catheters were placed in the coronary sinus: one of them to block blood circulation and the other to retrogradely inject 50 ml of a saline solution of DNA (20 µg/ml) containing the enhanced green fluorescent protein (EGFP) gene, at a flow rate of 5 ml/s.

RESULTS

The results obtained show that EGFP protein, identified by immunohistochemistry, was present and widely distributed throughout the atrial and ventricular cardiac tissue. This observation agrees with the efficiency of EGFP gene delivery resulting in 1-200 EGFP gene copies per endogenous haploid genome. However, the transcription efficiency of the exogenous EGFP gene was at a ratio of 0.2-10 copies with respect to the endogenous GAPDH gene, suggesting that optimized gene constructs for expression in cardiac tissue could increase the final efficacy of gene transfer.

CONCLUSIONS

We conclude that the retrovenous injection of naked DNA in the coronary sinus employing the catheterization technique is an easy and probably safe method for whole cardiac gene transfer.

Transgene expression in mononuclear muscle cells not infiltrating inflammatory cells following intramuscular plasmid gene electrotransfer

BACKGROUND

In situ electroporation-assisted intramuscular plasmid DNA delivery offers high efficiency for therapeutic protein replacement. Expression may be impaired by an immune response against the plasmid or transgenic protein. Expression of the transgene in non-muscle cells may increase the immune response. Gene transfer efficiency and phenotypic identification of intramuscular transgene-expressing mononuclear cells was studied following electroporation-mediated plasmid delivery.

METHODS

Plasmids expressing beta-galactosidase (pVR1012-betagal) or enhanced green fluorescent protein (eGFP) (pVR1012-eGFP) were electrotransferred into rat tibialis anterior muscles. Both transfection efficiency and the inflammatory response were determined in pVR1012-betagal-injected muscles by beta-galactosidase and haematoxylin and eosin staining of muscles 7 days post-plasmid injection. Muscles injected with pVR1012-eGFP were stained for CD3, CD68 and desmin at 24 and 48 h post-injection to determine whether mononuclear cells expressing eGFP were of immune or myogenic origin.

RESULTS

With electroporation, beta-galactosidase expression was significantly enhanced by up to ten-fold compared to plasmid injection without electroporation. A large area of regenerating muscle fibres and inflammatory cell infiltration was found in electroporated plasmid-injected muscle. No eGFP expression was found in CD3- or CD68-positive cells. Small mononuclear cells expressing eGFP showed negative staining for CD3 and CD68, but all stained positive for desmin.

CONCLUSIONS

In situ electroporation enhanced transfection efficiency of plasmid DNA delivery into muscle. Alongside its advantage for improving gene transfer, electroporation led to an increased inflammatory response and muscle damage. Mononuclear cells in muscle were transfected with plasmid and expressed the transgene. These cells were of myogenic origin with no evidence of transgene expression in infiltrating inflammatory cells.

Apelin induces enlarged and nonleaky blood vessels for functional recovery from ischemia

The efficacy of therapeutic angiogenesis for revascularization in ischemia using genes, proteins, and cells has been established. For further improvement, processes allowing enlargement of the luminal cavity to facilitate efficient blood flow need to be facilitated. Recently, we found that expression of APJ and its specific ligand, apelin, is seen in endothelial cells when angiogenesis is taking place during embryogenesis. Apelin-deficient mice are viable but have narrow intersomitic vessels during embryogenesis and narrow blood vessels in the trachea and skin after birth. Apelin induces the formation of larger cords of endothelial cells, mainly mediated by cell-cell aggregation, resulting in the generation of larger blood vessels. Here we report that transgenic overexpression of apelin in keratinocytes induces enlarged but not leaky blood vessels in the dermis. In the hind limb ischemia model, apelin together with vascular endothelial growth factor (VEGF) effectively induced functional vessels larger than with VEGF alone. Endogenous apelin is required for the suppression of VEGF-, histamine-, or inflammation-induced vascular hyperpermeability. Apelin inhibited the down-modulation of vascular endothelial-cadherin by VEGF, resulting in suppression of hyperpermeability. Our results suggest apelin efficacy for therapeutic angiogenesis.

Novel polymer carriers and gene constructs for treatment of myocardial ischemia and infarction

The number one cause of mortality in the US is cardiovascular related disease. Future predictions do not see a reduction in this rate especially with the continued rise in obesity [P. Poirier, et al., Obesity and cardiovascular disease: pathophysiology, evaluation, and effect of weight loss, Arterioscler Thromb Vasc Biol. 26(5), (2006) 968-976.; K. Obunai, S. Jani, G.D. Dangas, Cardiovascular morbidity and mortality of the metabolic syndrome, Med.Clin. North Am., 91(6), (2007) 1169-1184]. Even so, potential molecular therapeutic targets for cardiac gene delivery are in no short supply thanks to continuing advances in molecular cardiology. However, efficient and safe delivery remains a bottleneck in clinical gene therapy [O.J. Muller, H.A. Katus, R. Bekeredjian, Targeting the heart with gene therapy-optimized gene delivery methods, Cardiovasc Res, 73(3), (2007) 453-462]. Viral vectors are looked upon favorably for their high transduction efficiency, although their ability to elicit toxic immune responses remains [C.F. McTiernan, et al., Myocarditis following adeno-associated viral gene expression of human soluble TNF receptor (TNFRII-Fc) in baboon hearts, Gene Ther, 14(23), (2007) 1613-1622]. However, this high transduction does not necessarily translate into improved efficacy [X. Hao, et al., Myocardial angiogenesis after plasmid or adenoviral VEGF-A(165) gene transfer in rat myocardial infarction model, Cardiovasc Res., 73(3), (2007) 481-487]. Naked DNA remains the preferred method of DNA delivery to cardiac myocardium and has been explored extensively in clinical trials. The results from these trials have demonstrated efficacy in regard to secondary end-points of reduced symptomatology and perfusion, but have failed to establish significant angiogenesis or an increase in myocardial function [P.B. Shah, D.W. Losordo, Non-viral vectors for gene therapy: clinical trials in cardiovascular disease, Adv Genet, 54, (2005) 339-361]. This may be due in part to reduced transfection efficiency but can also be attributed to use of suboptimal candidate genes. Currently, polymeric non-viral gene delivery to cardiac myocardium remains underrepresented. In the past decade several advances in non-viral vector development has demonstrated increased transfection efficiency [O.J. Muller, H.A. Katus, R. Bekeredjian, Targeting the heart with gene therapy-optimized gene delivery methods, Cardiovasc Res, 73(3), (2007) 453-462]. Of these polymers, those that employ lipid modifications to improve transfection or target cardiovascular tissues have proven themselves to be extremely beneficial. Water-soluble lipopolymer (WSLP) consists of a low molecular weight branched PEI (1800) and cholesterol. The cholesterol moiety adds extra condensation by forming stable micellular complexes and was later employed for myocardial gene therapy to exploit the high expression of lipoprotein lipase found within cardiac tissue. Use of WSLP to deliver hypoxia-responsive driven expression of hVEGF to ischemic rabbit myocardium has proven to provide for even better expression in cardiovascular cells than Terplex and has demonstrated a significant reduction in infarct size (13+/-4%, p<0.001) over constitutive VEGF expression (32+/-7%, p=0.007) and sham-injected controls (48+/-7%). A significant reduction in apoptotic values and an increase in capillary growth were also seen in surrounding tissue. Recently, investigations have begun using bioreducible polymers made of poly(amido polyethylenimines) (SS-PAEI). SS-PAEIs breakdown within the cytoplasm through inherent redox mechanisms and provide for high transfection efficiencies (upwards to 60% in cardiovascular cell types) with little to no demonstrable toxicity. In vivo transfections in normoxic and hypoxic rabbit myocardium have proven to exceed those results of WSLP transfections by 2-5 fold [L.V. Christensen, et al., Reducible poly(amido ethylenediamine) for hypoxia-inducible VEGF delivery, J Control Release, 118(2), (2007) 254-261]. This new breed of polymer(s) may allow for decreased doses and use of new molecular mechanisms not previously available due to low transfection efficiencies. Little development has been seen in the use of new gene agents for treatment of myocardial ischemia and infarction. Current treatment consists of using mitogenic factors, described decades earlier, alone or in combination to spur angiogenesis or modulating intracellular Ca2+ homeostasis through SERCA2a but to date, failed to demonstrate clinical efficacy. Recent data suggests that axonal guidance cues also act on vasculature neo-genesis and provide a new means of investigation for treatment.

Potential Use of Gene Transfer in Athletic Performance Enhancement

After only a short history of three decades from concept to practice, gene therapy has recently been shown to have potential to treat serious human diseases. Despite this success, gene therapy remains in the realm of experimental medicine, and much additional preclinical and clinical study will be necessary for proving the efficacy and safety of this approach in the treatment of diseases in humans. However, a potential complicating factor is that advances in gene transfer technology could be misused to enhance athletic performance in sports, in a practice termed "gene doping". Moreover, gene doping could be a precursor to a broader controversial agenda of human "genetic enhancement" with the potential for a significant long-term impact on society. This review addresses the possible ways in which knowledge and experience gained in gene therapy in animals and humans may be abused for enhancing sporting prowess. We provide an overview of recent progress in gene therapy, with potential application to gene doping and with the major focus on candidate performance-enhancement genes. We also discuss the current status of preclinical studies and of clinical trials that use these genes for therapeutic purposes. Current knowledge about the association between the natural "genetic make-up" of humans and their physical characteristics and performance potential is also presented. We address issues associated with the safety of gene transfer technologies in humans, especially when used outside a strictly controlled clinical setting, and the obstacles to translating gene transfer strategies from animal studies to humans. We also address the need for development and implementation of measures to prevent abuse of gene transfer technologies, and to pursue research on strategies for its detection in order to discourage this malpractice among athletes.

Transplantation of genetically engineered mesenchymal stem cells improves cardiac function in rats with myocardial infarction: benefit of a novel nonviral vector, cationized dextran

It is expected that mesenchymal stem cells (MSCs) will be a cell source for cardiac reconstruction because of their differentiation potential and ability to supply growth factors. However, poor viability at the transplanted site often hinders the therapeutic potential of MSCs. Here, in a trial designed to address this problem, a non-viral carrier of cationized polysaccharide is introduced for genetic engineering of MSCs. Spermine-introduced dextran of cationized polysaccharide (spermine-dextran) was internalized into MSCs by way of a sugar-recognizable receptor to enhance the expression level of plasmid deoxyribonucleic acid (DNA). When genetically engineered by the spermine-dextran complex with plasmid DNA of adrenomedullin (AM), MSCs secreted a large amount of AM, an anti-apoptotic and angiogenic peptide. Transplantation of AM gene-engineered MSCs improved cardiac function after myocardial infarction significantly more than MSCs alone. Thus, this genetic engineering technology using the non-viral spermine-dextran is a promising strategy to improve MSC therapy for ischemic heart disease.

Preparation, characterization, cytotoxicity and transfection efficiency of poly(DL-lactide-co-glycolide) and poly(DL-lactic acid) cationic nanoparticles for controlled delivery of plasmid DNA

The objective of this study was to investigate the effect of formulation parameters (i.e. polymer molecular weight and homogenization speed) on various physicochemical and biological properties of cationic nanoparticles. Cationic nanoparticles were prepared using different molecular weights of poly(DL-lactide-co-glycolide) (PLGA) and poly(DL-lactic acid) (PLA) by double emulsion solvent evaporation at two different homogenization speeds, and were characterized in terms of size, surface charge, morphology, loading efficiency, plasmid release, plasmid integrity, cytotoxicity, and transfection efficiency. Cationic surfactant, cetyltrimethylammonium bromide (CTAB), was used to provide positive charge on the surface of nanoparticles. Reporter plasmid gWIZ Beta-gal was loaded on the surface of nanoparticles by incubation. Use of higher homogenization speed and lower molecular weight polymer led to a decrease in mean particle size, increase in zeta potential, increase in plasmid loading efficiency, and a decrease in burst release. The nanoparticles displayed good morphology as evident from scanning electron micrographs. In vitro cytotoxicity study by MTT assay showed a low toxicity. Structural integrity of the pDNA released from nanoparticles was maintained. Transfecting human embryonic kidney (HEK293) cells with nanoparticles prepared from low molecular weight PLGA and PLA resulted in an increased expression of beta-galactosidase as compared to those prepared from high molecular weight polymer. Our results demonstrate that the PLGA and PLA cationic nanoparticles can be used to achieve prolonged release of pDNA, and the plasmid release rate and transfection efficiency are dependent on the formulation variables.

Novel challenges in exploring peptide ligands and corresponding tissue-specific endothelial receptors

The structural and molecular diversity of vascular endothelium may depend on the functional state and tissue localisation of its cells. Tumour vasculature expresses a number of molecular markers that distinguish it from normal vasculature. In cancer, the determinant of specific tumour vasculature heterogeneity is, in part, dictated by dysregulated expression of tumour-derived angiogenic factors. The identification of molecular 'addresses' on the surface of tumour vasculature has significantly contributed to the selection of targets, which have been used for delivering therapeutic and imaging agents in cancer. Cytotoxic drug, pro-apoptotic peptides, protease inhibitors, and gene therapy vectors have been successfully linked to peptides and delivered to tumour sites with an improved experimental therapy. Different diagnostic and therapeutic compounds can be efficiently targeted to specific receptors on vascular endothelial cells; the development of ligand-directed vector tools may promote systemic targeted gene delivery. Here, we review the very recent advances in the identification of peptide ligands and their corresponding tissue-specific endothelial receptors through the phage display technology with emphasis on ligand-directed delivery of therapeutic agents and targeted gene therapy.

Transitional angiogenesis and vascular remodeling during coronary angiogenesis in response to myocardial infarction

Coronary artery disease (CAD) is a major source of morbidity and mortality in the industrialized world. CAD causes ischemia as a prelude to angina, myocardial infarction and heart failure as specific forms of heart disease causing a decline in the quality of life. CAD or atherosclerosis and the resulting myocardial ischemia trigger a natural angiogenic response that generates collateral circulations. The long-term goal for these studies is to develop therapeutic angiogenesis that augments the natural coronary angiogenesis. This project makes use of an infarcted transgenic mouse model to characterize formation of those collateral circulations in the post-infraction heart. The experiments utilized thoracotomy and a microcauterizer to produce an infarct in transgenic mice and this stimulated neovascularization and allowed labeling of the coronary vessels, thereby defining the morphogenic processes involved in formation of collateral circulations. The results show that the heart consistently responds to infarcts with angiogenesis at 1d post-treatment (PT) that undergoes transition into vascular remodeling at 7d PT with complete remodeling at 14d PT. The vascular remodeling appears to mitigate any net increase in perfusion that may be achieved early in coronary angiogenesis. The results suggest that therapeutic approaches need to shift from an exclusive focus on stimulating angiogenesis to include modulation of vascular remodeling for increased long-term myocardial perfusion.

Emerging vectors and targeting methods for nonviral gene therapy

Until recently, nonviral vectors were outside the mainstream of gene transfer technology. Recent problems in clinical trials using viral vectors renewed interest in these methods. The clinical usefulness of nonviral methods is still hindered by their relatively low gene delivery/transgene expression efficiencies. Vectors must navigate a series of obstacles before the therapeutic gene can be expressed. This review considers these barriers and the properties of components of nonviral vectors that are essential for nucleic acid transfer. Although developments of new physical methods (hydrodynamic delivery, ultrasound, electroporation) have made a significant impact on gene transfer efficiency, various chemical carriers (lipids and polymers) have been shown to achieve high-level gene delivery and functional expression. Success of nonviral gene targeting will depend not only on the efficacy, but also safety of this methodology, and this aspect is also discussed. Understanding problems associated with nonviral targeting can also help in designing better viral vectors. In fact, interplay between viral and nonviral technologies should lead to a continued refinement of both methodologies.

Repeated direct endomyocardial transplantation of allogeneic mesenchymal stem cells: safety of a high dose, "off-the-shelf", cellular cardiomyoplasty strategy

BACKGROUND

Efficacy of cellular cardiomyoplasty seems to occur in a dose-related manner. However, the safety of multiple transendomyocardial transplantation procedures to administer high cell dosages has not been previously reported. The aims of this study were to assess the short- and intermediate-term results of a repeated cell administration strategy and evaluate the safety of an "off-the-shelf" allogeneic mesenchymal stem cell (MSC) source.

METHODS

Porcine bone marrow-derived MSCs were culture-expanded through three cycles in vitro before transplantation. Yorkshire swine weighing 30-40 kg were allocated to receive the total dose during 1 injection procedure or divided over 2 procedures separated by 14 days, as follows: (i) 400x10(6) allogeneic MSC (n=5), (ii) 800x10(6) allogeneic MSC divided in 2 doses (n=5), (iii) cryopreservant vehicle containing 10% DMSO, 5% porcine serum and 85% PlasmaLyte A, 14 days apart (n=2), or (iv) sterile saline 14 days apart (n=2). During each procedure, twenty 0.5 ml aliquots of the assigned injectant were administered using the Stiletto Endocardial Direct Injection Catheter System, targeting at the left ventricular anterior, septal and lateral walls under fluoroscopy. Vital signs and electrocardiograms were recorded during the procedure and at 24 h. The animals were examined daily and cardiac enzymes were measured immediately post-procedure, and on days 1, 15 and 90. Necropsy and histopathology were performed at day 90.

RESULTS

Mean transendocardial injection procedure time was 40+/-10 min. All ventricular target areas were accessed by the Stiletto system. Ventricular ectopic beats and/or non-sustained ventricular tachycardia associated with catheter contact or endomyocardial injections were observed in all cases. However, no sustained ventricular arrhythmia, anaphylaxis, or significant cardiac enzyme release was seen. One mortality resulted from air embolism during the procedure. All other swine survived from the time of recovery until planned sacrifice at day 90 and had normal physical examination findings. The 3-month histopathology showed no evidence of rejection, calcification, teratoma or myocardial infarction.

CONCLUSION

Repeated endomyocardial transplantation of high dose, bone marrow-derived allogeneic cells appeared safe in a large animal, human surrogate model. Such cellular cardiomyoplasty strategy warrants further investigation.

Computational model of vascular endothelial growth factor spatial distribution in muscle and pro-angiogenic cell therapy

Members of the vascular endothelial growth factor (VEGF) family of proteins are critical regulators of angiogenesis. VEGF concentration gradients are important for activation and chemotactic guidance of capillary sprouting, but measurement of these gradients in vivo is not currently possible. We have constructed a biophysically and molecularly detailed computational model to study microenvironmental transport of two isoforms of VEGF in rat extensor digitorum longus skeletal muscle under in vivo conditions. Using parameters based on experimental measurements, the model includes: VEGF secretion from muscle fibers; binding to the extracellular matrix; binding to and activation of endothelial cell surface VEGF receptors; and internalization. For 2-D cross sections of tissue, we analyzed predicted VEGF distributions, gradients, and receptor binding. Significant VEGF gradients (up to 12% change in VEGF concentration over 10 mum) were predicted in resting skeletal muscle with uniform VEGF secretion, due to non-uniform capillary distribution. These relative VEGF gradients were not sensitive to extracellular matrix composition, or to the overall VEGF expression level, but were dependent on VEGF receptor density and affinity, and internalization rate parameters. VEGF upregulation in a subset of fibers increased VEGF gradients, simulating transplantation of pro-angiogenic myoblasts, a possible therapy for ischemic diseases. The number and relative position of overexpressing fibers determined the VEGF gradients and distribution of VEGF receptor activation. With total VEGF expression level in the tissue unchanged, concentrating overexpression into a small number of adjacent fibers can increase the number of capillaries activated. The VEGF concentration gradients predicted for resting muscle (average 3% VEGF/10 mum) is sufficient for cellular sensing; the tip cell of a vessel sprout is approximately 50 mum long. The VEGF gradients also result in heterogeneity in the activation of blood vessel VEGF receptors. This first model of VEGF tissue transport and heterogeneity provides a platform for the design and evaluation of therapeutic approaches.

Synthetic oligosaccharide stimulates and stabilizes angiogenesis: structure-function relationships and potential mechanisms

To determine the proangiogenesis effect of series of saccharides and a synthetic oligosaccharide and potential mechanisms, an in vitro 3-dimensional endothelial cell sprouting (3D-ECS) assay and the chick chorioallantoic membrane (CAM) model were used. We demonstrated that a sulfated oligosaccharide significantly promotes the endothelial capillary network initiated by vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF). Furthermore, although the capillary network initiated by VEGF and b-FGF lasts no more than 7 days, addition of a sulfated oligosaccharide significantly amplifies angiogenesis and stabilizes the capillary network of new blood vessels. In the CAM model, sulfated oligosaccharide also stimulated angiogenesis. In both the CAM and the 3D-ECS assay, structure-function studies reveal that increased saccharide chain length up to the hexa- to decasaccharide show optimal proangiogenesis efficacy. In addition, the sulfation and molecular shape (branched vs linear) of oligosaccharide are important for sustained proangiogenesis efficacy. Data indicate that chemically defined synthetic oligosaccharides can play an important role in regulation of capillary structure and stability, which may contribute to future advances in therapeutic angiogenesis. The proangiogenesis efficacy of an oligosaccharide is mediated via integrin alphavbeta3 and involves mitogen-activated protein kinase signaling mechanisms.

Potential therapeutic gene for the treatment of ischemic disease: Ad2/hypoxia-inducible factor-1alpha (HIF-1)/VP16 enhances B-type natriuretic peptide gene expression via a HIF-1-responsive element

In this issue of Molecular Pharmacology, Luo et al. (p. 1953) present a study employing a HIF-1alpha/VP16 chimera to investigate the mechanism by which this constitutively active transcription factor activates expression of brain natriuretic peptide (BNP). The results define a functional hypoxia responsive element (HRE) in the promoter of the human BNP gene and demonstrate that this HRE is necessary for HIF-1alpha/VP16-induced gene expression in human cardiomyocytes grown under normoxic conditions. Luo et al. also show that a consensus E-box DNA binding sequence is necessary for appropriate BNP regulation. Because HIF-1 is known to elicit protective and beneficial gene expression programs in many scenarios and because BNP is known to be cardioprotective, this study provides support for the therapeutic use of the chimeric HIF-1alpha/VP16 protein in coronary heart disease. However, because HIF-1alpha is a key regulatory molecule that acts upon a large number of downstream gene networks, there remains a need for further investigation. Particularly useful would be comprehensive gene expression profiling coupled with functional analysis of HIF-1alpha/VP16-regulated genes. The results of such studies will elucidate the mechanism of beneficial effects and address concerns regarding potential adverse effects of activating specific HIF-1alpha/VP16-dependent gene programs.