Comparison of Viral and Nonviral Vectors for Gene Transfer to Human Endothelial Progenitor Cells

Secretion of proteins and antibody fragments from transiently transfected endothelial progenitor cells

In neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and amyotrophic lateral sclerosis, neuroinflammation can lead to blood‐brain barrier (BBB) breakdown. After intravenous or intra‐arterial injection into mice, endothelial progenitor cells (EPCs) home to the damaged BBB to promote neurovascular repair. Autologous EPCs transfected to express specific therapeutic proteins offer an innovative therapeutic option. Here, we demonstrate that EPC transfection by electroporation with plasmids encoding the reporter protein GFP or an anti‐β‐amyloid antibody fragment (Fab) leads to secretion of each protein. We also demonstrate the secreted anti‐β‐amyloid Fab protein functions in β‐amyloid aggregate solubilization.

Tuning of endosomal escape and gene expression by functional groups, molecular weight and transfection medium: a structure-activity relationship study

The use of genetic material by non-viral transfer systems is still in its initial stages, but there are high expectations for the development of targeted therapies. However, nucleic acids cannot enter cells without help, they must be well protected to prevent degradation and overcome a variety of biological barriers, the endosomal barrier being one of the greatest cellular challenges. Herein, the structure-property-relationship was investigated in detail, using well-defined polymers. Polyacrylamides were synthesized via RAFT polymerization resulting in a polymer library of (i) different cationic groups as aminoethyl acrylamide (AEAm), dimethylaminoethyl acrylamide (DMAEAm), dimethylaminopropyl acrylamide (DMAPAm) and guanidinopropyl acrylamide (GPAm); (ii) different degree of polymerization; and investigated (iii) in different cell culture settings. The influence of molar mass and cationic moiety on complex formation with pDNA, cytotoxicity and transfection efficiency of the polymers were investigated. The systematic approach identified a pH-independent guanidinium-containing homopolymer (PGPAm₈₉) as the polymer with the highest transfection efficiency and superior endosomal release under optimal conditions. Since PGPAm₈₉ is not further protonated inside endosomes, common escape theories appear unsuitable. Therefore, the interaction with bis(monoacryloylglycerol)phosphate, a lipid specific for endosomal vesicles, was investigated. Our research suggests that the interactions between amines and lipids may be more relevant than anticipated.

Gene therapy for peripheral arterial disease

BACKGROUND

Peripheral arterial disease (PAD), caused by narrowing of the arteries in the limbs, is increasing in incidence and prevalence as our population is ageing and as diabetes is becoming more prevalent. PAD can cause pain in the limbs while walking, known as intermittent claudication, or can be more severe and cause pain while at rest, ulceration, and ultimately gangrene and limb loss. This more severe stage of PAD is known as 'critical limb ischaemia'. Treatments for PAD include medications that help to reduce the increased risk of cardiovascular events and help improve blood flow, as well as endovascular or surgical repair or bypass of the blocked arteries. However, many people are unresponsive to medications and are not suited to surgical or endovascular treatment, leaving amputation as the last option. Gene therapy is a novel approach in which genetic material encoding for proteins that may help increase revascularisation is injected into the affected limbs of patients. This type of treatment has been shown to be safe, but its efficacy, especially regarding ulcer healing, effects on quality of life, and other symptomatic outcomes remain unknown.

OBJECTIVES

To assess the effects of gene therapy for symptomatic peripheral arterial disease.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched Cochrane CENTRAL, the Cochrane Vascular Specialised Register, MEDLINE Ovid, Embase Ovid, CINAHL, and AMED, along with trials registries (all searched 27 November 2017). We also checked reference lists of included studies and systematic reviews for further studies.

SELECTION CRITERIA

We included randomised and quasi-randomised studies that evaluated gene therapy versus no gene therapy in people with PAD. We excluded studies that evaluated direct growth hormone treatment or cell-based treatments.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, performed quality assessment, and extracted data from the included studies. We collected pertinent information on each study, as well as data for the outcomes of amputation-free survival, ulcer healing, quality of life, amputation, all-cause mortality, ankle brachial index, symptom scores, and claudication distance.

MAIN RESULTS

We included in this review a total of 17 studies with 1988 participants (evidence current until November 2017). Three studies limited their inclusion to people with intermittent claudication, 12 limited inclusion to people with varying levels of critical limb ischaemia, and two included people with either condition. Study investigators evaluated many different types of gene therapies, using different protocols. Most studies evaluated growth factor-encoding gene therapy, with six studies using vascular endothelial growth factor (VEGF)-encoding genes, four using hepatocyte growth factor (HGF)-encoding genes, and three using fibroblast growth factor (FGF)-encoded genes. Two studies evaluated hypoxia-inducible factor 1-alpha (HIF-1α) gene therapy, one study used a developmental endothelial locus-1 gene therapy, and the final study evaluated a stromal cell-derived factor-1 (SDF-1) gene therapy. Most studies reported outcomes after 12 months of follow-up, but follow-up ranged from three months to two years.Overall risk of bias varied between studies, with many studies not providing sufficient detail for adequate determination of low risk of bias for many domains. Two studies did not utilise a placebo control, leading to risk of performance bias. Several studies reported in previous protocols or in their Methods sections that they would report on certain outcomes for which no data were then reported, increasing risk of reporting bias. All included studies reported sponsorships from corporate entities that led to unclear risk of other bias. The overall quality of evidence ranged from moderate to very low, generally as the result of heterogeneity and imprecision, with few or no studies reporting on outcomes.Evidence suggests no clear differences for the outcomes of amputation-free survival, major amputation, and all-cause mortality between those treated with gene therapy and those not receiving this treatment (all moderate-quality evidence). Low-quality evidence suggests improvement in complete ulcer healing with gene therapy (odds ratio (OR) 2.16, 95% confidence interval (CI) 1.02 to 4.59; P = 0.04). We could not combine data on quality of life and can draw no conclusions at this time regarding this outcome (very low-quality evidence). We included one study in the meta-analysis for ankle brachial index, which showed no clear differences between treatments, but we can draw no overall association (low-quality evidence). We combined in a meta-analysis pain symptom scores as assessed by visual analogue scales from two studies and found no clear differences between treatment groups (very low-quality evidence). We carried out extensive subgroup analyses by PAD classification, dosage schedule, vector type, and gene used but identified no substantial differences.

AUTHORS' CONCLUSIONS

Moderate-quality evidence shows no clear differences in amputation-free survival, major amputation, and all-cause mortality between those treated with gene therapy and those not receiving gene therapy. Some evidence suggests that gene therapy may lead to improved complete ulcer healing, but this outcome needs to be explored with improved reporting of the measure, such as decreased ulcer area in cm², and better description of ulcer types and healing. Further standardised data that are amenable to meta-analysis are needed to evaluate other outcomes such as quality of life, ankle brachial index, symptom scores, and claudication distance.

Construction and characterization of human embryonic kidney-(HEK)-293T cell overexpressing truncated α4 integrin

Blockade of α4 integrin by antibodies could be an appropriate treatment strategy in multiple sclerosis and Crohn's disease. Considering disadvantages of antibodies, other elements (e.g. aptamers) have been proposed for antibodies replacement. Isolation of aptamers through cell-SELEX (systematic evolution of ligands by exponential enrichment) method requires positive and negative expressing α4 integrin cell lines. For a better isolation, we intended to construct a negative cell line lacking of specific ligand binding site of α4 integrin. Escherichia coli strain top 10 was used for truncated integrin subunit α4 (TITGA-4) expression vector. Human embryonic kidney (HEK)-293T cell was transfected with linearized TITGA-4 plasmid and subsequently screened for stable truncated TITGA-4 expressing cells. Chromosomal DNA of truncated TITGA-4-transfected cells was extracted and the presence of truncated TITGA-4 gene in HEK-293T genome was confirmed by polymerase chain reaction (PCR). The expression level of truncated TITGA-4 on HEK-293T cells was also analysed by real-time PCR and flow cytometry. Real-time PCR and flow cytometric analysis showed significant difference of truncated TITGA-4 expression between untransfected HEK-293T cells compared to transfected cells. The results suggest that we have successfully constructed the truncated integrin α4 expressing HEK-293T cell, which will facilitate further research into the production of antibody, nanobody, and aptamer against α4 integrin.

Nonviral Gene Therapy for Cancer: A Review

Although the development of effective viral vectors put gene therapy on the road to commercialization, nonviral vectors show promise for practical use because of their relative safety and lower cost. A significant barrier to the use of nonviral vectors, however, is that they have not yet proven effective. This apparent lack of interest can be attributed to the problem of the low gene transfer efficiency associated with nonviral vectors. The efficiency of gene transfer via nonviral vectors has been reported to be 1/10th to 1/1000th that of viral vectors. Despite the fact that new gene transfer methods and nonviral vectors have been developed, no significant improvements in gene transfer efficiency have been achieved. Nevertheless, some notable progress has been made. In this review, we discuss studies that report good results using nonviral vectors in vivo in animal models, with a particular focus on studies aimed at in vivo gene therapy to treat cancer, as this disease has attracted the interest of researchers developing nonviral vectors. We describe the conditions in which nonviral vectors work more efficiently for gene therapy and discuss how the goals might differ for nonviral versus viral vector development and use.

Beyond Gene Transfection with Methacrylate-Based Polyplexes-The Influence of the Amino Substitution Pattern

Methacrylate-based polymers represent promising nonviral gene delivery vectors, since they offer a large variety of polymer architectures and functionalities, which are beneficial for specific demands in gene delivery. In combination with controlled radical polymerization techniques, such as the reversible addition-fragmentation chain transfer polymerization, the synthesis of well-defined polymers is possible. In this study we prepared a library of defined linear polymers based on (2-aminoethyl)-methacrylate (AEMA), N-methyl-(2-aminoethyl)-methacrylate (MAEMA), and N,N-dimethyl-(2-aminoethyl)-methacrylate (DMAEMA) monomers, bearing pendant primary, secondary, and tertiary amino groups, and investigated the influence of the substitution pattern on their gene delivery capability. The polymers and the corresponding plasmid DNA complexes were investigated regarding their physicochemical characteristics, cytocompatibility, and transfection performance. The nonviral transfection by methacrylate-based polyplexes differs significantly from poly(ethylene imine)-based polyplexes, as a successful transfection is not affected by the buffer capacity. We observed that polyplexes containing a high content of primary amino groups (AEMA) offered the highest transfection efficiency, whereas polyplexes bearing tertiary amino groups (DMAEMA) exhibited the lowest transfection efficiency. Further insights into the uptake and release mechanisms could be identified by fluorescence and transmission electron microscopy, emphasizing the theory of membrane-pore formation for the time-efficient endosomal release of methacrylate-based vectors.

Targeting REDV peptide functionalized polycationic gene carrier for enhancing the transfection and migration capability of human endothelial cells

Targeting gene engineering should be considered as an effective method for promoting endothelialization of vascular grafts. Herein, we developed a targeting REDV peptide functionalized polycationic gene carrier for carrying the pEGFP-ZNF580 plasmid with the aim of enhancing the transfection and migration capability of human endothelial cells. This polycationic gene carrier with the REDV peptide (mPEG-P(LA-co-CL)-PEI-REDV) was prepared by the conjugation of the Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide with the amphiphilic block copolymer methoxy poly(ethylene glycol) ether-poly(l-lactide-co-ε-caprolactone)-poly(ethyleneimine) (mPEG-P(LA-co-CL)-PEI). mPEG-P(LA-co-CL)-PEI nanoparticles (NP) and mPEG-P(LA-co-CL)-PEI-REDV nanoparticles (REDV-NP) were formed by the self-assembly of the corresponding polycationic polymers, and then their pEGFP-ZNF580 complexes were prepared via the electrostatic interaction with pEGFP-ZNF580 plasmids, respectively. Gel electrophoresis results show that the targeted REDV-NPs could compress pEGFP-ZNF580 plasmids into stable complexes and protect the plasmids against desoxyribonuclease degradation. MTT assay indicates that these targeted REDV-NP/pEGFP-ZNF580 complexes exhibit better cyto-compatibility than the non-targeted NP/pEGFP-ZNF580 complexes and the control PEI 1800 Da/pEGFP-ZNF580 complexes. In vitro transfection experiments and western blot analysis of EA.hy926 endothelial cells show that the pEGFP-ZNF580 plasmid expression and the relative protein level transfected by targeted REDV-NP/pEGFP-ZNF580 complexes are roughly consistent with that transfected by PEI 25 kDa/pEGFP-ZNF580 complexes. More importantly, the scratch wound assay results demonstrate that the migration capability of EA.hy926 cells has been improved significantly by the expression of the pEGFP-ZNF580 plasmid. Our results indicate that the polycationic polymer with functional REDV peptides can be a potential candidate as a pEGFP-ZNF580 plasmid delivery carrier and may be used in the endothelialization of vascular grafts.

Induction of antigen-specific immune responses by dendritic cells transduced with a recombinant lentiviral vector encoding MAGE-A3 gene

PURPOSE

Melanoma antigen gene A3 (MAGE-A3) is aberrantly expressed in a number of cancer types. Because of its high specificity, MAGE-A3 has shown to be a promising candidate for cancer immunotherapy. Dendritic cells (DCs) have emerged as the natural agents for antigen delivery. DCs transduced with antigen may increase immune response and maintain immune durability. The aim of this study was to investigate the roles of DCs transduced with lentiviral vectors (LVs) encoding full-length MAGE-A3 gene in cancer immunotherapy .

METHODS

A LV containing full-length MAGE-A3 gene (rLV/MAGE-A3) was constructed. Reverse transcriptase-polymerase chain reaction and direct DNA sequencing were performed to verify the construct. Human DCs derived from umbilical cord blood were then transduced with rLV/MAGE-A3. The potency of rLV/MAGE-A3-transduced DCs was examined by measurement of surface markers and mixed lymphocyte reaction. The MAGE-A3-specific T-cell response induced by DCs was detected using the lactate dehydrogenase release assay.

RESULTS

rLV/MAGE-A3 was constructed successfully and used to transduce DCs efficiently. DCs transduced with rLV/MAGE-A3 stably expressed MAGE-A3 and yielded high percentage of cells expressing CD80, CD86, and HLA-DR. rLV/MAGE-A3 transduction did not impair DCs viability and maturation at a multiplicity of infection of 30. The rLV/MAGE-A3-transduced DCs induced MAGE-A3-specific T lymphocytes that exhibited a significant lysis activity against MAGE-A3-bearing tumor cell lines (HuH-7 and SGC-7901).

CONCLUSIONS

DC-directed rLV/MAGE-A3 efficiently induced antigen-specific immune responses, indicating the possibility of DC-based MAGE-A3 antigen vaccine as a promising strategy for treatment of MAGE-A3-associated cancer.

The therapeutic effect of PEI-Mn0.5Zn0.5Fe2O4 nanoparticles/pEgr1-HSV-TK/GCV associated with radiation and magnet-induced heating on hepatoma

Comprehensive therapy based on the integration of hyperthermia, radiation, gene therapy and chemotherapy is a promising area of study in cancer treatment. Using PEI-Mn(0.5)Zn(0.5)Fe(2)O(4) nanoparticles (PEI-MZF-NPs) as a gene transfer vector, the authors transfected self-prepared pEgr1-HSV-TK into HepG2 cells and measured the expression of the exogenous gene HSV-TK by RT-PCR. The results showed that HSV-TK was successfully transfected into HepG2 cells and the expression levels of HSV-TK remained stable. Besides, PEI-MZF-NPs were used as magnetic media for thermotherapy to treat hepatoma by magnet-induced heating, combined with radiation-gene therapy. Both in vitro and in vivo results suggest that this combined treatment with gene, radiation and heating has a better therapeutic effect than any of them alone. The apoptotic rate and necrotic rate of the combined treatment group was 51.84% and 15.45%, respectively. In contrast, it was only 20.55% and 6.80% in the radiation-gene group, 7.49% and 3.62% in the radiation-alone group, 15.23% and 7.90% in the heating-alone group, and only 3.52% and 2.16% in the blank control group. The inhibition rate of cell proliferation (88.5%) of the combined treatment group was significantly higher than that of the radiation-gene group (59.5%), radiation-alone group (37.6%) and heating-alone group (60.6%). The tumor volume and mass inhibition rate of the combined treatment group was 94.45% and 93.38%, respectively, significantly higher than 41.28% and 33.58% of the radiation-alone group, 60.76% and 52.18% of the radiation-gene group, 79.91% and 77.40% of the heating-alone group. It is therefore concluded that this combined application of heating, radiation and gene therapy has a good synergistic and complementary effect and PEI-MZF-NPs can act as a novel non-viral gene vector and magnetic induction medium, which offers a viable approach for the treatment of cancer.

Adenovirus-mediated transcriptional targeting of colorectal cancer and effects on treatment-resistant hypoxic cells

BACKGROUND

Colorectal cancer is the second leading cause of cancer-related mortality and frequently presents with locally advanced or metastatic disease. Adenovirus (Ad) vectors are important gene delivery agents because they offer efficient and broad tissue transduceability. However, their ability to penetrate through multicell layers in colorectal cancers and maintain expression in colon tumor-related hypoxic conditions has yet to be analyzed. Furthermore, their broad tissue tropism presents safety concerns.

MATERIALS AND METHODS

An ex vivo cultured patient tumor sample model was employed to examine Ad transduction of colorectal tumors.

RESULTS

Results obtained from Ad delivery of the firefly luciferase (FLuc) reporter gene indicated that colon tumor tissue was more amenable to Ad transduction than other tumor histologic types examined (breast and ovary). Ad transduction levels were significantly higher than a range of viral and nonviral methods examined in patient colon tissue. Control of transgene expression using the CXC chemokine receptor 4 (CXCR4) promoter was examined as a strategy to confine expression to tumor cells. An Ad construct carrying FLuc under the control of the human CXCR4 promoter demonstrated low reporter gene expression compared with the ubiquitously expressing cytomegalovirus promoter in normal colon and liver tissue while providing high expression in tumors, demonstrating a 'tumour-on' and 'normal-off' phenotype in patient tissue. The effects of changing hypoxia on Ad-related transgene expression were examined in an in vitro model of hypoxic conditions relevant to clinical colorectal tumors. Reporter gene expression varied depending on the level of hypoxia, with significantly reduced levels observed with prolonged hypoxia. However, transgene expression was robust in the cycling hypoxic conditions relevant to colorectal tumors.

CONCLUSION

This study provides novel, clinically relevant data demonstrating the potential for efficient gene delivery to colorectal tumors using Ad.

In vitro functional testing of endothelial progenitor cells that overexpress thrombomodulin

This study investigated the augmentation of endothelial progenitor cell (EPC) thromboresistance by using gene therapy to overexpress thrombomodulin (TM), an endothelial cell membrane glycoprotein that has potent anti-coagulant properties. Late outgrowth EPCs were isolated from peripheral blood of patients with documented coronary artery disease and transfected with an adenoviral vector containing human TM. EPC transfection conditions for maximizing TM expression, transfection efficiency, and cell viability were employed. TM-overexpressing EPCs had a fivefold increase in the rate of activated protein C production over native EPCs and EPCs transfected with an adenoviral control vector expressing β-galactosidase (p<0.05). TM upregulation caused a significant threefold reduction in platelet adhesion compared to native EPCs, and a 12-fold reduction compared to collagen I-coated wells. Additionally, the clotting time of TM-transfected EPCs incubated with whole blood was significantly extended by 19% over native cells (p<0.05). These data indicate that TM-overexpression has the potential to improve the antithrombotic performance of patient-derived EPCs for endothelialization applications.

Highly efficient lentiviral transduction of phenotypically and genotypically characterized endothelial progenitor cells from adult peripheral blood

Postnatal vasculogenesis has been implicated as an important mechanism for neovascularization via bone marrow-derived endothelial progenitor cells (EPCs) circulating in peripheral blood. In preparation of the utilization of EPCs in clinical protocols, we have generated blood-derived EPCs according to two established protocols by culturing either nonadherent mononuclear cells on fibronectin or adherent mononuclear cells on collagen. To explore the feasibility of these EPCs for their potential clinical use as target cells for genetic transduction to enhance their thromboresistance, newly designed retroviral and lentiviral gene ontology expression vectors were tested. Whereas cell clusters derived from the nonadherent cells demonstrated an only limited proliferative potential, cell colonies derived from collagen-adherent cells expanded more than a million-fold. Characterization of the exponentially growing cells by surface antigen and gene expression profiling revealed a consistently strong expression of characteristic endothelial markers, whereas expression of leukocyte markers was gradually lost. Using a single-step transduction protocol, we were able to achieve gene transfer efficiency of up to 99%. Our results suggest that the generated blood-derived EPC population might be attractive target cells for tissue engineering and gene therapy protocols due to their well defined phenotype, extensive proliferative potential, and efficient genetic transducibility, three important qualities that need to be defined prior to any clinical use.

Endothelial lineage cell as a vehicle for systemic delivery of cancer gene therapy

A major limitation of cancer gene therapy is the difficulty of delivering a therapeutic gene to distant sites of metastatic disease. A promising strategy to address this difficulty is to use expanded ex vivo cells to produce a therapeutic protein. As with other approaches to gene therapy, this strategy is attractive when the therapeutic protein is unstable ex vivo or has a short circulating half life in vivo. The initial step to develop a cancer gene therapy using autologous cell delivery is the identification of a cell type that migrates to the tumor site, is readily available for harvesting, and is manipulated easily ex vivo. Recent evidence suggests that endothelial progenitor, precursor, and blood outgrowth endothelial cells are attracted to the tumor vasculature by its angiogenic drive. Here, we review recent advances in the study of circulating endothelial cell-mediated tumor vasculogenesis and discuss the advantages and challenges of bringing endothelial lineage-based cancer gene therapy closer to clinical application.

MR reporter gene imaging of endostatin expression and therapy

PURPOSE

The aim of this study is to monitor endostatin gene expression and therapy using transferrin receptor (TfR) as reporter gene and transferrin conjugate of ultrasmall supramagnetic iron oxide nanoparticle (Tf-USPIO) as magnetic resonance (MR) reporter probe.

PROCEDURE

A retroviral plasmid (pLP-LNCX) encoding mouse endostatin and TfR was constructed, and packaged with a titer of 4 × 10(7)colony-forming units per millimeter. MDA-MB-231 breast tumors were established in BALB/c mice by subcutaneous injection of 2 × 10(6) MDA-MB-231 cells. Mice were intratumorally injected with recombinant retrovirus and imaged with MR using Tf-USPIO. Western blot, Prussian blue, and immunohistochemical staining were performed to validate the magnetic resonance imaging results. The antitumor effect of retro-endostatin (ES)-TfR was also evaluated by intratumoral injection of the viral vector.

RESULTS

The expression of both endostatin and TfR genes in MDA-MB-231 cells after retroviral transfection was confirmed by Western blot and flow cytometry. Tf-USPIO conjugate binds specifically to cells stably transfected with retro-ES-TfR. After intravenous injection of the Tf-USPIO conjugate, there was a more pronounced decrease in T2 relaxation time in tumors treated with retro-ES-TfR than in tumors treated with empty retrovirus retro-LNCX. The expression of ES gene significantly delayed the growth of MDA-MB-231 tumor and reduction of microvessel density and VEGF level as compared to those without viral transfection or transfected with empty retro-LNCX vector.

CONCLUSIONS

Endostatin therapeutic gene expression was visualized successfully using TfR reporter gene and Tf-USPIO MR reporter probe, which indicates that MR reporter gene imaging may be valuable in gene therapy to evaluate therapeutic gene expression and treatment efficacy.