Gene transfer of kringle 5 of plasminogen by electroporation inhibits corneal neovascularization

In Vivo and Ex Vivo Gene Electrotransfer in Ophthalmological Disorders

The aim of this document is to present an overview of gene electrotransfer in ophthalmological disorders. In order to ensure an adequate variety of the assessed studies, several electronic databases were considered and studies published between January 1998 and December 2021 were analysed. Three investigators carried out data extraction and analysis, focusing on both technical (i.e., electrical protocol, type of electrode, plasmid) and medical (i.e., type of study, threated disease) aspects and highlighting the main differences in terms of results obtained. Moreover, the IGEA experience in the project “Transposon-based, targeted ex vivo gene therapy to treat age-related macular degeneration” (TargetAMD) was reported in the results section. No clinical trial was found on international literature and on ClinicalTrials.gov. Twelve preclinical studies were found including in vivo and ex-vivo applications. The studied showed that electrotransfer could be very efficient for plasmid DNA transfection. Many attempts such as modification of the electric field, buffers and electrodes have been made and the optimization of electric field setting seems to be very important. Using this technique, gene replacement can be designed in cases of retinal inheritance or corneal disease and a wide range of human eye diseases could, in the future, benefitfrom these gene therapy technologies.

Gene therapy in the anterior eye segment

This review provides comprehensive information about the advances in gene therapy in the anterior segment of the eye including cornea, conjunctiva, lacrimal gland, and trabecular meshwork. We discuss gene delivery systems including viral and non-viral vectors as well as gene editing techniques, mainly CRISPR-Cas9, and epigenetic treatments including antisense and siRNA therapeutics. We also provide a detailed analysis of various anterior segment diseases where gene therapy has been tested with corresponding outcomes. Disease conditions include corneal and conjunctival fibrosis and scarring, corneal epithelial wound healing, corneal graft survival, corneal neovascularization, genetic corneal dystrophies, herpetic keratitis, glaucoma, dry eye disease, and other ocular surface diseases. Although most of the analyzed results on the use and validity of gene therapy at the ocular surface have been obtained in vitro or using animal models, we also discuss the available human studies. Gene therapy approaches are currently considered very promising as emerging future treatments of various diseases, and this field is rapidly expanding.

New Frontiers of Corneal Gene Therapy

Corneal diseases are among the most prevalent causes of blindness worldwide. The transparency and clarity of the cornea are guaranteed by a delicate physiological, anatomic, and functional balance. For this reason, all the disorders, including those of genetic origin, that compromise this state of harmony can lead to opacity and eventually vision loss. Many corneal disorders have a genetic etiology, and some are associated with rather rare and complex syndromes. Conventional treatments, such as corneal transplantation, are often ineffective, and to date, many of these disorders are still incurable. Gene therapy carries the promise of being a potential cure for many of these diseases, with solutions and strategies that did not seem possible until a few years ago. With its potential to treat genetic disease by means of deletion, replacement, or editing of a defective gene, the challenge can also be extended to corneal disorders in order to achieve long-term, if not definitive, relief. The aim of this paper is to review the state of the art of the different gene therapy approaches as potential treatments for corneal diseases and the future perspectives for the development of personalized gene-based medicine.

Characterization and bioactivity of self-assembled anti-angiogenic chondroitin sulfate-ES2-AF nanoparticle conjugate

BACKGROUND

In the past few years, significant progress has been made in inhibiting neovascularization at the tumor site, cutting off the nutrient supply of the tumor, and inhibiting tumor growth and metastasis. However, many proteins/peptides have the disadvantage of poor stability, short half-life, and uncertain targeting ability. Chemical modification can be used to overcome these disadvantages; many polyethylene glycol-modified proteins/peptides have been approved by US FDA. The purpose of this study was to obtain a novel anti-angiogenic chondroitin sulfate (CS)-peptide nanoparticle conjugate with efficient anti-neovascularization and tumor targeting ability and an acceptable half-life.

MATERIALS AND METHODS

The CS-ES2-AF nanoparticle conjugate was synthesized and characterized using 1H-nuclear magnetic resonance spectroscopy, transmission electron microscopy, and particle size and zeta potential analyzer. The anti-angiogenic ability was studied using MTT, migration, tube formation, and chick chorioallantoic membrane assays. The targeting ability of CS-ES2-AF was studied by ELISA, surface plasmon resonance, and bioimaging. The pharmacokinetics was also studied.

RESULTS

The CS-ES2-AF could self-assemble into stable nanoparticles in aqueous solution, which significantly enhances its anti-neovascularization activity, tumor targeting more explicit, and prolongs its half-life.

CONCLUSION

CS is an effective protein/peptide modifier, and CS-ES2-AF displayed good potential in tumor targeting therapy.

Clinical correlates of common corneal neovascular diseases: a literature review

A large subset of corneal pathologies involves the formation of new blood and lymph vessels (neovascularization), leading to compromised visual acuity. This article aims to review the clinical causes and presentations of corneal neovascularization (CNV) by examining the mechanisms behind common CNV-related corneal pathologies, with a particular focus on herpes simplex stromal keratitis, contact lenses-induced keratitis and CNV secondary to keratoplasty. Moreover, we reviewed CNV in the context of different types of corneal transplantation and keratoprosthesis, and summarized the most relevant treatments available so far.

Anti-angiogenic effects of a mutant endostatin: a new prospect for treating retinal and choroidal neovascularization

Purpose

Pathological fundus angiogenesis is a major cause of vision loss in retina diseases. Endostatin, a C-terminal fragment of collagen XVIII, is an endogenous anti-angiogenic protein. The present study aimed to investigate the in vitro and in vivo anti-angiogenic properties of two proteins: an N-terminal H1D/H3D mutant endostatin (M-ES) and a polyethylene glycol propionaldehyde (PEG) covalent M-ES (PEG-M-ES).

Methods

M-ES and PEG-M-ES properties were characterized in vitro using a zinc ion binding assay and a stability test. Activity assays, including migration, proliferation, and tube formation assays, were performed with human retinal microvascular endothelial cells (HRMECs) and human umbilical vein endothelial cells (HUVECs). Mouse oxygen-induced retinopathy (OIR) and choroidal neovascularization (CNV) models were used to evaluate in vivo anti-angiogenic effects. In addition, a rabbit model was used to study the retinal pharmacokinetic profile following an intravitreal injection.

Results

The results indicated that the H1D/H3D mutations of endostatin reduced the zinc binding capacity of M-ES and facilitated PEG covalent binding. PEG-M-ES was more stable and persisted longer in the retina compared with M-ES. The in vitro studies demonstrated that M-ES and PEG-M-ES inhibited HRMEC and HUVEC proliferation, migration, and tube formation more efficiently than ES. In vivo, a single intravitreal injection of M-ES and PEG-M-ES significantly decreased neovascularization in both the OIR and CNV animal models.

Conclusion

The present study demonstrated for the first time that PEG-M-ES exhibits a long-term inhibitory effect on neovascularization in vitro and in vivo. These data suggest that PEG-M-ES may represent an innovative therapeutic strategy to prevent fundus neovascularization.

Placental growth factor expression is reversed by antivascular endothelial growth factor therapy under hypoxic conditions

BACKGROUND

Clinical trials have revealed that the antivascular endothelial growth factor (VEGF) therapies are effective in retinopathy of prematurity (ROP). But the low level of VEGF was necessary as a survival signal in healthy conditions, and endogenous placental growth factor (PIGF) is redundant for development. The purpose of this study was to elucidate the PIGF expression under hypoxia as well as the influence of anti-VEGF therapy on PIGF.

METHODS

CoCl2-induced hypoxic human umbilical vein endothelial cells (HUVECs) were used for an in vitro study, and oxygen-induced retinopathy (OIR) mice models were used for an in vivo study. The expression patterns of PIGF under hypoxic conditions and the influence of anti-VEGF therapy on PIGF were evaluated by quantitative reverse transcription-polymerase chain reaction (RTPCR). The retinal avascular areas and neovascularization (NV) areas of anti-VEGF, anti-PIGF and combination treatments were calculated. Retina PIGF concentration was evaluated by ELISA after treatment. The vasoactive effects of exogenous PIGF on HUVECs were investigated by proliferation and migration studies.

RESULTS

PIGF mRNA expression was reduced by hypoxia in OIR mice, in HUVECs under hypoxia and anti-VEGF treatment. However, PIGF expression was reversed by anti-VEGF therapy in the OIR model and in HUVECs under hypoxia. Exogenous PIGF significantly inhibited HUVECs proliferation and migration under normal conditions, but it stimulated cell proliferation and migration under hypoxia. Anti-PIGF treatment was effective for neovascular tufts in OIR mice (P<0.05).

CONCLUSION

The finding that PIGF expression is iatrogenically up-regulated by anti-VEGF therapy provides a consideration to combine it with anti-PIGF therapy.

DNA delivery in adult mouse eyes: an update with corneal outcomes

Ocular injection (intravitreal, subretinal, or into the anterior space) is an efficient approach to deliver many classes of drugs, cells, and other treatments to various cell types of the eye. In particular, subretinal injection is efficient since delivered agents accumulate as there is no dilution due to transport processes or diffusion and the volume of the interphotoreceptor space (IPS) is minimal (10-20 μl in the human eye, less than 1 μl in the mouse eye). We previously reported methods using subretinal injection and electroporation to deliver DNA to photoreceptor and retinal pigment epithelium cells in retinas of live mice (Johnson et al., 14:2211-2226; Nickerson et al. 884:53-69, 2012; Andrieu-Soler et al. 13:692-706, 2007). Here we detail further optimization of that approach and additionally report its use in delivering DNA expression plasmids to the corneal endothelium.

Emerging techniques to treat corneal neovascularisation

Neovascularisation is a major cause of visual loss in a number of ophthalmic diseases. This review aims to outline the basic regulators of vessel growth in corneal neovascularisation. An understanding of the underlying principles of physiological and pathophysiological vascular development helps to appreciate current approaches to prevent or treat corneal neovascularisation. Options for future interventions will be discussed in the light of recent evidence provided by animal models of corneal neovascularisation.

Intramuscular electroporation of a plasmid encoding human plasminogen kringle 5 induces growth inhibition of Lewis lung carcinoma in mice

Tumor growth and metastasis depend critically on blood vessel formation. Antiangiogenesis, therefore, represents a promising strategy for cancer therapy. The kringle 5 (K5) domain of human plasminogen is a potent angiogenesis inhibitor. To investigate whether intramuscular electroporation (EP) of K5 has antitumor activity in mouse tumor models, we constructed a plasmid encoding K5 (pVAX1-K5). Hela cells transfected with this plasmid produced and secreted K5 that inhibited the migration of human microvascular endothelial cells. Intramuscular EP treatment of pVAX1-K5 inhibited the growth of Lewis lung carcinoma and prolonged the survival time of tumor-bearing mice. Angiogenesis was obviously inhibited, and apoptosis was induced in tumor cells of mice that received intramuscular EP of pVAX1-K5. On the contrary, intramuscular injection of pVAX1-K5 without EP failed to show the same effects. The data indicate that intramuscular EP of plasmid DNA encoding the K5 domain is an effective strategy for the experimental treatment of cancer by expressing K5.

Effects of the phosphatidylinositol 3-kinase inhibitor in a mouse model of retinal neovascularization

PURPOSE

To determine the effects of LY294002, a phosphatidylinositol 3-kinase inhibitor, on suppressing experimental retinal neovascularization in an animal model of ischemic retinopathy.

METHODS

The effect of LY294002 on the survival of RF/6A cells stimulated by vascular endothelial growth factor (VEGF) was investigated colorimetrically. The inhibitory activity of LY294002 on the migration of cells stimulated with VEGF was measured by cell counting. C57BL/6N mice at postnatal day (P) 7 were exposed to 75 +/- 2% oxygen for 5 days (P7-P11) and then returned to room air for 5 days (P12-P17) to induce retinal neovascularization. Beginning on P12, mice received daily intraperitoneal injections of LY294002 or dimethyl sulfoxide and phosphate-buffered saline (control) through P17. Retinal neovascularization was examined by adenosine diphosphatase staining after 5 days in room air and was quantitated histologically by counting the neovascular endothelial cell nuclei anterior to the inner limiting membrane.

RESULTS

LY294002 significantly inhibited VEGF-induced survival and migration. LY294002-treated and control animals demonstrated no perfusion regions in the posterior retina. Retinas from control mice at P17 contained neovascular tufts at the junction between the perfused and nonperfused retina. The tufts contained numerous neovascular nuclei. Retinas from mice treated with LY294002 demonstrated a significant reduction in neovascular cell nuclei compared with control mice.

CONCLUSIONS

LY294002 significantly inhibits retinal neovascularization in a mouse model of retinal neovascularization.

Corneal gene therapy

Gene therapy to the cornea can potentially correct inherited and acquired diseases of the cornea. Factors that facilitate corneal gene delivery are the accessibility and transparency of the cornea, its stability ex vivo and the immune privilege of the eye. Initial corneal gene delivery studies characterized the relationship between intraocular modes of administration and location of reporter gene expression. The challenge of achieving effective topical gene transfer, presumably due to tear flow, blinking and low penetration of the vector through epithlelial tight junctions left no alternative but invasive administration to the anterior chamber and corneal stroma. DNA vaccination, RNA interference and gene transfer of cytokines, growth factors and enzymes modulated the corneal microenvironment. Positive results were obtained in preclinical studies for prevention and treatment of corneal graft rejection, neovascularization, haze and herpetic stromal keratitis. These studies, corneal gene delivery systems and modes of administration, and considerations regarding the choice of animal species used are the focus of this review. Opportunities in the field of corneal gene therapy lie in expanding the array of corneal diseases investigated and in the implementation of recent designs of safer vectors with reduced immunogenicity and longer duration of gene expression.

Electrically Assisted Ocular Gene Therapy

Electrotransfer and iontophoresis are being developed as innovative non-viral gene delivery systems for the treatment of eye diseases. These two techniques rely on the use of electric current to allow for higher transfection yield of various ocular cell types in vivo. Short pulses of relatively high-intensity electric fields are used for electrotransfer delivery, whereas the iontophoresis technique is based on the application of low voltage electric current. The basic principles of these techniques and their potential therapeutic application for diseases of the anterior and posterior segments of the eye are reviewed. Iontophoresis has been found most efficient for the delivery of small nucleic acid fragments such as antisense oligonucleotides, siRNA, or ribozymes. Electrotransfer, on the other hand, is being developed for the delivery of oligonucleotides or custom designed plasmids. The wide range of strategies already validated and the potential for targeting specific types of cells confirm the promising early observations made using electrotransfer and iontophoresis. These two nonviral delivery systems are safe and can be used efficiently for targeted gene delivery to ocular tissues in vivo. At the present, their application for the treatment of ocular human diseases is nearing its final stages of adaptation and practical implementation at the bedside.

Non-viral ocular gene therapy: potential ocular therapeutic avenues

Non-viral vectors for potential gene replacement and therapy have been developed in order to overcome the drawbacks of viral vectors. The diversity of non-viral vectors allows for a wide range of various products, flexibility of application, ease of use, low-cost of production and enhanced "genomic" safety. Using non-viral strategies, oligonucleotides (ODNs) can be delivered naked (less efficient) or entrapped in cationic lipids, polymers or peptides forming slow release delivery systems, which can be adapted according to the organ targeted and the therapy purposes. Tissue and cell internalization can be further enhanced by changing by physical or chemical means. Moreover, a specific vector can be selected according to disease course and intensity of manifestations fulfilling specific requirements such as the duration of drug release and its level along with cells and tissues specific targeting. From accumulating knowledge and experience, it appears that combination of several non-viral techniques may increase the efficacy and ensure the safety of these evolving and interesting gene therapy strategies.

[Comparison of several viral vectors for gene therapy of corneal endothelial cells]

AIM

In this paper we compare the transduction efficiency, toxicity, and safety of retroviral vectors [equine infectious anemia virus (EIAV), human immunodeficiency virus-1 (HIV-1), human foamy virus (PFV] and adenovirus (Ad) for potential use in gene therapy of corneal endothelial cells.

METHOD

Murine corneal endothelial cells were transduced with EIAV, HIV-1, PFV, and Ad, resulting in the overexpression of a green fluorescent protein (eGFP) transgene marker. The transduction efficiency was assessed by flow cytometry, while cytotoxicity and apoptosis rate were detected by annexin V/propidium iodide (PI) stain.

RESULTS

Ad had the highest transduction efficiency with 99% of the cells expressing the transgene, followed by EIAV (95%), HIV-1 (75%), and PFV (43%). However, the high transduction efficiency of Ad also resulted in the highest apoptosis rate (25%) in the corneal endothelial cells. There was no detectable difference in the toxicity between PFV and HIV-1 (10%). EIAV transduction had the lowest cytotoxicity, with only 3% of the cells being annexin V/PI positive.

CONCLUSION

Compared to other vectors EIAV exhibited high transduction efficiency combined with low toxicity to corneal endothelial cells. Therefore, it is a powerful tool for gene therapy applications in selected corneal endothelial diseases.

Gene therapy approaches to prolonging corneal allograft survival

Irreversible immunological rejection is the major cause of human corneal allograft failure and occurs despite the use of topical glucocorticoid immunosuppression. Systemic pharmacological interventions have not found widespread favour in corneal transplantation because of associated morbidities and inadequate demonstration of efficacy. Gene therapy offers tantalising prospects for improving corneal allograft survival, especially in those recipients at high risk of graft rejection. Donor corneas can be gene-modified ex vivo, while in storage prior to implantation, and the relative isolation of the transplanted cornea from the circulation decreases the risk of potential systemic complications. A wide variety of vectors have been found suitable for gene transfer to the cornea. The mechanisms involved in corneal graft rejection have been placed on a relatively secure footing over the past decade and in consequence a number of transgenes with promise for modulating rejection have been identified. However, relatively few studies have thus far demonstrated significant prolongation of corneal allograft survival after gene transfer to the donor cornea. In these instances, the therapeutic protein almost certainly acted at a proximal level in the afferent immune response, within the ocular environs.

Gene therapy for proliferative ocular diseases

Proliferative ocular diseases encompass a wide variety of pathological processes with adverse cellular differentiation, proliferation and migration as common features. Pathologies may involve neovascular responses associated with diabetic retinopathy, retinopathy of prematurity or age-related macular degeneration. These diseases are quite prevalent and account for substantial visual impairment and blindness worldwide. Although treatment strategies are largely surgical, advances in our understanding of the proteins crucial to cell transdifferentiation, proliferation and migration, along with better gene transfer techniques, have greatly increased the potential for biological treatment options. In this report, the most common proliferative ocular vascular diseases and existing therapeutic modalities will be reviewed and an overview of possible gene therapy options will be discussed, along with potential candidate genes.

Lipid-mediated delivery of brain-specific angiogenesis inhibitor 1 gene reduces corneal neovascularization in an in vivo rabbit model

Corneal neovascularization, which occurs in many pathologic states of the cornea, reduces the visual acuity. Recently, we found that the extracellular region of brain-specific angiogenesis inhibitor 1 (BAI1-ECR) has antiproliferative activity through functional blocking of alpha(v)beta(5) integrin in endothelial cells. In this study, we investigated the effects of lipid-mediated subconjunctival injection of the BAI1-ECR gene on corneal angiogenesis induced by epithelial debridement by heptanol in the rabbit. When a pEGFP-BAI1-ECR plasmid was given subconjunctivally 1 week after epithelial debridement, green fluorescence was detected in the corneal stroma with expression persisting for 7 days. To test the effect of BAI1-ECR on neovascularization, rabbits were injected with the BAI1-ECR gene or empty vector two or three times at 1-week intervals beginning 1 week after debridement. When measured with biomicroscopy at 1 or 2 weeks after two weekly injections, BAI1-delivered eyes had significantly less neovascularized corneal area than vector-injected ones in both time periods. Similar microscopic results were obtained after three weekly injections of BAI1-ECR. In quantitative histological examination, the BAI1-receiving eyes showed significantly less neovascular area and number of vessels than vector-injected ones. Also, after two weekly injections, BAI1-delivered eyes had decreased neovascularized corneal area equivalent to that of anti-VEGF antibody-injected ones. These results indicate that BAI1-ECR gene delivery effectively reduces experimental corneal neovascularization and suggest that the BAI1-ECR protein can be used as an angiogenesis suppressor in the eye.