In vivo use of oligonucleotides to inhibit choroidal neovascularisation in the eye

RNA-targeting strategies as a platform for ocular gene therapy

Genetic medicine is offering hope as new therapies are emerging for many previously untreatable diseases. The eye is at the forefront of these advances, as exemplified by the approval of Luxturna® by the United States Food and Drug Administration (US FDA) in 2017 for the treatment of one form of Leber Congenital Amaurosis (LCA), an inherited blindness. Luxturna® was also the first in vivo human gene therapy to gain US FDA approval. Numerous gene therapy clinical trials are ongoing for other eye diseases, and novel delivery systems, discovery of new drug targets and emerging technologies are currently driving the field forward. Targeting RNA, in particular, is an attractive therapeutic strategy for genetic disease that may have safety advantages over alternative approaches by avoiding permanent changes in the genome. In this regard, antisense oligonucleotides (ASO) and RNA interference (RNAi) are the currently popular strategies for developing RNA-targeted therapeutics. Enthusiasm has been further fuelled by the emergence of clustered regularly interspersed short palindromic repeats (CRISPR)-CRISPR associated (Cas) systems that allow targeted manipulation of nucleic acids. RNA-targeting CRISPR-Cas systems now provide a novel way to develop RNA-targeted therapeutics and may provide superior efficiency and specificity to existing technologies. In addition, RNA base editing technologies using CRISPR-Cas and other modalities also enable precise alteration of single nucleotides. In this review, we showcase advances made by RNA-targeting systems for ocular disease, discuss applications of ASO and RNAi technologies, highlight emerging CRISPR-Cas systems and consider the implications of RNA-targeting therapeutics in the development of future drugs to treat eye disease.

Application of Nanomaterials in the Treatment and Diagnosis of Ophthalmology Diseases

Eye diseases often lead to impaired vision and seriously affect the daily life of patients. Local administration of ophthalmic drugs is one of the most important approaches for the treatment of ophthalmic diseases. However, due to the special biochemical environment of the ocular tissue and the existence of many barriers, the bioavailability of conventional ophthalmic preparations in the eye is very low. Nanomaterials can be utilized as carriers of drugs, which can improve the absorption, distribution, metabolism and bioavailability of drugs in eyes. Nanomaterials have also the advantages of small size, simple preparation, good degradability, strong targeting, and little stimulation to biological tissues, providing an innovative and practical method for the drug delivery of ophthalmic diseases. In addition, nanomaterials can be used as an auxiliary means for early diagnosis of ophthalmic diseases by improving the specificity and accuracy of detection methods. Nanomaterials help clinicians and researchers delve deeper into the physiology and pathology of the eye at the nanoscale. We summarize the application of nanomaterials in the diagnosis and treatment of ophthalmic diseases in this review.

miR-539-5p inhibits experimental choroidal neovascularization by targeting CXCR7

Stromal cell-derived factor-1 (SDF-1) has been previously confirmed to participate in the formation of choroidal neovascularization (CNV) via its receptor, CXC chemokine receptor (CXCR) 4; CXCR7 is a recently identified receptor for SDF-1. The molecular mechanisms and therapeutic value of CXCR7 in CNV remain undefined. In this study, experimental CNV was induced by laser photocoagulation in Brown-Norway pigmented rats, and aberrant CXCR7 overexpression was detected in the retinal pigment epithelial/choroid/sclera tissues of laser-injured eyes. Blockade of CXCR7 activation via CXCR7 knockdown or neutralizing Ab administration inhibited SDF-1-induced cell survival and the tubular formation of human retinal microvascular endothelial cells (HRMECs) in vitro and reduced CNV leakage and lesion size in vivo. By using microRNA array screening and bioinformatic analyses, we identified miR-539-5p as a regulator of CXCR7. Transfection of HRMECs and choroid-retinal endothelial (RF/6A) cells with the miR-539-5p mimic inhibited their survival and tube formation, whereas CXCR7 overexpression rescued the suppressive effect of miR-539-5p. The antiangiogenic activities of the miR-539-5p mimic were additionally demonstrated in vivo by intravitreal injection. ERK1/2 and AKT signaling downstream of CXCR7 is involved in the miR-539-5p regulation of endothelial cell behaviors. These findings suggest that the manipulation of miR-539-5p/CXCR7 levels may have important therapeutic implications in CNV-associated diseases.-Feng, Y., Wang, J., Yuan, Y., Zhang, X., Shen, M., Yuan, F. miR-539-5p inhibits experimental choroidal neovascularization by targeting CXCR7.

Nano-vectors for the Ocular Delivery of Nucleic Acid-based Therapeutics

Nucleic acid-based therapeutics have gained a lot of interest for the treatment of diverse ophthalmic pathologies. The first to enter in clinic has been an oligonucleotide, Vitravene^® for the treatment of cytomegalovirus infection. More recently, research on aptamers for the treatment of age related macular degeneration has led to the development of Macugen^®. Despite intense potential, effective ocular delivery of nucleic acids is a major challenge since therapeutic targets for nucleic acid-based drugs are mainly located in the posterior eye segment, requiring repeated invasive administration. Of late, nanotechnology-based nano-vectors have been developed in order to overcome the drawbacks of viral and other non-viral vectors. The diversity of nano-vectors allows for ease of use, flexibility in application, low-cost of production, higher transfection efficiency and enhanced genomic safety. Using nano-vector strategies, nucleic acids can be delivered either encapsulated or complexed with cationic lipids, polymers or peptides forming sustained release systems, which can be tailored according to the ocular tissue being targeted. The present review focuses on developments and advances in various nano-vectors for the ocular delivery of nucleic acid-based therapeutics, the barriers that such delivery systems face and methods to overcome them.

Topical and intravitreous administration of cationic nanoemulsions to deliver antisense oligonucleotides directed towards VEGF KDR receptors to the eye

Antisense oligonucleotides (ODNs) specific for VEGFR-2-(17 MER) and inhibiting HUVEC proliferation in-vitro were screened. One efficient sequence was selected and incorporated in different types of nanoemulsions the potential toxicity of which was evaluated on HUVEC and ARPE19 cells. Our results showed that below 10 microl/ml, a 2.5% mid-chain triglycerides cationic DOTAP nanoemulsion was non-toxic on HUVEC and retinal cells. This formulation was therefore chosen for further experiments. In-vitro transfection of FITC ODNs in ARPE cells using DOTAP nanoemulsions showed that nanodroplets do penetrate into the cells. Furthermore, ODNs are released from the nanoemulsion after 48 h and accumulate into the cell nuclei. In both ex-vivo and in-vivo ODN stability experiments in rabbit vitreous, it was noted that the nanoemulsion protected at least partially the ODN from degradation over 72 h. The kinetic results of fluorescent ODN (Hex) distribution in DOTAP nanoemulsion following intravitreal injection in the rat showed that the nanoemulsion penetrates all retinal cells. Pharmacokinetic and ocular tissue distribution of radioactive ODN following intravitreal injection in rabbits showed that the DOTAP nanoemulsion apparently enhanced the intraretinal penetration of the ODNs up to the inner nuclear layer (INL) and might yield potential therapeutic levels of ODN in the retina over 72 h post injection.

Recent perspectives in ocular drug delivery

Anatomy and physiology of the eye makes it a highly protected organ. Designing an effective therapy for ocular diseases, especially for the posterior segment, has been considered as a formidable task. Limitations of topical and intravitreal route of administration have challenged scientists to find alternative mode of administration like periocular routes. Transporter targeted drug delivery has generated a great deal of interest in the field because of its potential to overcome many barriers associated with current therapy. Application of nanotechnology has been very promising in the treatment of a gamut of diseases. In this review, we have briefly discussed several ocular drug delivery systems such as microemulsions, nanosuspensions, nanoparticles, liposomes, niosomes, dendrimers, implants, and hydrogels. Potential for ocular gene therapy has also been described in this article. In near future, a great deal of attention will be paid to develop non-invasive sustained drug release for both anterior and posterior segment eye disorders. A better understanding of nature of ocular diseases, barriers and factors affecting in vivo performance, would greatly drive the development of new delivery systems. Current momentum in the invention of new drug delivery systems hold a promise towards much improved therapies for the treatment of vision threatening disorders.

Environmental enrichment effects on development of retinal ganglion cell dendritic stratification require retinal BDNF

A well-known developmental event of retinal maturation is the progressive segregation of retinal ganglion cell (RGC) dendrites into a and b sublaminae of the inner plexiform layer (IPL), a morphological rearrangement crucial for the emergence of the ON and OFF pathways. The factors regulating this process are not known, although electrical activity has been demonstrated to play a role. Here we report that Environmental Enrichment (EE) accelerates the developmental segregation of RGC dendrites and prevents the effects exerted on it by dark rearing (DR). Development of RGC stratification was analyzed in a line of transgenic mice expressing plasma-membrane marker green fluorescent protein (GFP) under the control of Thy-1 promoter; we visualized the a and b sublaminae of the IPL by using an antibody selectively directed against a specific marker of cholinergic neurons. EE precociously increases Brain Derived Neurotrophic Factor (BDNF) in the retina, in parallel with the precocious segregation of RGC dendrites; in addition, EE counteracts retinal BDNF reduction in DR retinas and promotes a normal segregation of RGC dendrites. Blocking retinal BDNF by means of antisense oligos blocks EE effects on the maturation of RGC dendritic stratification. Thus, EE affects the development of RGC dendritic segregation and retinal BDNF is required for this effect to take place, suggesting that BDNF could play an important role in the emergence of the ON and OFF pathways.

Novel cationic lipophilic peptides for oligodeoxynucleotide delivery

In search of new oligodeoxynucleotide (ODN) delivery agents, we evaluated novel peptides derived from core peptide H-GLRILLLKV-OH (CP). CP is a fragment designed from the T-cell antigen receptor (TCR) alpha-chain transmembrane sequence. CP was able to enter cells including T-cells and inhibited interleukin-2 (IL-2) production. To examine the effect of increased lipophilicity on cellular uptake and activity of CP, a lipoamino acid (2-aminododecanoic acid) was incorporated into peptide CP resulting in 2-aminodecanoyl-CP (LP). The toxicity of CP and LP was assessed by measuring the haemolytic activity. Neither compound caused any haemolysis of red blood cells. We have also compared the biological activities of the CP and LP. Using a T-cell antigen presentation assay, the more lipophilic LP caused greater inhibition of IL-2 production than the parent CP in the antigen stimulated T-cells. The LP also showed increased permeability than CP in the Caco-2 cell assay. We utilised the enhanced cell permeability property of LP in oligodeoxynucleotide ODN1 delivery. Isothermal titration calorimetry (ITC) suggested that CP and LP complex with ODN1 in a 12:1 (CP:ODN1) and 15:1 (LP:ODN1) ratio. These complexes were then transfected into human retinal pigment epithelial cells. The level of transfection was measured by the decreased production of the protein human vascular endothelial growth factor (hVEGF). The results revealed greater transfection efficiency for both CP and LP (47%, 55% more inhibition) compared to commercially available transfection agent cytofectin GSV. These results suggested that the CP and particularly its lipophilic analogue LP have the potential to be used as oligodeoxynucleotide delivery systems.

Retinal functional development is sensitive to environmental enrichment: a role for BDNF

Retina has long been considered less plastic than cortex or hippocampus, the very sites of experience-dependent plasticity. Now, we show that retinal development is responsive to the experience provided by an enriched environment (EE): the maturation of retinal acuity, which is a sensitive index of retinal circuitry development, is strongly accelerated in EE rats. This effect is present also in rats exposed to EE up to P10, that is before eye opening, suggesting that factors sufficient to trigger retinal acuity development are affected by EE during the first days of life. Brain derived neurotrophic factor (BDNF) is precociously expressed in the ganglion cell layer of EE with respect to non-EE rats and reduction of BDNF expression in EE animals counteracts EE effects on retinal acuity. Thus, EE controls the development of retinal circuitry, and this action depends on retinal BDNF expression.

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.

Ocular delivery of nucleic acids: antisense oligonucleotides, aptamers and siRNA

Nucleic acids have gained a lot of interest for the treatment of ocular diseases. The first to enter in clinic has been Vitravene an antisense oligonucleotide for the treatment of cytomegalovirus (CMV) infection and more recently, research on aptamers have led to the marketing of anti-vascular endothelial growth factor (VEGF) inhibitor (Macugen) for the treatment of age-related macular degeneration (AMD). The siRNAs appear very promising as they are very potent inhibitors of protein expression. Despite their potential, nucleic acids therapeutic targets of nucleic acid-based drugs are mainly located in the posterior segment of the eye requiring invasive administration which can be harmful if repeated. Their intracellular penetration in some cases needs to be enhanced. This is the reason why adequate delivery systems were designed either to insure cellular penetration, protection against degradation or to allow long-term delivery. A combination of both effects was also developed for an implantable system. In conclusion, the intraocular administration of nucleic acids offers interesting perspectives for the treatment of ocular diseases.

MMP-2 and MMP-9 secretion by rpe is stimulated by angiogenic molecules found in choroidal neovascular membranes

PURPOSE

Matrix metalloproteinases (MMP)-2 and -9 play an important role in the pathogenesis of choroidal neovascularization (CNV). Retinal pigment epithelial cells (RPE) are an important source of MMPs in the outer retinal environment, however little is known about the local factors that modulate MMP secretion in these cells. The purpose of this study was to determine the effects of CNV involved growth factors and the extracellular matrix molecule fibronectin on MMP-2 and -9 secretion by cultured human RPE.

METHODS

MMP-2 and -9 secretion was studied using gelatin zymography, Western blot, and ELISA assay of RPE culture supernatants. The effects of stimulating the cells for 36 hours with vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bGFG), tumor necrosis factor-alpha (TNF-alpha), or fibronectin (FN), all angiogenic factors found in CNV membranes, was determined.

RESULTS

Resting RPE cells secreted MMP-2 but not MMP-9. Stimulation with TNF-alpha induced secretion of MMP-9 and increased the secretion of MMP-2. MMP-2 secretion was also increased by stimulation with FN and VEGF, but not bFGF.

CONCLUSION

The results indicated that the angiogenic molecules VEGF, FN, and TNF-alpha stimulate MMP-2 and -9 secretion from RPE and thus further promote CNV.

Nanoparticle formulation enhances the delivery and activity of a vascular endothelial growth factor antisense oligonucleotide in human retinal pigment epithelial cells

The objective of this study was to investigate the delivery and activity of a vascular endothelial growth factor (VEGF) antisense oligonucleotide in a human retinal pigment epithelial cell line (ARPE-19) using a biodegradable nanoparticulate delivery system. A 19-mer antisense phosphorothioate oligonucleotide (PS-ODN) complementary to bases 6-24 relative to the translational start site of the VEGF mRNA, a sense PS-ODN and a mismatch PS-ODN were examined for the inhibition of secretion and mRNA expression of VEGF using an enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction, respectively. Nanoparticles of the antisense oligonucleotides were formulated using a poly(lactide-co-glycolide) (50:50) copolymer using a double emulsion solvent evaporation method. After preparing nanoparticles, drug loading, encapsulation efficiency and particle size were determined. The cells were exposed to either plain solution of oligonucleotide or nanoparticles of oligonucleotide from Day 3 through Day 6. Alternatively, the cells were incubated with PS-ODNs and lipofectin for 4 h on Day 4. In all studies, VEGF secretion and mRNA expression were determined on Day 6. The particle size, drug loading and encapsulation efficiency were 252 nm, 5.5% and 16.5%, respectively. The antisense PS-ODN inhibited VEGF mRNA and protein secretion when delivered using nanoparticles or lipofectin but not in its free form. This was consistent with the ability of nanoparticles and lipofectin to elevate the cellular uptake of the oligonucleotide by 4-fold and 13-fold, respectively. Neither mismatch nor sense oligonucleotides inhibited VEGF secretion. In conclusion, biodegradable nanoparticles enhance cellular delivery of a VEGF antisense oligonucleotide and inhibit VEGF secretion and mRNA expression in a human retinal pigment epithelial cell line.

Dendrimer delivery of an anti-VEGF oligonucleotide into the eye: a long-term study into inhibition of laser-induced CNV, distribution, uptake and toxicity

We have performed a long-term study into the use of a lipophilic amino-acid dendrimer to deliver an anti-vascular endothelial growth factor (VEGF) oligonucleotide (ODN-1) into the eyes of rats and inhibit laser-induced choroidal neovascularization (CNV). In addition, the uptake, distribution and retinal tolerance of the dendrimer plus oligonucleotide conjugates were examined. Analysis of fluorescein angiograms of laser photocoagulated eyes revealed that dendrimer plus ODN-1 significantly inhibited (P<0.05) the development of CNV for 4-6 months by up to 95% in the initial stages. Eyes similarly injected with ODN-1 alone showed no significant difference (P>0.05) in mean severity score at 2 months (2.86+/-0.09), 4 months (2.15+/-0.17) or 6 months (2.7+/-0.12) compared to the vehicle-injected controls. Furthermore, we showed that intravitreally injected ODN-1 tagged with 6-fam was absorbed by a wide area of the retina and penetrated all of the retinal cell layers to the retinal pigment epithelium. Ophthalmological examinations indicated that the dendrimers plus ODN-1 conjugates were well tolerated in vivo, which was later confirmed using immunohistochemistry, which showed no observable increase in antigens associated with inflammation. We conclude that the use of such dendrimers may provide a viable mechanism for the delivery of therapeutic oligonucleotides for the treatment of angiogenic eye diseases.

New Pharmacologic Approaches to Therapy for Age-Related Macular Degeneration

As a result of a better understanding of molecular mechanisms, a variety of new pharmacologic treatments have recently been developed for patients with age-related macular degeneration (AMD). Efficacy and tolerability have been demonstrated for drugs targeting vascular endothelial growth factor (VEGF), a key player in the pathogenesis of choroidal neovascularization. Both pegaptanib (anti-VEGF aptamer) and ranibizumab (anti-VEGF antibody fragment), applied at 4- to 6-week intervals into the vitreous, modified the natural course of the disease in phase III clinical studies. Corticosteroids with anti-angiogenic properties also represent a treatment option for wet AMD. Both intravitreal triamcinolone and anecortave acetate, administered juxtasclerally, are currently being pursued. The combination of different treatment strategies and potential synergistic effects offers new perspectives. While photodynamic therapy (PDT) combined with intravitreal triamcinolone is already frequently applied, other combinations (e.g. anti-VEGF drugs with PDT or antifibrotic agents) appear to be attractive alternatives. Pigment epithelium-derived factor represents another potential target, as well as inhibitors of matrix-metallo-proteinases. With the advent of gene therapy, the use of small interfering RNA (siRNA) is also on the horizon. Prophylactic measures are still limited. The combination of vitamins C and E, beta-carotene, and zinc as used in the AREDS (Age-Related Eye Disease Study) reduces risk for conversion from early- to late-stage disease in patients with high-risk features, at least to some extent. Lutein and zeaxanthin dietary supplements for improvement of macular pigment density need to be investigated in future longitudinal trials.

[Viral and nonviral gene therapy for treatment of retinal diseases]

The development of gene therapeutic approaches offers new perspectives for the treatment of retinal diseases. The use of both, nonviral methods employing oligonucleotides as well as viral expression vectors provide the possibility to treat neovascularization defects and retinal degeneration, respectively. The mechanism by which the therapeutic oligonucleotides (antisense oligonucleotides, aptamers and siRNA) work is based on degradation of specific transcripts. Consequently, a reduction of the corresponding protein, which is involved in the particular pathogenesis, follows. In contrast, viral vector transduction can substitute the disease-associated gene with an intact copy. So far, animal models have successfully contributed to the development of gene therapeutic medication and further treatments are at the recruiting phase of clinical trials.

Expression of VEGF and angiopoietins in subfoveal membranes from patients with age-related macular degeneration

PURPOSE

Vascular endothelial growth factor (VEGF) and angiopoietins are key regulators of angiogenesis. The purpose of this study was to measure mRNA levels of these factors and of their receptors in surgically excised subfoveal membranes from patients with age-related macular degeneration (AMD) and to evaluate their relevance as prognostic markers of postsurgical recurrence of choroidal neovascularization (CNV).

DESIGN

Prospective observational case series.

METHODS

setting: Institutional. study population: In a prospective series of 24 patients (aged 51 to 91 years) with classic CNV of AMD diagnosed less than 6 months previously, 24 subfoveal membranes (one eye per patient) were surgically removed and collected. Thirteen patients underwent treatment for recurrence of CNV within 6 months of surgery. main outcome measures: Four 8-mu sections were prepared from each membrane for immunohistochemical determination of vascular density (CD31 immunostaining). The remaining tissue was used for preparation of total RNA. The levels of VEGF-A, VEGF-R1, VEGF-R2, neuropilin-1, angiopoietin-1, angiopoietin-2, Tie-2, and hypoxanthine phosphoribosyltransferase mRNAs were determined by real-time reverse-transcriptase polymerase chain reaction.

RESULTS

Vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2 appeared to be expressed to variable levels in most samples, whereas Tie-2, VEGF-R1, and VEGF-R2 were undetectable. Low levels of VEGF expression correlated with postsurgical recurrence of CNV (P = .07). Angiopoietin-1 and angiopoietin-2 levels did not predict recurrence (P > .1).

CONCLUSION

The results indicate that at the time of surgical excision, subfoveal membranes express angiopoietin-1, VEGF, and, to a lesser degree, angiopoietin-2. Because CNV appears to recur less often in membranes expressing high levels of VEGF, we hypothesize that VEGF acts as a stabilizer of neovessels at this stage of the disease.

Treatments for choroidal and retinal neovascularization: a focus on oligonucleotide therapy and delivery for the regulation of gene function

Blinding eye diseases caused by neovascularization of the retinal tissue are the leading cause of blindness in Western societies. Current treatments, such as laser photocoagulation, are limited in their effectiveness at halting the progression of angiogenesis and are unable to reduce the number of vessels once they have developed. In addition, although complete blindness is often avoided, vision is often permanently impaired by the treatment itself. Several less invasive treatments are being developed and one of these is oligonucleotide gene therapy in which short stretches of nucleotides are being used as inhibitors of key, metabolic processes involved in angiogenesis. Combined with this is the development of new and improved nucleotide chemistries aimed at overcoming many of the problems associated with oligonucleotide gene therapy, such as poor longevity because of endonuclease activity. In addition, advancements in delivery systems have further enhanced the efficacy of oligonucleotide gene therapy by increasing cellular penetration and localizing delivery to specific cell types and organs.

Inhibition of in vitro VEGF expression and choroidal neovascularization by synthetic dendrimer peptide mediated delivery of a sense oligonucleotide

Ocular neovascularisation is the leading cause of blindness in developed countries and the most potent angiogenic factor associated with neovascularisation is vascular endothelial growth factor (VEGF). We have previously described a sense oligonucleotide (ODN-1) that possesses anti-human and rat VEGF activity. This paper describes the synthesis of lipid-lysine dendrimers and their subsequent ability to delivery ODN-1 to its target and mediate a reduction in VEGF concentration both in vitro and in vivo. Positively charged dendrimers were used to deliver ODN-1 into the nucleus of cultured D407 cells. The effects on VEGF mRNA transcription and protein expression were analysed using RT-PCR and ELISA, respectively. The most effective dendrimers in vitro were further investigated in vivo using an animal model of choroidal neovascularisation (CNV). All dendrimer/ODN-1 complexes mediated in a significant reduction in VEGF expression during an initial 24 hr period (40-60%). Several complexes maintained this level of VEGF reduction during a subsequent, second 24 hr period, which indicated protection of ODN-1 from the effects of endogenous nucleases. In addition, the transfection efficiency of dendrimers that possessed 8 positive charges (x=81.51%) was significantly better (P=0.0036) than those that possessed 4 positive charges (x=56.8%). RT-PCR revealed a correlation between levels of VEGF protein mRNA. These results indicated that the most effective structural combination was three branched chains of intermediate length with 8 positive charges such as that found for dendrimer 4. Dendrimer 4 and 7/ODN-1 complexes were subsequently chosen for in vivo analysis. Fluorescein angiography demonstrated that both dendrimers significantly (P<0.0001) reduced the severity of laser mediated CNV for up to two months post-injection. This study demonstrated that lipophilic, charged dendrimer mediated delivery of ODN-1 resulted in the down-regulation of in vitro VEGF expression. In addition, in vivo delivery of ODN-1 by two of the dendrimers resulted in significant inhibition of CNV in an inducible rat model. Time course studies showed that the dendrimer/ODN-1 complexes remained active for up to two months indicating the dendrimer compounds provided protection against the effects of nucleases.

Discovery of a novel control element within the 5'-untranslated region of the vascular endothelial growth factor. Regulation of expression using sense oligonucleotides

The regulation of vascular endothelial growth factor (VEGF), a potent stimulator of angiogenesis, is controlled primarily through the interactions of control elements located within the 5'- and 3'-untranslated regions, many of which are yet to be described. In this study we examined the 5'-untranslated region of human VEGF for control elements with the aim of regulating expression both in vitro and in vivo using oligonucleotide gene therapy. A potential control element was located, two sense oligonucleotides (S(1) and S(2)) were designed based on its sequence, and a third oligonucleotide (S(3)) was designed as a control and mapped to the 16 base pairs immediately upstream. Retinal cells cultured in the presence of S(1) and S(2) resulted in a 2-fold increase of VEGF protein and a 1.5-fold increase in mRNA 24 h post-transfection whereas S(3) had no significant effect (p > 0.05) compared with controls. Subsequent reporter gene studies confirmed the necessity of this element for up-regulation by S(1). Further in vivo studies showed that S(1) and S(2) mediated an increase in VEGF protein in a rodent ocular model that resulted in angiogenesis. In addition to providing insight into the regulation of the vascular endothelial growth factor, the use of these oligonucleotides to stimulate vascular growth may prove useful for the treatment of ischemic tissues such as those found in the heart following infarct.

Age-related macular degeneration: etiology, pathogenesis, and therapeutic strategies

Age-related macular degeneration is the principal cause of registered legal blindness among those aged over 65 in the United States, western Europe, Australia, and Japan. Despite intensive research, the precise etiology of molecular events that underlie age-related macular degeneration is poorly understood. However, investigations on parallel fronts are addressing this prevalent public health problem. Sophisticated biochemical and biophysical techniques have refined our understanding of the pathobiology of drusen, geographic atrophy, and retinal pigment epithelial detachments. Epidemiological identification of risk factors has facilitated an intelligent search for underlying mechanisms and fueled clinical investigation of behavior modification. Gene searches have not only brought us to the cusp of identifying the culpable gene loci in age-related macular degeneration, but also localized genes responsible for other macular dystrophies. Recent and ongoing investigations, often cued by tumor biology, have revealed an important role for various growth factors, particularly in the neovascular form of the condition. Transgenic and knockout studies have provided important mechanistic insights into the development of choroidal neovascularization, the principal cause of vision loss in age-related macular degeneration. This in turn has culminated in preclinical and clinical trials of directed molecular interventions.

Delivery of antisense oligonucleotide to the cornea by iontophoresis

We wished to evaluate the potential of iontophoresis to promote the delivery of antisense oligonucleotides (ODN) directed at the vascular endothelial growth factor (VEGF)-R2 receptor (KDR/Flk) to the cornea of the rat eye. Fluorescence (CY5)-labeled ODNs in phosphate-buffered saline (PBS) (20 microM) were locally administered to rat eyes, and their fate within the anterior segment was studied. Thirty-four male, 5-week-old Wistar rats were used for all experiments. The rats were divided in four groups. In group I (12 rats, 12 eyes), the ODNs (20 microM) were delivered by iontophoresis (300 microA for 5 minutes) using a specially designed corneal applicator. In group II (12 rats, 12 eyes), the ODNs (20 microM) were delivered using the same applicator, but no electrical current was applied. In group III (6 rats, 6 eyes), a corneal neovascular reaction was induced prior to the application of ODNs (20 microM), and iontophoresis electrical current was delivered as for group I rats. Group IV (4 rats, 4 eyes) received ODN (60 microM) iontophoresis application (300 microA for 5 minutes) and were used for ODN integrity studies. The animals were killed 5 minutes, 90 minutes, and 24 hours after a single ODN application and studied. Topically applied ODNs using the same iontophoresis applicator but without current do not penetrate the cornea and remain confined to the superficial epithelial layer. ODNs delivered with transcorneoscleral iontophoresis penetrate into all corneal layers and are also detected in the iris. In corneas with neovascularization, ODNs were particularly localized within the vascular endothelial cells of the stroma. ODNs extracted from eye tissues 24 hours after iontophoresis remained unaltered. The iontophoresis current did not cause any detectable ocular damage under these conditions. Iontophoresis promotes the delivery of ODNs to the anterior segment of the eye, including all corneal layers. Iontophoresis of ODNs directed at VEGF-R2 may be used for the design of specific antiangiogenic strategy in diseases of the cornea.

Syntheses of polycationic dendrimers on lipophilic peptide core for complexation and transport of oligonucleotides

Synthesis of novel polycationic lipophilic peptide core(s) was accomplished and these agents successfully transfected human retinal pigment epithelium cells with ODN1 upon complexation with the oligonucleotide. The level of transfection was indirectly measured by the decreased production of the protein hVEGF (human vascular endothelial growth factor) in comparison to the transfection agent cytofectin GSV.

Preclinical evaluation of a phosphorothioate oligonucleotide in the retina of rhesus monkey

Overexpression of vascular endothelial growth factor (VEGF) has been strongly implicated in the development of choroidal neovascularization (CNV) in patients with age-related macular degeneration. In this study, a phosphorothioate oligonucleotide (PS-oligo) targeting both human and rat VEGF(165) genes upstream of the translation initiation code, named DS135 in this study, was evaluated for its uptake dynamics and retinal tolerance after intravitreal (IV) and subretinal (SR) injections in the rhesus monkey. Intravitreal and SR injections of a fluorescent-labeled DS135 (FL-DS135) resulted in both dose- and time-dependent uptake and persistence, and FL-DS135 remained detectable in the retina for at least 3 weeks after injection. Ophthalmic examination showed transient vitreous haze after IV delivery of a high dose but not with a low dose of FL-DS135. Histologic examination showed no evidence of retinal degeneration with respect to IV delivery. After SR delivery, however, dose-related cellular infiltration, transient residual fluid, and slight distortion of the neuroretina were observed. The biologic efficacy of DS135 was further assessed in a laser-induced CNV model, and development of CNV was determined by fluorescein angiography and histologic examination. Incomplete inhibition of CNV formation was observed after IV and SR injection of DS135, but no statistically significant difference was achieved when compared with dose-matched control of PS-oligo. Analysis of fluorescein angiogram and histologic examination showed less than 30% incidence of CNV development in this monkey model. Our study demonstrated that PS-oligos can be successfully introduced into the retina, although with potential limitations, after SR delivery. DS135, a PS-oligo targeting the VEGF gene upstream of the translation initiation code, partially inhibited CNV formation. An improved CNV model is necessary for further confirmation of the full therapeutic potency of DS135 before clinical application.