Inhibitory efficacy of hypoxia-inducible factor 1α short hairpin RNA plasmid DNA-loaded poly (D, L-lactide-co-glycolide) nanoparticles on choroidal neovascularization in a laser-induced rat model

A drug delivery system of HIF-1α siRNA nanoparticles loaded by mesenchymal stem cells on choroidal neovascularization

Aim: To assess mesenchymal stem cells (MSCs) as carriers for HIF-1α siRNA-loaded nanoparticles (NPs) for targeted therapy of experimental choroidal neovascularization (CNV).Materials & methods: A poly (lactic-co-glycolic acid) (PLGA)-core/lipid-shell hybrid NP was designed. The transfection efficacy of MSCs with the hybrid NPs was assessed. Mice were intravenously injected with MSCs after laser photocoagulation and CNV was assessed at 7 days post-injection.Results & conclusion: The transfection efficiency of hybrid NPs into MSCs was 72.7%. HIF-1α mRNA expression in 661w cells co-cultured with MSC-hybrid-siRNA NPs was significantly lower. Intravenous delivery of MSC-hybrid-siRNA NPs greatly reduced CNV area and length. Intravenous injection of MSC-hybrid-siRNA NPs achieved therapeutic efficacy in reducing CNV area. The MSC-mediated homing enabled targeted inhibition of ocular angiogenesis.

Recent Advances in Nanomedicine for Ocular Fundus Neovascularization Disease Management

As an indispensable part of the human sensory system, visual acuity may be impaired and even develop into irreversible blindness due to various ocular pathologies. Among ocular diseases, fundus neovascularization diseases (FNDs) are prominent etiologies of visual impairment worldwide. Intravitreal injection of anti-vascular endothelial growth factor drugs remains the primary therapy but is hurdled by common complications and incomplete potency. To renovate the current therapeutic modalities, nanomedicine emerged as the times required, which is endowed with advanced capabilities, able to fulfill the effective ocular fundus drug delivery and achieve precise drug release control, thus further improving the therapeutic effect. This review provides a comprehensive summary of advances in nanomedicine for FND management from state-of-the-art studies. First, the current therapeutic modalities for FNDs are thoroughly introduced, focusing on the key challenges of ocular fundus drug delivery. Second, nanocarriers are comprehensively reviewed for ocular posterior drug delivery based on the nanostructures: polymer-based nanocarriers, lipid-based nanocarriers, and inorganic nanoparticles. Thirdly, the characteristics of the fundus microenvironment, their pathological changes during FNDs, and corresponding strategies for constructing smart nanocarriers are elaborated. Furthermore, the challenges and prospects of nanomedicine for FND management are thoroughly discussed.

A review on PLGA particles as a sustained drug-delivery system and its effect on the retina

In this review, the designs and recent developments of polymer-based drug delivery of Poly(lactic-co-glycolic acid) (PLGA) will be discussed for the possible treatment of age-related macular degeneration (AMD). PLGA is a versatile co-polymer that consists of synthetic lactic acid and glycolic acid monomers that are constructed to produce nanoparticles, microparticles, and scaffolds for the intraocular delivery of various drugs. As an FDA-approved polymer, PLGA has historically been well-suited for systemic slow-sustained release therapies due to its performance in biodegradability and biocompatibility. This review will examine recent in vitro and in vivo studies that provide evidence for PLGA-based particles as a therapeutic drug carrier for the treatment of AMD. Anti-angiogenic and antiproliferative effects of small peptides, small molecules, RNA molecules, and proteins within PLGA particles are briefly discussed. AMD is a leading cause of central vision loss in people over 55 years and the number of those afflicted will rise as the aging population increases. AMD has two forms that are often sequential. Dry AMD and wet AMD account for 85-90% and 10-15% of cases, respectively. The distinct categories of PLGA-based drug delivery vehicles are important for dispensing novel small molecules, RNA molecules, peptides, and proteins as a long-term effective treatment of AMD.

Polymer- and lipid-based nanocarriers for ocular drug delivery: Current status and future perspectives

Ocular diseases seriously affect patients' vision and life quality, with a global morbidity of over 43 million blindness. However, efficient drug delivery to treat ocular diseases, particularly intraocular disorders, remains a huge challenge due to multiple ocular barriers that significantly affect the ultimate therapeutic efficacy of drugs. Recent advances in nanocarrier technology offer a promising opportunity to overcome these barriers by providing enhanced penetration, increased retention, improved solubility, reduced toxicity, prolonged release, and targeted delivery of the loaded drug to the eyes. This review primarily provides an overview of the progress and contemporary applications of nanocarriers, mainly polymer- and lipid-based nanocarriers, in treating various eye diseases, highlighting their value in achieving efficient ocular drug delivery. Additionally, the review covers the ocular barriers and administration routes, as well as the prospective future developments and challenges in the field of nanocarriers for treating ocular diseases.

Ocular Delivery of Therapeutic Proteins: A Review

Therapeutic proteins, including monoclonal antibodies, single chain variable fragment (ScFv), crystallizable fragment (Fc), and fragment antigen binding (Fab), have accounted for one-third of all drugs on the world market. In particular, these medicines have been widely used in ocular therapies in the treatment of various diseases, such as age-related macular degeneration, corneal neovascularization, diabetic retinopathy, and retinal vein occlusion. However, the formulation of these biomacromolecules is challenging due to their high molecular weight, complex structure, instability, short half-life, enzymatic degradation, and immunogenicity, which leads to the failure of therapies. Various efforts have been made to overcome the ocular barriers, providing effective delivery of therapeutic proteins, such as altering the protein structure or including it in new delivery systems. These strategies are not only cost-effective and beneficial to patients but have also been shown to allow for fewer drug side effects. In this review, we discuss several factors that affect the design of formulations and the delivery of therapeutic proteins to ocular tissues, such as the use of injectable micro/nanocarriers, hydrogels, implants, iontophoresis, cell-based therapy, and combination techniques. In addition, other approaches are briefly discussed, related to the structural modification of these proteins, improving their bioavailability in the posterior segments of the eye without affecting their stability. Future research should be conducted toward the development of more effective, stable, noninvasive, and cost-effective formulations for the ocular delivery of therapeutic proteins. In addition, more insights into preclinical to clinical translation are needed.

Milk exosomes in nutrition and drug delivery

Exosomes are natural nanoparticles that originate in the endocytic system. Exosomes play an important role in cell-to-cell communication by transferring RNAs, lipids, and proteins from donor cells to recipient cells or by binding to receptors on the recipient cell surface. The concentration of exosomes and the diversity of cargos are high in milk. Exosomes and their cargos resist degradation in the gastrointestinal tract and during processing of milk in dairy plants. They are absorbed and accumulate in tissues following oral administrations, cross the blood-brain barrier, and dietary depletion and supplementation elicit phenotypes. These features have sparked the interest of the nutrition and pharmacology communities for exploring milk exosomes as novel bioactive food compounds and for delivering drugs to diseased tissues. This review discusses the current knowledgebase, uncertainties, and controversies in these lines of scholarly endeavor and health research.

MicroRNA-539-5p-Loaded PLGA Nanoparticles Grafted with iRGD as a Targeting Treatment for Choroidal Neovascularization

Choroidal neovascularization (CNV) is a major cause of visual impairment that results from excessive growth of blood vessels in the eye’s choroid. The limited clinical efficacy of the current therapy for this condition requires the emergence of new treatment modalities such as microRNA (miRNAs). A recent study identified microRNA-539-5p (miR-539) as an angiogenic suppressor in a CNV animal model; however, its therapeutic delivery is limited. Therefore, this study aims to formulate miR-539 in targeted nanoparticles (NPs) prepared from polylactic-co-glycolic acid (PLGA). The NPs were decorated with internalizing arginylglycylaspartic (RGD) peptide (iRGD), which specifically targets the alpha-v-beta-3 (αvβ3) integrin receptor that is overexpressed in blood vessels of ocular tissue in CNV patients. The ¹H NMR spectra results revealed successful conjugation of iRGD peptide into PLGA NPs. The miR-539-PLGA.NPs and miR-539-iRGD-PLGA.NPs were prepared and showed a particle size of 300 ± 3 and 306.40 ± 4 nm, respectively. A reduction in human retinal microvascular endothelial cell (HRMEC) viability was shown 48 and 72 h post transfection with miR-539 incorporated in PLGA NPs and iRGD-PLGA.NPs. iRGD-functionalized PLGA NPs caused further significant reduction in cell viability when compared with plain ones, revealing an enhancement in the NP uptake with iRGD-grafted NPs. The current study showed that miR-539-PLGA.NPs and miR-539-iRGD-PLGA.NPs are promising approaches that reduced the viability of HRMECs, suggesting their therapeutic potential in the treatment of CNV.

Bovine mammary alveolar MAC-T cells afford a tool for studies of bovine milk exosomes in drug delivery

Bovine milk exosomes (BMEs) have attracted attention as vehicles for delivering RNA therapeutics. BMEs originate in mammary alveolar cells. Here, we determined whether bovine mammary alveolar MAC-T cells afford a tool to assess RNA delivery by BMEs. MAC-T cells exosomes (MAC-T BMEs) and BMEs were harvested by differential ultracentrifugation. Exosome size, morphology, microRNA content and marker proteins were assessed using nanoparticle tracking analysis, transmission electron microscopy, real-time PCR and immunoblot analysis, respectively. MAC-T cells were genetically engineered to secrete MAC-T BMEs endogenously labeled with a near-infrared fluorescent protein and tissue distribution was compared to fluorophore-labeled BMEs following intravenous injection in C57BL/6 mice. Morphology and size were similar in MAC-T BMEs and BMEs (94 ± 5.8 nm and 101 ± 4.2 nm, p > 0.05). Both preparations expressed miR-320a, miR-200c and let-7a-5p (positive controls) but not miR-1 (negative control). Exosome marker proteins, CD9, CD63, CD81 and Tsg101, were detected in both MAC-T BMEs and BMEs. Distribution in mouse tissues was similar for both preparations, with liver being the primary accumulation site. Collectively, MAC-T BMEs afford a tool for BMEs-based RNA delivery studies.

Ten Years of Knowledge of Nano-Carrier Based Drug Delivery Systems in Ophthalmology: Current Evidence, Challenges, and Future Prospective

The complex drug delivery barrier in the eye reduces the bioavailability of many drugs, resulting in poor therapeutic effects. It is necessary to investigate new drugs through appropriate delivery routes and vehicles. Nanotechnology has utilized various nano-carriers to develop potential ocular drug delivery techniques that interact with the ocular mucosa, prolong the retention time of drugs in the eye, and increase permeability. Additionally, nano-carriers such as liposomes, nanoparticles, nano-suspensions, nano-micelles, and nano-emulsions have grown in popularity as an effective theranostic application to combat different microbial superbugs. In this review, we summarize the nano-carrier based drug delivery system developments over the last decade, particularly review the biology, methodology, approaches, and clinical applications of nano-carrier based drug delivery system in the field of ocular therapeutics. Furthermore, this review addresses upcoming challenges, and provides an outlook on potential future trends of nano-carrier-based drug delivery approaches in ophthalmology, and hopes to eventually provide successful applications for treating ocular diseases.

Distribution of polymeric nanoparticles in the eye: implications in ocular disease therapy

Advantages of polymeric nanoparticles as drug delivery systems include controlled release, enhanced drug stability and bioavailability, and specific tissue targeting. Nanoparticle properties such as hydrophobicity, size, and charge, mucoadhesion, and surface ligands, as well as administration route and suspension media affect their ability to overcome ocular barriers and distribute in the eye, and must be carefully designed for specific target tissues and ocular diseases. This review seeks to discuss the available literature on the biodistribution of polymeric nanoparticles and discuss the effects of nanoparticle composition and administration method on their ocular penetration, distribution, elimination, toxicity, and efficacy, with potential impact on clinical applications.

Suprachoroidally Delivered DNA Nanoparticles Transfect Retina and Retinal Pigment Epithelium/Choroid in Rabbits

Purpose

This study evaluated ocular tolerability and transfectability of nonviral DNA nanoparticles (DNPs) after microneedle-based suprachoroidal (SC) administration, in comparison to subretinal (SR) administration.

Methods

The DNPs consisted of a single copy of plasmid DNA with a polyubiquitin C/luciferase transcriptional cassette compacted with 10 kDa PEG-substituted lysine 30-mer peptides (CK30PEG10k). New Zealand White rabbits (n = 4 per group) received a unilateral SC injection (0.1 mL via a microneedle technique) of ellipsoid-shaped DNPs, rod-shaped DNPs, or saline (negative control). A cohort of rabbits (n = 4) also received a single unilateral SR injection (0.05 mL via a transvitreal approach) of rod-shaped DNPs. At day 7, luciferase activity was measured in the retina and retinal pigment epithelium (RPE)–choroid via bioluminescence assay. A cohort of rabbits received a SC injection of analogous DNPs to assess spread of DNP injectate in the suprachoroidal space (SCS) via optical coherent tomography and histology.

Results

Suprachoroidal injection of DNPs resulted in reversible opening of the SCS circumferentially and posteriorly and was generally well tolerated, with no significant ocular examination score changes, intraocular pressure abnormalities, or changes in electroretinography amplitudes on day 7 compared to the baseline. High luciferase activity was observed in the retina and RPE-choroid of eyes that received SC DNPs (rod and ellipsoid shape) and SR DNPs (rod shape) compared to controls. The mean luciferase activity in RPE-choroid and retina was comparable between SC and SR administrations. Transfection in the RPE-choroid was approximately 10-fold higher than in the retina after either SC or SR administration of DNPs.

Conclusions

Suprachoroidal and SR administration of DNPs resulted in comparable transfection of retina and RPE-choroid.

Translational Relevance

Suprachoroidal delivery of DNPs offers the potential to precisely target chorioretinal tissues while avoiding surgical risks associated with SR injection, and it may offer an office-based nonsurgical gene therapy option for the treatment of retinal diseases.

Delivering Combination Chemotherapies and Targeting Oncogenic Pathways via Polymeric Drug Delivery Systems

The side-effects associated with chemotherapy necessitates better delivery of chemotherapeutics to the tumor. Nanoparticles can load higher amounts of drug and improve delivery to tumors, increasing the efficacy of treatment. Polymeric nanoparticles, in particular, have been used extensively for chemotherapeutic delivery. This review describes the efforts made to deliver combination chemotherapies and inhibit oncogenic pathways using polymeric drug delivery systems. Combinations of chemotherapeutics with other drugs or small interfering RNA (siRNA) combinations have been summarized. Special attention is given to the delivery of drug combinations that involve either paclitaxel or doxorubicin, two popular chemotherapeutics in clinic. Attempts to inhibit specific pathways for oncotherapy have also been described. These include inhibition of oncogenic pathways (including those involving HER2, EGFR, MAPK, PI3K/Akt, STAT3, and HIF-1α), augmentation of apoptosis by inhibiting anti-apoptosis proteins (Bcl-2, Bcl-xL, and survivin), and targeting dysregulated pathways such as Wnt/β-catenin and Hedgehog.

Cell-specific gene therapy driven by an optimized hypoxia-regulated vector reduces choroidal neovascularization

Aberrant growth of blood vessels in the choroid layer of the eye, termed choroidal neovascularization (CNV), is the pathological hallmark of exudative age-related macular degeneration (AMD), causing irreversible blindness among the elderly. Co-localization of proangiogenic factors and hypoxia inducible factors (HIF) in neovascular membranes from AMD eyes suggests the role of hypoxia in pathogenesis of CNV. In order to utilize hypoxic conditions in RPE for therapeutic purposes, we developed an optimized hypoxia regulated, RPE cell-specific gene therapy to inhibit choroidal neovascularization. An adeno-associated virus (AAV2) vector comprising a RPE-specific promoter and HIF-1 response elements (HRE) was designed to regulate production of human endostatin (a powerful angiostatic protein) in RPE. The vector was tested in a mouse model of laser-induced CNV using subretinal delivery. Spectral domain optical coherence tomography (SD-OCT) images from live mice and confocal images from lectin stained RPE flat mount sections demonstrated reduction in CNV areas by 80% compared to untreated eyes. Quantitative real-time polymerase chain reaction (qPCR) confirmed exogenous endostatin mRNA expression from the regulated vector that was significantly elevated 3, 7, and 14 days following laser treatment, but its expression was completely shut off after 45 days. Thus, RPE-specific, hypoxia-regulated delivery of anti-angiogenic proteins could be a valuable therapeutic approach to treat neovascular AMD at the time and in the ocular space where it arises.

KEY POINTS

An optimized gene therapy vector targeting hypoxia and tissue-specific expression has been designed. The inhibitory role of gene therapy vector was tested in a mouse model of laser-induced CNV. An 80% reduction in choroidal neovascularization was achieved by the optimized vector. The expression of endostatin was limited to retinal pigment epithelium and regulated by hypoxia.

Gene delivery nanoparticles to modulate angiogenesis

Angiogenesis is naturally balanced by many pro- and anti-angiogenic factors while an imbalance of these factors leads to aberrant angiogenesis, which is closely associated with many diseases. Gene therapy has become a promising strategy for the treatment of such a disordered state through the introduction of exogenous nucleic acids that express or silence the target agents, thereby engineering neovascularization in both directions. Numerous non-viral gene delivery nanoparticles have been investigated towards this goal, but their clinical translation has been hampered by issues associated with safety, delivery efficiency, and therapeutic effect. This review summarizes key factors targeted for therapeutic angiogenesis and anti-angiogenesis gene therapy, non-viral nanoparticle-mediated approaches to gene delivery, and recent gene therapy applications in pre-clinical and clinical trials for ischemia, tissue regeneration, cancer, and wet age-related macular degeneration. Enhanced nanoparticle design strategies are also proposed to further improve the efficacy of gene delivery nanoparticles to modulate angiogenesis.

Non-viral strategies for ocular gene delivery

The success of gene therapy relies on efficient gene transfer and stable transgene expression. The in vivo efficiency is determined by the delivery vector, route of administration, therapeutic gene, and target cells. While some requirements are common to several strategies, others depend on the target disease and transgene product. Consequently, it is unlikely that a single system is suitable for all applications. This review examines current gene therapy strategies, focusing on non-viral approaches and the use of natural polymers with the eye, and particularly the retina, as their gene delivery target.

Synthetic nanocarriers for the delivery of polynucleotides to the eye

This review is a comprehensive analysis of the progress made so far on the delivery of polynucleotide-based therapeutics to the eye, using synthetic nanocarriers. Attention has been addressed to the capacity of different nanocarriers for the specific delivery of polynucleotides to both, the anterior and posterior segments of the eye, with emphasis on their ability to (i) improve the transport of polynucleotides across the different eye barriers; (ii) promote their intracellular penetration into the target cells; (iii) protect them against degradation and, (iv) deliver them in a long-term fashion way. Overall, the conclusion is that despite the advantages that nanotechnology may offer to the area of ocular polynucleotide-based therapies (especially AS-ODN and siRNA delivery), the knowledge disclosed so far is still limited. This fact underlines the necessity of more fundamental and product-oriented research for making the way of the said nanotherapies towards clinical translation.

Correction of Monogenic and Common Retinal Disorders with Gene Therapy

The past decade has seen major advances in gene-based therapies, many of which show promise for translation to human disease. At the forefront of research in this field is ocular disease, as the eye lends itself to gene-based interventions due to its accessibility, relatively immune-privileged status, and ability to be non-invasively monitored. A landmark study in 2001 demonstrating successful gene therapy in a large-animal model for Leber congenital amaurosis set the stage for translation of these strategies from the bench to the bedside. Multiple clinical trials have since initiated for various retinal diseases, and further improvements in gene therapy techniques have engendered optimism for alleviating inherited blinding disorders. This article provides an overview of gene-based strategies for retinal disease, current clinical trials that engage these strategies, and the latest techniques in genome engineering, which could serve as the next frontline of therapeutic interventions.

Nanoparticle-motivated gene delivery for ophthalmic application

Ophthalmic gene therapy is an intellectual and intentional manipulation of desired gene expression into the specific cells of an eye for the treatment of ophthalmic (ocular) genetic dystrophies and pathological conditions. Exogenous nucleic acids such as DNA, small interfering RNA, micro RNA, and so on, are used for the purpose of managing expression of the desired therapeutic proteins in ocular tissues. The delivery of unprotected nucleic acids into the cells is limited because of exogenous and endogenous degradation modalities. Nanotechnology, a promising and sophisticated cutting edge tool, works as a protective shelter for these therapeutic nucleic acids. They can be safely delivered to the required cells in order to modulate anticipated protein expression. To this end, nanotechnology is seen as a potential and promising strategy in the field of ocular gene delivery. This review focused on current nanotechnology modalities and other promising nonviral strategies being used to deliver therapeutic genes in order to treat various devastating ocular diseases.

Delivery strategies for treatment of age-related ocular diseases: From a biological understanding to biomaterial solutions

Age-related ocular diseases, such as age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma, result in life-long functional deficits and enormous global health care costs. As the worldwide population ages, vision loss has become a major concern for both economic and human health reasons. Due to recent research into biomaterials and nanotechnology major advances have been gained in the field of ocular delivery. This review provides a summary and discussion of the most recent strategies employed for the delivery of both drugs and cells to the eye to treat a variety of age-related diseases. It emphasizes the current challenges and limitations to ocular delivery and how the use of innovative materials can overcome these issues and ultimately provide treatment for age-related degeneration and regeneration of lost tissues. This review also provides critical considerations and an outlook for future studies in the field of ophthalmic delivery.

Nanoengineering of therapeutics for retinal vascular disease

Retinal vascular diseases, including diabetic retinopathy, neovascular age related macular degeneration, and retinal vein occlusion, are leading causes of blindness in the Western world. These diseases share several common disease mechanisms, including vascular endothelial growth factor (VEGF) signaling, hypoxia, and inflammation, which provide opportunities for common therapeutic strategies. Treatment of these diseases using laser therapy, anti-VEGF injections, and/or steroids has significantly improved clinical outcomes. However, these strategies do not address the underlying root causes of pathology, and may have deleterious side effects. Furthermore, many patients continue to progress toward legal blindness despite receiving regular therapy. Nanomedicine, the engineering of therapeutics at the 1-100 nm scale, is a promising approach for improving clinical management of retinal vascular diseases. Nanomedicine-based technologies have the potential to revolutionize the treatment of ophthalmology, through enabling sustained release of drugs over several months, reducing side effects due to specific targeting of dysfunctional cells, and interfacing with currently "undruggable" targets. We will discuss emerging nanomedicine-based applications for the treatment of complications associated with retinal vascular diseases, including angiogenesis and inflammation.

Nanoparticle-based technologies for retinal gene therapy

For patients with hereditary retinal diseases, retinal gene therapy offers significant promise for the prevention of retinal degeneration. While adeno-associated virus (AAV)-based systems remain the most popular gene delivery method due to their high efficiency and successful clinical results, other delivery systems, such as non-viral nanoparticles (NPs) are being developed as additional therapeutic options. NP technologies come in several categories (e.g., polymer, liposomes, peptide compacted DNA), several of which have been tested in mouse models of retinal disease. Here, we discuss the key biochemical features of the different NPs that influence how they are internalized into cells, escape from endosomes, and are delivered into the nucleus. We review the primary mechanism of NP uptake by retinal cells and highlight various NPs that have been successfully used for in vivo gene delivery to the retina and RPE. Finally, we consider the various strategies that can be implemented in the plasmid DNA to generate persistent, high levels of gene expression.

Therapeutic face of RNAi: in vivo challenges

INTRODUCTION

RNA interference is a sequence-specific gene silencing phenomenon in which small interfering RNAs (siRNAs) can trigger gene transcriptional and post-transcriptional silencing. This phenomenon represents an emerging therapeutic approach for in vivo studies by efficient delivery of specific synthetic siRNAs against diseases. Therefore, simultaneous development of synthetic siRNAs along with novel delivery techniques is considered as novel and interesting therapeutic challenges.

AREAS COVERED

This review provides a basic explanation to siRNA signaling pathways and their therapeutic challenges. Here, we provide a comprehensive explanation to failed and successful trials and their in vivo challenges.

EXPERT OPINION

Specific, efficient and targeted delivery of siRNAs is the major concern for their in vivo administrations. Also, anatomical barriers, drug stability and availability, immunoreactivity and existence of various delivery routes, different genetic backgrounds are major clinical challenges. However, successful administration of siRNA-based drugs is expected during foreseeable features. But, their systemic applications will depend on strong targeted drug delivery strategies.

Polymer nanoparticles for drug and small silencing RNA delivery to treat cancers of different phenotypes

Advances in nanotechnology have provided powerful and efficient tools in the development of cancer diagnosis and therapy. There are numerous nanocarriers that are currently approved for clinical use in cancer therapy. In recent years, biodegradable polymer nanoparticles have attracted a considerable attention for their ability to function as a possible carrier for target-specific delivery of various drugs, genes, proteins, peptides, vaccines, and other biomolecules in humans without much toxicity. This review will specifically focus on the recent advances in polymer-based nanocarriers for various drugs and small silencing RNA's loading and delivery to treat different types of cancer.

Retinal angiogenesis suppression through small molecule activation of p53

Neovascular age-related macular degeneration is a leading cause of irreversible vision loss in the Western world. Cytokine-targeted therapies (such as anti-vascular endothelial growth factor) are effective in treating pathologic ocular angiogenesis, but have not led to a durable effect and often require indefinite treatment. Here, we show that Nutlin-3, a small molecule antagonist of the E3 ubiquitin protein ligase MDM2, inhibited angiogenesis in several model systems. We found that a functional p53 pathway was essential for Nutlin-3-mediated retinal antiangiogenesis and disruption of the p53 transcriptional network abolished the antiangiogenic activity of Nutlin-3. Nutlin-3 did not inhibit established, mature blood vessels in the adult mouse retina, suggesting that only proliferating retinal vessels are sensitive to Nutlin-3. Furthermore, Nutlin-3 inhibited angiogenesis in nonretinal models such as the hind limb ischemia model. Our work demonstrates that Nutlin-3 functions through an antiproliferative pathway with conceivable advantages over existing cytokine-targeted antiangiogenesis therapies.

Comparative study of laser-induced choroidal neovascularization in rats by paraffin sections, frozen sections and high-resolution optical coherence tomography

PURPOSE

The purpose of this study was to demonstrate the value of a quantitative study concerning experimental choroidal neovascularization (CNV) tissue by correlating the paraffin sections and frozen sections with optical coherence tomography (OCT) images.

METHODS

After OCT imaging was performed, four right eyes from the normal Brown Norway (BN) rats were made into paraffin sections and four left eyes were made into frozen sections. Laser photocoagulation was performed on the right eyes of the other 32 BN rats to induce CNV; these rats then were divided into two groups. After the OCT imaging was performed, four eyes were made into serial paraffin sections in Group A or frozen sections in Group B at 1 week after laser photocoagulation, and weekly for 4 weeks. A quantitative comparison of histopathological images and OCT images was performed.

RESULTS

The thickness of the sensory retina and choroid of normal BN rats in paraffin sections was perceptibly less than that in the frozen sections, and the thickness of the sensory retina in the frozen sections was similar to that measured in the OCT images. The maximum thickness of the CNV tissue in the frozen sections was greater than that in the paraffin sections, but similar to that measured in the OCT images from week 1 to week 4.

CONCLUSIONS

Only the frozen sections accurately matched the high-resolution OCT images because of the processing artifacts in the paraffin sections. In further quantitative studies on experimental CNV, the frozen sections may be more preferable if the thickness of the CNV tissue is to be measured and compared.

Lentivirus vector-mediated knockdown of erythropoietin-producing hepatocellular carcinoma receptors B4 inhibits laser-induced choroidal neovascularization

PURPOSE

To evaluate the efficacy of erythropoietin-producing hepatocellular carcinoma receptors B4 (EphB4) knockdown on the development of laser-induced choroidal neovascularization (CNV) in vivo.

METHODS

We constructed recombinant lentiviral vectors (Lv) Lv-shRNA-EphB4 to specifically knock down the expression of EphB4. The mRNA and protein expression of EphB4 was investigated by real-time reverse transcription-polymerase chain reaction (RT-PCR) and western blot. CNV was induced by laser photocoagulation in C57BL/6 mice. The mice were then randomly assigned to be intravitreally injected with phosphate-buffered saline (PBS), Lv-shRNA-EphB4 recombinant lentivirus, or an unrelated shRNA recombinant lentivirus (pFU LV-shRNA-NC). An uninjected group was used as the control. Fundus fluorescein angiography (FFA), histologic analysis, and choroidal flat mounts analysis were applied to evaluate the inhibition of CNV after an intravitreal injection.

RESULTS

Transfection of Lv-shRNA-EphB4 led to the knockdown of EphB4, and EphB4 mRNA was down-regulated by about 80%. FFA and histologic analysis revealed that the leakage areas and the mean thickness of CNV were much smaller in the Lv-shRNA-EphB4 group than in the PBS-treated, pFU Lv-shRNA-NC group and the non-injection group. Choroidal flat mounts showed significantly less leakage and smaller leakage areas in the Lv-shRNA-EphB4 group than those in other groups.

CONCLUSION

Knocking down the expression of EphB4 exerts an inhibitory effect on CNV in vivo. It may provide a potential strategy for the treatment of CNV.

Polymeric vectors for ocular gene delivery

Gene therapy holds promise for the treatment of many inherited and acquired diseases of the eye. Successful ocular gene therapy interventions depend on efficient gene transfer to targeted cells with minimal toxicity. A major challenge is to overcome both intracellular and extracellular barriers associated with ocular gene delivery. Numerous viral and nonviral vectors were explored to improve transfection efficiency. Among nonviral delivery systems, polymeric vectors have gained significant attention in recent years owing to their nontoxic and non-immunogenic nature. Polyplexes or nanoparticles can be prepared by interaction of cationic polymers with DNA, which facilitate cellular uptake, endolysosomal escape and nuclear entry through active mechanisms. Chemical modification of these polymers allows for the generation of flexible delivery vectors with desirable properties. In this article several synthetic and natural polymeric systems utilized for ocular gene delivery are discussed.

From oxygen to erythropoietin: relevance of hypoxia for retinal development, health and disease

Photoreceptors and other cells of the retina consume large quantities of energy to efficiently convert light information into a neuronal signal understandable by the brain. The necessary energy is mainly provided by the oxygen-dependent generation of ATP in the numerous mitochondria of retinal cells. To secure the availability of sufficient oxygen for this process, the retina requires constant blood flow through the vasculature of the retina and the choroid. Inefficient supply of oxygen and nutrients, as it may occur in conditions of disturbed hemodynamics or vascular defects, results in tissue ischemia or hypoxia. This has profound consequences on retinal function and cell survival, requiring an adaptational response by cells to cope with the reduced oxygen tension. Central to this response are hypoxia inducible factors, transcription factors that accumulate under hypoxic conditions and drive the expression of a large variety of target genes involved in angiogenesis, cell survival and metabolism. Prominent among these factors are vascular endothelial growth factor and erythropoietin, which may contribute to normal angiogenesis during development, but may also cause neovascularization and vascular leakage under pathologically reduced oxygen levels. Since ischemia and hypoxia may have a role in various retinal diseases such as diabetic retinopathy and retinopathy of prematurity, studying the cellular and molecular response to reduced tissue oxygenation is of high relevance. In addition, the concept of preconditioning with ischemia or hypoxia demonstrates the capacity of the retina to activate endogenous survival mechanisms, which may protect cells against a following noxious insult. Part of these mechanisms is the local production of protective factors such as erythropoietin. Due to its plethora of effects in the retina including neuro- and vaso-protective activities, erythropoietin has gained strong interest as potential therapeutic factor for retinal degenerative diseases.