G-quartet oligonucleotide mediated delivery of proteins into photoreceptors and retinal pigment epithelium via intravitreal injection

Intravitreal AAV-IKV mediated delivery of decorin inhibits choroidal neovascularization, fibrosis, inflammation and elevates autophagy

Age-related macular degeneration (AMD) is the most common cause of blindness in the elderly. The exudative or wet form of AMD is caused by choroidal neovascularization (CNV) and subsequently a macular edema. Wet AMD can be effectively treated with anti-vascular endothelial growth factor (VEGF) therapies. However, despite treatment, more than half of patients continue to lose vision due to a lack of compliance with frequent intravitreal injections, failure to adequately respond to anti-VEGF therapy and emergence of fibrotic scars underneath the retina. In this study we investigated the use of our retinal penetrating AAV for delivery of human decorin (AAV-IKV-Decorin) in a murine model of laser induced CNV. Our results indicate that following a single intravitreal injection, decorin is highly expressed in the outer retina of AAV-IKV-Decorin injected mice and such mice exhibit significantly less neovascularization in laser induced CNV relative to mice injected with an AAV-IKV-Aflibercept, an AAV expressing an anti-VEGF. AAV-IKV-Decorin also significantly inhibited fibrosis, reduced inflammatory markers and increased autophagy.

Retinal Penetrating Adeno-Associated Virus

Purpose

The most common method of delivery of genes to the outer retina uses recombinant adeno-associated virus (AAV) injected into the subretinal space using a surgical procedure. In contrast, most drugs are delivered to the retina using an intravitreal approach in an office setting. The objective of the current study was to develop AAV vectors that can reach the outer retina via intravitreal injection.

Methods

Recently, we described a molecular chaperone (Nuc1) that enhanced the penetration of small and large molecules, including AAV, into the retina. The Nuc1 amino acid sequence or a truncated version of Nuc1 (IKV) was genetically incorporated into an exposed loop of AAV2/9 VP1 protein. These novel recombinant AAV vectors expressing green fluorescent protein (GFP) or nuclear factor erythroid 2 p45-related factor 2 (Nrf2) were injected into the vitreous of C57Bl/6J or Nrf2 knockout mice, respectively. The amount of GFP expression or oxidative stress as measured by 8-Hydroxy-2'-deoxyguanosine staining in C57Bl/6J or Nrf2 knockout mice, respectively, was quantified.

Results

Incorporation of Nuc1 into AAV2/9 did not lead to significant expression of GFP in the murine retina. However, incorporation of IKV into AAV2/9 led to robust expression of GFP in photoreceptors and retinal pigment epithelium (RPE) via the intravitreal and subretinal routes of delivery. Furthermore, expression of Nrf2 using an IKV vector led to a reduction in oxidative stress in the retina of C57Bl/6J and Nrf2 knockout mice.

Conclusions

We have developed a novel AAV vector that enables delivery of transgenes to the outer retina of mice, including photoreceptors and RPE following intravitreal injection.

Cell-Penetrating Chaperone Nuc1 for Small- and Large-Molecule Delivery Into Retinal Cells and Tissues

Purpose

There are currently no means available for the efficient delivery of recombinant proteins into retinal cells in vivo. Although cell-penetrating peptides have been somewhat effective in protein delivery to the retina, they generally require conjugation chemistry with the payload, negatively impacting function of the therapeutic protein. In this study, we developed a novel peptide (Nuc1) that acts as a chaperone for delivery of small and large molecules, including steroids, peptides, antibodies, recombinant proteins, and viruses (adeno-associated viruses [AAVs]) across biological membranes in vivo without the need for conjugation.

Methods

Nuc1 peptide was designed based on sequences known to bind heparan sulfate proteoglycans and nucleolin found on the surface of retinal cells. Nuc1 was injected into the vitreous of mice with a variety of molecules and retinas examined for uptake and function of these molecules.

Results

Nuc1 engages the process of macropynocytosis for cell entry. The delivery of functional recombinant X-linked inhibitor of apoptosis protein to photoreceptors via the intravitreal route of injection inhibited retinal apoptosis. Nuc1 was found to enhance the delivery of anti-VEGF antibodies delivered intravitreally or topically in models of age-related macular degeneration (AMD). Nuc1 enhanced delivery of decorin, facilitating significant inhibition of neovascularization and fibrosis in a model of AMD. Finally, Nuc1 was found to enhance penetration of retinal cells and tissues by AAV via both the subretinal and intravitreal routes of injection.

Conclusions

Nuc1 shows promise as a novel approach for the delivery of recombinant proteins into retinal cells in vivo.

Fluorescent Polymer-AS1411-Aptamer Probe for dSTORM Super-Resolution Imaging of Endogenous Nucleolin

Nucleolin is a multifunctional protein involved in essential biological processes. To precisely localize it and unravel its different roles in cells, fluorescence imaging is a powerful tool, especially super-resolution techniques. Here, we developed polymer-aptamer probes, both small and bright, adapted to direct stochastic optical reconstruction microscopy (dSTORM). Well-defined fluorescent polymer chains bearing fluorophores (AlexaFluor647) and a reactive end group were prepared via RAFT polymerization. The reactive end-group was then used for the oriented conjugation with AS1411, a DNA aptamer that recognizes nucleolin with high affinity. Conjugation via strain-promoted alkyne/azide click chemistry (SPAAC) between dibenzylcyclooctyne-ended fluorescent polymer chains and 3'-azido-functionalized nucleic acids proved to be the most efficient approach. In vitro and in cellulo evaluations demonstrated that selective recognition for nucleolin was retained. Their brightness and small size make these polymer-aptamer probes an appealing alternative to immunofluorescence, especially for super-resolution (10-20 nm) nanoscopy. dSTORM imaging demonstrated the ability of our fluorescent polymer-aptamer probe to provide selective and super-resolved detection of cell surface nucleolin.

Progress in cancer drug delivery based on AS1411 oriented nanomaterials

Targeted cancer therapy has become one of the most important medical methods because of the spreading and metastatic nature of cancer. Based on the introduction of AS1411 and its four-chain structure, this paper reviews the research progress in cancer detection and drug delivery systems by modifying AS1411 aptamers based on graphene, mesoporous silica, silver and gold. The application of AS1411 in cancer treatment and drug delivery and the use of AS1411 as a targeting agent for the detection of cancer markers such as nucleoli were summarized from three aspects of active targeting, passive targeting and targeted nucleic acid apharmers. Although AS1411 has been withdrawn from clinical trials, the research surrounding its structural optimization is still very popular. Further progress has been made in the modification of nanoparticles loaded with TCM extracts by AS1411.

CRISPR genome engineering for retinal diseases

Novel gene therapy treatments for inherited retinal diseases have been at the forefront of translational medicine over the past couple of decades. Since the discovery of CRISPR mechanisms and their potential application for the treatment of inherited human conditions, it seemed inevitable that advances would soon be made using retinal models of disease. The development of CRISPR technology for gene therapy and its increasing potential to selectively target disease-causing nucleotide changes has been rapid. In this chapter, we discuss the currently available CRISPR toolkit and how it has been and can be applied in the future for the treatment of inherited retinal diseases. These blinding conditions have until now had limited opportunity for successful therapeutic intervention, but the discovery of CRISPR has created new hope of achieving such, as we discuss within this chapter.

Simultaneous Targeting of Two Master Regulators of Apoptosis with Dual-Action PNA- and DNA-Peptide Conjugates

Conjugation of peptides with oligonucleotides offers opportunities for combining the strengths of both biopolymer classes. Herein, we show that the combination of a peptide-based module with an antisense oligonucleotide module provides for enhancements of potency and a widened scope of cell delivery options. The peptide unit comprises a Smac mimetic compound (SMCs) which antagonizes the action of inhibitor of apoptosis proteins (IAPs) frequently overexpressed in cancer cells. To counteract SMC resistance, the antisense module downregulates the cellular FLICE-like protein (c-FLIP), a master regulator of the extrinsic apoptosis pathway. We compared c-FLIP antisense units based on oligophosphorothioate (PSO) and peptide nucleic acid (PNA) architectures. Owing to the ease of synthesis, PNA conjugates combined with a cell penetrating peptide (CPP) offer a seemingly ideal solution for cell delivery of dual activity agents. However, our investigations revealed that such congeners have to be handled with care to avoid off-target effects. By contrast, PSO conjugates provided a more robust and specific activity for inducing death of SMC-resistant A549 cells due to a simultaneous activation of caspases and c-FLIP knockdown. We show that lipofection is a convenient approach for delivery of peptide-PSO conjugates into cells. The results highlight that the combination of the peptide and the DNA world confers properties inaccessible by the unconjugated components.

Antagonist of nucleolin, N6L, inhibits neovascularization in mouse models of retinopathies

Retinal vascular diseases (RVD) have been identified as a major cause of blindness worldwide. These pathologies, including the wet form of age-related macular degeneration, retinopathy of prematurity, and diabetic retinopathy are currently treated by intravitreal delivery of anti-vascular endothelial growth factor (VEGF) agents. However, repeated intravitreal injections can lead to ocular complications and resistance to these treatments. Thus, there is a need to find new targeted therapies. Nucleolin regulates the endothelial cell (EC) activation and angiogenesis. In previous studies, we designed a pseudopeptide, N6L, that binds the nucleolin and blocks the tumor angiogenesis. In this study, the effect of N6L was investigated in two experimental models of retinopathies including oxygen-induced retinopathy (OIR) and choroidal neovascularization (CNV). We found that in mouse OIR, intraperitoneal injection of N6L is delivered to activated ECs and induced a 50% reduction of pathological neovascularization. The anti-angiogenic effect of N6L has been tested in CNV model in which the systemic injection of N6L induced a 33% reduction of angiogenesis. This effect is comparable to those obtained with VEGF-trap, a standard of care drug for RVD. Interestingly, with preventive and curative treatments, neoangiogenesis is inhibited by 59%. Our results have potential interest in the development of new therapies targeting other molecules than VEGF for RVD.

Gene Therapy for Inherited Retinal Degeneration

Inherited retinal degeneration (IRD), a group of rare retinal diseases that primarily lead to the progressive loss of retinal photoreceptor cells, can be inherited in all modes of inheritance: autosomal dominant (AD), autosomal recessive (AR), X-linked (XL), and mitochondrial. Based on the pattern of inheritance of the dystrophy, retinal gene therapy has 2 main strategies. AR, XL, and AD IRDs with haploinsufficiency can be treated by inserting a functional copy of the gene using either viral or nonviral vectors (gene augmentation). Different types of viral vectors and nonviral vectors are used to transfer plasmid DNA both in vitro and in vivo. AD IRDs with gain-of-function mutations or dominant-negative mutations can be treated by disrupting the mutant allele with (and occasionally without) gene augmentation. This review article aims to provide an overview of ocular gene therapy for treating IRDs using gene augmentation with viral or nonviral vectors or gene disruption through different gene-editing tools, especially with the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) system.

CRISPR-Cas9 genome engineering: Treating inherited retinal degeneration

Gene correction is a valuable strategy for treating inherited retinal degenerative diseases, a major cause of irreversible blindness worldwide. Single gene defects cause the majority of these retinal dystrophies. Gene augmentation holds great promise if delivered early in the course of the disease, however, many patients carry mutations in genes too large to be packaged into adeno-associated viral vectors and some, when overexpressed via heterologous promoters, induce retinal toxicity. In addition to the aforementioned challenges, some patients have sustained significant photoreceptor cell loss at the time of diagnosis, rendering gene replacement therapy insufficient to treat the disease. These patients will require cell replacement to restore useful vision. Fortunately, the advent of induced pluripotent stem cell and CRISPR-Cas9 gene editing technologies affords researchers and clinicians a powerful means by which to develop strategies to treat patients with inherited retinal dystrophies. In this review we will discuss the current developments in CRISPR-Cas9 gene editing in vivo in animal models and in vitro in patient-derived cells to study and treat inherited retinal degenerative diseases.

G-quartet oligonucleotide mediated delivery of functional X-linked inhibitor of apoptosis protein into retinal cells following intravitreal injection

There is currently no efficient method available for the delivery of full length functional proteins into the cytoplasm of retinal cells in vivo. Historically, the most successful approach for the treatment of retinal diseases has been intravitreal injection of antibodies or recombinant proteins, but this approach is not yet utilized for the delivery of proteins that require intracellular access for a therapeutic effect. Here we describe a platform for the delivery of functional proteins into ganglion cells, photoreceptors and retinal pigment epithelium via intravitreal injection. A nucleolin binding aptamer, AS1411, was biotinylated and complexed with traptavidin and utilized as a platform for the delivery of GFP or X-linked inhibitor of apoptosis (XIAP) proteins by intravitreal injection in BALB/c mice. Retinal sections were analyzed for uptake of proteins in the retina. Apoptosis was induced by intravitreal injection of N-methyl-D-aspartate (NMDA). Retinas were harvested for analysis of TUNEL and caspase 3/7 activity. Intravitreal injection of AS1411-directed GFP or XIAP complexes enabled delivery of these proteins into ganglion cells, photoreceptors and retinal pigment epithelium in vivo. AS1411-XIAP complexes conferred significant protection to cells in the outer and inner nuclear layers following NMDA induced apoptosis. A concomitant decrease in activity of Caspase 3/7 was observed in eyes injected with the AS1411-XIAP complex. In conclusion, AS1411 can be used as a platform for the delivery of therapeutic proteins into retinal cells. This approach can potentially be utilized to introduce a large variety of therapeutically relevant proteins that are previously well characterized to maintain the structural integrity and function of retina, thus, preventing vision loss due to ocular trauma or inherited retinal degeneration.