Peripapillary Intravitreal Injection Improves AAV-Mediated Retinal Transduction

Recombinant adeno-associated virus with anti-tumor necrosis factor-alpha in an experimental autoimmune uveitis model

Uveitis treatment is associated with side effects and inconsistent outcomes. Existing treatments often fail to provide targeted and sustained relief; thus, novel therapeutic approaches are needed. Among these, gene therapy using adeno-associated virus (AAV) vectors target specific retinal cells, show low immunogenicity, and demonstrate sustained gene expression, making it a potential advancement in uveitis treatment. Therefore, we utilized a AAV2 system encapsulating encoded anti-tumor necrosis factor-alpha (TNF-α) antibody to assess its efficacy in the treatment of experimental autoimmune uveitis (EAU) in mice. Compared with the AAV2-GFP group, AAV2-ADA-injected mice showed significantly reduced clinical, OCT, and histopathological scores in EAU with lower percentages of Th1 and Th17 cells in the eyes and higher percentages of Treg cells in the draining lymph nodes (LN). This study demonstrated the safety and effects of AAV2-ADA in EAU treatment, providing a promising therapeutic strategy for uveitis.

An improved method of transducing retinal ganglion cells using AAV via transpupillary injection in adult mouse eyes

Purpose

Intravitreal injection of adeno-associated virus (AAV) vectors is a good approach for transducing retinal ganglion cells (RGCs) in mice. It allows for high transduction efficiency and is relatively specific to RGCs. To deliver vectors, most studies use a transscleral approach that can have potentially negative effects, causing damage to the lens or retina. We optimized the intravitreal injection method using a transpupillary approach to minimize ocular damage and efficiently transfect RGCs.

Methods

C57BL/6J mice were anesthetized, and their irises were dilated. The eyeball was held with forceps while a small, full-thickness incision was made halfway between the center and periphery of the cornea. Using a bent 35-gauge blunt needle, the tip was navigated through the incision across the anterior chamber to reach the distal aspect of the pupil. The needle was inserted through the pupil, swept around the lens, and entered the vitreous, delivering expression vectors containing cytomegalovirus (CMV) promoter-driving green fluorescent protein (AAV-CMV-GFP) into the vitreous chamber. Fourteen days after injection, live fluorescent fundus images were taken, followed by immunostaining for GFP.

Results

With the improved injection technique, the lens remained clear and undamaged. Fundus imaging and GFP staining showed that over 90% of the mouse retinas sustained no visible damage. Retinas injected via the transpupillary approach also exhibited GFP transduction throughout the ganglion cell layer.

Conclusions

Transpupillary intravitreal injection reduces the potential risk compared to the transscleral approach, offering a promising and efficient method for delivering reporter genes to RGCs and ensuring high levels of gene expression without damage to the lens or retina.

A journey through the world of vitreous

Vitreous, one of the largest components of the human eye, mostly contains water. Despite decades of studying the vitreous structure, numerous unanswered questions still remain, fueling ongoing active research. We attempt to provide a comprehensive overview of the current understanding of the development, morphology, biochemical composition, and function of the vitreous. We emphasize the impact of the vitreous structure and composition on the distribution of drugs. Fast-developing imaging technologies, such as modern optical coherence tomography, unlocked multiple new approaches, offering the potential for in vivo study of the vitreous structure. They allowed to analyze in vivo a range of vitreous structures, such as posterior precortical vitreous pockets, Cloquet canal, channels that interconnect them, perivascular vitreous fissures, and cisterns. We provide an overview of such imaging techniques and their principles and of some challenges in visualizing vitreous structures. Finally, we explores the potential of combining the latest technologies and machine learning to enhance our understanding of vitreous structures.

A Comparative Analysis of Models for AAV-Mediated Gene Therapy for Inherited Retinal Diseases

Inherited retinal diseases (IRDs) represent a diverse group of genetic disorders leading to progressive degeneration of the retina due to mutations in over 280 genes. This review focuses on the various methodologies for the preclinical characterization and evaluation of adeno-associated virus (AAV)-mediated gene therapy as a potential treatment option for IRDs, particularly focusing on gene therapies targeting mutations, such as those in the RPE65 and FAM161A genes. AAV vectors, such as AAV2 and AAV5, have been utilized to deliver therapeutic genes, showing promise in preserving vision and enhancing photoreceptor function in animal models. Despite their advantages-including high production efficiency, low pathogenicity, and minimal immunogenicity-AAV-mediated therapies face limitations such as immune responses beyond the retina, vector size constraints, and challenges in large-scale manufacturing. This review systematically compares different experimental models used to investigate AAV-mediated therapies, such as mouse models, human retinal explants (HREs), and induced pluripotent stem cell (iPSC)-derived retinal organoids. Mouse models are advantageous for genetic manipulation and detailed investigations of disease mechanisms; however, anatomical differences between mice and humans may limit the translational applicability of results. HREs offer valuable insights into human retinal pathophysiology but face challenges such as tissue degradation and lack of systemic physiological effects. Retinal organoids, on the other hand, provide a robust platform that closely mimics human retinal development, thereby enabling more comprehensive studies on disease mechanisms and therapeutic strategies, including AAV-based interventions. Specific outcomes targeted in these studies include vision preservation and functional improvements of retinas damaged by genetic mutations. This review highlights the strengths and weaknesses of each experimental model and advocates for their combined use in developing targeted gene therapies for IRDs. As research advances, optimizing AAV vector design and delivery methods will be critical for enhancing therapeutic efficacy and improving clinical outcomes for patients with IRDs.

Gene Therapy Activates Retinal Pigment Epithelium Cell Proliferation for Age-related Macular Degeneration in a Mouse Model

OBJECTIVE

Age-related macular degeneration (AMD) is a degenerative retinal disease. The degeneration or death of retinal pigment epithelium (RPE) cells is implicated in the pathogenesis of AMD. This study aimed to activate the proliferation of RPE cells in vivo by using an adeno-associated virus (AAV) vector encoding β-catenin to treat AMD in a mouse model.

METHODS

Mice were intravitreally injected with AAV2/8-Y733F-VMD2-β-catenin for 2 or 4 weeks, and β-catenin expression was measured using immunofluorescence staining, real-time quantitative reverse transcription polymerase chain reaction (PCR), and Western blotting. The function of β-catenin was determined using retinal flat mounts and laser-induced damage models. Finally, the safety of AAV2/8-Y733F-VMD2-β-catenin was evaluated by multiple intravitreal injections.

RESULTS

AAV2/8-Y733F-VMD2-β-catenin induced the expression of β-catenin in RPE cells. It activated the proliferation of RPE cells and increased cyclin D1 expression. It was beneficial to the recovery of laser-induced damage by activating the proliferation of RPE cells. Furthermore, it could induce apoptosis of RPE cells by increasing the expression of Trp53, Bax and caspase3 while decreasing the expression of Bcl-2.

CONCLUSION

AAV2/8-Y733F-VMD2-β-catenin increased β-catenin expression in RPE cells, activated RPE cell proliferation, and helped mice heal from laser-induced eye injury. Furthermore, it could induce the apoptosis of RPE cells. Therefore, it may be a safe approach for AMD treatment.

Retinal Organoids and Retinal Prostheses: An Overview

Despite the progress of modern medicine in the last decades, millions of people diagnosed with retinal dystrophies (RDs), such as retinitis pigmentosa, or age-related diseases, such as age-related macular degeneration, are suffering from severe visual impairment or even legal blindness. On the one hand, the reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) and the progress of three-dimensional (3D) retinal organoids (ROs) technology provide a great opportunity to study, understand, and even treat retinal diseases. On the other hand, research advances in the field of electronic retinal prosthesis using inorganic photovoltaic polymers and the emergence of organic semiconductors represent an encouraging therapeutical strategy to restore vision to patients at the late onset of the disease. This review will provide an overview of the latest advancement in both fields. We first describe the retina and the photoreceptors, briefly mention the most used RD animal models, then focus on the latest RO differentiation protocols, carry out an overview of the current technology on inorganic and organic retinal prostheses to restore vision, and finally summarize the potential utility and applications of ROs.

A look into retinal organoids: methods, analytical techniques, and applications

Inherited retinal diseases (IRDs) cause progressive loss of light-sensitive photoreceptors in the eye and can lead to blindness. Gene-based therapies for IRDs have shown remarkable progress in the past decade, but the vast majority of forms remain untreatable. In the era of personalised medicine, induced pluripotent stem cells (iPSCs) emerge as a valuable system for cell replacement and to model IRD because they retain the specific patient genome and can differentiate into any adult cell type. Three-dimensional (3D) iPSCs-derived retina-like tissue called retinal organoid contains all major retina-specific cell types: amacrine, bipolar, horizontal, retinal ganglion cells, Müller glia, as well as rod and cone photoreceptors. Here, we describe the main applications of retinal organoids and provide a comprehensive overview of the state-of-art analysis methods that apply to this model system. Finally, we will discuss the outlook for improvements that would bring the cellular model a step closer to become an established system in research and treatment development of IRDs.