The Role of Subretinal Injection in Ophthalmic Surgery: Therapeutic Agent Delivery and Other Indications

Co-delivery of antioxidants and siRNA-VEGF: promising treatment for age-related macular degeneration

Current treatments for retinal disorders are anti-angiogenic agents, laser photocoagulation, and photodynamic therapies. These conventional treatments focus on reducing abnormal blood vessel formation in the retina, which, in a low-oxygen environment, can lead to harmful proliferation of endothelial cells. This results in dysfunctional, leaky blood vessels that cause retinal edema, hemorrhage, and vision loss. Age-related Macular Degeneration is a primary cause of vision loss and blindness in the elderly, impacting around 20% of those over 50 years old. This complex disease is also closely related to oxidative stress in retina. In this review, we explore the challenge of treating retinal diseases, alternatives and possibilities of enhancing the effectiveness of therapies using co-delivery systems containing both antiangiogenic and antioxidant therapeutic agents. Despite recent proposals potential, the lack of extensive clinical studies on the long-term outcomes and optimal combinations of therapies means that the full risk profile and effectiveness of combined therapy are not yet completely understood. These factors must be carefully considered and managed by healthcare providers to optimize treatment outcomes and ensure patient safety.

dCasMINI-mediated therapy rescues photoreceptors degeneration in a mouse model of retinitis pigmentosa

Retinitis pigmentosa (RP) is characterized by degeneration of rod and cone photoreceptors that progresses to irreversible blindness. Now, there are no mutation-agnostic approaches to treat RP. Here, we utilized a single adeno-associated virus (AAV)-based CRISPR activation system to activate phosphodiesterase 6B (Pde6b) to mitigate the severe degeneration in Pde6anmf363 mice. We demonstrate that transcriptional activation of Pde6b can rescue the loss of Pde6a, with preservation of retinal structure, restoration of electroretinography responses, and improvement of visual function as assessed by optokinetic response and looming-induced escape behaviors. These findings demonstrate the therapeutic potential of a dCasMINI-mediated activation strategy that provides a mutation-independent treatment for retinal degeneration. This study offers a promising therapeutic approach for RP and potentially other forms of genetic diseases.

Stem cell-based therapies for retinal diseases: focus on clinical trials and future prospects

Stem cell-based therapy has gained importance over the past decades due to huge advances in science and technology behind the generation and directed differentiation of pluripotent cells from embryos and adult cells. Preclinical proof-of-concept studies have been followed by clinical trials showing efficacy and safety of transplantation of stem cell-based therapy, which are beginning to establish this as a modality of treatment. Disease candidates of interest are primarily conditions that may benefit from replacing dead or dying cells, including advanced inherited retinal dystrophies and age-related macular degeneration, and predominantly seek to transplant either RPE or photoreceptors, although neurotrophic approaches have also been trialed. Whilst a consensus has yet to be reached about the best stage/type of cells for transplantation (stem cells, progenitor cells, differentiated RPE and photoreceptors) and the methods of implantation (sheet, suspension), several CTs have shown safety. There remain potential concerns regarding tumorigenicity and immune rejection; however, with ongoing improvements in cell generation, selection, and delivery, these can be minimized. Earlier studies showed efficacy with immunosuppressive drugs to prevent rejection, and recent donor-matched transplants have avoided the need for immunosuppression. Retinal regenerative medicine is a challenging field and is in a nascent stage but holds tremendous promise. This narrative review delves into the current understanding of stem cells and the latest clinical trials of retinal cell transplantation.

Voretigene neparvovec for inherited retinal dystrophy due to RPE65 mutations: a scoping review of eligibility and treatment challenges from clinical trials to real practice

Biallelic mutations in the RPE65 gene affect nearly 8% of Leber Congenital Amaurosis and 2% of Retinitis Pigmentosa cases. Voretigene neparvovec (VN) is the first gene therapy approach approved for their treatment. To date, real life experience has demonstrated functional improvements following VN treatment, which are consistent with the clinical trials outcomes. However, there is currently no consensus on the characteristics for eligibility for VN treatment. We reviewed relevant literature to explore whether recommendations on patient eligibility can be extrapolated following VN marketing. We screened 166 papers through six research questions, following scoping reviews methodology, to investigate: (1) the clinical and genetic features considered in VN treatment eligibility; (2) the psychophysical tests and imaging modalities used in the pre-treatment and follow-up; (3) the potential correlations between visual function and retinal structure that can be used to define treatment impact on disease progression; (4) retinal degeneration; (5) the most advanced testing modalities; and (6) the impact of surgical procedure on treatment outcomes. Current gaps concerning patients' eligibility in clinical settings, such as pre-treatment characteristics and outcomes are not consistently reported across the studies. No upper limit of retinal degeneration can be defined as the univocal factor in patient eligibility, although evidence suggested that the potential for function rescue is related to the preservation of photoreceptors before treatment. In general, paediatric patients retain more viable cells, present a less severe disease stage and show the highest potential for improvements, making them the most suitable candidates for treatment.

Cell-cell interaction in the pathogenesis of inherited retinal diseases

The retina is part of the central nervous system specialized for vision. Inherited retinal diseases (IRD) are a group of clinically and genetically heterogenous disorders that lead to progressive vision impairment or blindness. Although each disorder is rare, IRD accumulatively cause blindness in up to 5.5 million individuals worldwide. Currently, the pathophysiological mechanisms of IRD are not fully understood and there are limited treatment options available. Most IRD are caused by degeneration of light-sensitive photoreceptors. Genetic mutations that abrogate the structure and/or function of photoreceptors lead to visual impairment followed by blindness caused by loss of photoreceptors. In healthy retina, photoreceptors structurally and functionally interact with retinal pigment epithelium (RPE) and Müller glia (MG) to maintain retinal homeostasis. Multiple IRD with photoreceptor degeneration as a major phenotype are caused by mutations of RPE- and/or MG-associated genes. Recent studies also reveal compromised MG and RPE caused by mutations in ubiquitously expressed ciliary genes. Therefore, photoreceptor degeneration could be a direct consequence of gene mutations and/or could be secondary to the dysfunction of their interaction partners in the retina. This review summarizes the mechanisms of photoreceptor-RPE/MG interaction in supporting retinal functions and discusses how the disruption of these processes could lead to photoreceptor degeneration, with an aim to provide a unique perspective of IRD pathogenesis and treatment paradigm. We will first describe the biology of retina and IRD and then discuss the interaction between photoreceptors and MG/RPE as well as their implications in disease pathogenesis. Finally, we will summarize the recent advances in IRD therapeutics targeting MG and/or RPE.