Establishment of A new animal model for gene therapy studies of retinal degenerative diseases

Objective: Hereditary retinopathies are characterized by retinal degeneration caused by genetic mutations that disrupt the structure and function of photoreceptors. Although most of the causative genes are located in the rod cells, rod cell deaths lead to the degeneration of cone cells and thus loss of vision. As photoreceptor degeneration mechanism and process are mainly governed by the type of mutation, the pathologies observed in the hereditary retinal dystrophy are similar. Thus, we aimed to develop a new experimental animal model of retinal degeneration manifesting a disease pathology which is common to all hereditary retinal dystrophies. Methods and Results: A hypoxia mimicking agent, cobalt chloride, was used to induce retinal photoreceptor cell degeneration. To determine the potential toxicity of CoCl2 on RPE and microglial cell lines, MTT assays were carried out using different concentration of CoCl2. To confirm the induction of hypoxia, the expression of the HIF-1α was evaluated by western blotting and immunofluorescence staining following CoCl2 treatment. Intravitreal injections of CoCl2 were performed to establish an animal model of retinal degeneration in Wistar rats. Then hematoxylin and eosin staining was performed in paraffin embedded eye tissues to reveal retinal degeneration status of sacrificed animals. Progressive retinal degeneration was first spotted in the outer segment of the photoreceptors and then extended in to other retinal layers in time. Additionally, an extensive TUNEL positive apoptotic cell staining was observed in the outer nuclear layer within the first 48 hours following CoCl2 injections. Conclusion: A chemical agent-induced animal model of progressive retinal degeneration was successfully established by intravitreal administration of CoCl2 in Wistar rats. Key words: cobalt chloride, hypoxia, progressive retinal degeneration