Gene therapies studied as potential treatment for retinal diseases

Reviewed by Elif Ozgecan Sahin.

Retinal degenerative diseases are a major cause of visual impairment and blindness in humans. The retinal degenerative processes that result from genetic mutations generally affect the retinal pigment epithelium (RPE) and retina. The development of a new animal model for gene therapy may make studying these genetic mutations easier.

With the development of hypoxia, the photoreceptors progressively apoptose, and metabolic changes in the retina develop. Microglial cells that are activated by the dead photoreceptors can alter their location in the retinal tissue, resulting in further photoreceptor degeneration due to the release of proinflammatory cytokines.

Elif Ozgecan Sahin, MS, under the supervision of Salih Sanlioglu, VMD, PhD, from the Department of Gene and Cell Therapy at Akdeniz University in Antalya, Turkey, explained during a presentation at the American Society of Gene & Cell Therapy 2021 Virtual Annual Meeting that because the type of mutation present controls the photoreceptor degeneration, the pathologies seen in the hereditary retinal dystrophies are similar.

Realization of this similarity sparked the need for development of a new animal model of retinal degeneration that exhibits the pathologies seen in all the inherited retinal dystrophies, she said.

The investigators then set out to create an in vitro retinal degeneration model by treating ARPE-19 cells with cobalt chloride (CoCl2), an agent that triggers hypoxia. Western blot analysis confirmed the hypoxia and degeneration using antibodies against HIF1A. The next step then was generation of hypoxia in vivo by injecting CoCl2 intravitreally into Wistar rats.

Sahin pointed out that evaluation of their efforts via hematoxylin and eosin staining and TUNEL assay results “indicated that progressive retinal degeneration initiated in the outer segment of the photoreceptors and then further extended into the other retinal layers over time.” Changes began to be observed in the first 48 hours following the CoCl2 injection.

She also reported that the CoCl2 activated microglia cells that were visualized by CD68 immune staining; the cells were scattered throughout the retinal layers.

“All these results indicate that this chemical agent–induced animal model can be used successfully for gene therapy studies targeting retinal degeneration,” she concluded.

Elif Ozgecan Sahin, MS

E: elifozgecansahin@gmail.com

This article is adapted from Sahin’s presentation at the American Society of Gene & Cell Therapy 2021 Virtual Annual Meeting. She has no financial interest in this subject matter.

Salih Sanlioglu VMD, PhD

E: ssanlioglu@icloud.com

Sanlioglu has no financial interest in this subject matter.

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