Brighter Blindness Treatment Opportunities – ScienceDaily

The journal written by José Sahel, Jean Bennett and Botond Roska summarizes the recent therapeutic strategies for the treatment of blinding diseases, which are very encouraging.

Summary of Comments

Gene replacement strategies or gene editing could potentially reverse vision loss and lead to near normal visual outcomes. Early intervention at the onset of retinal degeneration, when photoreceptor cells (rods and cones) are still intact, is particularly promising. The first gene therapy approved for Leber's Conbad Amaurosis (LCA) with a confirmed biallelic mutation RPE65 has paved the way for more than 30 gene replacement trials worldwide under other conditions, for example . those in clinical phase III for choroidemia, achromatopsia and Leber's hereditary optic neuropathy.

Gene-independent strategies aim to prevent or slow the progressive degeneration of photoreceptor cells with neuroprotective agents for a broad spectrum of retinal dystrophies. Neuroprotective strategies, particularly those aimed at preserving cones, are the best approach to treat a disease characterized by continuous degeneration of photoreceptor cells.

Stem cell therapy, optogenetic therapy and retinal prostheses are used to restore vision in later stages of retinal degeneration. These approaches can be applied independently of the causal mutation and should restore a low degree of vision in blind patients. Stem cell therapies intended to replace degenerate cells to restore vision are being developed or evaluated clinically in a wide range of degenerative disorders of the retina, e.g. for the "non-neovascular" form (badociated with progressive loss of photoreceptors and RPE cells) of age-related macular degeneration (AMD), for the replacement of hereditary retinal dystrophies (IRD) and epithelium retinal pigment (RPE).

Brain-machine interface technologies using electrode networks or optogenetics can stimulate the visual pathway downstream of the retina. Electrical stimulation of the primary visual cortex is a possible scenario currently undergoing clinical trials.

Optogenetic therapy makes cells sensitive to light by the expression of an optogen encoding a light-activated channel or pump in the remaining internal retinal cells. It could be used to resensitize a degenerate retina into visible light, regardless of the mutation causing the loss of photoreceptor cells.

Retinal prostheses can re-activate the remaining retinal circuits in bipolar or ganglion cells after the loss of photoreceptor cells. Epiretinal and subretinal implants are able to stimulate a degenerate, light-insensitive retina and restore partial vision in blind people.

Accelerated therapeutic developments in ophthalmology

Specific features make the eye particularly suitable for diagnostic and therapeutic exploration: easy access, small volumes, high internal compartmentalization and stable cell populations. Optical transparency of the eye allows direct visualization with high resolution imaging and accurate badessment of disease stage and response to treatment. The relative immune privilege of the eye, particularly the subretinal space, reduces adverse reactions to injected vectors and gene products. However, advances in ophthalmology are intrinsically linked to a better understanding of the morphology and function of the visual system.

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