Restoring vision in mice with retinal degeneration using multicharacteristic opsin

Abstract

Retinal degenerative diseases, such as retinitis pigmentosa (RP) and dry age-related macular degeneration, have led to loss of vision in millions of individuals. Currently, no surgical or medical treatment is available, although optogenetic therapies are in clinical development. We demonstrate vision restoration using multicharacteristics opsin (MCO1) in animal models with degenerated retina. MCO1 is reliably delivered to specific retinal cells via intravitreal injection of adeno-associated virus (vMCO1), leading to significant improvement in visually guided behavior conducted using a radial arm water maze. The time to reach the platform and the number of error arms decreased significantly after delivery of MCO1. Notably, the improvement in visually guided behavior was observed even at light intensity levels orders of magnitude lower than that required for channelrhodopsin-2 opsin. Viability of vMCO1-treated retina is not compromised by chronic light exposure. Safe virus-mediated MCO1 delivery has potential for effective gene therapy of diverse retinal degenerations in patients.

Sensitization of ON-bipolar cells with ambient light activatable multi-characteristic opsin rescues vision in mice

“…Genetically and chemically engineered light-gated ionotropic glutamate receptor [21,22] or synthetic small molecule photo-switch [23], have been shown to photosensitize retinal ganglion cells (RGCs), leading to improved visually-guided behavior. Optogenetic sensitization [24][25][26][27][28][29] of retinal cells combined with activation/inhibition, has potential as an alternative to retinal implants. Expression of opsin allows for the flow of specific ions by light-induced trans-cis isomerization of all-trans-retinal, and thus, depolarizing/hyperpolarizing the opsin-expressing retinal cells when illuminated by the light of the characteristic wavelength of the opsin.…”

“…This has allowed the possibility of replacing the retinal implants and eliminating the need to increase the number of electrodes for higher resolution. By bypassing the dysfunctional photoreceptors and engineering light responsiveness in remaining healthy retinal cells, optogenetic treatment reestablishes the lost function of the retinal circuitry, leading to visual perception in blind subjects [24,30]. In addition to higher resolution (determined by sensitized retinal cells: RGCs, bipolar cells), optogenetic treatment has several advantages over electrical stimulation such as cellular specificity (e.g., residual cones, ganglion, or bipolar cells) and not requiring complex intraocular surgery [27,28,31].…”

“…Long-term active stimulation with high intensity light poses the risk of retinal damage and adds complexity to the treatment. To circumvent the limitation of current optogenetics technology, we have engineered an ambient light (<10 µW/mm 2 ) sensitive opsin (MCO1) having high temporal precision and a lower threshold required for optogenetic stimulation [24]. Here, we demonstrate the use of AAV2 packaged MCO1 (vMCO1), to selectively transfect the upstream-located second order retinal cells (ON-bipolar cells) that receive synaptic input from photoreceptor cells.…”

Nano-enhanced Optical Gene Delivery to Retinal Degenerated Mice

“…Recently, optogenetic therapies have been evaluated for vision restoration in mice models of retinal degeneration either by non-specific stimulation of retina 27 or in a cell-specific manner for retinal ganglion cells [28][29][30][31][32] and ON bipolar cells 33,34,35 . Further, use of chloridechannel opsin (NpHR) expressing in longer-persisting cone photoreceptor protein has shown promise for restoration of vision 36 .…”

“…Herein, we introduce the use of nano-enhancement of near-infrared optical field of continuous wave (CW) near-infrared (NIR) laser beam by surface plasmon resonance (SPR) near targeted retinal cells for gene delivery. To allow ambient-light based activation 35 , we utilized multi-characteristic-opsin (MCO) encoding plasmids to sensitize retinal cells in degenerated retina. It would be highly desirable to re-induce transgene expression by reinjection, and NOD provides this opportunity.…”