Abstract
Purpose: A critical part in developing optogenetic and electrical vision restoration therapies is the ability to assess the restored function over long periods of time. Here we describe the application of an in vivo method to record and track the response of retinal neurons in a study of optogenetic vision restoration in a mouse model of photoreceptor degeneration (rd10).
Methods: We expressed the calcium indicator GCaMP6s and/or a red-shifted channelrhodopsin (ChrimsonR-tdTomato) in inner retina neurons using adeno-associated viral vectors. In vivo functional imaging of GCaMP6s was performed using a custom built adaptive optics scanning light ophthalmoscope to measure cell responses to light stimulation. Uniform field 0.2 Hz square wave stimuli were presented in Maxwellian view using two LEDs: 365 nm to drive S-opsin, and 620 nm to drive ChrimsonR. Responses were also recorded in wild-type (C57BL/6J) mice transfected with only GCaMP6s.
Results: Robust co-expression of GCaMP6s and ChrimsonR-tdTomato was observed in many neurons and persisted in mice as old as 210 days, 145 days after injection. In rd10 mice with ChrimsonR, cells showed robust responses to 620 nm stimulation at all ages tested; 70, 84 and 112 days old. In rd10 mice without ChrimsonR, no cells showed light evoked activity to 620 nm or 365 nm stimulation. In wild-type mice without ChrimsonR, many cells showed light evoked activity to 365 nm but none responded to 620 nm stimulation.
Conclusion: Expression and function of the channelrhodopsin ChrimsonR persists for extended periods of time, demonstrating excellent potential as a viable therapy for vision restoration in humans. In vivo imaging of calcium responses can be used to monitor responses of retinal neurons over time and may be a useful method for evaluating vision restoration methods.
Meeting abstract presented at the 2016 OSA Fall Vision Meeting