Purchase this article with an account.
Steven Stasheff, Frederick Blodi, Malini Shankar, Jeannette Bennicelli, Jean Bennett, Sajag Bhattarai, Arlene Drack, Stewart Thompson; Rpe65 gene therapy restores precise visual responses in vitro to many retinal ganglion cells in Rpe65-/- mice. Invest. Ophthalmol. Vis. Sci. 2013;54(15):720.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To help further improve Rpe65 gene therapy for Leber's congenital amaurosis (LCA), we sought to better understand its effectiveness at the resolution of single cells and retinal circuits. Here we report substantial improvements in retinal ganglion cell (RGC) responsiveness to light in vitro, but also persistent background hyperactivity and other abnormalities in visual signaling. Further understanding of mechanisms underlying these abnormalities may help explain the better response of children than adults and modest improvements of other visual function seen in early clinical trials.
We used in vitro multielectrode recordings to measure RGC activity in rd12 (Rpe65-/-) mouse retinas after subretinal injection with a viral vector to infect retinal pigment epithelium (RPE) cells with normal RPE65 (AAV2/1-hRPE65). We compared in vitro spontaneous and light-evoked activity in both treated and untreated eyes at several time points between 7-90 days following injection. Light stimuli were full field flashes of graded intensities, or pseudorandom checkerboard sequences to map receptive fields.
Ganglion cell responses to full field flashes were robust in treated eyes, including multiple recognizable response types (e.g., ON/OFF, brisk/sluggish, transient/sustained) and reliable receptive field maps in many cells. However, others had weak or imprecise responses. Retinotopic regions receiving gene therapy corresponded to regions with light responsiveness. No light-evoked responses were detected in any untreated eyes. Spontaneous hyperactivity persisted after gene therapy at a level similar to that in untreated eyes.
In vitro multielectrode recording provides a powerful system for evaluating the effectiveness of gene therapy at high resolution not possible in human patients. It can provide more detailed understanding of mechanisms that underlie imperfect responsiveness to gene therapy, and guide further improvements in treatment. The results of our current study suggest that spontaneous hyperactivity corrupts the neural code of RGCs, decreasing the precision of some RGC responses. This is expected to degrade the quality of vision and lead to disruption in downstream visual pathways in the brain. We are now investigating whether earlier treatment may prevent RGC hyperactivity.
This PDF is available to Subscribers Only