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Yongsook Goo, Kun No Ahn, Joo Yeon Kim, ; Comparison of Basal Firing Patterns of rd1 mice Retinal Ganglion Cell (RGC) Spikes in Freshly-isolated and Retinal Explants. Invest. Ophthalmol. Vis. Sci. 2014;55(13):356.
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Retinal prosthesis is being developed for patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD), and this is regarded as the most feasible method to restore vision. Extracting long-term safety margin for electrical stimulation for the prosthesis is one of the most important elements for the development of a viable retinal prosthesis. Here, we established a retinal explant culture method for our safe long-term electrical stimulation studies. We compared the firing pattern of retinal ganglion cell (RGC) spikes during 0 to 4 days in culture with those from freshly-isolated retinae. No electrical stimulation was applied to both tissues in order to explore basal firing patterns.
The well-known animal model for RP, rd1 (Pde6brd1) mice at postnatal 8 weeks were used (n=15). After isolation of retinae, retinal explants (n=15) were cultured in serum-free media (2% B27/ 1% N2) at 34 °C and 5% CO2 for up to 4 days. Each day, retinal waveforms were recorded with 8 × 8 MEA. Each day, we compared raster plot, mean frequency, inter-spike interval histogram (ISIH), power spectral density (PSD), and cross-correlation function of RGC spikes between explants and freshly-isolated tissues.
In freshly-isolated retinae, RGC spikes as well as ~10 Hz spontaneous oscillatory rhythm were observed while in explants, no spontaneous oscillatory rhythm was found. In explants, the mean frequency of RGC spikes were hypoactive compared with freshly-isolated retinae (ANOVA, p<0.05). There is no significant frequency change amongst the explants at days 1 to 4. Furthermore, no 2nd peak in ISIH and PSD were found in the explants. When the number of cross-correlated RGCs was counted at each day, the size of cross-correlated cell cluster becomes smaller with day.
We successfully established retinal explant tissue culture system. This may serve as a good model for future electrical stimulation studies regarding long-term safety margins.
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