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CHIN I LIN, Chuan-Chin Chiao; Blue light promotes neurite outgrowth of retinal explants in postnatal ChR2 mice. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5500. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Axons of retinal ganglion cells (RGCs) in mature mammals fail to regenerate after injury. Our previous study has shown that short-term modulation of developmental neural activity by electrical stimulation could promote neurite outgrowth of retinal explants in postnatal mice. However, electrical stimulation is non-specific and could activate the entire retina, thus the origin of neural activity on enhancing neurite outgrowth is unknown. In the present study, by using the mice with channelrhodopsin-2 (ChR2) expressed exclusively in RGCs, the optogenetic approach was applied to specifically activate RGCs and examine its effect on promoting neurite outgrowth.
Retinal explants from ChR2 mice were stimulated with different frequencies of blue light LED for one hour to activate RGCs and then cultured for 5 days. The extent of neurite outgrowth was quantified and compared to determine the effect of RGC activation on axon regeneration. Multi-electrode array (MEA) was also used to examine the neural activity patterns of retinal explants upon blue light stimulation.
The results showed that different blue light stimulations, especially 20 Hz, greatly enhanced the neurite outgrowth of P5 and P11 retinal explants from ChR2 mice. The MEA recording confirmed that the blue light could evoke neural responses of RGCs reliably in these ChR2 mice. In addition to the responses of channelrhodopsin activation in RGCs by blue light, the light responses of intrinsic photosensitive RGCs (ipRGCs) were also recorded in these developing retinas. In a separate experiment, it was found that activating ipRGCs alone in the wild type P5 C57BL/6 mice could also enhance neurite outgrowth.
These findings demonstrate that activating RGCs directly is sufficient to promote neurite outgrowth of retinal explants. Moreover, the ipRGCs may play an important role in enhancing axon growth during postnatal development.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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