Red light treatment in an axotomy model of neurodegeneration

Red light has been shown to provide neuroprotective effects. Axotomizing the optic nerve initiates retinal ganglion cell (RGC) degeneration, and an early marker of this is dendritic pruning. We hypothesized that 670nm light can delay axotomy-induced dendritic pruning in the retinal explant. To test this hypothesis, we monitored the effects of 670nm light (radiant exposure of 31.7Jcm(-2)), on RGC dendritic pruning in retinal explants from C57BL/6J mice, at 40min, 8h and 16h post axotomy. For sham-treated retinae, area under the Sholl curve, peak of the Sholl curve and dendritic length at 8h post axotomy showed statistically significant reductions by 42.3% (P=0.008), 29.8% (P=0.007) and 38.4% (P=0.038), respectively, which were further reduced after 16h by 40.56% (P<0.008), 33.9% (P<0.007), 45.43% (P<0.006), respectively. Dendritic field area was also significantly reduced after 16h, by 44.23% (P<0.019). Such statistically significant reductions were not seen in light-treated RGCs at 8 or 16h post axotomy. The results demonstrate the ability of 670nm light to partially prevent exvivo dendropathy in the mouse retina, suggesting that it is worthexploring as a treatment option for dendropathy-associatedneurodegenerative diseases, including glaucoma and Alzheimer's disease.