Effects of the extract from wolfberry on the survival of retinal ganglion cells after optic nerve transection

Abstract

Lycium barbarum (Wolfberry) is an anti-aging herbal medicine in China and has been proved to be neuroprotective in our previous studies. In addition, it can preserve the vision in different experimental eye disease models. In order to further investigate the mode of neuroprotective effects of wolfberry on retinal ganglion cells (RGCs), we employed two different optic nerve transection ways to investigate its effects on nerve injury. One model was complete optic nerve transection (CONT) in which RGCs mainly died from the primary insult; another model was partial optic nerve transection (PONT) in which secondary degeneration accounted for the death of RGCs whose axons were intact. Wolfberry was orally fed to the rats seven days prior to the experiments. Our results showed that wolfberry did not significantly preserve the survival of RGCs in both 1 and 2 weeks after CONT. However, it exhibited beneficial effects on RGCs in PONT. RGCs in the inferior part of retinas 4 weeks after cutting the dorsal one-third of the optic nerves had higher survival rate if rats were fed with wolfberry. We also aimed to examine the topography of partial optic nerve transection by using a fluorescent probe DiI. It was placed into the partial cut sites immediately after the surgery. The results indicated that the majority of RGCs labeled with DiI were in the superior part of retina, suggesting that secondary degeneration was the leading cause of RGC loss in the inferior part of retina. Taken together, wolfberry protected RGCs when the neurons were undergoing secondary degeneration rather than those undergoing primary injury.