Study On The Mechanisms Of Lens Injury Promoting The Regeneration After Injury Of Optic Nerve

Optic nerve injury is a common type of ocular injury in clinic, and always results in visual loss. It always happened with many type of facial, brain or orbit trauma, and pressing, drawing-of and cutting can result in a seriously injury of optic nerve, if can't receive timely treatment, visual acuity will lost irreversibly. After the injury of optic nerve, subsequent necrosis or apoptosis of retinal ganglion cells (RGCs) is the main reason of visual loss. So how to protect the injured optic nerve, especially the survival of RGCs and the regeneration of axons after optic nerve injury, has become a hot research topic all over the world.In mature Mammals, conventional wisdom thinks that axon can't regenerate after central nervous system injury, the injured neuron unable to form a new synaptic linkage. In 20th century, Hall found that transplanting with a section of the body sciatic nerve to the optic nerve damage area, successfully inducing the regeneration of injured optic nerve axon, the view of damaged central nervous system could not regenerate has changed. Recently Leon and Fischer found that lens injury of rats which result in traumatic cataract, can severely promote the survival of RGCs and the regeneration of injured optic nerve. But the mechanism is still poorly defined. So many researchers at home and abroad focus on the mechanism research that lens injury promoting the regeneration of injured optic nerve. Currently it has been reported that activated macrophages in injured peripheral nervous system can form a advantageous internal environment for the regeneration of peripheral nerve, through phagocytosis and synthesising and releasing many active factors. But there is rarely report about whether macrophage activation has such effect in central nervous system. And so far, we still don't know whether it played a key role in the mechanism of lens injury promoting the regeneration of injured optic nerve.ObjectiveOur research is to study the mechanisms of lens injury prompting the axonal regeneration of axotomized retinal ganglion cells after optic nerve injury in adult Wistar rats, and to explore the role of activated macrophages in this neuroprotection.MethodThere are 50 healthy adult Wistar rats, which are divided into 4 groups at random:normal control group (5 rats), without making any deal with the normal control group; simple optic nerve axotomy group (15 rats), by cutting the optic nerve at 2mm behind the eyeball (NC); joint lens injury group (15 rats), meanwhile lens receives intraocular penetration(NC+LP); joint injections of Zymosan (15 rats), meanwhile zymosan was injected intravitrously (NC+ZI).1,2,3 weeks after operation 5 rats are killed respectively in 3 operation groups. Macrophages are labeled in retina with anti-ED-1 antibody by immunohistochemistry. The regenerating RGCs were labeled with anti-GAP-43 antibody by immunofluorescence assays.ResultsIn normal control group and NC group, ED-1 positive cells weren't seen in retina. In NC+LP group and NC+ZI group, ED-1 positive cells were observed in retina.GAP-43 expression:In normal control group expression of GAP-43 main in inner plexiform layers of the retina, none in ganglion cell layer. In NC group, few GAP-43 staining in ganglion cell layer, and lost in the second week. In NC+LP group and NC+ZI group, showed an intense up regulation of GAP-43 in ganglion cell layer, the staining area is increased considerably in the first 2 weeks, and still staining in the third week.In NC group and normal control group there is significant difference statistically of positive staining area in retina among the 1st week(P<0.01), no significant difference statistically between the 2nd and 3rd week(P>0.05).In NC and NC+LP (or NC+ZI) groups there is significant difference statistically of positive staining area in retina at different time point (P<0.01). Expression of GAP-43 in retina may be the most in early time after injury, then decrease as time past.In NC+LP (or NC+ZI) group and normal control group there is significant difference statistically of positive staining area in retina at different time point (PO.01).In NC+LP group and NC+ZI group there is no significant difference statistically at the 1st week(P> 0.05), and difference statistically at the 2nd and 3rd week (P<0.05).In NC+ZI (or NC+ZI) group there is significant difference statistically of positive staining area in retina between different time point (P<0.01).Conclusion1. After the injury of optic nerve, few GAP-43 was observed in ganglion cell layers of the retina in early time.2. Lens injury and intravitreal zymosan can promote the activation of macrophages, and could significantly increase expression of GAP-43 after optic nerve injury, promote the regeneration of injured optic nerve, and this protective effect is stronger in the early time after injury, last for 3 weeks.