Study On The Mechanisms Of Lens Injury Promoting The Survival Of RGCs After Optic Nerve Injury In Rats

Traumatic optic neuropathy (TON), as a severe complication of brain, orbit and prosopo injury, always results in primary or secondary loss of vision. For a long time, there have been lots of arguments about the treatments of TON. Theoretically, making the injuried optic nerve regenerate completely is the only way to solve this problem in the end. Evidently, there is close relationship between the numbers of survival Retina ganglion cells (RGCs) and the regeneration of optic nerve axonal. So how to protect optic nerve, especially the survival of RGCs and the regeneration of axons after optic nerve injury, has become a focus all over the world.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 injuried optic nerve. It has been reported that Murine Miiller cells conditioned medium (MMG) can promote the survival of RGCs and the regeneration of axons, but there is rarely report about the expression chang of Muller cells on cataratogenic lens injury prompting the survival of RGCs in Wistar rats. ObjectiveOur research is to study the expression chang and the mechanisms of Muller cells on cataratogenic lens injury prompting the survival of RGCs after optic nerve injury in Wistar rats.MethodFourty healthy adult Wistar rats are divided into 3 groups at random:normal control group (8 rats), simple optic nerve axotomy group (16 rats) and joint injury group (16 rats). Without making any deal with the normal group; the optic nerves are completely cut at 3mm behind the eyeball in simple optic nerve axotomy group, lens receives intraocular penetration beside optic nerve axotomy in joint injury group. Normal control group rats are sacrificed after 7 days of feeding; 7,14 days after operation 8 rats are killed respectively in other 2 groups. The morphological changes of retina and retinal ganglion cells are observed by HE staining. Muller cells are labeled in retina with glial fibrillary acidic protein by immunohistochemistry, count the number of RGCs and GFAP positive Muller cells with microscope.Results1. Every level of the normal rat retina is clear, nerve fiber layer arranges regularly, there is no inflammatory cell in ganglion cell layer, the number of RGCs is 52.98±1.90.7 days after surgery, the number of survival RGCs in simple optic nerve axotomy group is 36.61±1.69, the loss rate of RGCs is 30.90%; the number of survival RGCs in joint injury group is 50.76±2.77, the loss rate of RGCs is 4.19%; when pairwise comparison, there are no significant difference statistically (P=0.000) except normal group compared with joint injury group (P=0.053).14 days after surgery, the number of survival RGCs in simple optic nerve axotomy group is 22.67±1.94, the loss rate of RGCs is 57.22%; the number of survival RGCs in joint injury group is 35.69±1.80, the loss rate of RGCs is 32.62%; there are significant difference statistically (P=0.000) when pairwise comparison.2. In normal rat retina, the inner core layer where Muller cell body lie is not dyeing. There is light brown deying in nerve fiber layer, the membrane of RGCs is not deying. Inner plexiform layer shows small amount of light brown color vertically.7 days after surgery, there are positive cells in the inner nuclear layer of simple injury group rats. the number of positive cells is 29.38±2.04, light brown, with hypertrophy of cell body and axon. Nerve fiber layer and membrane of RGCs also show light brown. There are also visible GFAP positive staining in inner plexiform layer, outer plexiform layer, outer nuclear layer and pigmented cell layer. The number of positive cells in joint injury group is 48.96±2.80 at this time, the colour is dark brown, with hypertrophy of cell body and axon. There is significant difference statistically between the two groups (P=0.000) at this time point.14 days after surgery, the number of positive cells in simple injury group is 19.07±2.14, without hypertrophy of positive cell body and axon. Compared with the same group, the number of positive cells decreased, the difference is statistically significant (P=0.000).14 days after surgery, the number of positive cells in joint injury group is 46.73±1.50, with hypertrophy of positive cell body and axon. compared with the same group, there is no significant difference statistically (P=0.067). There is also significant difference statistically between the two groups (P=0.000) at this time point.Conclusion1. As time goes by, RGCs loss progressively after optic nerve axotomy.2. Lens injury which leads to cataract could severely promote the survival of retina ganglial cells after optic nerve injury, and this protective effect is stronger in the early time after injury.3. Lens injury could significantly promote the activation of Muller cells, and the activation state is stable.