Protective Effect Of IGF-1 Following Optic Nerve Injury In Rat

Objective: To investigate the apoptosis in retinal ganglion cells(RGCs) and insulin-like growth factor 1 receptor(IGF-1R) in the retina following optic nerve crush,and the protective effect by inject insulin-like growth factor 1(IGF-1) in vitreous chamber following optic nerve crush.Methods: Healthy Wistar rats(N = 180) were divided into 6 groups: each group has 30 rats, the right eye is the normal control, the left is the optic nerve injury group. Inject NS 15μg/ml to the half of the injury eye and IGF-1 to the left eyes in vitreous chamber at 1h; 6h; 12h; 24h; 1w; 2w six time points.Immunohistochemistry and flow cytometry were performed to detect the expression of IGF-1R and to measure the apoptosis of RGCs, F-VEP was performed to detect the level of the optic nerve after injury.Results: Immunohistochemistry revealed that at 1 hour after optic nerve injury, IGF-1R immunereactivity began to increase and reached a maximal level at 24 h(P< 0.05) where it remained elevated up to 7 days after injury.The apoptosis rate in the optic nerve injury group increased over time. The apoptosis rate in the optic nerve injury group was 1.4% at 1 h, 4.4% at 6 h, 5.2% at 12 h, and reached a maximal level(8.5%) at 24 h. Subsequently the rate declined to 1.9% 1 week after injury and 0.9% 2 weeks after injury. There is significant difference of apoptosis of RGCs between the normal groups and injury groups at the different time points, and significant difference between injecting NS and IGF-1 in vitreous chamber after injury at1h、6h、12h、 24h; no significant difference at 1w、 2w.Conclusion: The IGF-1R immunereactivity in the retina increased after optic nerve injury. IGF-1 may regulate the apoptosis and regeneration of RGCs at different stages after optic nerve injury. IGF-1 play essential role in repairing and protecting acute optic nerve injury.