Expression of insulin-like growth factor 1 receptor in rat retina following optic nerve injury

Purpose: 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. Methods: Healthy Wistar rats (N=70) were divided into two groups: a normal control group and an optic nerve injury group. Immunohistochemistry and flow cytometry were performed to detect the expression of IGF-1R and to measure the apoptosis of RGCs, respectively. Results: Immunohistochemistry revealed that at 1hr after optic nerve injury, IGF-1R immunoreactivity began to increase and reached a maximal level at 24hr (p<0.05), where it remained elevated up to 14days after injury. RGC apoptosis in the normal control group was 0.53%, while 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 1hr, 4.4% at 6hr, 5.2% at 12hr and reached a maximal level (8.5%) at 24hr. Subsequently, the rate declined to 1.9% 7days after injury and 0.9% 2weeks after injury. Conclusion: The IGF-1R immunereactivity in the retina increased after optic nerve injury. IGF-1R may regulate the apoptosis and regeneration of RGCs at different stages after optic nerve injury.