Axonal regeneration after optic nerve crush in Nogo-A/B/C knockout mice

PURPOSE The axonal regeneration of retinal ganglion cells (RGCs) after optic nerve (ON) crush was investigated both in vivo and in vitro on Nogo-A/B/C knockout mice. METHODS The study used 20 Nogo-A/B/C knockout mice in the experimental group, and 20 C57BL/6 mice in the control group. Partial ON injury was induced by using a specially designed ON clip to pinch the ON 1 mm behind the mouse eyeball with 40 g pressure for 9 s. The left ON was injured in both groups, but the right ON was left untouched in the control group. Nogo-A/B/C mRNA was studied by in situ hybridization in both groups. GAP-43 was studied by immunofluorescence staining on frozen sections. RGCs were purified and cultured in DMEM medium containing B-27. Cells were then immunostained with both Thy1.1 and GAP-43 antibodies. The axonal growth of RGCs was calculated by a computerized image analyzer. RESULTS GAP-43 expression was significantly higher in the experimental group than in the control group (p<0.01). GAP-43 antibody binding was demonstrated in the axons of cultured RGCs. Axonal growth was significantly more active at every observed time point in the experimental group than in the control group (F=43.25, 32.16; p<0.01). CONCLUSIONS Nogo genes play an inhibitive role in the axonal regeneration after ON injury, while Nogo-knockout is an effective way to eliminate this inhibition and accelerate axonal regeneration.