Optic nerve alterations in apolipoprotein E deficient mice

PURPOSE. To study the morphologic characteristics of the optic nerve (ON) by using an experimental model of knockout mice for expression of the ApoE gene METHODS. Eyeballs with the retrobulbar ON attached were obtained from 24-week-old mice. Using morphologic and morphometric techniques and light and transmission electron microscopy, the ON characteristics were determined in three groups of mice: 1) wild type mice as the controls (CG; n=15), 2) knockout mice for the ApoE gene (ApoE-G; n=15), and 3) knockout mice for the ApoE gene that were fed a cholesterol-supplemented diet (ApoED-G; n=15). RESULTS. The ON cross-sectional area was significantly higher in the ApoE-G than in the CG (p<0.001) mice, whereas no significant changes were noticed between the ApoE-G and ApoED-G mice. Significant differences were noticed between those groups regarding the myelination index. Higher density of intra-axonal degeneration and myelin sheath alterations were found in both ApoE groups in respect to the CG. CONCLUSIONS. These results suggest that ApoE knockout mice have changes in ON morphology and myelination.