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.