Ultrastructural Changes in the Optic Nerve of Rabbits Induced by a Cholesterol Enriched Diet

Abstract

Purpose: : To study ultrastructural changes in the optic nerve and macroglial cells of hypercholesterolemic rabbits.

Methods: : New Zealand rabbits were divided into two groups: Control (G1; n=10), fed a standard diet for 8 months; Hypercholesterolemic (G2, n=10), fed a 0.5% cholesterol-enriched diet for 8 months. Eyes were processed for transmission electron microscopy.

Results: : In comparison with controls, the nerve fibre layer of the retina in G2 had very few axons and the basal membranes of the capillaries were thicker. In the optic nerve (ON), the vessels contained lipids and electrodense particles; their basal membrane was thicker and there was abundant collagen in the adventitia. In some instances we observed necrosis of the endothelial and muscles cells. The astrocytes were reactive, containing electrodense particles or else phagocyted apoptotic bodies or myelin debris. Some of them had degenerated due to necrosis rather than apoptosis. There was abundant loss of nerve fibres (NF), consistent with the loss of retinal ganglion cells; those remaining contained cellular debris and were oedematous. The oligodendrocytes were in several phases of necrosis.

Conclusions: : Hypercholesterolemia induces intense ultrastructural changes in the ON that could favour a situation of chronic ischemia.

Keywords: optic nerve • ischemia • microscopy: electron microscopy