Abstract
Purpose: :
Axons of retinal ganglion cells are damaged in glaucoma. Cytoskeletal components of axons are expected to change in the disease. This study classified subtypes of ganglion cell axons by their relative content of cytoskeletal components, F-actin, microtubules (MTs) and neurofilaments (NFs) and determined changes of each subtype in the context of glaucoma.
Methods: :
A rat model of glaucoma with laser photocoagulation of trabecular meshwork was used. Whole-mounted retinas were simultaneously stained with fluorescence to label F-actin, MTs and NFs. Strands of these components, running along the axons, were identified by confocal imaging of the tissues. To determine the relative content of cytoskeletal components, lines across cytoskeletal strands were defined within nerve fiber bundles. Intensity profiles along the lines were obtained for each cytoskeletal component. Axons were classified by relative intensities of these components. For instance, axons with intensely stained F-actin, MTs and NFs were classified as FMN subtype and axons with intensely stained MTs and NFs but lighter stain of F-actin were classified as MN subtype. A linear density of each subtype was calculated as the number of the subtype found along a line divided by the line length.
Conclusions: :
Normal axons of retinal ganglion cells contain different proportions of cytoskeletal components. Elevated IOP causes significant loss of FMN subtype at early stages of glaucoma. These results suggest that some subtypes of axons are more sensitive to elevated IOP than others.
Keywords: nerve fiber layer • cytoskeleton • microscopy: light/fluorescence/immunohistochemistry