Purpose: To identify and characterize astrocyte responses and reactivation in human optic nerve heads from patients with primary open-angle glaucoma.
Methods: Fifteen optic nerve heads with primary open-angle glaucoma and 13 normal controls were fixed in 4% paraformaldehyde, paraffin embedded, and stained for immunofluorescence and immunoperoxidase. The antibodies used were against glial fibrillary acidic protein (GFAP) and against neural cell adhesion molecule (N-CAM).
Results: Two subpopulations of type 1 astrocytes exist in the normal optic nerve. Type 1A astrocytes express only glial fibrillary acidic protein and type 1B express both glial fibrillary acidic protein and neural cell adhesion molecule. These are the major cell subpopulations in the lamina cribrosa and prelaminar regions. In primary open angle glaucoma, type 1B astrocytes in the prelaminar region showed increased immunoreactivity for glial fibrillary acidic protein and neural cell adhesion molecule, and cytoplasmic enlargement with thicker and longer cytoplasmic processes. At the level of the lamina cribrosa, type 1B astrocytes appeared round and the cell bodies were no longer in the cribriform plates but located in the nerve bundles. Type 1A astrocytes were not observed in the glaucomatous optic nerve head.
Conclusions: Astrocyte responses in primary open angle glaucoma may underlie cellular changes that lead to axonal damage and optic nerve head remodeling. These responses may have pathogenic significance for glaucomatous optic neuropathy.