Cross Linked Actin Networks (CLANs) in the Cells of the Bovine Optic Nerve Head

Abstract

Purpose:: To demonstrate the presence of cross linked actin networks (CLANs) in dexamethasone treated bovine optic nerve head cells in vivo.

Methods:: Bovine optic nerve head cells were grown using standard cell culture techniques. They were then divided into a sample group and control group. The sample groups of cells were subsequently treated with DMEM medium containing 0.1mM of dexamethasone for the duration of 3, 7, 10 and 14 days while the control cells were correspondingly treated with plain DMEM medium. Both the sample and control group cells were fixed with 10% formalin and then stained using Alexa Fluor 488 Phalloidin and Propidium Iodide. They were then imaged using confocal scanning laser microscopy. The images were analysed using the Confocal Assistant program and Aequitas IA imaging software. These bovine cells were also characterised using the glial fibrillary acid protein (GFAP) staining to determine their cell type.

Results:: Cross linked actin networks (CLANs) have been demonstrated in steroid treated optic nerve head cells in culture. An increased incidence of CLAN formation and complexity were noted directly proportional to the duration of steroid treatment. At day 14, the controls showed very minimal CLAN formation (4.79 % + 3.20 %) compared to the dexamethasone treated cells (69.68 % + 20.88 %). The characterisation of these bovine optic nerve head cells with glial fibrillary acid protein (GFAP) staining revealed them to be GFAP positive cells.Discussion: Cross linked actin networks (CLANs) have earlier been described in steroid treated bovine trabecular meshwork and have recently been demonstrated in the human trabecular meshwork as well. They have not been described before in the cells of the optic nerve head. These structure are mostly situated in the nuclear area and seem to aggregate within the cell to form a geodesic structure with minimal contractile activity. Further studies aim to reveal the exact role of these CLANs in the pathogenesis of steroid induced glaucoma as to whether they are a cause or effect of glaucoma.

Keywords: optic nerve • cytoskeleton