Enhanced tenascin expression associated with reactive astrocytes in human optic nerve heads with primary open angle glaucoma

Tenascin is a large extracellular matrix glycoprotein expressed in neural a nd non-neural tissues. In the central nervous system, tenascin is synthesiz ed by astrocytes during development and wound healing, forming barriers and affecting neurite outgrowth. In this study we examined tenascin expression in optic nerve heads of normal and glaucomatous eyes and found that there is upregulation of tenascin mRNA and protein in reactive astrocytes from hu man glaucomatous optic nerve heads compared to normal age-matched controls. In the prelaminar region there was a band of tenascin immunoreactivity aro und the blood vessels of glaucomatous, but not in normal eyes. However, ten ascin mRNA was only localized to astrocytes, suggesting that astrocytes are the cellular source of tenascin. In the lamina cribrosa, tenascin immunore activity and gene expression were localized to astrocytes in the cribriform plates and inside the nerve bundles. In the post-lamina region, tenascin i mmunoreactivity and gene expression were localized to astrocytes lining the pial septum immediately adjacent to the lamina cribrosa. In normal optic n erve heads, tenascin expression at the mRNA and protein levels was confined to clusters of astrocytes at the level of Bruch's membrane in the prelamin ar optic nerve head. In glaucoma, enhanced expression of tenascin may be pr otective to the axons of the retinal ganglion cells by providing a barrier for humoral and/or blood-borne factors that may cause further neural damage . However, the precise role of tenascin in glaucomatous optic neuropathy is not yet elucidated. (C) 1999 Academic Press.