The deterioration of vision associated with glaucoma is due to loss of nerve cell axons initially in the lamina cribrosa. This tissue has been considered an area of the sclera through which the optic nerve exits the globe and the glaucomatous changes in this region have been discussed in terms of altered blood flow or mechanical stresses that damage the nerves at elevated intraocular pressure (IOP). The objective of this research is to study the lamina cribrosa as a specialized connective tissue whose function is to maintain the exit pathway for the optic nerve leaving the eye. This research will aim to demonstrate the components of the extracellular matrix (ECM) of the lamina cribrosa, to show how these components differ from sclera and to test the hypothesis that, under conditions of elevated IOP, synthesis of one or more of the ECM components changes. This work will open an entirely new area of research and may eventually lead to new pharmacological therapy. The research uses material from laboratory and farm animals and enucleated human eyes and emphasizes three approaches: (1) immunohistochemical localization of ECM components (e.g. collagens, proteoglycans, etc.) using specific antibodies and indirect immunofluorescence techniques on fresh tissue; (2) autoradiographic demonstration of collagens and proteoglycans by incubation of fresh tissue with appropriate radiolabels; and (3) tissue culture of fibroblasts and astrocytes from the lamina cribrosa to study their growth patterns, morphology, and biosynthesis of collagens and proteoglycans. Fibroblasts from sclera and trabecular meshwork will also be cultured and compared to those grown from lamina cribrosa. Collagens and proteoglycans will be characterized by differential extraction, chromatographic and electrophoretic techniques, and specific enzyme digestion. To test the specific hypothesis concerning changes in the ECM associated with elevated IOP, these experiments will also compare, in parallel tissue from monkey eyes that have laser-induced glaucoma with the contralateral, control fibroblasts and astrocytes in culture. The influences of various agents on the in vivo and in vitro synthesis of collagens and proteoglycans by the cells of the lamina cribrosa will be determined, including steroidal and non-steroidal anti-inflammatory drugs, growth factors, transmitters, cofactors and inflammatory mediators.
