Immunohistochemical localization of MYOC/TIGR protein in the trabecular tissue of normal and glaucomatous eyes

Purpose. To examine immunohistochemically the localization of myocilin/trab ecular meshwork inducible glucocorticoid response (MYOC/TIGR) protein in th e glaucomatous and normal trabecular meshworks. Methods. Trabecular tissues were used from one eye with late-onset goniodys genetic glaucoma, three with primary open angle glaucoma (one of which had the MYOC/TIGR gene mutation), two with exfoliation glaucoma and one without glaucoma. For light microscopic immunohistochemistry, frozen sections were stained by the avidin-biotin complex method using anti-MYOC/TIGR polyclona l antibody. For electron microscopic immunohistochemistry, the pre-embeddin g method using the same antibody was performed. Double immunostaining using both anti-MYOC/TIGR and anti-type VI collagen antibodies was done by the i mmunofluorescence method. Results. With light microscopy, immunoreactivity was seen in the whole trab ecular meshwork of each of the specimens. No notable differences were detec ted in staining among the types of glaucoma, or between the eyes with and t hose without the gene mutation. Under electron microscopy, immunoreaction p roducts were observed not only in the cytoplasm of the trabecular cells but also in the extracellular matrix, where staining was associated with the l ong-spacing collagen, fine granular materials and possibly microfibrils. Wi th double immunohistochemistry, MYOC/TIGR was colocalized with type VI coll agen in the trabecular meshwork. Conclusions. In glaucomatous and normal trabecular meshworks, the MYOC/TIGR protein is distributed in the extracellular matrix colocalizing with type VI collagen.