Immunolocalization of MYOC Protein Within the Anterior Eye of Normal and Primary Open–Angle Glaucomatous Dogs

Abstract

Abstract: : Purpose: The presence of myocilin, MYCO, is being investigated in a colony of Beagles, a canine model for inherited spontaneous, hypertensive glaucoma. We have examined the localization the MYOC protein in the normal and glaucomatous canine eyes by immuno–histochemistry and –cytochemistry. Methods: Paraffin– and plastic–embedded specimens from the anterior uveas of 10 Beagles with inherited glaucoma (3–mos– to 13–yrs–old) and age–matched normal Beagles were sectioned and then were incubated with primary antibody, rabbit polyclonal anti–human MYOC IgG (Santa Cruz Biotechnology ) overnight at 4 degrees C. Specimens were incubated with secondary antibody either with biotinylated link followed by peroxidase–labeled streptavidin and then by substrate–chromogen for light microscopy or with18 nm colloidal gold labeled goat anti–rabbit IgG for TEM. Results: Within normal and moderately glaucomatous canine specimens, cell membranes of smooth muscle cells of the iris and ciliary body stained positively, as well as most resident stromal and vascular endothelial cells. The cytoplasm of cells within the nonpigmented ciliary epithelium of the ciliary body processes stained intensely being weaker along the pars plana. Trabecular meshwork cells were homogenously labeled as well as the sclera adjacent to the angular aqueous plexus. In specimens with advanced glaucoma, greater intensity of staining was observed within trabecular meshwork cells and adjacent sclera, and the nonpigmented epithelium of the ciliary processes. Fibrinous–like material labeled intensely within the posterior chamber. Conclusions: Immunolocalization of myocilin in the normal and glaucomatous canine eye was successfully observed for the first time. The findings with regard to the normal eye are nearly identical to that previously reported in humans. The findings in this study support the possibility that changes in the activity of MYOC within the aqueous humor outflow pathway of individuals with spontaneous glaucoma are associated with the rise of intraocular pressure and subsequent development of this disease.

Keywords: outflow: trabecular meshwork • ciliary body • immunohistochemistry