Matrix metalloproteinase-1 localization in the normal human uveoscleral outflow pathway

PURPOSE. TO determine the distribution of matrix metalloproteinase-1 (MMP-1 ) in the uveoscleral outflow pathway and other anterior segment tissues of normal human eyes. METHODS. Normal human eyes were fir;ed in methacarn and sectioned and immun ostained using a specific polyclonal antibody to MMP-1. Immunoreactivity wa s visualized using diaminobenzidine. To compare the staining intensity in v arious tissues, the mean optical density within the ciliary body, mid-iris stroma, iris root, uveal trabecular meshwork, cornea, and sclera was determ ined using imaging densitometry. To determine the cellular distribution of MMP-1 in ciliary muscle, additional sections were double-immunostained usin g antibodies to MMP-1 and calponin. These sections were examined by confoca l laser scanning microscopy. Specificity of the antibody to MMP-1 in ocular tissues was confirmed by western blot analysis with uveal tract homogenate s. RESULTS. Moderate-to-strong MMP-1 immunoreactivity was observed in ciliary muscle, iris, sclera, corneal endothelium, and ciliary nonpigmented epithel ium. Lighter immunoreactivity was observed in corneal epithelium, brood ves sels, trabecular meshwork, Schlemm's canal, and associated collector channe ls. Confocal microscopy showed that ciliary muscle MMP-1 was primarily insi de ciliary muscle cells. Densitometry showed that net optical density was a pproximately fivefold greater in ciliary muscle, iris root, and sclera than in trabecular meshwork. CONCLUSIONS. MMP-1 a-as prominently identified in regions of the anterior s egment of normal human eyes associated with the uveoscleral outflow pathway and in the iris, corneal endothelium, and ciliary nonpigmented epithelium. These data support the hypothesis that MMP-1 activity is involved in regul ating uveoscleral outflow facility.