Immunohistochemical monitoring of the effect of a synthetic fibronectin-like peptide (Arg-Gly-Asp) on the age-related changes in the isolated human corneoscleral tissue of glaucomatous eyes.

Fibronectin, an adhesion glycoprotein has been detected and localized in samples of the trabecular meshwork from eight normotensive and 30 glaucomatous human eyes of various ages by means of the indirect immunoperoxidase staining technique. Fibronectin concentration in the trabecular meshwork tissue was evaluated by morphometric analysis. Deposits of the adhesion glycoprotein fibronectin were shown to be spread in the ocular drainage outflow system from patients along with progressive primary open-angle glaucoma (POAG). The fibronectin level quantitatively evaluated in serial cross-sections of trabecular meshwork, appeared to be increased during ageing and more rapidly in the event of POAG development. The active amino acid sequence in fibronectin is an arginine-glycine-aspartic acid tripeptide (Arg-Gly-Asp) and it was shown that the synthetic Arg-Gly-Asp peptide specifically inhibited the adhesive function of fibronectin in trabecular meshwork samples when incubated for 30 min at a concentration of 1-2 mg/ml. The peptide concentration necessary for a 50% decrease of the maximal fibronectin level in the trabecular meshwork specimen derived from patients with moderately advanced POAG stage, was about 1 mg/ml. Immunohistochemical staining exhibited a fainter fibronectin staining in trabecular tissues including the external trabecular layers and subendothelial region of Schlemm's canal, in samples incubated with the synthetic peptide compared with the same tissue explants before peptide treatment. It may be concluded that the adhesion control system is likely to play an important role in development and maintenance of tissue architecture and specialization of the normal human trabecular meshwork.