Immunogold localization of collagen type VI, laminin and fibrillin in glaucomatous trabecular meshwork

Purpose: To localize the collagen type VI, laminin et fibrillin in glaucomatous and non-glaucomatous trabecular meshworks. Material: Twenty-four trabeculectomy specimens from patients suffering of primary open angle glaucoma (POAG, 15 cases), pigmentary glaucoma (PG, 2 cases), pseudo-exfoliative glaucoma (PEG, 7 cases) and 2 non glaucomatous aged trabeculums of enucleated eyes. Methods: Post-embedding immunogold indirect labelings on 4% paraformaldehyde-0.1 % glutaraldehyde fixed and LRWhite embedded samples. Results: Labeling of type VI collagen was observed on the 64 nm collagen fibers in all samples, less intensively on POAG or PG disorganised microfibril areas, and especially on PEG pseudo-exfoliative material deposits. Laminin labeling was strongly positive on healthy basal membranes and less intense on POAG and PG abnormal basal membranes. Fibrillin labeling was found on POAG or PG disorganized microfibril areas, especially around pigment granules, around 64 nm striated collagen fibers and with a mild intensity on POAG and PG juxtacanalicular microgranular substance areas. No labeling was found on pseudo-exfoliative substance deposits. Conclusion: Collagen type VI abundance in pseudo-exfoliative substance deposits could result from a fibrillogenesis abnormality. POAG and PG basal membrane ultrastructural abnormalities and weak laminin content could share the same origin. The abundance of fibrillin in disorganized microfibrils could result from the chronic elevated tensile strength due to ocular hypertony.