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Abstract #18511 Published in IGR 3-3
Ultrastructural localization of collagen IV, fibronectin, and laminin in the trabecular meshwork of normal and glaucomatous eyes
Hann CR; Springett MJ; Wang X; Johnson DHOphthalmic Research 2001; 33: 314-324
PURPOSE: To determine whether differences in the ultrastructural characteristics or composition of the basement membranes of the trabecular lamellae and Schlemm's canal exist in normal eyes and eyes with primary open-angle glaucoma (POAG). Basement membranes play key roles in the attachment of the overlying trabecular cells and Schlemm's canal cells. METHODS: Electron microscopy used in conjunction with immunogold labelling was used to examine the ultrastructure of the basement membranes in the trabecular meshwork and to determine the presence of collagen IV, laminin, and fibronectin in six normal eyes and six eyes with POAG. To determine which cells in the meshwork synthesized these molecules, in situ hybridization was studied in an additional eight normal eyes. RESULTS: No distinctive ultrastructural changes were found in the basement membranes of glaucomatous eyes, whether early or advanced disease, when compared with normal eyes. Labelling for all three proteins was present in the basement membranes of the trabecular lamellae, Schlemm's canal, and in scattered patches within the juxtacanalicular tissue. Laminin and fibronectin were most abundant in the periphery of the sheath material surrounding the elastic tendons in the juxtacanalicular tissue. In contrast to previously published light microscopic studies, no increase in fibronectin was found in glaucoma. Regions of the basement membrane of the canal underlying giant vacuoles were similar to regions without giant vacuoles in both appearance and labelling. In situ hybridization revealed that mRNA for all three proteins was present in most trabecular cells throughout the meshwork; no regional differences in cellular labelling within were observed. CONCLUSIONS: The ultrastructural characteristics and immunogold labelling of basement membranes were similar in normal and glaucomatous eyes; no additional structures were labelled in POAG eyes that were not also labelled in normal eyes. The labelling of the patches of amorphous fibrogranular material within the juxtacanalicular tissue suggests that it is basement membrane in origin, while the sheath material which is known to accumulate in POAG was not heavily labelled and does not appear to be basement membrane in origin.
Dr C.R. Hann, Department of Ophthalmology, Mayo Clinic and Mayo Foundation, Rochester, MN, USA
Classification:
2.5 Meshwork (Part of: 2 Anatomical structures in glaucoma)
