Trabecular meshwork phagocytosis in glaucomatous eyes.

Trabecular meshwork cells are actively phagocytic and may function to keep the drainage pathways free of cellular debris, pigment and other material. A decrease in phagocytic capacity has been proposed in the pathogenesis of glaucoma. This study was performed to compare the phagocytic capability of the human trabecular meshwork in glaucomatous and normal human eyes. The anterior segments of 6 donors with glaucoma (primary open-angle glaucoma, POAG: 5 donors; pseudoexfoliative glaucoma, PEX: 1 donor) and 6 normal donors were placed in perfusion organ culture. During the final 24 h of culture, latex microspheres, labeled with FITC and coated with antibodies, were perfused into the anterior segments. Eyes were then fixed, the trabecular meshworks were treated with a rhodamine-labeled secondary antibody, sectioned and the number of ingested beads determined with the laser scanning confocal microscope. Nuclei were quantitated and used to calculate the phagocytic index of each eye (number of ingested beads/number of nuclei). Anterior segments of glaucomatous donors were cultured for 1-3 days, as a preliminary culture study had revealed that culture of glaucomatous anterior segments is successful in only 50% when cultured for 21 days. Specimens of normal donors were cultured for 21 days. Ingested beads appeared green and could be differentiated from noningested beads, which appeared red, using appropriate wavelengths of the laser. Bead ingestion was confirmed with electron microscopy and the use of a secondary antibody labeled with horseradish peroxidase. Ingestion rates appeared similar among all three groups of eyes: POAG, 3.8 beads/cell; PEX, 3.3 beads/cell; normal, 3.5 beads/ cell. No evidence of significant migration or loss of trabecular cells was noted. Cell counts were not significantly different: POAG, 127 +/- 40 cells/section; normals, 136 +/- 49 cells/section. In conclusion, the phagocytic ability of the trabecular meshwork appears similar between eyes with POAG and normal eyes in perfusion organ culture. Cell loss after phagocytosis was not observed in these single-exposure experiments.