HYALURONAN IN THE HUMAN TRABECULAR MESHWORK

Purpose. Hyaluronan (HA) is a high-molecular weight glycosaminoglycan that can affect water and solute fluxes in the extracellular matrix. T he distribution of HA in the human trabecular meshwork of nonglaucomat ous eyes was examined to help understand the potential role of HA in t he regulation of aqueous outflow resistance. Methods. Histolocalizatio n of HA was established in situ in the trabecular meshwork of human ey es with no known diseases of the anterior segment, A specific biotinyl ated HA-binding peptide was used as a probe for this study, with enhan ced sensitivity of HA detection achieved by modifications of the fixat ion and staining procedures. Results, Evaluation of HA staining in the aqueous outflow pathway in comparison to that in other ocular structu res (e.g., the vitreous) showed pronounced staining in the trabecular meshwork. The staining intensity was similar between various layers of the meshwork. Both the filtering and the anterior nonfiltering portio ns of the trabecular meshwork showed pronounced HA staining. The stain ing was localized primarily to the trabecular meshwork endothelial cel ls. Conclusions. Pronounced HA staining observed in the various layers of the trabecular meshwork suggests that substantial amount of HA is present in the nonglaucomatous outflow pathway. The staining pattern s uggests that HA is associated with the endothelial cells lining the tr abecular beams. This finding supports potential roles for this glycosa minoglycan in the regulation of the physiological aqueous outflow resi stance or in the maintenance of the outflow channels or both. Histoche mical localization of HA in the various layers of the nonglaucomatous meshwork provides a useful basis for future comparative studies of HA distribution and relative amounts in the trabecular meshworks of eyes affected by various types of glaucoma.