GLYCOSAMINOGLYCAN STRATIFICATION OF THE JUXTACANALICULAR TISSUE IN NORMAL AND PRIMARY OPEN-ANGLE GLAUCOMA

Purpose. The juxtacanalicular tissue (JCT) is the probable site of aqu eous outflow resistance in normal eyes and of the increased resistance in primary open-angle glaucoma eyes (POAG). The purpose of this histo chemical study was to determine the glycosaminoglycan (GAG) compositio n and stratification in the JCT of POAG and age-matched normal eyes. M ethods. Five eyes from four normal donors and five eyes from four POAG donors (69 to 80 years of age) were analyzed. Using methods that hist ochemically presence GAGs, GAG-degrading enzymes, Alcian blue staining , and real color discrimination to exclude pigment, nuclear staining a nd unstained areas, the type and amount of GAGs were estimated by comp uter-aided charge-coupled device color video image analysis. To examin e GAG stratification, the JCT was segmented into three regions-anterio r, middle, and posterior-to examine regional differences in GAG compos ition; each region was further divided into four 2-mu m layers, from l ayer 1, adjacent to and including the endothelium of Schlemm's canal t o layer 4, to the first trabecular lamellae. Results. The normal GAGJC T profile was as follows: hyaluronic acid (HA), 7.78+/-1.23 femtograms (fg)/mu m(2); chondroitin sulfates (CS), 8.18+/-0.82 fg/mu m(2); derm atan sulfate, 0.29+/-0.18 fg/mu m(2); the total, 18.73+/-0.68 fg/mu m( 2). In contrast, the POAG GAGJCT profile was as follows: HA 0.57+/-0.3 1 fg/mu m(2) (P <0.00001), a 93% decrease; CS 13.49+/-0.74 fg/mu m(2) (P <0.0001), a 83% increase; dermatan sulfate, 0.90+/-0.53 fg/mu m(2); and the total, 17.31+/-0.95 fg/mu m(2), an 8.2% decrease. The HA was depleted in all layers of all regions of POAGJCT. Conclusions. Results indicate that the normal JCT is stratified, with HA as the predominan t GAG in layers 1 and 2. The POAG JCT is depleted of HA and has an acc umulation of CS, which may increase outflow resistance and, consequent ly, increase intraocular pressure in patients with POAG.