LOCALIZATION OF ELASTIN IN THE NORMAL AND GLAUCOMATOUS HUMAN TRABECULAR MESHWORK

Purpose. The extracellular materials (ECMs) in the trabecular meshwork (TM) are thought to play a crucial role in aqueous outflow resistance . Immunohistochemical localization of elastin, one of the major ECMs i n the normal and glaucomatous human TM, was examined ultrastructurally . Methods. Eight normal eye bank eyes and 16 trabeculectomy specimens of primary open angle glaucoma (POAG, 11 eyes from 8 cases), congenita l glaucoma (2 eyes from 1 case), and juvenile glaucoma (3 eyes from 2 cases) were embedded in Lowicryl K4M at low temperature. The distribut ion of elastin was studied by the protein A-gold technique. Results. I n normals, the gold particles indicating the antigenic sites for elast in existed mainly in the central amorphous element of the elastic-like fibers, and a few gold particles were observed within the area contai ning fine granular-like material and fine fibrillar-like material. No Iabeling was observed in cellular materials or other ECMs. In congenit al and juvenile glaucoma, labeling was similar to that observed in nor mals. In POAG specimens compared to normals, there was an increased am ount of elastin-bound immunogold particles along the inner canal endot helium. The increased gold particles, which did not have a fibrillar a rrangement and were not enclosed by electron-dense microfibrils, were found within the area containing fine fibrillar-like material. However , labeling within the elastic-like fibers was similar to that observed in normals. Conclusions. Under electron microscopy, elastin could be localized in the normal and glaucomatous human TM. The results of this investigation suggest that elastin may play an important role in the etiology of POAG.