Trabecular meshwork and elastin

Evidence that elastic fibers with elastin exists in the trabecular meshwork (TM) and play an important role in aqueous outflow resistance is presented. The elastic fibers consist of abundant microfibrillar components containing glycoproteins and amorphous components containing elastin. If TM tissues are digested with elastase, the cells composing trabecular sheets and Schlemm's canal are separated with a decrease of elastin and come in contact with each other with reproduction of elastin. When the anterior segments of eyes are perfused with elastase, the intraocular pressure drops with a decrease of outflow resistance. A large quantity of elastin exists in fine fibrils lying underneath the trabecular wall of Schlemm's canal in primary open angle glaucoma (POAG) eyes, in pseudoexfoliation (PE) materials of PE glaucoma eyes and in basement membrane and fine fibril-like materials of steroid glaucoma eyes. In congenital and juvenile glaucoma eyes, however, instead of elastin, fibronectin localizes in basement membrane and fine fibril-like materials. When TM tissues respond to steroid hormone, the tissues synthesize and secret microfibrils and elastin, components of the elastic fibers. Elastin gene expresses in human TM. Orally administered elastase is transferred in aqueous humor and digests elastin in TM. Therefore it is possible that such a drug decreases the outflow resistance of glaucoma eyes.