Effects of chondroitin sulfate on trabecular meshwork in rabbit eyes: an electron microscopic study.

The intraocular pressure of four New Zealand albino rabbit eyes was elevated when we replaced the aqueous humor of these eyes repeatedly with a chondroitin sulfate solution. Seen by electron microscopy, the trabecular meshwork of these eyes showed moderately increased collagen fibers, elastic fibers, and fine fibrils, and thickening of basement membrane. The amount of extracellular material present was markedly increased when compared with control eyes. Three types of basement membranes were noted. Compact multilaminated basement membrane and placoid accumulations of filamentous material with a granular background were found adjacent to the endothelial cells of the trabecular meshwork, and fine fibrils were observed around the angular aqueous veins. The ultrastructural alterations we observed were similar to those seen in some human glaucoma cases. The metabolism of trabecular meshwork cells may be affected by the long-term chondroitin sulfate treatment. As a result, extracellular matrix material appears to be accumulated in the trabecular meshwork, which may then contribute to an increased outflow resistance and a mild intraocular pressure elevation.