Glycosaminoglycans and Outflow Pathways of the Eye and Brain

Abstract

The etiology of the majority of defects of the outflow pathways of aqueous humor (glaucoma) and cerebrospinal fluid absorption (hydrocephalus) is unknown. A considerable amount of evidence indicates that glycosaminoglycans have a role in regulating fluid movement through connective tissues such as the trabecular meshwork of the eye and the arachnoid of the brain. Both the eye and the brain outflow pathways have hyaluronic acid and chondroitin sulfate within the filtration barrier. The physiological significance of glycosaminoglycans in the outflow pathways may be their ability to form highly viscous and elastic gel-like solutions that function as a selective biological gel filtration system, which maintains normal intraocular and intracranial pressure. We suggest that glycosaminoglycans may act to maintain the unidirectional character, low-flow fluid movement, and pressure gradient between the trabecular lamellae and the drainage channels of the eye and the brain. This review of the outflow pathways of the eye and the brain discusses the cell biology of glycosaminoglycans in regulating normal aqueous outflow and cerebrospinal fluid absorption.

Effect of glucosamine on intraocular pressure: a randomized clinical trial

“…Another theory to explain this observation is that high concentration of GAG in aqueous draws more water into the anterior chamber as a result of osmotic effect, thus induces swelling and compromising of pore sizes, leading to high IOP. 7 We did not find diabetes mellitus, cardiovascular disease, and gender as risk factors for glucosamineinduced hypertension; but age was significantly associated with rise of IOP in the treatment group. Several histological studies demonstrated age-related structural and functional changes including loss of cellularity, collagen and extracellular matrix accumulation, thickening and fusion of trabecular sheats.…”

“…5 Although glucosamine is the main component of the cartilage, it is also abundant in corneal stroma and contribute morphological and functional characteristics to trabecular meshwork. 6,7 Glucosamine is frequently prescribed for patients with OA, and radiographic studies have shown its efficacy in slowing joint space width loss. 8,9 In most countries oral glucosamine supplement is available as over the counter medication.…”

The Cause of Chiari II Malformation: A Unified Theory

“…There is increasing evidence that the extracellular matrix and the cellular activity of cerebrospinal outflow pathway are influenced by time-dependent inductive factors [35,66]. A series of morphogenetic and bio chemical events yield a functional outflow pathway.…”

Role of receptors in the trabecular meshwork of the eye as targeted to the development of antiglaucoma therapy

“…Proteoglycans consist of numerous glycosaminoglycans that interact with molecules in the basement membrane. cellular spaces of the TM are lined by a gel-like substance made up of proteoglycans and glycosaminoglycans such as keratan sulfate, heparan sulfate, chondroitin sulfate, and dermatan sulfate [Knepper and McLone, 1985;Acott et al, 19851. Hyaluronic acid is also present in large amounts as a free glycosaminoglycan.…”