Age-related changes of scleral hydration and sulfated glycosaminoglycans

Human scleras were analyzed to determine if tissue hydration changed in an age-related fashion, and whether this change could be related to decreased levels of glycosaminoglycans. The anterior half of normal human scleras were examined with donor ages ranging from newborn to 99 years (n = 40). Tissue hydration was found to decrease by 1.06% per decade (P = 0.0012). Glycosaminoglycans were extracted from scleras with guanidine hydrochloride, purified by anion exchange chromatography and quantitated using dimethylene blue and selective enzymatic digestion. The glycosaminoglycans of the sclera were primarily dermatan sulfate and chondroitin sulfate with small quantities of hyaluronic acid. While no loss of chondroitin sulfate with age was detected, a significant age-related loss of dermatan sulfate was found (P = 0.0006, n = 14). An examination of the relationship between glycosaminoglycan concentration and scleral hydration showed that increased levels of sulfated glycosaminoglycans were associated with increased levels of scleral hydration (P < 0.02, n = 14). No improvement in the correlation could be achieved by considering either dermatan sulfate or chondroitin sulfate individually. Our results suggest that, as in other connective tissues, aging is associated with a loss of glycosaminoglycans, and their loss is coincident with decreased tissue hydration.