Intrinsic aging- and photoaging-dependent level changes of glycosaminoglycans and their correlation with water content in human skin

Abstract

Background: Glycosaminoglycans (GAGs) have various structural and physiological regulatory functions in skin, including tissue water maintenance, due to their high water-holding capacity.

Objective: To investigate changes of GAGs during intrinsic aging and photoaging of human skin and their correlations with water content.

Methods: Samples of sun-protected buttock and sun-exposed forearm skin were obtained from young male (21-30 years, n=8) and female (20-33 years, n=8) subjects, as well as old male (70-78 years, n=8) and female (70-80 years, n=8) subjects, and their epidermal and dermal contents of hyaluronic acid (HA), total sulfated GAG (tsGAG), total uronic acid (tUA), and tissue water were measured. HA content was determined by enzyme-linked immunosorbent assay using HA-binding protein, tsGAG by the sulfated GAG assay kit using 1,9-dimethylmethylene blue, tUA by carbazole reaction, and tissue water by subtraction of tissue dry weight from wet weight.

Results: In the buttock, HA was higher in dermis than in epidermis, while tsGAG and tUA were higher in epidermis. In intrinsically aged buttock, epidermal HA and dermal tsGAG and tUA decreased. However, when analyzed for each gender, epidermal tsGAG, tUA, and tissue water decreased only in females. Forearm/buttock ratios of each molecule were compared for determination of photoaging-dependent changes. Forearm/buttock ratios of HA, tsGAG, tUA, and tissue water increased in aged dermis, but showed no change in aged epidermis. When analyzed for each gender, ratios of epidermal HA and tissue water increased only in aged females, while ratios of epidermal tsGAG, tUA, and tissue water decreased only in aged males. Correlations of water content with HA, tsGAG, and tUA were found in epidermis, but not with tsGAG in dermis.

Conclusion: These intrinsic aging- and photoaging-dependent GAG changes and their correlations with water content provide new insights into the pathophysiology of dry skin in the elderly.