Topical retinoic acid treatment of photoaged skin: its effects on hyaluronan distribution in epidermis and on hyaluronan and retinoic acid in suction blister fluid.

Topical treatment with retinoic acid (tretinoin, vitamin A acid) has been reported to partly reverse signs of photodamage. To determine whether the histochemical distribution of hyaluronan (hyaluronic acid, HYA) in the epidermis and dermis and the amounts of HYA and retinoic acid in suction blister fluid were influenced by such topical treatment, 14 subjects healthy apart from moderate photodamage were instructed to treat the lateral forearm with 0.01-0.05% retinoic acid cream for 6 months. In a study of the short-term effects, another six subjects applied 0.05% retinoic acid cream for 2 weeks. After 6 months the thickness of the vital epidermis had increased by 23%. The HYA staining was based on a specific immunohistochemical method in which hyaluronan-binding protein is used. Before treatment HYA was seen as a meshwork around the cells in the upper half of the stratum spinosum. After 6 months of treatment this meshwork had increased in thickness by 31% compared with pretreatment specimens. The HYA staining was already intense in the papillary dermis before treatment and no difference was observed after 6 months' treatment. The mean concentration of HYA in blister fluid had increased significantly (43%) after 2 weeks of treatment whereas after 6 months there was no significant difference in this respect between the treated and untreated arm. The increase in the thickness of the epidermal HYA meshwork after 6 months and the blister fluid HYA after 2 weeks may indicate that HYA is involved in the epidermal change induced by topical retinoic acid therapy.(ABSTRACT TRUNCATED AT 250 WORDS)