Topical retinoic acid changes the epidermal cell surface glycosylation pattern towards that of a mucosal epithelium

Topical all-trims retinoic acid (RA) produces a nutnber ol epidermal changes which are indistinguishable l'rom those observed following treatment with a local irritant, namely sodium lauryl sulphate (SI.S).Thisdhserviition has led to criticism thai the efficacy of RA in disorders such as photoageing.Is merely a result of irrilancy.In stratitied epithelia.the cellular difterentiation process is characterized by a stepwise synthesis of cell surface carhohydrates.and each type of stratitied epithelium has its own specific pattern of carbohydrate expression.Glycosyltrimsferases. which are responsible for carbohydrate synthesis, are influenced by retinoids.Thus, we investigated whether epidermal cell surface glycosylation is altered in skin treated with topical RA, and contrasted it wilh changes induced by topical SLS.Skin biopsies were obtained from seven normal volunteers who had been treated, on three separate areas of buttock skin, with single applications of 0 1% RA. 2% SLS, or vehicle creatiis, followed by 4-day occlusion.Biopsies were assessed imniunohistologically using highly specific monoclonal antibodies lo cell surface carbohydrates (types 1, 2 and 3 chain structures), previously demonstrated in the epidermis and iti oral mucosal epithelium.Although type 1 chain structures were not demonstrated in any of the samples, the distribution of type 2 and 3 chain structures in RAtreated epidermis was altered towards that seen in a mucosal epithelium.T antigen, a mucin-type cell surface carbohydrate structure normally expressed throughout the epidermis, was only observed in the granular layer of RA-treated epidermis-a feature of mucosal epitheiia.Le^, normally only seen in non-keratinized buccal epithelium, was strongly expressed in RA-treated epidermis.In contrast, the glycosylalion pattern of the SLS-treated epidermis was tiot significantly different frotn that observed after vehicle treatment.Thus, RA treattnent converts normal stratified epithelium towards the phenotype of mucosal epitheliutn with a decrease in T antigen and a concomitant increase in Le^.These changes iire not observed following treatment with SLS and identify an itnportant difference between RA elTects and irritancy.