TOPICAL RETINOIC ACID FOR PHOTOAGED SKIN - THERAPEUTIC EFFECTS AND MECHANISMS

Topical all-tuans-retinoic acid actively repairs photoaged skin, Rough ness is the first parameter to show improvement, and is related to epi dermal hyperproliferation, compaction of the stratum corneum and incre ase in epidermal glycosaminoglycans. Lightening of hyperpigmented lesi ons is correlated with a reduction in epidermal melanin content, Reduc tion in wrinkling occurs later, and is probably related to deposition of new collagen in the upper dermis, Epidermal atypia and dysplasia ar e also improved, Side-effects of dryness, peeling, erythema and irrita tion are dose-dependent, and diminish with continued treatment, The ex tent of the role of non-specific irritation, if any, is yet to be dete rmined, Specific nuclear retinoid receptors exist, and are present in skin, Within the nucleus the vitamin - receptor complex binds to speci fic DNA sequences - response elements - situated in specific retinoid target genes, thereby regulating transcription of these target genes, The precise genes targeted by the retinoid receptors, and the exact me chanism of action of retinoic acid in the process of repairing photoag eing, remain to be established.