Long-term treatment of photoaged human skin with topical retinoic acid improves epidermal cell atypia and thickens the collagen band in papillary dermis

Risk of photocarcinogenesis and the relevance of collagen in wrinkle effacement are two issues related to prolonged use of retinoic acid (RA) that have not been fully addressed.Our purpose was to investigate the degree of epidermal cellular atypia and the thickness of papillary dermal collagen in photoaging after long-term use of RA.Thirty-four subjects with photoaged skin were treated daily with 0.05% RA for at least 6 months. Epidermal cellular atypia was graded by means of a semiquantitative scale. Thickness of collagen band was measured by using image-analysis software.Compared with pretreatment findings, melanocytic and keratinocytic atypia was significantly reduced and the collagen band thickness doubled.This was an open-label study.Improvement in epidermal cellular atypia is consistent with the ability of RA to act as a chemopreventive agent in epithelial carcinogenesis. Prolonged use also significantly increased collagen matrix deposition in dermal repair zones, which most likely contributes to wrinkle effacement by RA.