RESTORATION OF COLLAGEN FORMATION IN PHOTODAMAGED HUMAN SKIN BY TRETINOIN (RETINOIC ACID)

Background. Topical tretinoin (retinoic acid) modifies fine wrinkles a nd certain other features of human skin damaged by exposure to the sun (photodamage), but histologic changes do not account for this improve ment. In mice with photodamage induced by ultraviolet light, effacemen t of fine wrinkles by tretinoin is correlated with dermal collagen syn thesis but not with histologic changes. We investigated whether collag en synthesis was reduced in photodamaged human skin and, if so, whethe r it could be restored by treatment with topical tretinoin. Methods. B iopsies of photodamaged skin from the extensor aspect of the forearm a nd skin from the buttocks, which had been protected from the sun, were performed on 26 healthy subjects. In addition, 29 patients with photo damaged skin were treated for 10 to 12 months with a daily application of 0.1 percent tretinoin cream (15 patients) or vehicle cream (14 pat ients). Skin-biopsy specimens obtained at base line and after treatmen t were assessed immunohistologically for evidence of dermal collagen I formation (collagen synthesis). Results. Collagen I formation was 56 percent less in the papillary dermis of photodamaged skin than in skin protected from the sun (P<0.001) and was correlated with the clinical severity of photodamage (r = -0.58, P = 0.002). Treatment of photodam aged skin with tretinoin produced an 80 percent increase in collagen I formation, as compared with a 14 percent decrease in collagen formati on with the use of vehicle alone (P = 0.006). Conclusions. The formati on of collagen I is significantly decreased in photodamaged human skin , and this process is partly restored by treatment with tretinoin.