...and here´s the first study that suggested that retinoic acid (tretinoin) could repair and treat aging skin (photoaging). It´s from 1984
so although many on this board is excited by retinoids (and they should be!), it´s not exactly new.
Connect Tissue Res. 1984;12(2):139-50.
Topical retinoic acid enhances the repair of ultraviolet damaged dermal connective tissue.Kligman LH, Duo CH, Kligman AM.
Ultraviolet (UV) irradiation induces excessive accumulations of elastic fibers in animal and human skin. Collagen is damaged and glycosaminoglycans are vastly increased. Formerly considered an irreversible change, we recently showed, post-irradiation, that a band of normal connective tissue was laid down subepidermally . Because of its ability to stimulate fibroblasts and enhance healing of wounds, we thought it likely that retinoic acid (RA) would promote the formation of this subepidermal zone of reconstruction. Hairless mice were irradiated for 10 weeks with Westinghouse FS20 sunlamps for a total UV dose of 7 J/cm2. Then, 0.05% RA was applied for 5 and 10 weeks. Observations were made by light and electron microscopy. In contrast to controls treated with vehicle, the reconstruction zone was significantly wider in RA-treated mice. The enhanced repair was dose related. Histochemically and ultrastructurally, collagen was normal, fibroblasts were numerous and in a configuration of high metabolic activity.
PMID: 6723309
A lot of research followed this, on human and animal skin, where they showed increased collagen synthesis
in vivo and repair of UV-damage. If you want to read the early studies search for "kligman" AND "tretinoin" on pubmed. Here is a little more recent summary:
Clin Geriatr Med. 2001 Nov;17(4):643-59
Photoaging: pathogenesis, prevention, and treatment.Kang S, Fisher GJ, Voorhees JJ.
Department of Dermatology, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
Premature skin aging, or photoaging, results largely from repeated exposure to ultraviolet (UV) radiation from the sun. Photoaging is characterized clinically by wrinkles, mottled pigmentation, rough skin, and loss of skin tone; the major histologic alterations lie in dermal connective tissue.
In recent years, a great deal of research has been done to explain the mechanism by which UV induces dermal damage. This research has enabled the identification of rational targets for photoaging prevention strategies.
Moreover, studies that have elucidated photoaging pathophysiology have produced significant evidence that
topical tretinoin (all-trans retinoic acid), the only agent approved so far for the treatment of photoaging, also works to prevent it. This article summarizes evidence mainly from studies of human volunteers that provide the basis for the current model of photoaging and the effects of tretinoin.
PMID: 11535421
PS since that was published tazarotene, a selective stronger retinoid with more anti-inflammatory and comedolytic properties, was also approved by FDA for the treatment of aging skin DS
Edited by fredrik, 24 November 2007 - 12:40 AM.