MDI 301 is a picolinic acid-substituted ester of 9-cis retinoic acid. It has been shown in the past that MDI 301 increases epidermal thickness, decreases matrix metalloproteinase (MMP) activity, and increases procollagen synthesis in organ-cultured human skin. Unlike all-trans retinoic acid (RA), MDI 301 does not induce expression of proinflammatory cytokines or induce expression of leukocyte adhesion molecules in human skin. In the present study we examined topical MDI 301 treatment for ability to improve the structure and function of skin in three models of skin damage in rodents and for ability to improve abrasion wound healing in these models. MDI 301 was applied daily to the skin of rats treated with the potent corticosteroid, clobetasol propionate, to the skin of diabetic rats (8 weeks posttreatment with streptozotocin) and to the skin of aged (14-16-month-old) rats. In all three models, subsequently induced abrasion wounds healed more rapidly in the retinoid-treated animals than in vehicle-treated controls. Immediately after complete wound closure, tissue from the wound site (as well as from a control site) was put into organ culture and maintained for 3 days. At the end of the incubation period, culture fluids were assessed for soluble type I collagen and for MMPs-2 and -9. In all three models, the level of type I collagen was increased and MMP levels were decreased by MDI 301. In all three models, skin irritation during the retinoid-treatment phase was virtually nonexistent.Minor abrasions that occur in healthy skin are expected to heal without incident. Interventions are designed primarily to prevent infection and to provide support for the body's own regenerative mechanisms. In contrast, wounds in chronically damaged and atrophic skin often go on to form nonhealing ulcers with devastating consequences. Diabetes alone is a contributing factor in up to 70% of the > 55,000 amputations that occur annually. [1][2][3][4] Skin that has become atrophic as a consequence of the aging process also demonstrates impaired wound healing, 5-7 as does skin that has been damaged as a result of extended corticosteroid use. [8][9][10] The majority of wound-healing research is directed toward understanding the pathophysiology of impaired wound healing and identifying interventions that can mitigate the critical patho-physiological events.Several past studies have demonstrated the efficacy of all-trans retinoic acid (RA) and its parent compound all-trans retinol (ROL, vitamin A) in wound healing. Although most studies have focused on wounds in the skin, [11][12][13][14][15][16][17] retinoid efficacy has also been demonstrated in healing of wounds in other tissues (bone, cornea, respiratory tract, upper digestive system, and gut). 27 Likewise, skin irritation is also a complication with synthetic retinoidal agents currently on the market. 28 Irritation is a major cause of non-compliance among retinoid users. In addition, excessive irritation may counteract the beneficial effects of retinoid use or actually predispo...