Vitamin A antagonizes decreased cell growth and elevated collagen-degrading matrix metalloproteinases and stimulates collagen accumulation in naturally aged human skin. - Varani,J.; Warner,RL.; Gharaee-Kermani,M.; Phan,SH.; Kang,S.; Chung,JH.; Wang,ZQ.; Datta,SC.; Fisher,GJ.; Voorhees,JJ. (J Invest Dermatol, 2000)