Vitamin A antagonizes decreased cell growth and elevated collagen-degrading matrix metalloproteinases and stimulates collagen accumulation in naturally aged human skin. - Varani,J.; Warner,R.L.; Gharaee-Kermani,M.; Phan,S.H.; Kang,S.; Chung,J.H.; Wang,Z.Q.; Fisher,G.J.; Vorhees,J.J. (J Invest Dermatol, 2000)