Age-related differences in human skin collagen: solubility in solvent, susceptibility to pepsin digestion, and the spectrum of the solubilized polymeric collagen molecules.

Age-related differences of human skin collagen in solubility, susceptibility to pepsin digestion, and the spectrum of collagen molecules were systematically examined. Less than .5% of the skin collagen were solubilized in a neutral salt solution. The solubility in acetic acid decreased rapidly during maturation and then slowly with age. Insoluble collagen from an infant was almost completely solubilized by pepsin digestion, whereas most of that from the elderly individuals remained insoluble even after four repeated times of pepsin digestion. The solubilized collagen was considered to contain a considerable amount of polymeric molecules. Characteristically, the amount of the Millipore-retained fraction of pepsin-solubilized collagen was prominent at the fourth decade. These differences represent the aging process of collagen.