Human skin collagen from different age groups before and after collagenase digestion; an electron microscopic study.

That some alteration in collagen occurs with age has been indicated by various workers. Young rat tendon (Neuberger and others, 1951) shows a greater radioactive glycine turnover than that of adult animals. Similar findings were reported in the skin of rats (Neuberger and Slack, 1953) and rabbits (Harkness and Neuberger, 1952). Under the electron microscope the collagen fibres in newborn rat skin were shown to be narrower than in older rats (Gross, 1950). Human skin, tendon, and dura collagen was found to vary in extractability with dilute acid according to age, being more soluble below the age of one year (Banfield, 1952). The excretion of hydroxyproline in children was significantly greater than in adults (Ziff and others, 1954), indicating the presence of an increased pool of hydroxyproline peptide for collagen synthesis in the growing individual. The authors found no difference between patients with or without collagen disease. Previous chemical studies (Keech, 1954a) showed a significant difference in digestion between the skin collagen of infants and adults following incubation with collagenase, but again no difference between patients with or without collagen disease. It appeared to be of interest to find out whether collagen from different age groups differs in its response to collagenase, and whether there is any correlation with different types of disease, particularly "collagen disease". This paper describes the effect (macroscopic and electron microscopic) of collagenase on extracted human skin collagen from