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Age and the chemical constitution of normal human dermis.

Samples of normal dermis were collected from seven women and six men ranging in age from 17 to 81 years. The water content increased with age while the total lipid remained unchanged. The tissue was separated into fractions representing 'ground substance' (isotonic saline extract), cells (tryptic digest), and collagen (gelatin). Each fraction was analyzed for nitrogen, hydroxyproline, hexosamine and hexuronic acid. The amount of the saline extract changed little with age. The amount of both the trypsin and gelatin fractions decreased with age. None of the measured components could be related to the sex of the donor. The proteins of the isotonic saline extract were examined by cellulose acetate, disc and immunoelectrophoresis. Qualitatively, all fractions resembled the plasma proteins. The relative proportions of the proteins corresponded closely to those in the plasma. The hemaglobin content of the extract was less than one percent that expected if the proteins were present in whole blood. Most of the hyaluronate of the dermis was found in the ground substance. Dermatan sulfate predominated in the cellular and collagenous fractions. The age and sex of the donor could not be related to the concentration of any fraction. The residue resembled pure elastin in its appearance under the light microscope after staining with hematoxylin and eosin, Heidenhain's azan or aldehyde fuchsin; its ultrastructure after sonication; its nitrogen and hydroxyproline content; and its amino acid analysis. The amount increased three-fold between 20 and 80 years of age.