Morphometric analysis of dermal collagen fibers in normal human skin as a function of age

A quantitative study of dermal collagen as a function of age was carried out by computerized digital image analysis. Fast Green-Syrius Red stained sections were obtained of skin biopsies taken from the upper inner arm of 33 healthy women and 38 healthy men. The Leitz texture Analysis System (Leitz-TAS) and mathematical morphology (Serra, 1982) were used for the evaluation of the data. Collagen was studied in the superficial dermis and also in the reticular dermis using the same program. There were significant correlations, firstly between the percentage of collagen measured by the morphometric method and the concentration of collagen analysed biochemically (microg/mm(2) of tissue section) (r = 0.79, p < 0.001) and secondly between the decreased concentration of collagen and age (r = 0.58, p < 0.05). The morphometrical measurements have shown that the relative percentage of collagen bundles (surface of collagen fibers as a function of the dermal area analyzed) was 93.35% in the superficial dermis and 89.2% in the reticular dermis. Although this value is higher than the chemically determined ratio of collagen to other proteins (over 70%), this may be due to the relatively uniform distribution pattern of (type I and III) collagen through the dermis covering most other components of the skin. As the collagen fiber density per unit dermal surface did not change with age, the decrease in collagen content of the skin may be ascribed to the loss of about 6% of dermal mass per decade (Branchet, 1990), although large individual variations exist. The histogram of the diameter distribution of collagen fiber bundles of the reticular dermis showed thinner diameters in persons between 20 and 40 years of age than in older persons. The histogram of the distribution of interfiber spaces did not show any variation with age in the superficial dermis, while in the reticular dermis there was a predominance of smaller interspaces in persons older than 50 years.