Age-related changes in the concentration of pyridinoline cross-links in human skin.

Abstract

The pyridinoline cross-links of collagen were first isolated from Achilles tendon by Fujimoto et al., I who reported pyridinoline present in significant levels in collagen of hypertrophic scars, but virtually absent in collagen of normal skin, as detected by fluorescence. The two forms of the structure of pyridinoline, namely Iysyl pyridinoline and hydroxylysyl pyridinoline, were further investigated by Eyre et al.', who postulated that the formation of pyridinoline results from a nucleophilic reaction, involving two existing cross-links between two separate collagen fibres. The underlying mechanism behind the presence of significant levels of pyridinoline cross-links in hypertrophic scar is still uncertain; one hypothesis is that it is the result of free radical generation.' The biological significance of these pyridinoline cross-links has yet to be established. Recent work has shown that there is a correlation between age and concentration of hydroxypyridinium cross-links in functionally different skeletal muscles. One study, using high-performance liquid chromatography techniques, showed significant increases in pyridinoline concentration during maturation in rats, During maturation the concentration of soluble collagen in muscles decreased, whilst the tensile strength and mechanical stiffness increased. However, Takahashi et al. reported that there was no significant change in pyridinoline between the content in various tissues from young and old human subjects.! The purpose of the present work is to investigate the relationship between pyridinoline concentration and age in human skin, which as far as the authors are aware, has not been reported before.