Characterization of dermal type I collagen of C3H mouse at different stages of the hair cycle.

Hair follicles develop or regress in accordance with the hair cycle. In this study, we partially characterized fibrillar type I collagen, the predominant component in the dermis, at two stages of the hair cycle: anagen and telogen. Skin samples were obtained from the backs of two groups of 11-week-old C3H mice: one at anagen stage induced by shaving and the other at telogen stage. The amount of neutral salt-soluble (newly synthesized) collagen obtained from anagen skin was about twofold that from telogen skin, while the level of acid-soluble collagen was not significantly different between the two groups. The degree of lysine hydroxylation of pepsinized type I collagen obtained from anagen skin was significantly higher than that in telogen (5.0% higher in alpha1 chain, and 15.6% higher in alpha2 chain). Proline hydroxylation at the anagen stage was also slightly higher than in the telogen stage. Two major collagen cross-links were found in both groups of skin; dehydro-hydroxylysinonorleucine and dehydro-histidinohydroxymerodesmosine. The concentration of the latter, a complex tetravalent cross-link, was significantly lower in anagen skin when compared with telogen skin (mean +/- SD 0.64 +/- 0. 07 vs. 0.78 +/- 0.06 mol/mol collagen). The former showed no significant difference between the two groups. In addition, a significant amount of lysyl-aldehyde (a cross-link precursor) was found in anagen (0.16 +/- 0.02 mol/mol collagen), while it was 0.12 mol/mol collagen in telogen. These results indicate that the remodelling of collagen is more active in anagen skin than in telogen, and that characteristic post-translational modifications of dermal collagen seen in anagen may play a part in facilitating an environment around hair follicles for their migration and growth.