ALTERED POSTTRANSLATIONAL MODIFICATIONS OF COLLAGEN IN KELOID

Keloid is a tissue with an excessive accumulation of collagen. In this study, we have partially characterized post-translational modificatio ns of type I collagen in human keloid in order to pursue their potenti al involvement in this pathology. The levels of lysyl hydroxylation of the helical portions of alpha 1 and alpha 2 chains of type I collagen in keloid were significantly higher than those of normal, while the l evels of prolyl hydroxylation were identical between these two groups. The contents of the major reducible cross-links in dermal collagen, d ehydro-hydroxylysinonorleucine and dehydro-histidinohydroxymero-desmos ine, were both significantly higher in keloids (up to sixfold) than th ose of normal. In addition, significant amounts of hydroxylysine-aldeh yde derived cross-links that are characteristic of skeletal tissue col lagens, dehydro-dihydroxylysinonorleucine (about 0.3 mole/mole of coll agen) and pyridinoline (about 0.1 mole/mole of collagen), were found i n keloids. These results indicate that keloid-forming cells are phenot ypically different from those in normal dermis and that the collagen p roduced is highly cross-linked. The increased cross-linking provides t he fibrils with more stability that may result in an accumulation of c ollagen. (C) 1998 Academic Press.