Collagen crosslinks in human dentin: Increasing content of hydroxypyridinium residues with age

Abstract

The hydroxypyridinium crosslinks of collagen are believed to derive from reducible, divalent crosslinks. To study this concept further, both types of crosslink were quantified as a function of age in dentin, a tissue thought to have minimal collagen turnover. Human (5, 15, 28 and 56 years) and bovine (fetal and adult) root dentin was analyzed by a procedure that measures both hydroxypyridinium and reducible crosslinks on the amino acid analyzer. In human dentin, hydroxypyridinium crosslinks increased with age and became the predominant crosslinks as the two reducible residues, dehydrodihydroxylysinonorleucine and dehydrohydroxylysinonorleucine, diminished. Similarly in adult bovine dentin, hydroxypyridinium residues were sixfold more concentrated than in fetal bovine dentin. Borohydride treatment of tissue did not influence the measured content of hydroxypyridinium residues. The analyses also ruled out natural reduction as a stabilizing reaction for the divalent, reducible crosslinks. Though hydroxypyridinium residues became the major aldehyde-mediated crosslinks of adult dentin collagen, significant levels of reducible crosslinks remain throughout the tooth's adult life.

Reactions of the organic matrix in dentin caries

“…The level of lysylpyridinoline was relatively low and no significant change was observed. The cross-link levels as a whole were relatively high compared with previous reports Rivera and Yamauchi, 1993;Walters and Eyre, 1983).…”

“…Labile difunctional cross-links diminish, probably because they dissociate by the action of acid (Kuboki et al, 1977). Another possibility is the formation of mature products from difunctional cross-links as reported in vitro (Davis et al, 1975;Deshmukh et al, 1971;Robins and Bailey, 1977), such as pyridinoline cross-links (Eyre, 1981;Uchiyama et al, 1981), which are naturally present in bovine dentin (Eyre and Oguchi, 1980;Linde and Robins, 1988;Walters and Eyre, 1983;Yamauchi et al, 1992).…”

“…These cross-links may then react with another oxidized residue to form trifunctional cross-links. The collagen cross-links in dentin are the difunctional didehydro-dihydroxylysinonorleucine (∆-DHLNL) and didehydro-hydroxylysinonorleucine (∆-HLNL), and the trifunctional hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) Kuboki et al, 1981;Linde and Robins, 1988;Mechanic et al, 1971;Mechanic et al, 1974;Walters and Eyre, 1983;Yamauchi et al, 1992). Lysinoalanine and histidinoalanine fall into a different category and form links between collagen and phosphoproteins (Fujimoto et al, 1981;Fujimoto et al, 1982).…”

“…1). Predentin, on the other hand, contains more difunctional and fewer trifunctional cross-links than dentin (Linde and Robins, 1988;Walters and Eyre, 1983;Yamauchi et al, 1992). These cross-links connect the non-helical extension 8 Chapter 1 of one molecule with the adjacent helical part of another molecule (Kuboki et al, 1981; Kuboki et al, 1993).…”

Análise do selamento marginal de restaurações realizadas após remoção de cárie radicular com o laser de Er, Cr:YSGG

“…O conteúdo orgânico é formado por aproximadamente 90 % de colágeno tipo I, sendo o restante composto por uma mistura de citratos, lipídeos e proteínas não colágenas, incluindo as fosfoproteínas e os proteoglicanos. Alguns estudos indicaram que os componentes orgânicos da dentina diferem de acordo com a idade e até mesmo com a localização da dentina (RAHIMA; VEIS, 1988;STEINFORT et al, 1989;WALTERS;EYRE, 1983;).…”