Time-dependent changes of collagen cross-links and their precursors in the culture of osteogenic cells.
The early stage of cross-link formation in bone collagen was studied in a cell culture system. An osteogenic cell line that produces and accumulates a remarkably high amount of collagen, and that eventually forms bone-like structures, was used in this study for its time-dependent development of reducible cross-links. It was found that precursors of the cross-link, dehydro-dihydroxynorleucine and dehydro-hydroxynorleucine became detectable as soon as the cells attained a confluent state. They showed maximal amounts at days 3-5 after confluence, but substantially disappeared at day 10 after confluence. In contrast, two characteristic cross-links of bone collagen, dehydro-dihydroxylysinorleucine (dehydro-DHLNL) and dehydro-hydroxylysinorleucine (dehydro-HLNL), which were present in trace amounts at the stage of cell confluence, gradually increased in amount and reached a plateau at day 10, just when their precursors disappeared. Thus, it was found that there was a time lag of about a week between the maximal formations of precursors and cross-links of bone collagen in this system. The significance of this time lag was interpreted in terms of the minimum essential accumulation of collagen for the precursor-product transition. The ratio of dehydro-DHLNL to dehydro-HLNL was as low as 0.7 at day 3 after confluency, increased to 4.2 at day 20, the period just before mineralization began, and decreased thereafter, suggesting a qualitative change in bone collagen associated with mineralization.
Kuboki
Y
Y
Department of Biochemistry, School of Dentistry, Hokkaido University, Sapporo, Japan.
Kudo
A
A
Mizuno
M
M
Kawamura
M
M
D000818:Animals; D001842:Bone and Bones / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D002113:Calcification, Physiologic / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D004151:Dipeptides / Q000032:analysis / Q000378:metabolism; D006882:Hydroxyapatites / Q000032:analysis / Q000378:metabolism; D051379:Mice; D010010:Osteoclasts / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology*; D011498:Protein Precursors / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D013997:Time Factors
D004151:Dipeptides; D006882:Hydroxyapatites; D011498:Protein Precursors; C007428:5,5'-dihydroxylysylnorleucine; C010991:delta-hydroxylysylnorleucine; D003094:Collagen