Osteogenesis imperfecta: biochemical studies of bone collagen

The biochemical properties of tibial bone collagen, obtained from patients with osteogenesis imperfecta, were studied by investigating amino acid composition, subunit composition and crosslink formation. Direct comparison of this bone was made with normal bone, age and sex matched, which had been removed from the tibiae of individuals within 48 hours after accidental death. The amino acid compositions of OI and normal bone collagen were almost identical and the pepsin solubilized collagen fraction as well as the CNBr peptides of insoluble bone collagen were very similar, indicating that no differences in collagen genetic type occurred in OI compared to normal. The crosslink contents and the specific radioactivities of the insoluble collagens were determined following NaB3H4 reduction. The specific radioactivity values of OI bone collagen were found to average 50 per cent higher than normal collagen. Analyses of OI collagen showed abundant formation of the major reducible aldehydes and crosslinks. Compared to the controls there were much higher proportions of the reduced aldehyde, dihydroxynorleucine and the reduced crosslink, dihydroxylysinonorleucine. These results may indicate delayed maturation of crosslinking in OI bone collagen and may reflect diminished stability of such collagen during bone development.