Age-related changes of noncalcified collagen in human cortical bone

It is well known that osteoid, which contains a noncalcified collagenous matrix, is formed during the initial stage of bone formation during the bone remodeling process. Thus, synthesis of defective collagen molecules in osteoid may cause abnormal bone formation, thereby leading to changes in bone quality. The objective of this study was to investigate age-related changes in noncalcified collagen molecules in osteoid and its likely effects on the mechanical integrity of human cortical bone. Thirty human cadaveric femurs were divided into three age groups: young adults, middle age, and the elderly, respectively. A novel high performance liquid chromatography approach was employed to quantify the denaturation of noncalcified collagenous matrix in addition to mechanical tests of bone. Bulk concentrations of both enzymatic and nonenzymatic collagen cross links in bone also were measured. Moreover, the number of newly formed osteons per unit area and the bony area fraction of these osteons were estimated. The results of this study indicate that denaturation of the noncalcified collagenous matrix in bone increases with increasing age. In addition, such collagen denaturation in osteoid exhibited a correlation with nonenzymatic collagen cross links as well as the strength and toughness of bone. These results suggest that age-related changes in the noncalcified collagenous matrix induced by bone remodeling may have likely effects on bone quality.