Changes in the Ratio of Non-Calcified Collagen to Calcified Collagen in Human Vertebrae with Advancing Age

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Abstract
Bone loss associated with aging is associated primarily with a decline in bone formation. To try and further understand the nature of this process we have used a biochemical approach which relies on the fact that osteoid is susceptible to enzymatic degradation whereas calcified collagen is protected by the mineral phase against proteolytic digestion. Our findings show a statistically significant inverse relationship between osteoid and age (r = 0.70 female, r = 0.47 male). A closer relationship was observed when age was related to the ratio of osteoid to bone (r = 0.73 female, r = 0.56 male). In both cases, the observed linear decline begins at an early age and becomes marked with advancing age. Histologic observations illustrate these findings showing decreased osteoid and osteoblasts in the older vertebral specimens compared to the younger ones. Even though the mechanism for osteoid calcification seems to remain unimpaired, the decline of a calcifiable matrix in the presence of normal bone turnover could lead to bone loss.