A View of Aging Bone
The aging of bone stems in part from the wear and tear of a very old cell population, according to this paper: "The adverse effects of aging of other organs (ovaries at menopause) on the skeleton are well known, but ironically little is known of skeletal aging itself. Evidence indicates that age-related changes, such as oxidative stress, are fundamental mechanisms of the decline of bone mass and strength. Unlike the short-lived osteoclasts and osteoblasts, osteocytes - former osteoblasts entombed in the mineralized matrix - live as long as 50 years, and their death is dependent on skeletal age. Osteocyte death is a major contributor to the decline of bone strength with age, and the likely mechanisms are oxidative stress, autophagy failure and nuclear pore "leakiness". Unraveling these mechanisms should improve understanding of the age-related increase in fractures and suggest novel targets for its prevention." The accumulating damage suffered by long-lived cell populations that are not replaced is an issue in many parts of the body, especially the nervous system.