Bone tissue is constantly remodeled, broken down by osteoclasts and built up by osteoblasts. With age the balance of activity between these two cell populations shifts to favor osteoclasts. The result is ever weaker and more brittle bones, the condition known as osteoporosis. Numerous mechanisms may contribute to this cellular imbalance, with the signaling of senescent cells clearly implicated on the basis of recent evidence. The open access paper noted here looks another of the possible contributions, the aging of mesenchymal stem cells in the bone marrow.
Aging is a gradual process that results in a loss of tissue homeostasis, driving a progressive deterioration of tissue and organ functions mainly due to cellular damage accumulated throughout life. The human skeleton is especially affected by the passage of time: bone loss begins as early as the third decade of life, immediately after peak bone mass. In humans, bone is a highly active tissue which undergoes continuous self-regeneration throughout adulthood to maintain structural integrity in a process called bone remodeling. It has been estimated that the entire skeleton is remodeled every 10 years.
Throughout young adulthood more bone is formed than is resorbed, resulting
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