Why Is Osteoporosis Prevalent in Certain Bones?

New Research Points to Overwhelming Differences in Limb and Skull Bones

Differences in bone types may explain why the limbs are less resistant to thinning than the skull, according to new findings that researchers suggest could aid in the continued understanding and treatment of osteoporosis.

As detailed in a new study recently published in the open access journal PLoS ONE, researchers compared the cells of skull and limb bones taken from adult rats, finding approximately 1,236 genetic differences between these bones.

Based on the study’s findings, skull and limb bones have differences in bone matrix characteristics, leading to different densities of bone-forming cells, or osteoblasts, and thus possibly explaining why bone thinning occurs in the limbs (arms and legs) with aging but not the skull.

For some more context, bone formation is a dynamic, remodeling process that involves bone being laid down by osteoblasts and removed by bone-eating cells called osteocytes. Typically, more bone is created than removed early in life; however, this process changes around age 30, with more bone removed than replaced.

Osteoporosis is a thinning of the bones that typically occurs in women greater than 50 as a result of decreased estrogen levels and the favoring of osteocytes, leaving limb bones and spinal vertebrae susceptible to fracture.

According to the study's researchers, the differences between skull and limb bones are profound at the levels of the organs, cells and transcriptomes, suggesting that such variances occur early in life, probably when these bones are still developing in the womb.

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