Osteoporosis-;weakening of the bones with age-;affects millions worldwide, and this figure is increasing annually as the global population ages. It is associated with the aging, or 'senescence', of bone cells, but the underlying cell types and mechanisms were unclear. Now, however, a research team from Osaka University has identified a key osteoporosis-related gene, Men1 , and developed a new animal model of this disease.
Bones contain cells called osteoblasts and osteoclasts. Osteoclasts break down old bone tissue in a process called 'resorption', allowing it to be replaced with new healthy bone made by osteoblasts. Osteoporosis can result when the breakdown of the old bone occurs at a rate faster than formation of the new bone.
Cellular senescence of osteoblasts, reducing their efficiency, might be a reason underlying this imbalance. A gene called Men1 is linked to a genetic condition known as MEN1, causing benign tumors and associated with both cellular senescence and the development of osteoporosis early in life. The team investigated the role of Men1 in age-related osteoporosis and found that elderly mice showed both reduced levels of Men1 and increased activity of senescence-related genes in osteoblasts.
They then generated a mouse model where Men1 could be inactivated specifically in osteoblasts. The bones of these mice resembled the fragile bones seen in elderly humans. "The osteoblasts showed reduced bone formation activity, and accelerated cellular senescence throug.