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The balancing actions of osteoblasts and osteoclasts in bone metabolism are well known. But the signals that stimulate and repress activity in these cells are understood only poorly.
A team from the University of Texas reported that, in mice, a particular microRNA (miR), miR-34a, inhibits the action of osteoclasts and (to a lesser degree) stimulates the action of osteoblasts. Mice in which miR-34a is knocked out have markedly low bone mass. Conversely, mice engineered to overexpress miR-34a have the following characteristics:
They exhibit high bone mass.
They are less likely than control mice to develop osteoporosis after ovariectomy.
They experience fewer bony metastases after inoculation with a mouse melanoma cell line or a human breast cance…