Work your bones, get more bone. The link between exercise and bone density has been recognized for a long time. It works like this: As you work out, your muscles pull on your bones, causing strain. Cells embedded in the structure of your bones called osteocytes sense the strain and put out a call to other bone cells, osteoblasts, to start churning out proteins and minerals that make your bones denser and stronger. Which is why a history of load- or weight-bearing exercise can help prevent osteoporosis.

What if we could awaken osteocytes artificially, helping adults and children with brittle bone diseases make more of the bone they need? Scientists may be closing in on a way to do this, using a gene called Lrp5 that plays a key role in passing along the biochemical signals that translate strain into bone. …