Anosteocytic tilapia bones rebuild

Abstract

We tend to take our bones for granted: they are constantly modified in response to use and their remarkable ability to repair damage is really only apparent after a painful break. But spare a thought for other less fortunate animals that lack the specialised cells, osteocytes, that are essential for bone rebuilding. Ron Shahar from The Hebrew University of Jerusalem explains that osteocytes detect when a bone is experiencing a mechanical load and trigger the adaptation that strengthens it in response to changes in use. However, he and his team explain that many fish lack these essential cells, posing the question whether fish bones can be modified at all and if so, how do they sense the mechanical loads that trigger the alteration?Inserting two screws into the bony opercula (gill cover) of tilapia and linking them with a spring – to pull the screws together and mechanically load the bone – Ayelet Atkins monitored how the bone responded over 50 days. She found that the bone between the spring-loaded screws dramatically altered structure, showing evidence of high numbers of bone-altering osteoblasts and osteoclasts that accompanied bone resorption and deposition in the vicinity of the spring, which resulted in a stiffer region of bone that also changed its shape.‘We show that the bone of the anosteocytic tilapia is able to adapt to applied loads, despite the complete absence of osteocytes’, says Shahar and his team suggests that osteoblasts could be the cells that detect mechanical loading in fish bones that lack osteocytes.