Irish scientists have discovered why movement of embryos inside the womb is so important for the development of strong joints and bones.

The researchers at Trinity College Dublin, working with colleagues in India, have for the first time unlocked the molecular mechanism that leads to cartilage rather than bone being produced in joints in a developing embryo.

They found that key molecular interactions are sparked by the movement, guiding the cells and tissues of the embryo to build a robust but malleable skeleton.

The discovery could be important for understanding of certain illnesses that lead to the fusing of bone, as well as treatments for conditions like osteoarthritis and cartilage injuries.

"Our new findings show that in the absence of embryonic movement the cells that should form articular cartilage receive incorrect molecular signals, where one type of signal is lost while another inappropriate signal is activated in its place," said Paula Murphy, Professor in Zoology at Trinity College Dublin.

"In short, the cells receive the signal that says 'make bone' when they should receive the signal that says 'make cartilage'." 

Scientist were previously aware that early embryonic cells receive biological signals that direct them to contribute to different types of tissue in different places.

One example in the early embryo is that cells are directed to decide whether to make bone or cartilage around articulating joints.

Until now little was known about the cartilage cell trigger and this has made it difficult to formulate effective treatments and repairs for many related conditions.

But now the research team has discovered that when embryonic movement is not present, the cells that should form cartilage in the joints receive an incorrect molecular signal.

This leads to the activation instead of the mechanism for making bone.

The team now plans to attempt to activate the correct signals for cartilage formation by exposing cells to varying combinations of biological and biophysical signals, as well as testing to see what movements are needed to trigger the correct mechanism.

 The research is published in the journal Development.