Stem cells and broken bones

James Chan

Paw end

Knee end

Shin bone

This is where we break the bone

This is the broken bone.

Let’s have a look inside..

If you’re observant, you’ll notice the blue rod going down the shaft of the bone . This is the metal rod that we put in to keep the broken bits together, otherwise the leg will fall to pieces when the mouse tries to run on it!

• Imagine dropping red ink into a pool of water: the red gets less intense and less concentrated at the edge as it spreads.

• The same happens here: the chemical signals get less concentrated as you move away from the place of injury

• The fancy name for this is the ‘concentration gradient’.

Now, whenever the body gets injured, the injured bits (the bone in this case) releases loads of chemical signals (red).

When the stem cells detect these signals, they start moving towards the place of injury because that’s where the signals are most intense, so you can say that the cells move ‘up the concentration gradient’.

These chemical signals wake up the stem cells that are lying around inside the bone and in the muscles around it.

Muscle

Stem cell in bone

Stem cell in muscle

callus

Once the stem cells get to the place of injury, the strong signals there stop them from moving any more and turn into specialised bone-making cells.

So, these cells start making a lump of new bone, or what we call a ‘callus’.

This is where the fracture was..

But the bone is a lot cleverer than people think because it is able to remember what shape it is supposed to be.

So over time, it reshapes itself back to its original shape.

This is called ‘remodelling’.

So remember, the bone is not dead. Far from it, it is very much alive!

My group has now found a chemical signal we can inject into the broken mouse bone...

..and speed up healing!

Hopefully, this can help our patients get back upand running again in no time!

Our aim now is to get this to work in humans!

Thank you!

Hope you enjoyed it.