A scar is born

Our body is constantly making new cells and tissues to replace those damaged by ageing or an injury; often the repair process isn’t perfect and leaves a scar. And most of the people you meet in the street have one and a story to go with it. Georgia Mills spoke to Matt Hardman, of the University of Hull, to find out how scars form...

Matt - Well, like any biological process it's actually quite complicated. So the first thing that happens is platelets in your blood clot together to form a clot - that stops you bleeding to death. Then immune cells are recruited from your circulation to the sites of injury. And their job is to get rid of any debris or get rid of any bacteria that are in the wound that shouldn't be there, and then stem cells become activated locally and they replace the cells that are missing in the void. And the key thing is that void has to be filled with matrix, a matrix is kind of like a biological polyfiller. And the way that that is sculpted is what causes the scar.

Georgia -  is that kind of a scaffold across the hole in your finger trying to bridge the gap? And what is that made of?

Matt -  So it's made of all kinds of different components essentially long proteins that bind together in kind of a mesh work and that mesh work is what restores the function of the tissue. The key thing is a scar is actually quite different to normal skin.

Georgia - Why is that why don't we get a lovely new fresh finger again. Why does it leave a scar.

Matt - It's evolutionarily programmed so we've developed over thousands of years to actually heal in in a dirty environment. So we have to heal rapidly and quickly and close that wound. But actually these days most injuries happen deliberately in operating theatres. And so that's a much cleaner environment so you don't necessarily need to heal so quickly and with such a prominent scar.

Georgia - Right. So it's because we're we're trying to heal so quickly that it is like different from our usual skin.

Matt -  Yeah. And the immune cells themselves actually drive the scarring process so if you have a really exuberant immune response that releases loads of factors which actually activate the scarring response.

Georgia - So why does the tissue look a different color as well?

Matt - So scars are completely different to normal skin: they like hair follicles, they lack sweat glands and they also tend to be less pigmented.

Georgia - It doesn't happen all the time does it. We don't always scar. So why does it happen sometimes and not others?

Matt -  Essentially the depth of the wound decides whether you're gonna scar or not, if you have a very superficial wound like a paper cut that's not going to scar. If you have a full thickness wound all the way through the skin then you're gonna end up with a scar.

Georgia- And yet the paper cut hurts more.

Matt - Yeah exactly. It is interesting that not everyone scars the same. And actually the way you scar changes over your lifetime.

Georgia -  How so?

Matt -  I'm sure you want to realize that younger people tend to heal faster but also with less scarring but also older people don't have such exuberant scarring mainly because their immune response is dampened so as you get older your immune cells lose a lot of their ability. And that means that your wounds heal less quickly but also with a better quality of scarring.

Georgia - That's really interesting. So it slows down and that means it doesn't scar so much. Could we trick younger people into doing that too to avoid scarring?

Matt - Yeah but the danger there is that then you'd move onto a wound that wouldn't heal. So it's a fine balance you don't want to delay wound healing too much because then you could end up with a much more serious problems.

Georgia - I see you could get infected and then you'll look great but you'll be about to die.

Matt - Yeah.

Georgia -  What about you mentioned younger people don't scar so much what about in the womb?

Matt - Yes so that's really interesting. So actually whereas most mammals do scar quite a lot. Most mammals when they're in the womb don't scar. So there's there are changes biological changes that occur at the point of birth that lead to scarring and it's thought that it is mainly the immune system. So when you're in the womb you have a less developed immune system.

Georgia - And I've heard that some animals don't actually scar at all, like a fish. Is this true and how are they doing it?

Matt - Yes. So flies worms fish even some lizards don't scar and they can actually regenerate whole limbs. And the answer is we don't really know why those less developed organisms are able to heal them regenerate whereas with humans aren't.

Georgia - that sounds really handy. I mean being like a regular Wolverine I mean could we could we find out what they're doing and then apply it to us, do you think?

Matt -  Yes absolutely. And there are lots of groups around the world who are actually looking at understanding regenerative healing and in less developed animals to be able to implement that in a human's.

Georgia - That sounds great. And finally this is something everyone who's ever had a skull will know. Why do they itch?

Matt -  So the nerves in your skin are actually stimulated by the cells that are healing a wound. So as they're moving around as they're releasing chemicals that stimulates your nerves but actually the nerves themselves are regenerating. So within the tissue there are underdeveloped nerves and they're sending out kind of scrambled signals to your brain which are sensed as itch.