“I would like to know why organs like your liver and brain can regenerate while others can’t?” – Maggie, age 9, Melbourne

This is a great question Maggie. Scientists have actually been trying to answer this question for a long time. The good news is after many years of research we now have a good idea of how this works.

What are cells?

As you may know, the body is made of cells. We sometimes call these cells “the building blocks of life”. Nature builds all the parts of our bodies with cells.

In other words, you might have played with Lego before. Cells are like pieces of Lego! Just like Lego blocks do, cells come in lots of shapes and colours. Cells can also do lots of different things.

Your skin is made of different cells. Some of them make your hair, and some make your scars when you get a cut, for example.

Even your blood is made of many different cells. The red blood cells give your blood its red colour.

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So going back to your question, some cells in our body are very special because they can multiply. Not only that, these special cells can turn into other cells as well. The name of these special cells is “stem cells”, and they are the key to our organs regenerating.

Imagine if your Lego blocks could do that!

Which organs can regenerate themselves?

Maggie, you’re very clever at nine to know what “regeneration” means, but in case some other young readers don’t, regeneration is when our organs fix themselves after they’ve been damaged. Our organs might have been damaged if we get injured or we’re very sick.

Organs like our skin (yes, the skin is the biggest organ of the body!) need to regenerate often. The skin’s stem cells produce new cells when the old ones are lost, like when we get a paper cut.

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Our livers are very good at regenerating themselves because they too can make new cells. The cells of the liver are called “hepatocytes”. Hepatocytes start to multiply when the liver is damaged. So hepatocytes work like stem cells.

Intestines are another good example of an organ which regenerates itself. Our intestines regenerate all the time, even when we’re healthy. They lose cells when we digest food, but the stem cells in the intestines multiply to keep this important organ working well.

Which organs aren’t very good at regenerating?

The brain actually can’t regenerate itself well because when the brain is damaged its cells find it harder to make new ones. This is because the brain has very few of the special cells, or stem cells.

In recent years, we’ve found some areas of the brain can regenerate. But we still need to do more research to better understand how this works.

We do know the brain is better at regenerating itself when we are young than when we are old.

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Jose Polo is a founder of Mogrify. He is an ARC future fellow and receives funding from the NHMRC.