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Regeneration, the process of growing back entire organs or body parts, isn't a concept that was made up by Dr Who - our own bodies have the capability of doing it! Our bodies are made up of millions of tiny building blocks called cells - there are hundreds of types of cells and each type of cell has a different function that, together, make a living, breathing person! The apparent super-power of regeneration originates by a special type of cell called the stem cell. These cells have the power to change (or differentiate) into any type of cell that may make up our bodies.
What Are Stem Cells?
When your mum was pregnant with you, your stem cells were working overtime to make your baby body. We all start life as one single stem cell; it grows and multiplies to make you. However, we have many different types of cells in our bodies, they all originate from that stem cell. That cell differentiates into more stem cells that are slightly more specific, then those cells differentiate into more cells that are more specific, and the process continues until you have the hundreds of different types of cells that your body needs. However, the more specific the cell is, the less power it has to differentiate into other cells, therefore after a while cells stop being called stem cells and are called specialised cells. This is because they've completed changing into other cells. Once a cell changes or differentiates fully - they can't change back. Because we have to do so much differentiation when we are growing into a baby, our bodies don't have many stem cells left in them.
How Do Stem Cells Work?
Stem cells are very powerful cells, so naturally it's quite complicated how they work...
Aside from cells, there are many chemicals in our bodies that keep our bodies working as they should. Some of these chemicals act on stem cells to tell them which cells to change into. These chemicals have different names - the one that we use when we are growing our baby bodies is called Stem Cell Factor (SCF). It binds to our stem cells and tells them what to do. Different chemicals tell stem cells to change in to different types of cells.
Have you ever got a cut or a graze from falling over? You'll know that your skin grows back after some time. That's because there are stem cells just under your skin, and when you cut yourself - those cells get told to grow new skin.
In fact, we actually replace all of our skin every day! This is because newer cells are more powerful. You body is constantly recycling your skin, using stem cells, so that your skin stays healthy.
Why Don't We Use Stem Cells to Help People Grow Back Arms or Legs?
You may know someone who is missing an arm or a leg, or maybe some other body part - like a kidney. Why do you think people can't just grow those body parts back?
Remember how I said that we don't have many stem cells left after we are born? That's why.
We don't have stem cells in the right places (or enough of them) in order to grow back whole body parts. That's why we can only grow back simple things like skin.
Using Stem Cells in Medicine
Just because our bodies can't use stem cells to grow back body parts yet doesn't mean scientists aren't going to try and make it possible! In 2006 Japanese scientist Shinya Yamanaka managed to take cells out of mice (and later people) and change the specialised cells back into stem cells! This meant that those cells were free to differentiate into a number of different cells. He did this by dumping a massive collection of chemicals, called transcription factors, on the cells. Yamanaka won the Nobel prize for medicine for this in 2012. We can then use these stem cells to make the cells we need to regrow certain tissues (clumps of cells that make up body parts) in labs; we then implant these tissues into people.
However, today, only a handful of stem cell therapies exist - they focus on blood disorders or for treating bad burns. This is because the newly grown stem cells, and the cells that they then specialise into, struggle to integrate or become part of our bodies once they are put inside us from the lab.
There is a new movement in stem cell science to try and directly change cells into stem cells inside our bodies, this is very very complex but, if it works, it would solve the problems of tissues not integrating into our bodies.
What uses of stem cells can you think of?
How would you solve the problems that we currently face?
Get in touch with your questions and your comments!
