Stem Cells : What are they and why are they so awesome?

Source

'Stem cells' are talked about a lot, but what really are they?

Stem cells are unspecialised cells, capable of making the specialised cells that make up our body. At conception, just after fusion of sperm and egg, we exist as one cell. This cell divides in to 2 daughter cells, which in turn divide to become 4 cells, which become 8, 16, 32, 64 and so on, until we have a LOT of cells. But our cells aren't all the same - our arms are pretty different to our eyes! Why? Our cells differ from one another according to the particular proteins, such as growth factors, that they are exposed to during development. The type and quantity of these proteins defines the cell fate. Cells exposed to lots of 'Growth Factor A' and a little bit of 'Growth Factor B' become liver cells. Nearby cells which are exposed to less of 'Growth Factor A' and more of 'Growth Factor B' become pancreas cells. It's a little more complicated than that, but you get the picture. It's about gradients. The proteins are responsible for switching certain genes on and off. So even though our cells contain the same genes, the active genes are different. This is why there are very distinct differences between pancreas and liver, arm and eye. This process affects what we call the potency of cells. 

We begin as just one cell, capable of making every possible cell in our body. As this cell divides and develops, the variety of possibilities for what these daughter cells could become reduces. We refer to this as potency. Totipotent cells are able to differentiate into all possible cell types, pluripotent cells are able to differentiate into almost all cell types, multipotent cells are able to differentiate into a particular family of cells... and so it continues, until we are left with differentiated cells, such as our skin cells, which can only be themselves. This transition from totipotent cells to differentiated cells is one-way; it doesn't reverse. A key feature of stem cells is that, as well as producing differentiated daughter cells, they can produce more of themselves. This means that they can replenish the pool of stem cells available. 

So why are they so exciting?

Source

Babies have high populations of stem cells, which is why they are capable of incredible feats such as RE-GROWING FINGERS! The stem cells near the wound are able to divide and differente into the cells required to rebuild the finger. You can kind of think of them as an emergency response team, capable of rebuilding our bodies. As adults, we still have some stem cell populations in our body, which regenerate and replenish tissues. For example, our bone marrow contains stem cells capable of making bone, fat, cartilage and muscle cells for us. 

For a long time we have been extracting stem cells, either from embryos (which throws up a whole realm of ethical issues) or from adults. We can then do two pretty cool things with them. 

1. We can harvest particular stem cells from donors and transplant them into patients with life-threatening diseases, to replenish tissues. (This process is difficult and limited.)


We can, in theory, take stem cells and artificially induce the process of differentiation. Put simply, we could turn a stem cell in to any type of cell that we want. We could create cells of the eye or brain, insulin-producing cells, heart valves, you name it. These could be transplanted back in to compatible patients. We could cure blindness, Parkinsons, Alzheimers, diabetes, spinal chord injury, strokes and so much more. 

There are currently stem-cell trials underway for some conditions such as multiple sclerosis and degenerative eye diseases. It is important to realise that the transition from theory to reality can take decades, at least. But there may come a time when paralysis and some of these diseases are a thing of the past.

In theory, we can pretty much do anything with stem cells. Unfortunately reality throws a whole load of issues in the way to make things a little harder. But recently a few things have changed. Firstly we are learning more and more about development and using this knowledge to get better at differentiating cells in the lab. Secondly and VERY excitingly, a Japanese scientist, Shinya Yamanaka, was able to reverse the direction of development. He took a differentiated adult cell and changed which genes were switched on and off, turning it back in to a pluripotent stem cell. Or at least a cell that looks and acts an awful lot like a pluripotent stem cell. We call these induced pluripotent stem cells, or iPSCs. The science is still young, but just think... one day a person diagnosed with a degenerative brain disease could go to the doctor and undergo a harmless procedure to harvest some cells. These cells could be taken to the lab, turned in to IPSCs and then transformed into specialised healthy brain cells to be transplanted back in to the patient. Disease cured. No risk of rejection as the cells came from the patient. 

Another VERY exciting, VERY awesome advance in technology is 3D printing. Utilising stem cells for 3D printing could have some very exciting results. Imagine for a second, that instead of using different colours of ink, these printers used living ink - made up of different types of cell. In fact, you don't need to imagine, just watch this video...

This is only the beginning. We are now successfully printing windpipes and attempts are underway to print human organs. If you have 17 minutes, I recommend Anthony Atala's TED talk on printing a human kidney. His team are pioneers of tissue engineering and organ printing. 

I hope this has got you excited about regenerative medicine. I cannot wait to see what incredible advances there are over the next few decades. Stem cell treatments and regenerative medicine are just some examples of awe-inspiring scientific discoveries and their modern applications. So please share and spread the knowledge. By getting more people aware and excited about science, we can get more funding directed to these areas and inspire more bright young minds, from all backgrounds, to pursue science. 

If you have any questions or want to know more, feel free to comment below.