Planaria — a model for a future of regenerative medicine
Having two heads would surely help in everyday life, wouldn’t it? And although this sounds like a scenario from some science fiction book set hundreds or even thousands of years in the future it is something which is possible and has already been done.
Now, I must admit I overexaggerated a little bit. We still can’t grow another human head but that doesn’t mean Planaria (Turbellaria) can’t do it. Let me elaborate; Planaria are flatworms which can be found in many small streams and rivers or even in the soil across the whole world.
Now, what’s special about them is their incredible ability to regenerate, or put differently, regrow parts of their body. They are so good at this that it’s possible for them to fully regenerate all their tissue and organs from just 1/279 of their body. That would be like growing a whole person from just their pinky finger.
Their incredible regenerative ability stems from the enormous amount of stem cells in their body, which make up about 30% of it. Stem calls have the uncanny ability to become any other type of cell.
Normally, the cells which make up the muscle tissue, for example, can only become those same type of cells after division. Think of stem cells as a blank canvas, by dividing they can become a skin, blood, bone, or any other cell. They can even turn into cells which normally don’t divide such as nerve cells, and if we found ways to use those principles in the human body it would be possible to achieve things like restore eyesight!
Therefore, it is important to understand stem cells and regeneration in general and the mechanisms which govern it. As such, many scientists are conducting research which is focused precisely on regeneration and although we have yet to completely understand regeneration and what factors influence it in recent years it has been shown that bioelectricity plays a large part in it.
Namely, bioelectricity is something which can be found in any organism and is a result of the difference in the concentration of charge at the cellular level. Every cell has a certain degree of electrical polarity caused by different ions in the membrane and cytoplasm such as Na+ or K+ and the difference in concentration of those ions results in bioelectricity. This phenomenon is essential in regulating loads of biological processes among which are healing and regeneration.
By now you must be asking yourselves, how is this connected to being able to grow two heads. Well, scientist found out that by changing bioelectricity in Planaria which are undergoing regeneration they end up with Planaria which regenerate two heads!
They can do this in a number of ways such as using a different electrical field or simply adding the regenerating trunks of Planaria in a solution of octanol, an alcohol with 8 C atoms. This in turn blocks communication among cells using those same ions mentioned earlier which are transported through different channels, the most important of which, in the case of Planaria, is GJC — gap junction communication. Think of those channels as roads and ions as cars, normally everything goes smoothly, people get where they need to be, cars shift from one lane to the other etc. and using octanol would be like putting a barrier in the middle of the road which would block people from reaching their destinations. Using those same methods, they were able to regenerate Planaria with two tails, Planaria with 4 heads, and Planaria with heads of a different species than they started with!
Now, I know this all sounds crazy and impossible, but it just goes to show you how amazing science is and how thigs which we now think of as impossible could very well be real in a couple of years, or even already are somewhere in a lab in some petri dish. ;)