Have you heard that our body is mainly composed of 70% water? Although true, the percentage varies from 55% of water in adult women, all the way up to 78% in babies, with the percentage for adult men somewhere in between. This is also true for animals, where some — like the jellyfish — have even 90% of their body composed of water. With this in mind, why don’t animals, including us, look like a soup? How can animals have a defined 3D structure?

Aurelia aurita, moon jellyfish, 5 preserved specimens (C193)

Animals are made out of cells, the building blocks of our organs and tissues. But cells are basically a bag of water and chemicals; so again, why don’t animals look like giant bags of chemicals? The most obvious reason is that animals have bones that give structure to the rest of the body. But even bones are 31% water, and organs with no bones, such as hearts, still have a unique 3D form. Hearts have defined chambers (see the elephant heart below); they’re not just a mush of cells. The answer lies not in the cells themselves but in what surrounds them.

Elephant dried heart (Z639)

Cells are engulfed by the extracellular matrix (ECM) which is mainly composed of proteins. This matrix encompasses the space in-between cells, gives them structural support and acts like a scaffold. It can also act as a pathway for cells to migrate along and it gives out chemical and physical cues that cells respond to. The ECM varies from organ to organ. The brain, for example, is mainly composed of cells with an ECM of only 20% of the total mass. In contrast, cartilage has fewer cells and around 70% of its mass is ECM. Every cell type is surrounded by a specific matrix that will affect its function. Studying this extracellular environment is important to understand how cells develop, how they interact with each other, and how they react to disease.

At the same time, by studying the ECM, researchers can get an idea of how an organ or tissue is structured and how to replicate its intricate architecture. Scientists that work in tissue engineering use a technique which consists of washing away the cells of an organ, literally. By using detergents, the cells are washed away in cycles until just the extracellular matrix is left. In this manner, they can analyse its composition and experiment with the matrix with the end goal of growing an organ in the lab. Therefore, one day we could replace diseased or aged organs with new ones without the need for transplantation. The unique composition of the ECM provides cells with the support they need to survive, and at the same time, gives animals and their organs a defined 3D structure.

Sources:

https://water.usgs.gov/edu/propertyyou.html

While working at the Grant museum of Zoology the other day, I encountered a lovely group of teenagers that started asking me questions about the museum. As we engagers do, I automatically started talking about my PhD project. I told them that I was working with stems cells and trying to build a neural tissue in the lab, to which they replied with a tilt of the head in sign of confusion. So I inevitably had to change my explanation and told them that I was trying to build a tiny part of a brain in the lab.

With a change of head tilting they replied with “Uh, that sounds cool” and “Are you going to create a Frankenstein?” To which I, being the bubble buster that I am, had to reply with, “Well, actually, Frankenstein was the scientist that created the monster”. So no, I am not going to create a scientist, or a monster, or a brain. I could see a tiny deception in their faces, so explained that neural tissue doesn’t necessarily mean that I’m building an entire brain, although it would be helpful to have two brains instead of one, especially when writing a thesis!!! But no, scientists have not been able to grow a full size brain. The closest that scientists have come, has been to grow a group of brain cells that self-assembled into an “organoid” that resembles some structures of a brain.

So how is that different from a brain? Good question, I am glad you asked avid reader. Even though the cells scientists have grown have developed into different kinds of brain cells and had some neural activity, the maturation and differentiation of different brain areas was not complete. The connections and systems that make us see or hear or control our movements were not there.

It is not enough to have brain cells arranged together; the information that runs through neurons has to have specific highways and an overall order in the soup of chemicals and cells that is our brain. Besides all the intricate and delicate organization cells need to have, they also need nutrients and oxygen or in other words, blood vessels, little tiny ones and big chunky ones, to reach every cell so that they can survive and function. Yes, there are interesting advances into knowing how the brain works and how cells develop into a brain, but we are not there yet.

So the answer to “Can we build a brain in the lab?” is no, not right now. So contrary to what may have been on the news, lets just say that we can grow brain cells and keep them alive; we can make them interact with each other and grow groups that self-assemble, but we are years away from actually growing a fully functional brain. And in order to have a ”functioning” brain it would need to have eyes and ears and muscles and all of the systems that connect to it (basically a body) in order to be functional. Otherwise it would not have any input and would not be able to process information.

Many of the guys that I was talking to in the museum where relieved when I explained this to them, fearing that maybe science has come too far. Has it? I don’t know, but I will leave you with this question: Do you think it would be a good idea to build a brain in a lab?

Infographic from livescience.com: