Photosynthesising algae inside living brains

Biomedical researchers often want to keep animal organs alive outside of the body to study them, just like how you’d keep an organ transplant alive before it goes into a patient. But those organs need oxygen to survive. Right now, the solution is to keep the organ in a bath with bubbles of oxygen. But a team at LMU Munich have another solution that sounds like it’s come straight out of science fiction. To keep their tadpole brains alive long enough to study how the nervous system works, they’ve injected algae cells into the blood vessels in the brain. When illuminated, the algae produce oxygen, which is fed directly to the surrounding brain cells, as Sally Le Page heard from Hans Straka...

Hans - The brain of all animals need an awful large amount of oxygen. Now, what we were interested is how can we actually understand how much energy a brain needs to perform its function? And our idea was why not directly use the oxygen, which is produced by plants and recruit it to provide the energy for the functional brain. Of course, we cannot plant the tree into the brain. So we had to go to a smaller version, which are algae. Algae are green plants at a single cell level. So these algae produce oxygen, just like a tree produces oxygen. Now, by inserting these algae into the brain, we thought we would have the capacity to directly produce the oxygen inside the brain, which can then be recruited by all the nerve cells in the brain.

Sally - So the air that I breathe, obviously I need oxygen to survive, the oxygen comes from trees and algae anyway, and you're like, why don't we short circuit that, why don't we cut out the middleman and just stick the photosynthesis right next to where the oxygen is being used?

Hans  - Exactly. That was the basic idea because it's faster. In our study, we injected algae into the blood vessels of a tadpole. We are working on these animals after euthanizing them and isolating the brain from these animals. And afterwards measured the production of oxygen upon illumination of the tissue.

Sally - You've got these tadpole brain tissues. You've got them floating around in this little bubble bath of nutrients, oxygen, and now you've inserted algae into their brains. What happened?

Hans - As soon as you turn on the light and shine the light on the tissue, the algae you start to produce your oxygen to such an amount that you all of a sudden can measure a considerable amount of oxygen, even inside the brain. Now, when you turn off the light, it goes down to zero again, because first the algae don't produce oxygen anymore, and the brain is starting to consume all the oxygen that the algae have produced actually.

Sally - And does that mean that if you wanted to, you could turn the light up and down on a demo switch and really fine tune control how much oxygen the brain is getting?

Hans - Exactly. That is what we, what we so to speak have done because we have repeatedly turned the light on and off and saw that the nerve cells start firing. And then they stopped firing when we shut down the light and then restart the firing, when we turn on the light. So we could really drive the brain activity by shining a particular amount of light.

Sally - And now we know it's theoretically possible. In the distant future, looking through your crystal ball, can you imagine human treatments where we might start injecting algae into humans to increase oxygen in parts of their bodies?

Hans - In theory, I could imagine something like that, but I mean, I could imagine a lot of things on the long run, as you have been used together with fibroblasts to heal skin wounds, because the oxygen which the algae produce actually helps closing the wounds. So on the external surface, this is already employed. Well, why not employing it internally as well.