Using Photosynthesis Inside Animal Cell Is No Longer Science Fiction

[00:00:00]How wonderful person, this is Anton, and today we're going to be discussing some of the recent research that tries to bridge two separate kingdoms of life, animals and plants. Two kingdoms we usually think of as completely separate, but that some of the recent research essentially tried to kind of combine.

[00:00:18]And that's because for a very long time, there was always this fascinating idea of having some kind of an animal that's able to harness the power of the sun. In other words, just like a leaf, researchers were wondering if an animal can also photosynthesize and thus potentially have certain benefits that would otherwise not exist. And so based on some of the recent studies you can find in the description and studies in synthetic biology, we now are technically moving much closer to making a photosynthetic animal a kind of a reality, but not for the sake of basically not eating anymore or essentially having some kind of a green skin animal, but instead because it seems to have very beneficial biomedical potentials. In there is actually a way to treat certain things using photosynthetic reactions. And so let's talk about these studies in a bit more detail, but first I guess something that you might have been aware of before because if you have been following science news enough, you might have seen something like this before, Elysia chlorotica, the green sea slug, something that nature has already actually created. And this is a phenomenon we've known about for several decades, kleptoplasty, a phenomenon that occurs in certain species of sacoglossan sea slugs, which literally steal chloroplasts, the tiny green engines that plants use for photosynthesis, from all of the algae they eat. In other words, they're able to sort of capture them into their own cells. But for a very long time, scientists debated whether these stolen organelles, or these kleptoplasts as they're technically known, were actually doing anything useful besides just acting up as some kind of a backup food source.

[00:01:57]And so, it wasn't until 2021 that researchers finally confirmed that these were not just for storage, but were indeed fixing carbon with the resulting molecules then actively sent to these slugs' reproductive organs for energy.

[00:02:11]And so, while these slugs are not entirely solar-powered in the sense [music] that they would be able to live on light alone, here the photosynthesis seems to give them some kind of a clear biological advantage, very likely helping them survive periods of starvation, but most importantly boosting their reproductive fitness. And so, this was actually a pretty interesting discovery. So, basically, it makes these slugs a little bit more tolerant of starvation compared to their cousins. But, the thing is, when it comes to more complex cells, and especially mammalian cells, there's always been this major challenge. And that's because our cells are much more complex, and frankly, are also quite hostile to anything foreign. So, basically, if you try to put some kind of a plant organelle into a human cell, the cell's defense system, and especially organelles referred to as lysosomes, would very likely destroy it completely, essentially treating it as some kind of a pathogen. And so, no foreign organelles would be able to survive inside a human cell for more than 48 hours. And on top of this, both chloroplasts and mitochondria also have their own genomes. That's because they actually used to be various bacteria back in the days, but still rely on the cell's nucleus to provide the majority of proteins they need to function. And while compared to these slugs, and also compared to most plants, the nucleus of an animal cell has no instructions on how to maintain a typical chloroplast.

[00:03:37]In other words, even if we were to somehow inject them into a typical mammalian cell, they would very likely just starve and eventually get destroyed, which is why this somewhat recent study from 2024 is actually very significant. This is a study by Ryota Aoki and Atsushi Miyoshi here. And this team from University of Tokyo did not just look at sea slugs, they actually found a successful way to incorporate photosynthetically active chloroplasts into various cultured mammalian cells.

[00:04:07]In other words, cells that were actually raised in a lab, but they were still extremely similar to what we have. And specifically, they used the cells from what's known as a Chinese hamster, and actually from the Chinese hamster's ovary. And introduced chloroplasts from a primitive algae referred to as Cyanidoson Merolae. This is a type of a red algae very often found in relatively hot acidic environments. And while this algae was specifically chosen because it lives in these extreme environments, meaning that its chloroplasts are going to be incredibly robust and basically somewhat difficult to destroy. And so here, researchers first found that these chloroplasts were not just passive passengers, but maintained their electron transport activity themselves.

[00:04:51]This is one of the main mechanisms in photosynthesis. And importantly, when these cells were mixed, or basically when the chloroplasts were injected into the mammalian cells, they were actually able to do all of this inside the mammalian cell for at least two days, with the animal cells surprisingly even showing an increased growth rate during this period. Sort of suggesting that they might have been using some of the products produced by these chloroplasts as a direct carbon source. But interestingly, not all of these ovary cells accepted the chloroplasts. Only about 20% incorporated one to maybe three chloroplasts, and only 1% were chloroplast-rich containing 7 to 45 of them. But once incorporated, they were then found within intracellular vesicles, and seemed to be localized extremely close to the nucleus, very similar to how it's usually done inside plants. And so during this two-day period, they actually seemed to help these cells to become just a little bit better. With the study providing the first ever evidence that chloroplasts can survive inside a mammalian cell for at least 2 days. But obviously, if they can survive longer, that's a question we cannot answer yet. Although most likely no, because they'll still get destroyed.

[00:06:05]With the chloroplasts showing signs of structural and even functional degradation by the fourth day.

[00:06:10]Nevertheless, this is a direct demonstration that it's possible to introduce functional photosynthetic genetic organelles even into mammalian cells. With the implications from this now actually being recreated in a different study. Okay, so I guess this is the next question. Why even do this?

[00:06:26]Especially since it doesn't seem to work very well. And that's because the future application could be what's known as a photosynthetic therapy. In other words, we're not trying to create something like this, but instead are trying to find a way to use this to possibly treat various disorders. And now in 2026, we have our first proof that it does seem to work. And so here in this recent study that was published in the journal Cell, researchers applied this to the organ inside of us that always receives light. Here the application involved the eyes. And that's obviously because our eyes are naturally exposed to light, making them perfect candidates for this kind of technology. And so here scientists developed what's known as Leaf, a light reaction enriched thylakoid and ADP H foundry, which is a very fancy way of saying a photosynthetic medicine. And essentially here they took the machinery of photosynthesis out of spinach leaves, and especially the thylakoid grana. This is actually where the first steps of photosynthesis usually happen, and then turn them into a kind of a nano scale delivery system. And well, then they took this and injected it into eyes of mice. Specifically mice with what's known as a dry eye disease. And here this particular disease can be actually pretty serious. It's not just about lacking tears, it's a condition involving chronic inflammation and a lot of oxidative stress where the body produces way too many harmful molecules referred to as reactive oxygen species.

[00:07:57]And so, it's a condition where eyes become inflamed extremely quickly. And well, just like humans, mice suffer from this as well. And normally, our cells use a molecule called NADPH to fight all of the stress. But under diseased conditions, our natural supply runs out and the eyes become very inflamed. And so, here this leaf system basically uses a lot of ambient light to then photosynthesize a fresh supply of NADPH and ATP, or basically the fuel of the cell, but in this case, directly inside the eye cells. And so, in these mouse trials, after just 5 days, by using these photosynthetic eye drops, or basically eye drops containing these spinach leaf extract, seem to be just as effective as some of the more expensive commercial medications that are often used to treat this problem. And in this case, it dramatically reduced cornea damage and restored tear production for all of the mice. In other words, we have our first official proof that photosynthetic medicine can indeed work and can be applied to mammalian cells and thus be used by humans. Although in this case, the benefit obviously goes way beyond the eye. With other researchers also testing similar systems to even treat inflammation from arthritis inside the knees. And so, here they actually applied this to the mouse knees and well, it seems to kind of work. There's even talk about using algae or thylakoid membranes to provide this green oxygen to the human brain during medical emergencies or to power the heart tissue that might have been damaged by a lack of blood flow. In other words, by injecting certain mixtures involving these photosynthetic cells, we might be able to provide oxygen to various tissues where oxygen is deprived. But I also need to emphasize that all of this is extremely early research, and we're obviously not at the point where we're going to have photosynthetic humans anytime soon.

[00:09:51]There are still quite a lot of different challenges, and this might take decades before it becomes useful. And so once again, because of the nuclear problem, or basically because the animal cell nucleus cannot maintain chloroplasts inside their cell, and because our cells are generally very hostile to various foreign invaders, a lot of these challenges will still be extremely difficult to overcome. And so, where does all of this leave us? Well, as of 2026, we're now in a kind of a transition stage from observation biology, or basically studying these slugs, to synthetic bioengineering, where we're now applying some of these strategies to try to create new medical solutions. And while we're still learning how to have these new organelles survive inside of us, scientists have already found a few strategies that basically seem to work.

[00:10:37]And although right now we only have two studies using the spinach leaves and the red algae organelles, this is definitely an interesting step forward. In other words, one day we might be able to use the light not just to obviously see, but to also heal, and maybe even for energy.

[00:10:53]So there's actually quite a lot of potential that one day this might provide various solutions for 1.5 billion people suffering from various kinds of eye disease, or to even help us rescue various organs, even, for example, the brain, where the oxygen has to be delivered extremely quickly. But at least for now, that's all I have.

[00:11:11]This is definitely an area of science that's going to be moving pretty fast, so we'll definitely come back and discuss this more once there are some updates. Until then, thank you for watching, subscribe, come back tomorrow to learn something else. Support this channel on Patreon, where you can find additional videos, videos without any ads, and can DM me directly, or by joining our channel membership, which grants you early access. You can also support this channel by buying one of our present t-shirts in the description below. Stay wonderful. I'll see you tomorrow. And as always, bye-bye.