Breakthrough As Scientists Make Animal Cells Photosynthesize
In a world first that challenges what we thought we knew about biology, scientists have successfully engineered animal cells that can photosynthesize. The breakthrough promises to revolutionize medical research and scale up the production of lab-grown meat.Photosynthesis is a biochemical process that plants, algae and certain bacteria use to turn light energy from the sun into food. The process—which occurs in special cellular structures called chloroplasts—uses up water and carbon dioxide and produces oxygen, as well as sugars that can be used by the plant.”All living organisms on the Earth, including humans, are able to live thanks to photosynthesis,” Sachihiro Matsunaga, Professor at the Laboratory of Integrated Biology at the University of Tokyo who led the research, told Newsweek. “Animal cells consume oxygen, eat and break down sugars, and emit carbon dioxide. This reaction is completely opposite to photosynthesis.”Scientists have been trying to make photosynthesis happen in animals since the 1970s.
An image shows chloroplasts (magenta colored) successfully incorporated into animal cells for the first time. In a world first scientists have successfully engineered animal cells that can photosynthesize.
An image shows chloroplasts (magenta colored) successfully incorporated into animal cells for the first time. In a world first scientists have successfully engineered animal cells that can photosynthesize.
R. Aoki, Y. Inui, Y. Okabe et al. 2024/ Proceedings of the Japan Academy, Series B
“If we can get even part of photosynthesis to occur in animal cells, we can reduce the amount of oxygen consumed, reduce the amount of sugar eaten, and reduce carbon dioxide emissions,” Matsunaga said.However, inserting these chloroplasts into animal cells is a lot easier said that done.”Animal cells recognize chloroplasts as foreign and immediately destroy them, so chloroplasts did not work even when put into animal cells,” Matsunaga said. “As a result, after about 10 years, everyone stopped doing research. It became ‘common knowledge’ in the biological field that chloroplasts by themselves do not function in animal cells.”Aside from being seem as “alien” material, the chloroplasts themselves struggle to function in the environment of an animal cell.”Almost all algae and plant species photosynthesize under 30 degrees Celsius,” Matsunaga said. “Most animal cells are cultured at 37 degrees Celsius.”Therefore, the researchers had to search for chloroplasts that would be able to function I the warm environment of an animal cell.”The success of this study is attributed to the isolation of chloroplasts from schyzon, which grows in a volcanic hot spring in Italy at 42 degrees Celsius and has chloroplast activity even at 37 degrees Celsius,” Matsunaga said.”Planimals”Some animals have managed to harness the power of photosynthesis for themselves. The “leaf sheep” sea slug, for example, is able to absorb the chloroplasts from the green algae on which it feeds. This not only allows the leaf sheep to photosynthesize, but it also turns them bright green, channeling the appearance of an underwater artichoke.
Photo of a leaf sheep, known scientifically as Costasiella kuroshimae. These sea slugs are able to absorb the chloroplasts in the algae they feed on, allowing them to photosynthesize.
Photo of a leaf sheep, known scientifically as Costasiella kuroshimae. These sea slugs are able to absorb the chloroplasts in the algae they feed on, allowing them to photosynthesize.
Kittisak Songprakob/Getty
The next step was to stop the animal cells from rejecting the chloroplasts as “foreign” material.”When chloroplasts are forcibly introduced into animal cells, they are recognized as foreign substances such as bacteria or viruses and are quickly degraded,” Matsunaga said. “[However, our] chloroplasts were fed to animal cells as food, rather than forcing them into animal cells.”Chloroplasts eaten as food could be maintained in the animal cell for at least two days, during which time the initial reaction of photosynthesis could be detected. This is the first time in the world that we have been able to detect the initial reaction of photosynthesis in animal cells. We were able to overturn common sense in biology.”Not only that, the animal cells that contained chloroplasts showed an increased growth rate, suggesting the chloroplasts were providing an alternative source of food for their hosts.”I was surprised because we were able to do something that no one had been able to do for 50 years and that all biological researchers had given up on,” Matsunaga said.So, does this mean we will all be able to start photosynthesizing? Well, we’re not quite there yet.”Since our technology is adapted to cultured animal cells, the shortest path is to consider it useful for the development of [mini model organs for medical research] and artificial meat,” Matsunaga said. “When cells become multilayered, the interior of the cell mass [don’t get enough oxygen,] cell division stops, and size increase is not possible. However, if light can be delivered to the interior of the cell mass, oxygen can be supplied by the captured chloroplasts, the [low oxygen] condition inside the cell mass can be improved, and cell division can resume.”In the future, this process may also show promise in medical settings, for example if patients need more oxygen delivered to certain organs.”If the goal of the therapy is to share oxygen near the blood vessels of the heart in order to improve heart disease, it would be sufficient to implant an LED light source near the heart,” Matsunaga said.Before that can happen, however, the team will need to keep the chloroplasts working for longer than just two days, as was the case in this experiment.”In the future, we will improve our technique so that chloroplasts can carry out photosynthesis in animal cells for as long as possible,” Matsunaga said.Do you have a tip on a science story that Newsweek should be covering? Do you have a question about cellular engineering? Let us know via [email protected], R., Inui, Y., Okabe, Y., Sato, M., Takeda-Kamiya, N., Toyooka, K., Sawada, K., Morita, H., Genot, B., Maruyama, S., Tomo, T., Sonoike, K., & Matsunaga, S. (2024). Incorporation of photosynthetically active algal chloroplasts in cultured mammalian cells towards photosynthesis in animals. Proceedings of the Japan Academy Series B.https://doi.org/10.2183/pjab.100.035