Chloroplasts, the parts. The cells that allow plants and algae to carry out photosynthesis are thought to have originated more than a billion years ago, when photosynthetic cyanobacteria lived symbiotically within other primitive cellular organisms.
It was previously thought that replicating the development of this photosynthetic capacity in other cells (by placing chloroplasts inside animal cells) was impossible: animal cells recognize chloroplasts as foreign bodies and digest them. But a Japanese research team has changed this way of thinking. Has developed a technique to isolate photosynthetically active chloroplasts from primitive algae cyanidioschizon and transplant them into Chinese hamster ovary (CHO) cells, a type of cultured animal cell line, and still retain their functionality.
“To our knowledge, this is the first time that photosynthetic electron transport has been confirmed in chloroplasts transplanted into animal cells.” explains Professor Yukihiro Matsunaga of the University of Tokyo. Electron transport is a key process by which plants and algae generate chemical energy, supporting various cellular functions.
Matsunaga’s research team managed to transfer chloroplasts by promoting phagocytosis by CHO cells, which is the process by which cells digest and break down foreign substances.
The research team then used fluorescence laser microscopy and super-resolution microscopy to capture cross-sectional images of the cells and observe how both the cells and chloroplasts behaved. They found that chloroplasts that had been taken up by CHO cells were present within the cytoplasm, the fluid that fills the inside of the cell, and some of them surrounded the cell nucleus. Once the chloroplasts were absorbed, the CHO cells showed signs of behaving normally, for example by continuing to divide.
Further observations using an electron microscope revealed that the structure of the thylakoid membrane of chloroplasts, which is where the enzymes necessary for photosynthesis are found, was maintained for at least two days. Measurements of photosynthetic activity using microscopic imaging and pulse modulation also confirmed that electron transport for photosynthesis was normal during this period. However, on the fourth day after transfer, the thylakoid membrane structure collapsed and the photosynthetic activity of chloroplasts decreased significantly.
This research points to new possibilities in tissue engineering. Artificial organs, artificial flesh, and sheets of skin made from multiple layers of cells have limited growth when the tissue is exposed to low levels of oxygen. If cells incorporating chloroplasts could be added, it would be possible to supply oxygen to the tissue and promote growth simply by illuminating it.
But to achieve this, a technology is required that allows transplanted chloroplasts to maintain photosynthetic activity for longer within animal cells. According to the research team, in the future it will also be necessary to quantify the amount of oxygen generated by the transplanted chloroplasts and the amount of carbon dioxide fixed inside the animal cells, which can be done using a technique called isotopic labeling.
The research team will now continue their research, with the ultimate goal of creating “planimal” cells that have plant capabilities. Planimal cells, if possible, could be a game-changer in multiple industries, including medical research, food production, and energy generation.
This story originally appeared on Japan wired and has been translated from Japanese.