Chloroplast-Infused Cells Revolutionize Tissue Engineering

Recent research from Japan has demonstrated that chloroplasts from algae can be integrated into hamster cells, allowing these cells to perform photosynthesis. Previously, it was believed that the fusion of chloroplasts—structures containing chlorophyll found in plants and algae—with animal cells was unfeasible, as the chloroplasts were thought to be incapable of surviving or functioning within the animal cells.

However, findings indicated that photosynthetic activity persisted for a minimum of two days. This method may have applications in artificial tissue engineering, as tissues often face challenges in growth due to insufficient oxygen. Incorporating cells infused with chloroplasts could facilitate the supply of oxygen and energy through light exposure and photosynthesis.

Imagine if, similar to plants or algae, simply basking in the sun could provide one with energy (beyond just vitamin D). While it may sound like a concept from science fiction, certain animals have already harnessed this remarkable ability. For instance, giant clams engage in a symbiotic relationship with algae.

The algae, which contain chloroplasts, can convert light into food and oxygen through photosynthesis. In this arrangement, the clams offer a habitat for the algae, while the algae supply energy that supports the clams' well-being.

Animal cells, unlike plants and algae, lack chloroplasts. Recent research has shown that functionally integrating the two is feasible.

As far as we know, this is the first reported detection of photosynthetic electron transport in chloroplasts implanted in animal cells.”

Sachihiro Matsunaga, Study Corresponding Author and Professor, University of Tokyo

Photosynthetic electron transport produces chemical energy essential for various cellular functions in plants and algae.

We thought that the chloroplasts would be digested by the animal cells within hours after being introduced. However, what we found was that they continued to function for up to two days and that the electron transport of photosynthetic activity occurred.”

Sachihiro Matsunaga, Study Corresponding Author and Professor, University of Tokyo

The team introduced chloroplasts from red algae into cultured cells obtained from hamsters. The researchers analyzed the structure of the chloroplasts within the cells using various imaging techniques, such as confocal microscopy, superresolution microscopy, and electron microscopy.

They also assessed and verified that electron transport related to photosynthetic activity was taking place by employing pulses of light, a method known as pulse amplitude modulation fluorometry.

We believe this work will be useful for cellular-tissue engineering. Lab-grown tissues, such as artificial organs, artificial meat and skin sheets, are made of multiple layers of cells. However, there is a problem that they cannot increase in size due to hypoxia (low oxygen levels) inside the tissue, which prevents cell division. By mixing in chloroplast-implanted cells, oxygen could be supplied to the cells through photosynthesis, by light irradiation, thereby improving the conditions inside the tissue to enable growth.”

Sachihiro Matsunaga, Study Corresponding Author and Professor, University of Tokyo

The team is continuing its research on creating “planimal” cells that can provide the beneficial features of plants to animals. In this study, it was found that animal cells containing chloroplasts exhibited an increased cell growth rate, indicating that the chloroplasts supplied a carbon source (fuel) for the host cells.

The researchers propose that future studies could explore the processes involved in the exchange of substances between the host cell and chloroplasts, as well as the additional substances that are produced.

Matsunaga concludes, “We expect planimal cells to be game-changing cells, which in the future can help us achieve a ‘green transformation’ to a more carbon-neutral society. We will continue to develop innovative biotechnologies with the aim of realizing a sustainable society and the reduction of carbon dioxide emissions.”