Astronauts are growing livers in space, where microgravity can help them thrive

Miniature livers will fly on board International space station in a future study on whether microgravity can promote the growth of healthy tissue with adequate blood supply.

It’s an effort that could potentially lead to personalized, space-grown tissues and organs for use in transplant surgeries, scientists say. In two upcoming experiments, the researchers plan to test how well liver tissue grows in microgravity, and to test a new technology designed to keep the tissue alive but supercooled for its journey back to Earth.

“My ultimate goal with these tissues, if they do what we imagine and hope they can do with microgravity, is to use these tissues for therapy,” said Dr. Tammy Changprofessor of surgery at the University of California, San Francisco. The tissue can be transplanted to treat a variety of liver diseases and disorders, Chang told Live Science.

Growing tissue in a lab dish on Earth can be difficult, in part because gravity pulls the cells into contact with the bottom of the dish or dish. Gravity also subjects the cells to shear stress because to keep the cells in suspension as they grow, their bowl must be agitated. After all, in nature, organs arise from a developing embryo as it floats in the amniotic fluid in the womb, or in the fluid cushion created by the egg.

These persistent problems with gravity have led researchers to develop rotating bioreactors that simulate a low-gravity environment by rotating very quickly. This allows tissues and miniature organs, or “organoids,” to grow in artificial conditions, but these rotating vessels also place stress on the tissues, especially as the cell clusters within them become larger.

Chang and his colleagues believe that organoids can grow better in a stable, high-quality microgravity environment similar to that seen on the International Space Station.

“These organelles, which are typically 200 microns in diameter, which is 0.2 millimeters (0.008 inches) in diameter, will be able to further organize and interact with each other to develop larger tissues and, in particular, vascularized tissues,” he said. Chang, who presented her research at the 2024 American College of Surgeons Clinical Congress in San Francisco on Tuesday (Oct. 22). Vascularized tissues are penetrated by many blood vessels.

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An image of liver cells under a microscope, shown in green and purple — This image shows a magnified liver organoid grown in a tissue pellet.(Image credit: Tammy T. Chang, MD)

To grow their space-age liver organoids, Chang and her team use “induced pluripotent stem cells,” meaning adult cells reprogrammed into stem cells that can give rise to different types of tissue. The researchers then induced these engineered stem cells to transform into liver cells and grew the cells in a special spherical bioreactor called the Tissue Orb. This ball reactor has a central channel that mimics a blood vessel in its center. Cultivating organoids with such a circulatory system is key to growing larger pieces of tissue.

“Our concept is that these organelles in the main chamber can merge and interact with the central channel and develop a more complex and more vascularized tissue,” Chang said.

The future experiment with liver tissue will fly to the ISS in early 2025. The tissues will grow aboard the station for two weeks before being fixed — placed in a preservative solution — for analysis on Earth. A second experiment, likely to take place later in 2025 or early 2026, will test a supercooling system for returning living tissue to Earth.

These miniature livers are not the first organoids grown on board the ISS. Researchers use space-grown organoids to investigate questions from how the brain ages to how cancer develops and responds to drugs.

Conducting an experiment aboard the space station is the culmination of years of work, Chang said: “It’s very exciting to conduct an experiment aboard the ISS.”

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