Hundreds of test tubes containing adult human stem cells have made their way to the International Space Station (ISS) as researchers aim to test their ability to grow into organ-like structures known as organoids in microgravity environments. If successful, scientists say that the experiment could lead to new methods for someday growing bones, cartilage, and other organs for transplantation and precision medicine.

University of Zurich (UZH) Space Hub researchers sent 250 test tubes on Space X's CRS-20 resupply mission, which took off from Cape Canaveral, Florida onMarch 7, and was caught by astronaut Jessica Meir operating the ISS' robotic arm yesterday morning. In the shipment is a mobile mini-laboratory called the CubeLab, a closed sterile system that allows stem cells to proliferate and differentiate at constant variables in a controlled environment. Stem cells are human cells that have the ability to turn into many different types of cells. Differentiation occurs when one cell changes to a more specialized type. This process typically happens after proliferation, whereby the cells replicate many times, according to the National Institutes of Health.

“Physical forces such as gravity appear critical in cell differentiation and organization of tissue formation and regeneration. Because cells exhibit spatially unrestricted growth and can assemble into complex 3D aggregates in microgravity, low-Earth orbit may make it possible to manufacture human tissue structures,” write the researchers in the experiment description for NASA’s Space Station Research Explorer.

Weightlessness aboard the ISS is being used as a “tool” to determine how physical forces influence the way that stem cells differentiate as well as tissue is organized during formation and regeneration. It is thought that low gravity aboard the ISS will allow for newly formed cells to organize into three-dimensional tissues.

If the experiment is successful, the researchers say they plan to gradually shift to a larger production scale for future tissue generation to be used in transplants, like cartilage or new liver cells. The astronomical lab may also provide an alternative to animal experiments, paving the way for a new direction in future medicine.

"Artificially produced autologous human tissue could be used to determine which combination of drugs is the most suitable for the patient in question. In addition, human tissue and organ-like structures produced in space could help to reduce the number of animal experiments,” said Oliver Ullrich, Professor of Anatomy at UZH, in a statement.

The experiment is part of a public-private partnership between the University of Zurich and Airbus, who helped to provide logistical planning and equipment for research. Ullrich adds that declining costs of transporting objects to space has made research more affordable and accessible.

"In space projects, the main cost drivers are the custom-made hardware and the bureaucracy," says Ullrich. "In a few decades, humankind will use the low Earth orbit as a routine place for research, development, and production.”

Many projects have been conducted aboard the ISS to test out microgravity conditions, including growing lettuce that has been shown to be as safe to eat as Earth-grown leafy greens, and a recent SpaceX collaboration aiming to send hundreds of hemp and coffee plants to the station.

After their month-long stay aboard the ISS, the Space Hub researchers will study the organoids at the histological, cellular, molecular, and functional levels back on Earth.