Research to Study Liver Regeneration in Space will fly on SpaceX CRS-29

  - The human liver is a superhero among organs. It works to rid the body of toxins and is capable of regeneration-a unique trait that has fascinated scientists for eons, as evidenced by Prometheus in Greek mythology, who continuously has his liver ripped out by an eagle only for it to regrow the next day as a form of eternal punishment. However, due to the aging process and the hazardous nature of its work, the liver can lose its ability to regenerate, resulting in the need for a transplant.

With more than 100,000 people on the transplant list and not enough organs to go around, researchers are turning to the International Space Station (ISS) National Laboratory to better understand liver cell regeneration.

Research has shown that in the absence of countermeasures, prolonged spaceflight can result in many of the same physiological changes associated with aging, only at a much quicker rate. This makes the microgravity environment of the space station a valuable platform for researching conditions associated with the aging process, including immune system weakening and diminished liver function.

To better understand the mechanisms behind the decline of liver regeneration in the elderly, researchers from the University of California, San Francisco (UCSF) will send tissue chips containing liver cells and immune cells to space. The investigation, funded by the U.S. National Science Foundation, will launch on SpaceX's 29th Commercial Resupply Services (CRS) mission to the space station. Tissue chips are small devices designed to model the function of human tissue. By taking tissue chips to space, researchers can observe microgravity-induced changes in human physiology relevant to disease, which could lead to novel therapies for patients on Earth.

"The liver has the most regenerative capability of any organ in the body," said Sonja Schrepfer, a professor of surgery at UCSF. "But how is the liver affected by prolonged stays in microgravity? Will it lose some of that capability?"

In a previous ISS National Lab-sponsored experiment, Schrepfer learned that immune cells age in microgravity in just three days, diminishing their protective abilities. This change in immune cells can also affect other cells in the body, such as the stem cells involved in tissue regeneration.

In this current investigation, Schrepfer and her team will examine the influence of age-related immune dysfunction (also known as immunosenescence) on the regenerative capacity of liver tissue-specific stem cells. Specifically, the team will focus on liver progenitor cells (LPCs) and will study how they behave in microgravity and after they come back to Earth.

Many of the physiological changes observed in cells during spaceflight revert to pre-spaceflight conditions after returning to Earth. This unique observation means that the researchers can study the fundamental processes involved in the aging process and look for ways to reverse them.

"In our other study, we learned that mesenchymal stromal cells (MSCs), multipotent stem

cells that can repair cartilage and bone, can recover after spaceflight, but endothelial progenitor cells (EPCs), stem cells that develop into vascular cells, cannot," said Schrepfer. "So, we're curious to see what happens with the liver progenitor cells."

The SpaceX CRS-29 mission, scheduled to launch from Kennedy Space Center on November 7, 2023, at 9:16 p.m. EST, includes more than 15 ISS National Lab-sponsored payloads.