Experiment on China's Space Station Predicted to Yield New Approach for Fatty Liver Treatment

A study conducted on China’s Tiangong space station is expected to identify the metabolic regulation mechanisms of a type of liver cell and present a new approach to treating fatty liver disease. The seven-day in-orbit experiment, completed last week, was designed to explain the effects of biological phase separation related to the space environment on lipid metabolism under microgravity conditions. Space microgravity forms a unique mechanical environment, involving factors that strongly regulate the metabolic functions of hepatocytes, the main type of liver cell, according to Li Ning, a researcher at the Institute of Mechanics of the Chinese Academy of Sciences. The liver is an organ with a highly complex mechanical microenvironment. ‘In the development of diseases such as liver fibrosis or fatty liver disease, changes occur in this micromechanical environment, including increased stiffness and changes in blood flow,’ Li said. Based on extensive experimental findings, scientists believe the most direct mechanical factor causing abnormalities in lipid metabolism in the liver is fluid shear stress. Under normal conditions, blood flow creates interstitial shear stress as it passes through the walls of hepatic blood vessels, ‘washing’ the hepatocytes and thus maintaining metabolic homeostasis. However, in a microgravity environment, the cephalad redistribution of body fluids leads to increased blood flow above the heart and decreased blood flow below it, resulting in a significant reduction in portal venous blood flow to the liver. At the same time, the loss of hydrostatic pressure reduces the pressure load on the liver. ‘The mechanical effects of blood flow on the liver are reduced in space,’ Li noted. Consequently, the regulatory role of blood flow is diminished, and more fat accumulates. To investigate how blood flow shear stress regulates liver metabolic function, experiments conducted during the Shenzhou-16 spaceflight mission have shown that the microgravity environment activates SREBP protein, leading to an increase in intracellular lipid droplets. However, blood flow inhibits SREBP and provides a protective effect, thereby reducing lipid droplets. Given previous research has confirmed the protective effect of the blood flow environment on cells, the new experiment specifically designed a corresponding intervention group to enhance the cell response to mechanical stimulation from blood flow. The in-orbit experiment selected hepatocytes as the research subject and designed three experimental conditions including static culture, simulated blood flow environment, and ‘blood flow environment with drug stimulation,’ yielding a total of six cell samples. The entire experiment was initiated by Earth-based researchers via remote commands. ‘During the in-orbit culture period, we performed microscopic imaging of the cells daily to observe their growth status in real time,’ Li said, adding that on the seventh day, the system automatically injected a fixative solution to preserve the cell condition. Afterwards, the samples were placed in a minus 80 degrees Celsius freezer for storage. The samples are scheduled to be brought back to Earth in the second half of this year. The comprehensive collection and in-depth analysis of the core data will officially begin thereafter.