Time-Lapse Imaging of Neural Stem Cells Exposed to Microgravity on the International Space Station
Scott Olenych ZEISS Research Microscopy Solutions
scott.olenych@zeiss.com
Abstract: Astronauts who spend significant time in space may expe- rience intracranial hypertension (pressure inside the skull), which often does not normalize upon return to Earth. This type of
intra-
cranial pressure can cause vision problems, headaches, glaucoma, and other serious health problems, making it a significant obstacle to long-duration space exploration missions. NASA is hoping that a better understanding of how central nervous system stem cells divide in microgravity will help lead to ways to protect astronauts from prob- lems with intracranial pressure and to design adequate preventive measures. These studies examine cell growth and division of neural stem cells that experienced microgravity on the International Space Station and were returned to normal gravity prior to live-cell imaging studies to determine cell changes.
Keywords: neural stem cells, oligodendrocytes, microgravity, time- lapse imaging, International Space Station
Introduction: Unique Study Investigates Multiplication of Human Nervous System Cells in Microgravity Dr. Araceli Espinosa-Jeffrey, a research neurobiologist at
the Semel Institute for Neuroscience and Human Behavior at UCLA, has had a long-standing interest in making more neu- ral cells faster. Her initial interest was for their use in trans- plantation research, and she has conducted experiments that observed a faster rate of cell growth in simulated microgravity (sim‐μG) compared to that seen under standard Earth gravity conditions [1]. Believing that studies using microgravity will increase our understanding of the brain in health and disease, and in particular, to the discovery of new molecules and mech- anisms impossible to unveil while in normal gravity condi- tions (1G), she sought and obtained funding from the National Aeronautics and Space Administration (NASA) to place an experiment using human brain cells aboard the International Space Station (ISS). For the NASA studies, human brain cells were flown to
the ISS on the SpaceX CRS-16 mission with the goal of gain- ing a better understanding of how neural stem cells grow and develop in true microgravity (Figure 1). Understanding cell response to true microgravity conditions is key to discover- ing more about the serious issues of intracranial hyperten- sion affecting astronauts returning from space. In the future, information gathered may also be used to further cell replace- ment therapies for people with neurological disorders or neu- rological diseases. To study the effects of microgravity on the cells that had been on the ISS, Dr. Espinosa-Jeffrey and her research team conducted time-sensitive 72-hour time- lapse imaging to examine proliferation, migration, and other features of cells as they readapted to terrestrial gravity. Te goal was to confirm and expand the results from the sim‐μG
26 doi:10.1017/S1551929520001352
microgravity experiments they had conducted and to learn more about cells in space microgravity, including the effects on different cell types [1,2]. NASA’s particular interest in funding the research was
spurred by its desire to learn more about the role increased divi- sion of these cells in space may play in the intracranial hyper- tension (pressure inside the skull) observed during human spaceflight, which oſten does not normalize when astronauts return to Earth. Tis type of intracranial pressure can cause vision problems, headaches, glaucoma, and other serious health problems, making it a significant obstacle to long-dura- tion space exploration missions. NASA is hoping that a better understanding of how central nervous system stem cells divide in microgravity will lead to the design of adequate preventive measures and protection for astronauts from problems with intracranial pressure. Te work was similar to a study investigating oligoden-
drocyte progenitors (OLPs) grown in simulated microgravity and designed to investigate the effects of space microgravity on the global secretome of these cells including molecules important for cell-cell communication, function, stemness, and differentiation. Te knowledge gained from these experi- ments will contribute to a better understanding of how stem cell growth is affected by gravity at the molecular level and may help advance neural stem cell technologies that would be useful in wound healing, tissue regrowth, and organ culture. When OLPs used in this study were cultured in sim‐μG
on the ground, they divided faster than cells cultured under normal gravity conditions [1]. Espinosa-Jeffrey has reported that neural stem cells also proliferated more in sim‐μG [3] and space microgravity [4]. Studying the reasons why, and the mechanisms causing these cells to divide faster in microgravity, could pave the way to breakthroughs in stem cell production for cell replacement therapies. Finding ways to generate more stem cells is urgent because there is cur- rently no way to quickly produce the large numbers of “self” stem cells needed for the many cell replacement therapies that are showing such promise for people with neurological disorders, neurological diseases like multiple sclerosis, and developmental disabilities. In addition, using one’s own cells without graſting donor
cells and tissues opens the possibility that a neural stem cell donor could be his or her own recipient, eliminating risks of rejection. Such an approach could be used for repair of head and spinal injuries, as well as other cell replacement therapies. In addition to her work with NASA, Dr. Espinosa-Jeffrey would like to work on these issues with the Center for the Advance- ment of Science in Space, Inc. (CASIS, also known as the ISS
www.microscopy-today.com • 2020 September
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