Neural Stem Cells
Due to delays, cells were maintained on the ISS for 39.3 days instead of the 35 days originally anticipated. Aſter splashdown, transport to Long Beach airport, and delivery to UCLA, the human neural stem cells were retrieved from the hardware, plated onto poly-d-lysine-coated flasks in a stem cell chemi- cally defined medium [5], and allowed to recover from space flight. Researchers then began measuring how much the cells had divided while in space by using the Automated Type IV units from Yuri. Aſter space flight, cells were seeded onto microscopy
compatible flasks and 72 h continuous time-lapse microscopy allowed analysis of cell proliferation and measurement of the cell cycle duration [6]. Moreover, using the same approach, Dr. Espinosa-Jeffrey’s team is currently determining the effects of the secretome of stem cells flown onto space on 1 G (naïve) cells and identifying the proteins secreted.
Dedicated Microscope Resources Needed for Crucial Time-Lapse Imaging Time-lapse imaging and cell division and proliferation
Figure 4: Diagram of an oligodendrocyte wrapping around a neuron’s axon. Te two cell types sent to the International Space Sta-
tion were maintained in cell culture hardware developed by Airbus-Kiwi (Friedrichshafen/Germany, formerly .kiwi- microgravity, currently Yuri,
https://www.yurigravity.com/ our-service) ( Figure 5) and then installed in the Space Tech- nology and Advanced Research Systems (STaARS)-1 Experi- ment Facility, where the cells were given time to grow and divide. Dr. Espinosa-Jeffrey designed the experiments and inspired the STaARS team to design the self-contained cell culture box. Automated control of the experiments, includ- ing culture media exchanges, was conducted from Houston, TX so astronauts would not have to invest time on this task.
studies were conducted with the ZEISS Axio Observer 7 fully motorized inverted research microscope equipped with Defi- nite Focus 2, ZEISS Axiocam 506 monochrome camera with ZEISS ZEN soſtware, and ZEISS Full Incubation XL chamber for temperature and CO2
control with a motorized scanning
stage (Figures 6 and 7). Live-cell imaging equipment was essen- tial as all data had to be collected within 72 hours using a con- trolled temperature and gas environment equivalent to what cells would experience in a standard tissue culture incubator. Te cells had to be kept at the temperature of the human body with in vivo conditions to mimic their native environment to avoid the risk of sample degradation over time and a poten- tially diminished ability to detect subtle effects of the space- flight environment. Completion of the analysis was especially time critical. For extended time-lapse studies, images were col- lected every 10–15 minutes at each of 6 to 8 xyz positions for 72 hours (Figure 7). From the position list several time-lapse movies were created demonstrating cell growth and prolifera- tion, as well as other features such as migration.
Discussion It was extremely important to begin
analysis immediately, so there would be no chance of missing any changes to the cells. It was important to show that cells behaved as
Analysis of data from time-lapse images showed that
these cells had proliferated
Figure 5: (Left) Dr. Espinosa-Jeffrey holding the Airbus-Kiwi (Yuri) cell culture automated chamber [7]. (Right) Airbus-Kiwi (Yuri) automated cell culture chamber.
28
post-flight at comparable rates to control cells growing in normal gravity. For fur- ther studies, Dr. Espinosa-Jeffrey’s team is now characterizing the secretome of space flight cells for novel features that they have not observed in ground control cells or in their simulated microgravity studies. Te Espinosa-Jeffrey team, using time- lapse microscopy, has recently reported
www.microscopy-today.com • 2020 September
they did in simulated microgravity, where some cells move
slightly faster.
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