Evaluation of Techniques for Performing Cellular Isolation and Preservation during Microgravity Conditions

Abstract

Genomic and epigenomic studies require the precise transfer of small volumes from one container to another. Epigenomic and transcriptional analysis require separation of purified cell types, and long term preservation of cells requires their isolation and transfer into appropriate freezing media. There are currently no protocols for these procedures on the ISS. Currently samples are either frozen as mixed cell populations, with poor yield, or returned under ambient conditions, requiring timing with Soyuz missions. Here, we evaluate the feasibility of translating terrestrial cell purification techniques to the ISS. Our evaluations were performed in microgravity conditions during parabolic atmospheric flight. The pipetting of open liquids in microgravity was evaluated using analog blood fluids and several types of pipette hardware. The best performing pipettes were used to evaluate the pipetting steps required for peripheral blood mononuclear cell (PBMC) isolation via density gradient centrifugation (DGC). Evaluation of actual blood products was performed for both the overlay of diluted blood, and the extraction of isolated PBMCs. We also validated magnetic purification of cells. We found that positive displacement pipettes avoided air bubbles, and the tips allowed the strong surface tension of water, glycerol and blood to maintain a patent meniscus and withstand robust pipetting in microgravity. These procedures will greatly increase the breadth of research that can be performed onboard the ISS, and allow improvised experimentation on extraterrestrial missions.