Microfluidics-integrated spaceflight hardware for measuring muscle strength of Caenorhabditis elegans on the International Space Station

Abstract

Caenorhabditis elegans is a low-cost genetic model that has been flown to the International Space Station to investigate the influence of microgravity on changes in the expression of genes involved in muscle maintenance. These studies showed that genes that encode muscle attachment complexes have decreased expression under microgravity. However, it remains to be answered whether the decreased expression leads to concomitant changes in animal muscle strength, specifically across multiple generations. We recently reported the NemaFlex microfluidic device for the measurement of muscle strength of C. elegans (Rahman et al., Lab Chip, 2018). In this study, we redesign our original NemaFlex device and integrate it with flow control hardware for spaceflight investigations considering mixed animal culture, constraints on astronaut time, crew safety, and on-orbit operations. The technical advances we have made include (i) a microfluidic device design that allows animals of a given size to be sorted from unsynchronized cultures and housed in individual chambers, (ii) a fluid handling protocol for injecting the suspension of animals into the microfluidic device that prevents channel clogging, introduction of bubbles, and crowding of animals in the chambers, and (iii) a custom-built worm-loading apparatus interfaced with the microfluidic device that allows easy manipulation of the worm suspension and prevents fluid leakage into the surrounding environment. Collectively, these technical advances enabled the development of new microfluidics-integrated hardware for spaceflight studies in C. elegans. Finally, we report Earth-based validation studies to test this new hardware, which has led to it being flown to the International Space Station.

WormSpace μ-TAS enabling automated on-chip multi-strain culturing and multi-function imaging of Caenorhabditis elegans at the single-worm level on the China Space Station

“…Additionally, these earth-based studies mainly used bacteria-based liquid culture media, which possibly results in the clogging of microfluidic channels and brings the risks of biosafety to the crew and workstation on the space station. Recently, Soni et al 6 verified the feasibility of microfluidic-based C. elegans spaceflight experiment. However, in this work, nematodes were cultured in liquid bags and periodically loaded into the chambers of the chip for observation by astronauts, resulting a low degree of automation and deficiency of validating on-chip long-term cultivation in orbit.…”

“…5 Together, C. elegans has been recognized as an excellent model system for space biology research. 6…”

“…5 Together, C. elegans has been recognized as an excellent model system for space biology research. 6 From 1992 to 2021, C. elegans was flown in several spaceflight investigations through the space transportation system (STS), 3,[7][8][9][10][11] DELTA MISSION (ICE-FIRST) 2,5,12 and SpaceX mission 4,13,14 to the International Space Station (ISS), or from China's Shenzhou-8 spacecraft 15,16 and Shijian-10 recoverable scientific satellite. 17 These studies mainly focused on the biological effects of space radiation and microgravity, and most of them used genomics or proteomics to analyze C. elegans populations with multiple generations and different developmental stages.…”

A Compact Imaging Platform for Conducting C. elegans Phenotypic Assays on Earth and in Spaceflight

“…Nematode sample preparation usually occurs on Earth, with worm culture bags being flown to the ISS, where the crew extracts samples and injects into the microfluidic chips. The authors have recently flown to the ISS micropillar-based microfluidic devices for muscle strength measurements in C. elegans [ 20 ], and the CIP is a valuable addition to the imaging needs on the ISS.…”

“…The numerous advantages that underscore the use of C. elegans as a genetic model on Earth also translate to its use in spaceflight as a cost-effective organism to understand the mechanisms underlying the effects of microgravity and radiation exposure on astronaut health. Indeed, C. elegans have been flown several times to the International Space Station (ISS) [ 16 , 17 , 18 , 19 , 20 ]. The conducting of animal experiments on the ISS is associated with stringent operational requirements on payload size, weight, crew time and safety [ 21 , 22 ].…”