International Caenorhabditis elegans Experiment First Flight-Cells (ICE-First-Cells) studies the effect of space flight on cell migration and muscle cells in C. elegans development. C. elegans (nematode worms) are relatively simple organisms that are used as a model for a wide variety of biological processes. The ICE-First investigation is a collaborative effort conducted by scientists from several countries which have the opportunity to work as a team to design related experiments that would produce valuable results for scientists across multiple disciplines.Principal Investigator(s)
Japan Aerospace Exploration Agency (JAXA), Tsukuba, , Japan
Japan Aerospace Exploration Agency (JAXA)Sponsoring Organization
Information PendingISS Expedition Duration
October 2003 - April 2004
8Previous ISS Missions
The precursor to ICE-First (flown during Expedition 8), BRIC-60/C. elegans, flew on STS-107 (Columbia). Following the break-up of Columbia upon re-entry into the Earth's atmosphere, the samples were located among debris in East Texas and returned to NASA.
ICE-First-Cells is one of several experiments that investigates the effects of spaceflight on a model organism of the nematode worm family (Caenorhabditis elegans) and aims to develop links to human physiology in space. The organism chosen for this study is known to be able to mate, reproduce and develop apparently normally during space flight. Researchers have long tried to figure out why long-term spaceflight can lead to weakened muscles in human astronauts. Many agree that microgravity conditions somehow reduce the rate at which new muscle proteins and fibers are created or synthesized.
C. elegans is a round worm or nematode (Phylum Nematoda) measuring around 1mm and is found naturally in soil. Its body is composed of 959 cells and includes complete reproductive, nervous, muscular, and digestive systems. C. elegans are hermaphrodites (displaying two genders and possessing the ability of self fertilization). Its life span is about 2-3 weeks; although, concerning the liquid medium used for this study at 25°, the life cycle is around 5 days. The entire genome has been sequenced and consists of 97 million base pairs (compared to the 3,000 million found in the human genome) and around 20,000 genes (compared to the 30,000 that humans have) and an entire library of well characterized mutants are available. C. elegans has been used as a model system for various medical pathologies and was the subject of the 2002 Nobel Prize in Medicine or Physiology because the process of programmed cell death or apoptosis was first discovered while studying C. elegans development.
C. elegans has two muscle tissues; pharynx for feeding and a body wall muscle for locomotion. They correspond to heart and skeletal muscle of vertebrates. Recently scientists found that worms with defects in muscle filament genes have defects not only in muscle function but also muscle development. Additionally, these mutants have abnormal distal tip cell migration during the worm development. Abnormal cell migration can easily be seen under the microscope.
The possibilities for longer-term spaceflights are increasing. These types of experiments give scientists an insight into the effect that the environment of space will have on organisms down to the genetic level.Earth Applications
With certain genetic techniques used in this experiment, highlighting the genes where differences occur in comparison to Earth data can further provide scientists with a direction of where to develop research in the future, either on similar organisms or humans. By understanding fundamental processes in C. elegans, scientists can better understand the human counterparts. This study can lead to a further understanding of muscle function and development.
ICE-First-Cells samples are placed in either the Kubik Topaz or Kubik Amber incubator before and after the launch. Filming is required immediately upon the arrival on Earth for later evaluation. The samples are required to stay either frozen or refrigerated until their return to scientists in Toulouse, France two days prior to landing.Operational Protocols
The C. elegans samples are transported to the launch pad in Baikonur, transferred into the Kubik Topaz (incubator with microgravity plate) and kept at 18 degrees C. Three days after the launch, 3 samples are transferred into the Kubik Amber (incubator with centrifuge), while the other five samples remain in Kubik Topaz. On the last flight day, four of the C. elegans samples are injected with a fixative by the crew and all of the samples are placed in Kubik Topaz on the Soyuz and returned to Earth. Upon return to Earth, the containers are filmed to evaluate the behavior of the C. elegans following space flight. The small bags containing the culture of the worms are either frozen or refrigerated until they are returned to their respective principal investigators for detailed analysis.
As with wild-type animals, histologic study of unc-15 (e73) animals was conducted using phalloidin and anti-paramyosin staining. In both ground control and spaceflown unc-15 animals, deformed thin filaments and the aggregated paracrystalline forms of paramyosin (component of smooth muscles) were noted. However, in spaceflown worms, partially formed normal paramyosin filaments were also observed. Additionally, the spaceflown animals displayed a normal muscle filament to body-width ratio that was not observed in the ground control animals. Thus, spaceflight appears to have partially rescued the histologic defects of the paramyosin mutant. Again as with wild-type animals, Western Blots were used to assess the levels of paramyosin, myosin heavy chains B and C, actin, and tropomyosin III (a type of protein). Spaceflown unc-15 mutant animals displayed increased levels of paramyosin and myosin heavy chains relative to both ground controls and spaceflown wild-type animals. In contrast, actin remained the same and tropomyosin III was slightly depressed, although the depression was not statistically significant. Thus, as with wild-type animals, the thick and thin filament proteins showed different effects in response to spaceflight. However, unlike wild-type animals, which showed decreased thick filament proteins in response to spaceflight, unc-15 animals showed increased thick filament proteins. These observations suggest two things. First, spaceflight has a differential effect on thick and thin filaments regardless of mutations in a thick filament gene. Second, spaceflight allows animals to better compensate for a mutation in the thick filaments by increasing thick filament gene expression. Together the histologic and Western Blot data from unc-15 animals suggest that altered muscle development, induced by spaceflight, allows partial rescue of the defects induced by the mutation. A direct elucidation of the functional consequences and the mechanism underlying the rescue remains to be demonstrated. If spaceflight does indeed rescue the functional consequences of mutations in muscle proteins, this suggests that muscles damaged in flight may be better able to repair than muscle damaged on Earth, a view that runs counter to the current conventional wisdom. However, while scientists have presented the unc-15 data as spaceflight having “rescued” the effects of the mutation, the investigators have correctly pointed out that there may be concerns with this apparent rescue. Specifically, their data can also be interpreted to show that increased muscle protein degradation, a required component of muscle atrophy, is found in the mutants vs. wild-type. If the investigators are correct, this reinforces the currently widely held view that muscles damaged during spaceflight may not be properly able to repair. Future studies are clearly needed.
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