International Space Station Experiments


Drosophila Motility, Behaviour and Ageing

The main scientific objectives of the experiment are to study in more detail the mechanisms of the abnormal motility response encountered in space by young flies with consequences on the posterior aging response of the flies. For this purpose, three different fly strains with different phenotypes are used, in four configurations. The three strains are a long-lived strain, a short-lived strain and a strain showing an abnormal gravitropic response on the Ground. Recently hatched flies of the three phenotypes will be exposed to the Space Environment. In addition, a two-week old population of the short-lived strain will be also included to confirm the differences between them. During flight, the only experimental activity planned is the video recording of the in flight motility in the different experimental containers. This will be complemented by an extensive series of post-flight analyses involving behavioural assays (gravitropic responses, mating activity of the males, optokinetic responses, gene expression profiles and neuropeptide patterns of defined neurons). The experiment will be complemented by appropriated ground controls involving space simulation exposures of equivalent groups of flies.

Findings so far:
Sensory and nervous system are rather insensitive to microgravity. However, change in the gravity environment appears to alter the behavior of flies and cause accelerated ageing.

Role of Gravity and Geomagnetic Field in Flatworm Regeneration

Advances in the regenerative process will have transformative implications for regenerative medicine as well as design of flexible, robust robotic and communication systems. In KS5: Role of Gravity and Geomagnetic Field in Flatworm Regeneration (Flatworm Regeneration), it is proposed to expose planarians to the microgravity environment to understand the role of gravity in their amazing healing abilities. The experiment includes intact control worms, and worms with their heads or tails amputated, placed in sealed spring water vials before sending these into space immediately after amputation. The regeneration patterns are analyzed (via morphological and molecular-genetic methods) in the lab on Earth upon their return.

It is important to understand how living tissues use physical forces to control pattern formation., A specific hypothesis about the role of gravity and the geomagnetic field in the pathways that regulate complex tissue patterning and wound healing is made once it is determined what aspects of morphogenesis are disrupted by microgravity and loss of the geomagnetic field.

For measuring and scoring the molecular difference in the flatworms, in situ hybridization or immunohistochemistry is used.  The same criteria as used in the hundreds of published papers in the planarian model system is utilized, which is the difference between control and experimental patterns should be bigger than the difference observed within the group of approximately 20 controls. Immunofluorescence and in situ hybridization signal is not usually quantified – the expression of transcripts or proteins in inappropriate locations (e.g., a head marker expressed in a tail wound) is quite obvious – a qualitative, not quantitative, difference.

Progress into the basic mechanisms of embryonic development and complex organ repair/regeneration advances space exploration. Experiments conducted in the unique environment of space enrich understanding of biophysical mechanisms that underlie complex pattern formation. In particular, the role of bioelectrical signals in this process needs to be understood, as these signals are an especially powerful means of cell regulation that underlie information processing in all cell groups.

The objective of Flatworm Regeneration is to understand the first step in “mapping’ the mechanisms of how an organism determines the placement of damage and how it instructs the “leading edge” to grow the particular area or appendage that has been damaged. This mapping may lead to more effective treatments in conditioning injuries for regrowth by coaxing the damaged area into appropriate growth. Additionally the mapping could be used as the basis for algorithms of self-replicating or repairing robots which themselves have boundless uses.

The growth of the flatworm is analyzed morphologically (looking at anatomical markers such as shape, size, and proportion of the different regenerated organs) and, any differences from control animals are noted, with further analysis using molecular genetics (for spatial expression profiles of genes known to control regenerative patterning) to understand the mechanism by which the changes in regenerative shape occurred.  Molecular analysis will include in situ hybridization and immunehisto-chemistry for markers of head blastema, tail blastema, innervation, eye tissue, neoblasts (stem cells), apoptosis (programmed cell death), and a set of ion channels and pumps known to be important for normal patterning.

Findings so far:
Flatworms regenerate their own cells, replacing them as they age or are damaged. KS5: Role of Gravity and Geomagnetic Field in Flatworm Regeneration (Flatworm Regeneration) studies the cell signaling mechanisms these organisms use while regenerating their tissue in microgravity. Results provide insight into how gravity affects tissue regeneration and the rebuilding of damaged organs and nerves, which is important for understanding how wounds heal in space.

Mice Drawer System (MDS)

Mice Drawer System (MDS) is an Italian Space Agency experiment that will use a validated mouse model to investigate the genetic mechanisms underlying bone mass loss and other microgravity effect on different tissues such as muscles, glands, brain. Research conducted with the MDS is an analog to the human research program, which has the objective to extend the human presence safely beyond low Earth orbit.
Science Results for Everyone
The Mice Drawer System (MDS) used three wild-type (Wt) and three PTN mice (which have had a foreign bone-metabolism gene inserted) to investigate genetic mechanisms of bone loss and effects on other tissues in microgravity. One PTN and two Wt mice died due to health- or payload-related reasons, but tissues were used in 20 different investigations of microgravity-induced modifications, primarily focusing on bone loss. These revealed loss in the weight-bearing bones of both strains; muscle atrophy; changes in atrophy-related genes; structural changes in thyroid and testes; changes in regulation of immune response, metabolic, inflammatory and catabolic genes; and changes in blood cell parameters.

Role of Weightlessness on Metabolism (Actin)

This experiment aims at studying the effect of weightlessness on the structure and metabolism of cellular actin microfilaments in mammalian cells. Actin is one of two proteins involved in muscle contraction and is found in both smooth and striated muscle. It also serves as an important structural molecule.

Science Results for Everyone
Are astronaut’s muscles ‘actin’ up? This experiment studies the effect of weightlessness on actin, a protein involved in muscle contraction. Mouse muscle cells were sent into space, preserved and returned, then the actin labeled with fluorescent phalloidin (a toxin with high preference for filamentous actin). No flight results were obtained due to a combination of malfunctioning hardware and unfulfilled temperature requirements, but analysis clearly revealed increased actin content of the cells under microgravity conditions, suggesting that actin is gravity-sensitive. Simultaneous ground controls using the same batch of cells gave normal results.

Eyespots and Macular Pigments Extracted from Algal Organisms Immobilized in Organic Matrix with the Purpose to Protect Astronaut’s Retina (Night Vision)

One of the main problems for astronauts exposed to long-duration space flight is the exposure to ionizing radiation and the consequent oxidative stress. One of the organs affected by ionizing radiation is the human retina. Moreover, the continuous changes in light due to the movement of the International Space Station (ISS) can lead astronauts to experience various dawns and sunsets over 24 hours. These phenomena cause troubles and difficulties in maintaining the rhythm of sleeping and the vision is particularly difficult in missions external to the ISS.

Lutein (substance found in vegetables that protect against cell damage) and zeaxanthin (substance usually found in yellow/orange fruits and vegetables, as well as egg yolks) are the pigments present in both the macula and lens of the human eye which are also referred to as macular pigments (MPs). They belong to the family of xanthophylls (yellow and orange pigments found in plants, animal fats and egg yolks) which are oxidized derivatives of carotenes, including several compounds. Both carotenes and xanthophylls belong to a class of polyisoprenoids (synthetic molecules). MPs’ effects on the human body include the improvement of visual function, and the protection from photo-induced damage, as they act as filters for blue light and shield short-wave radiation. Epidemiological studies have shown a strong correlation between the levels of lutein and zeaxanthin in eye tissues, serum and blood plasma, with a reduced incidence of oxidative stress associated with age and macular degeneration pigment. MPs cannot be synthesized by the organism and must be introduced via the diet. There are other xanthophylls that also play an important role in protecting visual apparatus. The unicellular alga Chlamydomonas reinhardtii possess only one chloroplast that is in contact with an orange organelle called eyespot; similar to the human retina. As the human retina, the algal eyespot presents macular pigments involved in perception of light and a similar organization. Other algae with similar eyespots include Chlamydomonas nivalis andHaematococcus pluvialis.

This project proposes the study of resistance to ionizing radiation of algae and Chlamydomonas reinhardtii genetic mutants that accumulate various quantities of macular pigments in the eyespots. The extracts of eyespots will also be immobilized in alginate (salt from alginic acid) and their antioxidant effects will be evaluated for future nutrition programs in space. These immobilized matrices will be analyzed by means of X-ray (powder X-ray diffraction, XRD) to study the relationship between organization and functionality of the eyespots.

One of the organs mostly affected by cosmic radiation is the visual apparatus; in particular, the central and peripheral photoreceptors of the retina. The global vision in astronauts is disturbed in the perception of colors and movements. The result is that the vision during the night exploration is particularly disturbed. Recent studies on the ISS suggest that a unique ionizing heavy particle can hit one or plus photoreceptors in the retina, including damage to other eye tissue, such as the lens. The mechanism of oxidation at retina level is not known in detail. One hypothesis is that the damage is generated from a genetic damage in the lens epithelial cells, including the destruction of normal cellular life cycle, apoptosis (cell death), abnormal differentiation of cells and cellular disorganization.

The Department of Aviation Medicine is particularly interested in increasing the visual efficiency of astronauts as the number of working hours is reduced as a result of reduced visual fatigue. To understand what happens inside astronauts’ eyes, scientific literature proposes several models in vivo and in vitro as to study the high ocular pressure in the retina and in the optical nerve, which occurs during oxidative stress. For the in vivo studies, an empiric model based on guinea pigs is used, causing ocular hypertension by injecting methylcellulose in front of the eyes. In guinea pigs, or humans affected by oxidative stress, eye neural tissue degenerates with a cell death program.

Mechanisms for plant adaptation to space environment

Successful plant growth in closed-loop life support conditions is a difficult challenge for the realization of long-term habitation of spacecraft and other extraterrestrial environments. In such environments, plants can undergo stress induced by a number of factors including changes in gravity, radiations, vibration, limited exchange of gases, and suboptimal growth conditions (temperature, light, nutrients). These sources of stress are often associated with reprogramming of gene expression and can cause limited plant growth, development and yield.

To facilitate plant life in space, it is crucial to acquire a better understanding of the genetic changes that enable plant cells to respond to spaceflight stress. To do so, one goal of this proposal is to define the underlying mechanisms of plant adaptation to spaceflight environment at a transcriptional level. A protein named AtIRE1 has been successfully identified as a master regulator of transcription in conditions of stress responses to abiotic, biotic stress, and gravity changes in plants. A better understanding of the signaling pathways controlled by AtIRE1 are not well defined, especially in conditions of altered gravity. Additional research on the signaling pathways controlled by AtIRE1 is important to gain a better understanding on how plants can grow in conditions of stress.

In-flight and ground resources are used, along with genomics and transcriptomics analyses in the model plant Arabidopsis thaliana to understand the regulartory role of AtIRE1 in adaptation to space flight stress. Further development of this research contributes to the understanding of basic signaling pathways that are in place to ensure stress survival in hostile environments, thus making possible the design and growth of plants that are resistant to space stress. To contribute further to the successful realization of habitation in space, the aim is to develop plants that can function as bioindicators of stress during in-flight situations. To do so, plants are engineered with an AtIRE1 substrate that is activated specifically in conditions of stress and are adapted to function as a visual stress reporter. The availability of real-time stress bioindicators provides scientists and astronauts with direct read-outs of stress in the space environment.

The results gathered in our research contributes to NASA’s strategic plans for the realization of long-term habitation of space and planetary surfaces. Because of the conservation of stress sensing and response mechanisms across multicellular organisms, the results are expected to have important implications for the general knowledge of stress and the design of solutions for space stress management in multicellular organisms, including humans.

Gravity Related Genes in Arabidopsis

Gravity Related Genes in Arabidopsis – A (Genara-A) will address the existence of gravity regulated genes, which affect the mechanism of gravisensing and the redistribution of plant growth hormones.

For this purpose the growth of Arabidopsis shall be followed by optical observation of 1g reference samples and samples grown under microgravity.

Genara-A will provide an understanding of microgravity induced altered molecular activities which will help to find plant systems that compensate the negative impact on plant growth in space, an aspect of special importance for the application of plant based systems in life support systems or as food source for long-duration space flights beyond low Earth orbit.
The existence of gravity regulated genes, whose expression depends (at least) upon the mechanism of gravisensing and the redistribution of hormones, shall be addressed properly in this experiment. In transgenic Arabidopsis plants, several biomonitors will report the distribution of IAA (plant hormone auxin [Indole-3-Acetic Acid]) and ABA (plant hormone [Abscisic Acid]) at the tissue level in microgravity or in the 1-g centrifuge.

Science Results for Everyone
Plants get stressed out in space. This investigation of how microgravity alters molecular activities in plants helps identify those plants which can compensate for the negative effect of space on growth. Membrane proteins were extracted from seedlings grown in space, on a 1-G reference centrifuge, and on the ground. Among 1,484 proteins identified and quantified, 80 were significantly more abundant in the seedlings grown in microgravity in space. Proteins associated with metabolism and movement of growth hormones were depleted by microgravity, while those associated with stress responses, defense, and metabolism were more abundant. This indicates that plants perceive microgravity as a stressful environment.


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