Below, explore peer-reviewed journal articles related to ISS National Lab investigations. For a more extensive list of spaceflight-related publications (not limited to ISS National Lab sponsorship), see the International Space Station Research Results Citations on the NASA website.
Regeneration is regulated not only by chemical signals but also by physical processes, such as bioelectric gradients. How these may change in the absence of the normal gravitational and geomagnetic fields is largely unknown. Planarian flatworms were moved to the International Space Station for 5 weeks, immediately after removing their heads and tails. A control group in spring water remained on Earth. No manipulation of the planaria occurred while they were in orbit, and space-exposed worms were returned to our laboratory for analysis. One animal out of 15 regenerated into a double-headed phenotype?normally an extremely rare event. Remarkably, ampu- tating this double-headed worm again, in plain water, resulted again in the double-headed phenotype. Moreover, even when tested 20 months after return to Earth, the space-exposed worms displayed significant quantitative differences in behavior and microbiome composition. These obser- vations may have implications for human and animal space travelers, but could also elucidate how microgravity and hypomagnetic environments could be used to trigger desired morphological, neurological, physiological, and bacteriomic changes for various regenerative and bioengineering applications.
Bacteria will accompany humans in our exploration of space, making it of importance to study their adaptation to the microgravity environment. To investigate potential phenotypic changes for bacteria grown in space, Escherichia coli was cultured onboard the International Space Station with matched controls on Earth. Samples were challenged with different concentrations of gentamicin sulfate to study the role of drug concentration on the dependent variables in the space environment. Analyses included assessments of final cell count, cell size, cell envelope thickness, cell ultrastructure, and culture morphology. A 13-fold increase in final cell count was observed in space with respect to the ground controls and the space flight cells were able to grow in the presence of normally inhibitory levels of gentamicin sulfate. Contrast light microscopy and focused ion beam/scanning electron microscopy showed that, on average, cells in space were 37% of the volume of their matched controls, which may alter the rate of molecule–cell interactions in a diffusion-limited mass transport regime as is expected to occur in microgravity. TEM imagery showed an increase in cell envelope thickness of between 25 and 43% in space with respect to the Earth control group. Outer membrane vesicles were observed on the spaceflight samples, but not on the Earth cultures. While E. coli suspension cultures on Earth were homogenously distributed throughout the liquid medium, in space they tended to form a cluster, leaving the surrounding medium visibly clear of cells. This cell aggregation behavior may be associated with enhanced biofilm formation observed in other spaceflight experiments.
The Hyperspectral Imager for the Coastal Ocean (HICO) was used to derive chlorophyll-a (chl-a) based on the normalized difference chlorophyll index (NDCI) in two Gulf of Mexico coastal estuaries. Chl-a data were acquired from discrete in situ water sample analysis and above-water hyperspectral surface acquisition system (HyperSAS) remote sensing reflectance in Pensacola Bay (PB) and Choctawhatchee Bay (CB). NDCI algorithm calibrations and validations were completed on HICO data. Linear and best-fit (polynomial) calibrations performed strongly with R2 of 0.90 and 0.96, respectively. The best validation of NDCI resulted with an R2 of 0.74 and root-mean-square error (RMSE) of 1.64 µg/L. A strong spatial correspondence was observed between NDCI and chl-a, with higher NDCI associated with higher chl-a and these areas were primarily located in the northern PB and eastern CB at the river mouths. NDCI could be effectively used as a qualitative chl-a monitoring tool with a reduced need for site-specific calibration.
The application of ocean color product retrieval algorithms for pixels containing cloud shadows leads to erroneous results. Thus, shadows are an important scene type that should be identified and excluded from the set of clear-sky pixels. In this paper, we present an optical cloud shadow-detection technique called the Cloud Shadow Detection Index (CSDI). This approach is for homogeneous water bodies such as deep waters where shadow detection is very challenging due to the relatively small differences in the brightness values of the shadows and neighboring sunlit or some other regions. The CSDI technique is developed based on the small differences between the total radiances reaching the sensor from the shadowed and neighboring sunlit regions of similar optical properties by amplifying the differences through integrating the spectra of the two regions. The Integrated Value (IV) is then normalized by the mean of the IVs within a spatial adaptive sliding box where atmospheric and marine optical properties are assumed homogeneous. Assuming that the true color and the IV images represent accurate shadow locations, the results were visually compared. The CSDI images agree reasonably well with the corresponding true color and the IV images over open ocean. Also, the shape of the cloud shadow particularly for the isolated cloud closely follows that of the cloud, as expected, reconfirming the potential of the CSDI technique.
Harmful algal blooms (HABs) can lead to severe economic and ecological impacts in coastal areas and can threaten marine life and human health. About three quarters of these toxic blooms are caused by dinoflagellate species. One dinoflagellate species, i.e., Karenia brevis, blooms nearly every year in the Gulf of Mexico, particularly on the West Florida Shelf (WFS), where these blooms cause millions of dollars in socioeconomic damage. In this letter, we use the red band difference (RBD) bloom detection technique for detection of low backscattering phytoplankton blooms, such as K. brevis, and conduct time-series analyses of the spatial extent of these blooms using Moderate Resolution Imaging Spectroradiometer (MODIS) monthly mean data spanning July 2002 (sensor inception) to September 2014. The time-series results show that the RBD successfully detects the documented HABs in the region, illustrating the seasonal and interannual variability, including the extensive blooms of 2005 and 2014.
We report on the observation of new properties of secondary cosmic rays Li, Be, and B measured in the rigidity (momentum per unit charge) range 1.9 GV to 3.3 TV with a total of 5.4 × 10 6 nuclei collected by AMS during the first five years of operation aboard the International Space Station. The Li and B fluxes have an identical rigidity dependence above 7 GV and all three fluxes have an identical rigidity dependence above 30 GV with the Li / Be flux ratio of 2.0 ± 0.1 . The three fluxes deviate from a single power law above 200 GV in an identical way. This behavior of secondary cosmic rays has also been observed in the AMS measurement of primary cosmic rays He, C, and O but the rigidity dependences of primary cosmic rays and of secondary cosmic rays are distinctly different. In particular, above 200 GV, the secondary cosmic rays harden more than the primary cosmic rays.
We present the precision measurement from May 2011 to May 2017 (79 Bartels rotations) of the proton fluxes at rigidities from 1 to 60 GV and the helium fluxes from 1.9 to 60 GV based on a total of 1×109 events collected with the Alpha Magnetic Spectrometer aboard the International Space Station. This measurement is in solar cycle 24, which has the solar maximum in April 2014. We observed that, below 40 GV, the proton flux and the helium flux show nearly identical fine structures in both time and relative amplitude. The amplitudes of the flux structures decrease with increasing rigidity and vanish above 40 GV. The amplitudes of the structures are reduced during the time period, which started one year after solar maximum, when the proton and helium fluxes steadily increase. Above ∼3 GV the p/He flux ratio is time independent. We observed that below ∼3 GV the ratio has a long-term decrease coinciding with the period during which the fluxes start to rise.
We present high-statistics, precision measurements of the detailed time and energy dependence of the primary cosmic-ray electron flux and positron flux over 79 Bartels rotations from May 2011 to May 2017 in the energy range from 1 to 50 GeV. For the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. Based on 23.5×106 events, we report the observation of short-term structures on the timescale of months coincident in both the electron flux and the positron flux. These structures are not visible in the e+/e− flux ratio. The precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over 830±30 days from one value to another. The midpoint of the transition shows an energy dependent delay relative to the reversal and changes by 260±30 days from 1 to 6 GeV.
Neural EGFL like 1 (Nell-1) is essential for chondrogenic differentiation, maturation, and regeneration. Our previous studies have demonstrated that Nell-1’s pro-chondrogenic activities are predominantly reliant upon runt-related transcription factor 3 (Runx3)-mediated Indian hedgehog (Ihh) signaling. Here, we identify the nuclear factor of activated T-cells 1 (Nfatc1) as the key transcriptional factor mediating the Nell-1 → Runx3 signal transduction in chondrocytes. Using chromatin immunoprecipitation assay, we were able to determine that Nfatc1 binds to the −833–−810 region of the Runx3-promoter in response to Nell-1 treatment. By revealing the Nell-1 → Nfatc1 → Runx3 → Ihh cascade, we demonstrate the involvement of Nfatc1, a nuclear factor of activated T-cells, in chondrogenesis, while providing innovative insights into developing a novel therapeutic strategy for cartilage regeneration and other chondrogenesis-related conditions.
The Alpha Magnetic Spectrometer experiment onboard the International Space Station has recently provided cosmic ray electron and positron data with unprecedented precision in the range from 0.5 to 350 GeV. The observed rise in the positron fraction at energies above 10 GeV remains unexplained, with proposed solutions ranging from local pulsars to TeV-scale dark matter. Here, we make use of this high quality data to place stringent limits on dark matter with masses below ? 300 GeV, annihilating or decaying to leptonic final states, essentially independent of the origin of this rise. We significantly improve on existing constraints, in some cases by up to 2 orders of magnitude.
MTAN (5?-methylthioadenosine nucleosidase) catalyzes the hydrolysis of the N-ribosidic bond of a variety of adenosine-containing metabolites. The Helicobacter pylori MTAN (HpMTAN) hydrolyzes 6-amino-6-deoxyfutalosine in the second step of the alternative menaquinone biosynthetic pathway. Substrate binding of the adenine moiety is mediated almost exclusively by hydrogen bonds, and the proposed catalytic mechanism requires multiple proton-transfer events. Of particular interest is the protonation state of residue D198, which possesses a pKa above 8 and functions as a general acid to initiate the enzymatic reaction. In this study we present three corefined neutron/X-ray crystal structures of wild-type HpMTAN cocrystallized with S-adenosylhomocysteine (SAH), Formycin A (FMA), and (3R,4S)-4-(4-Chlorophenylthiomethyl)-1-[(9-deaza-adenin-9-yl)methyl]-3-hydroxypyrrolidine (p-ClPh-Thio-DADMe-ImmA) as well as one neutron/X-ray crystal structure of an inactive variant (HpMTAN-D198N) cocrystallized with SAH. These results support a mechanism of D198 pKa elevation through the unexpected sharing of a proton with atom N7 of the adenine moiety possessing unconventional hydrogen-bond geometry. Additionally, the neutron structures also highlight active site features that promote the stabilization of the transition state and slight variations in these interactions that result in 100-fold difference in binding affinities between the DADMe-ImmA and ImmA analogs.
In an effort to better understand the early stages of planet formation, we have developed a 1.5U payload that flew on the International Space Station (ISS) in the NanoRacks NanoLab facility between September 2014 and March 2016. This payload, named NanoRocks, ran a particle collision experiment under long-term microgravity conditions. The objectives of the experiment were (a) to observe collisions between mm-sized particles at relative velocities of <1~cm/s, and (b) to study the formation and disruption of particle clusters for different particle types and collision velocities. Four types of particles were used: mm-sized acrylic, glass, and copper beads, and 0.75 mm-sized JSC-1 lunar regolith simulant grains. The particles were placed in sample cells carved out of an aluminum tray. This tray was attached to one side of the payload casing with three springs. Every 60~s, the tray was agitated and the resulting collisions between the particles in the sample cells were recorded by the experiment camera. During the 18 months the payload stayed on ISS, we obtained 158 videos, thus recording a great number of collisions. The average particle velocities in the sample cells after each shaking event were around 1 cm/s. After shaking stopped, the inter-particle collisions damped the particle kinetic energy in less than 20~s, reducing the average particle velocity to below 1 mm/s, and eventually slowing them to below our detection threshold. As the particle velocity decreased, we observed the transition from bouncing to sticking collisions. We recorded the formation of particle clusters at the end of each experiment run. This paper describes the design and performance of the NanoRocks ISS payload.
Cardiomyocytes derived from human pluripotent stem cells (hPSCs) are a promising cell source for regenerative medicine, disease modeling, and drug discovery, all of which require enriched cardiomyocytes, ideally ones with mature phenotypes. However, current methods are typically performed in 2D environments that produce immature cardiomyocytes within heterogeneous populations. Here, we generated 3D aggregates of cardiomyocytes (cardiospheres) from 2D differentiation cultures of hPSCs using microscale technology and rotary orbital suspension culture. Nearly 100% of the cardiospheres showed spontaneous contractility and synchronous intracellular calcium transients. Strikingly, from starting heterogeneous populations containing ∼10%–40% cardiomyocytes, the cell population within the generated cardiospheres featured ∼80%–100% cardiomyocytes, corresponding to an enrichment factor of up to 7-fold. Furthermore, cardiomyocytes from cardiospheres exhibited enhanced structural maturation in comparison with those from a parallel 2D culture. Thus, generation of cardiospheres represents a simple and robust method for enrichment of cardiomyocytes in microtissues that have the potential use in regenerative medicine as well as other applications.
The International Space Station (ISS) National Laboratory is dedicated to studying the effects of space on life and physical systems, and to developing new science and technologies for space exploration. A key aspect of achieving these goals is to operate the ISS National Lab more like an Earth-based laboratory, conducting complex end-to-end experimentation, not limited to simple microgravity exposure. Towards that end NASA developed a novel suite of molecular biology laboratory tools, reagents, and methods, named WetLab-2, uniquely designed to operate in microgravity, and to process biological samples for real-time gene expression analysis on-orbit. This includes a novel fluidic RNA Sample Preparation Module and fluid transfer devices, all-in-one lyophilized PCR assays, centrifuge, and a real-time PCR thermal cycler. Here we describe the results from the WetLab-2 validation experiments conducted in microgravity during ISS increment 47/SPX-8. Specifically, quantitative PCR was performed on a concentration series of DNA calibration standards, and Reverse Transcriptase-quantitative PCR was conducted on RNA extracted and purified on-orbit from frozen Escherichia coli and mouse liver tissue. Cycle threshold (Ct) values and PCR efficiencies obtained on-orbit from DNA standards were similar to Earth (1 g) controls. Also, on-orbit multiplex analysis of gene expression from bacterial cells and mammalian tissue RNA samples was successfully conducted in about 3 h, with data transmitted within 2 h of experiment completion. Thermal cycling in microgravity resulted in the trapping of gas bubbles inside septa cap assay tubes, causing small but measurable increases in Ct curve noise and variability. Bubble formation was successfully suppressed in a rapid follow-up on-orbit experiment using standard caps to pressurize PCR tubes and reduce gas release during heating cycles. The WetLab-2 facility now provides a novel operational on-orbit research capability for molecular biology and demonstrates the feasibility of more complex wet bench experiments in the ISS National Lab environment.
Mechanical unloading in microgravity is thought to induce tissue degeneration by various mechanisms, including inhibition of regenerative stem cell differentiation. To address this hypothesis, we investigated the effects of microgravity on early lineage commitment of mouse embryonic stem cells (mESCs) using the embryoid body (EB) model of tissue differentiation. We found that exposure to microgravity for 15 days inhibits mESC differentiation and expression of terminal germ layer lineage markers in EBs. Additionally, microgravity-unloaded EBs retained stem cell self-renewal markers, suggesting that mechanical loading at Earth's gravity is required for normal differentiation of mESCs. Finally, cells recovered from microgravity-unloaded EBs and then cultured at Earth's gravity showed greater stemness, differentiating more readily into contractile cardiomyocyte colonies. These results indicate that mechanical unloading of stem cells in microgravity inhibits their differentiation and preserves stemness, possibly providing a cellular mechanistic basis for the inhibition of tissue regeneration in space and in disuse conditions on earth.
The past decade has seen an explosion of research directed toward better understanding of the mechanisms of mesenchymal stem/stromal cell (MSC) function during rescue and repair of injured organs and tissues. In addition to delineating cell?cell signaling and molecular controls for MSC differentiation, the field has made particular progress in defining several other mechanisms through which administered MSCs can promote tissue rescue/repair. These include: 1) paracrine activity that involves secretion of proteins/peptides and hormones; 2) transfer of mitochondria by way of tunneling nanotubes or microvesicles; and 3) transfer of exosomes or microvesicles containing RNA and other molecules. Improved understanding of MSC function holds great promise for the application of cell therapy and also for the development of powerful cell-derived therapeutics for regenerative medicine. Focusing on these three mechanisms, we discuss MSC-mediated effects on immune cell responses, cell survival, and fibrosis and review recent progress with MSC-based or MSC-derived therapeutics.
It is known that polymer films can degrade as a result of space environmental expose, but the magnitude of the mechanical property degradation and the degree to which the different environmental factors play a role is not well understood. An experiment was flown on the Materials International Space Station Experiment 5 to determine the change in tensile strength and percent elongation of some typical polymer films exposed in a nadir-facing environment on the International Space Station and, where possible, compare with similar ram- and wake-facing experiments flown on the Materials International Space Station Experiment 1 to get a better indication of the role the different environments play in mechanical property change.
Muscle loading is important for maintaining muscle mass; when load is removed, atrophy is inevitable. However, in clinical situations such as critical care myopathy, masticatory muscles do not lose mass. Thus, their properties may be harnessed to preserve mass. We compared masticatory and appendicular muscles responses to microgravity, using mice aboard the space shuttle Space Transportation System-135. Age- and sex-matched controls remained on the ground. After 13 days of space flight, 1 masseter (MA) and tibialis anterior (TA) were frozen rapidly for biochemical and functional measurements, and the contralateral MA was processed for morphologic measurements. Flight TA muscles exhibited 20 ± 3% decreased muscle mass, 2-fold decreased phosphorylated (P)-Akt, and 4- to 12-fold increased atrogene expression. In contrast, MAs had no significant change in mass but a 3-fold increase in P-focal adhesion kinase, 1.5-fold increase in P-Akt, and 50–90% lower atrogene expression compared with limb muscles, which were unaltered in microgravity. Myofibril force measurements revealed that microgravity caused a 3-fold decrease in specific force and maximal shortening velocity in TA muscles. It is surprising that myofibril-specific force from both control and flight MAs were similar to flight TA muscles, yet power was compromised by 40% following flight. Continued loading in microgravity prevents atrophy, but masticatory muscles have a different set point that mimics disuse atrophy in the appendicular muscle.—Philippou, A., Minozzo, F. C., Spinazzola, J. M., Smith, L. R., Lei, H., Rassier, D. E., Barton, E. R. Masticatory muscles of mouse do not undergo atrophy in space.
Skeletal muscle has the remarkable ability to adapt to changes in workload. Numerous muscle properties can be modulated, including muscle mass, contractile properties, and metabolism. Changes in patterns of gene expression and shifts in the balance between protein synthesis and degradation are required for adaptational responses. How well the existing properties meet the demands on the tissue is coordinated by mechanical, chemical, and metabolic information to instigate the process of muscle adaptation. Identification of major pathways that directly regulate gene expression and protein synthesis/degradation demonstrate that multiple inputs can converge on final common pathways for muscle adaptation. Understanding the contribution of the wide variety of inputs on muscle adaptation has been challenging. Skeletal muscle mass generally is regulated by a dynamic balance between protein synthesis and degradation and a vital equilibrium between the signals driving these processes (1, 2).
In skeletal muscle, sensors of mechanical loading are situated in the sarcolemma tethering the intracellular cytoskeleton to the extracellular matrix. Specifically, two major protein complexes—the focal adhesion complex and the dystrophin glycoprotein complex—are important for sensing mechanical stress at the membrane and are thought to coordinate the balance between muscle growth and atrophy (3–5). Both complexes transmit mechanical information to the cell nucleus via their association with specific nonreceptor protein tyrosine kinases such as focal adhesion kinase (FAK) (6). Phosphorylation of FAK affects its association with other signaling proteins, leading to the activation of the Ras-Raf-MEK-ERK pathway, as well as the phosphatidylinositol 3-kinase-Akt pathway, through which FAK mediates its signaling to promote muscle cell survival and muscle mass maintenance (7).
In response to reduction of external mechanical loading, including disuse and microgravity, the dynamic balance is shifted in favor of protein degradation over synthesis (2, 8–10). Systematic muscle protein degradation occurs by the activation of muscle-specific ubiquitin ligases, most prominently Atrogin-1 (MaFbx) and muscle ringer finger-1 (MuRF-1) (11, 12). The expression of progrowth genes is down-regulated simultaneously (13–15).
In the microgravity environment of space flight, absence of weight bearing has detrimental effects on skeletal muscle, including reprogramming of the expression pattern of various genes related to muscle growth/atrophy, transformation of muscle fiber types, and mass reduction (16–18). Most of these previous studies on mice subjected to microgravity have focused on limb muscles, where much has been revealed regarding adaptational responses of appendicular muscle to lack of external load. A differential response may occur in masticatory muscles, which has not been addressed. We have reported previously clear differences in terms of loading signals between the masseters (MAs) and limb muscles (19). Further, in clinical situations where there is severe muscle wasting, as seen in patients with acute quadriplegic myopathy in the intensive care unit, the masticatory muscles are spared. This suggests these muscles are equipped with a different load sensing program than limb muscles (20, 21). Animal models for acute quadriplegic myopathy recapitulate the protection against atrophy in MA muscles in stark contrast to the muscle atrophy in the rest of the body (22, 23). These studies raise the possibility that masticatory muscles have a unique loading set point and that they do not respond to unloading in the same manner as appendicular muscles.
In the current study, we compared the signaling, expression, and functional responses of appendicular versus masticatory muscles to the microgravity environment of space flight. We obtained tibialis anterior (TA) and MA muscles from mice subjected to microgravity and age- and sex-matched ground controls on the last space shuttle mission, Space Transportation System (STS)-135, of the National Aeronautics and Space Administration (NASA). To evaluate the loading response thoroughly, we also compared the responses of the masticatory muscles in mice subjected to a liquid diet, which eliminates the loading from normal chewing but still affords muscle movement and activity. We hypothesized that the loading of MA muscles comes in part from normal chewing activity, and therefore the mouse MAs may be spared from atrophy in the weightlessness environment, yet they would still succumb to atrophy on a liquid diet.
Deregulation in uterine contractility can cause common pathological disorders of the female reproductive system, including preterm labor, infertility, inappropriate implantation, and irregular menstrual cycle. A better understanding of human myometrium contractility is essential to designing and testing interventions for these important clinical problems. Robust studies on the physiology of human uterine contractions require in vitro models, utilizing a human source. Importantly, uterine contractility is a three-dimensionally (3D)-coordinated phenomenon and should be studied in a 3D environment. Here, we propose and assess for the first time a 3D in vitro model for the evaluation of human uterine contractility. Magnetic 3D bioprinting is applied to pattern human myometrium cells into rings, which are then monitored for contractility over time and as a function of various clinically relevant agents. Commercially available and patient-derived myometrium cells were magnetically bioprinted into rings in 384-well formats for throughput uterine contractility analysis. The bioprinted uterine rings from various cell origins and patients show different patterns of contractility and respond differently to clinically relevant uterine contractility inhibitors, indomethacin and nifedipine. We believe that the novel system will serve as a useful tool to evaluate the physiology of human parturition while enabling high-throughput testing of multiple agents and conditions.
Viscous fingering (VF) is an interfacial hydrodynamic instability phenomenon observed when a fluid of lower viscosity displaces a higher viscous one in a porous media. In miscible viscous fingering, the concentration gradient of the undergoing fluids is an important factor, as the viscosity of the fluids are driven by concentration. Diffusion takes place when two miscible fluids are brought in contact with each other. However, if the diffusion rate is slow enough, the concentration gradient of the two fluids remains very large during some time. Such steep concentration gradient, which mimics a surface tension type force, called the effective interfacial tension, appears in various cases such as aqua-organic, polymer-monomer miscible systems, etc. Such interfacial tension effects on miscible VF is modeled using a stress term called Korteweg stress in the Darcy's equation by coupling with the convection-diffusion equation of the concentration. The effect of the Korteweg stresses at the onset of the instability has been analyzed through a linear stability analysis using a self-similar Quasi-steady-state-approximation (SS-QSSA) in which a self-similar diffusive base state profile is considered. The quasi-steady-state analyses available in literature are compared with the present SS-QSSA method and found that the latter captures appropriately the unconditional stability criterion at an earlier diffusive time as well as in long wave approximation. The effects of various governing parameters such as log-mobility ratio, Korteweg parameters, disturbances' wave number, etc., on the onset of the instability are discussed for, (i) the two semi-infinite miscible fluid zones and (ii) VF of the miscible slice cases. The stabilizing property of the Korteweg stresses effect is observed for both of the above mentioned cases. Critical miscible slice lengths are computed to have the onset of the instability for different governing parameters with or without Korteweg stresses. These stabilizing properties of the Korteweg stresses captured in this present study are in agreement with the numerical simulations of fully nonlinear problem and the experimental observations reported in the literature.