Microgravity alters key biological processes, impacting cellular structure, function, and metabolism. In the absence of gravity, cells experience changes that disrupt signal transduction, gene expression, and metabolic pathways, affecting growth rates and cellular viability. Ground-based simulators like clinostats replicate microgravity conditions to study these effects, allowing researchers to examine cellular responses in the lab. This study uses Saccharomyces cerevisiae to explore microgravity's impact on yeast metabolism and properties. Yeast cells are exposed to simulated microgravity via a 2D-clinostat and analyzed using dielectrophoresis over 1-24 h. A double-shell model reveals significant morphological and membrane changes under these conditions. Results indicate notable differences in membrane permittivity and conductivity, with microgravity reducing the folding factor in yeast cells, impairing nutrient uptake and energy production. This research enhances the understanding of microgravity's effects on eukaryotic cells and contributes to the field of gravitational biology.
Maxillofacial fractures, especially those of the mandible, pose a significant risk in microgravity environments because astronauts experience progressive bone loss during long-duration flights because of skeletal unloading. In this study, we explored the biomechanical response of the mandibular angle to high-impact trauma caused by gravity and microgravity. A human mandibular model was subjected to a force of 2000 N at an angle of 45°, which was directed posterosuperiorly at the right-angle region with simulations comparing healthy and osteoporotic bone (bone loses its density in long flights due to skeletal unloading). The results revealed that although stresses remained the same across all conditions, microgravity caused nearly double the strain and deformation, indicating a high risk of fracture. These findings emphasize the need for biomechanical evaluation and protective strategies in space medicine.
As resident immune cells of the central nervous system, microglia exhibit inherent responsiveness to external stimuli and insults. In this study, we demonstrated that a simulated microgravity conditions induces pro-inflammatory activation of BV2 microglial cells, a process tightly regulated by the RhoA GTPase Arhgap18. Specifically, the downregulation of Arhgap18 under simulated microgravity was identified as the upstream mechanism driving microglial activation and triggering neuroinflammation via the Arhgap18/RhoA/ROCK signaling pathway. For in vivo validation, we established a 21-day hindlimb unloading (HU) mouse model, which confirmed that simulated microgravity promotes pro-inflammatory microglial activation in the cerebral cortex and hippocampus. Furthermore, co-culture of N2a neural cells with pro-inflammatory microglia led to distinct morphological alterations in N2a cells and a significant downregulation of synaptic plasticity-related proteins-effects that were recapitulated in the HU mouse model. Collectively, these findings suggest that microgravity may mediate changes in neuronal synaptic plasticity by activating the inflammatory response of microglia.
Adolescent Idiopathic Scoliosis (AIS) progresses via excessive concave-endplate compressive stress and PIEZO1 overexpression-induced vertebral growth plate chondrocyte degeneration. Though microgravity-mediated mechanical unloading is traditionally linked to musculoskeletal harm, we explored its therapeutic potential for AIS. We integrated clinical observations, in vivo models, and in vitro experiments: Clinical anti-gravity skull traction (mechanical unloading) reduced a severe AIS patient's Cobb angle. In a scoliosis mouse model, 10 h/day traction suspension delayed deformity. In vitro, 100 kPa pressure overload upregulated PIEZO1 in chondrocytes, while simulated microgravity reversed this, inhibiting ossification and matrix degeneration. Mouse tail compression elevated PIEZO1 and accelerated ossification, which tail suspension reversed. PIEZO1 agonist Yoda1 promoted chondrocyte osteogenic differentiation, confirming PIEZO1's pathological role. This study shows simulated microgravity-mediated mechanical unloading alleviates AIS by inhibiting PIEZO1, repurposing microgravity from a "pathological factor" to a non-invasive AIS therapy, bridging aerospace medicine and orthopedics.
The growth of compositionally uniform InAs1-xSbx bulk crystals remains a formidable challenge due to severe solute segregation and morphological instability under terrestrial conditions. Here, we report the successful growth of a single-crystalline InAs0.933Sb0.067 alloy (x = 6.7 mol%) on an InAs seed via the vertical gradient freeze method aboard the China Space Station. Crucially, microgravity enables diffusion-dominated solidification by suppressing buoyancy-driven convection. As a direct consequence, the crystal is free of macroscopic voids and striations, exhibits a tenfold reduction in dislocation density, and maintains Sb compositional uniformity (±0.5 mol%) over its entire ~11 mm diameter and ~2.5 mm growth length. Moreover, the microgravity-grown crystal outperforms its terrestrial counterpart in both crystalline quality and electrical properties. These findings highlight that microgravity provides a unique pathway to overcome the intrinsic limitations of ground-based growth, enabling crystal quality unattainable on Earth - with potential relevance to advanced optoelectronic applications.
This pioneering study investigated cardiovascular responses in children during simulated microgravity exposure using a 15° head-down tilt (HDT) for one hour. Twenty-six healthy participants aged 8-14 years (15 girls, 11 boys) underwent continuous non-invasive monitoring of nine cardiovascular parameters, including heart rate, stroke volume, cardiac output, and blood pressure. Results showed that children tolerated HDT well, with no signs of distress or adverse reactions. Heart rate decreased significantly during tilt, while stroke volume and left ventricular ejection time increased, suggesting adaptive cardiovascular adjustments similar to those observed in adults under microgravity conditions. Cardiac output and cardiac index exhibited transient rises in girls, followed by normalization, and no significant intersex differences were found in blood pressure responses. These findings indicate that children display physiological adaptability comparable to adults, providing novel insights into pediatric cardiovascular function in microgravity analogs and supporting considerations for future inclusion of young participants in space research and tourism.
Airborne transmission is one of the most efficient routes of respiratory viral spread, posing a significant challenge in controlling major infectious diseases such as COVID-19. In microgravity environments, such as the International Space Station (ISS), this mode of transmission requires heightened vigilance and preventive measures due to the prolonged suspension of virus-laden particles, which increases the risk of infection. Using the COVID Airborne Risk Assessment (CARA) tool, we assess the risk of airborne transmission of respiratory viruses, using SARS-CoV-2 as a case study, in microgravity by simulating the emission, dispersion, and inhalation of virus-laden particles. Our simulations show that the unique conditions of microgravity allow these particles to remain airborne for more extended periods compared to Earth, leading to a 286-fold increase in virus concentration in the air and resulting in nearly twice the probability of infection for a susceptible host. We also evaluated the effectiveness of preventive measures. We found that facemasks could reduce the risk by up to 23%, while continuous HEPA filtration at five air changes per hour proves crucial for managing air quality and minimizing infection risks by reducing airborne virus concentration by 99.79%. To explore potential effects of spaceflight-induced immune suppression on transmission risk, we modeled hypothetical scenarios with increased viral shedding based on herpesvirus reactivation data. An 8-fold increase in viral load (as observed for herpesviruses in space) raised infection probability by 12 percentage points above baseline. Sensitivity analysis with 4-fold and 16-fold increases showed infection risk scales proportionally with viral shedding intensity. Although facemasks and air filtration help mitigate the risk, their effectiveness diminishes when viral load is elevated. Enhancing host immunity through vaccination or other interventions is vital, potentially reducing infection probability by up to 14.17% when combined with HEPA filtration.
Prolonged space missions expose astronauts to microgravity and cosmic radiation, leading to persistent vascular dysfunction driven by oxidative stress, cardiac deconditioning, and reduced physical activity. Current therapies are limited by adverse effects such as hypertension, hyperkalemia, and poor bioavailability, with no effective countermeasures targeting oxidative and endothelial-specific damage. Here, we present a multifunctional zein nanocage-based therapeutic formulation (ZNT) that encapsulates a remedial cocktail designed to mitigate oxidative stress and protect cardiovascular health under simulated microgravity conditions. In vitro studies on endothelial cells have revealed that microgravity induces reactive oxygen species generation, mitochondrial membrane depolarization, oxidative DNA damage, and apoptosis. These changes were accompanied by elevated nitric oxide production and aberrant expression of angiogenesis-related genes, including VEGFA, HIF-1α, eNOS, iNOS, FGF-2, and ANG1. Treatment with ZNT restored redox balance, preserved mitochondrial integrity, prevented DNA damage and apoptosis, and normalized angiogenic gene expression. These protective effects were further validated in vivo using zebrafish larvae and chick embryo models. By addressing both oxidative stress and pathological angiogenesis, ZNT emerges as a promising nanotherapeutic strategy to safeguard cardiovascular function during and after spaceflight, potentially filling a critical gap in astronaut healthcare.
Experiments conducted onboard the International Space Station help investigate the physiological changes that living organisms undergo in microgravity. On Earth, the two-axis clinostat serves as an alternative that can continuously change the direction of gravity and simulate microgravity conditions by time-averaging the gravity vector. However, its structural characteristics inevitably produce poles where gravity is unevenly concentrated. This study conducted a quantitative analysis and comparison of pole formation across four representative clinostat control strategies. To evaluate the poles, two quantitative indicators were defined. The commonly used control strategies, maintaining a constant angular velocity or following a random distribution, were found to induce severe poles. In contrast, when the angular velocity of the external motor followed a specifically designed reciprocal sinusoidal profile, pole formation could be significantly reduced by adjusting the ratio between the minimum and maximum angular velocities. These trends, identified through simulations, were further validated through experiments using an inertial measurement unit.
Space missions require sustainable life support systems capable of producing oxygen and biomass under microgravity. We report the use of acoustic levitation to trap and manipulate the filamentous cyanobacterium Limnospira indica PCC 8005 during parabolic flights. Within a millimeter-scale fluidic chamber, this helical microorganism rapidly assembles into thin layers under a standing ultrasonic wave. Stable trapping in microgravity requires substantially less acoustic power (0.42 mW) than on Earth (1.4 mW), highlighting the potential for energy-efficient bioprocessing in space. Monte Carlo simulations and light attenuation modeling show that layered structuring enhances light penetration, potentially overcoming the "compensation point" limitation in bulk cultures. These findings open new perspectives for photobioreactors using acoustic manipulation to boost photosynthetic efficiency and reduce energy demands for oxygen and biomass production in space.
Microgravity significantly impacts astronaut physiology, causing accelerated bone loss and impairing bone regeneration. As human space exploration expands, effective and minimally invasive bone repair treatments are crucial. In this study, we investigated the regenerative potential of a novel mineral-organic bone adhesive, Tetranite® (TN), compared to the osteoinductive rhBMP2 (Infuse®). We used a critical-size calvarial bone defect model in mice, with half launched on a 60-day mission to the International Space Station and the other half serving as ground controls. Histological and quantitative micro-computed tomography (MicroCT) analyses confirmed that both TN and rhBMP2 promoted bone regeneration in both spaceflight and ground conditions. While both biomaterials were effective, TN's regenerative effect was more localized to the defect site. Our findings demonstrate that TN implantation effectively promotes calvarial bone regeneration under both microgravity and terrestrial conditions. This suggests its potential as a minimally invasive clinical solution for treating bone fractures during future space missions and on Earth.
This study reports a new method of analysis to measure the surface tension of high melt-temperature liquid metals using levitation in microgravity. The method, which leads to a self-consistent benchmarking technique to determine surface tension, requires forced oscillations of a levitated drop until the drop responds by deforming at a target mode, say the first fundamental mode of the natural frequency of the drop. Decomposition of the drop shape into Legendre modes, followed by time-domain analysis, reveals that the response to a target-mode forcing is composed of multiple modes that oscillate at frequencies, commensurate with the natural frequencies of those modes. We refer to the multiple modes that emanate from the target mode forcing as subordinate or ancillary modes. This then means that multiple modal shapes constituting the deforming drop's response co-exist. It is found that the ratios of the experimentally determined ancillary modal frequencies correlate well with the theoretical ratios predicted by the Rayleigh formula, thereby providing a self-consistent benchmark method for surface tension determination for any given sample, regardless of its composition. Validation of this method has been performed using experiments on the Electrostatic Levitation Furnace (ELF) in the KIBO module aboard the International Space Station (ISS) demonstrating accuracy and precision.
Microgravity strongly affects human physiology during spaceflight. Biological sex has not yet been sufficiently considered as a variable for spaceflight deconditioning. The VivalDI studies investigated physiological systems affected by 5-days dry immersion (DI) in females and males, with a focus on immune changes in this report. In both sexes proportions of peripheral granulocytes and NK cells were elevated during DI and T-cell numbers were reduced. Leukocyte activation and cytokine levels were moderately affected. Females showed a higher Torque-Teno-virus shedding at the end of DI. Noradrenaline concentrations increased during the study with sex-specific patterns. Hemodynamics suggest that immunological changes were caused by DI-induced fluid shifts. Moreover, male study participants' patterns were compared to a historical data set from a 5-days head-down-tilt bed rest (HDT-BR) study. Changes in leukocyte proportions and body fluid indicators were stronger in DI versus HDT-BR. These analyses indicate that fluid shifts primarily drive intervention-related immune-physiological differences, independent of biological sex. ClinicalTrials.gov, TRN: NCT05043974 and NCT05493176.
Long-duration spaceflight produces structural, functional, and hemodynamic brain changes driven by microgravity, radiation, elevated CO2, and isolation. Consequences include Spaceflight-Associated Neuro-Ocular Syndrome, vestibular imbalance, orthostatic intolerance, and cognitive disturbance. We consolidate current evidence, present a cerebrovascular physiologic framework, and discuss emerging countermeasures-including lower body negative pressure, artificial gravity, advanced neuromonitoring, and synthetic torpor-needed to safeguard neurological health on exploration-class missions.
Understanding thermophysical properties such as surface tension (σ), total hemispherical emissivity (ε), specific heat capacity (cp) and viscosity (η) as a function of temperature is essential for optimizing the vitrification of bulk metallic glasses (BMGs). In this study, the thermophysical properties of liquid Vit106a were measured aboard the International Space Station (ISS) using the electromagnetic levitator (EML). The surface tension σ exhibited a similar value with other Zr-based BMG, with a weak temperature dependence described by σ(T) = 1.557-4.36 ×10-5 × (T - 1106) N.m-1. The viscosity temperature-dependence η(T) was analyzed using the Vogel-Fulcher-Tammann (VFT) equation, yielding a kinetic fragility parameter of D* = 9.8 at high temperature, compared to D* = 21.6 at low temperature, that indicates a fragile-to-strong transition characteristic of Zr-based metallic glass formers. XRD analysis confirms full crystallization of the sample, despite being cooled at a rate of 16 K.s⁻¹, over nine times faster than the critical cooling rate of 1.75 K.s⁻¹ reported in the literature. The crystallized sample reveals a heterogeneous distribution of binary intermetallic phases, including ZrAl3, Zr2Cu, Zr2Ni, ZrAl and Nb2Ni. These findings provide insights into the thermophysical behavior of liquid Vit106a for large-scale manufacturing but also raise important questions regarding its good glass-forming ability for larger casting thickness.
Even a minor increase in core body temperature (CBT) raises physiological challenges in astronauts, leading to a decline in physical and cognitive performance. This study aims to systematically review and summarize existing literature on the effects of spaceflight or its simulations on human thermoregulation. This systematic review was performed according to the PRISMA guidelines and Space Biomedicine Systematic Review methods. The search was performed using three databases: PubMed, Web of Science, and Cochrane Library. During the database search, 832 studies were identified. A total of 20 studies were included in the systematic review (spaceflight exposure: 6 studies, bed rest: 14 studies). One of the primary observations from spaceflight studies was the elevation of CBT during prolonged missions. The observed increase in CBT has been attributed to multiple factors, including disruptions in circadian regulation, changes in the immune system, and reduced evaporative cooling due to altered sweating responses. Five of the spaceflight simulation studies show an increase in the CBT after bed rest, and no change was observed in 3 studies. To mitigate risks associated with the dysregulated thermoregulatory system, future studies analyzing the integration of advanced monitoring technologies, personalized thermal management strategies, and evidence-based countermeasures are needed.
Spaceflight acutely but transiently elevates intraocular pressure (IOP), often attributed to cephalad fluid shift and choroidal expansion. We propose that anterior segment mechanics, including lens-iris diaphragm position and conventional outflow loading, may contribute to early IOP changes. Comparing phakic and pseudophakic eyes, paired with anterior segment OCT and complementary imaging aboard the International Space Station, could define mechanisms and inform astronaut screening and ocular risk mitigation.
Expanding human space exploration necessitates technologies for sustainable local resource acquisition, to overcome unviable resupply missions. Asteroids, some of which rich in metals like platinum group elements, are promising targets. The BioAsteroid experiment aboard the International Space Station tested the use of microorganisms (bacteria and fungi) to extract 44 elements from L-chondrite asteroidal material under microgravity. Penicillium simplicissimum enhanced the release of palladium, platinum and other elements in microgravity, compared to non-biological leaching. For many elements, non-biological leaching was more effective in microgravity than on Earth, while bioleaching remained stable. Metabolomic analysis revealed distinct changes in microbial metabolism in space, particularly for P. simplicissimum, with increased production of carboxylic acids, and molecules of potential biomining or pharmaceutical interest in microgravity. These results demonstrate the impact of microgravity on bioleaching, highlighting the need for optimal combination of microorganisms, rock substrate, and conditions for successful biomining, in space and Earth.
With the recent rise in the numbers and diversity of astronauts and space travelers, health and prevention of illness in space are of primary importance. Changes in immune function among astronauts during spaceflight have been reported, but gaps remain in understanding how this may translate to increases in an in-flight risk of infection. To understand how immunity and infection are affected by microgravity, we used the nematode Caenorhabditis elegans as an animal host-pathogen model. Worms exposed to either space or simulated microgravity for several days exhibited increased Enterobacter gut colonization compared to normal gravity on Earth. Bacterial susceptibility was more severe in immunocompromised mutants of the pmk-1 gene, a conserved p38 MAPK ortholog that regulates innate immunity. RNA sequencing analysis identified several immune effector genes regulated by microgravity through MAPK/PMK-1. Silencing these genes via RNA interference identified specific immune effectors that protect C. elegans against increased Enterobacter gut proliferation, while transgenic expression of one of these effectors prevented increased colonization in immunocompromised C. elegans in microgravity. This study underscores the importance of the conserved MAPK/PMK-1 innate immune pathway in providing protection against possible infection during spaceflight.
Future long-duration space missions will require in-situ, on-demand manufacturing of tools and components. Photopolymer-based processes are attractive for this purpose due to their low energy requirements, volume efficiency, and precise control of curing. However, photopolymerization generates significant heat, which is difficult to regulate in microgravity where natural convection is absent, leading to defects such as surface blistering and deformation. In this work, we combine experimental studies and modeling to address these thermal challenges. We report results from International Space Station (ISS) experiments and a dedicated parabolic flight campaign, which confirm that suppressed convective heat transfer in microgravity exacerbates thermal buildup and defect formation. Building on these observations, we present a predictive thermal model that couples heat transfer, light absorption, and evolving material properties to simulate polymerization and temperature evolution under terrestrial and microgravity conditions. Laboratory validation demonstrates strong agreement between model predictions and measured temperature profiles. Applying the model to the ISS experiments, we show that the model accurately reproduces experimentally observed blistering in TJ-3704A, a commercial acrylate-based polymer resin, while also predicting defect-free outcomes for Norland optical adhesives. The model functions as a design tool for defect-free in-space manufacturing, enabling the selection of polymer properties, exposure strategies, and environmental conditions that together inhibit excess thermal buildup, paving the way for scalable, reliable in-situ manufacturing during future missions.