Prolonged exposure to simulated microgravity promotes stemness impairing morphological, metabolic and migratory profile of pancreatic cancer cells: a comprehensive proteomic, lipidomic and transcriptomic analysis.

BACKGROUND: The impact of the absence of gravity on cancer cells is of great interest, especially today that space is more accessible than ever. Despite advances, few and contradictory data are available mainly due to different setup, experimental design and time point analyzed. METHODS: Exploiting a Random Positioning Machine, we dissected the effects of long-term exposure to simulated microgravity (SMG) on pancreatic cancer cells performing proteomic, lipidomic and transcriptomic analysis at 1, 7 and 9 days. RESULTS: Our results indicated that SMG affects cellular morphology through a time-dependent activation of Actin-based motility via Rho and Cdc42 pathways leading to actin rearrangement, formation of 3D spheroids and enhancement of epithelial-to-mesenchymal transition. Bioinformatic analysis reveals that SMG may activates ERK5/NF-κB/IL-8 axis that triggers the expansion of cancer stem cells with an increased migratory capability. These cells, to remediate energy stress and apoptosis activation, undergo a metabolic reprogramming orchestrated by HIF-1α and PI3K/Akt pathways that upregulate glycolysis and impair ß-oxidation, suggesting a de novo synthesis of triglycerides for the membrane lipid bilayer formation. CONCLUSIONS: SMG revolutionizes tumor cell behavior and metabolism leading to the acquisition of an aggressive and metastatic stem cell-like phenotype. These results dissect the time-dependent cellular alterations induced by SMG and pave the base for altered gravity conditions as new anti-cancer technology.

Alteration in facial skin blood flow during acute exposure to -10 and -30° head-down tilt in young human volunteers.

NEW FINDINGS: What is the central question of this study? Facial skin blood flow (SBF) might increase during head-down tilt (HDT). However, the effect of HDT on facial SBF remains controversial. In addition, the changes in facial SBF in the cheek (cheek SBF) during a steeper angle of HDT (>-12° HDT) have not been investigated. What is the main finding and its importance? This study showed that cheek SBF decreased during -30° HDT, alongside increased vascular resistance. Furthermore, vascular impedance was suggested to be elevated, accompanied by an increased hydrostatic pressure gradient caused by HDT. Constriction of the facial skin vascular bed and congestion of venous return owing to the steep angle of HDT can decrease facial SBF. ABSTRACT: Head-down tilt (HDT) has been used to simulate microgravity in ground-based studies and clinical procedures including the Trendelenburg position or in certain surgical operations. Facial skin blood flow (SBF) might be altered by HDT, but the effect of a steeper angle of HDT (>-12° HDT) on facial SBF remains unclear. We examined alterations in facial SBF in the cheek (cheek SBF) using two different angles (-10 and -30°) of HDT and lying horizontal (0°) in a supine position for 10 min, to test the hypothesis that cheek SBF would increase with a steeper angle of HDT. Cheek SBF was measured continuously by laser Doppler flowmetry. Cheek skin vascular resistance and the pulsatility index of cheek SBF were calculated to assess the circulatory effects on the facial skin vascular bed in the cheek. Cheek SBF decreased significantly during -30° HDT. In addition, the resistance in cheek SBF increased significantly during -30° HDT. The pulsatility index of cheek SBF increased during both -10 and -30° HDT. Contrary to our hypothesis, cheek SBF decreased during -30° HDT along with increased skin vascular resistance. Vascular impedance, estimated by the pulsatility index in the cheek SBF, was elevated during both -10 and -30° HDT, and elevated vascular impedance would be related to increased hydrostatic pressure induced by HDT. Skin vascular constriction and venous return congestion would be induced by -30° HDT, leading to deceased cheek SBF. The present study suggested that facial SBF in the cheek decreased during acute exposure to a steep angle of HDT (∼-30° HDT).

Mitochondrial Respiration in Drosophila Ovaries after a Full Cycle of Oogenesis under Simulated Microgravity.

Studies of the function of the female reproductive system in zero gravity are urgent for the future exploration of deep space. Female reproductive cells, oocytes, are rich in mitochondria, which allow oocytes to produce embryos. The rate of cellular respiration was determined to assess the functional state of the mitochondrial apparatus in Drosophila melanogaster ovaries in which the full cycle of oogenesis took place under simulated microgravity. Since cellular respiration depends on the state of the cytoskeleton, the contents of the main cytoskeletal proteins were determined by Western blotting. To modulate the structure of the cytoskeleton, essential phospholipids were administered per os at a dosage of 500 mg/kg in medium. The results of this study show that after a full cycle of oogenesis under simulated microgravity, the rate of cellular respiration in the fruit fly ovaries increases, apparently due to complex II of the respiratory chain. At the same time, we did not find any changes in the area of oocytes or in the content of proteins in the respiratory chain. However, changes were found in the relative contents of proteins of the actin cytoskeleton. There were no changes of essential phospholipids and no increase in the rate of cellular respiration of the ovaries after exposure to simulated microgravity. However, in the control, the administration of essential phospholipids led to a decrease in the efficiency of oxygen consumption in the flies' ovaries due to complexes IV-V.

Simulated microgravity accelerates aging of human skeletal muscle myoblasts at the single cell level.

Earth's gravity is essential for maintaining skeletal muscle mass and function in the body. The role of gravity in the myogenic mechanism has been studied with animal experiments in the International Space Station. Recently, gravity-control devices allow to study the effects of gravity on cultured cells on the ground. This study demonstrated that simulated microgravity accelerated aging of human skeletal muscle myoblasts in an in-vitro culture. The microgravity culture induced a significant decrease in cell proliferation and an enlargement of the cytoskeleton and nucleus of cells. Similar changes are often observed in aged myoblasts following several passages. In fact, by the microgravity culture the expression of senescence associated ß-Gal was significantly enhanced, and some muscle-specific proteins decreased in the enlarged cells. Importantly, these microgravity effects remained with the cells even after a return to normal gravity conditions. Consequently, the microgravity-affected myoblasts demonstrated a reduced capability of differentiation into myotubes. In the body, it is difficult to interpret the disability of microgravity-affected myoblasts, since muscle regeneration is linked to the supply of new myogenic cells. Therefore, our in-vitro cell culture study will be advantageous to better understand the role of each type of myogenic cell in human muscle without gravitational stress at the single cell level.

Simulated microgravity disturbs iron metabolism and distribution in humans: Lessons from dry immersion, an innovative ground-based human model.

The objective of the present study was to determine the effects of dry immersion, an innovative ground-based human model of simulated microgravity and extreme physical inactivity, on iron homeostasis and distribution. Twenty young healthy men were recruited and submitted to 5 days of dry immersion (DI). Fasting blood samples and MRI were performed before and after DI exposure to assess iron status, as well as hematological responses. DI increased spleen iron concentrations (SIC), whereas hepatic iron store (HIC) was not affected. Spleen iron sequestration could be due to the concomitant increase in serum hepcidin levels (P < .001). Increased serum unconjugated bilirubin, as well as the rise of serum myoglobin levels support that DI may promote hemolysis and myolysis. These phenomena could contribute to the concomitant increase of serum iron and transferrin saturation levels (P < .001). As HIC remained unchanged, increased serum hepcidin levels could be due both to higher transferrin saturation level, and to low-grade pro-inflammatory as suggested by the significant rise of serum ferritin and haptoglobin levels after DI (P = .003 and P = .003, respectively). These observations highlight the need for better assessment of iron metabolism in bedridden patients, and an optimization of the diet currently proposed to astronauts.

Mitophagy contributes to endothelial adaptation to simulated microgravity.

Exposure to real or simulated microgravity is sensed as a stress by mammalian cells, which activate a complex adaptive response. In human primary endothelial cells, we have recently shown the sequential intervention of various stress proteins which are crucial to prevent apoptosis and maintain cell function. We here demonstrate that mitophagy contributes to endothelial adaptation to gravitational unloading. After 4 and 10 d of exposure to simulated microgravity in the rotating wall vessel, the amount of BCL2 interacting protein 3, a marker of mitophagy, is increased and, in parallel, mitochondrial content, oxygen consumption, and maximal respiratory capacity are reduced, suggesting the acquisition of a thrifty phenotype to meet the novel metabolic challenges generated by gravitational unloading. Moreover, we suggest that microgravity induced-disorganization of the actin cytoskeleton triggers mitophagy, thus creating a connection between cytoskeletal dynamics and mitochondrial content upon gravitational unloading.

Genomic Changes Driven by Radiation-Induced DNA Damage and Microgravity in Human Cells.

The space environment consists of a complex mixture of different types of ionizing radiation and altered gravity that represents a threat to humans during space missions. In particular, individual radiation sensitivity is strictly related to the risk of space radiation carcinogenesis. Therefore, in view of future missions to the Moon and Mars, there is an urgent need to estimate as accurately as possible the individual risk from space exposure to improve the safety of space exploration. In this review, we survey the combined effects from the two main physical components of the space environment, ionizing radiation and microgravity, to alter the genetics and epigenetics of human cells, considering both real and simulated space conditions. Data collected from studies on human cells are discussed for their potential use to estimate individual radiation carcinogenesis risk from space exposure.

Simulated Microgravity Inhibits the Proliferation of Chang Liver Cells by Attenuation of the Major Cell Cycle Regulators and Cytoskeletal Proteins.

Simulated microgravity (SMG) induced the changes in cell proliferation and cytoskeleton organization, which plays an important factor in various cellular processes. The inhibition in cell cycle progression has been considered to be one of the main causes of proliferation inhibition in cells under SMG, but their mechanisms are still not fully understood. This study aimed to evaluate the effects of SMG on the proliferative ability and cytoskeleton changes of Chang Liver Cells (CCL-13). CCL-13 cells were induced SMG by 3D clinostat for 72 h, while the control group were treated in normal gravity at the same time. The results showed that SMG reduced CCL-13 cell proliferation by an increase in the number of CCL-13 cells in G0/G1 phase. This cell cycle phase arrest of CCL-13 cells was due to a downregulation of cell cycle-related proteins, such as cyclin A1 and A2, cyclin D1, and cyclin-dependent kinase 6 (Cdk6). SMG-exposed CCL-13 cells also exhibited a downregulation of α-tubulin 3 and ß-actin which induced the cytoskeleton reorganization. These results suggested that the inhibited proliferation of SMG-exposed CCL-13 cells could be associate with the attenuation of major cell cycle regulators and main cytoskeletal proteins.

Simulated Microgravity Remodels Extracellular Matrix of Osteocommitted Mesenchymal Stromal Cells.

The extracellular matrix (ECM) is the principal structure of bone tissue. Long-term spaceflights lead to osteopenia, which may be a result of the changes in composition as well as remodeling of the ECM by osteogenic cells. To elucidate the cellular effects of microgravity, human mesenchymal stromal cells (MSCs) and their osteocommitted progeny were exposed to simulated microgravity (SMG) for 10 days using random positioning machine (RPM). After RPM exposure, an imbalance of MSC collagen/non-collagen ratio at the expense of a decreased level of collagenous proteins was detected. At the same time, the secretion of proteases (cathepsin A, cathepsin D, MMP3) was increased. No significant effects of SMG on the expression of stromal markers and cell adhesion molecules on the MSC surface were noted. Upregulation of COL11A1, CTNND1, TIMP3, and TNC and downregulation of HAS1, ITGA3, ITGB1, LAMA3, MMP1, and MMP11 were detected in RPM exposed MSCs. ECM-associated transcriptomic changes were more pronounced in osteocommitted progeny. Thus, 10 days of SMG provokes a decrease in the collagenous components of ECM, probably due to the decrease in collagen synthesis and activation of proteases. The presented data demonstrate that ECM-associated molecules of both native and osteocommitted MSCs may be involved in bone matrix reorganization during spaceflight.

Nutraceuticals Synergistically Promote Osteogenesis in Cultured 7F2 Osteoblasts and Mitigate Inhibition of Differentiation and Maturation in Simulated Microgravity.

Microgravity is known to impact bone health, similar to mechanical unloading on Earth. In the absence of countermeasures, bone formation and mineral deposition are strongly inhibited in Space. There is an unmet need to identify nutritional countermeasures. Curcumin and carnosic acid are phytonutrients with anticancer, anti-inflammatory, and antioxidative effects and may exhibit osteogenic properties. Zinc is a trace element essential for bone formation. We hypothesized that these nutraceuticals could counteract the microgravity-induced inhibition of osteogenic differentiation and function. To test this hypothesis, we cultured 7F2 murine osteoblasts in simulated microgravity (SMG) in a Random Positioning Machine in the presence and absence of curcumin, carnosic acid, and zinc and evaluated cell proliferation, function, and differentiation. SMG enhanced cell proliferation in osteogenic medium. The nutraceuticals partially reversed the inhibitory effects of SMG on alkaline phosphatase (ALP) activity and did not alter the SMG-induced reduction in the expression of osteogenic marker genes in osteogenic medium, while they promoted osteoblast proliferation and ALP activity in the absence of traditional osteogenic media. We further observed a synergistic effect of the intermix of the phytonutrients on ALP activity. Intermixes of phytonutrients may serve as convenient and effective nutritional countermeasures against bone loss in space.

Hypercapnia augments resistive exercise-induced elevations in intraocular pressure in older individuals.

NEW FINDINGS: What is the central question of this study? Astronauts on-board the International Space Station (ISS) perform daily exercises designed to prevent muscle atrophy and bone demineralization: what is the effect of resistive exercise performed by subjects while exposed to the same level of hypercapnia as on the ISS on intraocular pressure (IOP)? What is the main finding and its importance? The static exercise-induced elevation in IOP during 6° prone head-down tilt (simulating the headward shift of body fluids in microgravity) is augmented by hypercapnia and exceeds the ocular hypertension threshold. ABSTRACT: The present study assessed the effect of 6° head-down (establishing the cephalad fluid displacement noted in astronauts in microgravity) prone (simulating the effect on the eye) tilt during rest and exercise (simulating exercise performed by astronauts to mitigate the sarcopenia induced by unloading of weight-bearing limbs), in normocapnic and hypercapnic conditions (the latter simulating conditions on the International Space Station) on intraocular pressure (IOP). Volunteers (mean age = 57.8 ± 6 years, n = 10) participated in two experimental sessions, each comprising: (i) 10 min rest, (ii) 3 min static handgrip exercise (30% max), and (iii) 2 min recovery, inspiring either room air (NCAP) or a hypercapnic mixture (1% CO2 , HCAP). We measured IOP in the right eye, cardiac output (CO), stroke volume (SV), heart rate (HR) and mean arterial pressure (MAP) at regular intervals. Baseline IOP in the upright seated position while breathing room air was 14.1 ± 2.9 mmHg. Prone 6° head-down tilt significantly (P < 0.01) elevated IOP in all three phases of the NCAP (rest: 27.0 ± 3.7 mmHg; exercise: 32.2 ± 4.8 mmHg; recovery: 27.4 ± 4.0 mmHg) and HCAP (rest: 27.3 ± 4.3 mmHg; exercise: 34.2 ± 6.0 mmHg; recovery: 29.1 ± 5.8 mmHg) trials, with hypercapnia augmenting the exercise-induced elevation in IOP (P < 0.01). CO, SV, HR and MAP were significantly increased during handgrip dynamometry, but there was no effect of hypercapnia. The observed IOP measured during prone 6° HDT in all phases of the NCAP and HCAP trials exceeded the threshold pressure defining ocular hypertension. The exercise-induced increase in IOP is exacerbated by hypercapnia.

Effect of simulated microgravity conditions of hindlimb unloading on mice hematopoietic and mesenchymal stromal cells.

Conditions in space, such as microgravity, may affect the hematopoietic and bone marrow-derived mesenchymal stromal cells (BM-MSCs) of astronauts. However, to date, few detailed phenotype change data about the different type of hematopoietic cells have reported. In this study, C57BL/6 mice were randomly divided into two groups: a control group (control) and a hindlimb suspension group (treated). After four weeks of hindlimb suspension, we found that this simulated microgravity (sµg) condition could increase the percentage of monocytes and macrophages and decrease the percentage of B lymphocytes and mature red cells in bone marrow. The percentage of B lymphocytes in the spleen and the red blood cell count in peripheral blood also decreased, consistent with the response of bone marrow. The cytoskeleton in the BM-MSCs was disrupted. The expression levels of hematopoietic-related genes, such as fms-like tyrosine kinase-3 ligand, granulocyte-macrophage colony stimulating factor, interleukin-3, and adipogenic differentiation associated genes, leptin and proliferator-activated receptor γ type 2, were upregulated under sµg conditions. These results indicated that simulating microgravity can affect the phenotype of certain types of hematopoietic cells and the morphology and gene expression pattern of BM-MSCs.

Simulation of human gait with body weight support: benchmarking models and unloading strategies.

BACKGROUND: Gait training with partial body weight support (BWS) has become an established rehabilitation technique. Besides passive unloading mechanisms such as springs or counterweights, also active systems that allow rendering constant or modulated vertical forces have been proposed. However, only pilot studies have been conducted to compare different unloading or modulation strategies, and conducting experimental studies is costly and time-consuming. Simulation models that predict the influence of unloading force on human walking may help select the most promising candidates for further evaluation. However, the reliability of simulation results depends on the chosen gait model. The purpose of this paper is two-fold: First, using human experimental data, we evaluate the accuracy of some of the most prevalent walking models in replicating human walking under the influence of Constant-Force BWS: The Simplest Walking model (SW), the Spring-Loaded Inverted Pendulum model (SLIP) and the Muscle-Reflex (MR) gait model. Second, three realizations of BWS, based on Constant-Force (CF), Counterweight (CW) and Tuned-Spring (TS) approaches, are compared to each other in terms of their influence on gait parameters. METHODS: We conducted simulations in Matlab/Simulink to model the behaviour of each gait model under all three BWS conditions. Nine simulations were undertaken in total and gait parameter response was analysed in each case. Root mean square error (mrmse) w.r.t human data was used to compare the accuracy of gait models. The metrics of interest were spatiotemporal parameters and the vertical ground reaction forces. To scrutinize the BWS strategies, loss of dynamic similarity was calculated in terms of root mean square difference in gait dynamics (Δgd) with respect to the reference gait under zero unloading. The gait dynamics were characterized by a dimensionless number Modela-w. RESULTS: SLIP model showed the lowest mrmse for 6 out of 8 gait parameters and for 1 other, the mrmse value were comparable to the MR model; SW model had the highest mrmse. Out of three BWS strategies, Tuned-Spring strategies led to the lowest Δgd values. CONCLUSIONS: The results of this work demonstrate the usefulness of gait models for BWS simulation and suggest the SLIP model to be more suitable for BWS simulations than the Simplest Walker and the Muscle-reflex models. Further, the Tuned-Spring approach appears to cause less distortions to the gait pattern than the more established Counterweight and Constant-Force approaches and merits experimental verification.

Changes in Nuclear Shape and Gene Expression in Response to Simulated Microgravity Are LINC Complex-Dependent.

Microgravity is known to affect the organization of the cytoskeleton, cell and nuclear morphology and to elicit differential expression of genes associated with the cytoskeleton, focal adhesions and the extracellular matrix. Although the nucleus is mechanically connected to the cytoskeleton through the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, the role of this group of proteins in these responses to microgravity has yet to be defined. In our study, we used a simulated microgravity device, a 3-D clinostat (Gravite), to investigate whether the LINC complex mediates cellular responses to the simulated microgravity environment. We show that nuclear shape and differential gene expression are both responsive to simulated microgravity in a LINC-dependent manner and that this response changes with the duration of exposure to simulated microgravity. These LINC-dependent genes likely represent elements normally regulated by the mechanical forces imposed by gravity on Earth.

EMT Transcription Factors Are Involved in the Altered Cell Adhesion under Simulated Microgravity Effect or Overloading by Regulation of E-cadherin.

In order to study the effect of stress changes on cell adhesion, HUVEC, and MCF-7 cells were treated with simulated microgravity effect (SMG) and overloading (OL). METHODS: Rotating Wall Vessel (2D-RWVS) bioreactor was used to create different culture conditions. In addition, the alteration of cell adhesion states, adhesion proteins, and relating factors of adhesion molecules under these two conditions were detected using cell adhesion assay, immunofluorescence, western blot, and qRT-PCR technology. RESULTS: The results showed that the adhesion of cells decreased under SMG, while increased under OL. The expressions of integrin ß1, paxillin, and E-cadherin under SMG condition were down-regulated as compared to that of the control group showing a time-dependent pattern of the decreasing. However, under OL condition, the expressions of adhesion proteins were up-regulated as compared to that of the control group, with a time-dependent pattern of increasing. EMT transcription factors Snail, twist, and ZEB1 were up-regulated under SMG while down-regulated under OL. CONCLUSION: Collectively our results indicated that cells could respond to stress changes to regulate the expressions of adhesion proteins and adapt their adhesion state to the altered mechanical environment. The altered cell adhesion in response to the mechanical stress may involve the changed expression of EMT-inducing factors, Snail, Twist, and ZEB1under the SMG/OL conditions.

Drosophila melanogaster Sperm under Simulated Microgravity and a Hypomagnetic Field: Motility and Cell Respiration.

The role of the Earth's gravitational and magnetic fields in the evolution and maintenance of normal processes of various animal species remains unclear. The aim of this work was to determine the effect of simulated microgravity and hypomagnetic conditions for 1, 3, and 6 h on the sperm motility of the fruit fly Drosophila melanogaster. In addition to the usual diet, the groups were administered oral essential phospholipids at a dosage of 500 mg/kg in medium. The speed of the sperm tails was determined by video recording and analysis of the obtained video files, protein content by western blotting, and cell respiration by polarography. The results indicated an increase in the speed of movement of the sperm tails after 6 h in simulated microgravity. The levels of proteins that form the axoneme of the sperm tail did not change, but cellular respiration was altered. A similar effect occurred with the administration of essential phospholipids. These results may be due to a change in the level of phosphorylation of motor proteins. Exposure to hypomagnetic conditions led to a decrease in motility after 6 h against a background of a decrease in the rate of cellular respiration due to complex I of the respiratory chain. This effect was not observed in the flies that received essential phospholipids. However, after 1 h under hypomagnetic conditions, the rate of cellular respiration also increased due to complex I, including that in the sperm of flies receiving essential phospholipids.

Peculiarities of Pharmacokinetics and Bioavailability of Some Cardiovascular Drugs under Conditions of Antiorthostatic Hypokinesia.

We studied pharmacokinetics and bioavailability of verapamil, propranolol, and ethacizine in healthy volunteers after single oral administration under normal conditions and on the second day of simulated antiorthostatic hypokinesia modeling some effects of microgravity. Under conditions of antiorthostatic hypokinesia, a tendency to a decrease in half-elimination period, mean retention time, and volume of distribution and an increase in the rate of absorption, ratio of maximum concentrations, and relative rate of absorption of verapamil and propranolol were revealed. For ethacizine, a statistically significant increase in the time of attaining maximum concentration and volume of distribution and a decrease in the maximum concentration, rate of absorption, ratio of maximum concentrations, and relative rate of absorption under conditions of antiorthostatic hypokinesia were found.

Remote Controlled Autonomous Microgravity Lab Platforms for Drug Research in Space.

Research conducted in microgravity conditions has the potential to yield new therapeutics, as advances can be achieved in the absence of phenomena such as sedimentation, hydrostatic pressure and thermally-induced convection. The outcomes of such studies can significantly contribute to many scientific and technological fields, including drug discovery. This article reviews the existing traditional microgravity platforms as well as emerging ideas for enabling microgravity research focusing on SpacePharma's innovative autonomous remote-controlled microgravity labs that can be launched to space aboard nanosatellites to perform drug research in orbit. The scientific literature is reviewed and examples of life science fields that have benefited from studies in microgravity conditions are given. These include the use of microgravity environment for chemical applications (protein crystallization, drug polymorphism, self-assembly of biomolecules), pharmaceutical studies (microencapsulation, drug delivery systems, behavior and stability of colloidal formulations, antibiotic drug resistance), and biological research, including accelerated models for aging, investigation of bacterial virulence , tissue engineering using organ-on-chips in space, enhanced stem cells proliferation and differentiation.

Reptiles in Space Missions: Results and Perspectives.

Reptiles are a rare model object for space research. However, some reptile species demonstrate effective adaptation to spaceflight conditions. The main scope of this review is a comparative analysis of reptile experimental exposure in weightlessness, demonstrating the advantages and shortcomings of this model. The description of the known reptile experiments using turtles and geckos in the space and parabolic flight experiments is provided. Behavior, skeletal bones (morphology, histology, and X-ray microtomography), internal organs, and the nervous system (morphology, histology, and immunohistochemistry) are studied in the spaceflight experiments to date, while molecular and physiological results are restricted. Therefore, the results are discussed in the scope of molecular data collected from mammalian (mainly rodents) specimens and cell cultures in the parabolic and orbital flights and simulated microgravity. The published data are compared with the results of the gecko model studies after the 12-44.5-day spaceflights with special reference to the unique peculiarities of the gecko model for the orbital experiments. The complex study of thick-toed geckos after three spaceflights, in which all geckos survived and demonstrated effective adaptation to spaceflight conditions, was performed. However, future investigations are needed to study molecular mechanisms of gecko adaptation in space.

Apoptosis Induction and Alteration of Cell Adherence in Human Lung Cancer Cells under Simulated Microgravity.

BACKGROUND: Lung cancer cells are known to change proliferation and migration under simulated microgravity. In this study, we sought to evaluate cell adherence, apoptosis, cytoskeleton arrangement, and gene expression under simulated microgravity. METHODS: Human lung cancer cells were exposed to simulated microgravity in a random-positioning machine (RPM). Cell morphology and adherence were observed under phase-contrast microscopy, cytoskeleton staining was performed, apoptosis rate was determined, and changes in gene and protein expression were detected by real-time PCR with western blot confirmation. RESULTS: Three-dimensional (3D)-spheroid formation was observed under simulated microgravity. Cell viability was not impaired. Actin filaments showed a shift in alignment from longitudinal to spherical. Apoptosis rate was significantly increased in the spheroids compared to the control. TP53, CDKN2A, PTEN, and RB1 gene expression was significantly upregulated in the adherent cells under simulated microgravity with an increase in corresponding protein production for p14 and RB1. SOX2 expression was significantly upregulated in the adherent cells, but protein was not. Gene expressions of AKT3, PIK3CA, and NFE2L2 remained unaltered. CONCLUSION: Simulated microgravity induces alteration in cell adherence, increases apoptosis rate, and leads to upregulation of tumor suppressor genes in human lung cancer cells.