Simulated Microgravity Environment Research Articles

Ground-Based Study on Distribution of Fire Parameters and Installation of Fire Detectors in Space-Confined Microgravity

The manned spacecraft is a typically confined space in microgravity and it suffers severe fire risks. This paper studies on the distribution of the fire parameters in space-confined microgravity to find a more rational way to install the fire detectors. The experiments are carried out in the ground simulation experiment platform for fire based on the International Space Station. Based on the functional simulation principle, this paper maintainsGr(Grashof number) and increasesRe(Reynolds number) to simulate microgravity environment in such a full-scale platform. The results show that Fire Detector 5 on the center of the side wall and Fire Detector 7 on the corner of the ceiling are the best installing locations for smoke detection. And, temperature detection is not appropriate in manned spacecraft. Namely, the way to install the fire detectors in manned spacecraft should be different from that in normal gravity.

How to stimulate a space microgravity environment or effect on Earth: From the viewpoint of responses of space cell growth to microgravity

Little is known about the effects of a microgravity environment in space on biological, chemical, and physical processes. It also remains unclear if it is possible to simulate a space microgravity environment or effect on Earth. This paper discusses, according to the mechanical/physical principles of the basic processes of cell growth in space, the issues of what gravitational change is, how a space microgravity environment or effect can be simulated, and how biological responses to a simulated microgravity environment can be mimicked. It aims to elucidate relevant concepts in space life science and biotechnology, as well as in space physiology and medicine, and to present the scientific merits of related ground-based investigations.

Mouse undifferentiated spermatogonial stem cells cultured as aggregates under simulated microgravity.

Dynamic simulated microgravity (SMG) culture systems provide environments that stimulate stem cell proliferation and differentiation. However, the effect of SMG on spermatogonial stem cells (SSCs) remains unclear. Here, we used a rotating cell culture system (RCCS) to determine its effect on mouse SSC proliferation and differentiation. SSCs were enriched from mouse pub testis and cocultured with Sertoli cell feeders pre-treated with mitomycin C on fibrin scaffolds in a rotary bioreactor for 14 days. Our results show that mouse SSCs cultured in a rotary bioreactor exhibited enhanced proliferation surpassing those cultured in static conditions, although SSC cultures in SMG underwent a growth lag at initial 3 days. After 14 days, mouse SSCs and feeders grew into cell aggregates with average diameters of 242.63 ± 16.53 μm compared with those in conventional static culture (49.51 ± 15.64 μm). Related detection revealed that proliferating SSCs in SMG remained undifferentiated, maintained clone-forming capacity and were capable of differentiation into round spermatids with flagella. The growth characteristics of mouse SSCs in RCCS suggest that the resulting aggregates are similar to native in vivo cells. Rotary bioreactors that create SMG environments may be an alternative to conventional systems for the clinical application of SSCs.

Simulated Microgravity Based Stem Cell Cultures Enhance Their Utility for Cell-Based Therapy

A technical improvement enabling efficient and reproducible stem cell cultures is one of the most important aspects in stem cell research and cell-based therapy. For this purpose, researchers have used various cytokine cocktails and gene transfection techniques to proliferate stem cells. However, stem cell fate can reportedly be determined by physical stimuli such as gravity, electrical fields, and magnetic fields. In this regard, we have developed a novel technique utilizing a clinostat, a device capable of generating a controlled microgravity environment for robust maintenance of stem cell state. Here, we review our recent progress in expansion and differentiation of stem cells grown under simulated microgravity environment and their utility for transplantation in animal models of cartilage deficiency and neurotrauma.

Effects of Underwater Arm-Cranking Exercise on Cardiac Autonomic Nervous Activity

ABSTRACT The purpose of this study was to clarify the beneficial effect of an underwater environment on heart rate (HR) and cardiac autonomic nervous activity (HF) during arm-cranking exercise. Ten healthy young men participated in this study. The arm-cranking exercise (40% peakV̇O2) was performed for 10 minutes under two conditions: in water and in air. After the exercise, a recovery phase for 30 seconds followed. Changes in HR, V̇O2, and HF did not differ between the conditions. The time constant of the heart rate decay for the first 30 seconds after exercise in the water was less than in air. The results suggest that cardiac parasympathetic nervous activity influences earlier recovery of HR after exercise in water. The results of our study suggest underwater exercise may be applied to wider areas of health management for individuals returning from space travel or sedentary patients in simulated microgravity environments.

Effect of 45-day simulated microgravity on the evaluation of orally reported emergencies

Accurate evaluation of emergencies is a critical concern in long-duration space flights. Accordingly, we studied the effect of 45 days of − 6° head-down bed rest – a model that simulates the conditions in microgravity environments – on the evaluation of orally reported emergencies. Sixteen male participants listened to corresponding emergency scenarios and assessed the severity of these situations eight times before, during and after bed rest. The results revealed a ‘ recency effect’: compared with emergency descriptions in the order of serious to mild, those framed in the reverse order were judged to be more serious. However, the severity ratings did not vary with time spent in the simulated microgravity environment. These findings are similar to those observed in a regular environment on Earth, indicating that the design principles of information presentation for situations on Earth may also be extended to designs intended for outer space. Practitioner Summary: A recency effect was found in the evaluation of orally reported emergencies under simulated microgravity conditions. The design principles of information presentation for situations on Earth may also be extended to designs intended for outer space.

Simulated microgravity increases susceptibility of intestinal epithelial cells to acetaldehyde‐induced barrier dysfunction

Previously, we showed that intestinal epithelial cells (IEC) exposed to simulated microgravity display lower transepithelial resistance (TER) and delayed localization of tight junction proteins indicating a barrier defect. Here, we investigated whether simulated microgravity increases susceptibility to epithelial barrier defects by the alcohol metabolite, acetaldehyde. HT‐29 IEC were cultured (i) on microcarrier beads for 18 days in a rotating wall vessel (RWV) to simulate microgravity, (ii) on beads without microgravity (static control), and (iii) in flasks (flask control). After removal of cells from beads or flasks and seeding on semi‐permeable supports for 11 and 14 days, RWV and control IECs were pre‐incubated with phosphate buffered saline (PBS) for 1 hour followed by 0.5% vapor phase acetaldehyde or PBS alone for 5 hours. TER, expressed as % change, was measured following PBS preincubation and again after 5hr treatment. Acetaldehyde caused a greater TER decrease in RWV cells (−13 ± 4.9%; n=6; p<0.05) vs. static (−3 ± 6.9%; n=6) and flask controls (−6 ± 5 %; n=6). PBS alone had no significant effect. Acetaldehyde also increased permeability to 4KD FITC‐dextran in RWV cells vs. controls. ZO‐1 and occludin proteins showed correlative decreases in expression. These data suggest that a simulated microgravity environment increases acetaldehyde‐induced barrier defects. Supported by NIH UH2 AA019708–01.

Reversal of the Detrimental Effects of Simulated Microgravity on Human Osteoblasts by Modified Low Intensity Pulsed Ultrasound

Microgravity (MG) is known to induce bone loss in astronauts during long-duration space mission because of a lack of sufficient mechanical stimulation under MG. It has been demonstrated that mechanical signals are essential for maintaining cell viability and motility, and they possibly serve as a countermeasure to the catabolic effects of MG. The objective of this study was to examine the effects of high-frequency acoustic wave signals on osteoblasts in a simulated microgravity (SMG) environment (created using 1-D clinostat bioreactor) using a modified low-intensity pulsed ultrasound (mLIPUS). Specifically, we evaluated the hypothesis that osteoblasts (human fetal osteoblastic cell line) exposure to mLIPUS for 20 min/d at 30 mW/cm2 will significantly reduce the detrimental effects of SMG. Effects of SMG with mLIPUS were analyzed using the MTS proliferation assay for proliferation, phalloidin for F-actin staining, Sirius red stain for collagen, and Alizarin red for mineralization. Our data showed that osteoblast exposure to SMG results in significant decreases in proliferation (∼ −38% and ∼ −44% on days 4 and 6, respectively; p < 0.01), collagen content (∼ −22%; p < 0.05) and mineralization (∼ −37%; p < 0.05) and actin stress fibers. In contrast, mLIPUS stimulation in SMG condition significantly increases the rate of proliferation (∼24% by day 6; p < 0.05), collagen content (∼52%; p < 0.05) and matrix mineralization (∼25%; p < 0.001) along with restoring formation of actin stress fibers in the SMG-exposed osteoblasts. These data suggest that the acoustic wave can potentially be used as a countermeasure for disuse osteopenia.

Development of a Landing Mechanism for Asteroids with Soft Surface

A landing mechanism to an asteroid with soft surface is developed. It consists of three landing feet, landing legs, cardan element, damping element, equipment base, anchoring system, and so on. Static structural analysis and modal analysis are carried out to check the strength and natural frequency of the landing mechanism with FEA. Testing platform for the anchoring system is introduced, and then the penetrating and anchoring tests of the anchoring system are carried out in different media. It shows that cohesion of the media has large influence on the penetrating and anchoring performance of the anchoring system. Landing tests of the landing mechanism with different velocities under simulated microgravity environment are carried out on the air-floating platform, and the impact accelerations are measured by the sensors on the landing mechanism. At the same time, these impact accelerations are processed by spectrum analysis to find the natural frequency of the landing mechanism.

Phenotypic characterization of Aspergillus niger and Candida albicans grown under simulated microgravity using a three‐dimensional clinostat

The living and working environments of spacecraft become progressively contaminated by a number of microorganisms. A large number of microorganisms, including pathogenic microorganisms, some of which are fungi, have been found in the cabins of space stations. However, it is not known how the characteristics of microorganisms change in the space environment. To predict how a microgravity environment might affect fungi, and thus how their characteristics could change on board spacecraft, strains of the pathogenic fungi Aspergillus niger and Candida albicans were subjected to on-ground tests in a simulated microgravity environment produced by a three-dimensional (3D) clinostat. These fungi were incubated and cultured in a 3D clinostat in a simulated microgravity environment. No positive or negative differences in morphology, asexual reproductive capability, or susceptibility to antifungal agents were observed in cultures grown under simulated microgravity compared to those grown in normal earth gravity (1 G). These results strongly suggest that a microgravity environment, such as that on board spacecraft, allows growth of potentially pathogenic fungi that can contaminate the living environment for astronauts in spacecraft in the same way as they contaminate residential areas on earth. They also suggest that these organisms pose a similar risk of opportunistic infections or allergies in astronauts as they do in people with compromised immunity on the ground and that treatment of fungal infections in space could be the same as on earth.

Simulated microgravity alters the expression of key genes involved in fracture healing

Fracture healing in animal models has been shown to be altered in both ground based analogs of spaceflight and in those exposed to actual spaceflight. The molecular mechanisms behind altered fracture healing as a result of chronic exposure to microgravity remain to be elucidated. This study investigates temporal gene expression of multiple factors involved in secondary fracture healing, specifically those integral to the development of a soft tissue callus and the transition to that of hard tissue. Skeletally mature female rats were subjected to a 4 week period of simulated microgravity and then underwent a closed femoral fracture procedure. Thereafter, they were reintroduced to the microgravity and allowed to heal for a 1 or 2 week period. A synchronous group of weight bearing rats was used as a normal fracture healing control. Utilizing Real-Time quantitative PCR on mRNA from fracture callus tissue, we found significant reductions in the levels of transcripts associated with angiogenesis, chondrogenesis, and osteogenesis. These data suggest an altered fracture healing process in a simulated microgravity environment, and these alterations begin early in the healing process. These findings may provide mechanistic insight towards developing countermeasure protocols to mitigate these adaptations.

Expression of estrogen receptor α in human breast cancer cells regulates mitochondrial oxidative stress under simulated microgravity

This study investigated intracellular oxidative stress and its underlying mechanisms in a rotary cell culture system used to achieve a simulated microgravity (SMG) environment. Experiments were conducted with human breast cancer cell lines MCF-7 (an estrogen receptor (ER) α positive cell line) and MDA-MB-231 (an ERα negative cell line) encapsulated in alginate/collagen carriers. After 48h, SMG led to oxidative stress and DNA damage in the MDA-MB-231 cells but a significant increase in mitochondrial activity and minimal DNA damage in the MCF-7 cells. The activity of superoxide dismutase (SOD) significantly increased in the MCF-7 cells and decreased in MDA-MB-231 cells in the SMG environment compared with a standard gravity control. Moreover, SMG promoted expression of ERα and protein kinase C (PKC) epsilon in MCF-7 cells treated with PKC inhibitor Gö6983. Overall, exposure to SMG increased mitochondrial activity in ERα positive cells but induced cellular oxidative damage in ERα negative cells. Thus, ERα may play an important role in protecting cells from oxidative stress damage under simulated microgravity.

7C14 人工無重力環境を利用した未分化幹細胞培養技術の開発(OS21 幹細胞利用と培養・評価技術)

7C14 人工無重力環境を利用した未分化幹細胞培養技術の開発(OS21 幹細胞利用と培養・評価技術)

Reconstitution of hepatic tissue architectures from fetal liver cells obtained from a three-dimensional culture with a rotating wall vessel bioreactor

Reconstitution of tissue architecture in vitro is important because it enables researchers to investigate the interactions and mutual relationships between cells and cellular signals involved in the three-dimensional (3D) construction of tissues. To date, in vitro methods for producing tissues with highly ordered structure and high levels of function have met with limited success although a variety of 3D culture systems have been investigated. In this study, we reconstituted functional hepatic tissue including mature hepatocyte and blood vessel-like structures accompanied with bile duct-like structures from E15.5 fetal liver cells, which contained more hepatic stem/progenitor cells comparing with neonatal liver cells. The culture was performed in a simulated microgravity environment produced by a rotating wall vessel (RWV) bioreactor. The hepatocytes in the reconstituted 3D tissue were found to be capable of producing albumin and storing glycogen. Additionally, bile canaliculi between hepatocytes, characteristics of adult hepatocyte in vivo were also formed. Apart from this, bile duct structure secreting mucin was shown to form complicated tubular branches. Furthermore, gene expression analysis by semi-quantitative RT-PCR revealed the elevated levels of mature hepatocyte markers as well as genes with the hepatic function. With RWV culture system, we could produce functionally reconstituted liver tissue and this might be useful in pharmaceutical industry including drug screening and testing and other applications such as an alternative approach to experimental animals.

Detection of the quantity of kinesin and microgravity-sensitive kinesin genes in rat bone marrow stromal cells grown in a simulated microgravity environment

Kinesin and kinesin-like proteins (KLPs) constitute a superfamily of microtubule motor proteins found in all eukaryotic organisms. Members of the kinesin superfamily are known to play important roles in many fundamental cellular and developmental processes. To date, few published studies have reported on the effects of microgravity on kinesin expression. In this paper, we describe the expression pattern and microgravity-sensitive genes of kinesin in rat bone marrow stromal cells cultured in a ground-based rotating bioreactor. The quantity of kinesin under the clinorotation condition was examined by immunoblot analysis with anti-kinesin. Furthermore, the distribution of kinesin at various times during clinorotation was determined by dual immunostaining, using anti-kinesin monoclonal antibody or anti-β-tubulin monoclonal antibody. In terms of kinesin quantity, we found that the ratios of the amounts of clinorotated/stationary KLPs decreased from clinorotation day 5 to day 10, although it increased on days 2 and 3. Immunofluorescence analysis revealed that kinesin in the nucleus was the first to be affected by simulated microgravity, following the kinesin at the periphery that was affected at various times during clinorotation. Real-time RT-PCR analysis of kinesin mRNA expression was performed and led to the identification of 3 microgravity-sensitive kinesin genes: KIF9, KIFC1, and KIF21A. Our results suggest that kinesin has a distinct expression pattern, and the identification of microgravity-sensitive kinesin genes offers insight into fundamental cell biology.

ICAM-1 expression and organization in human endothelial cells is sensitive to gravity

Transendothelial migration (TEM) of immune cells is a crucial process during a multitude of physiological and pathological conditions such as development, defense against infections and wound healing. Migration within the body tissues and through endothelial barriers is strongly dependent and regulated both by cytoskeletal processes and by expression of surface adhesion molecules such as ICAM-1 and VCAM-1. Space flight experiments have confirmed that TEM will be inhibited and may cause astronauts’ immune function decreased and make them easy for infection. We used NASA RCCS to provide a simulated microgravity environment; endothelial cells were cultured on microcarrier beads and activated by TNF-α. Results demonstrate after clinorotation ICAM-1 expression increased, consistent with the notion in parabolic flights. However, VCAM-1 showed no significant change between activated or inactivated cells. Depolymerization of F-actin and clustering of ICAM-1 on cell membrane were also observed in short-term simulated microgravity, and after 24 h clinorotation, actin fiber rearrangement was initiated and clustering of ICAM-1 became stable. ICAM-1 mRNA and VCAM-1 mRNA were up-regulated after 30 min clinorotation, and returned to the same level with controls after 24 h clinorotation.

Effect Of Elastic Band Resistance Training During Simulated Microgravity On Neuromuscular Function

Prolonged duration in a weightless environment results in decreased neuromuscular function. In Earth's 1-g environment, resistance exercise helps prevent muscle atrophy and its subsequent attenuations in strength and power. Previous studies have attempted to apply findings of gravity-based research to a microgravity environment. Although it has been shown that the decrease in neuromuscular function from a weightless environment can be attenuated through resistance training in 1-g, studies have not been completely successful utilizing resistance training in a microgravity environment to completely counter these negative neuromuscular changes. To examine the effect of elastic band resistance training in a microgravity-simulated environment on muscle size, strength, power, and muscle activity pre- and post- training. Twenty college-age males were randomly assigned to a training (T) group (n = 13; age = 20.15 ± 1.34years; height = 178.85 ± 8.23 cm; mass = 77.47 ± 8.63 kg) or a control (C) group (n = 7; age = 21.71 ± 1.70 years; height = 174.8 ± 4.56 cm; mass = 73.90 ± 8.70 kg) that refrained from any training during the nine-week period. Kinetic and kinematic variables, as well as electromyography (EMG) of the vastus lateralis (VL), were collected and analyzed before and after the training period in which the T group completed a progressive resistance protocol consisting of six sets often dead lifts utilizing elastic bands while in the custom-made microgravity apparatus. Muscle size was obtained through a DEXA scan, strength was measured by one-repetition maximum (1RM) squat, power was assessed through a countermovement jump (CMJ) at body mass, and muscle activity was determined through EMG of the VL. Squat 1RM strength increased significantly in the T group (103.65 ± 26.94 kg to 115.38 ± 25.43 kg, p < 0.001) as compared to no change in the C group (121.43 ± 30.78 kg to 125.71 ± 21.62 kg). No statistically significant changes were observed in power during the CMJ (4738.61 ± 700.70 W to 4562.59 ± 971.31 W) after training. Changes in muscle size and activity were insignificant. This was the first study to examine the effectiveness of elastic resistance bands in a microgravity training environment. This model was effective in inducing strength gains. Utilizing resistance bands may be a viable exercise countermeasure to combat the negative neuromuscular effects experienced from prolonged exposure to microgravity. With the inefficacy of free weights in microgravity, it is necessary to find an alternative means of resistance training. Elastic resistance band training provides a practical and cost-effective method to increase strength in microgravity. Because this is the first study to utilize elastic resistance bands in a simulated microgravity environment, more research is warranted to determine the optimal training variables such as sets, reps, and rest periods needed to produce the greatest hypertrophy and strength gains. Additionally, future investigations should include this microgravity-simulated exercise protocol during a concurrent period of bed rest. Acknowledgment: This investigation was funded by a North Carolina Space Grant - New Investigations Program Grant.

Simulated Microgravity Affects Growth of Escherichia coli and Recombinant β-d-Glucuronidase Production

Effects of simulated microgravity (SMG) on bacteria have been studied in various aspects. However, few reports are available about production of recombinant protein expressed by bacteria in SMG. In this study growth of E. coli BL21 (DE3) cells transformed with pET-28a (+)-pgus in double-axis clinostat that could model low shear SMG environment and the recombinant beta-D-glucuronidase (PGUS) expression have been investigated. Results showed that the cell dry weights in SMG were 16.47%, 38.06%, and 28.79% more than normal gravity (NG) control, and the efficiency of the recombinant PGUS expression in SMG were 18.33%, 19.36%, and 33.42% higher than that in NG at 19 degrees C, 28 degrees C, and 37 degrees C, respectively (P < 0.05).

The influence of leptin on the activity of lung lymphocytes under simulated microgravity

Exposure to microgravity has been implicated in the compromised immune function in space travellers, resulting in opportunistic infections, poor wound healing, and cancer. Since recent studies have suggested that leptin was capable of modulating immune responses, the purpose of this study was to examine effects of microgravity on the activation and proliferation of rat lung lymphocytes and then to examine the effects of leptin-mediated signal transduction mechanisms of lymphocyte activation in these same conditions. In control conditions (T-flasks cultured cells) leptin was not able by itself to increase lymphocytes proliferation, or induce significant increase of either IL-2 production or expression of lymphocytes activation markers, such as CD25 and CD71, while it markedly enhanced the positive effects induced on these parameters by concanavalin A (ConA). Using clinostatic rotating wall vessel (RWV) bioreactors to simulate a microgravity environment, we found that ConA responsiveness was inhibited. Moreover, under these conditions, leptin was not able to reverse these impaired functions. Accordingly with the above cited inhibitory effects exerted by the simulated microgravity environment, evidence was also obtained of defects in lymphocyte intracellular signal transduction induced by the incubation in RWV bioreactors, namely concerning decreased ConA-mediated PKC activity, and reduced expression of NF-kappaB, c-fos, and ERK1/2. Again, leptin appeared to be unable in restoring a physiologic increase of these parameters, different from what could be observed after complementation of the ConA-mediated signalling with phorbol myristate acetate, which instead demonstrated to overcome the inhibition of lymphocytes activating functions, in the presence of simulated microgravity conditions.

Cultivation of lacrimal gland acinar cells in a microgravity environment

Background:A rotary cell-culture system (RCCS) allows the creation of a microgravity environment of low shear force, high-mass transfer and three-dimensional cell culture of various cell types. The aim of the...