In situ study on articular cartilage degeneration in simulated microgravity by HOF-ATR-FTIR spectroscopy.

Fourier transform infrared spectroscopy (FTIRS) can provide rich information on the composition and content of samples, enabling the detection of subtle changes in tissue composition and structure. This study represents the first application of FTIRS to investigate cartilage under microgravity. Simulated microgravity cartilage model was firstly established by tail-suspension (TS) for 7, 14 and 21 days, which would be compared to control samples. A self-developed hollow optical fiber attenuated total reflection (HOF-ATR) probe coupled with a FTIR spectrometer was used for the spectral acquisition of cartilage samples in situ, and one-way analysis of variance (ANOVA) was employed to analyze the changes in the contents of cartilage matrix at different stages. The results indicate that cartilage degenerates in microgravity, the collagen content gradually decreases with the TS time, and the structure of collagen fibers changes. The trends of proteoglycan content and collagen integrity show an initial decrease followed by an increase, ultimately significantly decreasing. The findings provide the basis for the cartilage degeneration in microgravity with TS time, which must be of real significance for space science and health detection.

Exploring the effects of simulated microgravity on esophageal cancer cells: insights into morphological, growth behavior, adhesion, and genetic damage.

The exploration of microgravity has garnered substantial scholarly attention due to its potential to offer unique insights into the behavior of biological systems. This study presents a preliminary investigation into the effects of simulated microgravity on esophageal cancer cells, examining various aspects such as morphology, growth behavior, adhesion, inhibition rate, and DNA damage. To achieve this, a novel microgravity simulator named "Gravity Challenge" was utilized for its effectiveness in minimizing external influences that could compromise microgravity conditions. The international cell line SK-GT-4 was utilized as the focal point of this investigation. Results revealed noticeable alterations in the growth behavior of cancer cells following exposure to simulated microgravity for 24 h, characterized by a loss of adhesion properties compared to control cells. Concurrently, cell viability exhibited a decline, as evidenced by cytotoxicity testing. Furthermore, the comet assay test demonstrated that cells subjected to microgravity simulation experienced a higher incidence of DNA damage compared to their control counterparts. In conclusion, this comprehensive examination of the impact of simulated microgravity on esophageal cancer cells extends beyond morphological changes, delving into genetic implications through observed DNA damage. The diminished vitality of cells under microgravity conditions underscores the multifaceted effects on cellular behavior in response to environmental variations. These findings represent a significant step towards understanding the dynamics of cancer cells, laying the groundwork for future research aimed at identifying potential therapeutic strategies for this disease.

Effects of simulated microgravity on colorectal cancer organoids growth and drug response.

Cellular and molecular dynamics of human cells are constantly affected by gravity. Alteration of the gravitational force disturbs the cellular equilibrium, which might modify physiological and molecular characteristics. Nevertheless, biological responses of cancer cells to reduced gravitational force remains obscure. Here, we aimed to comprehend not only transcriptomic patterns but drug responses of colorectal cancer (CRC) under simulated microgravity. We established four organoids directly from CRC patients, and organoids cultured in 3D clinostat were subjected to genome wide expression profiling and drug library screening. Our observations revealed changes in cell morphology and an increase in cell viability under simulated microgravity compared to their static controls. Transcriptomic analysis highlighted a significant dysregulation in the TBC1D3 family of genes. The upregulation of cell proliferation observed under simulated microgravity conditions was further supported by enriched cell cycle processes, as evidenced by the functional clustering of mRNA expressions using cancer hallmark and gene ontology terms. Our drug screening results indicated an enhanced response rate to 5-FU under conditions of simulated microgravity, suggesting potential implications for cancer treatment strategies in simulated microgravity.

Effects of simulated space conditions on CD4+ T cells: a multi modal analysis.

Introduction: The immune system is an intricate network of cellular components that safeguards against pathogens and aberrant cells, with CD4+ T cells playing a central role in this process. Human space travel presents unique health challenges, such as heavy ion ionizing radiation, microgravity, and psychological stress, which can collectively impede immune function. The aim of this research was to examine the consequences of simulated space stressors on CD4+ T cell activation, cytokine production, and gene expression. Methods: CD4+ T cells were obtained from healthy individuals and subjected to Fe ion particle radiation, Photon irradiation, simulated microgravity, and hydrocortisone, either individually or in different combinations. Cytokine levels for Th1 and Th2 cells were determined using multiplex Luminex assays, and RNA sequencing was used to investigate gene expression patterns and identify essential genes and pathways impacted by these stressors. Results: Simulated microgravity exposure resulted in an apparent Th1 to Th2 shift, evidenced on the level of cytokine secretion as well as altered gene expression. RNA sequencing analysis showed that several gene pathways were altered, particularly in response to Fe ions irradiation and simulated microgravity exposures. Individually, each space stressor caused differential gene expression, while the combination of stressors revealed complex interactions. Discussion: The research findings underscore the substantial influence of the space exposome on immune function, particularly in the regulation of T cell responses. Future work should focus expanding the limited knowledge in this field. Comprehending these modifications will be essential for devising effective strategies to safeguard the health of astronauts during extended space missions. Conclusion: The effects of simulated space stressors on CD4+ T cell function are substantial, implying that space travel poses a potential threat to immune health. Additional research is necessary to investigate the intricate relationship between space stressors and to develop effective countermeasures to mitigate these consequences.

Human cranial bone-derived mesenchymal stem cells cultured under simulated microgravity can improve cerebral infarction in rats.

The efficacy of transplanting human cranial bone-derived mesenchymal stem cells (hcMSCs) cultured under simulated microgravity (sMG) conditions has been previously reported; however, their effect on cerebral infarction remains unknown. Here, we examined the efficacy of transplanting hcMSCs cultured in an sMG environment into rat models of cerebral infarction. For evaluating neurological function, hcMSCs cultured in either a normal gravity (1G) or an sMG environment were transplanted in rats 1 day after inducing cerebral infarction. The expression of endogenous neurotrophic, axonal, neuronal, synaptogenic, angiogenic, and apoptosis-related factors in infarcted rat brain tissue was examined using real-time polymerase chain reaction and western blotting 35 days after stroke induction. The RNAs of hcMSCs cultured under 1G or sMG environments were sequenced. The results showed that neurological function was significantly improved after transplantation of hcMSCs from the sMG group compared with that from the 1G group. mRNA expressions of nerve growth factor, fibroblast growth factor 2, and synaptophysin were significantly higher in the sMG group than in the 1G group, whereas sortilin 1 expression was significantly lower. RNA sequencing analysis revealed that genes related to cell proliferation, angiogenesis, neurotrophy, neural and synaptic organization, and inhibition of cell differentiation were significantly upregulated in the sMG group. In contrast, genes promoting microtubule and extracellular matrix formation and cell adhesion, signaling, and differentiation were downregulated. These results demonstrate that hcMSCs cultured in the sMG environment may be a useful source of stem cells for the recovery of neurological function after cerebral infarction.

Simulated weightlessness procedure, head-down bed rest has reversible effects on the metabolism of rhesus macaque.

It is a consensus in the international manned space field that factors such as microgravity during the space flight can cause anxiety, depression and other important brain function abnormalities in astronauts. However, the neural mechanism at the molecular level is still unclear. Due to the limitations of research conditions, studies of biological changes in the primate brain have been comparatively few. We took advantage of -6° head-down bed rest (HDBR), one of the most implemented space analogues on the ground, to investigate the effects of simulated weightlessness on non-human primate brain metabolites. The Rhesus Macaque monkeys in the experiment were divided into three groups: the control group, the 42-day simulated weightlessness group with HDBR, and the recovery group, which had 28 days of free activity in the home cage after the HDBR. Liquid chromatography-mass spectrometry (LC-MS) was used to perform metabolomics analysis on specific brain areas of the monkeys under three experimental conditions. Our results show that simulated weightlessness can cause neurotransmitter imbalances, the amino acid and energy metabolism disorders, and hormone disturbances. But these metabolomics changes are reversible after recovery. Our study suggests that long-term brain damage in space flight might be reversible at the metabolic level. This lays a technical foundation for ensuring brain health and enhancing the brain function in future space studies.

Simulated microgravity-induced dysregulation of cerebrospinal fluid immune homeostasis by disrupting the blood-cerebrospinal fluid barrier.

BACKGROUND: The blood-cerebrospinal fluid barrier (BCSFB) comprises the choroid plexus epithelia. It is important for brain development, maintenance, function, and especially for maintaining immune homeostasis in the cerebrospinal fluid (CSF). Although previous studies have shown that the peripheral immune function of the body is impaired upon exposure to microgravity, no studies have reported changes in immune cells and cytokines in the CSF that reflect neuroimmune status. The purpose of this study is to investigate the alterations in cerebrospinal fluid (CSF) immune homeostasis induced by microgravity and its mechanisms. This research is expected to provide basic data for brain protection of astronauts during spaceflight. METHODS: The proportions of immune cells in the CSF and peripheral blood (PB) of SMG rats were analyzed using flow cytometry. Immune function was evaluated by measuring cytokine concentrations using the Luminex method. The histomorphology and ultrastructure of the choroid plexus epithelia were determined. The concentrations of intercellular junction proteins in choroid plexus epithelial cells, including vascular endothelial-cadherin (VE-cadherin), zonula occludens 1 (ZO-1), Claudin-1 and occludin, were detected using western blotting and immunofluorescence staining to characterize BCSFB injury. RESULTS: We found that SMG caused significant changes in the proportion of CD4 and CD8 T cells in the CSF and a significant increase in the levels of cytokines (GRO/KC, IL-18, MCP-1, and RANTES). In the PB, there was a significant decrease in the proportion of T cells and NKT cells and a significant increase in cytokine levels (GRO/KC, IL-18, MCP-1, and TNF-α). Additionally, we observed that the trends in immune markers in the PB and CSF were synchronized within specific SMG durations, suggesting that longer SMG periods (≥21 days) have a more pronounced impact on immune markers. Furthermore, 21d-SMG resulted in ultrastructural disruption and downregulated expression of intercellular junction proteins in rat choroid plexus epithelial cells. CONCLUSIONS: We found that SMG disrupts the BCSFB and affects the CSF immune homeostasis. This study provides new insights into the health protection of astronauts during spaceflight.

Salidroside alleviates simulated microgravity-induced bone loss by activating the Nrf2/HO-1 pathway.

BACKGROUND: Bone loss caused by microgravity exposure presents a serious threat to the health of astronauts, but existing treatment strategies have specific restrictions. This research aimed to investigate whether salidroside (SAL) can mitigate microgravity-induced bone loss and its underlying mechanism. METHODS: In this research, we used hindlimb unloading (HLU) and the Rotary Cell Culture System (RCCS) to imitate microgravity in vivo and in vitro. RESULTS: The results showed that salidroside primarily enhances bone density, microstructure, and biomechanical properties by stimulating bone formation and suppressing bone resorption, thereby preserving bone mass in HLU rats. In MC3T3-E1 cells cultured under simulated microgravity in rotary wall vessel bioreactors, the expression of osteogenic genes significantly increased after salidroside administration, indicating that salidroside can promote osteoblast differentiation under microgravity conditions. Furthermore, the Nrf2 inhibitor ML385 diminished the therapeutic impact of salidroside on microgravity-induced bone loss. Overall, this research provides the first evidence that salidroside can mitigate bone loss induced by microgravity exposure through stimulating the Nrf2/HO-1 pathway. CONCLUSION: These findings indicate that salidroside has great potential for treating space-related bone loss in astronauts and suggest that Nrf2/HO-1 is a viable target for counteracting microgravity-induced bone damage.

Omics Studies of Specialized Cells and Stem Cells under Microgravity Conditions.

The primary objective of omics in space with focus on the human organism is to characterize and quantify biological factors that alter structure, morphology, function, and dynamics of human cells exposed to microgravity. This review discusses exciting data regarding genomics, transcriptomics, epigenomics, metabolomics, and proteomics of human cells and individuals in space, as well as cells cultured under simulated microgravity. The NASA Twins Study significantly heightened interest in applying omics technologies and bioinformatics in space and terrestrial environments. Here, we present the available publications in this field with a focus on specialized cells and stem cells exposed to real and simulated microgravity conditions. We summarize current knowledge of the following topics: (i) omics studies on stem cells, (ii) omics studies on benign specialized different cell types of the human organism, (iii) discussing the advantages of this knowledge for space commercialization and exploration, and (iv) summarizing the emerging opportunities for translational regenerative medicine for space travelers and human patients on Earth.

Cultivation in long-term simulated microgravity is detrimental to pyocyanin production and subsequent biofilm formation ability of Pseudomonas aeruginosa.

Pseudomonas aeruginosa forms aggregates known as biofilms. Previous studies have shown that when P. aeruginosa is cultivated in space, thicker and structurally different biofilms are formed than from those grown on Earth. We investigated how microgravity, simulated in a laboratory setting, influenced the growth, colonization, and virulence potentials of a P. aeruginosa PA14 wild-type strain, as well as two surface attachment-defective (sad) mutants altered at crucial biofilm-forming steps: flgK and pelA. Using high-aspect ratio rotating-wall vessel (HARV) bioreactors, P. aeruginosa bacteria were grown to stationary phase under prolonged (6 days) exposure to simulated microgravity or normal gravity conditions. After the exposure, the capacity of the culture to form biofilms was measured. Additionally, pigment (pyocyanin) formed by each culture during the incubation was extracted and quantified. We demonstrate that the first prolonged exposure to low-shear modeled microgravity (LSMMG) and without nutrient replenishment significantly diminishes wild-type P. aeruginosa PA14 biofilm formation abilities after exposure and pyocyanin production during exposure, while the mutant strains exhibit differing outcomes for both properties. IMPORTANCE: Given plans for humans to engage in prolonged space travel, we investigated biofilm and pigment/virulence factor formation in Pseudomonas aeruginosa when cultivated in microgravity. These bacteria are opportunistic pathogens in immunocompromised individuals. Previous studies of space travelers have shown some immune system diminutions. Hence, our studies shed some light on how prolonged cultivation of bacteria in simulated microgravity conditions affect their growth characteristics.

Response of Staphylococcus aureus physiology and Agr quorum sensing to low-shear modeled microgravity.

Staphylococcus aureus is commonly isolated from astronauts returning from spaceflight. Previous analysis of omics data from S. aureus low Earth orbit cultures indicated significantly increased expression of the Agr quorum sensing system and its downstream targets in spaceflight samples compared to ground controls. In this current study, the rotary cell culture system (RCCS) was used to investigate the effect of low-shear modeled microgravity (LSMMG) on S. aureus physiology and Agr activity. When cultured in the same growth medium and temperature as the previous spaceflight experiment, S. aureus LSMMG cultures exhibited decreased agr expression and altered growth compared to normal gravity control cultures, which are typically oriented with oxygenation membrane on the bottom of the high aspect rotating vessel (HARV). When S. aureus was grown in an inverted gravity control orientation (oxygenation membrane on top of the HARV), reduced Agr activity was observed relative to both traditional control and LSMMG cultures, signifying that oxygen availability may affect the observed differences in Agr activity. Metabolite assays revealed increased lactate and decreased acetate excretion in both LSMMG and inverted control cultures. Secretomics analysis of LSMMG, control, and inverted control HARV culture supernatants corroborated these results, with inverted and LSMMG cultures exhibiting a decreased abundance of Agr-regulated virulence factors and an increased abundance of proteins expressed in low-oxygen conditions. Collectively, these studies suggest that the orientation of the HARV oxygenation membrane can affect S. aureus physiology and Agr quorum sensing in the RCCS, a variable that should be considered when interpreting data using this ground-based microgravity model.IMPORTANCES. aureus is commonly isolated from astronauts returning from spaceflight and from surfaces within human-inhabited closed environments such as spacecraft. Astronaut health and immune function are significantly altered in spaceflight. Therefore, elucidating the effects of microgravity on S. aureus physiology is critical for assessing its pathogenic potential during long-term human space habitation. These results also highlight the necessity of eliminating potential confounding factors when comparing simulated microgravity model data with actual spaceflight experiments.

Effects of Ginsenoside Rb1 on the Crosstalk between Intestinal Stem Cells and Microbiota in a Simulated Weightlessness Mouse Model.

Exposure to the space microenvironment has been found to disrupt the homeostasis of intestinal epithelial cells and alter the composition of the microbiota. To investigate this in more detail and to examine the impact of ginsenoside Rb1, we utilized a mouse model of hindlimb unloading (HU) for four weeks to simulate the effects of microgravity. Our findings revealed that HU mice had ileum epithelial injury with a decrease in the number of intestinal stem cells (ISCs) and the level of cell proliferation. The niche functions for ISCs were also impaired in HU mice, including a reduction in Paneth cells and Wnt signaling, along with an increase in oxidative stress. The administration of Rb1 during the entire duration of HU alleviated the observed intestinal defects, suggesting its beneficial influence on epithelial cell homeostasis. Hindlimb unloading also resulted in gut dysbiosis. The supplementation of Rb1 in the HU mice or the addition of Rb1 derivative compound K in bacterial culture in vitro promoted the growth of beneficial probiotic species such as Akkermansia. The co-housing experiment further showed that Rb1 treatment in ground control mice alone could alleviate the defects in HU mice that were co-housed with Rb1-treated ground mice. Together, these results underscore a close relationship between dysbiosis and impaired ISC functions in the HU mouse model. It also highlights the beneficial effects of Rb1 in mitigating HU-induced epithelial injury by promoting the expansion of intestinal probiotics. These animal-based insights provide valuable knowledge for the development of improved approaches to maintaining ISC homeostasis in astronauts.

Simulated Microgravity Alters Gene Regulation Linked to Immunity and Cardiovascular Disease.

Microgravity exposure induces a cephalad fluid shift and an overall reduction in physical activity levels which can lead to cardiovascular deconditioning in the absence of countermeasures. Future spaceflight missions will expose crew to extended periods of microgravity among other stressors, the effects of which on cardiovascular health are not fully known. In this study, we determined cardiac responses to extended microgravity exposure using the rat hindlimb unloading (HU) model. We hypothesized that exposure to prolonged simulated microgravity and subsequent recovery would lead to increased oxidative damage and altered expression of genes involved in the oxidative response. To test this hypothesis, we examined hearts of male (three and nine months of age) and female (3 months of age) Long-Evans rats that underwent HU for various durations up to 90 days and reambulated up to 90 days post-HU. Results indicate sex-dependent changes in oxidative damage marker 8-hydroxydeoxyguanosine (8-OHdG) and antioxidant gene expression in left ventricular tissue. Three-month-old females displayed elevated 8-OHdG levels after 14 days of HU while age-matched males did not. In nine-month-old males, there were no differences in 8-OHdG levels between HU and normally loaded control males at any of the timepoints tested following HU. RNAseq analysis of left ventricular tissue from nine-month-old males after 14 days of HU revealed upregulation of pathways involved in pro-inflammatory signaling, immune cell activation and differential expression of genes associated with cardiovascular disease progression. Taken together, these findings provide a rationale for targeting antioxidant and immune pathways and that sex differences should be taken into account in the development of countermeasures to maintain cardiovascular health in space.

[Effect of Collagen Peptides on Function of Mouse T Lymphocytes under Simulated Microgravity].

OBJECTIVE: To understand the effect of collagen peptides on the function of mouse lymphocytes under simulated microgravity. METHODS: The splenocytes of mice were isolated, and the rotary cell culture system was used to simulate the microgravity. The T lymphocytes were stimulated with mitotic agents, concanavalin A (ConA), and the cells were treated with different concentrations of collagen peptides. The proliferation of lymphocytes and the levels of cytokines in the supernatant were detected. RESULTS: Simulated microgravity could inhibit the proliferation of spleen T lymphocytes and decrease the level of cytokines in the supernatant. Collagen peptides could promote the lymphocyte proliferation and cytokine production in cells cultured under simulated microgravity. CONCLUSION: Collagen peptides may attenuate the inhibitory effect of simulated microgravity on T lymphocytes by regulating the cell proliferation and the secretion of cytokines.

A simulated microgravity-oriented AIE probe-ECM hydrogel-integrated chip for cell culture and superoxide anion radical detection.

Human space activities have been continuously increasing. Astronauts experiencing spaceflight are faced with health problems caused by special space environments such as microgravity, and the investigation of cell injury is fundamental. The development of a platform capable of cell culture and injury detection is the prerequisite for the investigation. Constructing a platform suitable for special conditions in space life science research is the key issue. The ground-based investigation is an indispensable part of the research. Accordingly, a simulated microgravity (SMG)-oriented integrated chip platform capable of 3D cell culture and in situ visual detection of superoxide anion radical (O2•-) is developed. SMG can cause oxidative stress in human cells, and O2•- is one of the signaling molecules. Thus, a O2•--responsive aggregation-induced emission (AIE) probe is designed, which shows high selectivity and sensitivity to O2•-. Moreover, the probe exhibits abilities of long-term and wash-free staining to cells due to the AIE behavior, which is precious for space cell imaging. Meanwhile, a chip with a high-aspect-ratio chamber for adequate medium storage for the lack of the perfusion system during the SMG experiment and a cell culture chamber which can integrate the extracellular matrix (ECM) hydrogel for the bioinspired 3D cell culture is fabricated. In addition, a porous membrane is introduced between the chambers to prevent the hydrogel from separating during the SMG experiment. The afforded AIE probe-ECM hydrogel-integrated chip can achieve 3D culturing of U87-MG cells and in situ fluorescent detection of endogenous O2•- in the cells after long-term staining under SMG. The chip provides a powerful and potential platform for ground-based investigation in space life science and biomedical research.

Numerical analysis of blood flow in the abdominal aorta under simulated weightlessness and earth conditions.

Blood flow through the abdominal aorta and iliac arteries is a crucial area of research in hemodynamics and cardiovascular diseases. To get in to the problem, this study presents detailed analyses of blood flow through the abdominal aorta, together with left and right iliac arteries, under Earth gravity and weightless conditions, both at the rest stage, and during physical activity. The analysis were conducted using ANSYS Fluent software. The results indicate, that there is significantly less variation in blood flow velocity under weightless conditions, compared to measurement taken under Earth Gravity conditions. Study presents, that the maximum and minimum blood flow velocities decrease and increase, respectively, under weightless conditions. Our model for the left iliac artery revealed higher blood flow velocities during the peak of the systolic phase (systole) and lower velocities during the early diastolic phase (diastole). Furthermore, we analyzed the shear stress of the vessel wall and the mean shear stress over time. Additionally, the distribution of oscillatory shear rate, commonly used in hemodynamic analyses, was examined to assess the effects of blood flow on the blood vessels. Countermeasures to mitigate the negative effects of weightlessness on astronauts health are discussed, including exercises performed on the equipment aboard the space station. These exercises aim to maintain optimal blood flow, prevent the formation of atherosclerotic plaques, and reduce the risk of cardiovascular complications.

Cardiovascular adaptations in microgravity conditions.

Gravity has had a significant impact on the evolution of life on Earth with organisms developing necessary biological adaptations over billions of years to counter this ever-existing force. There has been an exponential increase in experiments using real and simulated gravity environments in the recent years. Although an understanding followed by discovery of counter measures to negate diminished gravity in space had been the driving force of research initially, there has since been a phenomenal leap wherein a force unearthly as microgravity is beginning to show promising potential. The current review summarizes pathophysiological changes that occur in multiple aspects of the cardiovascular system when exposed to an altered gravity environment leading to cardiovascular deconditioning and orthostatic intolerance. Gravity influences not just the complex multicellular systems but even the survival of organisms at the molecular level by intervening fundamental cellular processes, directly affecting those linked to actin and microtubule organization via mechano-transduction pathways. The reach of gravity ranges from cytoskeletal rearrangement that regulates cell adhesion and migration to intracellular dynamics that dictate cell fate commitment and differentiation. An understanding that microgravity itself is not present on Earth propels the scope of simulated gravity conditions to be a unique and useful environment that could be explored for enhancing the potential of stem cells for a wide range of applications as has been highlighted here.

PIEZO1 Promotes the Migration of Endothelial Cells via Enhancing CXCR4 Expression under Simulated Microgravity.

Exposure to microgravity during spaceflight induces the alterations in endothelial cell function associated with post-flight cardiovascular deconditioning. PIEZO1 is a major mechanosensitive ion channel that regulates endothelial cell function. In this study, we used a two-dimensional clinostat to investigate the expression of PIEZO1 and its regulatory mechanism on human umbilical vein endothelial cells (HUVECs) under simulated microgravity. Utilizing quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis, we observed that PIEZO1 expression was significantly increased in response to simulated microgravity. Moreover, we found microgravity promoted endothelial cells migration by increasing expression of PIEZO1. Proteomics analysis highlighted the importance of C-X-C chemokine receptor type 4(CXCR4) as a main target molecule of PIEZO1 in HUVECs. CXCR4 protein level was increased with simulated microgravity and decreased with PIEZO1 knock down. The mechanistic study showed that PIEZO1 enhances CXCR4 expression via Ca2+ influx. In addition, CXCR4 could promote endothelial cell migration under simulated microgravity. Taken together, these results suggest that the upregulation of PIEZO1 in response to simulated microgravity regulates endothelial cell migration due to enhancing CXCR4 expression via Ca2+ influx.

The adaptation of 3T3 cells to simulated microgravity by retrieving the major cell cycle-related protein expression during long-term in vitro proliferation.

The present study aimed to assess the effects of simulated microgravity (SMG) on 3T3 cell proliferation and the expression of cell cycle regulators. 3T3 cells were induced to SMG by Gravite® for 8 days, while the control group was treated with 1G condition. The result showed that the SMG condition causes a decrease in proliferative activity in 3T3 cells. In the SMG group, the expression of cell cycle-related proteins was lower than the control on day 3. However, these proteins were upregulated in 3T3 cells of the SMG group on day 5, suggesting that these cells were rescued from the arrest and retrieved a higher proliferation. A down-regulation of cell cycle-related proteins was observed in 3T3 cells of both SMG and control groups on day 7. In conclusion, SMG results in the attenuation of cell proliferation during the initial exposure to SMG, but the cells will adapt to this condition and retrieve normal proliferation by increasing the expression of cell cycle regulators.

Integration of Proteomic and Metabolomic Data Reveals the Lipid Metabolism Disorder in the Liver of Rats Exposed to Simulated Microgravity.

Long-term exposure to microgravity is considered to cause liver lipid accumulation, thereby increasing the risk of non-alcoholic fatty liver disease (NAFLD) among astronauts. However, the reasons for this persistence of symptoms remain insufficiently investigated. In this study, we used tandem mass tag (TMT)-based quantitative proteomics techniques, as well as non-targeted metabolomics techniques based on liquid chromatography-tandem mass spectrometry (LC-MS/MS), to comprehensively analyse the relative expression levels of proteins and the abundance of metabolites associated with lipid accumulation in rat liver tissues under simulated microgravity conditions. The differential analysis revealed 63 proteins and 150 metabolites between the simulated microgravity group and the control group. By integrating differentially expressed proteins and metabolites and performing pathway enrichment analysis, we revealed the dysregulation of major metabolic pathways under simulated microgravity conditions, including the biosynthesis of unsaturated fatty acids, linoleic acid metabolism, steroid hormone biosynthesis and butanoate metabolism, indicating disrupted liver metabolism in rats due to weightlessness. Finally, we examined differentially expressed proteins associated with lipid metabolism in the liver of rats exposed to stimulated microgravity. These findings contribute to identifying the key molecules affected by microgravity and could guide the design of rational nutritional or pharmacological countermeasures for astronauts.