Simulated microgravity-mediated reversion of murine lymphoma immune evasion

Microgravity and immune cells

The microgravity environment experienced during spaceflight severely impaired immune system, making astronauts vulnerable to various diseases that seriously threaten the health of astronauts. Immune cells are exceptionally sensitive to changes in gravity and the microgravity environment can affect multiple aspects of immune cells through different mechanisms. Previous reports have mainly summarized the role of microgravity in the classification of innate and adaptive immune cells, lacking an overall grasp of the laws that microgravity effects on immune cells at different stages of their entire developmental process, such as differentiation, activation, metabolism, as well as function, which are discussed and concluded in this review. The possible molecular mechanisms are also analysed to provide a clear understanding of the specific role of microgravity in the whole development process of immune cells. Furthermore, the existing methods by which to reverse the damage of immune cells caused by microgravity, such as the use of polysaccharides, flavonoids, other natural immune cell activators etc. to target cell proliferation, apoptosis and impaired function are summarized. This review will provide not only new directions and ideas for the study of immune cell function in the microgravity environment, but also an important theoretical basis for the development of immunosuppression prevention and treatment drugs for spaceflight.

May the Force Be with You (Or Not): The Immune System under Microgravity

All terrestrial organisms have evolved and adapted to thrive under Earth's gravitational force. Due to the increase of crewed space flights in recent years, it is vital to understand how the lack of gravitational forces affects organisms. It is known that astronauts who have been exposed to microgravity suffer from an array of pathological conditions including an impaired immune system, which is one of the most negatively affected by microgravity. However, at the cellular level a gap in knowledge exists, limiting our ability to understand immune impairment in space. This review highlights the most significant work done over the past 10 years detailing the effects of microgravity on cellular aspects of the immune system.

Microgravity, Stem Cells, and Cancer: A New Hope for Cancer Treatment

Humans are integrated with the environment where they live. Gravitational force plays an important role in shaping the universe, lives, and even cellular biological processes. Research in the last 40 years has shown how exposure to microgravity changes biological processes. Microgravity has been shown to have significant effects on cellular proliferation, invasion, apoptosis, migration, and gene expression, specifically in tumor cells, and these effects may also exist in stem and cancer stem cells. It has also been shown that microgravity changes the effects of chemotherapeutic drugs. Although studies have been carried out in a simulated microgravity environment in cell culture lines, there are few animal experiments or true microgravity studies. Cancer remains one of the most significant problems worldwide. Despite advances in medical science, no definitive strategies have been found for the prevention of cancer formation or to inform treatment. Thus, the microgravity environment is a potential new therapeutic strategy for future cancer treatment. This review will focus on current knowledge on the impact of the microgravity environment on cancer cells, stem cells, and the biological behavior of cancer stem cells.

Implications of microgravity-induced cell signaling alterations upon cancer cell growth, invasiveness, metastatic potential, and control by host immunity

The human endeavor to venture beyond the orbit of Earth is challenged by both continuous space radiation and microgravity-induced immune dysfunction. If cancers were to develop in astronauts, it is unclear how these abnormal cells would grow and progress in the microgravity environment. It is unknown if the astronaut's immune response would be able to control or eradicate cancer. A better molecular understanding of how the mechanical force of gravity affects the cell as well as the aggressiveness of cancers and the functionality of host immunity is needed. This review will summarize findings related to microgravity-mediated alterations in the cell cytoskeleton, cell-cell, and cell-extracellular matrix interactions including cadherins, immunoglobulin superfamily of adhesion molecules, selectins, and integrins and related cell signaling. The effects of spaceflight and simulated microgravity on cell viability, cancer cell growth, invasiveness, angiogenesis, metastasis as well as immune cell functions and the subsequent signaling pathways involved will be discussed. Microgravity-induced alterations in function and signaling of the major anti-cancer immune populations will be examined including natural killer cells, dendritic cells, CD4⁺ T cells, and CD8⁺ T cells. Further studies regarding the molecular events impacted by microgravity in both cancer and immune cells will greatly increase the development of therapies to restrict tumor growth and enhance cancer-specific responses for both astronauts and patients on Earth.

Feasibility, potency, and safety of growing human mesenchymal stem cells in space for clinical application

Growing stem cells on Earth is very challenging and limited to a few population doublings. The standard two-dimensional (2D) culture environment is an unnatural condition for cell growth. Therefore, culturing stem cells aboard the International Space Station (ISS) under a microgravity environment may provide a more natural three-dimensional environment for stem cell expansion and organ development. In this study, human-derived mesenchymal stem cells (MSCs) grown in space were evaluated to determine their potential use for future clinical applications on Earth and during long-term spaceflight. MSCs were flown in Plate Habitats for transportation to the ISS. The MSCs were imaged every 24-48 h and harvested at 7 and 14 days. Conditioned media samples were frozen at -80 °C and cells were either cryopreserved in 5% dimethyl sulfoxide, RNAprotect, or paraformaldehyde. After return to Earth, MSCs were characterized to establish their identity and cell cycle status. In addition, cell proliferation, differentiation, cytokines, and growth factors' secretion were assessed. To evaluate the risk of malignant transformation, the space-grown MSCs were subjected to chromosomal, DNA damage, and tumorigenicity assays. We found that microgravity had significant impact on the MSC capacity to secrete cytokines and growth factors. They appeared to be more potent in terms of immunosuppressive capacity compared to their identical ground control. Chromosomal, DNA damage, and tumorigenicity assays showed no evidence of malignant transformation. Therefore, it is feasible and potentially safe to grow MSCs aboard the ISS for potential future clinical applications.

Modeling the Impact of Microgravity at the Cellular Level: Implications for Human Disease

A lack of gravity experienced during space flight has been shown to have profound effects on human physiology including muscle atrophy, reductions in bone density and immune function, and endocrine disorders. At present, these physiological changes present major obstacles to long-term space missions. What is not clear is which pathophysiological disruptions reflect changes at the cellular level versus changes that occur due to the impact of weightlessness on the entire body. This review focuses on current research investigating the impact of microgravity at the cellular level including cellular morphology, proliferation, and adhesion. As direct research in space is currently cost prohibitive, we describe here the use of microgravity simulators for studies at the cellular level. Such instruments provide valuable tools for cost-effective research to better discern the impact of weightlessness on cellular function. Despite recent advances in understanding the relationship between extracellular forces and cell behavior, very little is understood about cellular biology and mechanotransduction under microgravity conditions. This review will examine recent insights into the impact of simulated microgravity on cell biology and how this technology may provide new insight into advancing our understanding of mechanically driven biology and disease.