A spaceflight to the International Space Station (ISS) is a dream of many researchers. We had the chance to investigate the effect of real microgravity (CellBox-2 Space mission) on the transcriptome and proteome of FTC-133 human follicular thyroid cancer cells (TCC). The cells had been sent to the ISS by a Falcon 9 rocket of SpaceX CRS-13 from Cape Canaveral (United States) and cultured in six automated hardware units on the ISS before they were fixed and returned to Earth. Multicellular spheroids (MCS) were detectable in all spaceflight hardware units. The VCL, PXN, ITGB1, RELA, ERK1 and ERK2 mRNA levels were significantly downregulated after 5 days in space in adherently growing cells (AD) and MCS compared with ground controls (1g), whereas the MIK67 and SRC mRNA levels were both suppressed in MCS. By contrast, the ICAM1, COL1A1 and IL6 mRNA levels were significantly upregulated in AD cells compared with 1g and MCS. The protein secretion measured by multianalyte profiling technology and enzyme-linked immunosorbent assay (AngiogenesisMAP^®, extracellular matrix proteins) was not significantly altered, with the exception of elevated angiopoietin 2. TCC in space formed MCS, and the response to microgravity was mainly anti-proliferative. We identified ERK/RELA as a major microgravity regulatory pathway.

Human spaceflight is associated with several health-related issues as a result of long-term exposure to microgravity, ionizing radiation, and higher levels of psychological stress. Frequent reported skin problems in space include rashes, itches, and a delayed wound healing. Access to space is restricted by financial and logistical issues; as a consequence, experimental sample sizes are often small, which limits the generalization of the results. Earth-based simulation models can be used to investigate cellular responses as a result of exposure to certain spaceflight stressors. Here, we describe the development of an in vitro model of the simulated spaceflight environment, which we used to investigate the combined effect of simulated microgravity using the random positioning machine (RPM), ionizing radiation, and stress hormones on the wound-healing capacity of human dermal fibroblasts. Fibroblasts were exposed to cortisol, after which they were irradiated with different radiation qualities (including X-rays, protons, carbon ions, and iron ions) followed by exposure to simulated microgravity using a random positioning machine (RPM). Data related to the inflammatory, proliferation, and remodeling phase of wound healing has been collected. Results show that spaceflight stressors can interfere with the wound healing process at any phase. Moreover, several interactions between the different spaceflight stressors were found. This highlights the complexity that needs to be taken into account when studying the effect of spaceflight stressors on certain biological processes and for the aim of countermeasures development.

Stem cells contained within the dental mesenchymal stromal cell (MSC) population are crucial for tissue homeostasis. Assuring their genomic stability is therefore essential. Exposure of stem cells to ionizing radiation (IR) is potentially detrimental for normal tissue homeostasis. Although it has been established that exposure to high doses of ionizing radiation (IR) has severe adverse effects on MSCs, knowledge about the impact of low doses of IR is lacking. Here we investigated the effect of low doses of X-irradiation with medical imaging beam settings (<0.1 Gray; 900 mGray per hour),in vitro, on pediatric dental mesenchymal stromal cells containing dental pulp stem cells from deciduous teeth, dental follicle progenitor cells and stem cells from the apical papilla. DNA double strand break (DSB) formation and repair kinetics were monitored by immunocytochemistry of γH2AX and 53BP1 as well as cell cycle progression by flow cytometry and cellular senescence by senescence-associated β-galactosidase assay and ELISA. Increased DNA DSB repair foci, after exposure to low doses of X-rays, were measured as early as 30 min post-irradiation. The number of DSBs returned to baseline levels 24 h after irradiation. Cell cycle analysis revealed marginal effects of IR on cell cycle progression, although a slight G₂/M phase arrest was seen in dental pulp stromal cells from deciduous teeth 72 h after irradiation. Despite this cell cycle arrest, no radiation-induced senescence was observed. In conclusion, low X-ray IR doses (< 0.1 Gray; 900 mGray per hour), were able to induce significant increases in the number of DNA DSBs repair foci, but cell cycle progression seems to be minimally affected. This highlights the need for more detailed and extensive studies on the effects of exposure to low IR doses on different mesenchymal stromal cells.

As global cancer incidence rises, so does the population of cancer survivors, making long-term and post-treatment quality of life a central clinical concern. Despite modern improvements in treatment, cardiotoxic side effects caused by anthracycline agents and thoracic radiotherapy remain a major clinical challenge. Human iPSC-derived heart organoids offer a promising alternative to animal and 2D in vitro models, but their utility is limited by inter-organoid variability. To address this, we developed reCardioids, a robust heart organoid model generated by dissociation and reaggregation of self-assembling cardioids. Through single-cell transcriptomics, we demonstrated that reCardiods maintain cellular diversity while also exhibiting a more mature cardiomyocyte phenotype compared to non-dissociated cardioids. To validate their utility as a preclinical in vitro model, we evaluated their response after exposure to doxorubicin and clinically relevant doses of γ-radiation. reCardioids successfully modeled doxorubicin-induced cytotoxicity, metabolic decline and altered contractile dynamics. Bulk RNA sequencing following radiation exposure revealed a temporal trajectory of injury, progressing from acute DNA damage through vascular stunting, metabolic dysfunction and eventually compensatory pathological hypertrophic remodeling.

Human space exploration exposes astronauts to environmental stressors including microgravity (µg) and ionizing radiation, which may adversely affect cardiovascular health. Human induced pluripotent stem cell (hiPSC)-derived cardiac organoids, also referred to as cardioids, provide a physiologically relevant model to investigate these effects, but preservation of complex 3D tissues remains challenging. Current methods rely mainly on cryopreservation, creating variability and logistical constraints, particularly for spaceflight research. Alternative preservation strategies suitable for both ground-based and space experiments are therefore needed. In this study, human cardiac organoids were exposed to simulated µg (sµg) using a random positioning machine (RPM) and to a mixed neutron–photon field generated by a Californium-252 (²⁵²Cf) source. To assess preservation potential, organoids preserved at ambient temperature in CellShip^® transport medium were compared with unpreserved controls. Viability, proliferative activity and functional performance, including spontaneous beating, were assessed. Simulated µg induced limited detectable effects, whereas chronic irradiation (dose equivalent rate, 1.31–1.33 mSv/h over 70.5–74.7 h) impaired several organoid viability and functional readouts. Ambient-temperature-preserved organoids showed greater recovery of measurable beating after irradiation than unpreserved organoids. These proof-of-concept findings support further evaluation of CellShip^®-based ambient preservation as a non-cryogenic alternative for cardiac organoids in terrestrial and spaceflight research.