Ambient Temperature Preservation Supports Recovery of Beating Capacity in Human Cardiac Organoids After Exposure to Simulated Space Stressors

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.