Observation of host cell morphological changes under simulated-microgravity conditions

Abstract Microgravity exposure has been associated with various health concerns, including reports of opportunistic infections. However, the specific changes that occur in host cells under these conditions remain unclear. In this study, we investigated the effect of microgravity on Vero cells and human foreskin fibroblasts (HFFs), which serve as host cells.Under simulated-microgravity conditions, both Vero cells and HFFs formed multicellular spheroids, representing an irreversible change to the viable cells. Moreover, Vero cell proliferation after 7 days of culture under simulated-microgravity conditions was increased compared to normal gravity conditions. Electron microscopy revealed widened intercellular spaces under the simulated-microgravity conditions, indicating morphological changes. RNA sequencing showed no substantial changes in the expression levels of genes related to growth ability. However, some changes in gene expression support the phenomena like reductions in collagen levels, which are reported previously. Our findings suggest that simulated microgravity influences cell morphology and proliferation, and offer insights into maintaining the health of astronauts.