PURPOSEMicrogravity is known to cause endothelium dysfunction in astronauts returning from spaceflight. We aimed to reveal the regulatory mechanism in alterations of human endothelial cells after simulated microgravity (SMG).

METHODSWe utilized the rotary cell culture system (RCCS-1) to explore the subsequent effects of SMG on human umbilical vein endothelial cells (HUVECs).

RESULTSSMG-treated HUVECs appeared obvious growth inhibition after return to normal gravity, which might be attributed to a set of responses including alteration of cytoskeleton, decreased cell adhesion capacity and increased apoptosis. Expression levels of mTOR and its downstream Apaf-1 were increased during subsequent culturing after SMG. miR-22 was up-regulated and its target genes SRF and LAMC1 were down-regulated at mRNA levels. LAMC1 siRNAs reduced cell adhesion rate and inhibited stress fiber formation while SRF siRNAs caused apoptosis.

CONCLUSIONSMG has the subsequent biological effects on HUVECs, resulting in growth inhibition through mTOR signaling and miR-22-mediated mechanism.