Enhanced self-renewal of human pluripotent stem cells by simulated microgravity

We developed a fast-rotating clinostat to simulate micrigravity (µg) and investigated various effects (including proliferation, self-renewal, and cell cycle regulation) of simulated microgravity (sµg) on human pluripotent stem cells (hPSC). Cells were cultured in sµg and control condition in normal gravity (1g). We observed significant upregulation of protein translation of human pluripotency transcription factors in hPSC cultured in sµg condition compared to 1g. We also noted a significant increase in the expression levels of genes involved in telomere elongation. Our induced differentiation experiments showed that hPSC cultured in sµg condition were less susceptible towards differentiation compared to cells cultured in 1g condition as indicated by the significant delayed in the process of differentiation of the cell in sµg condition. These results suggest that sµg conditions enhance the self-renewal of hPSC. Our study further revealed that sµg enhanced the cell proliferation of hPSC by regulating the expression of cell cycle associated kinases. Moreover, RNAseq analysis indicated that in sµg condition the expression of pathways related to differentiation and development and down-regulated, while multiple components of the ubiquitin proteasome system are up-regulated, thus further contributing to an enhanced self-renewal of hPSC. These effects of sµg were not replicated in human fibroblasts. Taken together, these results highlight pathways and mechanisms in hPSC vulnerable to µg that impose significant impacts on human health and performance, physiology, and cellular and molecular processes. We performed a comparative gene expression profiling analysis of RNA-seq data for H1 and H9 human pluripotent stem cells after culturing them under normal gravity (1g) and simulated microgravity (near zero gravity).