Abstract
Graphical abstractMicrogravity (MG) effect is a weightlessness phenomenon caused by the distance from the ground or low gravity of other planets outside the earth’s atmosphere. The various effects of MG have been corroborated in human and animal studies and modeled in cell-based analogs. However, the impact of MG on siRNA performance remains to be elucidated, which is crucial for aerospace medicine. In this study, we prepared nucleic acid nanomicelles (EAASc/siRNA) by using tri-block copolymer of PEG45-PAMA40-P(C7A36-DBA37) (EAASc) and siRNA and explored its working mechanism under simulated microgravity (SMG) condition generated by a random positioning machine (RPM). The binding ability of EAASc to siRNA and silence activity were firstly confirmed in normal gravity (NG) environment. Evaluation of PLK1 mRNA expression revealed that gene inhibition efficiencies were increased by 28.7% (HepG2) and 28.9% (A549) under SMG condition, compared with those under NG condition. In addition, mechanism exploration indicated that morphology and migration capability of cancer cells were significantly changed, the internalization of EAASc/siRNA by cells was magnified when the cells were incubated with RPM. No significant difference was observed regarding the expression profiles of genes involved in RNA interference (RNAi) pathway, including Ago2, Dicer, TRBP, and so on. Taken together, siRNA activity was elevated under SMG condition owning to increased cellular internalization. This study, for the first time to our knowledge, provides valuable theory for development and application of siRNA therapeutic in space in the future.
Highlights
In the process of the rapid development of human demand for space exploration, the impact of the extreme environment on astronauts has attracted much attention (Egorov 1996; Ohta et al 2002), which has become the biggest challenge for long-term human habitation and space exploration
Before exploring the effects of microgravity on Small interfering RNA (siRNA) transfection and gene silence, we need to confirm that the polymer used in this study has excellent siRNA transfection efficiency under normal gravity (NG) condition
It is reported that pKa value or pH-responsive property of delivery carrier plays essential role in delivering siRNA and mediating efficient endosomal escape (Du et al 2018; Whitehead et al 2014; Zhou et al 2016)
Summary
In the process of the rapid development of human demand for space exploration, the impact of the extreme environment on astronauts has attracted much attention (Egorov 1996; Ohta et al 2002), which has become the biggest challenge for long-term human habitation and space exploration. Microgravity environment can affect the growth and process of tumor cells (Jhala et al 2014), leading to changes in the phenotype and characteristics of breast cancer (Bauer et al 2018; Masiello et al 2014), the differentiation and apoptosis status of follicular thyroid carcinoma cells (Grimm et al 2002), and the metastasis of lung cancer (Ahn et al 2019; Eyal and Derendorf 2019) This series of changes together may significantly affect the treatment effect of certain therapeutics in space. Theory exploration and technique platform establishment are of essential importance for drug development and application in space
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