No DNA damage response and negligible genome-wide transcriptional changes in human embryonic stem cells exposed to terahertz radiation

Abstract

Terahertz (THz) radiation was proposed recently for use in various applications, including medical imaging and security scanners. However, there are concerns regarding the possible biological effects of non-ionising electromagnetic radiation in the THz range on cells. Human embryonic stem cells (hESCs) are extremely sensitive to environmental stimuli, and we therefore utilised this cell model to investigate the non-thermal effects of THz irradiation. We studied DNA damage and transcriptome responses in hESCs exposed to narrow-band THz radiation (2.3 THz) under strict temperature control. The transcription of approximately 1% of genes was subtly increased following THz irradiation. Functional annotation enrichment analysis of differentially expressed genes revealed 15 functional classes, which were mostly related to mitochondria. Terahertz irradiation did not induce the formation of γH2AX foci or structural chromosomal aberrations in hESCs. We did not observe any effect on the mitotic index or morphology of the hESCs following THz exposure.

Biological effects of in vitro THz radiation exposure in human foetal fibroblasts

“…Furthermore, few experimental reports demonstrated THzinduced genotoxicity in human lymphocytes [23], phosphorylation of H2AX as consequence of DSBs formation in artificial human skin tissues [30], spindle disturbances in human-hamster hybrid cells [24], or changes in gene expression and activation of apoptosis and necrosis in human dermal fibroblasts and Jurkat cells [34,49]. Conversely, different studies reported no DNA damage after in vitro THz exposure evaluated by the comet assay [20,22,50], by the MN test [20,22], by analysis of H2AX phosphorylation [31] and by the expression of DNA sensing and repair genes [35].…”

“…Besides, an increase in the levels of several proteins involved in cell-cycle regulation and tumor suppression was reported, suggesting that DNA repair mechanisms are quickly activated [30]. Conversely, in a recent study Bogomazova et al, did not recognize the formation of H2AX phosphorylation foci or structural chromosomal aberrations in human embryonic stem cells [31].…”

Biomedical Applications of Terahertz Spectroscopy and Imaging

“…Given that no obvious temperature rise was observed in these studies, most of the results are associated with proposed nonthermal effects of low-level THz irradiation, wherein THz radiation induced lowfrequency collective biomolecular vibrations [90]. However, the most recent evidence indicated no obvious DNA [ 2 2 _ T D $ D I F F ] damages or negligible gene changes for some ranges of THz radiation, such as 2.3 THz [93]; additionally, the observed DNA [ 2 2 _ T D $ D I F F ] damages may be effectively repaired [89]. These controversial results can be attributed to our limited understanding of the nonthermal effects of THz at the biomolecule level because of a lack of applicable modern tools [85].…”

Novosibirsk Free Electron Laser—Facility Description and Recent Experiments

“…The genotoxic action of terahertz radiation on the frequency of induction of DNA double strand breaks in human stem cells was estimated. The ability of terahertz radiation to cause chromosomal aberrations in irradiated cells was studied [45].…”