|Exposure duration||continuous for 2, 4, 6 and 9 h|
Lipid droplet-like inclusions appeared in the cellular cytoplasm after 6 hours of exposure. Extended exposure (9 h) resulted in specific changes in cellular functions that are closely related to gene transcription. The biochip data showed that whereas 89% of the genes in mouse stem cells did not respond to the applied terahertz exposure, certain genes are activated (approx. 6% of the genes, upregulation more than two times), while other are repressed (approx. 5% of the genes, downregulation more than two times). RT-PCR experiments with selected gene probes corresponding to transcripts in the three groups of genes (i.e. of upregulated, downregulated genes and unchanged regulation) confirmed the gene specific effect. The response was not only gene specific but also exposure conditions (i.e. exposure duration) dependent.
The findings suggest that the applied terahertz irradiation accelerates cell differentiation toward adipose phenotype by activating the transcription factor peroxisome proliferator-activated receptor gamma (PPARG). Finally, the molecular dynamics computer simulations indicate that the local breathing dynamics of the PPARG promoter DNA coincides with the gene specific response to the terahertz irradiation.
The authors propose that terahertz exposure is a potential tool for cellular reprogramming.