Evaluation of dioxin induced transcriptomic responses in a 3D human liver microtissue model

Three-dimensional human liver microtissue model provides a promising method for predicting the human hepatotoxicity of environmental chemicals. However, the dynamics of transcriptional responses of 3D human liver microtissue model to dioxins exposure remain unclear. Herein, time-series transcriptomic analysis was used to characterize modulation of gene expression over 14 days in 3D human liver microtissues exposed to 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD, 31 nM, 10 ng/ml). Changes in gene expression and modulation of biological pathways were evaluated at several time points. The results showed that microtissues stably expressed genes related to toxicological pathways (e.g. highly of genes involved in external stimuli and maintenance of cell homeostasis pathways) during the 14-day culture period. Furthermore, a weekly phenomenon pattern was observed for the number of the differentially expressed genes in microtissues exposed to TCDD at each time point. TCDD led to an induction of genes involved in cell cycle regulation at day three. Metabolic pathways were the main significantly induced pathways during the subsequent days, with the immune/inflammatory response enriched on the fifth day, and the cellular response to DNA damage was identified at the end of the exposure. Finally, relevant transcription patterns identified in microtissues were compared with published data on rodent and human cell-line studies to elucidate potential species-specific responses to TCDD over time. Cell development and cytochrome P450 pathway were mainly affected after a 3-day exposure, with the DNA damage response identified at the end of exposure in the human microtissue system but not in mouse/rat primary hepatocytes models. Overall, the 3D human liver microtissue model is a valuable tool to predict the toxic effects of environmental chemicals with a relatively long exposure.