Mouse organoids as an in vitro tool to study the in vivo intestinal response to cytotoxicants.

Cross-species comparison of drug responses at the organoid level could help to determine the human relevance of findings from animal studies. To this end, we first need to evaluate the in vitro to in vivo translatability of preclinical organoids. Here, we used 5-fluorouracil (5-FU) as an exemplar drug to test whether the in vivo gut response to this cytotoxicant was preserved in murine intestinal organoids. Mice treated with 5-FU at 20 or 50 mg/kg IV (low and high dose, respectively) displayed diarrhea at clinically relevant exposures. 5-FU also induced intestinal lesions, increased epithelial apoptosis, and decreased proliferation in a dose-dependent manner. To enable comparison between the in vitro and in vivo response, top nominal in vitro drug concentrations that caused significant cytotoxicity were chosen (dose range 1-1000 µM). The inferred intracellular concentration in organoids at 1000 µM was within the tissue exposure range related to intestinal toxicity in vivo. 5-FU at ≥ 100 µM decreased ATP levels and increased Caspase-3 activity in intestinal organoids. In keeping with the in vivo findings, 5-FU increased the percentage of Caspase-3-positive cells and reduced Ki67 staining. At the transcriptome level, there was an overlap in the activity of pathways related to 5-FU's mode of action, lipid and cholesterol metabolism and integrin signaling across in vivo gut and organoids. The predicted activity state of upstream regulators was generally well preserved between setups. Collectively, our results suggest that despite their inherent limitations, organoids represent an adequate tool to explore the intestinal response to cytotoxicants.