Species-specific Liver Microtissues
The toxicity of substances in animals and humans can be different [1]. For example, fialuridine is more hepatotoxic in humans than in monkeys, dogs, and rats due to the expression of a drug transporter on the mitochondrial membrane in humans [2]. Therefore, understanding the difference in toxicities in different species is key to the safety assessment process of drug candidates.
To this aim, here, microtissues composed of Macaca fascicularis (Cynomolgus), Canis familiaris (Beagle), or Rattus norvegicus (Sprague Dawley) liver cells were developed as in vitro tools to study species-specific drug effects. Liver microtissues are 200 µm spherical in vitro models composed of primary parenchymal and non-parenchymal liver cells co-cultured in a physiological liver ratio [3].
Monkey, dog, and rat liver microtissues are viable and functional for up to 7 days of culture. Interestingly, fialuridine is markedly more cytotoxic in human liver microtissues than in their animal counterparts, hence recapitulating the in vivo observation. In contrast, chlorpromazine, which is not reported to be more hepatotoxic in a specific species, is cytotoxic at similar drug concentrations in all four human, monkey, dog, and rat liver microtissues.
Transcriptomic analysis of fialuridine response in liver microtissues revealed a different signature, specifically in human liver microtissues, with a marked change in genes involved in the response to DNA damage, in agreement with different work highlighting the mutagenesis potential of fialuridine in human hepatocytes [4].
Altogether, this work suggests that species-specific liver microtissues form a set of in vitro tools that can help assess the relative hepatotoxicity and the mechanism of toxicity of a substance in different species. Therefore, species-specific liver microtissues can help drug developers better understand the toxicity of a substance, thereby supporting the development of efficacious and safe drug candidates.
Acknowledgments
Part of these experiments were funded by the Cross-species Consortium, a partnership of pharma and technology providers companies, including AbbVie, Genentech, Takeda, Merck, Sanofi, Pfizer, InSphero, MicroMatrices, and Philip Morris International.
References
[1] Olson, H. et al. Concordance of the Toxicity of Pharmaceuticals in Humans and in Animals. Regulatory Toxicology and Pharmacology 32, 56–67 (2000).
[2] Wang, J. et al. Phosphorylation of the anti-hepatitis B nucleoside analog 1-(2'-deoxy-2'-fluoro-1-beta-D-arabinofuranosyl)-5-iodouracil (FIAU) by human cytosolic and mitochondrial thymidine kinase and implications for cytotoxicity. Antimicrob Agents Chemother. 40(6):1555-7 (1996).
[3] Messner, S. et al. Transcriptomic, Proteomic, and Functional Long-Term Characterization of Multicellular Three-Dimensional Human Liver Microtissues. Applied In Vitro Toxicology, 1-12 (2018).
[4] Aslamkhan, A.G. et al. A mechanistic biomarker investigation of fialuridine hepatotoxicity using the chimeric TK-NOG Hu-liver mouse model and in vitro micropatterned hepatocyte cocultures. Toxicology research, 279(6):4490-7 (2024).
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