3Rs Quarterly

Humans are exposed to combinations of chemicals. Regulatory bodies consider dose addition of chemicals as sufficiently conservative for risk assessment. In this paper, researchers at RIVM studied whether this concept of dose addition holds for complex mixtures. This is done by testing these mixtures in zebrafish embryos, taking craniofacial malformations as read-out. The cumulative effect of the chemicals in the mixture was in accordance with dose addition. This case study shows that this pipeline can be useful for cumulative risk assessment in general.

There is a need for human-relevant, new approach methods that can predict the potential developmental neurotoxic effects of compounds. Researchers of RIVM showed that the hNPT, an in vitro culture of stem cell-derived neurons and astrocytes, can mimic some cellular biological processes relevant for neurodevelopment. These processes could be perturbed by known neurotoxic compounds. Combined with other new approach methods, prediction of developmental neurotoxicity of compounds may be feasible.

Stem cell-based in vitro models are valuable tools for developmental toxicity assessment. A group of experts, including from RIVM, reviewed available models from 1533 publications, resulting in an overview of all assays and their features, including e.g. readout endpoint, reproducibility and predictive power. The biology represented in the assays and the chemical domain that can be tested mark opportunities and limitations for their applicability. The continuing attention to these models shows their central place as a tool in animal-free developmental toxicity testing.

An adverse outcome pathway (AOP) provides a pragmatic description of causally linked biological effects leading from a molecular perturbation to adverse health effects. RIVM, currently co-chair of the HESI Genetic Toxicology Technical Committee, contributed to the development of an AOP network that links oxidative DNA damage to two adverse outcomes: mutations and chromosomal aberrations. Additional genotoxicity-associated AOPs can be built upon this AOP network and aid in designing novel integrated testing approaches for genotoxicity assessment.

In this publication, the European Horizon 2020 project RISK-HUNT3R (“Risk assessment of chemicals integrating human-centric next-generation testing strategies promoting the 3Rs”) delineates its strategy to establish a Next Generation Risk Assessment (NGRA) framework for chemicals, pesticides and cosmetics. RISK-HUNT3R is designed to deliver a sustainable NGRA framework, using a comprehensive toolbox of mechanism-based, human-relevant New Approach Methodologies, aiming to develop faster, more accurate chemical risk assessments.

Over recent years, an increasing number of 3R centres and platforms have been established. These initiatives facilitate development of non-animal models in basic, regulatory and applied science, dissemination of knowledge on 3R methods, and implementation of 3R principles in regulations, policy and education. Together with European 3R initiative representatives, RIVM contributed to a publication that provides an overview of the historical development of 3R centres and platforms.

Working towards animal-free research strategies is an effort crossing international and interdisciplinary borders. TPI.tv is designed to facilitate this transition through connecting people and ideas via video messages. On TPI.tv, short video messages (‘pitches’) provide the medium for researchers to display their findings and request input if needed. New videos on TPI.tv:

Neural tube closure in silico | Next generation carcinogenicity testing | Zebrafish for toxicity testing