Modeling of pathways of developmental neurotoxicity as pilot of a paradigm shift for regulatory safety assessments of chemicals - creation of the ReTox-21c Centre-


Prof. Dr. Thomas Hartung

Johns Hopkins University, 

Doerenkamp-Zbinden-Chair for Evidence-based Toxicology

Centre for Alterntives to Animal Testing (CAAT), Baltimore, USA

Expected Results Benefits, Outputs and Outcome


There is a critical lack of information concerning the effects of chemicals on the developing brain. Current animal based approaches cost $1.4 million per substance. Experts have recommended the development of screening approaches based on alternative in vitro methods. The project aims to comply with this recommendation by developing a rapid systems biology approach for the assessment of developmental neurotoxicity. Expected results will demonstrate the significance of a systems biology approach to assess developmental neurotoxicity in a faster, more scientific and more humane manner. The impact of the project will be the increase in understanding of the developing brain and how chemicals interact with brain development (in vitro and in vivo). Possibly new pathways of developmental neurotoxicity will be identified and biomarkers for its prediction. Moreover, by demonstrating the proof of concept for the systems biology approach, companies or institutes might implement systems biology to replace, reduce or refine animal studies for regulatory DNT assessment.

Since the project includes a human cell system, it might show that human cell systems provide better predictions for human heath effects. Further simplifying the model with reporter gene transfected cells and then in silico modeling will demonstrate whether a feasible battery of in vitro and in silico tests can be envisaged. Toxicology has to undergo a transition in order to meet the challenges of the 21st century. The vision of a toxicity pathway-based approach has been put forward by the NAS [NRC 2007]. It is necessary to create a proof-of-principle. Reproductive toxicity is a key aspect of risk assessment, consuming a large part of resources and animals for the regulation of environmental chemicals. The dimensions of the funding available versus the complexity of the reproductive cycle require focusing on a key area; it is proposed to address DNT, which qualifies as a stand-alone hazard assessment demand and because of its key role in the current change from a two-generation to an extended one-generation study for regulatory purposes.

By bringing together carefully prioritized highly quality-controlled in vitro models, with pathway identification by systems toxicology, with molecular biology derived reporter gene assays, with state-of-the-art in silico modeling and with supervision/advice from leading toxicologist involved in the paradigm shift of toxicology, a unique feasibility study shall be carried out. If successful, this study will serve as a role model for a novel approach to regulatory toxicology.


The proposed work shall:


-        Establish a center ReTox-21c at Johns Hopkins.

Results and benefits: expand the existing competence center in a prime academic environment to leverage for setting into practice the NAS vision; link formally to nationally leading groups

-       Focus on carefully selected models, which reflect crucial mechanisms and targets of DNT, and a list of priority chemicals. A homogenous dataset shall be produced, which allows identification of key cellular pathways.

Results and benefits: Sufficiently large and homogenous datasets in relevant, quality-controlled in vitro models to allow meaningful in silico modeling.


-       This requires a combination of state-of-the art, quality-controlled cell culture with various omic technologies and bioinformatics to establish a systems toxicology approach. 

Results and benefits: translate systems biology to toxicology; objective interpretation of results from information-rich systems

-       Selected pathways shall then be established as reporter gene cells (or acquired where such cells have been already constructed). The original substance set plus a broader selection identified in a consensus process with the DNT consortium shall be tested, taking into consideration the needs of later modeling.

Results and benefits: pathways identified without pre-knowledge / prejudice by systems toxicology shall be modeled first in vitro to allow higher through-put screening without confounding parallel pathways; optimal conditions for model development by early alignment of needs, large and easily interpretable datasets.

-       The standardized datasets are used for modeling.

Results and benefits: optimal start conditions to model in silico relatively simple systems in order to reduce labor and costs of information generation.

-       Additional standardized data are produced for model validation. 

Results and benefits: independent external validation of models by a second dataset with the same quality.

-       The process will be monitored as a case study to develop a pathway-based toxicology and in vitro testing strategies for DNT. Opportunities for extension to other mechanisms of DNT, reproductive toxicology in general or other areas of toxicology shall be assessed in workshops and the DNT-4 conference planned for 2014.

Results and benefits: extension beyond the actual projects as a test case for the novel approach by accompanying analysis of process and limitations; maximum stakeholder and expert input for the test case.

-       A link to pertinent projects in Europe shall be maintained.

Results and benefits: synergy for developing new approaches; opening up for possible later evaluation / acceptance of new approaches.