Katharina Koch

Katharina Koch is a co-founder and shareholder of the company DNTOX offering DNT assay services and chemical testing for the chemical, cosmetic and pharmaceutical industry. Furthermore, she is the commissarial head of the working group "Alternative method development for environmental toxicity testing" at the IUF - Leibniz Research Institute for Environmental Medicine in Duesseldorf, Germany. Her research focuses on the development of test methods for developmental neurotoxicity (DNT), endocrine disruption (ED)-mediated DNT and acute neurotoxicity. She has extensive expertise in the development and scientific validation of alternative in vitro test methods using primary fetal neural progenitor cells (NPCs) and induced pluripotent stem cell-derived iNPCs and the study of hormonal dependencies of key neurodevelopmental processes (KNDPs).

NextGen Basel 1

Elucidation of hormonal dependencies and associated species specificities of key neurodevelopmental processes to improve EDC risk assessment

Katharina Koch 1, 2, Kevin Schlüppmann 1, Louisa Merit Stark 1, Saskia Hüsken 1, Stefan Masjosthusmann 1, Jördis Klose 1,2, Arif Dönmez 1,2, Nils Förster 3,4, Ellen Fritsche 1,2,5

1 - Leibniz Research Institute for Environmental Medicine (IUF), Düsseldorf, Germany

2 - DNTOX GmbH, Düsseldorf, Germany

3 - Bioinformatics Group, Department of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany

4 - Bioinformatics, Center for Protein Diagnostics (ProDi), Ruhr-University Bochum, Bochum, Germany

5 - SCAHT, Basel, Switzerland

Background: Endocrine disrupting chemicals (EDCs) have been intensively studied regarding their harmful effects on human brain development. Despite increasing evidence that developmental EDC exposure causes developmental neurotoxicity (DNT), systematic endocrine disruption (ED)-mediated DNT testing is lacking in EDC risk assessment. The identification of chemicals causing adverse neurodevelopmental effects is solely based on rodent in vivo studies. However, it is questionable to which extent the species influences the sensitivity of key neurodevelopmental processes (KNDPs) to exogenous noxae, both for endocrine and non-endocrine modes-of-action. Therefore, DNT in vitro test systems have been established that enable species comparisons, including a multiplexed high-content assay based on neural progenitor cells (NPCs), the Neurosphere Assay. Here, the human Neurosphere Assay was used to identify hormone-sensitive neurodevelopmental key events and establish ED-DNT in vitro assays that meet the regulatory requirements for screening putative EDCs

Methods: To identify hormone-sensitive KNDPs that represent putative targets of EDCs, we examined the effects of 14 hormone receptors (HRs) on the eight KNDPs modeled in the Neurosphere Assay using fetal human NPCs (hNPC). In addition, causal relationships between hormone receptor activation and correlated DNT phenotypes were investigated using RNA sequencing analyses. Species specificities were investigated by challenging time-matched rat NPCs (rNPCs) with the same HR modulators.

Results: KNDPs like NPC proliferation, radial glia migration, and terminal differentiation into neurons and oligodendrocytes were affected by HR activation at physiological relevant hormone concentrations in the nanomolar range. Activation of the liver X receptor (LXR) and peroxisome proliferator-activated receptors (PPARs) α and β/δ impaired oligodendrocyte differentiation, which we could further correlate to deregulation of developmental pathways (e.g. Wnt and MAPK/ERK) and disruption of lipid homeostasis. Activation of the retinoic acid receptor (RAR) and glucocorticoid receptor (GR) impaired hNPC proliferation, which was linked to deregulation of cell cycle progression and DNA/RNA transcription. Of note, the GR-dependent NPC proliferation arrest was controlled in a sex-specific way with male NPCs being more sensitive. Finally, neuronal differentiation was enhanced by thyroid hormone receptor (THR) and retinoid X receptor (RXR) activation, which we could correlate to transcriptional Notch pathway suppression. Strikingly, multiple phenotypes observed in hNPCs could not be recapitulated in rat NPCs, illustrating how species-specifically neurodevelopment is regulated by hormones and questioning the predictivity of in vivo rodent studies for EDC risk assessment.

Conclusion: Since HR-regulated KNDPs represent targets for endocrine disruption, ED-DNT in vitro assays are currently being established and screened using libraries of known and putative EDCs. Given the severe implications associated with DNT, testing putative EDCs for their developmental neurotoxic potential is of paramount importance to various stakeholders, including regulatory agencies, industry, and the general public.