In vitro developmental neurotoxicity
Speaker: Dr. Ellen Hessel, scientific researcher developmental neurotoxicology

DR. ELLEN HESSEL: We are developing a model based on human embryonic stem cells and the model mimics a part of the brain development. The model is used to test the safety of compounds.

VISUAL: In vitro developmental neurotoxicity

VOICE OVER: Disruption of brain development may have enormous impact on future life and might result in disorders such as ADHD or mental retardation. It is known that genetic factors contribute to these disorders, but environmental factors, such as exposure to compounds, may also play a role.

DR. ELLEN HESSEL: The effect of compounds on the developing brain is largely unknown. Therefore, there is a high need for testing adverse effects on the brain development of compound exposure.

VOICE OVER: A testing strategy with in vitro and in silico methods based on the biology of human brain development will help to unravel the adverse effects of compounds on the developing brain.

DR. ELLEN HESSEL: RIVM is developing an in vitro method that mimics parts of the brain development. This model is based on human stem cells. Human embryonic stem cells and induced pluripotent stem cells from blood can be used. As a first step, these stem cells are differentiated into neural progenitor cells. These neural progenitor cells can be frozen or re-cultured and differentiated in a neuron-astrocyte network, within 10 days. This is a relatively short and robust protocol.

VOICE OVER: With this differentiation method the model can develop a functional neuronal network.

DR. ELLEN HESSEL: Characterisation of the model with gene and protein expression show that we have neurons and astrocytes within the model and the ratio of these cells differ during the 10-day differentiation period. After 3 days, we even have spontaneous electrical activity within the model. With this model we show that compounds affect neuronal differentiation and this is in line with in vivo data. This model can be an important component in a testing strategy for developmental neurotoxicity and to measure the effect of chemicals and pharmaceuticals on the developing brain. This method is human-relevant and animal-free and is based on mechanistic knowledge of human biology of brain development.

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Cells4Thought research in the context of making human-relevant, animal-free models for neurodevelopmental health.

VICTORIA DE LEEUW, neurotoxicologist: We want to make human-relevant...

ELLEN HESSEL, neuroscientist: ...animal-free models...

MARTIJN DOLLÉ, molecular biologist: ...for neurodevelopmental health.

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On-screen text: Cells4Thought.

ELLEN: The prevalence of neurodevelopmental disorders is increasing worldwide, including cognitive impairments. There's evidence that exposure to chemicals may contribute to this increased prevalence of neurodevelopmental disorders. But there is very little causal evidence for this. This is because human brain development is extremely complex. And the models that are used to test this link, which are mostly animal studies, do not translate very well to humans. That's why we need to research the effect of chemicals in more human relevant models.

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VICTORIA: We're going to use induced pluripotent stem cells that we will differentiate into neuronal cells. Upon differentiation these cells will make connections with each other, which is a crucial cell process for normal brain development and cognition. We're not going to use any type of stem cell, but cells of which we know the history and genetic makeup. These cells will be derived from blood samples of healthy participants of the Doetinchem cohort after they've given informed consent. We will also induce gene mutations in these cells of which we know that they are important for normal cognition, using CRISPR-Cas technology. We will select these genes together with clinicians from the Amsterdam UMC. We will expose these cells to chemicals while they are differentiating into brain cells. The assumption is that when the differentiation of these cells is affected, that the chemical is potentially toxic. And moreover, it allows us to look at the underlying mechanisms.

MARTIJN: First we have to make the stem cells. Blood cells from consenting Doetinchem cohort participants will be reprogramed by the specialized iPS facility at the Erasmus Medical Center. This will lead to a stem cell resource that will be kept at the RIVM. We will differentiate these stem cells to functional neurons and expose them to harmful compounds at the same time. By exposing these differentiating cells from different people with and without disabled genes for normal cognitive function, we intend to gain insights on how genetic backgrounds and specific mutations affect the susceptibility of brain cells to chemical compounds. If our approach is successful for the brain, the stem cell resource
created in this project can be used to generate other tissues and study the effect of exposures in combination with genetic variation on human health, using human-relevant and animal-free models.

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On-screen text: Cells4Thought. Human cell models for healhty brains. National Institute for Public Health and the Environment, ministry of Health, Welfare and Sport, Amsterdam UMC, Erasmus MC.