Grantee Research Project Results
Final Report: Human Stem Cell-Based Platform to Predict Selective Developmental Neurotoxicity
EPA Grant Number: R835552Title: Human Stem Cell-Based Platform to Predict Selective Developmental Neurotoxicity
Investigators: Terskikh, Alexey V.
Institution: Sanford-Burnham Medical Research Institute
EPA Project Officer: Aja, Hayley
Project Period: September 1, 2013 through August 31, 2017
Project Amount: $800,000
RFA: Development and Use of Adverse Outcome Pathways that Predict Adverse Developmental Neurotoxicity (2012) RFA Text | Recipients Lists
Research Category: Chemical Safety for Sustainability , Human Health
Objective:
The objective of this research project was to develop and implement a novel screening approach to assay developmental neurotoxicity using a human embryonic stem cell (hESC)-based model of neuronal development. We postulated that toxicants that exert selective neurodevelopmental cytotoxicity are particularly difficult to identify using conventional toxicological approaches. However, such chemicals will be of high concern since they are capable of disrupting the balance of neural development and may result in early onset of locomotion deficits such as Parkinson’s as well as neurological abnormalities associated with mesolimbic dopaminergic pathways such as altered motivation, emotion, and addiction responses. We proposed to identify such compounds by screening ToxCast e1k library (1860 unique compounds). We have included human fetal neural precursor cells (hfNPCs) to account for the potential cytotoxicity to primary human neural progenitors. We have used human ESC-derived ventral neural precursor cells (vNPCs) and human ESC-derived dorsal neural precursor cells (dNPCs).
Summary/Accomplishments (Outputs/Outcomes):
We have achieved the major and the principle goal of the proposed studies by clearly demonstrating the existence of compounds, which have selective cytotoxic effect on one type of regionally specified neural progenitors and thus has a potential to affect neurodevelopment in a subtler ways then overtly toxic compounds, which conventionally result in gross abnormalities of neurodevelopment often resulting in embryonic lethality due to the major aberrations in neural development. The selective cytotoxic compounds identified in our screening of 1860 e1k unique compounds revealed two compounds with known broad spectrum of developmental abnormalities in mouse models (8, 9) thus further validating our finding with human neural progenitors. On the other hand, we have identified three experimental compounds that were not advanced to clinic, thus demonstrating the validity of our approach for screening novel candidate drugs for specific effects on some but not other neurodevelopmental processes. Based on our findings it will be important to conduct the screening of a larger libraries of environmental toxicants such as >8,000 compounds from Tox21 chemical library.
The identification of compounds in e1k library that selectively and potently effect ventral neural progenitors has significant implications for future testing of environmental chemicals, and, especially, drugs used in clinical practice. Indeed, reduction of ventral neural progenitors could induce significant changes in the developing ventral midbrain, which give rise to Th+ dopaminergic neurons in substantia nigra (SN) and ventral tegmental area (VTA). The nigrostriatal pathway associated with the activity of dopaminergic neurons in SN is responsible for locomotion and the deficit of dopaminergic neurons in this area represent on of hallmarks of Parkinson’s. On the other hand, the mesolimbic dopaminergic system originating from the VTA innervates, among other structures, the nucleus accumbens and amygdala, which are known to be involved in motivation, emotion, reward, addiction, and intense feeling of love (10, 11). The relationship between the ventral neural progenitors, midbrain dopaminergic neurons, and main dopaminergic pathways are depicted in Figure 4 (modified from (12)). Because dopaminergic neurons in both VTA and SNc originating from the same progenitor pool (vNPCs) it becomes apparent that any deficit of vNPCs will generate subsequent deficits in both nigro-striatal and mesolimbic dopaminergic pathways.
Conclusions:
Our observations of selective neurodevelopmental effects of several e1k compounds on ventral neural progenitors implies that these compounds might elicit deficits of nigrostriatal and mesolimbic pathways if encountered during fetal brain development. Therefore, it will be important to conduct the in vivo studies (which are outside of the scope of current work) with these compounds to determine whether they indeed elicit developmental changes in ventral midbrain in vivo. Subsequent stereological counting of adult DA neurons in the affected SN and VTA will address the possibility that in utero exposure to environmental toxicants might elicit a broader neurodegenerative and behavioral phenotype than previously anticipated.
Supplemental Keywords:
ESC, embryonic stem cells, NPC, neural progenitor cells, GFAP, glial fibrillary acidic protein, SNc, substanita nigra, VTA, ventral tegmental area, DMSO, dimethyl sulfoxideProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.