Grantee Research Project Results
2021 Progress Report: Skeletal Teratogenicity of Industrial and Environmental Chemicals Predicted with Human Pluripotent Stem Cells in Vitro
EPA Grant Number: R839502Title: Skeletal Teratogenicity of Industrial and Environmental Chemicals Predicted with Human Pluripotent Stem Cells in Vitro
Investigators: zur Nieden, Nicole I , Volz, David C.
Institution: University of California - Riverside
EPA Project Officer: Callan, Richard
Project Period: August 1, 2019 through July 31, 2022 (Extended to July 31, 2025)
Project Period Covered by this Report: August 1, 2020 through July 31,2021
Project Amount: $849,811
RFA: Advancing Actionable Alternatives to Vertebrate Animal Testing for Chemical Safety Assessment (2018) RFA Text | Recipients Lists
Research Category: Chemical Safety for Sustainability
Objective:
We hypothesize that cultures of human embryonic stem cells (hESCs) can be utilized to predict the skeletal embryotoxicity of industrial and environmental chemicals in vitro. The objectives of this study are to differentiate hESCs into bone-forming osteoblasts with concomitant chemical exposure (the test bank includes selected chemicals from the ToxCast I library with known effects on the skeleton). Detrimental effects of the chemical are evaluated based on a reduction in matrix mineralization (as a surrogate of skeletal maturation). To identify suitable assays for matrix mineralization that adequately predict human risk, we compare inexpensive absorbance-based assays and image analysis tools recently developed by us. Hierarchies of chemical potency and efficacy will be established by setting the half-maximal inhibitory doses of differentiation inhibition in relation to the half-maximal cytotoxic dose using a biostatistical model, canonical linear discriminants and integration of our new data into EPA’s Toxicology Priority Index to create a skeletal embryotoxicity score. A case study will determine whether the scoring system is sufficiently sensitive to distinguish between closely related chemical derivatives and will consequently establish whether the assay can be used to identify safer chemical alternatives. Lastly, testing the chemicals with differentiation protocols that generate only neural crest or mesodermal osteoblasts coupled with next-generation sequencing will identify potential modes-of-action (disruption of organogenesis) and mechanisms of toxicity (molecular-level initiating event).
Progress Summary:
In order to develop a predictive in vitro assay, we have selected chemicals from the ToxCastI library with known effects on the skeleton associated with embryonic exposure. From this list, we have so far tested 13 chemicals with human cells and 11 with mouse cells. In addition, we have obtained concentration response curves for four reference chemicals that exhibit either strong embryotoxicity or none. All chemicals tested so far have been evaluated with an existing biostatistical prediction model found to only partially predict embryotoxicity classes according to the chemical’s known in vivo effects. This was an expected result and lends evidence to the hypothesis that a different prediction model needs to be created, as is the objective of this proposal. The results to date put as well on the trajectory towards achieving our objectives as proposed.
Future Activities:
Finalizing the chemicals screen for the training set in cell types of both mouse and human will help establish the predictivity of our in vitro assay for human risk associated with exposure and the development of a new biostatistical prediction model, specifically geared toward risk for skeletal malformations. Testing chemicals from a test set will then determine the validity of the established statistical models. Similarly, once we regain access to equipment on our campus, currently non-usable due to COVID-19 prevention measures, we will evaluate alternative, less expensive endpoints.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 6 publications | 3 publications in selected types | All 3 journal articles |
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Walker LM, Sparks NR, Puig-Sanvicens V, Rodrigues B, Zur Nieden NI. An evaluation of human induced pluripotent stem cells to test for cardiac developmental toxicity. International Journal of Molecular Sciences 2021;22(15):8114. |
R839502 (2021) |
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Supplemental Keywords:
exposure, risk assessment, sensitive populations, dose-response, teratogen, develop-mental toxicity, pluripotent stem cells, adverse outcome pathway, imaging, chemical derivativesProgress 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.