Session 12 OpenTox Virtual Conference 2021
Session Title & Summary: Towards Zebrafish Toxicity Assays Harmonization and Validation for Risk Assessment, Ongoing and Future Perspectives.
The utility of zebrafish for toxicity testing is expanding across the globe with hopes that this model species can serve as a chemical screening tool, predict adverse health outcomes, or even replace rodent models used for risk assessment. However, challenges exist which hinder the broader adoption of the zebrafish model in toxicology. These obstacles include the lack of harmonized experimental approaches in embryonic and adult fish, incomplete knowledge regarding chemical absorption, distribution, metabolism, and excretion, and also inconsistent informatics approaches used to classify adverse outcomes. Without harmonization in these key areas, integrating and comparing data across laboratories is problematic for organizations hoping to use this model for safety or toxicity assessments and causes doubts about their use as a reliable model for human health. This session will explain different efforts going on worldwide among the zebrafish community to harmonized and validate different zebrafish toxicity assays.
The first speaker will talk about the National Toxicology Program’s approach to refine and harmonize zebrafish screening protocols for chemical safety assessment, highlighting the importance of anthologies harmonization in the zebrafish, especially for developmental toxicity assessment. The second speaker will focus on the advantages of using software that allows the unbiased assessment based on image analysis for phenotypic screening in zebrafish assay. Finally, the last speaker will talk about the complexity of harmonization and validation of protocols, and the efforts of the inter-laboratory case study to determine the added value of the Zebrafish Light-dark transition test to predict developmental neurotoxicity.
Talk Title: Harmonization and Validation of zebrafish Light-dark transition test to predict Developmental Neurotoxicity for the OECD test guidelines for DNT (TG 426 and 443).
Abstract: The development of the Central Nervous System (CNS) is a complex process involving many different events that are activated in exact time frames and each event might show a different window of vulnerability to chemical exposure. Therefore, Developmental Neurotoxicity (DNT) entails one of the most complex areas in toxicology. There is an increasing number of chemicals in our food, drinking water, air, and soil and some chemicals are becoming worldwide pollutants so it is important to perform comprehensive toxicological profiling of newly manufactured chemicals. There is an unmet need for human-relevant, fast, sensitive, and cheap in vivo models to assess DNT potential of chemicals. Zebrafish is a suitable model for this purpose. The advantages of the zebrafish include their low cost and ease of maintenance and breeding. They have external fertilization and can produce hundreds of offspring weekly. Moreover, its small size allows zebrafish to be plated in standard microplates, they can be handled easily and compound exposure is usually carried out by immersion of fish directly into the media. Importantly, the results of the zebrafish screens show a good correlation to mammalian models of toxicology and support the utility of the zebrafish model in toxicology research . The neurological system, the different neuron types, and neurotransmitters are well studied and well conserved among zebrafish and other species, including humans. In zebrafish, whole-brain development occurs within a relatively short period: by 2–3 dpf, many different neurotransmitter-expressing neurons (GABAergic, glutamatergic, monoaminergic, cholinergic, and peptidergic) can be identified and glial subtypes (oligodendrocytes, Schwann cells, and astrocytes) are detected at 4 dpf . Up until 120 hours post-fertilization (hpf), zebrafish are not considered experimental animals under the current European animal directive (2010/63/EU) thus, working with this model supports ‘3R’ principles. Zebrafish show spontaneous swimming behavior from 3 days post fertilization (dpf) onwards what allows assessment of locomotor activity. Moreover, embryo tracking systems enable ease and automated analysis of locomotor activity under different conditions. Therefore, assessment of the locomotor activity of zebrafish could be a relevant and cost/time-effective method for DNT screening.
However, different treatment regimens or different conditions for behavior assessment may provoke to achieve different results. To obtain widespread accepted outcomes harmonization of the protocol is essential. This harmonized protocol should involve the exposure process, readout conditions, acceptance criteria and analysis, and interpretation of results. This harmonization effort is the principal aim of the DNT-OECD interlaboratory project where Biobide is taking part, in standardizing and validating the assay, to be included in the OECD test guidelines for DNT (TG 426 and 443) are only occasionally carried out and the predictivity of these in vivo animal tests for human health effects may be limited. There is a high need for human-relevant in vitro models to assess the DNT potential of chemicals. OECD is, therefore, building a guidance document containing a testing strategy to predict DNT. This testing strategy consists of a combination of in vitro tests encompassing the critical processes in brain development. This study aims to investigate the added value of the zebrafish DNT behavioral model in this testing strategy.
CV: MSc in Pharmacy and Master's degree in R+D+i of New Drugs at the Navarra University (Pamplona, Spain), with doctorate course in Design, Synthesis, and Evaluation of New drugs, in Pharmaceutical and Organic Chemistry. In addition, she has an MBA from the San Pablo CEU University of Madrid (Spain), where she improved her management and business development skills.
She began working in CRO´s 18 years ago, first in the field of Clinical Trials, and later in 2006, she moved to the Pre-Clinical field starting to work in Biobide, after a training period working with zebrafish in the Salk Institute of California. During those years she had different positions in Biobide, from Quality, Safety, and Environment Director, to I.P. and Business Development Director, leading to generate a deep understanding of the zebrafish services developed in the field.