Zebrafish Embryos and Larvae as Alternative Animal Models for Toxicity Testing

Abstract

Prerequisite to any biological laboratory assay employing living animals is consideration about its necessity, feasibility, ethics and the potential harm caused during an experiment. The imperative of these thoughts has led to the formulation of the 3R-principle, which today is a pivotal scientific standard of animal experimentation worldwide. The rising amount of laboratory investigations utilizing living animals throughout the last decades, either for regulatory concerns or for basic science, demands the development of alternative methods in accordance with 3R to help reduce experiments in mammals. This demand has resulted in investigation of additional vertebrate species displaying favourable biological properties. One prominent species among these is the zebrafish (Danio rerio), as these small laboratory ray-finned fish are well established in science today and feature outstanding biological characteristics. In this review, we highlight the advantages and general prerequisites of zebrafish embryos and larvae before free-feeding stages for toxicological testing, with a particular focus on cardio-, neuro, hepato- and nephrotoxicity. Furthermore, we discuss toxicokinetics, current advances in utilizing zebrafish for organ toxicity testing and highlight how advanced laboratory methods (such as automation, advanced imaging and genetic techniques) can refine future toxicological studies in this species.

Keywords: 3R; alternative methods; danio rerio; organ toxicity; transgenic animals.

Figure 1

Possible compound application routes for larval zebrafish. Uptake routes which predominate during exposure by immersion are indicated by arrows, sites for compound microinjection by injection needles.

Figure 2

Transgenic zebrafish reporter lines. (A) Lateral view of the trunk of a cdh17:mCherry larva (5 dpf), co-stained nuclei with Hoechst 33342. The mCherry fluorescence labels the kidney (arrowheads) and the intestine (diamond). (B) Snapshot of a gata1:DsRed larva (5 dpf) in lateral position. Hematopoietic cells are marked by red fluorescence throughout the whole body. (C) Ventral gfp/brightfield overlay image of the larval myl7:GFP heart (5 dpf), exhibiting green fluorescence in myocardial cells around the heart chambers (atrium and ventricle) and in the atrioventricular canal.