Testing the Translational Power of the Zebrafish: An Interspecies Analysis of Responses to Cardiovascular Drugs

The zebrafish is rapidly emerging as a promising alternative in vivo model for the detection of drug-induced cardiovascular effects. Despite its increasing popularity, the ability of this model to inform the drug development process is often limited by the uncertainties around the quantitative relevance of zebrafish responses compared with nonclinical mammalian species and ultimately humans. In this test of concept study, we provide a comparative quantitative analysis of the in vivo cardiovascular responses of zebrafish, rat, dog, and human to three model compounds (propranolol, losartan, and captopril), which act as modulators of two key systems (beta-adrenergic and renin–angiotensin systems) involved in the regulation of cardiovascular functions. We used in vivo imaging techniques to generate novel experimental data of drug-mediated cardiovascular effects in zebrafish larvae. These data were combined with a database of interspecies mammalian responses (i.e., heart rate, blood flow, vessel diameter, and stroke volume) extracted from the literature to perform a meta-analysis of effect size and direction across multiple species. In spite of the high heterogeneity of study design parameters, our analysis highlighted that zebrafish and human responses were largely comparable in >80% of drug/endpoint combinations. However, it also revealed a high intraspecies variability, which, in some cases, prevented a conclusive interpretation of the drug-induced effect. Despite the shortcomings of our study, the meta-analysis approach, combined with a suitable data visualization strategy, enabled us to observe patterns of response that would likely remain undetected with more traditional methods of qualitative comparative analysis. We propose that expanding this approach to larger datasets encompassing multiple drugs and modes of action would enable a rigorous and systematic assessment of the applicability domain of the zebrafish from both a mechanistic and phenotypic standpoint. This will increase the confidence in its application for the early detection of adverse drug reactions in any major organ system.



A considerable number of drug candidates have the potential to alter cardiovascular functions at therapeutically relevant concentrations. Predicting those effects as early as possible during drug development is critically important to ensure the progression of safer compounds through the pipeline and to minimize the risk of cardiovascular safety liabilities emerging at later stages of development (Laverty et al., 2011Cook et al., 2014Lester and Olbertz, 2016). The fast-paced advancements ongoing in the development of human-based in silico and in vitro predictive approaches hold great promise for improving the early detection of drug-induced cardiovascular alterations, including cardiotoxicity (Clements et al., 2015Colatsky et al., 2016Gintant et al., 2016Land et al., 2017Passini et al., 2017). However, to date, the use of in vivo preclinical models is still a key aspect of cardiovascular efficacy and safety assessment (Fliegner et al., 2015Vargas et al., 2015Berridge et al., 2016), mainly because of the ability of in vivo testing to capture integrated multiscale processes that cannot be observed outside an intact organism. These processes include pharmacokinetic-dependent and metabolism-mediated effects, chronic or delayed toxicity, vascular and hemodynamic alterations, as well as interaction between cardiovascular, nervous, and renal systems (Holzgrefe et al., 2014).

In this context, the identification of the most suitable preclinical animal model represents a central challenge for the design of a successful testing strategy, as this choice can profoundly affect the translational value of each experiment and, in turn, data interpretation and subsequent decision-making (Denayer et al., 2014Holzgrefe et al., 2014). From a cardiovascular perspective, dog and nonhuman primates (e.g., cynomolgus monkey) are the most commonly used nonrodent models, as their physiology is considered the most relevant to humans (Leishman et al., 2012Holzgrefe et al., 2014). Other test species include minipig (Bode et al., 2010), marmoset (Tabo et al., 2008), and guinea pigs (Marks et al., 2012). Beside these models, small rodent species (i.e., rat and mouse) remain the most popular choice to investigate cardiovascular physiology and disease, genetics, and pharmacology (Camacho et al., 2016). As with any animal model, each species mentioned above has both advantages and limitations (e.g., see Holzgrefe et al. (2014) and Milani-Nejad and Janssen (2014) for extensive reviews of these aspects); however, common limitations include high ethical and financial costs, and low throughput potential.

In recent years, extensive research efforts have been allocated worldwide to identify potential alternative testing approaches that may lead to the reduction, replacement, or refinement (3Rs) of the model species mentioned above. Within this research theme, the zebrafish has emerged as a new, potentially valuable, model for the in vivo assessment of a variety of human-relevant drug-induced effects, including cardiovascular alterations (Parker et al., 2014MacRae and Peterson, 2015). Zebrafish are characterized by a number of valuable features, including relatively inexpensive maintenance costs, amenability to genetic manipulation, high conservation of human drug targets (i.e., >82%; Howe et al., 2013Verbruggen et al., 2017), and of a broad range of human-relevant phenotypes that can be modified by pharmacological treatment (MacRae and Peterson, 2015).

Considering the high impact of unpredicted cardiotoxicity on drug development (Laverty et al., 2011), the availability of a simpler vertebrate model, such as zebrafish, may enable cardiovascular profiling of new drugs before commencing mammalian toxicity tests, thus serving as a bridge between early in vitro safety predictions and later in vivo preclinical testing. Several studies have started to explore this potential from a translational perspective, such as Parker et al. (2014)and Cornet et al. (2017). Despite encouraging results, to date, the implementation of zebrafish in existing testing strategies faces resistance not least because of uncertainty around the quantitative aspects of zebrafish cardiovascular responses compared with both mammalian preclinical species and humans. We propose that coordinated efforts to perform quantitative comparative assessment of those responses may help to clarify the translational value of zebrafish and help define its domain of applicability from both mechanistic and phenotypic standpoints.

The aim of the present study was to quantify the degree of similarity in the in vivo cardiovascular responses of zebrafish, rat, dog, and human to three model compounds (propranolol, losartan, and captopril), which act as modulators of two key systems (beta-adrenergic and renin–angiotensin systems) involved in the regulation of cardiovascular functions. To do so, we used in vivo imaging techniques to generate novel zebrafish experimental data. The latter were successively combined with a database of interspecies responses extracted from the literature to perform a meta-analysis of effect size and direction across species (Figure 1).


Link to the publication : https://www.frontiersin.org/articles/10.3389/fphar.2019.00893/full