Literature review on in vitro and alternative Developmental Neurotoxicity (DNT) testing methods

Abstract

The goal of this systematic review performed under a contract with EFSA was the evaluation of information on assessment methods in the field of developmental neurotoxicity (DNT). Therefore, a systematic and comprehensive literature search and collection of scientific literature and all other relevant grey literature and website information (in English) from past 20 years until mid of April 2014 on the state of the art of in vivo DNT testing methods including novel and alternative non-mammalian models, in vitro test methods, in silico methods, read across and combination of testing methods in test batteries was performed. This systematic review identified a variety of methods covering early and later stages of neurodevelopment that have the ability to predict DNT of chemicals. Few in vivo models alternative to OECD TG 426 were identified. In general, the available published in vivo data is scattered and heterogeneous, making comparisons across exposure paradigms and compounds very difficult. Thus, to make more useful evaluations, publications with more consistent experimental designs are needed, and more focused in vivo-in vitro comparisons are needed to establish useful effect biomarkers and testing models. From the alternative methods, a testing strategy covering early and later neurodevelopmental stages (from stem cell to zebrafish larvae motor behaviour) can be assembled. For gaining regulatory acceptance, definition of biological application domains of alternative methods by performing e.g. in vitro -in vivo validation is needed. Moreover, protocols for cell-based and zebrafish assays need international standardization. With such standardized protocols, the test battery needs to be tested for its sensitivity and specificity by testing concentration-responses of known DNT positive and negative compounds across the different assays. Such data might then be used either for regulatory decision-making or compound prioritization in favour of a reduction of rodent guideline in vivo testing.

Scanning laser optical tomography resolves developmental neurotoxic effects on pioneer neurons

“…The pro-apoptotic alkaloid staurosporine is not an established DNT-positive compound, but has been listed as potential candidate in a systematic review on DNT testing methods 28 . Staurosporine acts mainly as a broad-spectrum protein kinase inhibitor 49 and will most likely interfere with many cellular processes.…”

“…Next, we generated a concentration-response curve (n = 226) for the pro-apoptotic compound staurosporine which has been listed as possible DNT positive compound 28 (Fig. 4B).…”

Assessment of developmental neurotoxicity induced by chemical mixtures using an adverse outcome pathway concept

“…The battery of the in vitro assays was applied to hiPSCderived neural stem cells (NSCs) differentiated into a mixed culture of neurons and astrocytes, since this model recapitulates, most of the key processes critical and specific for human brain development including neural progenitor cell commitment, proliferation, migration, neuronal and glial differentiation, synaptogenesis, and neuronal network formation and function [33][34][35]. The readiness of these in vitro methods for regulatory purposes has been recently evaluated based on 13 established semi-quantitative criteria [36].…”

OECD/EFSA workshop on developmental neurotoxicity (DNT): The use of non-animal test methods for regulatory purposes

“…Do we currently have assays that are ready for chemical screening?" The consensus, based on published literature, the EFSA DNT review (Fritsche et al, 2015) and OECD report (Fritsche, 2016), and data presented by the speakers, indicated that the response to this question depends on the problem formulation. Thus, the answer was "yes" for screening and prioritization, since we have already reached a high level of confidence in a number of process-control based assays (Fig.…”