Advancing the 3Rs: Refining and Complementing Animal Models in Molecular Neuroscience

Animal models remain central to neuroscience research, providing insights into brain function, disease mechanisms, neurotoxicology, and therapeutic development that cannot yet be fully replicated by other approaches. At the same time, advances in experimental and computational methods are creating new opportunities to refine animal studies, reduce the number of animals required, and, where scientifically appropriate, replace specific uses of animals altogether. The principles of Replacement, Reduction, and Refinement (the 3Rs) therefore provide not only an ethical framework for neuroscience research, but also an opportunity to improve experimental design, mechanistic resolution, and translational relevance.Rapid advances in human-derived in vitro systems, brain organoids, microphysiological platforms, computational modeling, and artificial intelligence are expanding the range of questions that can be addressed without exclusively reliance on animal models. These approaches can improve mechanistic studies, facilitate compound screening, identify promising targets before in vivo testing, and help prioritize experimental conditions. An important challenge for the next generation of non-animal neuroscience models will be increasing their biological complexity and translational value. For example, many conventional neural cell culture and brain organoid systems lack vascularization and do not reproduce interactions between neural cells and the cerebral vasculature, among other shortcomings. Incorporating multiple human-derived cell types, blood–brain barrier properties, perfusion, and other components of the neurovascular unit may substantially improve the physiological and translational relevance of these models.At the same time, the suitability of an alternative approach depends on the biological question being asked. Complex behaviors, circuit-level interactions, systemic physiology, neuroendocrine and immune interactions, and long-term developmental processes often require the integration provided by an intact organism. Conversely, questions involving defined cellular mechanisms, molecular pathways, or early-stage compound screening may increasingly be addressed using human-derived cells, organoids, microphysiological systems, or computational approaches. Advancing the 3Rs therefore requires selection of the appropriate model for the scientific question rather than reliance on any single experimental approach to universally replace another.This Research Topic welcomes contributions that advance the 3Rs through refinement of animal models, reduction in animal use, development and validation of non-animal approaches, or integration of complementary experimental systems. Contributions should address how new methods can improve scientific rigor and translational value while reducing animal use or burden, and we particularly encourage authors to consider the strengths and limitations of the models they employ. Of particular interest are studies that identify where animal models remain necessary, where alternative approaches can provide equivalent or superior information, and how computational, in vitro, ex vivo, and in vivo methods can be combined within an efficient and scientifically rigorous research pipeline. Sub-themes welcomed include, but are not limited to:• Advances in brain organoids, microphysiological systems, human-derived cell models, and other approaches for investigating neural development, function, disease, and toxicity.• Development of more physiologically complete in vitro models, including incorporation of vascular and neurovascular-unit components, immune cells, extracellular matrix, fluid flow, and inter-organ interactions where these features are necessary for biological or translational validity.• Refinement strategies that improve animal welfare while simultaneously improving data quality, including non-invasive or minimally invasive monitoring, longitudinal study designs, improved behavioral methods, imaging approaches, and optimized experimental design.• Reduction strategies that increase the information obtained from individual animals or experiments, including multimodal endpoints, longitudinal measurements, advanced statistical design, data sharing, and computational integration.• Domains in which intact animal models remain necessary and the scientific rationale for their continued use.• Hybrid research pipelines that integrate computational, in vitro, ex vivo, and in vivo approaches to maximize mechanistic and translational information while minimizing animal use.• Validation and benchmarking studies that compare alternative models with established animal models and, where possible, human biological or clinical data.• Studies defining the limitations, boundaries of applicability, and sources of uncertainty associated with emerging replacement and complementary models.• AI and machine-learning approaches for predicting neurotoxicity, behavior, disease mechanisms, or therapeutic responses and for prioritizing experiments before in vivo testing. Topic editors: Yijie Geng, Freyja Olafsdottir, Lisa Genzel, Hector Rosas-Hernandez Source: https://www.frontiersin.org/research-topics/85907/advancing-the-3rs-refining-and-complementing-animal-models-in-molecular-neuroscience