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A Three-Dimensional Organoid Culture Model to Assess the Influence of Chemicals on Morphogenetic Fusion.
Belair, D., C. Wolf, S. Moorefield, C. Wood, C. Becker, AND B. Abbott. A Three-Dimensional Organoid Culture Model to Assess the Influence of Chemicals on Morphogenetic Fusion. TOXICOLOGICAL SCIENCES. Society of Toxicology, RESTON, VA, 166(2):394-408, (2018). https://doi.org/10.1093/toxsci/kfy207
Virtual Tissue Models are uniquely positioned to capture the connectivity between different scales of biological organization. The focus of the Morphogenetic Fusion Task is to develop a complex 3-D culture model to mimic embryonic fusion events required during development. Morphogenetic fusion is a complex process having contributions from multiple cell types and cell behaviors and is sensitive to chemical disruption. The spheroid model is being developed to evaluate responses to chemicals and perturbation in molecular initiating events or key events involved in fusion-related phenotypes (birth defects). This paper reports outcomes of experiments to evaluate of the spheroid model’s responsiveness to model chemicals and to selective disruptors of key events and signaling pathways in palatal fusion.
Organogenesis in the embryo involves cell differentiation and organization events that are unique to each tissue and organ and are susceptible to developmental toxicants. Animal models are the gold standard for identifying putative teratogens, but the limited throughput of developmental toxicological studies in animals coupled with the limited concordance between animal and human teratogenicity motivates a different approach. In vitro organoid models can mimic the cellular architecture and phenotype of many tissues and organs, and the three-dimensional (3D) architecture of organoids presents an opportunity to study developmental human toxicology. Common themes during development like the involvement of epithelial-mesenchymal transition and tissue fusion present an opportunity to develop in vitro models to study cell and tissue morphogenesis. We previously described organoids composed of human stem and progenitor cells that recapitulated the cellular features of palate fusion, and here we further characterized the model by examining pharmacological inhibitors targeting known palatogenesis and epithelial morphogenesis pathways as well as twelve cleft palate teratogens identified from rodent models. Organoid survival was dependent on signaling through EGF, IGF, HGF, and FGF pathways, and organoid fusion was disrupted by inhibition of BMP signaling. We observed concordance between the effects of EGF, FGF, and BMP inhibitors on organoid fusion and epithelial cell migration in vitro, suggesting that organoid fusion is dependent on epithelial morphogenesis. Three of the twelve putative cleft palate teratogens studied here significantly disrupted in vitro fusion, including theophylline, triamcinolone, and valproic acid. Tributyltin chloride and all-trans retinoic acid (ATRA) were cytotoxic to fusing organoids. The study herein demonstrates the utility of the in vitro fusion assay for identifying chemicals that disrupt human organoid survival and morphogenesis in a scalable format amenable to toxicology screening.