Citation:

Abbott, B., D. Belair, Cynthiaj Wolf, K. Das, C. Wood, C. Becker, AND S. Moorefield. An Engineered Organoid Culture Model That Incorporates Human Mesenchymal and Epithelial Cells to Model Palatal Fusion. Teratology Society Annual Meeting, Clearwater, Florida, June 23 - 28, 2018.

Impact/Purpose:

This abstract is for an invited presentation at the Symposium "Organotypic culture Models and Microphysiological systems for human development: New platforms for mechanistic evaluation of developmental toxicity”. This research is a Task in the CSS Program Virtual Tissues Project and represents the development of a complex culture model of tissue fusion, an important developmental event in formation of tissues and organs. Complex models using human cells in an integrated, morphologically relevant context provide medium through-put models that bridge between high throughput systems (such as those in ToxCast) that use simple, cell-free or cellular assays and expensive, low-through-put animal testing.

Description:

During embryonic development, fusion events are critical to morphogenesis of organs and tissues, including the iris, urethra, heart, neural tube, and secondary palate. Modeling this process in vitro is challenging as the interactions of mesenchymal and epithelial cells can be critical to successful completion of the fusion process. In vitro models to mimic human development ideally would use human cells in appropriate states of differentiation and gene expression which incorporate key signaling pathways necessary for development of the tissue being modeled. In this project, we use human cells to develop a complex, three-dimensional culture system to model palatal fusion. Spherical organoids were engineered from human Wharton’s jelly stem cells (HWJSCs) and human neonatal primary epidermal keratinocyte progenitor cells (HPEKp). The organoids consist of a sphere of HWJSC with HPEKp cells on the surface. The HWJSC core was induced to differentiate toward an osteogenic phenotype and expressed genes associated with extracellular matrix production, angiogenesis, cell adhesion, and skeletal system. Fusion was evaluated by placing organoids in contact and monitoring the change in presence of epithelial cells in the contact zone (i.e. elimination of an epithelial barrier between organoids, similar to removal of medial cells at palatal fusion). At completion of fusion, epithelial cells remained only on the surface of the merged organoids. Inhibition of critical morphogenetic signaling with pharmacological inhibitors demonstrated that the bone morphogenetic protein (BMP), epidermal growth factor (EGF), fibroblast growth factor (FGF), hepatocyte growth factor (HGF), and insulin-like growth factor (IGF) pathways were critical for fusion and survival of the organoids. Also, exogenous EGF in the medium promoted proliferation of the epithelial cells and disrupted fusion. Teratogens were selected for testing in the organoid fusion model based on induction of cleft palate in rodent models. After 4 days of exposure during the fusion stage of culture, valproic acid and triamcinolone showed a dose-dependent interference with fusion of the organoids, whereas tretinoin and tributyltin chloride affected both fusion and survival. This engineered complex culture model demonstrates the potential for using human cells to mimic cellular and molecular events of palatal fusion.

Record Details: