Engineering human cell spheroids to model embryonic tissue fusion in vitro
Authors
David G. Belair, Cynthia J. Wolf, Carmen Wood, Hongzu Ren, Rachel Grindstaff, William Padgett, Adam Swank, Denise MacMillan, Anna Fisher, Witold Winnik, Barbara D. Abbott
Institution
Toxicity Assessment Division, US EPA, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina, United States of America Research Cores
Country
United States
Year
2017
Journal
PLOS one
Abstract
Epithelial-mesenchymal interactions drive embryonic fusion events during development,
and perturbations of these interactions can result in birth defects. Cleft palate and neural
tube defects can result from genetic defects or environmental exposures during development,
yet very little is known about the effect of chemical exposures on fusion events during
human development because of a lack of relevant and robust human in vitro assays of
developmental fusion behavior. Given the etiology and prevalence of cleft palate and the relatively
simple architecture and composition of the embryonic palate, we sought to develop a
three-dimensional culture system that mimics the embryonic palate and could be used to
study fusion behavior in vitro using human cells. We engineered size-controlled human
Wharton's Jelly stromal cell (HWJSC) spheroids and established that 7 days of culture in
osteogenesis differentiation medium was sufficient to promote an osteogenic phenotype
consistent with embryonic palatal mesenchyme. HWJSC spheroids supported the attachment
of human epidermal keratinocyte progenitor cells (HPEKp) on the outer spheroid surface
likely through deposition of collagens I and IV, fibronectin, and laminin by
mesenchymal spheroids. HWJSC spheroids coated in HPEKp cells exhibited fusion behavior
in culture, as indicated by the removal of epithelial cells from the seams between spheroids,
that was dependent on epidermal growth factor signaling and fibroblast growth factor
signaling in agreement with palate fusion literature. The method described here may broadly
apply to the generation of three-dimensional epithelial-mesenchymal co-cultures to study
developmental fusion events in a format that is amenable to predictive toxicology
applications.
Introduction