Cocultured DPSC and HSG cells: a Model for Epithelial-mesenchymal Communication

Objectives: Differentiation of tooth germ involves epithelial-mesenchymal interactions. We aimed to model these interactions using cultures of mesenchymal cells isolated from adult human dental pulp and undifferentiated epithelial cells from salivary origin. Methods: Primary dental pulp stem cell culture (DPSC) was prepared from human impacted third molars. HSG, an undifferentiated human salivary gland ductal cell line, capable of transdifferentiating into salivary acini, was used as an epithelial source for culture. DPSC and HSG cells were cocultured on glass slides. In separate experiments DPSC and HSG cells were cultured on the extracellular matrix derivative Matrigel. Results: DPSC grew as elongated fibroblast-like cells on glass slides. HSG cells on glass slide grew as a monolayer with cobblestone appearance. When HSG and DPSC cells were cocultured (40-40 K cells plated onto the two sides of a coverslip) the normal growth and shape of HSG cells remained undisturbed. However, DPSCs migrated toward the HSG cells, some of them reaching to the top of HSG clusters, and changed in morphology characterized by long extensions of cytoplasm and smaller, rounded soma. Matrigel induced HSG cell differentiation into acinar-like structures in the first two days, and resulted in apoptosis of the epithelial cells in 5 days. When DPSCs were cultured on Matrigel the cells rapidly underwent growth arrest and eventually died. Conclusions: Coculture of DPSC and HSG cells results in dramatic changes of cell shape and migrating activity of DPSCs, while no obvious morphological change can be observed in HSG cells. The extracellular matrix derivative Matrigel induces rather different effects, selectively promoting the differentiation of the epithelial HSG cells, but not the mesenchymal DPSCs. Further studies are needed to identify the factors transmitting the above described differentiation signals for DPSC and HSG cells. This work was supported by OTKA -61543, ETT 350/2003 and OM Postdoctoral Grant (18657/2005).