Epithelial-mesenchymal signaling interactions induce differentiation of dental lineage cells

Objective: Teeth form through reciprocal signaling interactions between epithelium and mesenchyme, similar to other epithelial appendages. In this study, we reconstituted the reciprocal signaling interactions between human fetal dental epithelial cells and mesenchymally derived dental pulp cells, to study the signaling network involved in odontogenesis.

Methods: Dental epithelial cells, isolated from human fetal tooth organs, were mixed with Matrigel and seeded on the upper chamber of transwell 24-well plates. Human dental pulp cells, including a small subgroup of STRO1 expressing mesenchymal stem cells, were grown on the lower chambers of transwell plates. Dental epithelial cells in Matrigel, or mesenchymal cells alone, were cultured on the upper chamber or lower chamber of transwell plate as controls. After three weeks in co-culture, the dental epithelial cells /Matrigel complex were fixed, sectioned for H&E and immunostained. Dental mesenchymal cells were collected for RNA purification and assayed for collagen type I expression. SuperArray analysis was used to compare the expression of extracellular matrix and adhesion molecules between epithelial cell controls and co-cultured epithelial cells.

Result: PCR showed that collagen type I mRNA expression in co-cultured dental mesenchymal cells was significantly increased. Real time PCR and immunostaining showed increased expression of amelogenin by epithelial cells in co-culture. Meanwhile, SuperArray analysis indicated that E-cadherin, integrin b7 and a2b were up-regulated in the co-cultured epithelial cells.

Conclusion: Human fetal dental epithelial cells and dental pulp cells grown in co-culture underwent reciprocal signaling to induce differentiation of both cells types. These dental epithelial cells and pulp mesenchymal cells are valuable tools for studying epithelial-mesenchymal signaling interactions.

This study was supported by NIDCR grants R21-DE017910 to PDK and 2007 UCSF Dental School Dean Creativity Fund to YZ.