Roles of Extracellular Matrix Molecules in Differentiation of Odontoblast-like Cells from Dental Pulps of pOBCol2.3GFP Transgenic Mice

There is increasing experimental evidence suggesting that the adult dental pulp contains progenitor cells capable of giving rise to a new generation of odontoblasts secreting dentine-like tissue. However, signaling pathways regulating differentiation of pulp cells into odontoblasts have not been clearly identified. Objectives: To examine the roles of extracellular matrix (ECM) molecules in differentiation of pulp cells into a new generation of odontoblast. Methods: The coronal portion of pulps from the first molars of 5-day old pOBCol2.3GFP transgenic mice were isolated and prepared for explantation. These transgenic mice carry a Green Fluorescent Protein (GFP) reporter gene fused to 2.3 kb fragment of rat Col1a1 regulatory sequences. Gelatin sponges seeded with dissociated pulp cells (GSP) were transplanted under the dorsal skin of SCID hosts for 6 weeks. Intact portion of pulps (IPP) were transplanted under the kidney capsule of hosts for 2 weeks. Phenotypes of the differentiated cells originating from dental pulp were characterized by morphology of the cells, their associated mineralized matrices and their expression of Col1a1-2.3-GFP and DSPP. Results: IPP formed tubular- and atubular-containing mineralized islands with cells expressing Col1a1-2.3-GFP. The atubular-mineralized islands in IPP contained numerous osteocytes and osteoblasts expressing high levels of Col1a1-2.3-GFP. Tubular-containing mineralized islands in IPP were lined with odontoblast-like cells expressing high levels of Col1a1-2.3-GFP and DSPP with extended Col1a1-2.3-GFP-expressing processes. GSP also formed tubular- and atubular-containing mineralized islands but in lesser amounts. Mineralized islands formed by GSP contained numerous Col1a1-2.3-GFP expressing osteoblasts, but few osteocytes and odontoblast-like cells. Conclusion: These observations provide evidence for essential roles of ECM molecules in differentiation of odontoblast-like cells from dental pulp. This work was supported by NIH grant DE13363.