Differentiation of embryonic mesenchymal cells to odontoblast-like cells by overexpression of dentin matrix protein 1

摘要

Cells of the craniofacial skeleton are derived from a commonmesenchymal progenitor. The regulatory factors that control theirdifferentiation into various cell lineages are unknown. To investigatethe biological function of dentin matrix protein 1 (DMP1), anextracellular matrix gene involved in calcified tissue formation,stable transgenic cell lines and adenovirally infected cellsoverexpressing DMP1 were generated. The findings in this paperdemonstrate that overexpression of DMP1 in pluripotent andmesenchyme-derived cells such as C3H10T1/2, MC3T3-E1, and RPC-C2A caninduce these cells to differentiate and form functionalodontoblast-like cells. Functional differentiation of odontoblastsrequires unique sets of genes being turned on and off in a growth- anddifferentiation-specific manner. The genes studied includetranscription factors like core binding factor 1 (Cbfa1), bonemorphogenetic protein 2 (BMP2), and BMP4; early markers forextracellular matrix deposition like alkaline phosphatase (ALP),osteopontin, osteonectin, and osteocalcin; and late markers like DMP2and dentin sialoprotein (DSP) that are expressed by terminallydifferentiated odontoblasts and are responsible for the formation oftissue-specific dentin matrix. However, this differentiation pathwaywas limited to mesenchyme-derived cells only. Other cell lines testedby the adenoviral expression system failed to expressodontoblast-phenotypic specific genes. An in vitromineralized nodule formation assay demonstrated that overexpressedcells could differentiate and form a mineralized matrix. Furthermore,we also demonstrate that phosphorylation of Cbfa1 (osteoblast-specifictranscription factor) was not required for the expression ofodontoblast-specific genes, indicating the involvement of otherunidentified odontoblast-specific transcription factors orcoactivators. Cell lines that differentiate into odontoblast-like cellsare useful tools for studying the mechanism involved in the terminaldifferentiation process of these postmitotic cells.