Overexpression of DMP1 both in-vivo and in-vitro results in mineralized tissue formation

The regulatory factors that control the differentiation of neural-crest cells into odontoblasts are unknown. Objective: To investigate the biological function of dentin matrix protein1 (DMP1), an extracellular matrix gene involved in calcified tissue formation, we have generated stable transgenic cell lines, adenovirally-infected cells overexpressing DMP1 and transgenic mice overexpressing DMP1. Method: The genes that we have studied include transcription factors like Cbfa1, BMP2 and 4, early markers for extracellular matrix deposition like ALP, OPN, ON and OCN and late markers like DMP2 and DSP that represents terminal differentiation of odontoblasts and formation of tissue-specific dentin matrix. Result: For the first time we are able to demonstrate that overexpression of DMP1 in pluripotent and mesenchymal derived cells such as C3H10T1/2 and MC3T3-E1 can induce these cells to differentiate and form functional odontoblast-like cells. Functional differentiation of odontoblasts requires unique sets of genes being turned on and off in a growth and differentiation specific manner. However, this odontoblast differentiation was limited to mesenchymal derived cells only. Other cell lines tested by adenoviral expression system failed to express odontoblast-phenotypic specific genes. In-vitro and in-vivo mineralized nodule formation assay was used to demonstrate that overexpressed cells could differentiate and form a mineralized matrix. Conclusion: Cell lines that differentiate into odontoblast- like cells are useful tools for studying the mechanism involved in the terminal differentiation process of these post-mitotic cells. Supported by NIH-DE 11657.