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

Abstract

Cells of the craniofacial skeleton are derived from a common mesenchymal progenitor. The regulatory factors that control their differentiation into various cell lineages are unknown. To investigate the biological function of dentin matrix protein 1 (DMP1), an extracellular matrix gene involved in calcified tissue formation, stable transgenic cell lines and adenovirally infected cells overexpressing DMP1 were generated. The findings in this paper demonstrate that overexpression of DMP1 in pluripotent and mesenchyme-derived cells such as C3H10T1͞2, MC3T3-E1, and RPC-C2A 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. The genes studied include transcription factors like core binding factor 1 (Cbfa1), bone morphogenetic protein 2 (BMP2), and BMP4; early markers for extracellular matrix deposition like alkaline phosphatase (ALP), osteopontin, osteonectin, and osteocalcin; and late markers like DMP2 and dentin sialoprotein (DSP) that are expressed by terminally differentiated odontoblasts and are responsible for the formation of tissue-specific dentin matrix. However, this differentiation pathway was limited to mesenchyme-derived cells only. Other cell lines tested by the adenoviral expression system failed to express odontoblastphenotypic specific genes. An in vitro mineralized nodule formation assay demonstrated that overexpressed cells could differentiate and form a mineralized matrix. Furthermore, we also demonstrate that phosphorylation of Cbfa1 (osteoblast-specific transcription factor) was not required for the expression of odontoblast-specific genes, indicating the involvement of other unidentified odontoblast-specific transcription factors or coactivators. Cell lines that differentiate into odontoblast-like cells are useful tools for studying the mechanism involved in the terminal differentiation process of these postmitotic cells.

Identification of Full-Length Dentin Matrix Protein 1 in Dentin and Bone

“…The distinctive feature of DMP1 is the presence of a large number of acidic domains, a property that implicates it as a possible participant in regulating matrix mineralization. This purported biological function is supported by observations that MC3T3-E1 cells overexpressing DMP1 demonstrate an earlier onset of mineralization and the formation of a significantly larger size of the induced mineralized nodules compared to nontransfected control cells [4]. Findings from Dmp1 knockout mouse experiments and gene mutation studies on human osteomalacia strengthen the conclusion that DMP1 plays an important role in bone and dentin mineralization [5][6][7].…”

Dentin matrix protein 1 induces cytodifferentiation of dental pulp stem cells into odontoblasts

“…14 To investigate the biological role of DMP1 during dentin mineralization, stable transgenic cell lines and adenovirally-infected cells overexpressing DMP1 were generated. 15 Data from these experiments demonstrate that overexpression of DMP1 in pluripotent and mesenchyme-derived cells such as C3H10T1/2, MC3T3-E1 and RPC-C2A can induce these cells to differentiate and form functional odontoblast-like cells. These transformed cells had the ability to express markers for terminally differentiated odontoblasts, namely DSP and DMP2.…”

Immunohistochemical localization of dentin matrix protein 1 in human dentin

“…In particular, DMP1 has been shown to have similar functions as dentin sialophosphoprotein and to be detected in primary dentin with a marked decrease in tertiary dentin (Moses et al 2006). DMP1 has been shown in vitro to facilitate initiation of mineral nucleation at specific sites during bone and dentin formation and to prevent spontaneous calcium phosphate precipitation in areas in which mineralization is not desirable, thus regulating the temporal and spatial aspects of mineral initiation (Narayanan et al 2001;He et al 2005). The importance of DMP1 in mineralization processes has been well demonstrated by DMP1 gene knock-out experiments.…”