Bone morphogenetic protein 2 (Bmp2) is essential for odontogensis and dentin mineralization. Generation of floxed Bmp2 dental mesenchymal cell lines is a valuable application for studying the effects of Bmp2 on dental mesenchymal cell differentiation and its signaling pathways during dentinogenesis. Limitation of the primary culture of dental mesenchymal cells has led to the development of cell lines that serve as good surrogate models for the study of dental mesenchymal cell differentiation into odontoblasts and mineralization. In this study, we established and characterized immortalized mouse floxed Bmp2 dental papilla mesenchymal cell lines, which were isolated from 1st mouse mandibular molars at postnatal day 1 and immortalized with pSV40 and clonally selected. These transfected cell lines were characterized by RT-PCR, immunohistochemistry, and analyzed for alkaline phosphatase activity and mineralization nodule formation. One of these immortalized cell lines, iBmp2-dp, displayed a higher proliferation rate, but retained the genotypic and phenotypic characteristics similar to primary cells as determined by expression of tooth-specific markers as well as demonstrated the ability to differentiate and form mineralized nodules. In addition, iBmp2-dp cells were inducible and responded to BMP2 stimulation. Thus, we for the first time described the establishment of an immortalized mouse floxed Bmp2 dental papilla mesenchyma cell line that might be used for studying the mechanisms of dental cell differentiation and dentin mineralization mediated by Bmp2 and other growth factor signaling pathways. Tooth development involves sequential and reciprocal interactions between dental epithelial and mesenchymal cells, and proceeds through a series of cytodifferentiations in specific spatialtemporal patterns (Linde and Goldberg, 1993). Dentinogenesis is a complex process in which multiple signaling pathways converge to induce dentin formation and is controlled by many growth and transcription factors (Thesleff, 2003). The bone morphogenetic proteins (Bmps) are structurally related to the transforming growth factor beta (TGF-β) superfamily and were originally identified by their capacity to induce ectopic bone formation in rodents (Urist, 1965;Wozney et al., 1988). Members of the Bmp family have diverse biological functions during embryonic development (Hogan, 1996;Wu et al., 2003) including a vital role in osteogenesis (Chen et al., 2004;Rosen, 2009). Among the Bmp family members, Bmp2 has been extensively studied for its various biological functions during chondrogenic and osteogenic differentiation (Reddi, 1997;Ducy and Karsenty, 2000). Also, Bmp2 has been shown to promote dental pulp stem cell commitment to the odontoblast lineage in vitro ) and induces dental pulp cell differentiation and mineralization in vitro and in vivo (Nakashima, 2005;Chen et al., 2008). However, detail understandings of the molecular mechanisms of Bmp2 exerting its effects on tooth development and formation remain elusive in particular duri...

A 3.5-year-old girl presented to our clinic experiencing pain in her maxillary central incisors following traumatic injury during a fall. Radiographic examination revealed both primary maxillary central incisors with mid-root and apical third horizontal root fractures, respectively. Splinting with orthodontic brackets and stainless steel wire was performed. At 2 weeks, resorption of the apical fragments in both injured teeth was observed, and after 3 months, almost complete resorption was noted on radiographs. Tooth mobility at this point was back to physiologic levels and the splint was removed. After 2.5 years, the primary maxillary incisors were replaced by permanent incisors demonstrating normal tooth color, position, and root development. Although this case illustrated the favorable prognosis of two primary teeth with root fractures and severely mobile coronal fragments by a conservative approach, more scientific evidences are needed and frequent recalls are necessary when primary root fractures are attempted to be managed with splinting.

Bone morphogenetic protein 2 (Bmp2) is essential for osteoblast differentiation and osteogenesis. Generation of floxed Bmp2 osteoblast cell lines is a valuable tool for studying the effects of Bmp2 NIH Public Access

Bone morphogenetic proteins 2 and 4 (BMP2/4) are essential for osteoblast differentiation and osteogenesis. Generation of a BMP2/4 dual knock‐out (ko/ko) osteoblastic cell line is a valuable asset for studying effects of BMP2/4 on skeletal development. In this study, our goal was to create immortalized mouse deleted BMP2/4 osteoblasts by infecting adenoviruses with Cre recombinase and green fluorescent protein genes into immortalized murine floxed BMP2/4 osteoblasts. Transduced BMP2/4ko/ko cells were verified by green immunofluorescence and PCR. BMP2/4ko/ko osteoblasts exhibited small size, slow cell proliferation rate and cell growth was arrested in G1 and G2 phases. Expression of bone‐relate genes was reduced in the BMP2/4ko/ko cells, resulting in delay of cell differentiation and mineralization. Importantly, extracellular matrix remodeling was impaired in the BMP2/4ko/ko osteoblasts as reflected by decreased Mmp‐2 and Mmp‐9 expressions. Cell differentiation and mineralization were rescued by exogenous BMP2 and/or BMP4. Therefore, we for the first time described establishment of an immortalized deleted BMP2/4 osteoblast line useful for study of mechanisms in regulating osteoblast lineages. J. Cell. Physiol. 231: 1189–1198, 2016. © 2015 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

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