Cementum is a hard connective tissue, produced by cementoblasts during tooth root formation, which provides for the attachment of the periodontal ligament to the roots and surrounding alveolar bone. Establishment of this attachment is an important event in the regeneration of lost periodontal tissues. We examined whether or not odontoblast conditioned media(CM) have a regulatory influence on the differentiation and mineralization of cementoblasts(murine cementoblastic cell line, OCCM-30) in vitro. To identify the effect of odontoblast conditioned media and dentin non collagenous proteins (dNCPs) on cementoblast differentiation and mineralization, we treated CM and dNCPs to cementoblast then differentiated the cells for 14 days. To evaluate the formation of mineralized nodules alizarin-red S staining was performed at 0,4,7 and 14 days. Expression of cementum matrix genes was measured by RT-PCR. Mineralization of cementoblasts was accelerated with CM from odontoblastic MDPC-23 and OD-11. The expression of BSP, ALP, and OC mRNA in cementoblastic OCCM-30 cells was facilitated by the MDPC-23 and OD-11 cells. The extracted dNCPs had little influence on the proliferation, cell cycle modification, and chemotaxis of OCCM-30 cells. Although the dNCPs did not exhibit chemotactic activities for cementoblasts, the dNCPs promoted the differentiation and mineralization of cementoblasts. In conclusion, the dentin matrix protein, or the secreted products of odontoblast, facilitates cementoblast differentiation and mineralization. This represents a new approach and suggests another avenue for cementum regeneration.

Nuclear factor I-C (NFI-C) null mice demonstrated aberrant odontoblast differentiation, abnormal dentin formation, and thus molar lacking roots. However, the mechanism by which the disruption of NFI-C gene affect the expression of other genes in dental pulp cells remains unknown. In this study, in order to understand this mechanism, the gene expression of pulp cells in NFI-C deficient mice were compared to those of wild-type mice by cDNA microarray analysis. According to the cDNA microarray profile comparison, the disruption of NFI-C gene increased the expression of TGF-β and TGF-β receptor, whereas it decreased the expression of Smad proteins. Interestingly, most of the FGF-related genes were down-regulated in pulp cells by NFI-C gene disruption. Among the cell cycle-related genes, the expression of p16 and p18 were increased by NFI-C disruption, but the expression of cy clin E1 and cy clin D1 were decreased by NFI-C disruption. These results indicate that the disturbance of NFI-C gene suppressed the proliferation of pulp cells and up-regulated the expression of TGF-β and its downstream signaling molecules during root formation, contributing to the formation of short root containing abnormal dentin.

Dentin is a mineralized tissue formed by odontoblasts that are differentiated from ectomesenchymal cells , The molecul ar mech anism of odontoblast diffe rentiation remains unclear, Amino acid transporters play an important role in s up plying nutri tion to normal a nd ca ncer cells including odntoblasts, and for cell proliferation , Amino acid transport system L is a maj or nutrient t ransport system responsible for the Na+' -independent transport o[ neutral amino acids incJuding several essentiaJ amino acids , The system L is divided into two major subgroups, the L-type amino acid transporter 1 (LAT1) and the L-type amino acid transporter 2 (LAT2) , In this study, the expression pattern and role of amino acid transport system L were, therefore, investigated in the differentiation of MDPC-23 cells derived from mouse dental papilla celJs , To determi ne the expression Jevel o[ amino acid transport system L participating in intracelJ ular transport of amino acids in the differentiat ion 0 1' MDPC-23 cells, it was examined by RT-PCR, observation of cell morphoJogy‘ A1izaline red-S staining ancl uptake analysis after inclucing experimental differentiation in MDPC-23 cells The res ults were as follows , The LAT1 mRNA was expressed in the early stage of MDPC-23 cell differentiation , The expression leveJ was gradually increased by time course and it was decreased after the late stage, The LAT2 mRNA was not observed in the earJy stage of MDPC-23 cell differentiation, The LAT2 mRNA was expressed at the 11 days 0 1' MDPC-23 cell differentiation and the expression level was gradually decreased by time course, There was no changes in the expression level of 4F2hc mRNA, the cofactor of LAT1 and LAT2, during the differentiation of MDPC-23 cells , The expression of ON mRNA was graduaJJy decreased but the expression of ALP mRNA was increased during differentiation of MDPC-23 cells , The L-Ieucine uptake was increased by time cour se from the early stage to the 9 days in MDPC-23 cell differentiation , The amount of L-Ieucine uptake was maintained to the 11 and 14 days of MDPC-23 cell differentiation As the resul ts‘ it is considered that among neutral amino acid transport system L in differentiation of MDPC-23 cells , the LATl has a key role in cell proliferation in the early stage and middle stage of cell differentiation and the LAT2 has an important roJe in ceJJ differenti ation and mineralization in the Jate stage of cell differentiation for providing cells with neutral a mino acids incJuding several essentiaJ amino acids

The periodontal ligament (PDL) is that soft, specialized connective tissue situated between the cementum covering the root of the tooth and bone forming the socket wall. The PDL is a connective tissue particularly well adapted to its principal function, supporting the teeth in their sockets and at the same time permitting them to withstand the considerable force of mastication. During the life time, PDL is usually exposed to mechanical stress by mastication. However, little is known about the gene which is related to the mechanical stress in PDL. UNC-50 (PDLs22) was identified and isolated from D. melanogater and C. elegance. This gene was also regulated in sensory bristle for mechanotransduction in D. melanogaster. In this study, to uncover the relationship between UNC-50 and mechanical stress, we induced the mechanical stress by medium displacement in cementoblast cell line. After mechanical stress induction UNC-50 expression was analyzed by RT-PCR, Real-time PCR, and western analysis. The expression of UNC-50 was increased after medium displacement of cementoblast in vitro. Collagen type I, type III, and osteonection mRNAs were also strongly expressed after mechanical stress induction. The results of this study suggest that UNC-50 might responsible for molecular event in PDL inducing cementoblast under mechanical stress.

Periodontalligament (PDL) fibroblasts have an ectomesenchymal origin and are known to participate not only in formation of PDL but also in the repair and regeneration of the a이acent alveolar bone and cementum. However, little is known about the molecular mechanism which is related to the development and differentiation of PDL cells. Recendy, we reported the PDLs (a periodontalligament-specific) 22 as a PDL fibroblast-specific mRNA which is not expressed in gingival fibroblasts. In this study, to examine the expression and functional characterization of PDμ22 mRNA and prαein in development and differentiation of periodontal 따sue ， we carried out northem analysis, insitu hybridization, immunofluorescence and immunohistochemistry. The expression of PDLs22 mRNA was increased with PDL cell differentiation from the confluent to multilayer stage but decreased slighdy with mineralized nodule formation in vitro. πle PDLs22 protein was localized on the nuclear membrane and expressed throughout the differentiation of PDL fibroblasts in vitro. The PDLs22 mRNA and protein were expressed in the differentiating cementoblasts, PDL fibroblasts and osteoblasts along the r∞t surface and alveolar bone of the developing rat teeth. These results indicate that the PDLs22 plays an irnportant role in the differentiation of cementoblasts and osteoblasts and thus homeostasis of cementum, PDL and alveolar bone.