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

System L amino acid transporter is a major route for providing living cells with neutral amino acids including several essential amino acids. To elucidate the expression pattern of L-type amino acid transporter 1 (LAT1) in the bone formation process, the expressions of LAT1 and its subunit 4F2 heavy chain (4F2hc) were investigated in the healing process after the implantation of bone graft materials in the calvarial osseous defected rats. Circular calvarial defects (1 cm in diameter) were made midparietally. The rats were divided into 4 groups of 1 control group and 3 experimental groups. In the control group, the defect was only covered with soft tissue flap. In the experimental groups, they were filled with human particulate dentin (particulate dentin group), with plaster of Paris (plaster of Paris group) and with the mixture of human particulate dentin and plaster of Paris with ratio of 2 : 1 by weight (mixture group). The rats were sacrificed at the 1, 2, 4 and 8 weeks after operation and the RT-PCR analysis and immunohistochemical analysis were performed. In the RT-PCR analysis, the mRNAs of LAT1 and 4F2hc were strongly detected in all 4 groups. In the immunohistochemical analysis, at 1 week after operation, the LAT1 protein and its subunit 4F2hc protein were mainly expressed in the osteoblasts, osteocytes and interstitial tissues of the around the defect and inner part of newly forming bone in all 4 groups. The expressions of LAT1 and 4F2hc proteins were decreased at 2 and 4 weeks after operation. The LAT1 and 4F2hc proteins were scarcely expressed at 8 weeks after operation in all 4 groups. These results suggest that the LAT1 and its subunit 4F2hc highly expressed at the early stage of new bone formation and may have an important role in providing cells with neutral amino acids including several essential amino acids at that stage.