Sox2 maintains epithelial cell proliferation in the successional dental lamina.

OBJECTIVES: The successional dental lamina is the distinctive structure on the lingual side of the vertebrate tooth germ. The aim of this study was to investigate the relationship among Sox2, Claudin10 and laminin5 and the role of Sox2 in successional dental lamina proliferation during vertebrate tooth development. MATERIALS AND METHODS: To understand the successional dental lamina, two types of successional tooth formation, that in geckos (with multiple rounds of tooth generation) and that in mice (with only one round of tooth generation), were analysed. RESULTS: Unique coexpression patterns of Sox2 and Claudin10 expression were compared in the successional dental lamina from the cap stage to the late bell stage in the mouse tooth germ and in juvenile gecko teeth to support continuous tooth replacement. Furthermore, Laminin5 expression was shown in the cap stage and decreased after the bell stage. Upon comparing the epithelial cell cycles and cell proliferation in successional dental lamina regions between mouse and gecko molars using BrdU and IdU staining and pulse-chase methods, distinctive patterns of continuous expression were revealed. Moreover, Sox2 overexpression with a lentiviral system resulted in hyperplastic dental epithelium in mouse molars. CONCLUSIONS: Our findings indicate that the regulation of Sox2 in dental lamina proliferation is fundamental to the successional dental lamina in both species.

Cell cycle of the enamel knot during tooth morphogenesis.

Enamel knot (EK) is known to be a central organ in tooth development, especially for cusp patterning. To trace the exact position and movement among the inner dental epithelium (IDE) and EK cells, and to monitor the relationship between the EK and cusp patterning, it is essential that we understand the cell cycle status of the EK in early stages of tooth development. In this study, thymidine analogous (IdU, BrdU) staining was used to evaluate the cell cycle phase of the primary EK at the early casp stage (E13.0) and the gerbil embryo (E19) in a developing mouse embryo. The centerpiece of this study was to describe the cell cycle phasing and sequencing during proliferation in the IDE according to the expression of IdU and BrdU following their injection at calculated time points. The interval time between IdU injection and BrdU injection was set at 4 h. As a result, the cell cycle in the IDE of the mouse and gerbil was found to be synchronous. Conversely, the cell cycle in primary EKs of mice was much longer than that of the IDE. Therefore, the difference of cell cycle of the IDE and the EK is related to the diversity of cusp patterning and would provide a new insight into tooth morphogenesis.

Design and synthesis of 4-aryl-4-oxobutanoic acid amides as calpain inhibitors.

The involvement of mu-calpain in neurological disorders, such as stroke and Alzheimer's disease has attracted considerable interest in the use of calpain inhibitors as therapeutic agents. 4-Aryl-4-oxobutanoic acid amide derivatives 4 were designed as acyclic variants of mu-calpain inhibitory chromone and quinolinone derivatives. Of the compounds synthesized, 4c-2, which possesses a 2-methoxymethoxy group at the phenyl ring and a primary amide at the warhead region most potently inhibited mu-calpain (IC(50)=0.34 microM). Our findings suggest that the 4-aryl-4-oxobutanoic acid amide derivatives should be considered as a new family of mu-calpain inhibitors.