ClC chloride channels in tooth germ and odontoblast-like MDPC-23 cells

Objective: To detect expression of ClC chloride channel mRNA in tooth germ and odontoblasts, and explore the affect Of chloride channel function on cell proliferation and cell cycle. Design: We extracted total RNA of tooth germ from newborn. C57BL mice and mouse odontoblast-like cells (MDPC-23), then detected mRNA expression of chloride channel genes Clcn1-7 with RT-PCR. We used chloride channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) to interfere with chloride channel function of MDPC-23 cells. Cell proliferation rate and cell cycle were detected with MTT assay and flow cytometry, respectively. Student's t-test was used to determine statistical significance between control and treatment groups. Results: The mRNA of Clcn1-7 chloride channel genes was expressed in tooth germ of newborn mice. Clcn3, Clcn5 and Clcn7 mRNAs; were expressed in MDPC-23 cells. NPPB slowed down the proliferation rate of MDPC-23 cells from day 2 to day 4 (P < 0.01), and also changed the proportion of cell cycle phase. Comparing to the control, the proportion of G2/M phase cells reduced from 3.93 +/- 2.62% to 0.54 +/- 0.25% (P < 0.05). The ratio of G1/G2 increased from 1.86 +/- 0.01 to 1.95 +/- 0.02 (P < 0.05). Conclusions: There is abundant chloride channel gene expression in tooth germ. Some of these chloride channels may regulate tooth development through effects on cell proliferation and cell cycle signal pathway. (C) 2008 Elsevier Ltd. All rights reserved.