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Effects of mechanical stress on the mRNA expression of S100A4 and cytoskeletal components by periodontal ligament cells.

The periodontal ligament (PDL) functions under constant mechanical stress, and PDL cells obviously control PDL functions under such conditions. We have previously found that the mRNA expression of the Ca2+-binding protein S100A4 and beta-actin is higher in the PDL from erupted teeth than in the PDL from teeth under eruption. This suggested a role for S100A4 in the response of PDL cells to mechanical stress, possibly by coupling Ca2+ and the cytoskeletal system. In the present study, we investigated the direct effects of cyclical stretching on the mRNA expression of S100A4 and two cytoskeletal components (beta-actin and alpha-tubulin) by PDL cells. In Northern blotting analysis, the expression of S100A4, beta-actin, and alpha-tubulin mRNAs was higher in the PDL from fully erupted and functional bovine teeth than in partially erupted ones. Similarly, when bovine PDL cells were mechanically stimulated by means of the Flexercell Strain Unit, the expression of S100A4, beta-actin, and alpha-tubulin mRNAs increased over the control levels. The results of our present study indicate that S100A4 is involved in the responses of PDL cells to mechanical stress possibly by coupling Ca2+ to the cytoskeletal system in these cells.