The actions of protein S (PS) on the scratch injury-induced proliferation of rat astrocytes (AC) were studied. PS (10-300 nM) markedly inhibited [3H]thymidine incorporation into injured AC. The effect of 100 nM PS was comparable with that of transforming growth factor-β1 (TGF-β1; 20 ng/ml). The incorporation of bromodeoxyuridine, which is usually detectable in AC along the border of the wound, was undetectable in the presence of 300 nM PS. The level of PS mRNA in the injured AC was slightly increased 15 h after the injury, although the level of its receptor, Tyro 3 mRNA was not changed significantly. The results of the present study suggest that PS plays an important role in tissue repair processes in the central nervous system (CNS) by suppressing the proliferation of AC as in the case of TGF-β1.
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