Résumé :
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Communication n° 686. Proliferation of vascular smooth muscle cells (VSMC) is associated with loose of sarco/endoplasmic Ca2+-ATP-ase (SERCA2a) resulting in increase of cytosolic Ca2+ and alteration of activity of Ca2+-dependent transcription factors CREB and NFAT. Mutation of the d-sarcoglycan gene in cardiomyopathic Syrian hamster CHF 147 induce abnormal Ca2+ handling and intracellular Ca2+ overload in cardiomyocytes. The aim of this study is to determine whether this mutation is also associated with dysfunction of vascular smooth muscle cells. We compared the proliferating response, expression of proteins involved in Ca2+ handling and activity Ca2+-regulated transcription factors in aortic VSMC freshly isolated from Syrian hamster CHF 147 and their controls the golden hamsters. Anatomopathologic analysis of thoracic aorta showed an important irregularity of media in Syrian hamster, suggesting proliferation and/or apoptosis of muscle cells. In the culture, Golden hamsters VSMC quickly proliferated in the presence of serum. By contrast, serum failed to increase cell number of Syrian hamster VSMC, and in the culture all cells were dead 10-15 days after beginning of the experiment. In Syrian hamster VSMC (freshly isolated or cultured 3 days with serum) an important nuclear fragmentation was revealed by Hoechst staining (25% vs 0% in control cells), suggesting apoptosis. In quiescent Golden hamster cells SERCA 2a, SERCA 2b and RyR were expressed, CREB was phosphorylated and NFAT was present in the cytosol. After serum induction, SERCA2a and pCREB disappeared, and NFAT was translocated to the nucleus. By contrast, in freshly isolated Syrian hamster cells SERCA 2a and pCREB were absent, and NFAT was already present in the nucleus. Exposure to serum (3 days) did not affect neither calcium pumps expression nor activity of Ca2+-regulated transcription factors. In conclusion, our results demonstrated the major alteration of phenotype of VSMC in Syrian hamster CHF 147.
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