Résumé :
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Coronary restenosis, results mainly from the proliferation of vascular smooth muscle cells (VSMC). Here, we determine whether in human arteries, the cardiac isoform of the sarco/endoplasmic reticulum calcium ATPase, SERCA2a controls VSMC proliferation via calcium-dependent calcineurin/NFAT signalling pathway. In atherosclerotic coronary arteries (CA) SERCA2a and the ryanodine receptor (RyR2) were expressed only in differentiated VSMC from the media but not in the neointima, containing mainly dedifferentiated cells. Primary CA VSMCs lost SERCA2a and RyR within 3 days after induction of proliferation. SERCA2a gene transfer inhibited VSMC proliferation through inhibition of NFAT leading to down regulation of cell cycle controlling proteins cyclin D1 and Erg1. Single-channel patch-clamp recording showed that SERCA2a gene transfer inhibited basal voltage-independent Ca2+ influx. Promoter-reporter assay showed that in human VSMCs NFAT was activated by store-dependent Ca2+ influx, inhibited by depolarisation-induced Ca2+ influx and its transcriptional activity strongly correlated with proliferative state, as demonstrated by Ca2+ channels blockers, expression of VIVIT (NFAT inhibitory peptide) or constitutively active NFAT. Furthermore, SERCA2a gene transfer prevented vascular remodelling and reduced neointima formation in an ex-vivo model of injury: the left internal mammary arteries (MA), injured and kept 2 weeks in organ culture under constant pressure and flow (intima/media ratio was 0.07 ± 0.01 vs 0.40 ± 0.03 in ?Gal-infected arteries, p<0.001, n=5). In conclusion, in human SERCA2a controls proliferation of VSMC and neointima formation via inhibition of basal voltage-independent Ca2+ influx and transcription factor NFAT. These findings could have potential implications for treatment of intervention-induced restenosis.
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