C015 Identification of new biomarkers of vascular smooth muscle cells ageing from transcriptomic and mirna studies

Our aim was to better understand the changes in expression in vascular smooth muscle cells during ageing using non pathological human mammary artery. We defined 2 groups of patients: a group of young ones, Y, composed of men under 60 years old (43 to 60, 13 patients) and a group of old ones, O, composed of men over 75 years old (75 to 83, 11 patients). After dissection of the artery, medias were crushed and total RNA including microRNAs were collected. Using microRNA array, we found that 90 microRNAs are expressed in the media from these patients. After statistical analysis no change in microRNA expression was found between the O and the Y groups. Therewere a lot of heterogeneity between the patients inside each group. It seems that vascular aging do not affect miRNA expression in our study, but the two groups of age were maybe too close to see some regulation. Using DNA microarray, we found 233 genes significatively regulated between the O group and the Y group. Among them, 60 genes were modulated more than 1.4 fold. We choose to verify these expression changes for 20 of them (the most regulated, newly identified or implicated in ageing) by quantitative RT-PCR and confirmed the regulation for 14 genes: compared to the Y, in the O group we saw an overexpression (from 1.4 to 8 fold) for 9 genes and an inhibition (from -1.5 to -3.2 fold) for 5 other genes. We focused on overexpressed Osteopontin, WISP1 (Wnt inducible secreted protein 1), Gamma S Crystallin (for instance only described in lens and which could be a chaperon) and on inhibited Cystathionase (which produces H2S, an artery vasodilatator). The changes observed in mRNA expression were also seen in protein expression by Western Blot although less clearly due to strong inter-individual variability. We also found that Wnt/beta-catenin signalization pathway was more activated in the O group. We notably found that beta-catenin phosphorylation on Ser 552 and Ser 675, which leads to betacatenin transfer in the nucleus, was increased.