Stent thrombosis is a serious, although rare, complication of percutaneous coronary intervention (PCI). Some data from randomized trials indicate a higher risk for drug- eluting stents (DES) thrombosis. Furthermore, it has been shown that the most powerful histological predictor of stent thrombosis was endothelial coverage and that reendothelialization was delayed after implantation of first-generation DES compared with baremetal stents (BMS) as from the first month after PCI. We do not have yet simple blood test biomarkers that could reflect the ongoing process of stent reendothelialization. MicroRNAs are small, endogenous, noncoding RNAs, easily detectable in plasma, involved in a variety of cellular processes via suppression of specific target mRNAs and could be such biomarkers. Some of them have been linked to endothelial function and reendothelialization in animal or in vitro studies. We hypothesized that the expression of certain microRNAs was informative of stent endothelialization. We therefore sought beforehand to determine wether stent type and stent length could influence the expression of candidate microRNAs in human peripheral blood. Between July 2008 and December 2013, all patients who underwent coronary angioplasty in our centre were asked to attend a systematic consultation one month after revascularization for blood sampling. Sixty patients with a single-vessel disease meeting over twenty clinical, biological, echocardiographic and angiographic criteria were selected: 30 with a BMS and 30 with a DES, with a balanced ratio of short (≤15mm) and long (>15mm) stents in each group. Twenty eight microRNAs were chosen based on a review of literature. Their expression was measured using qRT-PCR in plasma samples collected at one month. Levels were normalized to cel-miR-39 and compared between the two groups of patients. The results are currently under analysis (table next page).