Endothelial injury induced by coronary angioplasty triggers mobilization of endothelial progenitor cells in patients with stable coronary artery disease 1

Despite the wider use of drug-eluting stents, the rate of complications following angioplasty, mainly stent thrombosis and in-stent restenosis, is still limiting [1]. These complications are the consequences of endothelial injury and may depend on the efficiency of the healing process for the re-establishment of the endothelial monolayer. This balance between damage and repair is therefore of critical importance in determining angioplasty outcomes [2]. Circulating endothelial cells (CEC) can be used to monitor both functional and physical endothelial integrity [3]. They are non-hematopoietic cells, originated from sloughing of the injured vessel wall. These cells are defined by the expression of endothelial markers, the absence of leukocyte and immaturitymarkers, and the lack of proliferative potential in vitro [3]. CEC are found in very low concentration in healthy subjects [4] but increased numbers are described in various cardiovascular clinical settings with significant diagnosis and prognostic value [5–9]. Repair of an injured endothelium has been recently shown to involve circulating endothelial progenitor cells (EPC). These cells are defined as bonemarrowderived circulating cells with an immature endothelial phenotype, a high clonogenic potential in vitro and a specific capacity to contribute to angiogenesis in vivo [10,11]. The baseline number of circulating EPC depends on numerous factors among which are coronary artery disease severity, cardiovascular risk factors, and aging [12,13]. The main triggers of EPC mobilization from bone marrow to peripheral blood are ischemia and vascular trauma [14–16]. Although experimental models of vascular injury have suggested that exogenous EPC could play a critical role in the restoration of the endothelial lining [17–19], whether endothelial injury induced by coronary angioplasty is a sufficient stimulus to trigger EPC mobilization in coronary artery disease (CAD) patients is still unknown. We investigated the effect of coronary angioplasty on EPC levels in patients with CADand determine the relationship with the endothelial damage assessed by CEC counts. Patients with stable angina with need for scheduled angioplasty on a native coronary were enrolled after an informed consent was obtained. Exclusion criteria were acute coronary syndromes (ACS) within the two previous weeks, elevated preprocedural troponin Ic (cTnI), concurrent illness that could affect progenitor cell count. Coronary angioplasty and sirolimuscoated stent implantation were performed according to institutional standards, using a balloon inflation time of 30 s at 20 atmospheres. Blood samples were obtained before angioplasty (pre-precutaneous coronary intervention [PCI]), immediately after the end of the procedure (post-PCI), then 6, 24, 48 h and 7 days after PCI. CEC were counted using CD146-based immunomagnetic separation as previously described [4]. Circulating hematopoietic progenitor cells (HPC) were analyzed using flow cytometry (Epics XL Cytometer; Beckman Coulter, Villepinte, France) after staining of whole blood with fluorescein isothiocyanate (FITC)-labeled monoclonal mouse antihuman CD45 antibody, phycoerythrin (PE)-labeled monoclonal mouse antihuman CD34 antibody and 7AAD (Stemkit ; Beckman Coulter). Absolute numbers of HPC lL were determined using calibration beads according to manufacturer’s instructions. The number of circulating EPC was determined using a colony-forming assay according to method ofHill et al. [12]. Results were expressed in number of CFU-EC per 10 cells. Correspondence: Françoise Dignat-George, INSERM UMR 608, UFR de Pharmacie, 27 Boulevard Jean Moulin, 13385 Marseille cedex 5, France. Tel. : + 33 4 91 83 56 00; fax: + 33 4 91 83 56 02; e-mail: dignat@ pharmacie.univ-mrs.fr