Abstract 9907: Exposure to Oxidized LDL Converts Early Endothelial Progenitors Into Dendritic/Antigen Presenting Cells
Background- “Early” endothelial progenitor cells (eEPCs) derive from circulating monocytes in the presence of angiogenic factors. While eEPCs number and ability to form angiogenic cell clusters in culture are reduced by risk conditions, changes in their function have not been yet reported. Specific aims and Results - In the present work, we assessed whether eEPCs are functionally converted into dendritic cells (DCs) by exposure to oxidized LDL (Ox-LDL), a lipoprotein abundant in atherosclerotic plaques. eEPCs were derived by culturing mononuclear cells (MNCs) purified from buffy-coats of healthy blood donors into EGM-2 medium for 7 days. They were then primed for 3 days with a cytokine cocktail containing GM-CSF and IL4 (10 ng/ml) in 10% FBS containing medium. To promote DCs maturation, primed eEPCs were cultured for 2 further days with OxLDL (100μg/ml) in 1% FBS-containing medium. In these conditions, eEPCs showed a typical DCs morphology, acquired DC-specific markers CD80 and CD83 (both <1% vs. 88.1±3.5 and 30.0±5.8; C vs. Ox-LDL, P<.05, t-test, n=5) and underwent a robust upregulation of CD86 (48.6±10.1 vs. 81.9±5.1, C vs. Ox-LDL; P< .05, t-test, n=5), another DC-specific antigen. Mixed lymphocyte reaction (MLR) experiments revealed high levels of BrdU incorporation in CD3+ T-cells mixed in a 10:1 ratio with eEPCs-derived DCs. The percentage of BrdU+CD3+ cells was comparable to that of T-cells cocultured with control CD14+ cells-derived DCs (44.7±1.7 vs. 43.9±6.7, P> .05, t-test, n=3). Analysis of 30 cytokines released in the culture supernatant revealed a substantially overlapping secretome profile in eEPCs-derived and CD14+-derived DCs. In addition, they showed an angiogenic “fingerprint”, as witnessed by significantly (P< .05, t-test, n=3) higher expression of PDGF-BB (790±185 vs. 192±18, pg/ml), IL-8 (25.5±4.4 vs. 3.4±1.1 ng/ml), bFGF (3.5±0.7 vs. 1.0±0.43 pg/ml) and VEGF (535±19 vs 7.8±1.3 pg/ml), compared with CD14+-derived DCs. Conclusions - The present data show an unexpected pro-inflammatory conversion of human eEPCs in response to a potent "auto-antigen" such as OxLDL. This unravels a possible specific immune modulator role of these cells in patients with risk factors, thus contributing to progression of coronary artery disease.
- © 2012 by American Heart Association, Inc.