Oxidized low-density lipoprotein induces endothelial progenitor cell senescence, leading to cellular dysfunction

1. Recent studies have revealed an association between coronary risk factors and both the number and function of bone marrow-derived endothelial progenitor cells (EPC). We investigated the effect of oxidized low-density lipoprotein (ox-LDL) on the senescence of EPC, leading to cellular dysfunction. 2. Endothelial progenitor cells were isolated from human peripheral blood and characterized. The exposure of cultured EPC to ox-LDL (10 mug/mL) significantly accelerated the rate of senescence compared with control during 20 days in culture as determined by acidic beta-galactosidase staining. Oxidized LDL-induced EPC senescence was significantly inhibited by pretreatment with either lectin-like ox-LDL receptor-1 (LOX-1) antibody (Ab) or atorvastatin (P < 0.01). 3. Because cellular senescence is critically influenced by telomerase, which elongates telomeres, we measured telomerase activity using a polymerase chain reaction-ELISA-based assay. Oxidized LDL significantly diminished telomerase activity to approximately 50%, an effect that was significantly abolished by pretreatment with either LOX-1 Ab or atorvastatin (P < 0.01). 4. We examined whether ox-LDL-induced EPC senescence translates into EPC dysfunction. An MTS assay disclosed an inhibitory effect of ox-LDL on EPC proliferation. In a Matrigel assay, EPC treated with ox-LDL were less likely to participate in network fomation compared with controls. 5. In conclusions, ox-LDL accelerates the onset of EPC senescence, which may be related to telomerase inactivation. Oxidized LDL-induced EPC senescence leads to the impairment of proliferative capacity and network formation.