There have been growing evidences suggesting that circulating fibrocytes (CFs) play a pivotal role in tissue repair and fibrosis.In contrast, Angiotensin-(1-7) [Ang-(1-7)], in recent studies, has been shown to exert powerful effect against fibrosis.The purpose of this study is to examine direct effect of Ang-(1-7) on CFs.Total mononuclear cells (MNCs) were isolated from peripheral blood by Ficoll density gradient centrifugation.CFs were identified using laser scanning confocal microscope as adherent cells with double positive fluorescent staining for both cell antigen of CD34 and Collagen Ⅰ.After 14 days in culture,CFs were stimulated with Ang-(1-7) at series of final concentrations of 10, 100, 1000, 10000 nmol/l, for 24,48, 72 h.Cell number, proliferation and apoptosis were determined, respectively, by Hematoxylin Eosin staining, Cell Counting Kit-8 (CCK8) assay and Annexin V/Propidium Iodide binding assay.The collagen content of CFs was measured by the concentration of hydroxyproline, which was detected using the enzymatic digestion method.The expression of eNOS was assayed by Wstern Blot analysis.We found that Ang-(1-7) increases CFs apoptosis and eNOS production.In addition, Ang-(1-7) decreases CFs number,proliferative capacity and collagen-secretion in a concentration-and time-dependent manner.These data suggest that Ang-(1-7) suppresses the number and function of CFs, possibly through increasing eNOS production in the CFs.