OBJECTIVEIn order to investigate the role of shear stress in the regulation of endothelial function, we assessed here effects of shear stress on tissue-type plasminogen activator in human endothelial progenitor cells (EPCs).

METHODSThe peripheral blood mononuclear cells were separated from healthy adult and inducted into EPCs, which were identified by double staining for the fluorescent labeled acetylated-LDL and lectin. EPCs were seeded on the small diameter artificial vessels, and then divided into four different experimental groups including stationary group, low-flow shear stress group (5 dyn/cm(2)), medium-flow shear stress group (15 dyn/cm(2)) and high-flow shear stress group (25 dyn/cm(2)). The levels of t-PA in EPC culture medium at 0 hour, 5 hours, 10 hours, 15 hours, 20 hours and 25 hours after culture were measured by enzyme-linked immunosorbent assay.

RESULTSThe peripheral blood mononuclear cells differentiated into EPCs after induction, which were positively labeled by fluorescent acetylated-LDL and lectin. Shear stress enhanced production of the t-PA by EPCs, which was paralleled to levels and times of shear stress.

CONCLUSIONSShear stress increases t-PA secretion by human EPCs, suggesting that shear stress not only regulates vascular endothelial function but also participates in the pathogenesis of arteriosclerosis.