Effects of osteopontin on functional activity of late endothelial progenitor cells

The aim of this study is to investigate the effect of osteopontin (OPN) on functional activity of late endothelial progenitor cells (EPCs). Total mononuclear cells (MNCs) were isolated from human umbilical cord blood by Ficoll density gradient centrifugation, and then the cells were plated on fibronectin-coated culture plates. Late EPCs were positive for both 1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine-labeled acetylated low-density lipoprotein (DiI-acLDL) and fluorescein-isothiocyanate-conjugated Ulex europaeus agglutinin lectin (UEA-1). Expression of von Willbrand factor (vWF) and kinase insert domain receptor (KDR) were detected by indirect immunofluorescence staining. Late EPCs of 3-5 passages were treated for 24 h with OPN (to make a series of final concentration: 0.005 µg/ml, 0.01 µg/ml, 0.05 µg/ml, 0.5 µg/ml, 2.5 µg/ml), or vehicle control. The proliferation, migration, and in vitro vasculogenesis activity of late EPCs were assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, modified Boyden chamber assay and an in vitro angiogenesis assay, respectively. Late EPCs adhesion assay was performed by replating cells on fibronectin-coated plates, and then adherent cells were counted. Incubation with OPN dose-dependently inhibited the proliferative, adhesive, and in vitro vasculogenesis capacity and increased migratory activity of late EPCs.