Background The vascular endothelium is a vital organ whose health is essential to normal vascular physiology and whose dysfunction can be a critical factor in the pathogenesis of vascular disease.Postnatal bone marrow contains a subtype of unique progenitor cells that have the capacity to differentiate into functional endothelial cells.Hence, these cells have been termed endothelial progenitor cells (EPCs).KLF4 has recently been independently implicated byindependent groups as being important in maintaining pluripotent state of stem cells.This present study was designed to investigate the expression and significane of transcription factors KLF4 in differentiated endothelial progenitor cells.