ObjectiveTo explore optimal conditions of isolation, culture and labeled with superparamagnetic iron oxide (SPIO) in vitro of rat bone marrow endothelial progenitor cells, and lay the foundations for the further EPCs tracer study in vivo. MethodsThe EPCs derived from rat bone marrow were isolated and cultured by using density gradient centrifugation, which were labeled with different concentrations SPIO, Prussian blue staining was used to detect the cells labeling rate, MTT assay was used to detect the cells proliferation activity, and Trypan blue staining was used to detect the cells vitality. ResultsEPCs gradually growed in monolayer arrangement about 7 d after cultured. When the concentration of SPIO was 50μg/mL, the highest labeling rate of Prussian blue staining was 90%, the growth state of labeled EPCs were good, and could normal adherent growth and passage. At this time, the cell viability and proliferation activity were the highest through trypan blue staining and MTT assay. ConclusionsEPCs can be labeled with SPIO easily and efficiently when the concentration was 50μg/mL?without interference on the viability and proliferation activity, which lay the foundations for the further EPCs tracer study in vivo.