OBJECTIVETo explore the feasibility of Single Fe(2)O(3)-PLL labeled mouse spleen-derived endothelial progenitor cells (EPCs) detection by 7.0T MR system.

METHODSMononuclear cells (MNCs) were isolated from mouse spleen by density gradient centrifugation and EPCs were obtained by the different adherence of cells.Immunocytochemistry and fluorescent staining were performed to identify EPCs. The EPCs were labeled with Fe(2)O(3)-PLL and the intracellular iron was identified with prussian blue staining. MTT assay was assessed to evaluate proliferation of Fe(2)O(3)-PLL labeled EPCs. The cells underwent MR imaging with different sequences.

RESULTSCultured in vitro, mouse spleen-derived MNCs resulted in EC-like morphology. These cells expressed EPCs-specific antigens, such as CD31, CD34 and vWF, and had the ability to incorporate ac-LDL and bind UEA-1. Between Fe(2)O(3)-PLL labeled EPCs and unlabeled cells, MTT value of light absorption had no statistical significant difference (day4 t = 2.81, day5 t = -1.87, day6 t = -0.298, day7 t = -0.115, all P > 0.05). The signal void induced by labeled single cell is 20.2 pixels in MSME sequence, and 20.2 pixels in 3D-FLASH sequence (t = 15.2, P < 0.05). Single cell could be detected by 7.0 T MR system.

CONCLUSIONMNCs isolated from mouse spleen can differentiate into endothelial cells in vitro and have the specific property of stem cells. The mouse spleen-derived EPCs can be labeled with Fe(2)O(3)-PLL efficiently. The labeled EPCs can be imaged as dispersed single cells.