OBJECTIVETo perform in vitro magnetic resonance imaging on magnetic iron oxide (Fe(2)O(3)-PLL) labeled rabbit peripheral blood endothelial progenitor cells (EPCs).

METHODSFe(2)O(3) was incubated with PLL for 2 hours to form Fe(2)O(3)-PLL. Rabbit peripheral blood mononuclear cells (MNCs) were isolated and EPCs were selected by adherence method, expanded and incubated with Fe(2)O(3)-PLL. Intracellular iron was detected by Prussian blue stain and under electron microscope. MTT assay was used to evaluate cell survival and proliferation of Fe(2)O(3)-PLL labeled EPCs. Flow cytometry was used to analysis cell cycle and apoptosis. The cells underwent in vitro MR imaging with various sequences.

RESULTSIron-containing intracytoplasmatic vesicles could be observed clearly with Prussian blue staining and electron microscope observation. Survival, life cycle and apoptosis values obtained by MTT and flow cytometry analysis were similar among unlabelled EPCs and EPCs labeled with various concentrations Fe(2)O(3)-PLL. The signal intensity on MRI was significantly decreased in labeled cells compared with that in unlabeled cells. The percentage change in signal intensity (DeltaSI) was most significant on T(2)*WI and DeltaSI was significantly lower in cells labeled for 7 days than that labeled for 1 day.

CONCLUSIONSThe rabbit peripheral blood EPCs can be labeled with Fe(2)O(3)-PLL without significant change in viability and proliferation. The labeled EPCs can be imaged with standard 1.5 T MR equipment. The degree of MR signal decreasing may indirectly reflect the cells count, growth state and division.