Magnetic labeling of endothelial progenitor cells and their magnetic resonance imaging in vitro

Abstract

Objective To explore the influence of ultra-small super-paramagnetic iron oxide (USPIO) on the biological activity of endothelial progenitor cells (EPCs) and optimize their MR imaging sequence in vitro. Methods EPCs were cultured and the USPIO particles were inducted as magnetic markers, with the concentration of 25 μg/mL. For different concentrations of cells (2×106/mL, 1×106/mL,5×105/mL and 2.5×10VmL) disposed by 100 μL 8% gelatin, the T2 map and T2* map sequences were used to measure the relaxation time and rate. Results Immunocytochemistry, acetylated low density lipoprotein staining marked with Dil and Ulex europaeus agglutinin Ⅰ staining marked with fluorescein demonstrated that these cells were EPCs. USPIO labeled EPCs efficiently, with (98.45 ±0.05)% positive rate of labeling on the 5th d, and trypan blue staining and MTT assay indicated that it had no significant effect on the stem cell growth and proliferation. The T2 map and T2* map sequences showed that the relaxation rates (R2 and R2*) were linearly related to the cell concentrations in vitro (r1=0.990,P1=0.010;r2=0.975 ,P2=0.025), and the slop of R2* was 3.58 times of the R2's. Conclusion USPIO can label the EPCs efficiently without changing the biological characteristics of cells. Both T2* map and T2 map sequences can test the signal changes with different concentrations of labeled cells, and the former is more sensitively than the later. Key words: Endothelial progenitor cell; Magnetic resonance imaging; Ultra-small super-paramagnetic iron oxide