A pilot study on in vivo MRI tracking of magnetically labeled dendritic cells homing to the draining lymph nodes

Abstract:

Objective：To track homing of magnetically-laden dendritic cells（DCs） into the draining lymph nodes using magnetic reso－nance（MR） imaging. Methods：Mature DCs generated from murine bone marrow cells were labeled with a laboratorially-synthesized alkylated-polyethyleneimine（PEI2k） coated superparamagnetic ironoxide（SPIO） nanoparticle. Perl’s staining，confocal laser scanning microscopy（CLSM），and fluorescence activated cell sorting（FACS） were followed to analyze labeling results and expression of mature phenotype，respectively. For in vivo MR imaging，gradient amount of DCs were subcutaneously injected into the footpads of three mice. MR scanning was performed at different time points. At 72 h after injection，mice were sacrificed to extract the popliteal lymph nodes for pathological examination. Results：A final purity of about 90% DC was achieved by this culture method. Probes located in cyto－plasm after overnight labeling，as evidenced by Perl’s staining and CLSM. Labeling process did not impact obviously on the maturation phenotypes of DCs. Both MRI and pathological studies documented the successful migration of labeled DCs into popliteal nodes. Conclusion：It is feasible to utilize MR imaging to track the in vivo migration of DCs labeled with N-alkyl-PEI2k/SPIO nanoprobe.