In vitro labeling of mesenchymal stem cells with superparamagnetic iron oxide by means of microbubble-enhanced US exposure: initial experience.

Purpose: To investigate the feasibility of magnetically labeling stem cells with superparamagnetic iron oxide (SPIO) by means of microbubble-enhanced ultrasonographic (US) exposure (MUE) and to study the effects of this approach--without secondary transfection agents--on the viability, proliferation activity, and differentiation capability of MUE-labeled stem cells.

Materials And Methods: Institutional review board approval was obtained for this study. Human mesenchymal stem cells (MSCs) ([1 to 2] x 10(6)/mL) were studied in four experiment groups: sham exposure to US with microbubbles and SPIO (group A), exposure to US with SPIO but without microbubbles (group B), exposure to US with microbubbles and SPIO (group C), and sham exposure to US without SPIO or microbubbles (group D). Intracellular iron uptake was analyzed qualitatively at light and electron microscopy. The viability and proliferation activity of MSCs were evaluated. The adipogenic and osteogenic differentiation capability of the labeled MSCs was also evaluated. Ninety-five percent confidence intervals were derived for assessment of differences in cell viability and proliferation activity between groups C and D.

Results: Light and electron microscopy revealed intracytoplasmic iron uptake and nearly 100% cell labeling efficiency. The MUE-labeled MSCs had unaltered viability and uncompromised proliferation activity compared with the nonlabeled MSCs. Similar to the nonlabeled MSCs, the MUE-labeled MSCs differentiated into adipogenic and osteogenic lineages.

Conclusion: Initial study results show that stem cells can be effectively labeled with SPIO by using MUE without secondary transfection agents and thus that MUE labeling is an appealing alternative cell-labeling approach that warrants investigation for intracellular magnetic labeling of stem cells.

Supplemental Material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.2531081974/-/DC1.