Abstract
Background aims. Mesenchymal stromal cells (MSC) are the focus of research in regenerative medicine aiming at the regulatory approval of these cells for specific indications. To cope with the regulatory requirements for somatic cell therapy, novel approaches that do not interfere with the natural behavior of the cells are necessary. In this context in vivo magnetic resonance imaging (MRI) of labeled MSC could be an appropriate tool. Cell labeling for MRI with a variety of different iron oxide preparations is frequently published. However, most publications lack a comprehensive assessment of the non-interference of the contrast agent with the functionality of the labeled MSC, which is a prerequisite for the validity of cell-tracking via MRI. Methods. We studied the effects of iron oxide–poly(l-lactide) nanoparticles in MSC with flow cytometry, transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM), Prussian blue staining, CyQuant® proliferation testing, colony-forming unit–fibroblast (CFU-F) assays, flow chamber adhesion testing, immunologic tests and differentiation tests. Furthermore iron-labeled MSC were studied by MRI in agarose phantoms and Wistar rats. Results. It could be demonstrated that MSC show rapid uptake of nanoparticles and long-lasting intracellular persistence in the endosomal compartment. Labeling of the MSC with these particles has no influence on viability, differentiation, clonogenicity, proliferation, adhesion, phenotype and immunosuppressive properties. They show excellent MRI properties in agarose phantoms and after subcutaneous implantation in rats over several weeks. Conclusions. These particles qualify for studying MSC homing and trafficking via MRI.
Acknowledgments
The authors thank Julia Dausend, Sonu Sharma, Karin Fuchs, Gisela Baur, Ariane Bruche, Uschi Maile, Marion Tomo, Victoria Lang, Johannes Schmid and Thomas Becker for their technical support, and PD Dr Henschler for the review of the manuscript and for guidance and supervision of the adhesion testing.
This work was supported by a grant from the 7th Framework Program of the European Commission: CASCADE (Cultivated Adult Stem Cells as Alternative for Damaged Tissue) (number 223236; HEALTH-F5-2009-223236) and REBORNE (REgenerating BOne defects using New biomedical Engineering approaches) (number HEALTH-2009-1.4.2-241879).
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.