Assessment of the Differentiation Potential of Rat Adult Mesenchymal Stem Cells after Labeling with MR Contrast Agents

Background and Aims: Adult mesenchymal stem cells (MSC) are the focus of research in the emerging field of regenerative medicine due to their somatic and visceral differentiation potential. Using MRI for tracking labeled cells is a very promising technique for the non-invasive monitoring of their fate. The aim of our study was to evaluate whether small or ultrasmall particles of iron oxide (U)SPIO might interfere in the differentiation potential and thus influence the plasticity of MSC. Materials and Methods: Adult MSC were isolated from the bone marrow of rats, cloned and propagated. Cells in P12 were labeled with 200 mu g/ml (U)SPIO (Resovist registered /Resovist C) for 15 hours or with 60 mu g/ml (U)SPIO in combination with the transfection agents (TAs) Dosper registered or jetPEI for four hours. MSC were characterized by osteogenic, adipogenic and chondrogenic in vitro differentiation after labeling without TAs. Surface protein expression was analyzed by FACS. Spectrophotometrically quantification of the cellular iron content and determination of the cellular viability were performed additionally. Results: Labeling of MSC with (U)SPIO was feasible without affecting cell viability or their osteogenic, adipogenic or chondrogenic differentiation potential. Surface protein staining was negative for CD4, CD11b, CD31, CD45, CD106, CD117, and positive for CD29, CD59 and CD90. TAs augmented the iron content of the cells, and, in particular, jetPEI was very effective. Conclusions: (U)SPIO labeling of raMSC for 15 hours does not alter the differentiation potential of the cells, although being in a high in vitro cultivation passage. Contradictory to recent publications, we could not detect interference between (U)SPIO labeling and chondrogenic differentiation potential.