Bone marrow derived mesenchymal stem cell (BM MSC) application in articular cartilage repair 6

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Figure 3-19. Prussian blue staining of the iron labeled MSCs in the
surgical scar site.
Prussian blue staining was used to detect the presence of the iron labeled
MSCs in the surgical scar site. The iron particles in the cells were visualized
as the blue dots in the cells.

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Figure 3-20. Prussian blue staining of iron labeled MSCs in the para-
patellar fat.
Prussian blue staining was used to detect the presence of the iron labeled
MSCs in the para-patellar fat. The iron particles in the cells were visualized as
the blue dots.

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3.5 Discussion
Several other groups have investigated the effects of the SPIO labeling of
MSC using different transfection approaches (200-203). These studies
reported controversial results especially on chondrogenic differentiation.
Farrell et al. (204) showed that SPIO labeled cells negatively affected the
osteogenic differentiation of the cells in vivo. In contrast, our study showed
that iron labeling did not affect the adipogenic and osteogenic potential of
MSCs in vitro but could negatively affect viability and chondrogenic
differentiation of the labeled cells at higher concentrations. Our results are in
agreement with those of Kostura et al. (192), but not with those of Heymer et
al. (205) and Arbab et al. (189). This difference could be the result of lower

loading of the cells (5 pg iron per cell) by Heymer et al., which is similar to our
cells iron content labeled with lower labeling concentration (25–50 µg/mL).
Hence, an optimized and controlled labeling concentration of MSCs can
reduce the adverse effects of the iron particles.
Our results showed, after optimized labeling, that visualization of injected
MSCs is indeed feasible in vivo. Cells migration and localization into different
site of the inflammation was observed in the knee joint over time. A majority of
the cells moved to the surgery sites such as surgery scar, para-patellar fat
and injection site, confirming the report of Jing et al. (206, 207). In addition,
our results showed that we could detect labeled cells in vivo up to 6 weeks,
thus the SPIO labeling method of the cells can be a promising tool for real
time evaluation and tracking of MSCs, providing data for a better
understanding of the migration and localization of the injected cells.