Monitoring the Bystander Killing Effect of Human Multipotent Stem Cells for Treatment of Malignant Brain Tumors

Figure 8

Follow-up of suicide gene therapy using hMultistem as cellular vehicles in the hU87 glioma model by using multimodal in vivo imaging and histology. (a) MR images of a representative animal from the sham, PBS, and GCV treated groups show a comparable tumor growth prior to hMultistem injection on T₂-weighted MR images (upper row for each group). While there is little hypointense contrast visible on 3D -weighted MR images (lower row for each group), the distribution of SPIO labeled hMultistem cells could clearly be detected due to their hypointense contrast in the PBS and GCV treated group (one day after engraftment). The contrast distribution changed only very little until the end of treatment. When tumors grew larger, the hypointense voxels got more dispersed over time. (b) Left: bioluminescent imaging using D-luciferin as a substrate for fLuc expressing hMultistem cells. Stem cells were detectable after engraftment but not after the end of treatment for both, the PBS and GCV receiving groups. Right: bioluminescence imaging using coelenterazine-h as a substrate for rLuc expressing hU87 tumor cells. The signal intensity increased for the sham and PBS group but not for the GCV group, indicating some inhibition of tumor growth. (c) Two weeks after the end of therapy, animals developed symptoms after which histological analysis was performed. Masson’s trichrome staining (upper left) of all animals showed large, dense tumors. Prussian blue (upper right) staining was also performed which confirmed the presence of iron in PBS and GCV treated animals. Finally, Iba1 staining (bottom) was performed which showed a predominant absence of activated microglia in all treatment groups.

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