Figure 6.

Example of Reporter Gene Integration to Enable Non-invasive Monitoring of Stem Cell-Mediated Teratoma Formation by In Vivo Imaging

Human ESCs were lentivirally modified to express the HSV1-tk radionuclide reporter gene fused to enhanced GFP, and 2–5 × 10⁶ reporter expressing hESCs were injected intramuscularly and tracked in vivo by whole-body SPECT/CT imaging. Yellow arrows/rings indicate tumors. (A and B) Representative planar (A) γ and (B) SPECT/CT images of tumors derived in an animal scanned 87 days after tumor inoculation (when a palpable tumor was detected). The radiotracer [¹²⁵I]FIAU was intravenously (i.v.) administered and the animal was scanned 24 h later. (C) Longitudinal SPECT/CT imaging of a different SCID (severe combined immunodeficiency)-beige mouse harboring a teratoma from reporter-expressing hESCs. This mouse was serially imaged at the indicated time points post inoculation. All data were quantitatively analyzed in the study. For details the reader is referred to the original work¹⁹⁹. [Figure reproduced with minor modification from the cited work.]