Abstract 9306: Site-Specific Reporter Gene Imaging of Stem Cell Transplantation: Early Engraftment Predicts Late Improvement in Cardiac Function
Stable genetic modification of cardiac progenitor cells (CPCs) enables quantitative assessment of their engraftment and proliferation using reporter gene imaging. However, random lentiviral integration techniques carry the concomitant risk of introducing inadvertent mutations, including the unacceptable risk of proto-oncogene activation. Here, we demonstrate a safe, clinically applicable method for site-specific PET reporter gene imaging of transplanted CPCs. A triple fusion reporter gene was integrated specifically into chromosome 19 of Sca-1+ human CPCs using the ΦC31 integrase. Targeted integration into this genomic locus was confirmed using nested PCR and Southern blotting. Stably-integrated CPCs (1×106) were then transplanted into ischemic murine myocardium (n=40), and monitored noninvasively using PET, bioluminescence, cardiac MR, and echocardiography for four weeks. hCPC-treated hearts demonstrated a statistically significant improvement in fractional shortening (27.2±2.3% vs. 21.5±1.4%; P=0.04) as well as ejection fraction (48.3±2.6% vs. 42.2±1.7%; P=0.03) at day 14 post-transplant compared to PBS controls, as assessed by echocardiography and cardiac MRI, respectively. Initial PET signal intensity, as a surrogate marker of cellular engraftment, predicted the degree of functional improvement at week 2 (R2=0.73) in a “dose-effect” relationship. To investigate the mechanism of hCPC benefit on myocardial function, we isolated the transplanted cells from recipient myocardium by laser capture microdissection and found direct evidence for upregulated expression of the VEGF-α and CTGF pro-angiogenic growth factors in vivo. Here, we demonstrate the first use of site-specific reporter gene imaging to enable prognostic prediction of the ultimate success of CPC therapy. Given the encouraging but variable results of recent cell therapy trials, our results provide valuable insight into the determinants of successful cell therapy.
- © 2011 by American Heart Association, Inc.