Cell and gene therapy with reporter gene imaging in myocardial ischemia

Reporter gene/probe systems have proved to be reliable for monitoring gene/cell therapy. We sought to evaluate whether a reporter gene/probe system, namely the human estrogen receptor ligand binding domain (hERL)/16α-¹⁸F fluoro-17β-estradiol (¹⁸F-FES), could be used for monitoring vascular endothelial growth factor (VEGF) gene expression and response to bone marrow mesenchymal stem cell (MSCs) therapy in ischemic heart disease.

Reporter gene hERL and therapeutic gene VEGF165 were linked through internal ribosome entry site (IRES), and then the recombinant adenovirus vector Adenovirus 5-hERL-IRES-VEGF (Ad5-EIV) was constructed and transfected into MSCs, and named Ad5-EIV-MSCs. Rat myocardial infarction was induced by coronary arterial branch ligature, and Ad5-EIV-MSCs were transplanted by injection into the peripheral myocardium, while non-transfected MSCs transplantation used as controls. Fluorine-18-FDG micro-PET imaging was performed to confirm myocardial infarction 1 day after surgery. Fluorine-18-FES micro-PET/CT images were acquired 2 days after Ad5-EIV-MSCs transplantation. Myocardial specimens were obtained and stained with hematoxylin-eosin (H&E) staining to verify the myocardial infarction. The expression of estrogen receptor (ER) and VEGF was detected using immunohistochemistry (IHC).

Rat myocardial infarction models were successfully produced and confirmed by H&E staining. Images of ¹⁸F-FDG PET showed obvious reduced or absent uptake of ¹⁸F-FDG on the infarct myocardium, while uniform and well-distribution on the normal myocardium. ¹⁸F-FES micro-PET/CT showed the tracer notable accumulated in the apical region where Ad5-EIV-MSCs were injected with an uptake value of 0.38±0.09%ID/g, which was much higher than that of surrounding normal myocardium with nearly no uptake of ¹⁸F-FES (0.10±0.03%ID/g, n=5, P<0.05). In the group of non-transfected MSCs, the apical uptake was similar to that of normal myocardium. Immunohistochemistry studies demonstrated positive expression of both ER and VEGF in the involved region accompanied by active angiogenesis.

This study confirmed that hERL/¹⁸F-FES could be used as a reporter gene/probe system for monitoring gene and cell therapy in the ischemic heart disease.