Noninvasive imaging of ex vivo intracoronarily delivered nonviral therapeutic transgene expression in heart

We developed a clinically applicable approach for noninvasive monitoring of reporter-therapeutic linked gene expression in the whole heart of large animals using PET imaging and further validated the efficacy and cardiac adverse effects of reporter-therapeutic linked gene transfer in a rabbit cervical heterotopic functional heart transplant model. Cationic liposome complexed with a vector containing a herpes simplex virus type I mutant thymidine kinase (HSVI-sr39tk) as the reporter gene and a recombinant human immunosuppressive cytokine, interleukin-10 (hIL-10), as the therapeutic gene was ex vivo intracoronarily delivered into cardiac allografts before implantation. Long-term HSV1-sr39tk and hIL-10 transgene and protein overexpression associated with myocardial PET reporter probe 9-(4-[F-18]fluoro-3-hydroxymethylbutyl)guanine ([F-18]FHBG) accumulation was observed in the allografts. The expression of the HSVI-sr39tk gene was significantly correlated with the hIL-10 gene expression and the total myocardial [F-18]FHBG accumulation quantified as a percentage of intravenously injected [F-18]FHBG dose. A homogeneous distribution of [F-18]FHBG accumulation was seen in the whole heart similar to the distribution of [F-18]fluorodeoxyglucose, a PET glucose metabolism probe. The immunosuppressive therapeutic efficacy remained the same in allografts treated with reporter-therapeutic linked gene and therapeutic gene only. No cardiac adverse effect was found. Our results demonstrate for the first time that PET reporter-therapeutic linked gene imaging is applicable for noninvasively monitoring ex vivo intracoronarily delivered therapeutic transgene expression in the whole heart.