Efficiency of adenovirus-mediated gene transduction in heart grafts in rats

Construction of recombinant adenovirus vector containing a modified gene that codes for human hypoxia-inducible factor-1alpha without oxygen-dependent degradation domain

The expression of hypoxia-inducible factor-1alpha (HIF-1alpha) in heart allografts is an important mechanism in response to ischemia/reperfusion (I/R) injury which represents the single major non-immunologic factor implicated in pathogenesis of chronic graft dysfunction (CGD). Adenoviral mediated overexpression of HIF-1alpha is a useful way to investigate the molecular mechanisms of I/R injury and the cardiac function during heart transplantation. The oxygen-dependent degradation (ODD) domain of HIF-1alpha can lead to degradation of the HIF-1alpha protein in normoxia. This will be an obstacle to steady expression of HIF-1alpha in heart allograft after transduction. In this study, we obtained the coding sequence of HIF-1alpha without ODD domain (HIF-1alphaDeltaODD) through a PCR-based method, and then generated the HIF-1alphaDeltaODD-expressing adenovirus. In normoxia, adenoviral mediated expression of HIF-1alphaDeltaODD shows constitutive activity in human cardiomyocytes, and can up-regulate heme oxygenase (HO)-1 mRNA levels significantly compared with the group transduced with HIF-1alpha-expressing adenovirus. The constructed HIF-1alphaDeltaODD-expressing adenovirus can be used to transduce allografts in animal studies to investigate the mechanism of CGD and provide a useful model to study the regulation mechanisms of genes regulated by HIF-1alpha alone.

Sodium iodide symporter (hNIS) permits molecular imaging of gene transduction in cardiac transplantation

BACKGROUND

We evaluated the feasibility of noninvasive micro-single photon emission computed tomography (SPECT)/computed tomography (CT) imaging and quantification of cardiac gene expression after sodium iodide symporter (hNIS) gene transfer in cardiac transplantation.

METHODS

Donor rat hearts were perfused ex vivo with adenovirus expressing hNIS (Ad-hNIS), Ad-Null, or University of Wisconsin (UW) solution prior to heterotopic transplantation into syngeneic recipients. In the first group of recipients, imaging of the transplanted hearts with micro-SPECT/CT on day 5 was followed by immediate explant of the organs for ex vivo analyses. Radioactivity counts in the explanted hearts were obtained ex vivo and expressed as a percentage of the injected dose per gram of tissue (%ID/g). Intensities of the SPECT images of the transplanted hearts were quantified and converted to radioactive counts using a standard equation. The second group of recipients was imaged sequentially after injection of I on days 2 to 14 after transplantation.

RESULTS

Higher ex vivo radioiodine counts were noted in the hearts perfused with Ad-hNIS (1.04+/-0.2) compared to either the UW group (0.31+/-0.11, P<0.001) or the Ad-Null group (0.32+/-0.08, P<0.001). Image intensity in the Ad-NIS group (0.9+/-0.2) was also significantly higher than in the UW group (0.4+/-.03, P=0.003) or the Ad-Null group (0.5+/-0.1, P<0.05). Sequential imaging of Ad-NIS-perfused hearts between postoperative days 2 and 14 revealed peak image intensity at day 5. Overall, image intensities correlated with ex vivo counts of radioactivity (rho=0.74, P<0.05).

CONCLUSIONS

These data demonstrate that hNIS gene transfer permits sequential real-time detection and quantification of reporter gene expression in the transplanted heart with micro-SPECT/CT imaging.