Adeno-associated virus mediated gene delivery into coronary microvessels of chronically instrumented dogs

A CMV-actin-globin hybrid promoter improves adeno-associated viral vector gene expression in the arterial wallin vivo

BACKGROUND

Adeno-associated virus (AAV) vectors are attractive tools for direct intralumenal arterial gene transfer in interventional cardiology or cardiovascular surgery, but clinical application has been constrained by poor gene expression in this setting.

METHODS

To improve arterial wall gene expression, a hybrid promoter consisting of a cytomegalovirus (CMV) immediate-early enhancer, a chicken beta-actin transcription start site, and a rabbit beta-globin intron (CAG promoter) was substituted for the Rous sarcoma virus (RSV) promoter in an AAV type 2 vector with an alkaline phosphatase (AP) reporter gene.

RESULTS

Intralumenal transduction of rabbit carotid arteries by an AAV2 vector containing a CAG promoter resulted in gene expression in a mean of > or = 80% of the lumenal area at 14 days following exposure, compared to < or = 25% gene-expressing area with the RSV promoter-based control vector. The high prevalence of gene expression was maintained at 3, 7, 14, and 28 days. Importantly, in carotid arteries transduced with the CAG promoter, gene product expression was readily visible by the third day following transduction whereas gene expression was rarely seen before day 10 using the RSV promoter in the same animal model. On histology, AP gene expression was predominantly in vascular smooth muscle cells although some endothelial cell expression was also present.

CONCLUSIONS

Substituting the CAG for the RSV promoter results in widespread gene expression, demonstrating efficient arterial wall transduction by AAV2 vectors. This finding plus the early time to gene expression hold promise for AAV vectors as agents for direct intralumenal arterial wall gene delivery during cardiovascular interventions.

Endothelial nitric oxide synthase gene transfer restores endothelium-dependent relaxations and attenuates lesion formation in carotid arteries in apolipoprotein E-deficient mice

Nitric oxide (NO) and monocyte chemoattractant protein-1 (MCP-1) exert partly opposing effects in vascular biology. NO plays pleiotropic vasoprotective roles including vasodilation and inhibition of platelet aggregation, smooth muscle cell proliferation, and endothelial monocyte adhesion, the last effect being mediated by MCP-1 downregulation. Early stages of arteriosclerosis are associated with reduced NO bioactivity and enhanced MCP-1 expression. We have evaluated adenovirus-mediated gene transfer of human endothelial NO synthase (eNOS) and of a N-terminal deletion (8ND) mutant of the MCP-1 gene that acts as a MCP-1 inhibitor in arteriosclerosis-prone, apolipoprotein E-deficient (ApoE(-/-)) mice. Endothelium-dependent relaxations were impaired in carotid arteries instilled with a noncoding adenoviral vector but were restored by eNOS gene transfer (p < 0.01). A perivascular collar was placed around the common carotid artery to accelerate lesion formation. eNOS gene transfer reduced lesion surface areas, intima/media ratios, and macrophage contents in the media at 5-week follow-up (p < 0.05). In contrast, 8ND-MCP-1 gene transfer did not prevent lesion formation. In conclusion, eNOS gene transfer restores endothelium-dependent vasodilation and inhibits lesion formation in ApoE(-/-) mouse carotids. Further studies are needed to assess whether vasoprotection is maintained at later disease stages and to evaluate the long-term efficacy of eNOS gene therapy for primary arteriosclerosis.