Biologic bypass with the use of adenovirus-mediated gene transfer of the complementary deoxyribonucleic acid for vascular endothelial growth factor 121 improves myocardial perfusion and function in the ischemic porcine heart

Abstract

Objectives: Vascular endothelial growth factor (VEGF), a potent angiogenic mediator, can be delivered to targeted tissues by means of a replication-deficient adenovirus (Ad) vector. We hypothesized that direct administration of Ad vector expressing the VEGF121 complementary deoxyribonucleic acid (AdGVVEGF121.10) into regions of ischemic myocardium would enhance collateral vessel formation and improve regional perfusion and function.

Methods: Yorkshire swine underwent thoracotomy and placement of an Ameroid constrictor (Research Instruments & MFG, Corvallis, Ore.) on the circumflex coronary artery. Three weeks later, myocardial perfusion and function were assessed by single photon emission computed tomography imaging (SPECT) with 99mTc-labeled sestamibi and by echocardiography during rest and stress. AdGVVEGF121.10 (n = 7) or the control vector, AdNull (n = 8), was administered directly into the myocardium at 10 sites in the circumflex distribution (10(8) pfu/site). Four weeks later, these studies were repeated and ex vivo angiography was performed.

Results: SPECT imaging 4 weeks after vector administration demonstrated significant reduction in the ischemic area at stress in AdGVVEFG121.10-treated animals compared with AdNull control animals (p = 0.005). Stress echocardiography at the same time demonstrated improved segmental wall thickening in AdGVVEGF121.10 animals compared with AdNull control animals (p = 0.03), with AdGVVEGF121.10 animals showing nearly normalized function in the circumflex distribution. Collateral vessel development assessed by angiography was also significantly greater in AdGVVEGF121.10 animals than in AdNull control animals (p = 0.04), with almost complete reconstitution of circumflex filling in AdGVVEGF121.10 animals.

Conclusions: An Ad vector expressing the VEGF121 cDNA induces collateral vessel development in ischemic myocardium and results in significant improvement in both myocardial perfusion and function. Such a strategy may be useful in patients with ischemic heart disease in whom complete revascularization is not possible.

Fig. 1.

Schema of the experimental design. Three weeks after Ameroid constrictor placement, animals were administered either Ad_GVVEGF121.10 (n = 7) or the control vector AdNull (n = 8) at 10 sites (10⁸ pfu/site) distributed throughout the left ventricular region between the circumflex and left anterior descending coronary arteries, as indicated.

Fig. 2.

Quantitative assessment of regional stress-induced myocardial ischemia with ^99mTc-labeled sestamibi SPECT imaging. A, Schema of method using circumferential count profiles. Short-axis ^99mTc-sestamibi images at the midventricular level were analyzed as described in the Methods section. The extent and severity (area) of myocardial ischemia was determined from the difference between the rest and stress circumferential count profile curves. The greatest severity of ischemia (ischemia maximum) in the circumflex distribution was determined as the greatest difference between the rest and stress circumferential count profiles. B, Representative circumferential count profiles of an AdNull-treated animal at 3 weeks (at the time of vector administration) at rest (upper part of the panel) and stress (atrial pacing; at the lower part of the panel), showing a perfusion defect in the posterolateral region. C, Same animal as in panel B, but at 7 weeks. There is minimal decrease in area of ischemia and ischemia maximum compared with 3 weeks. D, Representative circumferential count profiles of an Ad_GVVEGF121-treated animal at 3 weeks (at the time of vector administration) at rest and stress (atrial pacing), showing a perfusion defect in the posterolateral region. E, Same animal as in panel D, but at 7 weeks; there is a marked decrease in both area of ischemia and ischemia maximum compared with observations at 3 weeks.

Fig. 2.

Quantitative assessment of regional stress-induced myocardial ischemia with ^99mTc-labeled sestamibi SPECT imaging. A, Schema of method using circumferential count profiles. Short-axis ^99mTc-sestamibi images at the midventricular level were analyzed as described in the Methods section. The extent and severity (area) of myocardial ischemia was determined from the difference between the rest and stress circumferential count profile curves. The greatest severity of ischemia (ischemia maximum) in the circumflex distribution was determined as the greatest difference between the rest and stress circumferential count profiles. B, Representative circumferential count profiles of an AdNull-treated animal at 3 weeks (at the time of vector administration) at rest (upper part of the panel) and stress (atrial pacing; at the lower part of the panel), showing a perfusion defect in the posterolateral region. C, Same animal as in panel B, but at 7 weeks. There is minimal decrease in area of ischemia and ischemia maximum compared with 3 weeks. D, Representative circumferential count profiles of an Ad_GVVEGF121-treated animal at 3 weeks (at the time of vector administration) at rest and stress (atrial pacing), showing a perfusion defect in the posterolateral region. E, Same animal as in panel D, but at 7 weeks; there is a marked decrease in both area of ischemia and ischemia maximum compared with observations at 3 weeks.

Fig. 3.

Representative ex vivo angiograms of pig hearts 7 weeks after placement of Ameroid constrictors. The vectors were administered 3 weeks after placement of the Ameroid constrictor. A, AdNull. B and C, Ad_GVVEGF121.10 (referred to as AdVEGF121). The Ameroid constrictor completely occludes the circumflex artery in both the AdNull and AdVEGF121-treated animals. The AdNull-treated animal demonstrates only minimal filling of the distal circumflex artery. In contrast, the AdVEGF121-treated animals show nearly complete reconstitution of the circumflex artery.