Capillary enlargement, not sprouting angiogenesis, determines beneficial therapeutic effects and side effects of angiogenic gene therapy.
OBJECTIVE
Currently, it is still unclear which mechanisms drive metabolic benefits after angiogenic gene therapy. The side-effect profile of efficient angiogenic gene therapy is also currently incompletely understood. In this study, the effects of increasing doses of adenoviral (Ad) vascular endothelial growth factor-A (VEGF-A) were evaluated on vascular growth, metabolic benefits, and systemic side effects.


RESULTS
Adenoviral vascular endothelial growth factor-A or AdLacZ control was injected intramuscularly (10(9)-10(11) vp/mL) or intra-arterially (5 × 10(11) vp/mL) into rabbit (n = 102) hindlimb muscles and examined 6 or 14 days later. Blood flow, tissue oedema, metabolic benefits, and the structure of angiogenic vessels were assessed using ultrasound imaging, modified Miles assay, arterial blood gas and metabolite analyses, and light and confocal microscopy, respectively. Safety analyses included cardiac ultrasound, electrocardiograms, and blood and tissue samples. Sprouting angiogenesis was already induced with low AdVEGF-A concentrations, whereas higher concentrations were needed to reach efficient capillary enlargement and increases in target muscle perfusion. Interestingly, metabolic benefits, such as improved aerobic energy metabolism and decreased metabolic acidosis during exercise, after AdVEGF-A administration were highly correlated to the level of capillary enlargement but not to sprouting angiogenesis. Several systemic dose-dependent side effects, including transient increases in liver, kidney, and pancreatic enzymes, and signs of cardiac effects were observed.


CONCLUSIONS
Efficient capillary enlargement leading to significant increases in tissue perfusion is needed to gain metabolic benefits after angiogenic gene therapy. However, the risk of systemic side effects can increase as the efficiency of angiogenic gene therapy is improved. Importantly, the unstable wall structure of the newly formed vessels seems not to compromise the metabolic benefits.
Department of Molecular Medicine, A.I. Virtanen Institute, University of Eastern-Finland, Kuopio, Finland.
Petra
P
Korpisalo
Jarkko P
JP
Hytönen
Johannes T T
JT
Laitinen
Svetlana
S
Laidinen
Henna
H
Parviainen
Henna
H
Karvinen
Jaana
J
Siponen
Varpu
V
Marjomäki
Ismo
I
Vajanto
Tuomas T
TT
Rissanen
Seppo
S
Ylä-Herttuala
D000256:Adenoviridae; D000818:Animals; D002196:Capillaries / Q000033:anatomy & histology*; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000009:adverse effects / Q000379:methods*; D005822:Genetic Vectors; D006614:Hindlimb; D007273:Injections, Intramuscular; D007763:Lac Operon / Q000235:genetics; D018482:Muscle, Skeletal / Q000098:blood supply*; D018919:Neovascularization, Physiologic; D011817:Rabbits; D018084:Ultrasonography, Interventional; D042461:Vascular Endothelial Growth Factor A / Q000008:administration & dosage* / Q000009:adverse effects
D042461:Vascular Endothelial Growth Factor A