Angiogenesis is the process by which new blood vessels are formed from existing vessels. The vascular endothelial growth factors (VEGFs) are considered as key molecules in the process of angiogenesis. The VEGF family currently includes VEGF-

Background-Neointimal vascular smooth muscle cell (VSMC) proliferation is a primary cause of occlusive vascular disease, including atherosclerosis, restenosis after percutaneous interventions, and bypass graft stenosis. Angiogenesis is implicated in the progression of early atheromatous lesions in animal models, but its role in neointimal VSMC proliferation is undefined. Because percutaneous coronary interventions result in induction of periadventitial angiogenesis, we analyzed the role of this process in neointima formation. Methods and Results-Local injury to the arterial wall in 2 different animal models induced periadventitial angiogenesis and neointima formation. Application of angiogenesis stimulators vascular endothelial growth factor (VEGF-A 165 ) or a proline/arginine-rich peptide (PR39) to the adventitia of the injured artery induced a marked increase in neointimal thickening beyond that seen with injury alone in both in vivo models. Inhibition of either VEGF (with soluble VEGF receptor 1 [sFlt1]) or fibroblast growth factor (FGF) (with a dominantϭnegative form of FGF receptor 1 [FGF-R1DN]), respectively, signaling reduced adventitial thickening induced by VEGF and PR39 to the level seen with mechanical arterial injury alone. However, neither inhibitor was effective in preventing neointimal thickening after mechanical injury when administered in the absence of angiogenic growth factor. Conclusions-Our findings indicate that adventitial angiogenesis stimulates intimal thickening but does not initiate it.

Significant differences were observed between the AAV and the Adv vectors in their patterns of arterial transduction and consequent inflammatory responses. These distinct properties may be utilized for different applications in vascular biology research and gene therapy for cardiovascular diseases.

Recent discovery of new members of the vascular endothelial growth factor (VEGF) family has generated much interest as to which members may be best suited for therapeutic angiogenesis in various tissues. In this study we evaluated angiogenic responses of the different members of the VEGF family in vivo using adenoviral gene transfer. Adenoviruses (1 x 10(9) plaque-forming units [pfu]) encoding for VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGF-C(deltaNdeltaC) and VEGF-D(deltaNdeltaC) (deltaNdeltaC are proteolytically cleaved forms) were transferred locally to the periadventitial space of the rabbit carotid arteries using a collar technique that allows efficient local transfection of the periadventitial tissue. Expression of the transfected VEGFs was confirmed by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). Seven days after the gene transfer maximum neovessel formation was observed in VEGF-A-, VEGF-D-, and VEGF-D(deltaNdeltaC)-transfected arteries. VEGF-C(deltaNdeltaC) also showed angiogenic activity whereas VEGF-B was not effective in inducing angiogenesis. Pericytes were detected around the neovessels, which also frequently showed the presence of intraluminal erythrocytes. Infiltration of inflammatory cells in response to VEGF-D and VEGF-D(deltaNdeltaC) was less prominent than that caused by other VEGFs. In line with the absence of lymphatics in the normal carotid arteries no significant evidence of lymphatic vessel formation was seen in response to any of the studied VEGFs in the periadventitial space. The results help to define possibilities for local angiogenic therapy around blood vessels and support the concept that angiogenic effects may be tissue-specific and depend both on the growth factor ligands and the target tissues. It is concluded that VEGF-A, VEGF-D, and VEGF-D(deltaNdeltaC) are the best candidates for therapeutic angiogenesis when delivered around large arteries.

Adventitial delivery of adenoviruses encoding VEGF-A, VEGF-D and VEGF-D(DeltaNDeltaC) increased intimal hyperplasia in the rabbit collar model. Adventitial angiogenesis correlated positively with the intimal hyperplasia. These results indicated that efficient adventitial production of VEGF-A, VEGF-D and VEGF-D(DeltaNDeltaC) can cause thickening of the inner layer of the artery in rabbits.