Vascular endothelial growth factor stimulates angiogenesis without improving collateral blood flow following hindlimb ischemia in rabbits

Abstract

This study was designed to test the ability of adenovirus-delivered vascular endothelial growth factor (Ad-VEGF) to stimulate angiogenesis and arteriogenesis in the rabbit hindlimb following the induction of ischemia and to evaluate the functional changes in the collateral circulation. Ten days after the surgical induction of hindlimb ischemia, either a control virus (1 x 10(9) pfu) or an adenovirus containing the gene for VEGF(165) (1 x 10(6), 1 x 10(7), 1 x 10(8), or 1 x 10(9) pfu) was administered intramuscularly into the ischemic limb. Thirty days after administration of the adenoviral vectors, skeletal muscle capillary density was assessed and angiography was performed as markers of angiogenesis and arteriogenesis, respectively. Hindlimb blood flow was directly measured and hyperemic tests were performed to evaluate the functional improvements in collateral blood flow. Animals treated with Ad-VEGF at 1 x 10(8) and 1 x 10(9) pfu showed elevated levels of circulating VEGF and dose-dependent hindlimb edema. These doses also led to a robust angiogenic response (i.e., increase in capillary density), but failed to improve collateral blood flow. Consistent with the lack of a functional response, there was no angiographic evidence of enhanced arteriogenesis with any dose of Ad-VEGF. Following the induction of hindlimb ischemia, administration of Ad-VEGF stimulated capillary sprouting (i.e., angiogenesis), but did not increase the growth and development of larger conduit vessels (i.e., arteriogenesis) or improve collateral blood flow. These results support the concept that VEGF may not be expected to have therapeutic utility for the treatment of peripheral or myocardial ischemia.

Angiogenesis is confined to the transient period of VEGF expression that follows adenoviral gene delivery to ischemic muscle

“…These kinetics are consistent with the known transient nature of gene expression following delivery with adenovirus and are similar to other reports of serum VEGF after gene delivery. 11,12 Serum VEGF did not increase in control ischemic animals, but tissue levels of the RNAs of both VEGF and metallothionein (a hypoxia-activated gene 13 ) increased at 8, 24, and 48 h after imposition of ischemia, determined by Northern blot analysis (data not shown).…”

“…In the latter study, Ad-lacZ also significantly stimulated capillary density and it is not clear whether the angiogenesis was attributed to VEGF or the consequences of viral infection. Hershey et al, 12 studying a lower dose of Ad-VEGF (1 Â 10 9 PFU) in the rabbit, confirmed an early transient VEGF expression and (a) Large artery density is determined by the number of pixels contained in a masked region common to all angiograms by reference to the femur; it corresponds to arteries with diameters 4250 mm (b). Peak image intensity quantifies the total amount of contrast that enters the large arteries and represents perfusion.…”

“…The latter observation is in contrast with a previous report that 1 Â 10 9 PFU of Ad-CMV-VEGF165 caused significant edema of the hindlimb. 12 We can only attribute this to differences in the animal models. Adenovirus was delivered directly into the adductor muscle in a total volume of 1 ml at eight injection sites on each side and distal to the excised region of the femoral artery.…”

Continuous occurrence of both insufficient neovascularization and elevated vascular permeability in rabbit proximal femur during inadequate repair of steroid‐associated osteonecrotic lesions

“…It has been suggested that angiogenesismediated neovascularization precedes osteogenesis (4), which is critical during osteonecrotic lesion repair (5). However, studies of the therapeutic efficacy of using angiogenic factor as a treatment to improve blood flow in ischemia models have been fraught with inconsistencies and even disappointment (6)(7)(8)(9). The exact vascular pathophysiologic mechanism during inadequate repair of steroid-associated osteonecrotic lesions remains unclear with regard to defining a therapeutic strategy, which requires systematic investigation of the events underlying vascular pathophysiology.…”

Human adipose-derived mesenchymal stem cell could participate in angiogenesis in a mouse model of acute hindlimb ischemia

“…Some of the VEGF forms bind to its receptor such as VEGF-R2 (Flk-1/KDR), which is expressed almost exclusively in the endothelial cells (Neufeld et al, 1999). By the interaction of VEGF and VEGF-R2, vascular permeability was induced (Clauss, 2000;Henry et al, 2003;Hershey et al, 2003). VEGF binding stimulated proliferation and decreased apoptosis of endothelial cells, leading to the increased efficiency of ischemic hindlimb treatment.…”