nan Mehta

Long-term increase in uterine blood flow is achieved by local overexpression of VEGF-A 165 in the uterine arteries of pregnant sheep

Increasing uterine artery blood flow (UABF) may benefit fetal growth restriction where impaired uteroplacental perfusion prevails. Based on previous short-term results, we examined the long-term effects of adenovirus vector-mediated overexpression of vascular endothelial growth factor-A165 (VEGF-A165) in the uterine artery (UtA). Transit-time flow probes were implanted around both UtAs of mid-gestation pregnant sheep (n=11) to measure UABF. A carotid artery catheter was inserted to measure maternal or fetal hemodynamics. Baseline UABF was measured over 3 days, before injection of adenovirus vector (5 × 1011 particles) encoding the VEGF-A165 gene (Ad.VEGF-A165) into one UtA and a reporter β-galactosidase gene (Ad.LacZ) contralaterally. UABF was then measured daily until term. At 4 weeks post injection, the increase in UABF was significantly higher in Ad.VEGF-A165 compared with Ad.LacZ-transduced UtAs (36.53% vs 20.08%, P=0.02). There was no significant effect on maternal and fetal blood pressure. Organ bath studies showed significantly lesser vasoconstriction (Emax 154.1 vs 184.7, P<0.001), whereas immunohistochemistry demonstrated a significantly increased number of adventitial blood vessels (140 vs 91, n=26, P<0.05) following Ad.VEGF-A165 transduction. Local overexpression of VEGF-A165 in the UtAs of pregnant mid-gestation sheep leads to a sustained long-term increase in UABF, which may be explained by neovascularization and altered vascular reactivity.

THE EFFECTS OF LOCAL OVER-EXPRESSION OF VEGF ON THE UTERINE ARTERIES AND UTERINE ARTERY ENDOTHELIAL CELLS OF PREGNANT SHEEP

Introduction Impaired utero-placental perfusion leads to fetal growth restriction. The authors have shown a significant increase in blood flow in the uterine arteries (UAs) of pregnant sheep and a significantly reduced contractile response following local transduction with an adenovirus encoding VEGF-A165 (Ad.VEGF-A). The authors have now studied the effects of local over-expression of the VEGF-DΔNΔC isoform and investigated the mechanism behind the VEGF (−A and −DΔNΔC) induced effects. Method UAs of mid-gestation pregnant sheep were injected with adenovirus vectors (5×1011 particles) encoding the VEGF-DΔNΔC gene (Ad.VEGF-D) and a reporter β-galactosidase gene (Ad.LacZ) contra-laterally. Sheep were killed 4–7 days later. UAs were isolated and their vasoreactivity studied on an organ bath. Adventitial blood vessels were enumerated by anti-vWF immunohistochemistry. Endothelial cells (ECs) were isolated from the UAs of control mid-gestation pregnant sheep, cultured and infected with Ad.VEGF-A vector. Protein was extracted from these uterine artery endothelial cells (UAECs) infected ex vivo and assayed for endothelial nitric oxide synthase (eNOS) levels by Western blotting. Results There was a significant reduction in the UA contractile response following Ad.VEGF-D when compared to Ad.LacZ transduction (Emax 126.6±7.54 vs 159.9±10.96, p<0.001, n=5) and vasorelaxation was enhanced (pD2 (−log EC50) 9.05±0.14 vs 8.87±0.16, p=0.55, n=4). eNOS levels increased with rising adenovirus vector concentrations in UAECs transduced ex vivo. There were significantly higher numbers of blood vessels in the perivascular adventitia of Ad.VEGF-D transduced vessels compared to Ad.LacZ transduced vessels (140.6±15.1 vs 91.7±9.9, p<0.05). Conclusion Changes in eNOS levels and vascular remodeling may be the underlying mechanism of action of local VEGF over-expression in pregnant sheep UAs.