Fetal growth restriction (FGR) is a common and potentially severe pregnancy complication. Currently there is no treatment available. The guinea pig is an attractive model of human pregnancy as placentation is morphologically very similar between the species. Nutrient restriction of the dam creates growth-restricted fetuses while leaving an intact uteroplacental circulation, vital for evaluating novel therapies for FGR. Growth-restricted fetuses were generated by feeding Dunkin Hartley guinea pig dams 70% of ad libitum intake from four weeks before and throughout pregnancy. The effect of maternal nutrient restriction (MNR) on dams and fetuses was carefully monitored, and ultrasound measurements of pups collected. There was no difference in maternal weight at conception, however by five weeks post conception MNR dams were significantly lighter ( P < 0.05). MNR resulted in significantly smaller pup size from 0.6–0.66 gestation. Ultrasound is a powerful non-invasive tool for assessing the effect of therapeutic interventions on fetal growth, allowing longitudinal measurement of fetuses. This model and method yield data applicable to the human condition without the need for animal sacrifice and will be useful in the translation of therapies for FGR into the clinic.

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-A(165) (VEGF-A(165)) 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 × 10(11) particles) encoding the VEGF-A(165) gene (Ad.VEGF-A(165)) 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-A(165) 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 (E(max) 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-A(165) transduction. Local overexpression of VEGF-A(165) 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.

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.

Correction to: Gene Therapy (2008) 15, 1344–1350; doi:10.1038/sj.gt.2008.102 The authors have noticed that one of the author's names has been published incorrectly. KA Nader should be K Abi-Nader. The correct spelling is now shown above. The authors would like to apologize for this error.