Effect of Bushen Yiqi Huoxue recipe on placental vasculature in pregnant rats with fetal growth restriction induced by passive smoking

Interactions of vascular endothelial growth factor (VEGF) with receptors VEGFR1/Flt1 and VEGFR2/Flk1, and those of angiopoietins (Ang-1, Ang-2) with receptor Tie2 play important roles in placental angiogenesis. This study investigated vascular morphology and expression of these angiogenic factors in rat placenta on the day 15, 18, 21 of gestation (D15, D18 and D21). The rats were randomly assigned into 3 groups: normal group, model group [fetal growth restriction (FGR) model], and Bushen Yiqi Huoxue (BYHR) recipe treatment group (BYHR group, the pregnant rats with FGR were treated with BYHR recipe). Morphological analysis indicated that during initial villous formation, fetal nucleated erythrocytes (FNEs) appeared in maternal blood sinus (MBS). Subsequently, FNEs were surrounded by endothelial cells to form fetal capillary (FC) and then by trophoblast cells to form villi. As pregnancy proceeded, FC density increased progressively with increasing endothelial identification staining (EIS) in normal and BYHR groups. Whereas, villous formation was suppressed, normal increase in FC density was impaired and EIS was weakened in model group. Quantitative PCR analysis showed that VEGF and Flk1 mRNA increased over gestation in all groups, indicating that VEGF might play a pivotal role in FC growth during late gestation. VEGF mRNA was increased on D15, while decreased on D21 in model group as compared with normal group and BYHR group. Immunohistochemically, Ang-2 protein was highly expressed in FNEs, gradually disappeared as villi matured, and decreased over gestation in all groups, indicating that Ang-2 might play a pivotal role in villous formation, which was further supported by decreased Ang-2 mRNA and protein expression in model group on D15. Ang-1 mRNA, Tie2 mRNA and Ang-1/Ang-2 ratio increased from D15 to D18 in all groups as placenta matured. Ang-1 mRNA, Tie2 mRNA and Ang-1/Ang-2 ratio were decreased on D18 in model group as compared with normal and BYHR groups, indicating delayed maturity of FGR placenta. Alterations in angiogenic factors may result in altered placental vasculature and cause placental insufficiency. BYHR recipe could balance the angiogenic factors to promote the formation and maturation of FGR placental vasculature.