Vascular network modeling reveals significant differences in vascular morphology in growth-restricted placentas.

AIM: To construct and examine models of the vascular networks using the technique of vascular corrosion casting in placentas collected from normal pregnancies and from pregnancies complicated by fetal growth restriction (FGR). METHODS: Twenty placentas were collected from normal term pregnancies (Group NP) and an equal number from pregnancies with idiopathic term FGR (Group FGR) and placental vascular network models constructed by perfusing an acrylic-based solution separately into the umbilical vein and arteries. Placental blood volumes and blood vessel characteristics (number of branches, diameter, and morphology) were then examined and compared. RESULTS: In placentas from Group NP, the veins branched five to seven times with a peripheral artery-to-vein ratio ranging from 1:2 to 1:3. In placentas from Group FGR, the veins branched only four to five times with an artery-to-vein ratio of 1:1 to 2:1 and increased evidence of nodularity and pitting of the vessel walls. The two groups showed significant differences in placental blood volume and in the mean diameters of umbilical veins and arteries. In Group FGR, significant positive correlations could be found between birth weight and placental volume, venous diameters, and select arterial diameters. CONCLUSION: Vascular network models can be constructed from term placentas. Such modeling may provide novel insights and improve our understanding of the placental vascular system in both health and disease.

[Correlation between oligohydramnios and abnormal expressions of TXA2, PGI2 and TXA2R in the umbilical arterial blood and placenta].

OBJECTIVE: To investigate the roles of thromboxane A(2) (TXA(2)) and prostaglandin I(2) (PGI(2)) in development of oligohydramnios. METHODS: The concentration of TXB(2) and 6-keto-PGF1 in umbilical cord blood collected from 30 normal parturients (control) and 30 parturients with oligohydramnios was detected by radioimmunoassay to calculate the TXA(2)/PGI(2) ratio. Immunohistochemistry was performed to detect the contents of TXA(2)R in vascular endothelial cell in the placental villi. RESULTS: Compared with the control group, the concentration of umbilical cord blood TXB(2) in oligohydramnios group was significantly increased (P<0.01), but the elevation of 6-keto-PGF(2) concentration was not statistically significant (P>0.05). The oligohydramnios group showed significantly higher positivity rates of TXB2 and 6-keto-PGF1 in than the control group (P<0.01), and the positivity rate of TXA(2)R in the vascular endothelial cells in the placental villi was also significantly higher in the oligohydramnios group (22/30, 77.3% vs 11/30, 36.7%, P<0.05). Most of the TXA(2)R-positive cases in the oligohydramnios group showed strong positivities of TXA(2)R. CONCLUSION: Abnormal elevation of TXA(2) concentration in the umbilical cord blood and the TXA(2)/PGI(2) imbalance are responsible for the development of oligohydramnios.