Fetal Sex and Fetal Environment Interact to Alter Diameter, Myogenic Tone, and Contractile Response to Thromboxane Analog in Rat Umbilical Cord Vessels.

Benoit Sicotte,Michèle Brochu

doi:10.3389/fphys.2021.620058

Abstract

Fetal growth needs adequate blood perfusion from both sides of the placenta, on the maternal side through the uterine vessels and on the fetal side through the umbilical cord. In a model of intrauterine growth restriction (IUGR) induced by reduced blood volume expansion, uterine artery remodeling was blunted. The aim of this study is to determine if IUGR and fetus sex alter the functional and mechanical parameters of umbilical cord blood vessels. Pregnant rats were given a low sodium (IUGR) or a control diet for the last 7 days of pregnancy. Umbilical arteries and veins from term (22 day) fetal rats were isolated and set-up in wire myographs. Myogenic tone, diameter, length tension curve and contractile response to thromboxane analog U46619 and serotonin (5-HT) were measured. In arteries from IUGR fetuses, myogenic tone was increased in both sexes while diameter was significantly greater only in male fetuses. In umbilical arteries collected from the control group, the maximal contraction to U46619 was lower in females than males. Compared to the control groups, the maximal response decreased in IUGR male arteries and increased in female ones, thus abolishing the sexual dimorphism observed in the control groups. Reduced contractile response to U46619 was observed in the IUGR vein of both sexes. No difference between groups was observed in response to 5HT in arteries. In conclusion, the change in parameters of the umbilical cord blood vessels in response to a mild insult seems to show adaptation that favors better exchange of deoxygenated and wasted blood from the fetus to the placenta with increased myogenic tone.

Highlights

Adequate blood perfusion from both sides of the placental barrier is a prerequisite to the successful growth of the fetus
This is associated with an increased placental vascular resistance (Kalache and Duckelmann, 2012), which might be caused by structural modifications to the placental microcirculatory system, by an increased thickness of stem villi vessel walls and a decreased in lumen circumference (Mitra et al, 2000) or by an abnormal number of tortuous vessels (Baykal et al, 2004)
We showed that sex and fetal environment alter the diameter of umbilical cord vessels and the contractile response to an analog of Thromboxane A2, which could lead to an adaptation during intrauterine growth restricted (IUGR)

Summary

Introduction

Adequate blood perfusion from both sides of the placental barrier is a prerequisite to the successful growth of the fetus. As the umbilical cord lacks innervations, its vascular tone depends of the viscoelastic properties and is under the control of vasoactive substances within the circulation, released locally within the vessel wall or from the placenta. Abnormal Doppler waveforms are observed in the umbilical arteries of intrauterine growth restricted (IUGR) fetuses. This is associated with an increased placental vascular resistance (Kalache and Duckelmann, 2012), which might be caused by structural modifications to the placental microcirculatory system, by an increased thickness of stem villi vessel walls and a decreased in lumen circumference (Mitra et al, 2000) or by an abnormal number of tortuous vessels (Baykal et al, 2004). The contractile response to KCl was decreased in umbilical arteries from IUGR guinea pigs compared to their control group counterparts (Canas et al, 2017)

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