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. 2019 Nov 1;160(11):2748-2758.
doi: 10.1210/en.2019-00463.

PBDEs Concentrate in the Fetal Portion of the Placenta: Implications for Thyroid Hormone Dysregulation

Matthew T Ruis  1 , Kylie D Rock  2 , Samantha M Hall  1 , Brian Horman  2 , Heather B Patisaul  2 , Heather M Stapleton  1   2   3
Affiliations

PBDEs Concentrate in the Fetal Portion of the Placenta: Implications for Thyroid Hormone Dysregulation

Matthew T Ruis et al. Endocrinology. .

Abstract

During pregnancy, the supply of thyroid hormone (TH) to the fetus is critically important for fetal growth, neural development, metabolism, and maintenance of pregnancy. Additionally, in cases where maternal and placental TH regulation is significantly altered, there is an increased risk of several adverse pregnancy outcomes. It is unclear what may be disrupting placental TH regulation; however, studies suggest that environmental contaminants, such as polybrominated diphenyl ethers (PBDEs), could be playing a role. In this study, Wistar rats were gestationally exposed to a mixture of PBDEs for 10 days. THs and PBDEs were quantified in paired maternal serum, dissected placenta, and fetuses, and mRNA expression of transporters in the placenta was assessed. Significantly higher concentrations of PBDEs were observed in the fetal portion of the placenta compared with the maternal side, suggesting that PBDEs are actively transported across the interface. PBDEs were also quantified in 10 recently collected human maternal and fetal placental tissues; trends paralleled observations in the rat model. We also observed an effect of PBDEs on T3 levels in dam serum, as well as suggestive changes in the T3 levels of the placenta and fetus that varied by fetal sex. mRNA expression in the placenta also significantly varied by fetal sex and dose. These observations suggest the placenta is a significant modifier of fetal exposures, and that PBDEs are impacting TH regulation in a sex-specific manner during this critical window of development.

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Figures

Figure 1.
Figure 1.
Concentration of PBDEs in dam serum, maternal placenta, fetal placenta, and fetus. Numbers above brackets represent fold difference in concentration between maternal and fetal placenta. n = number of litters (not pups); error bars represent SEM of litters. *P < 0.05 between maternal and fetal placental concentrations.
Figure 2.
Figure 2.
Ratio of PBDEs in fetal vs maternal placentas measured in both rat (control experiment) and human placentas. The dashed line indicates the 1:1 line. n = number of placentas analyzed; error bars represent SEM of individual placentas.
Figure 3.
Figure 3.
T3 concentration in dam serum, stratified by GD and dose group. n = number of dams; error bars represent SEM of dam. *P < 0.05 in T3 concentrations in dam serum between control and dosed animals at GD 14_15.
Figure 4.
Figure 4.
T3 concentration in maternal and fetal placenta, stratified by GD, sex, and dose group. n = number of litters (not pups); error bars represent SEM of litter. *P < 0.05 between maternal and fetal placental tissue type; #P < 0.05 between GD.
Figure 5.
Figure 5.
T3 concentration in the fetus, stratified by GD, sex, and dose group. n = number of litters (not pups); error bars represent SEM of litter. #P < 0.05 indicates a significant sex difference.
Figure 6.
Figure 6.
Transporter gene expression in the (a) maternal and (b) fetal portion of the placenta (n = 7/8). n = number of litters (not pups); error bars represent SEM of litter. *P < 0.05 between dose groups.
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