Expression of thyroid hormone transporters in the human placenta and changes associated with intrauterine growth restriction

MCT8 and MCT10 ontogeny in human placenta. A, B: Relative mRNA expression (mean ± sem) in human placentae from 6 to 34 wks compared to term, given an arbitrary value of 1; **p < 0.01, ***p < 0.001 compared to term; ⁺p < 0.05 and ⁺⁺p < 0.01 compared to 27–34 wks. C, D: Western blot on placental homogenates from normal human placentae (8–40 wks) demonstrating a band at ∼60 kDa for MCT8 (C) and ∼50 kDa for MCT10 [34] (D). Immunoblotting for β-actin on the same blot was used to assess protein loading. E: Specificity of the MCT8 polyclonal antibody was tested in MCT8-null JEG-3 cells transfected with empty vector (VO) or MCT8 plasmid (MCT8) and placental homogenates from normal human term placentae (Term PL). F, G: Densitometry of the protein bands shown in C and D respectively; *p < 0.05. H: Representative sections demonstrating MCT10 immunoreactivity in 1st trimester (H1), term (H2) placenta and in 1st trimester placental bed (H3). Villous cytotrophoblasts are shown by arrows, syncytiotrophoblasts by arrowheads and EVTs in placental bed by thick arrows. All photographed with 40× objective lens.

OATP1A2 and OATP4A1 ontogeny in human placenta. A, B: Relative mRNA expression (mean ± sem) in human placentae from 6 to 34 wks compared to term, given an arbitrary value of 1; *p < 0.05 compared to term. C, D: Western blot on placental homogenates from normal human placentae (8–39 wks) demonstrated multiple bands between 60 and 85 kDa representing different glycosylated states with the OATP1A2 antibody and a single band at ∼60 kDa for OATP4A1 [35]. Immunoblotting for β-actin on the same blot was used to assess protein loading. Relative densitometry of the protein bands is shown below the corresponding blot. E, F: Representative sections demonstrating immunoreactivity of OATP1A2 and OATP4A1 in 1st trimester (E1, F1), term (E2, F2) placenta and in 1st trimester placental bed (E3, F3). Villous cytotrophoblasts are shown by arrows, syncytiotrophoblasts by arrowheads and EVTs in placental bed by thick arrows. All photographed with 40× objective lens.

LAT2, LAT1 and CD98 ontogeny in human placenta. A–C: Relative mRNA expression (mean ± sem) in normal human placentae from 6 to 34 wks compared to term, given an arbitrary value of 1; *p < 0.05, **p < 0.01, ***p < 0.001 compared to term. D: CD98 Western blot on placental homogenates from normal human placentae (8–39 wks) demonstrated a broad band with two distinct species at 75 and 100 kDa representing different glycosylation states of CD98 [25]. Immunoblotting for β-actin on the same blot was used to assess protein loading. Densitometry of the protein bands is shown below the blot.

MCT8 and MCT10 expression in IUGR and AGA placentae. A, D: Relative mRNA expression of MCT8 or MCT10 in early (25–32 wks) and late (37–38 wks) 3rd trimester IUGR placentae compared to gestationally-matched AGA controls (27–34 wks and 37–41 wks respectively). Scatter dot plots represent individual relative expression with mean (dotted line) and sem. B, E: Representative Western blots showing MCT8 and MCT10 protein in placental homogenates from early and late 3rd trimester AGA pregnancies and in those complicated by IUGR. Immunoblotting for β-actin on the same blots was used to assess protein loading. C, F: Relative densitometry analysis of MCT8 and MCT10 protein expression respectively. MCT8: pooled data from 2 separate Western blots including a total of 8 IUGR and 8 AGA samples; MCT10: pooled data from 3 separate Western blots including a total of 4 IUGR and 4 AGA samples; *p < 0.05.

OATP1A2, OATP4A1, LAT1, LAT2 and CD98 expression in IUGR and AGA placentae. Relative mRNA expression in IUGR human placentae (early: 25–32 wks and late: 37–38 wks 3rd trimester gestational groups) compared to gestationally-matched AGA controls (27–34 wks and 37–41 wks respectively); Scatter dot plots represent individual relative expression with mean (dotted line) and sem. Analysis using 2-way ANOVA showed no significant differences.