Preeclampsia does not alter vascular growth and expression of CD31 and vascular endothelial cadherin in human placentas

Abstract

Preeclampsia is characterized by maternal endothelial dysfunction (e.g., increased maternal vascular permeability caused by the disassembly of endothelial junction proteins). However, it is unclear if preeclampsia is associated with impaired vascular growth and expression of endothelial junction proteins in human placentas. Herein, we examined vascular growth in placentas from women with normal term (NT) and preeclamptic (PE) pregnancies using two endothelial junction proteins as endothelial markers: CD31 and vascular endothelial-cadherin (VE-Cad). We also compared protein and mRNA expression of CD31 and VE-Cad between NT and PE placentas, and determined the alternatively spliced expression of CD31 using PCR. We found that CD31 and VE-Cad were immunolocalized predominantly in villous endothelial cells. However, capillary number density (total capillary number per unit villous area) and capillary area density (total capillary lumen area per unit villous area) as well as CD31 and VE-Cad protein and mRNA levels were similar between NT and PE placentas. PCR in combination with sequence analysis revealed a single, full-length CD31, suggesting that there are no alternatively spliced isoform of CD31 expressed in placentas. These data indicate that preeclampsia does not significantly affect vascular growth or the expression of endothelial junction proteins in human placentas.

Keywords: CD31; VE-cadherin; placenta; preeclampsia; vasculature.

Figure 1.

Immunolocalization of CD31 and VE-Cad in human placentas from women with normal term (NT) and preeclamptic (PE) pregnancies. The adjacent tissue sections were incubated with antibodies against CD31 or VE-Cad, or pre-immune goat or mouse IgG (insets). Reddish color indicates positive staining for the CD31 and VE-Cad. Representative images are shown. *lumen of blood vessels. n=10 for each group. Scale, 100 μm.

Figure 2.

(A) Western blot analysis of CD31 and VE-Cad proteins in human placentas from women with normal term (NT) and preeclamptic (PE) pregnancies. Proteins (150 μg for each placental sample, and 20 μg for HUVECs) were subjected to Western blotting. (B–D) Data normalized to β-actin are expressed as the mean ± SEM as a fold-difference with respect to that of the NT pregnancy samples. CD31c and CD31n: indicate antibodies against the C- or N-terminus, respectively, of human CD31. n=10 for each group.

Figure 3.

Sequence analyses of CD31 PCR products from the placentas of women with normal term (NT) and preeclamptic (PE) pregnancies. (A) The PCR products along with a DNA ladder were run on a 1.5% agarose gel. n=5 for each group. (B) Multiple sequence alignment among CD31 PCR products from NT and PE placentas (n=2 for each group), the full-length human CD31 mRNA (NM_000442.4: CD31), and 6 of the human CD31 transcript variants mRNA sequences (XM_005276880.1: CD31, transcript variant X2; XM_005276881.1: CD31, transcript variant X3; XM_005276882.1: CD31, transcript variant X4; XM_005276883.1: CD31, transcript variant X5; XM_006721944.1: CD31, transcript variant X6; XM_006721945.1: CD31, transcript variant X7). Sequences that differ from the full-length human CD31 mRNA are shown in red and highlighted in yellow. The numbers above the sequence alignment indicate the corresponding sequence positions in the full-length human CD31 mRNA sequence. The position of exons 11–16 are shown in blue arrows.