Placental Expression Patterns of Galectin-1, Galectin-2, Galectin-3 and Galectin-13 in Cases of Intrauterine Growth Restriction (IUGR)

Abstract

Galectins (gal) are members of the mammalian β-galactoside-binding proteins and recognize Galβ1-4GlcNAc and Galβ1-4GalNac (Thomsen-Friedenreich antigen (TF)) sequences of several cell surface oligosaccharides. In this study, gal-1, -2, -3 and -13 were investigated systematically in the trophoblast and decidua compartment of intrauterine growth restriction (IUGR) placentas and normal third trimester control placentas and stratified by fetal gender and gestational age. Within this study, 29 third trimester placentas after delivery were analyzed. Fetal gender was equally divided within both groups, and immunohistochemical staining was analyzed according to fetal gender and gestational age. Double immune-fluorescence with trophoblast-specific markers was used to identify galectin-expressing cells at the feto-maternal interface in the decidua. Gal-3 was significantly downregulated only in the extravillous trophoblast of IUGR placentas. In contrast, expressions of gal-2 and gal-13 were downregulated in both villous and extravillous trophoblast cells of IUGR placentas. In addition, gal-2 and gal-13 showed a highly correlated expression scheme in the placenta. There are significant gender-specific expression patterns for single prototype galectins with downregulation of gal-2 and gal-13 of male gender placentas in cases of IUGR. Gal-3 as the chimera type galectin shows only little gender-specific differences in expression, which disappear in IUGR cases.

Keywords: IUGR; decidua; galectins; placenta; trophoblast.

Figure 1

Staining of gal-1 in the villous trophoblast in cases of IUGR is shown in (A); for comparison with control placenta, see (B), showing only slight differences in staining intensity. The presentation of staining results is shown in (C) as a box-plot. The range between the 25th and 75th percentiles is represented by the boxes with a horizontal line at the median. The bars show the fifth and 95th percentiles. The circle indicates values more than 1.5 box lengths.

Figure 2

Gal-2 staining in cases of IUGR in villous trophoblasts (A) compared to control placentas (B) [20] appeared to be downregulated. The noted differences in staining intensity are statistically significant (* p = 0.002), as shown in the box-plot (C). The range between the 25th and 75th percentiles is represented by the boxes with a horizontal line at the median. The bars show the fifth and 95th percentiles. The circle indicates values more than 1.5 box lengths.

Figure 3

In extravillous trophoblasts, gal-2 expression appeared also to be decreased in IUGR placentas (A) compared to control placentas (B); Immunostaining revealed a statistically-significant four-fold decrease (* p = 0.002) in IUGR cases in comparison to control placentas, as shown in the box-plot presentation (C). For details of the box-plot interpretation, see the legend of Figure 2.

Figure 3

In extravillous trophoblasts, gal-2 expression appeared also to be decreased in IUGR placentas (A) compared to control placentas (B); Immunostaining revealed a statistically-significant four-fold decrease (* p = 0.002) in IUGR cases in comparison to control placentas, as shown in the box-plot presentation (C). For details of the box-plot interpretation, see the legend of Figure 2.

Figure 4

Gal-3 showed intermediate staining intensity in extravillous trophoblasts for control placentas (A); in cases of IUGR, extravillous trophoblast staining revealed a totally absent expression in 60% of the cases with a median IRS of zero (B); these results are statistically significant with * p = 0.032, shown in the box-plot presentation (C). For details of the box-plot interpretation, see the legend of Figure 2.

Figure 5

In villous trophoblast gal-13 expression is down regulated in cases of IUGR (A) compared to control placentas with high expression of gal-13 (B); The results in staining intensity are statistically significant (* p = 0.002) as shown in the Box-plot (C). For details of Box-plot interpretation see legend of Figure 2, and the asterisk indicates values more than 3.0 box lengths from the 75th percentile.

Figure 6

In IUGR placentas, gal-13 expression in extravillous trophoblasts was rarely detectable. IRS scoring revealed only weak to no expression (A); control placentas showed intermediate expression for gal-13 (B); again, all results were statistically significant (* p = 0.003). In summary the scoring result is presented in box-plot form (C). For details of the box-plot interpretation, see the legend of Figure 2.

Figure 7

Gal-2 (A) (marked in red color) was found exclusively expressed by extravillous trophoblast cells marked with an HLA-G antibody (B); marked in green. A similar expression schema was found for gal-3 in the decidua. Gal-3 (C); also with red staining, showed a strong co-expression with CK-7 (D); shown in green. In addition, gal-3 is also expressed by cells negative for CK-7. Gal-13 staining in red (E) was found co-expressed by extravillous trophoblast cells marked with a CK-7 antibody in green (F). Scale bar, 500 µm in all cases.

Figure 8

Stratification for gestational age does not reveal any dependency of galectin expression levels on progressing gestational age, as depicted for gal-2 in villous (a) and extravillous trophoblasts (b), for gal-3 in EVT (c) and gal-13 in both villous (d) and extravillous trophoblasts (e).

Figure 9

Male IUGR placentas showed a significantly lower production (3.5-fold downregulation) of gal-2 mRNA compared to the control placentas analyzed, with β-actin as the housekeeping gene.

Figure 10

Control tissue for evaluation of gal-1 staining in duodenum (A); As a positive control for gal-2 and gal-3 expression, colon tissue was stained ((B,C), respectively). Appropriate negative controls are shown as inserts of each figure.