Galectin-1 (gal-1) is expressed at the feto-maternal interface and plays a role in regulating the maternal immune response against placental alloantigens, contributing to pregnancy maintenance. Both decidua and placenta contribute to gal-1 expression and may be important for the maternal immune regulation. The expression of gal-1 within the placenta is considered relevant to cell-adhesion and invasion of trophoblasts, but the role of gal-1 in the immune evasion machinery exhibited by trophoblast cells remains to be elucidated. In this study, we analyzed gal-1 expression in preimplantation human embryos and first-trimester decidua-placenta specimens and serum gal-1 levels to investigate the physiological role played by this lectin during pregnancy. The effect on human leukocyte antigen G (HLA-G) expression in response to stimulation or silencing of gal-1 was also determined in the human invasive, proliferative extravillous cytotrophoblast 65 (HIPEC65) cell line. Compared with normal pregnant women, circulating gal-1 levels were significantly decreased in patients who subsequently suffered a miscarriage. Human embryos undergoing preimplantation development expressed gal-1 on the trophectoderm and inner cell mass. Furthermore, our in vitro experiments showed that exogenous gal-1 positively regulated the membrane-bound HLA-G isoforms (HLA-G1 and G2) in HIPEC65 cells, whereas endogenous gal-1 also induced expression of the soluble isoforms (HLA-G5 and -G6). Our results suggest that gal-1 plays a key role in pregnancy maternal immune regulation by modulating HLA-G expression on trophoblast cells. Circulating gal-1 levels could serve as a predictive factor for pregnancy success in early human gestation.

Preeclampsia (PE) is a pregnancy-specific disorder characterized by sudden onset of hypertension and proteinuria in the second half of pregnancy (>20 wk). PE is strongly associated with abnormal placentation and an excessive maternal inflammatory response. Galectin-1 (Gal-1), a member of a family of carbohydrate-binding proteins, has been shown to modulate several processes associated with placentation and to promote maternal tolerance toward fetal antigens. Here, we show that Gal-1 exhibits proangiogenic functions during early stages of pregnancy, promoting decidual vascular expansion through VEGF receptor 2 signaling. Blocking Gal-1-mediated angiogenesis or lectin, galactoside-binding, soluble, 1 deficiency results in a spontaneous PE-like syndrome in mice, mainly by deregulating processes associated with good placentation and maternal spiral artery remodeling. Consistent with these findings, we observed a down-regulation of Gal-1 in patients suffering from early onset PE. Collectively, these results strengthen the notion that Gal-1 is required for healthy gestation and highlight Gal-1 as a valuable biomarker for early PE diagnosis.

Transforming growth factor beta (TGF-βs) are secreted from cells as latent complexes and the activity of TGF-βs is controlled predominantly through activation of these complexes. Tolerance to the fetal allograft is essential for pregnancy success; TGF-β1 and -β2 play important roles in regulating these processes. Pregnancy-specific β-glycoproteins (PSGs) are present in the maternal circulation at high concentration throughout pregnancy and have been proposed to have anti-inflammatory functions. We found that recombinant and native PSG1 activate TGF-β1 and TGF-β2 in vitro. Consistent with these findings, administration of PSG1 protected mice from DSS-induced colitis, reduced the secretion of pro-inflammatory cytokines and increased the number of T regulatory cells. The PSG1-mediated protection was greatly inhibited by the co-administration of neutralizing anti-TGF-β Ab. Our results indicate that proteins secreted by the placenta directly contribute to the generation of active TGF-β and identify PSG1 as one of the few known biological activators of TGF-β2.

The involvement of gal-1 in the regulation of different processes during the establishment, development and maintenance of pregnancy could be described as unique. Gal-1 has emerged as an important lectin with major functions in pregnancy.

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Disruption of fetal-maternal tolerance mechanisms can contribute to pregnancy complications, including spontaneous abortion. Galectin-9 (LGALS9), a tandem repeat lectin associated with immune modulation, is expressed in the endometrium during the mid and late secretory phases and in decidua during human early pregnancy. However, the role of LGALS9 during pregnancy remains poorly understood. We used real-time PCR and immunohistochemical staining to analyze the expression of Lgals9/LGALS9 during mouse gestation as well as in human tissues obtained from normal pregnancy and spontaneous abortions. In mice, three Lgals9 splice variants were detected, the expression of which was differentially regulated during gestation. Furthermore, decidual Lgals9 expression was deregulated in a mouse model of spontaneous abortion, whereas placental levels did not change. We further found that the LGALS9 D5 isoform suppresses interferon gamma production by decidual natural killer cells. In human patients, six Lgals9 splice variants were detected, and a decrease in Lgals9 D5/10 was associated with spontaneous abortion. Altogether, these results show a differential regulation of Lgals9 isoform expression during normal and pathological pregnancies and designate Lgals9 as a potential marker for adverse pregnancy outcomes.

Cirrhosis is characterized by an excessive accumulation of extracellular matrix components including hyaluronic acid (HA) and is widely considered a preneoplastic condition for hepatocellular carcinoma (HCC). 4-Methylumbelliferone (4MU) is an inhibitor of HA synthesis and has anticancer activity in an orthotopic HCC model with underlying fibrosis. Our aim was to explore the effects of HA inhibition by 4MU orally administered on tumor microenvironment. Hepa129 tumor cells were inoculated orthotopically in C3H/HeJ male mice with fibrosis induced by thioacetamide. Mice were orally treated with 4MU. The effects of 4MU on angiogenesis were evaluated by immunostaining of CD31 and quantification of proangiogenic factors (vascular endothelial growth factor, VEGF, interleukin-6, IL-6 and C-X-C motif chemokine 12, CXCL12). IL-6 was also quantified in Hepa129 cells in vitro after treatment with 4MU. Migration of endothelial cells and tube formation were also analyzed. As a result, 4MU treatment decreases tumor growth and increased animal survival. Systemic levels of VEGF were significantly inhibited in 4MU-treated mice. Expression of CD31 was reduced after 4MU therapy in liver parenchyma in comparison with control group. In addition, mRNA expression and protein levels of IL-6 and VEGF were inhibited both in tumor tissue and in nontumoral liver parenchyma. Interestingly, IL-6 production was dramatically reduced in Kupffer cells isolated from 4MU-treated mice, and in Hepa129 cells in vitro. Besides, 4MU was able to inhibit endothelial cell migration and tube formation. In conclusion, 4MU has antitumor activity in vivo and its mechanisms of action involve an inhibition of angiogenesis and IL-6 production. 4MU is an orally available molecule with potential for HCC treatment.

Fetal growth restriction (FGR) is the most common pregnancy complication in developed countries. Pregnancies affected by FGR, frequently concur with complications and high risk of neonatal morbidity and mortality. To date, no approved treatment is available for pregnant women affected with FGR. The objective of this study was to investigate the contribution of galectin-3 (gal-3), a β-galactoside binding protein involved in pregnancy, placental function and fetal growth. We demonstrated that lack of gal-3 during mouse pregnancy leads to placental dysfunction and drives FGR in the absence of a maternal preeclampsia syndrome. Analysis of gal-3 deficient dams revealed placental inflammation and malperfusion, as well as uterine natural killer cell infiltration with aberrant activation. Our results also show that FGR is associated with a failure to increase maternal circulating gal-3 levels during the second and third trimester in human pregnancies. Placentas from human pregnancies affected by FGR displayed lower gal-3 expression, which correlated with placental dysfunction. These data highlight the importance of gal-3 in the promotion of proper placental function, as its absence leads to placental disease and subsequent FGR.