Galectin-1 Is Part of Human Trophoblast Invasion Machinery - A Functional Study In Vitro

Abstract

BackgroundInteractions of glycoconjugates with endogenous galectins, have been long proposed to participate in several reproductive processes including implantation. In human placenta gal-1, gal-3, gal-8, and gal-13 proteins are known to be present. Each of them has been proposed to play multiple functions, but so far no clear picture has emerged. We hypothesized that gal-1 participates in trophoblast invasion, and conducted Matrigel invasion assay using isolated cytotrophoblast from first trimester placenta and HTR-8/SVneo cell line to test it.Methods and FindingsFunction blocking anti-gal-1 antibody was employed to assess participation of endogenous gal-1 in cell adhesion, cell invasion of HTR-8/SVneo cells. When gal-1 was blocked in isolated trophoblast cell invasion was reduced to 75% of control (SEM±6.3, P<0.001) and to 66% of control (SEM±1.7, P<0.001) in HTR-8/SVneo cell line. Increased availability of gal-1, as two molecular forms of recombinant human gal-1 (CS-gal-1 and Ox-gal-1), resulted in increased cell invasion by cytotrophoblast to 151% (SEM±16, P<0.01) with 1 ng/ml of CS-gal-1, and to 192% (SEM±51, P<0.05) with 1 µg/ml of Ox-gal-1. Stimulation was also observed in HTR-8/SVneo cells, to 317% (SEM±58, P<0.001) by CS-gal-1, and to 200% (SEM±24, P<0.001) by Ox-gal-1 at 1 µg/ml. Both sets of results confirmed involvement of gal-1 in trophoblast invasion. Galectin profile of isolated cytotrophoblast and HTR-8/SVneo cells was established using RT-PCR and real-time PCR and found to consist of gal-1, gal-3 and gal-8 for both cell types. Only gal-1 was located at the trophoblast cell membrane, as determined by FACS analysis, which is consistent with the results of the functional tests.Conclusion and SignificanceThese findings qualify gal-1 as a member of human trophoblast cell invasion machinery.

Galectin-1 influences trophoblast immune evasion and emerges as a predictive factor for the outcome of pregnancy

“…In this context, gal-1 is expressed in the CTB of middle and distal cell columns differentiating toward fully invasive trophoblast (Vicovac et al, 1998) and has been recently reported as a component of the human trophoblast invasion machinery. Thus, while gal-1 silencing has a negative effect on trophoblast cell invasion capacity, exogenous gal-1 stimulation has been shown to enhance this process (Kolundzic et al, 2011). This observation is in agreement with the identification of gal-1 expression as a signature of cell invasiveness when comparing highly and poorly invasive mammary carcinoma cell lines (Harvey et al, 2001).…”

“…Gal-1 is up-regulated within the decidua (on stromal cells and NK cells) and can induce tolerogenic DCs, emerging as a key modulator of T cell functions (Blois et al, 2007;Kopcow et al, 2008;Than et al, 2008). In addition, gal-1 has been found to induce trophoblast invasion and fusion during placentation, and may thus be important for the regulation of trophoblast differentiation (Fischer et al, 2010;Kolundzic et al, 2011). Together with its influence on the immune evasion machinery in trophoblast cells by regulating HLA-G expression described here, these data strongly suggest that gal-1 plays a central role in the maintenance of pregnancy.…”

“…Another important source of gal-1 is the placenta, particularly the cytotrophoblast (CTB) of the mid and distal columns during the first trimester of pregnancy (Vicovac et al, 1998). Putative roles played by gal-1 during placentation include the organization of extracellular matrix and the regulation of trophoblast differentiation and cell motility (Vicovac et al, 1998;Jeschke et al, 2010;Kolundzic et al, 2011). However, the role of gal-1 in trophoblast immune evasion mechanism has not been extensively studied yet.…”

Extracellular presence/release of galectins from HTR-8/SVneo extravillous trophoblast cells*

“…It is widely accepted that both gals (Than et al, 2012; and EVs (Redman and Sargent, 2008;Mincheva-Nilsson and Baranov, 2014) serve as important mediators in early pregnancy events. It is of interest to note that EVT cell invasion is increased by both gal-1 (Kolundzic et al, 2011b) and EVs from cytotrophoblast cells grown in a hypoxic environment (Salomon et al, 2013). Both gal-1 (Blois et al, 2007;Tirado-Gonzalez et al, 2013) and placental EVs (Stenqvist et al, 2013;Mincheva-Nilsson and Baranov, 2014;Tannetta et al, 2014) are involved in immunoregulation during pregnancy.…”

“…Three members of the galectin family are found in extravillous trophoblast (EVT): gal-1, gal-3 (Maquoi et al, 1997;Vićovac et al, 1998), and gal-8 (Kolundzic et al, 2011a). In EVT, gals may play multiple roles, possibly in cell adhesion and migration, as shown for gal-1 in EVT in vitro (Kolundzic et al, 2011b). Gal-1 has been also associated with different pregnancy disorders such as spontaneous abortion (Ramhorst et al, 2012), preeclampsia (Than et al, 2008), and gestational diabetes mellitus .…”