Appropriate cell-cell connection between mother and foetus assures a good exchange of nutrients and waste during pregnancy. There are different types of cell-cell connections depending on the placental type. In the bovine epitheliochorial placenta is formed. Extracellular matrix (ECM) proteins, including adhesive proteins that might regulate and be regulated by the activity of metalloproteinases, are key players in this process [[1], [2], [3]]. Besides decorin and dermatopontin which were already examined by our team, one of the important representatives of ECM molecules is glycodelin (Gd) [[4], [5], [6], [7]].

Glycodelin is a glycoprotein in the human and bovine placenta and heifer serum [8,9]. The molecule is also known as placental α2-globulin, chorionic α2-microglobulin, α-uterine protein, placental protein (PP14), progestagen-dependent endometrial protein (PEP), pregnancy-associated endometrial α2-globulin (α2-PEG), and progesterone-associated endometrial protein (PAEP) [10,11]. There are four differently glycosylated isoforms of glycodelin (GdS; GdA; GdF and GdC) detected and secreted in different parts of the reproductive system. While the structure of a particular isoform (including the pattern of glycosylation) influences its function, it participates in the regulation of fertilization, implantation and placentation [8,12]. Immunosuppression, which is crucial for pregnancy maintenance and is supposed to be connected to progesterone, can be directly controlled by one of the Gd isoforms - GdA. Yeung et al. (2009) claimed that immunosuppressive properties of GdA operate at the maternal-foetal interface based on induction of apoptosis of activated T lymphocytes [13]. Seppala et al. (2007) confirmed these results by the description of the relationship between pregnancy loss in women and disturbances in apoptosis of activated T lymphocytes [14]. Glycodelin was pinpointed by Koh et al. (2018) as exclusive to heifers with low fertility, suggesting it might play an essential role in fertility [9].

Glycodelin is synthesized in the endometrium in response to progesterone and relaxin [15]. This protein may regulate the activity of metalloproteinases (MMPs) – the enzymes responsible for ECM remodelling [16].

There are several MMPs with different substrate specificities [[17], [18], [19]]. Many studies have described the presence and the activity of MMP2 and MMP9 both in human and bovine placentas [1,[20], [21], [22], [23], [24], [25], [26], [27]], while the information about MMP3 and MMP7 is rather limited. In women, altered activity of MMP2 and MMP9 can be detected in some pregnancy disorders including preeclampsia [28], premature separation of the placenta [29] and also disturbances in the separation of bovine foetal membranes [24]. Demir-Weusten et al. (2007) demonstrated that tissue localization and the activity of MMP3 in the human placenta are similar to that of MMP9, as they use similar substrates [30]. Zhang et al. (2021) described that the increase in MMP3 expression in bovine endometrium might be related to endometritis [31]. MMP3 can also activate other MMPs [32]. Ulbrich et al. (2011) showed that there are significant increases in MMP2 enzyme activity after the 15th day of the oestrous cycle in bovine endometrial tissue [33].

In the available literature, despite extensively described changes in the amount and distribution of glycoproteins associated with bovine pregnancy, there is still no complete data on their relationship with MMPs.

The aim of this study was to investigate the impact of glycodelin on the activity of selected MMPs (MMP2, MMP3, and MMP7) in the bovine placenta during early-mid pregnancy and parturition, as well as in the endometrial cell cultures, in the context of attachment and detachment of the bovine placenta.