Relative amounts of sialic acid and fucose of amniotic fluid glycoconjugates in relation to pregnancy age

Abstract

The present knowledge concerning the glycan structures and role of glycoconjugates derived from amniotic fluid is fragmentary and mainly focuses on the individual glycoproteins. The question has arisen as whether the general glycosylation pattern of amniotic fluid glycoconjugates can change with the progression of a normal pregnancy. In the present work we have described the dynamic, quantitative alterations in relative amounts of sialic acid and fucose linked by a variety of anomeric linkages to subterminal oligosaccharide structures of amniotic fluid glycoconjugates in relation to pregnancy age. The analysis was performed in the following groups of amniotic fluids derived from normal pregnancy by lectin dotting method: "2nd trimester" (14-19 weeks), "3rd trimester" (29-37 weeks), "perinatal period" (38-40 weeks) , "delivery at term" (39-41 weeks) and "post date pregnancy" (41-43 weeks). In the "3rd trimester" the amniotic fluid glycoconjugates contained higher relative amounts of glycans terminated by alpha2-6-linked sialic acid (p < 0.00002) and by alpha1-6 innermost fucose (p < 0.000001) than those in the 2nd trimester. In contrast, they showed the lower relative amount of fucose linked alpha1-3 (p < 0.02). At the perinatal period the relative amount of alpha2-6-linked sialic acid increased (p < 0.03), and it then decreased during delivery (p < 0.02) to the level found in the "3rd trimester" group. In the post date pregnancy all parameters studied increased. The sialyl- and fucosyl-glycotopes of the amniotic fluid glycoconjugates may play an critical role in growth and tissue remodeling of the foetus, as well as may might reflect maturation of a foetus. Additionally, a determination of the glycotope expressions might be helpful in prenatal diagnosis as predictor factors for well being of mother and child.

Terminal monosaccharide expression on amniotic glycoproteins as biomarkers of fetus maturity

“…In the second trimester of pregnancy AF glycoconjugates reveal the presence of oligosaccharides terminated with α2,3-and α2,6-linked sialic acids, and fucoses linked via α1,6-linkage to core oligosaccharide and α1,3-and α1,2-linked at the non-reducing termini [20]. At this time, AF AGP and FN (fibronectin) present mainly maternal-type glycans in terms of branching, sialylation and/or fucosylation.…”

“…With the physiological development of the organs of the fetus, the expression of the α2,6-linked sialic acid and α1,6-core fucose in amniotic glycoconjugates increases, whereas the α1,3-linked fucose decreases [20]. Briese et al [9] have reported that, in the third trimester, the sialic acid synthesized by the maternal tissues crosses the placenta to contribute to fetal growth.…”

“…α2,6-Sialylation of amniotic glycoconjugates increases significantly, whereas α2,3-linked sialic acid, only slightly. At the same time, the fucosylation pattern is almost at a constant level [20]. In contrast, the amniotic AGP and FN sialylation with both types of sialic acid linkages remains almost unaltered starting from the third trimester and throughout the perinatal period [23,24].…”

“…Inflammatory activation occurs with normal-term labour to accelerate processes necessary for successful labour and delivery [40]. During delivery the total glycoconiugates are characterized by α2,6-desialylation, whereas α2,3-sialylation and the three types of fucosylation remain nearly unaltered [20]. The α2,6-and α2,3-sialylation, as well as α1,6-fucosylation of amniotic AGP and all isoforms of FN, remain almost unchanged during delivery [5,23,24]; however, delivery is associated with the decrease of outer arm α1,3-and α1,2-linked fucose expression in AGP [5].…”

Mass spectrometry‐based proteomics in reproductive medicine

“…Most of the AF proteins are structurally glucoconjugates, which promote growth and differentiation of fetal tissues (Orczyk-Pawilowicz et al, 2005). They include oncofetal antigens, hormones, enzymes, and various cytokines.…”