Glycoprotein characterization in the uterine glands from cows with normal and cystic ovaries

Uterine glands secrete a variety of molecules, including glycoproteins, collectively termed “uterine milk”, that are essential for maternal support of conceptus survival and growth in mammals. Although it is well-known that glycoproteins can undergo changes related to normal and pathological conditions, the glycans of bovine uterine glands have received scarce attention. The aim of this study was to investigate the distribution and the characterization of the glycoconjugates in the uterine glands from pre-pubertal (PO), periovulatory (PE) normal and cystic ovary (CO) cows by means of conventional and lectin histochemistry. Uterus fragments were fixed in 4% (w/v) neutral formalin and embedded in paraffin wax. Sections were stained to evaluate the neutral mucosubstances/glycoproteins using the PAS reaction, as well as carboxylated and sulphated mucosubstances with Alcian blue (AB) pH 2.5 and AB pH 1.0, respectively. The analysis of oligosaccharides was performed by means of 4 lectins (SNA, PNA, DBA Con A) in association with sialidase (s) treatment. Conventional histochemistry showed no AB staining in all the investigated samples, whereas a weak presence of neutral glycans was found in the cytoplasm and lumen content of the uterine glands from PR and CO cows. The latter also showed supra-nuclear PAS-positive granules. Lectin histochemistry showed: 1) Terminal Forssman pentasaccharide (Fp) and Neu5Ac-FP (DBA and s-DBA reactivity) throughout the gland cytoplasm of PR and PO cows, 2) Terminal Fp, Neu5Acα2,6Gal/GalNAc, terminal Galβ1,3GalNAc (SNA and PNA affinity) in the luminal surface of normal cows and terminal/internal αMan (Con A staining) only in PE cows, whereas Neu5Ac-Fp appeared in the apical surface of CO which expressed a non constant presence of SNA and PNA reactivity; 3) Terminal Fp, Neu5Acα2,6Gal/GalNAc, Galβ1,3GalNAc and terminal/internal αMan in the lumen glands of normal cows as well as Neu5Acα2,3Galβ1,3GalNAc appearance, unsettled Neu5Acα2,6Gal/GalNAc presence and αMan lack in the lumen glands of CO cows. Lastly, supra-nuclear granules reactive to SNA and DBA were only found in the uterine glands of CO cows. These findings show the existence of modifications in the glycoconjugates of the bovine uterine gland linked to physiological and pathological conditions.