Comparison of the glycoprofile of epididymal fluid, seminal plasma, and glycocalyx of epididymal and ejaculated spermatozoa of dromedary camels

The surface of sperm contains a thick glycocalyx whose glycosylation begins in the testes and undergoes changes during transit through the epididymis and other components of the male genital tract, where new glycans secreted into the lumen may be absorbed by the sperm surface or incorporated into the plasma membrane. The sperm glycocalyx plays a key role in reproduction as it is involved in sperm motility, maturation and fertilisation, as well as protecting sperm from humoral and cellular immunity in the uterus. Camelid ejaculate is highly viscous, which limits its processing and use in assisted reproductive technology (ART). Recently, epididymal sperm (ES) have been used in ART in several domestic animal species and may be an alternative to overcome viscosity-related problems in camelid ART. Since the sperm glycocalyx is involved in the functional and physicochemical characteristics of ejaculate, this research focused on comparing the glycan composition of the glycocalyx of ES and ejaculated spermatozoa (EJS), as well as epididymal fluid and seminal plasma of dromedary camels using ten fluorescent lectins. The sperm glycoanalysis was performed in epididymal and ejaculated spermatozoa before and after washing with TCF. The epididymal fluid did not react with the lectins used, unlike seminal plasma (SP), which showed a high presence of mannosylated and α2,6-sialylated N-glycans, a low content of terminal Forssman antigen and α/βGalNAc in O-glycans and fucose residues. ES surface displayed high levels of N-linked glycans and O-glycans terminating with Galβ1,3GalNAc (T antigen), a moderate presence of α2,3-/ α2,6-sialilated glycans, and weak content of both fucosylated and α/ βGalNAc-terminating O-glycans before and after washing. The surface of unwashed EJS did not express the T antigen and α2,6-sialilated glycans. Still, it showed a low presence of the other sugars mentioned above, which were more prevalent in the glycocalyx of washed EJS, where the reappearance of T antigen in the acrosomal region was detected, and the presence of Forssman antigen in the acrosomal and tail regions and terminal lactosamine in the caudal region was also found. These results demonstrate that SP glycoproteins adhere to the surface of the EJS and that this masks the T antigen residues, which, together with the Forssman antigen and lactosamine, the latter absent in the ES glycocalyx, characterise the glycocalyx of EJS compared to epididymal sperm. Whether the absence of the Forssman antigen and lactosamine residues precludes the effectiveness of epididymal sperm in camelid ART could be an interesting subject for future studies.