Changes in glycoconjugates surfaces of ejaculated sperm related to the fertility status of stallions

Carbohydrates of sperm glycocalyx play a key role in the sperm-egg recognition and zona binding. Therefore, the acquisition of the mature glycocalyx is related to the attaintment of full sperm fertilizing ability. The aim of this study was to evaluate the distribution of carbohydrates in ejaculated spermatozoa from fertile and infertile stallions using lectin histochemistry. Semen from two fertile and one infertile stallions (3 ejaculates each) was diluted in Tyrode’s medium, fixed in 4% (w/v) neutral formalin, smeared on slides and incubated with appropriate dilutions of 12 lectins. The spermatozoa from fertile horses reacted with 1) MAL II, SNA, HPA, Con A, WGA, GSA II in the whole cell surface, 2) PNA, RCA120, SBA in the acrosomal region, 3) GSA I-B4 in the entire head, 4) DBA and UEA I in the postacrosomal region and tail. The spermatozoa from the infertile stallion did not show D-GlcNAc or GalNAc (GSA II and SBA reactivity, respectively) in the acrosomal region, and displayed αGal (GSA I-B4 affinity) and GalNAc in the acrosomal region and tail, respectively. The acrosomal region in a high number of spermatozoa was found to be lacking Neu5acα2,3Galβ1,4GlcNAc, Neu5Acα2,6/GalNAc, Galβ1,3GalNAc, Galβ1,4GlcNAc, αGalNAc, αMan, βGlcNAc, and αGal (MAL II, SNA, PNA, RCA120, HPA, Con A, WGA, and GSA I-B4 reactivity). This indicates that the oligosaccharide sequences of sperm glycocalyx could be related to fertility status and that major glycoconjugates changes could involve the acrosomal region