Highlight of new agents inducing capacitation-related changes in stallion spermatozoa

To fertilize the oocyte, the sperm undergoes physiological and biochemical modifications known as “sperm capacitation”. The aim of this study was to analyze by flow cytometry and immunofluorescence analysis the changes induced by several molecules on stallion sperm viability, plasma membrane fluidity, cholesterol content, calcium influx and tyrosine phosphorylation. Moreover, the modifications induced on glycocalyx sperm sugars were studied by means of lectin-based cell microarray analysis. Frozen sperm samples were incubated with calcium ionophore, MβCD, α-Lfucosidase, neurotensin, HSPA8, cAMP and 4-AP. Flow cytometry analysis showed that membrane fluidity was affected by MβCD, cAMP, neurotensin, HSPA8 and 4-AP; cholesterol depletion was induced by MβCD; an increase of intracellular calcium was produced by calcium ionophore and cAMP; and sperm viability was affected by MβCD. Tyrosine phosphorylation increased when sperm was incubated with MβCD and cAMP. Sperm microarray analysis revealed that i) MβCD and cAMP treatment increased α2,3-linked sialic acid and T antigen, whereas decreased α1,3-linked fucose signals; ii) cAMP alone increased α1,6- and α1,2-linked fucoses; iii) MβCD alone reduced sialylated T antigen, lactosamine, αGal, GalNAc, terminating glycans as well as α1,6fucose in high-mannose glycans. The combination of MβCD + cAMP treatment preserved the α2,3-linked sialic acid increasing, determined the GalNAc, GlcNAc, α1,2-linked fucose enhancement, whereas reduced T antigen and high-mannose glycans. Our results determine the specific effect of each molecule in order to establish a combination of several agents to achieve an efficient in vitro capacitation technique for stallion sperm.