Cytochemical study on human spermatozoa metabolism during in vitro capacitation

Comprehensive proteomic analysis of bovine spermatozoa of varying fertility rates and identification of biomarkers associated with fertility

BACKGROUND

Male infertility is a major problem for mammalian reproduction. However, molecular details including the underlying mechanisms of male fertility are still not known. A thorough understanding of these mechanisms is essential for obtaining consistently high reproductive efficiency and to ensure lower cost and time-loss by breeder.

RESULTS

Using high and low fertility bull spermatozoa, here we employed differential detergent fractionation multidimensional protein identification technology (DDF-Mud PIT) and identified 125 putative biomarkers of fertility. We next used quantitative Systems Biology modeling and canonical protein interaction pathways and networks to show that high fertility spermatozoa differ from low fertility spermatozoa in four main ways. Compared to sperm from low fertility bulls, sperm from high fertility bulls have higher expression of proteins involved in: energy metabolism, cell communication, spermatogenesis, and cell motility. Our data also suggests a hypothesis that low fertility sperm DNA integrity may be compromised because cell cycle: G2/M DNA damage checkpoint regulation was most significant signaling pathway identified in low fertility spermatozoa.

CONCLUSION

This is the first comprehensive description of the bovine spermatozoa proteome. Comparative proteomic analysis of high fertility and low fertility bulls, in the context of protein interaction networks identified putative molecular markers associated with high fertility phenotype.

Effects of deep freezing on the energy metabolism of bovine spermatozoa during in vitro capacitation: A cytochemical approach

In order to study the effects of deep freezing on the energy metabolism of bovine spermatozoa, a cytochemical quantitative study was carried out by a microdensitometric method on cytochrome oxidase and lactate dehydrogenase (LDH) activities. These were evaluated in situ on individual frozen-thawed bull spermatozoa collected at different times during in vitro capacitation. The results showed that in bull spermatozoa both the initiation of motility and capacity to fertilize eggs were associated with the anaerobic rather than aerobic glycolysis. The freezing-thawing processes and storage in liquid nitrogen induced a general enhancement of both the enzymatic activities examined. The high ionic strength treatment gave rise to a significant but reversible decrease in both the cytochrome oxidase and LDH activities in the fresh as well as in the frozen-stored sperm. The findings, based on cytochemical observations of energy metabolism of spermatozoa and evaluated during in vitro capacitation, suggest that the respiration and the anaerobic glycolysis of spermatozoa seem to be slightly impaired by the freezing-thawing and storage processes.