Extracellular vesicles from seminal plasma to improve fertilizing capacity of bulls

Abstract

Extracellular vesicles (EVs) contained in seminal plasma, vehicle RNA, proteins, and other molecules able to influence the biological function of sperm. The aim of this study was to improve the fertilizing capacity of male gametes of low-fertility bulls using EVs isolated by ultracentrifugation from the seminal plasma of a bull of proven fertility. After a dose–response curve study, 10×106 sperm of low-fertility bulls were co-incubated for 1 h with 400×106 EVs/mL. In addition, it has been verified that the incorporation of EVs, which takes place in the sperm midpiece, is maintained for 5 h and even after cryopreservation. Subsequently, the spermatozoa of low-fertility bulls, with EVs incorporated, were used for the in vitro production of embryos. The rate of blastocyst at seventh day yield in vitro, with the use of sperm with EVs incorporated, increased by about twice the yield obtained with the same sperm in the absence of EVs: bulls having an average embryonic yield of 6.41 ± 1.48%, 10.32 ± 4.34%, and 10.92 ± 0.95% improved their yield to 21.21 ± 1.99%, 22.17 ± 6.09%, and 19.99 ± 5.78%, respectively (P < 0.05). These encouraging results suggest that it might be possible to keep breeding bulls with poor fertility. Further studies will be needed to evaluate the in vivo fertility of sperm treated with EVs and understand how the content of EVs is involve in the sperm–vesicle interaction and in the improved sperm performance. Lay summary Sperm can fertilize eggs after they mature as they move through the tube in the testes. As they move, the sperm communicate with the lining of the tubes, thanks to small sacs which are made by the tube itself. These sacs contain many molecules that may play a part in the mechanisms that help sperm fertilize eggs. In veterinary medicine, as with humans, there are fertile and less-fertile individuals. It is possible that the sacs of the semen from a bull which is known to be fertile are different to those from a bull with low fertility. For this reason, sacs from bulls with proven fertility were mixed with sperm from the less-fertile bulls to test in the laboratory how the sperm was able to fertilize eggs and produce embryos. The results show that, in the laboratory, the number of embryos produced is doubled. This suggests it would be possible to improve the fertility of people who are less fertile.