Improved bovine in vitro embryo production with sexed and unsexed sperm selected by chemotaxis

DOMINGUEZ, ESTEBAN MAURICIO; TRIBULO H; MORENO-IRUSTA, AYELEN; GIOJALAS LC; GUIDOBALDI, HÉCTOR ALEJANDRO; DOMINGUEZ, ESTEBAN MAURICIO; MORENO-IRUSTA, AYELEN; TRIBULO H; GIOJALAS LC; GUIDOBALDI, HÉCTOR ALEJANDRO

THERIOGENOLOGY

ELSEVIER SCIENCE INC

Año: 2018 vol. 122 p. 1 - 8

0093-691X

Assisted reproductive techniques (ART) have been widely used in farm animals in the last decades. Sexedcryopreserved spermatozoa, ovum pick up, in vitro embryo production and transfer constitute the ARTthat have revolutionized the dairy industry. However, the efficiency of some of these techniques is stilllow due in part to sperm quality, which influences fertilization, embryo development and implantation.The Sperm Selection Assay (SSA), based on sperm chemotaxis towards progesterone, provides a spermsubpopulation enriched with spermatozoa that are capacitated, with intact DNA and low level ofoxidative stress. Since the SSA selects a sperm subpopulation at optimum physiological state, theapplication of the SSA may improve the efficiency of the current ART. The aim of this study was to adaptthe SSA for unsexed and sexed bovine frozen-thawed semen samples, and then to test whether spermselection by the SSA improves the cleavage rate of bovine embryos in vitro. The optimal SSA conditions toobtain the higher sperm accumulation percentage given by chemotaxis were the same for both unsexedand sexed semen samples. Thus, sperm accumulation in W2 was significantly higher when: 2 millionsperm per mL were placed in W1 (unsexed samples: 12 ± 1%, p ¼ 0.002; sexed samples: 14 ± 3%,p ¼ 0.02); 1 pM progesterone was placed in W2 (unsexed sample: 9 ± 1%, p ¼ 0.009; sexed samples:11 ± 2%, p ¼ 0.02); and to incubate the SSA device for 10 min (unsexed samples: 17 ± 2%, p ¼ 0.007; sexedsamples: 10 ± 1%, p ¼ 0.004). We found that the quality of spermatozoa recovered from W2 in unsexedand sexed semen was enhanced. Thus, the capacitation index was significantly increased (unsexedsamples: 1.75 ± 0.1, p ¼ 0.0001; sexed samples: 1.76 ± 0.2, p ¼ 0.004), while DNA fragmentation indexwas significantly decreased (unsexed samples: 0.33 ± 0.07, p ¼ 0.0003; sexed samples: 0.32 ± 0.04,p ¼ 0.002). Moreover, the cleavage index of oocytes fertilized with either unsexed or sexed SSA-selectedsperm was significantly improved (unsexed samples: 3.2 ± 0.4, p ¼ 0.0001; sexed samples: 2.3 ± 0.33,p ¼ 0.03). Thus, we show that the SSA can be used to recruit a bovine sperm subpopulation at optimalfunctional state regardless of whether the sample is previously sexed, and that this optimal state improvesbovine embryo cleavage rate.