No abstract

In artificial insemination the use of sex-sorted bovine sperm results in reduced conception, the causes of which are only partly understood. Therefore, we set out to investigate the effects of sexing on bovine sperm function and early embryonic development. Computer-assisted semen analysis (CASA) of sperm of the same bulls (n = 5), before and after sexing, demonstrated significantly reduced fast (A) and slow (B) progressively motile sperm (p < 0.05) after sexing. Sexed-sperm also revealed significantly less hyperactivated sperm (p < 0.05). As shown by time-lapse videomicroscopy of in vitro produced embryos (n = 360), embryos derived from sexed-sperm displayed significantly increased incidences of arrest at the 4-cell stage (p < 0.05). The relative risk for shrinkage/fusion of blastomeres with subsequent lysis was 1.71 times higher in the embryos derived from sexed-sperm as compared to conventional embryos (p < 0.05) resulting in significantly reduced blastocyst rates (p < 0.001). The relative risk for cleavage was 2.36 times lower in the embryos derived from sex-sorted sperm (p < 0.001). Additionally, sexedsperm-derived embryos showed reduced survival times (hazard ratio HR = 1.54, p < 0.001) which were bull dependent (p < 0.001). However, the percentage of apoptotic cells was similar to conventional embryos. Furthermore, embryos derived from sexed-sperm were found to reach developmental stages at similar timings as conventional embryos. our results suggest that reduced conception rates after sexing are due to altered sperm morphokinetics, decreasing the chance of sperm to reach and fertilise the oocyte, and aberrant early embryonic development.Flow cytometric sorting of spermatozoa is based on differences in the amount of DNA between X and Y bearing sperm, which is detected using the DNA-binding stain Hoechst 33342 1-3 . Due to low sperm numbers, sexed-sperm were primarily first used for in vitro fertilization (IVF) 4-6 . Further adaptions at Colorado State University enabled greater sorting efficiency, with the first commercial license for sexed-sperm use in artificial insemination (AI) issued in 2003 7 .The use of AI has grown to over 130 million artificial inseminations in the dairy industry worldwide annually, with 6% of those being sexed-sperm. In heifers, sexed-sperm accounted for 1.4%, of all registered US Holstein breedings in 2006, 9.5% in 2007 and 17.8% in 2008. In cows in the US, sexed-sperm were used in 0.1% of all breedings in 2006, 0.2% in 2007 and 0.4% in 2008 8 . In 2016, more than 4.5 million straws of sexed semen were processed in the US, over 90% being of dairy sire origin 9 . This increased demand in the dairy industry is because male calves are of low economic value and are associated with a higher risk of dystocia compared to heifer calves 8,10 . Additionally, the use of sexed-sperm in AI enables faster herd expansion, shortened generation intervals and an increased rate of genetic gain 11,12 .Despite the economic advantages of the use of sexed-semen, its routine use has been limited to da...

No abstract

Purpose To study whether members of the miR-290-295 cluster in spent culture medium (SCM) of embryos are correlated with morphokinetics and apoptosis. Methods Cryopreserved 1-cell stage mouse embryos were cultured to the blastocyst stage, development was monitored by time-lapse, 59 SCM were collected, and miR-291a and miR-294 were detected with polymerase chain reaction (PCR). Blastocysts were immuno-stained for sexing (H2AK119ub) and for apoptosis (TUNEL). Each embryo and SCM were individually processed. Correlations were run between the miRNAs and developmental events (t2, t3, t4, t5, t8, tSB, tB, ECC2, ECC3, s2, s3, dB) and apoptosis (apoptotic cells/total cell number %). MiR-294 SCM and cell levels were compared in 40 blastocysts. Apoptosis was induced in 15 blastocysts with UV radiation and SCM samples were analyzed for miR-294. Results MiR-291a and miR-294 are released in variable levels by mouse blastocysts. Their release is similar between male and female embryos. No significant correlations were found between these miRNAs and development. MiR-294 was significantly positively correlated with apoptosis ( r = 0.560, p < 0.001). Cellular expression was lower in blastocysts that released miR-294 in high levels compared with null, low, and medium release embryos ( p < 0.01). UV radiation caused apoptosis which triggered higher secretion of miR-294 in 15 blastocysts versus 13 control embryos ( p < 0.01). Conclusion(s) MicroRNAs are important regulators of preimplantation development. Apoptosis triggers the release of miR-294 by blastocysts which possibly serves a secretory role for embryo-maternal communication. SCM miRNA analysis is possible for individually cultured embryos and future studies can investigate miRNAs as noninvasive markers of embryo quality. Electronic supplementary material The online version of this article (10.1007/s10815-020-01796-5) contains supplementary material, which is available to authorized users.