Semen quality assessments and their significance in reproductive technology

Seminal cell-free DNA as a potential marker for in vitro fertility of Nellore bulls

PURPOSE

This study aimed to identify a marker for freezability and in vitro fertility of sperm samples before freezing.

METHODS

Semen was collected from nine Nelore bulls; half of the ejaculate was used for seminal plasma cell-free DNA (cfDNA) quantification, and the other half was cryopreserved. Evaluation of sperm movement using computer-assisted semen analysis and plasma membrane integrity and stability, acrosomal integrity, apoptosis, and mitochondrial potential using flow cytometry were performed on fresh and frozen/thawed semen at 0, 3, 6, and 12 h after thawing. Frozen/thawed sperm was also used for in vitro embryo production. cfDNA was extracted from each bull, and the total DNA and number of cell-free mitochondrial DNA (cfmtDNA) copies were quantified. Semen from each animal was used for IVF, and cleavage, blastocyst formation, and cell counts were evaluated.

RESULTS

Two groups were formed and compared based on the concentrations of cfDNA and cfmDNA present: low-cfDNA and high-cfDNA and low-cfmtDNA and high-cfmtDNA. Up to 12 h post-thawing, there were no differences between the groups in the majority of the sperm parameters evaluated. Cleavage, day 6 and 7 blastocyst rates, and the number of cells were higher in the high cfDNA group than in the low cfDNA group. Similar results were observed for cfmtDNA, except for the number of cells, which was similar between the groups.

CONCLUSION

The concentration of cfDNA and the relative number of copies of cfmtDNA in seminal plasma cannot predict the freezability of semen but can be used to predict in vitro embryo production.

Impact of semen-derived amyloid (SEVI) on sperm viability and motility: its implication in male reproductive fitness

Human semen contains a large number of macromolecules, including proteins/enzymes and carbohydrates, regulating and protecting sperm cells. Proteomic analysis of human seminal fluid led to the discovery of semen amyloids derived from short peptide fragments of the proteins prostatic acid phosphatase (PAP) and semenogelin (SG) which are known to play a crucial role in enhancing HIV infection. However, the relevance of their existence in human semen and role in maintaining sperm behavior remains unclear. Distinct physiological, biochemical, and biophysical attributes might cause these amyloids to influence sperm behavior positively or negatively, affecting fertilization or other reproductive processes. We assessed the direct effect of amyloids derived from a PAP_248-286 fragment, on sperm motility and viability, which are crucial parameters for assessment of sperm quality in semen. Co-incubation of human sperm with PAP_248-286 amyloids at normal physiological concentrations formed in buffer led to significant reduction in sperm viability, though approximately a 10× higher concentration was needed to show a similar effect with amyloid formed in seminal fluid. Both forms of PAP_248-286 amyloid also had a significant impact on sperm motility at physiological levels, in agreement with a previous report. Our study suggests that PAP_248-286 amyloids can directly influence sperm motility and viability in a concentration-dependent manner. We hypothesise that the direct toxic effect of PAP_248-286 amyloid is normally mitigated by other seminal fluid ingredients, but that in pathological conditions, where PAP_248-286 concentrations are elevated and it plays a role in determining sperm health and viability, with relevance for male fertility as well as sterility.