Sperm aminopeptidase N identifies the potential for high-quality blastocysts and viable embryos in oocyte-donation cycles

STUDY QUESTION

Is there a relationship between human sperm aminopeptidase N (APN) and embryo development in humans?

SUMMARY ANSWER

Human sperm APN could possibly become a new molecular biomarker for identifying the potential for high-quality and usable embryos.

WHAT IS KNOWN ALREADY

The diagnosis of male fertility is one of the major concerns of reproductive medicine. Approximately 30-40% of men with otherwise normal fertility parameters are still unable to achieve pregnancy. The predictive clinical value of semen analysis to identify fertile or infertile males is limited; therefore, new diagnostic methodologies for sperm are urgently required. Sperm APN may be a relevant molecular marker due to its high concentration in sperm cells and its important roles in sperm physiology, such as its functions in motility, acrosome reaction and embryo development.

STUDY DESIGN, SIZE, DURATION

This study included 81 couples who underwent oocyte-donation cycles at Clínica IVI Bilbao (Spain), yielding 611 embryos, between September 2014 and July 2015.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was conducted in an assisted reproduction unit and an academic research laboratory. All the semen samples were examined and classified following World Health Organization guidelines. Spermatozoa were isolated from semen using the discontinuous colloidal silica gradient (45-90%) technique. Embryo quality and development were determined according to the Spanish Association of Reproduction Biology Studies (ASEBIR) criteria. Human sperm APN levels were analyzed by quantitative and semiquantitative flow cytometry.

MAIN RESULTS AND THE ROLE OF CHANCE

The most well-developed and usable blastocysts were associated with low sperm APN levels. Semen samples that had lower APN levels generated more expanded, hatched and usable blastocysts and fewer early, arrested and non-usable blastocysts. The cumulative probability of having well-developed blastocysts increased by 1.38-fold at Day 5 and 1.90-fold at Day 6 of embryo development, and the likelihood of having usable embryos increased by 1.48-fold, when semen samples with low APN levels were used during the ICSI technique.

LIMITATIONS, REASONS FOR CAUTION

The data were obtained from a single fertility clinic. A multicentre study will be required to confirm the results.

WIDER IMPLICATIONS OF THE FINDINGS

Human sperm APN has the potential to become a new molecular biomarker to help identify the potential for high-quality embryos and diagnose male infertility, especially when seminal parameters are close to the threshold values. It could be a crucial tool for couples for whom the number of usable blastocysts is critical for ART success.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Basque Government (GIC15/165) and the University of the Basque Country (UPV/EHU) (EHUA14/17). The authors declare that they have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Reproductive characteristics, semen quality, seminal oxidative status, steroid hormones, sperm production efficiency of rabbits fed herbal supplements

Today, orthodox medicine has almost exceeded its limits in resolving subfertility problems in animals, thus making phytomedicine a primary tool in the treatment of infertility. In this work, three herbal supplements obtained from freshly air-dried Moringa oleifera, Phyllanthus amarus and Viscum album leaves were evaluated to ascertain their comparative effect on the reproductive potentials of bucks. Sixty bucks were allotted four diets made up of standard grower rabbit ration without supplement and with 5% Moringa, Mistletoe and Phyllanthus supplementation for 84 days. Semen samples were collected from all bucks using artificial vagina, for semen quality and seminal oxidative stress markers. The organ weights, testicular and epididymal spermatozoa reserves were assessed to determine sperm production potentials using standard procedures. The result obtained revealed that spermatozoa concentration, progressive motility, curvilinear velocity, average path velocity and the amplitude of lateral head was significantly (p < 0.05) higher in the group fed with mistletoe supplemented diet compared to that recorded in the control groups. The inclusion of herbal supplements linearly (p < 0.05) increased the seminal total antioxidant activity with a corresponding decrease in the seminal lipid peroxidation across the herbal supplemented treatments compared to the control. The gonadal and extra-gonadal sperm reserves of bucks fed on the herbal supplements were depleted compared to bucks on control. Bucks on mistletoe supplementation rivalled the superior daily sperm production and testicular sperm reserve in bucks without herbal supplements. In conclusion, Viscum album supplements in bucks' diets encouraged daily sperm production, testicular sperm reserves, testosterone, as well as spermatozoa kinetics. The three herbal supplements did enhance semen oxidative stability.

Evaluation of dextran for rabbit sperm cryopreservation: Effect on frozen-thawed rabbit sperm quality variables and reproductive performance

Effects were analysed of dextran supplementation to Me₂SO and acetamide rabbit semen freezing extenders on quality characteristics of rabbit spermatozoa and reproductive performance. The final concentration of cryoprotectants in pooled semen samples was 12.4 % Me₂SO for the A extenders, 10.7 % Me₂SO and 2.9 % acetamide for the D extenders and 8.9 % Me₂SO and 2.9 % acetamide in F extenders, with a supplementation of 1.7 % sucrose in all cases. There was not inclusion of dextran in the A0, D0, F0; while 5 % dextran was included in A5, D5, F5 and 10 % dextran in A10, D10 and F10 extenders. Sperm motility and viability rates were similar with use of the different extenders. Acrosome integrity after the freeze-thawing processes, however, was markedly greater when there was dextran supplementation of D and F extenders. Prolificacy was affected by extender composition. When there was artificial insemination (AI) using semen cryopreserved in the A extenders, number of kits born was similar to when there was AI with fresh semen when there was inclusion of 5% dextran for cryopreservation, while there was no effect on prolificacy when there was cryopreservation of semen using the D and F extenders. In conclusion, dextran supplementation of extenders containing Me₂SO and acetamide resulted in greater acrosome integrity. Furthermore, when there was AI using sperm preserved in cryo-diluents containing an intermediate concentration of Me₂SO, combined with inclusion of 5 % dextran, there was a marked beneficial effect on rabbit doe reproductive performance.

Effects of dietary plant polyphenols and seaweed extract mixture on male-rabbit semen: Quality traits and antioxidant markers

Feed additive consisting of polysaccharides from brown seaweeds plus phenolic acid, hydroxycinnamic acids, tannins, and flavonoids from plant extracts, was used as rabbit food supplement. Main aim of the study was to determine the effect of natural mix of marine and freshwater seaweed polyphenols on selected reproductive characteristics of male rabbits during the 90-days experiment. Natural mix was incorporated in feed-pellets for rabbits in two different concentrations - 0.3% (T1 group) and 0.6% (T2 group), compared with a control group (C group). In experimental groups a significant increase of concentration of calcium during first 30 days of supplementation was found. An increase of alanine aminotransferase, glutathione peroxidase and ferric reducing ability of plasma and a decrease in aspartate aminotransferase after 90 days were recorded in the same groups. Except for that we noticed decrease of semen distance of curved line and velocity of curved line after 30 days though only while being supplemented with 0.6% proportion of seaweed polyphenols in feed mixture. Based on the results it can be stated that the natural mix in the tested levels do not show adverse effect on male rabbit reproductive parameters, and an improvement of antioxidant status was observed. The feed additives can have a very important effect on growth, health and development of animals in general as it supplies the with the much-needed minerals, nutritional substances and antioxidants, on which we focused in our study.

Effect of Aminopeptidase N on functions and fertility of mouse spermatozoa in vitro

Aminopeptidase N (APN) is defined as a multifunctional enzyme, which regulate cellular physiology of a wide variety of cells in human. Earlier studies reported that mammalian semen shares this common enzyme as a major protein of seminal plasma that has correlation with male fertility, while the regulatory mechanisms of APN in spermatozoa are still far from being well understood. Present study was designed to investigate the role of APN in biological and chemical functions of spermatozoa using an in vitro antagonistic approach. Results showed that lower APN activity in sperm culture medium significantly increased sperm motility and the percentage of high speed spermatozoa and decreased the percentage of slow speed spermatozoa after a dose dependent inhibitor treatment (10, 100, and 1000 μM leuhistin) on epididymal mouse spermatozoa in a capacitating media for 90 min. Both 100 μM and 1000 μM decreased APN activity, while only 1000 μM decreased cell viability and increased PKA activity significantly compared to control. Nonetheless capacitation status, acrosome reaction status, and lactate dehydrogenase activity were not affected. Intriguingly, the treatment affected embryonic development through decreasing tyrosine phosphorylation of proteins and increasing reactive oxygen species levels. Further in silico analysis revealed associated regulatory proteins, which have critical functional role for male fertility.

Elevated aminopeptidase N affects sperm motility and early embryo development

Aminopeptidase N (APN) is a naturally occurring ectopeptidase present in mammalian semen. Previous studies have demonstrated that APN adversely affects male fertility through the alteration of sperm motility. This enzyme constitutes 0.5 to 1% of the seminal plasma proteins, which can be transferred from the prostasomes to sperms by a fusion process. In the present study, we investigated the molecular mechanism of action of APN and its role in regulating sperm functions and male fertility. In this in vitro study, epididymal mouse spermatozoa were incubated in a capacitating media (pH 7) containing 20 ng/mL of recombinant mouse APN for 90 min. Our results demonstrated that the supplementation of recombinant APN in sperm culture medium significantly increased APN activity, and subsequently altered motility, hyperactivated motility, rapid and medium swimming speeds, viability, and the acrosome reaction of mouse spermatozoa. These effects were potentially caused by increased toxicity in the spermatozoa. Further, altered APN activity in sperm culture medium affected early embryonic development. Interestingly, the effect of elevated APN activity in sperm culture medium was independent of protein tyrosine phosphorylation and protein kinase A activity. On the basis of these results, we concluded that APN plays a significant role in the regulation of several sperm functions and early embryonic development. In addition, increased APN activity could potentially lead to several adverse consequences related to male fertility.