Artificial activation of sperm motility in vitro.

AIM: The sperm activation method is a modern methodological approach that is used more and more often in practice. The number of studies focused on methods of artificial activation of human sperm motility are constantly increasing. Standard sperm selection methods can fail in some cases, among other things, because very young sperm are isolated that have not yet completed their development. In these cases, artificial stimulation of their movement can have a positive effect and greatly facilitate and faster the process of selecting suitable sperm. Methylxanthines are most often used as activating agents. However, opinions on the safety of using these substances on sperm are not uniform. The aim of the thesis is to present current knowledge about artificial activation of sperm motility for in vitro fertilization and subsequent embryonic development. METHODOLOGY: Research of relevant literature in Web of Science, Scopus, PubMed/Medline databases. RESULTS AND CONCLUSION: The literature analysis shows that this method is safe and effective in the selection of immotile spermatozoa. Scientific studies have been conducted to verify the safety and reliability of this method. The conclusion of these studies is the positive impact of this method of selection, especially in cases of sperm obtained from testicular tissue after method testicular sperm extraction. In these cases, the method of artificial sperm activation facilitated and accelerated the selection of sperm before intracytoplasmic sperm injection. Undamaged spermatozoa, which are immobile due to incomplete maturation, were activated.

Assisted oocyte activation.

OBJECTIVE: Currently, there is a rapid increase in studies on assisted oocyte activation, which can significantly improve the process of in vitro fertilization. Fertilization of oocytes by conventional methods and by intracytoplasmic sperm injection can be affected by insufficient activation of the oocyte. The reason is mainly deviations in the enzymatic equipment of sperm or oocytes or a non-functional activation cascade. In many cases, fertilization can be achieved using artificial oocyte activation by applying calcium ion donors to the oocytes after sperm microinjection. However, opinions on the safety and reliability of this method are not uniform. The aim of the thesis is to present current knowledge about assisted oocyte activation and its impact not only on in vitro fertilization, but also on subsequent embryonic and fetal development. METHODOLOGY: Research of relevant literature in Web of Science, PubMed/Medline and Scopus databases. RESULTS AND CONCLUSIONS: Based on the literature data and the authors' own experience, it follows that this method is effective and safe from the point of view of further development of the embryo, fetus and postnatal development. Extensive meta-analyses focused on this method were carried out, which did not find a negative impact not only on the embryonic and fetal development of the individual, but this method did not have associated with a negative impact on the psychosomatic development of the children.

The absence of a DNA replication checkpoint in porcine zygotes.

It has been demonstrated that in the zygotes of some mammals a unique checkpoint controls the onset of DNA replication. Thus, DNA replication begins in the maternal pronucleus only after the paternal pronucleus is fully formed. In our experiments we have investigated whether this checkpoint also operates in porcine zygotes produced either by in vitro fertilization (IVF) or by intracytoplasmic sperm injection (ICSI). Our results show that the onset of DNA replication occurs in the maternal pronucleus even in the presence of an intact sperm head in zygotes produced by ICSI, as well as in polyspermic eggs where some sperm heads are intact or male pronuclei are not yet fully developed. We conclude that in porcine zygotes there is an absence of the DNA replication checkpoint that is typical for some other mammals.

Development of pig embryos after electro-activation and in vitro fertilization in PZM-3 or PZM supplemented with fetal bovine serum.

The aim of present study was to optimize culture conditions for pig embryos. Initially, we evaluated three different basic culture conditions. When embryos from electro-activation (parthenotes) or in vitro fertilization (IVF-embryos) were cultured in PZM supplemented with 3 mg/ml bovine serum albumin (PZM-3) in 4-well dishes, in medium covered with oil in 4-well dishes or in droplets under oil, 0%, 33% and 20% of the parthenotes, and 11%, 23% and 20% of the IVF-embryos developed to blastocysts. Subsequently, we examined the development of embryos when they were cultured in 4-well dishes in medium covered with oil continuously for 7 days or cultured under the same conditions but with a change to fresh medium on Days 2 and 4. In this experiment, 23% (no medium change) and 34% (change) of the parthenotes developed to blastocysts, respectively. When IVF-embryos were cultured under similar conditions, 33% and 38% of the embryos developed to blastocysts. Further improvement was achieved when PZM was supplemented with FBS from Day 4. In this experiment, 47% of the parthenotes developed to blastocysts with an average cell number of 57 +/- 7.7. In IVF-embryo group, 49% of the embryos developed to blastocysts with a mean cell number of 60 +/- 6.1. These results indicate that a change to fresh medium and inclusion of FBS in the medium during the late stages of culture can generate a higher proportion of high-quality blastocysts.

Cryopreservation of isolated mouse germinal vesicles.

The storage of unfertilized oocytes, either immature, maturing or mature, is still unsatisfactory. Here we describe an approach in which germinal vesicles isolated as karyoplasts from immature oocytes are vitrified by open the pulled straws (OPS) method in evacuated porcine zonae pellucidae. After thawing, their survival was almost absolute. Moreover, when thawed GV-karyoplasts were fused to immature oocyte cytoplasts the maturation of reconstructed cells resulted in the production of secondary oocytes--metaphase II.

Effect of caffeine on meiotic maturation of porcine oocytes.

This study was conducted to evaluate the effect of caffeine on the meiotic maturation of porcine oocytes. Oocyte-cumulus complexes were collected from slaughterhouse-derived ovaries and cultured for 24, 32 or 48 h in medium 199 supplemented with 10% fetal calf serum, 10 microg/ml FSH, 50 microg/ml sodium pyruvate and 50 microg/ml gentamicin in the presence or absence of 2.5 mM caffeine. Caffeine inhibited the meiotic resumption of pig oocytes effectively after 24 h of culture, and 95.5% of oocytes were arrested at the germinal vesicle (GV) stage (control 17.8%, p < 0.05). Prolonged culture with caffeine up to 32 h or 48 h, however, resulted in a significant decrease in the inhibitory effect (GV: 13.8% and 8.2%). The number of oocytes at metaphase II after 48 h of culture in the presence of caffeine was significantly lower than that in the control medium (65.3% vs 94.7%, p < 0.05). The withdrawal of caffeine after 24 h of culture resulted in the resumption of meiotic maturation, and the oocytes reached metaphase II after 48 h. However, the ability of caffeine-treated oocytes to develop to blastocysts after artificial activation was lower than that of the control (5.5% vs 9.1%, p < 0.05). Caffeine treatment significantly increased cAMP levels in the oocytes after 24 h of culture, while both Cdc2 kinase and MAP kinase activation were inhibited in the oocytes. These results suggest that caffeine, similarly to other purine derivatives, prolongs the meiotic arrest of porcine oocytes at the GV stage, perhaps by its action of increasing the cAMP level and by the suppression of Cdc2 kinase and MAP kinase activities in the oocytes.