Biological Processes that Prepare Mammalian Spermatozoa to Interact with an Egg and Fertilize It

Mammalian embryo culture media: now and into the future

For over 70years, since the culture of the first mammalian embryo in vitro , scientists have undertaken studies to devise and optimise media to support the manipulation and culture of gametes and embryos. This area of research became especially active in the late 1970s onwards following the successful birth of the first human in vitro fertilised embryo. This review summarises some of the key advances in mammalian embryo culture media over time based on a greater understanding of the biochemical milieu of the reproductive tract. It highlights how learnings from studies in mice and agricultural species have informed human culture media compositions, in particular the inclusion of albumin, growth factors, cytokines, and antioxidants into contemporary culture media formulations, and how these advances may then in turn help to inform and guide development of in vitro culture systems used in other arenas, in particular agriculture. Additionally, it will highlight how the introduction of new technologies, such as timelapse, can influence current trends in media composition and usage that may see a return to a single step medium.

Decreasing sperm quality in mice subjected to chronic cannabidiol exposure: New insights of cannabidiol-mediated male reproductive toxicity

Cannabidiol (CBD) is a natural cannabinoid present in the Cannabis sativa plant, widely prescribed as an anticonvulsant drug, especially for pediatric use. However, its effects on male reproduction are still little investigated. Therefore, the present study assessed the effects of CBD on the spermatogenesis and sperm quality. For this, twenty-one-day-old Swiss mice received CBD for 34 consecutive days by gavage at doses of either 15 or 30 mg/kg. Chronic exposure to CBD decreased the frequency of stages VII-VIII and XII of spermatogenesis and an increase in the frequency of stage IX were noted. Furthermore, the seminiferous epithelium height reduced at stage IX and increased at stage XII in both CBD-treated groups. There was a significant rise of sperm DNA damage, while no genotoxic effects were observed in leukocytes. The activities of superoxide dismutase and catalase decreased, while malondialdehyde levels increased in the sperm of mice treated with a higher dose of CBD. Mice exposed to 30 mg/kg of CBD showed a reduction in the mobile spermatozoa percentage and in curvilinear velocity, while straight line and average path velocity decreased in both treated groups. The number of acrosome-intact spermatozoa declined in the CBD 30 group, and the number of abnormal acrosomes raised in both CBD groups. On the other hand, the weight of reproductive organs, sperm count, and hormone levels were not affected by CBD treatment. These findings show that dysregulation of the endocannabinoid system by CBD can reduce sperm quality. The mechanisms responsible may be associated with disorders during spermatogenesis, especially during the final stages of nuclear remodelling and assembly of acrosome. However, changes in mitochondrial function, as well as the reduction on the antioxidant enzyme activities during epididymal transit, at least partly, may also be involved.

Deficiency in Sperm-Egg Protein Interaction as a Major Cause of Fertilization Failure

Complete elucidation of fertilization process at molecular level is one of the unresolved challenges in sexual reproduction studies, and understanding the molecular mechanism is crucial in overcoming difficulties in infertility and unsuccessful in vitro fertilization. Sperm-oocyte interaction is one of the most remarkable events in fertilization process, and deficiency in protein-protein interactions which mediate this interaction is a major cause of unexplained infertility. Due to detection of how the various defects of sperm-oocyte interaction can affect fertilization failure, different experimental methods have been applied. This review summarizes the current understanding of sperm-egg interaction mechanism during fertilization and also accumulates the different types of sperm-egg interaction abnormalities and their association with infertility. Several detection approaches regarding sperm-egg protein interactions and the associated defects are reviewed in this paper.

Assessment of Pradosia huberi effects on the reproductive system of male rats

Pradosia huberi is a species found in the Amazon region and used as an antiulcerogenic and gastroprotective agent; however, phytochemical analysis has revealed the presence of compounds with potential toxic effects on the reproductive system. For the evaluation of the toxicity of P. huberi on male fertility, male Wistar rats were divided into four groups: one control (distilled water p.o.) and three treated (hydroalcoholic extract of the stem bark of P. Huberi (PH-HAE) at doses of 1.22, 6.1, and 30.5 mg/kg p.o.) once daily, for 63 days. In the last week of treatment (from the 57th to the 63rd day), the rats were mated with untreated virgin females (n = 30/group) and were killed on day 64. To investigate the toxic potential of PH-HAE on the reproductive system of rats the following parameters were evaluated: sperm production, genotoxicity, and general development. The production of gametes and their morphology did not differ between control and treated groups. Treatment with PH-HAE did not result in fewer vaginal plugs formed, indicating that the ability to mate was not impaired, but caused an increase of 14.3 and 10.8% in the preimplantation loss index, a reduction of 14.3 and 10.8% in the implantation index, and a reduction of 5.6 and 8.2% in the postimplantation loss index of female rats mated with rats treated with 6.1 and 30.5 mg/kg, respectively, indicating a possible toxic action of PH-HAE on the reproductive system of rats.