The role of L-type calcium channels in mouse oocyte maturation, activation and early embryonic development

Flavopiridol inhibits oocyte maturation, reduces oocyte quality and blocks cumulus cell function

Flavopiridol (FP) is a plant-derived flavonoidis and used to treat cancers, fungal infections and inflammation-related diseases. However, it is not clear whether it has side effects on the female reproductive system. In this study, we aimed to investigate the toxic effects and potential underlying mechanisms of FP on oocyte maturation and cumulus cell expansion in mice. Cumulus-oocyte complexes (COCs) were cultured in vitro with FP of gradient concentration (50-1000nM), according to the plasma concentration of FP in the clinical trial. The maturation rate and cumulus expansion index of oocytes were counted and studied by immunofluorescence staining, qRT-PCR, oocyte chromosome preparation and so on. The results showed that the FP-exposed COCs inhibited the oocyte maturation and cumulus cell expansion, leading to cell apoptosis in a dose dependent way. Oocytes exposed to 500nM FP showed abnormalities in the spindle structure and chromosome arrangement, ultimately leading to the oocyte maturation arrest and aneuploidy. This may be due to the excessive oxidative stress caused by mitochondrial membrane potential damage and mislocalization. Therefore, when FP is used for cancer treatment, its side effects on the female reproductive system should be seriously considered.

Early embryonic failure caused by a novel mutation in the TUBB8 gene: A case report

BACKGROUND

This study aimed to explore the relationship between gene mutations and early embryonic development arrest and to provide more possibilities for the diagnosis and treatment of repeated implantation failure.

CASE SUMMARY

Here, we collected and described the clinical data of a patient with early embryonic development stagnation after repeated in vitro fertilization attempts for primary infertility at the Department Reproductive Center of Zaozhuang Maternal and Child Healthcare Hospital. We also detected the whole-exon gene of the patient's spouse and parents, and conducted bioinformatics analysis to determine the pathogenesis of the gene.

CONCLUSION

A novel mutant of the TUBB8 gene [c.602G>T(p.C201F)] was identified, and this mutant provided new data on the genotype-phenotype relationships of related diseases.

Aflatoxin B1 impairs porcine oocyte quality via disturbing intracellular membrane system and ATP production

Aflatoxin is the most common type of mycotoxins in contaminated corn, peanuts and rice, which affects the livestock and ultimately endangers human health. Aflatoxin is reported to have carcinogenicity, mutation, growth retardation, immunosuppression and reproductive toxicity. In present study we reported the causes for the declined porcine oocyte quality under aflatoxin exposure. We set up an in vitro exposure model and showed that aflatoxin B1 disturbed cumulus cell expansion and oocyte polar body extrusion. We found that aflatoxin B1 exposure disrupted ER distribution and elevated the expression of GRP78, indicating the occurrence of ER stress, and the increased calcium storage also confirmed this. Besides, the structure of cis-Golgi apparatus, another intracellular membrane system was also affected, showing with decreased GM130 expression. The oocytes under aflatoxin B1 exposure showed aberrant lysosome accumulation and higher LAMP2 expression, a marker for lysosome membrane protection, and this might be due to the aberrant mitochondria function with low ATP production and the increase of apoptosis, since we found that BAX expression increased, and ribosomal protein which is also an apoptosis-related factor RPS3 decreased. Taken together, our study revealed that aflatoxin B1 impairs intracellular membrane system ER, Golgi apparatus, lysosome and mitochondria function to affect porcine oocyte maturation quality.

4-vinylcyclohexene diepoxide induces apoptosis by excessive reactive oxygen species and DNA damage in human ovarian granulosa cells

4-Vinylcyclohexene diepoxide (VCD) is a hazardous industrial material which is widely used in the production of fragrances, rubber tires, antioxidants, pesticides, flame retardants and plasticizers. Previous studies have shown that exposure to VCD damages the female reproductive system, but the effects and mechanisms of VCD exposure on human granulosa cells are not reported. In this study, we used a human granulosa cell line (SVOG) to explore the effects of VCD exposure and found that VCD exposure had toxic effects on SVOG cells in vitro. VCD exposure led to excessive accumulation of intracellular ROS, caused DNA damage in cells, altered the expression of some key genes related with apoptosis and oxidative stress, and ultimately inhibited the proliferative capacity of granulosa cells, resulting in increased apoptosis. Overall, our findings provide solid evidence showing that VCD exposure produces severe damage to human granulosa cells, which is helpful for understanding the reproductive toxicity of VCD and etiology of infertility.

Disruption in ACTL7A causes acrosomal ultrastructural defects in human and mouse sperm as a novel male factor inducing early embryonic arrest

Early embryonic arrest is a challenge for in vitro fertilization (IVF). No genetic factors were previously revealed in the sperm-derived arrest of embryonic development. Here, we reported two infertile brothers presenting normal in conventional semen analysis, but both couples had no embryos for transfer after several IVF and intracytoplasmic sperm injection (ICSI). Whole-exome sequencing identified a homozygous missense mutation of ACTL7A in both brothers. This mutation is deleterious and causes sperm acrosomal ultrastructural defects. The Actl7a knock-in mouse model was generated, and male mutated mice showed sperm acrosomal defects, which were completely consistent with the observations in patients. Furthermore, the sperm from ACTL7A/Actl7a-mutated men and mice showed reduced expression and abnormal localization of PLCζ as a potential cause of embryonic arrest and failure of fertilization. Artificial oocyte activation could successfully overcome the Actl7a-mutated sperm-derived infertility, which is meaningful in the future practice of IVF/ICSI for the ACTL7A-associated male infertility.

β-carotene improves oocyte development and maturation under oxidative stress in vitro

Recently, the mean maternal age at first birth has been continuing to increase. The decline in the age-related fertility is due to the reduction in the number and the quality of the oocyte. An elevation in intra-ovarian reactive oxygen species (ROS) is correlated with the increase in maternal age, and the oxidative stress is involved in the decline in oocyte quality. Although β-carotene, a very effective quencher of ROS, has been found to have the beneficial contribution to the ovarian development and steroidogenesis, it is unknown the effect of β-carotene on the oocyte development especially oocyte maturation. This investigation aimed to explore the beneficial contribution of β-carotene on oocyte maturation under oxidative stress and the underlying mechanism. We found that the oxidative stress induced by ROS reagent Rosup inhibited oocyte development/maturation and parthenogenetic activation which could be dramatically rescued by β-carotene (57.1 ± 4.7% vs 78.9 ± 3.8%; p < 0.05) in vitro. The underlying mechanisms include that β-carotene not only reduces ROS formation and cell apoptosis, but also it can restore actin expression, cortical granule-free domain (CGFD) formation, mitochondria homogeneous distribution, and nuclear maturation. The data suggest that β-carotene acts as a potential antioxidant in the oocyte. Therefore, the findings from this investigation provide the fundamental 7knowledge for using β-carotene as an antioxidant to improve the oocyte quality and even the ovarian function.

Toxic effects and possible mechanisms following malathion exposure in porcine granulosa cells

Malathion is a wide spectrum organophosphorothionate insecticide that is frequently found in drinking water, food and foodstuffs. Ovarian granulosa cells modulate oogenesis by providing metabolic nutrients to oocytes. They can decide the fate of folliculogenesis and oocyte maturation by supplying regulatory cues that help in reproduction. However, little is known about the underlying mechanisms of malathion as a reproductive toxicant in porcine granulosa cells. In the present study, we found that malathion has obvious toxic effects on cultured porcine granulosa cells in a dose-dependent manner. Malathion exposure resulted in significantly increased oxidative stress levels and DNA damage response, which was measured by the mRNA expression levels of homologous recombination (HR) pathway and non-homologous end-joining (NHEJ) pathway-related genes. Subsequently, it was found that malathion exposure could induce apoptosis and autophagy by qRT-PCR and fluorescence intensity analysis. In conclusion, malathion is a reproductive toxicant by inhibiting granulosa cell proliferation by multiple pathways connected to oxidative stress, DNA damage, apoptosis and autophagy.

Tributyltin oxide exposure impairs mouse oocyte maturation and its possible mechanisms

Tributyltin oxide (TBTO) has been widely used as marine antifouling composition, preservative, biocide, and a stabilizer in plastic industry. Previous studies have indicated that TBTO can cause immunotoxicity as an environmental pollutant. However, little is known about its reproductive toxicity, especially on female oocyte maturation and the underlying mechanisms. In this study, mouse oocytes were cultured with different concentrations of TBTO in vitro, and several crucial events during meiotic maturation were evaluated. We found that the first polar body extrusion rate was significantly reduced, which reflected the disruption of meiotic maturation. The rate of abnormal spindle organization increased significantly, accompanied with a higher rate of chromosome misalignment. In addition, TBTO treatment increased reactive oxygen species generation markedly, which also accelerated the early-stage apoptosis. Moreover, heterogeneous mitochondrial distribution, mitochondrial dysfunction, and higher rate of aneuploidy were detected, which consequently disrupted in vitro fertilization. In conclusion, our results indicated that TBTO exposure could impair mouse oocyte maturation by affecting spindle organization, chromosome alignment, mitochondria functions, oxidative stress, and apoptosis.