Effect of perfluorodecanoic acid on pig oocyte viability, intracellular calcium levels and gap junction intercellular communication during oocyte maturation in vitro

Perfluoroalkyl and polyfluoroalkyl substances and Cancer risk: results from a dose-response Meta-analysis

Background

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent organic pollutants in the environment. While some studies suggest that PFASs may contribute to cancer development, the link between PFAS exposure and cancer risk remains debated.

Methods

This dose-response meta-analysis explores the relationship between PFASs and cancer. It employs odds ratio (OR) and standardized mean difference (SMD), along with their 95% confidence interval (CI), to assess the effects of PFASs on cancer risk. Relevant studies were sourced from Web of Science, PubMed, Embase, Medline, and CNKI databases. The dose-response relationship was assessed by the fixed-effects model and least-squares regression.

Results

Forty studies, involving a total of 748,188 participants, were included in this meta-analysis. Out of these, 13 studies were specifically analyzed for the dose-response relationship. Findings revealed that exposure to PFASs, especially PFDA, significantly raises the risk of genitourinary cancers, and PFDA exposure shows a dose-dependent increase in overall and breast cancer risk. Additionally, PFOS exposure is associated with an increased cancer risk, and elevated PFOA levels were significantly observed in breast cancer patients.

Conclusions

The findings suggest that PFAS exposure is a potential cancer risk factor, with the carcinogenic potential of PFDA being dose-dependent.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40201-024-00899-w.

Perfluoroalkyl and Polyfluoroalkyl Substances in Relation to the Participant-Reported Total Pregnancy and Live Birth Numbers among Reproductive-Aged Women in the United States

Perfluoroalkyl and polyfluoroalkyl substances (PFASs), widely utilized in various industries, may pose potential reproductive well-being risks. However, the research on the impact of PFAS exposures on pregnancy and live birth rates remains scarce. To address this gap, we conducted a cross-sectional study using the data from the United States National Health and Nutrition Examination Survey (NHANES) collected between 2013 and 2018. We focused on six PFAS compounds measured in the serum of women aged 20 to 50 years, employing the Poisson regression, Quantile G-composition (Qgcomp), and Weighted Quantile Sum (WQS) regression models. Adjusting for age, racial/ethnic origin, educational level, marital status, family income, body mass index (BMI), menarche age, birth control pill use, and other female hormone consumption, the Poisson regression identified significant negative associations between the individual PFAS exposures and pregnancy and live birth numbers (p < 0.05 for all 24 null hypotheses for which the slope of the trend line is zero). The Qgcomp analysis indicated that a one-quartile increase in the mixed PFAS exposures was associated with reductions of 0.09 (95% CI: -0.15, -0.03) in the pregnancy numbers and 0.12 (95% CI: -0.19, -0.05) in the live birth numbers. Similarly, the WQS analysis revealed that a unit increase in the WQS index corresponded to decreases of 0.14 (95% CI: -0.20, -0.07) in the pregnancy numbers and 0.14 (95% CI: -0.21, -0.06) in the live birth numbers. Among the six specific PFAS compounds we studied, perfluorononanoic acid (PFNA) had the most negative association with the pregnancy and live birth numbers. In conclusion, our findings suggest that PFAS exposures are associated with lower pregnancy and live birth numbers among women of reproductive age.

Calcium signaling in oocyte quality and functionality and its application

Calcium (Ca2+) is a second messenger for many signal pathways, and changes in intracellular Ca2+ concentration ([Ca2+]i) are an important signaling mechanism in the oocyte maturation, activation, fertilization, function regulation of granulosa and cumulus cells and offspring development. Ca2+ oscillations occur during oocyte maturation and fertilization, which are maintained by Ca2+ stores and extracellular Ca2+ ([Ca2+]e). Abnormalities in Ca2+ signaling can affect the release of the first polar body, the first meiotic division, and chromosome and spindle morphology. Well-studied aspects of Ca2+ signaling in the oocyte are oocyte activation and fertilization. Oocyte activation, driven by sperm-specific phospholipase PLCζ, is initiated by concerted intracellular patterns of Ca2+ release, termed Ca2+ oscillations. Ca2+ oscillations persist for a long time during fertilization and are coordinately engaged by a variety of Ca2+ channels, pumps, regulatory proteins and their partners. Calcium signaling also regulates granulosa and cumulus cells' function, which further affects oocyte maturation and fertilization outcome. Clinically, there are several physical and chemical options for treating fertilization failure through oocyte activation. Additionally, various exogenous compounds or drugs can cause ovarian dysfunction and female infertility by inducing abnormal Ca2+ signaling or Ca2+ dyshomeostasis in oocytes and granulosa cells. Therefore, the reproductive health risks caused by adverse stresses should arouse our attention. This review will systematically summarize the latest research progress on the aforementioned aspects and propose further research directions on calcium signaling in female reproduction.

Establishing a 3D-cultured system based on alginate-hydrogel embedding benefits the in vitro maturation of porcine Oocytes

The in vitro maturation (IVM) quality of oocytes is directly related to the subsequent developmental potential of embryos and a fundamental of in vitro embryo production. However, conventional IVM methods fail to maintain the gap-junction intercellular communication (GJIC) between cumulus-oocyte complexes (COCs), which leads to insufficient oocyte maturation. Herein, we investigated the effects of three different three-dimensional (3D) culture methods on oocyte development in vitro, optimized of the alginate-hydrogel embedding method, and assessed the effects of the alginate-hydrogel embedding method on subsequent embryonic developmental potential of oocytes after IVM and parthenogenetic activation (PA). The results showed that Matrigel embedding and alginate-hydrogel embedding benefited the embryonic developmental potential of oocytes after IVM and PA. With the further optimization of alginate-hydrogel embedding, including crosslinking and decrosslinking of parameters, we established a 3D culture system that can significantly increase oocyte maturation and the blastocyst rate of embryos after PA (27.2 ± 1.5 vs 36.7 ± 2.8, P < 0.05). This 3D culture system produced oocytes with markedly increased mitochondrial intensity and membrane potential, which reduced the abnormalities of spindle formation and cortical granule distribution. The alginate-hydrogel embedding system can also remarkably enhance the GJIC between COCs. In summary, based on alginate-hydrogel embedding, we established a 3D culture system that can improve the IVM quality of porcine oocytes, possibly by enhancing GJIC.

Fertility loss: negative effects of environmental toxicants on oogenesis

There has been a global decline in fertility rates, with ovulatory disorders emerging as the leading cause, contributing to a global lifetime infertility prevalence of 17.5%. Formation of the primordial follicle pool during early and further development of oocytes after puberty is crucial in determining female fertility and reproductive quality. However, the increasing exposure to environmental toxins (through occupational exposure and ubiquitous chemicals) in daily life is a growing concern; these toxins have been identified as significant risk factors for oogenesis in women. In light of this concern, this review aims to enhance our understanding of female reproductive system diseases and their implications. Specifically, we summarized and categorized the environmental toxins that can affect oogenesis. Here, we provide an overview of oogenesis, highlighting specific stages that may be susceptible to the influence of environmental toxins. Furthermore, we discuss the genetic and molecular mechanisms by which various environmental toxins, including metals, cigarette smoke, and agricultural and industrial toxins, affect female oogenesis. Raising awareness about the potential risks associated with toxin exposure is crucial. However, further research is needed to fully comprehend the mechanisms underlying these effects, including the identification of biomarkers to assess exposure levels and predict reproductive outcomes. By providing a comprehensive overview, this review aims to contribute to a better understanding of the impact of environmental toxins on female oogenesis and guide future research in this field.

Perfluorohexane sulfonate (PFHxS) disturbs the estrous cycle, ovulation rate, oocyte cell communication and calcium homeostasis in mice

Perfluoroalkyl substances are man-made chemicals with ample consumer and industrial applications. They are widely used and are resistant to environmental and metabolic degradation. Several studies have evaluated the effects of Perfluorohexane sulfonate on reproduction. However, there are few reports exploring the cell and molecular mechanisms of its toxicity in the ovary. The aim of this study was to investigate the effects of PFHxS exposure on the estrous cycle, ovulation rate, and the underlying mechanisms of action in female mice in vivo. The animals received a single sub-lethal dose of PFHxS (25.1 mg/kg, 62.5 mg/kg) or vehicle and were stimulated to obtain immature cumulus cell-oocyte complexes (COCs) from the ovaries, or superovulated to develop mature COCs. To evaluate oocyte physiology, Gap-junction intercellular communication (GJIC) was analyzed in immature COCs and calcium homeostasis was evaluated in mature oocytes. PFHxS exposure prolonged the estrous cycle and decreased ovulation rate in female mice. Connexins, Cx43 and Cx37, were downregulated and GJIC was impaired in immature COCs, providing a possible mechanism for the alterations in the estrous cycle and ovulation. No morphological abnormalities were observed in the mature PFHxS-exposed oocytes, but calcium homeostasis was affected. This effect is probably due, at least partially, to deregulation of the endoplasmic reticulum calcium modulator, Stim1. These mechanisms of ovarian injury could explain the reported correlation among PFHxS levels and subfertility in women undergoing fertility treatments.

Effects of perfluorooctanoic acid in oxidative stress generation, DNA damage in cumulus cells, and its impact on in vitro maturation of porcine oocytes

Perfluorooctanoic acid is a synthetic compound mostly used in a wide range of consumer products with several adverse effects on somatic cells and gametes. It has been linked to hepatotoxic and carcinogenic effects, alterations in the immune system, endocrine, and reproductive alterations. In vivo studies show an increase in reactive oxygen species and DNA damage. However, the mechanisms by which this compound affects fertility, remain contradictory. Therefore, the aim of the present study was to evaluate the effect of perfluorooctanoic acid on oocyte viability and maturation, as well as the viability, generation of oxidative stress, and genotoxic damage in the cumulus cells exposed during in vitro maturation. This compound had a negative effect on oocyte viability (lethal concentration, LC₅₀  = 269 μM) and maturation (inhibition maturation concentration IM₅₀  = 75 μM), while in cumulus cells the LC₅₀ was 158 μM. The generation of reactive oxygen species evaluated in cumulus cells, protein carbonylation, and DNA damage, was significantly increased at 40 μM perfluorooctanoic acid. This study provides evidence that perfluorooctanoic acid causes reactive oxygen species generation, protein oxidation, and DNA damage in cumulus cells, compromising the maturation and viability of porcine oocyte, which may affect fertility.

Melatonin improves the maturation and developmental ability of bovine oocytes by up-regulating GJA4 to enhance gap junction intercellular communication

Melatonin (MT) increases oocyte maturation by reducing reactive oxygen species level and enhancing oocyte antioxidant capacity. However, the mechanisms via which MT works are still poorly understood. In the present study, the effects of MT on the maturation rate and development ability of bovine oocytes were investigated. Then, the transcriptome of oocytes treated by MT was sequenced. Finally, the expression of gap junction protein alpha 4 (GJA4) protein and cAMP level were detected in bovine oocytes, and isoprenaline (enhancer of gap junctional intercellular communication (GJIC)) and heptanol (inhibitor of GJIC) were used to investigate the effect of MT on GJIC activity in bovine oocytes. Our results showed that MT significantly improved the maturation, developmental ability and mRNA expression of GJA4 of bovine oocytes. Meanwhile, MT significantly increased GJA4 protein level and cAMP level in bovine oocytes. In contrast to heptanol, both isoproterenol and MT significantly increased GJIC activity, nuclear maturation and the development ability of bovine oocytes. However, MT significantly restored the nuclear maturation and developmental ability of oocytes treated by heptanol. In conclusion, our results showed that MT improves the maturation and developmental ability of bovine oocytes by enhancing GJIC activity via up-regulating GJA4 protein expression in IVM progress.

Perfluorodecanoic acid induces meiotic defects and deterioration of mice oocytes in vitro

Perfluorodecanoic acid (PFDA) is a member of the perfluoroalkyl substances, which are toxic to organic functions. Recently, it has been found in follicular fluid, seriously interfering with reproduction. Follicular fluid provides the oocyte with necessary resources during the process of oocytes maturation. However, the effects of PFDA on the oocyte need investigation. Our study evaluated the impacts of PFDA on the meiosis and development potential of mouse oocytes by exposing oocytes to PFDA in vitro at 350, 400, and 450 μM concentrations. The results showed that exposure to PFDA resulted in the first meiotic prophase arrest by obstructing the function of the maturation-promoting factor. It also induced the dysfunction of the spindle assembly checkpoint, expedited the progression of the first meiotic process, and increased the risk of aneuploidy. The oocytes treated with PFDA had a broken cytoskeleton which also contributed to meiotic maturation failure. Besides, PFDA exposure caused mitochondria defections, increased the reactive oxygen species level in oocytes, and consequently induced oocyte apoptosis. Moreover, PFDA produced epigenetic modifications in oocytes and increased the frequency of mature oocytes with declined development potential. In summary, our data indicated that PFDA disturbs the meiotic process and induces oocyte quality deterioration.

Perfluorooctanoic acid inhibits the maturation rate of mouse oocytes cultured in vitro by triggering mitochondrial and DNA damage

BACKGROUND

Perfluorooctanoic acid (PFOA) is widely used in the manufacture of household and industrial products. It has certain toxicity and leaves many residues in the environment. Numerous studies have shown that PFOA exhibits endocrine disrupting properties and immunotoxicity and induces developmental defects. However, there is very little information regarding its toxicity on oocytes.

METHODS

We cultured denuded oocytes in maturation medium supplemented with 0, 300, or 500 PFOA during IVM and evaluated the maturation of oocytes from the aspects of ROS(DCFH-DA), mitochondria(MitoOrange and JC-1), DNA damage(P-H2AX), and cytoskeleton(β-tubulin).

RESULTS

Compared with the control group, the PFOA treatment group exhibited significantly reduced proportion of oocytes matutation. Furthermore, the DCFH-DA test showed that PFOA significantly increased reactive oxygen species (ROS) levels. PFOA disrupted mitochondrial distribution and decreased mitochondrial function as assessed using MitoOrange and JC-1. In addition, PFOA-treated oocytes exhibited a significantly higher percentage of P-H2AX, defective β-tubulin, abnormal chromosome alignment, lower expression of the anti-apoptotic gene Bcl-2, and higher expression of the apoptotic genes caspase3 and Bax.

CONCLUSION

In summary, PFOA could negatively and directly affect oocyte maturation in vitro and cause oxidative stress, mitochondrial function disruption, DNA damage, cytoskeleton damage, and apoptosis.

Bisphenol S enhances gap junction intercellular communication in ovarian theca cells

Gap junction intercellular communication (GJIC) is necessary for ovarian function, and it is temporospatially regulated during follicular development and ovulation. At outermost layer of the antral follicle, theca cells provide structural, steroidogenic, and vascular support. Inter- and extra-thecal GJIC is required for intrafollicular trafficking of signaling molecules. Because GJIC can be altered by hormones and endocrine disrupting chemicals (EDCs), we tested if any of five common EDCs (bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), perfluorooctanesulfonic acid (PFOS), and triphenyltin chloride (TPT)) can interfere with theca cell GJIC. Since most chemicals are reported to repress GJIC, we hypothesized that all chemicals tested, within environmentally relevant human exposure concentrations, will inhibit theca cell GJICs. To evaluate this hypothesis, we used a scrape loading/dye transfer assay. BPS, but no other chemical tested, enhanced GJIC in a dose- and time-dependent manner in ovine primary theca cells. A signal-protein inhibitor approach was used to explore the GJIC-modulatory pathways involved. Phospholipase C and mitogen-activated protein kinase (MAPK) inhibitors significantly attenuated BPS-induced enhanced GJIC. Human theca cells were used to evaluate translational relevance of these findings. Human primary theca cells had a ∼40% increase in GJIC in response to BPS, which was attenuated with a MAPK inhibitor, suggestive of a conserved mechanism. Upregulation of GJIC could result in hyperplasia of the theca cell layer or prevent ovulation by holding the oocyte in meiotic arrest. Further studies are necessary to understand in vitro to in vivo translatability of these findings on follicle development and fertility outcomes.

Effect of porcine immature oocyte vitrification on oocyte-cumulus cell gap junctional intercellular communication

Vitrification may severely affect cumulus cells and oocyte morphology and viability, limiting their maturation and developmental potential. The aim of this study was to evaluate the gap junction intercellular communication (GJIC) integrity after the vitrification of porcine immature cumulus-oocyte complexes (COCs). Fresh COCs were randomly distributed in three groups: untreated (control), toxicity (cryoprotectants exposure), and vitrification, then subjected to in vitro maturation (IVM). Oocyte viability and IVM were measured in all groups. The evaluation of GJIC was expressed as relative fluorescence intensity (RFI). Vitrification significantly decreased oocyte viability and maturation after 44 h of culture compared to control. Also, significantly reduced RFI was observed in vitrified COCs during the first hours of culture (4-8 h) compared to control. This study demonstrates that porcine oocyte viability and maturation after 44 h of culture decreased after vitrification. GJIC was also affected during the first hours of culture after the vitrification of immature oocytes, being one of the possible mechanisms by which oocyte maturation decreased.

Suicide Gene Therapy Against Malignant Gliomas by the Local Delivery of Genetically Engineered Umbilical Cord Mesenchymal Stem Cells as Cellular Vehicles

BACKGROUND

Glioblastoma (GBM) is a malignant tumor that is difficult to eliminate, and new therapies are thus strongly desired. Mesenchymal stem cells (MSCs) have the ability to locate to injured tissues, inflammation sites and tumors and are thus good candidates for carrying antitumor genes for the treatment of tumors. Treating GBM with MSCs that have been transduced with the herpes simplex virus thymidine kinase (HSV-TK) gene has brought significant advances because MSCs can exert a bystander effect on tumor cells upon treatment with the prodrug ganciclovir (GCV).

OBJECTIVE

In this study, we aimed to determine whether HSV-TK-expressing umbilical cord mesenchymal stem cells (MSCTKs) together with prodrug GCV treatment could exert a bystander killing effect on GBM.

METHODS AND RESULTS

Compared with MSCTK: U87 ratio at 1:10,1:100 and 1:100, GCV concentration at 2.5µM or 250µM, when MSCTKs were cocultured with U87 cells at a ratio of 1:1, 25 µM GCV exerted a more stable killing effect. Higher amounts of MSCTKs cocultured with U87 cells were correlated with a better bystander effect exerted by the MSCTK/GCV system. We built U87-driven subcutaneous tumor models and brain intracranial tumor models to evaluate the efficiency of the MSCTK/GCV system on subcutaneous and intracranial tumors and found that MSCTK/GCV was effective in both models. The ratio of MSCTKs and tumor cells played a critical role in this therapeutic effect, with a higher MSCTK/U87 ratio exerting a better effect.

CONCLUSION

This research suggested that the MSCTK/GCV system exerts a strong bystander effect on GBM tumor cells, and this system may be a promising assistant method for GBM postoperative therapy.

A novel role of SIRT2 in regulating gap junction communications via connexin-43 in bovine cumulus-oocyte complexes

SIRT2, the predominantly cytosolic sirtuin, plays important role in multiple biological processes, including metabolism, stress response, and aging. However, the function of SIRT2 in gap junction intercellular communications (GJICs) of cumulus-oocyte complexes (COCs) is not yet known. The purpose of the present study was to evaluate the effect and underlining mechanism of SIRT2 on GJICs in COCs. Here, we found that treatment with SIRT2 inhibitors (SirReal2 or TM) inhibited bovine oocyte nuclear maturation. Further analysis revealed that SIRT2 inactivation disturbed the GJICs of COCs during in vitro maturation. Correspondingly, both the Cx43 phosphorylation levels and MEK/MER signaling pathways were induced by SIRT2 inhibition. Importantly, SIRT2-mediated Cx43 phosphorylation was completely abolished by treatment with MEK1/2 inhibitor (Trametinib). Furthermore, treatment with SIRT2 inhibitors resulted in the high levels of MEK1/2 acetylation. Functionally, downregulating the MER/ERK pathways with inhibitors (Trametinib or SCH772984) could attenuate the closure of GJICs caused by SIRT2 inactivation in partly. In addition, inhibition of SIRT2 activity significantly decreased the membrane and zona pellucida localization of Cx43 by upregulating the levels of Cx43 acetylation. Taken together, these results demonstrated a novel role that SIRT2 regulates GJICs via modulating the phosphorylation and deacetylation of Cx43 in COCs.