Melatonin ameliorates murine fetal oocyte meiotic dysfunction in F1 and F2 offspring caused by nicotine exposure during pregnancy

Maternal vitamin B1 is a determinant for the fate of primordial follicle formation in offspring

The mediation of maternal-embryonic cross-talk via nutrition and metabolism impacts greatly on offspring health. However, the underlying key interfaces remain elusive. Here, we determined that maternal high-fat diet during pregnancy in mice impaired preservation of the ovarian primordial follicle pool in female offspring, which was concomitant with mitochondrial dysfunction of germ cells. Furthermore, this occurred through a reduction in maternal gut microbiota-related vitamin B1 while the defects were restored via vitamin B1 supplementation. Intriguingly, vitamin B1 promoted acetyl-CoA metabolism in offspring ovaries, contributing to histone acetylation and chromatin accessibility at the promoters of cell cycle-related genes, enhancement of mitochondrial function, and improvement of granulosa cell proliferation. In humans, vitamin B1 is downregulated in the serum of women with gestational diabetes mellitus. In this work, these findings uncover the role of the non-gamete transmission of maternal high-fat diet in influencing offspring oogenic fate. Vitamin B1 could be a promising therapeutic approach for protecting offspring health.

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.

Transcriptomic landscape reveals germline potential of porcine skin-derived multipotent dermal fibroblast progenitors

According to estimations, approximately about 15% of couples worldwide suffer from infertility, in which individuals with azoospermia or oocyte abnormalities cannot be treated with assisted reproductive technology. The skin-derived stem cells (SDSCs) differentiation into primordial germ cell-like cells (PGCLCs) is one of the major breakthroughs in the field of stem cells intervention for infertility treatment in recent years. However, the cellular origin of SDSCs and their dynamic changes in transcription profile during differentiation into PGCLCs in vitro remain largely undissected. Here, the results of single-cell RNA sequencing indicated that porcine SDSCs are mainly derived from multipotent dermal fibroblast progenitors (MDFPs), which are regulated by growth factors (EGF/bFGF). Importantly, porcine SDSCs exhibit pluripotency for differentiating into three germ layers and can effectively differentiate into PGCLCs through complex transcriptional regulation involving histone modification. Moreover, this study also highlights that porcine SDSC-derived PGCLCs specification exhibit conservation with the human primordial germ cells lineage and that its proliferation is mediated by the MAPK signaling pathway. Our findings provide substantial novel insights into the field of regenerative medicine in which stem cells differentiate into germ cells in vitro, as well as potential therapeutic effects in individuals with azoospermia and/or defective oocytes.

Aflatoxin B1 disrupts testicular development via the cell cycle-related Ras/PI3K/Akt signaling in mice and pig

Aflatoxins B1 (AFB1), a type I carcinogen widely present in the environment, not only poses a danger to animal husbandry, but also poses a potential threat to human reproductive health, but its mechanism is still unclear. To address this question, multi-omics were performed on porcine Sertoli cells and mice testis. The data suggest that AFB1 induced testicular damage manifested as decreased expression of GJA1, ZO1 and OCCLUDIN in mice (p < 0.01) and inhibition of porcine Sertoli cell proliferation. Transcriptomic analysis suggested changes in noncoding RNA expression profiles that affect the cell cycle-related Ras/PI3K/Akt signaling pathway after AFB1 exposure both in mice and pigs. Specifically, AFB1 caused abnormal cell cycle of testis with the characterization of decreased expressions of CCNA1, CCNB1 and CDK1 (p < 0.01). Flow cytometry revealed that the G2/M phase was significantly increased after AFB1 exposure. Meanwhile, AFB1 downregulated the expressions of Ras, PI3K and AKT both in porcine Sertoli cell (p < 0.01) and mice testis (p < 0.01). Metabolome analysis verified the alterations in the PI3K/Akt signaling pathway (p < 0.05). Moreover, the joint analysis of metabolome and microbiome found that the changes of metabolites were correlated with the expression of flora. In conclusion, we have demonstrated that AFB1 impairs testicular development via the cell cycle-related Ras/PI3K/Akt signaling.

Hexavalent chromium disrupts the skin barrier by targeting ROS-mediated mitochondrial pathway apoptosis in keratinocytes

Hexavalent chromium (Cr(VI)), a toxic heavy metal, is ubiquitous in daily life. Exposure to this toxic substance in occupational settings can cause dermatitis and cancer. As the body's largest organ, the skin plays a crucial role in protecting the organism against external aggressions. While previous studies have focused on the effects of Cr(VI) on skin inflammation, this study investigates the potential toxicity of Cr(VI) from the skin barrier and integrity perspective. The in vivo results of this study showed that mice exposed to Cr(VI) experienced skin deterioration and hemorrhaging, as well as a reduction in the thickness of the collagen fiber layer. TUNEL and Occludin staining results revealed that Cr(VI)'s toxicity primarily targeted keratinocytes. Experiments in vitro demonstrated that Cr(VI) treatment decreased the activity of HaCaT cells, altered cell morphology, and increased LDH secretion. Further research revealed that Cr(VI) could modify membrane permeability, impair membrane integrity, and reduce the protein expression of ZO-1 and Occludin. In addition, it was discovered that Cr(VI) promoted cell apoptosis and inhibited AKT activation. However, the addition of a caspase inhibitor and an AKT activator prevented Cr(VI)-induced injury to the cell membrane barrier, indicating that apoptosis plays a crucial role in this process. The addition of three apoptotic pathway inhibitors, confirmed that Cr(VI) damaged the cell barrier through ROS-mediated mitochondrial pathway apoptosis. Moreover, the use of a ROS inhibitor significantly reduced Cr(VI)-induced apoptosis and cell barrier injury. In conclusion, this study provides an experimental foundation for the treatment of skin injury caused by Cr(VI).

Melatonin promotes the proliferation of primordial germ cell-like cells derived from porcine skin-derived stem cells: A mechanistic analysis

In vitro differentiation of stem cells into functional gametes remains of great interest in the biomedical field. Skin-derived stem cells (SDSCs) are an adult stem cells that provides a wide range of clinical applications without inherent ethical restrictions. In this paper, porcine SDSCs were successfully differentiated into primordial germ cell-like cells (PGCLCs) in conditioned media. The PGCLCs were characterized in terms of cell morphology, marker gene expression, and epigenetic properties. Furthermore, we also found that 25 μM melatonin (MLT) significantly increased the proliferation of the SDSC-derived PGCLCs while acting through the MLT receptor type 1 (MT1). RNA-seq results found the mitogen-activated protein kinase (MAPK) signaling pathway was more active when PGCLCs were cultured with MLT. Moreover, the effect of MLT was attenuated by the use of S26131 (MT1 antagonist), crenolanib (platelet-derived growth factor receptor inhibitor), U0126 (mitogen-activated protein kinase kinase inhibitor), or CCG-1423 (serum response factor transcription inhibitor), suggesting that MLT promotes the proliferation processes through the MAPK pathway. Taken together, this study highlights the role of MLT in promoting PGCLCs proliferation. Importantly, this study provides a suitable in vitro model for use in translational studies and could help to answer numerous remaining questions related to germ cell physiology.

Exogenous melatonin protects preimplantation embryo development from decabromodiphenyl ethane-induced circadian rhythm disorder and endogenous melatonin reduction

Decabromodiphenyl ethane (DBDPE) is a novel flame retardant that is widely used in plastics, electronic products, building materials and textiles. Our previous studies have revealed the oocyte toxicity of DBDPE, but the effect of DBDPE on preimplantation embryo development has not been reported. Here, we investigated whether and how DBDPE exposure affects preimplantation embryo development. Adult female mice were orally exposed to DBDPE (0, 5, 50, 500 μg/kg bw/day) for 14 days. First, we found that after DBDPE exposure, mice showed obvious circadian rhythm disorder. Moreover, the development of preimplantation embryos was inhibited in DBDPE-exposed mice after pregnancy. Then, we further explored and revealed that DBDPE exposure reduced the endogenous melatonin (MLT) level during pregnancy, thereby inhibiting the development of preimplantation embryos. Furthermore, we discovered that exogenous MLT supplementation (15 mg/kg bw/day) rescued the inhibition of preimplantation embryo development induced by DBDPE, and a mechanistic study demonstrated that exogenous MLT inhibited the overexpression of ROS and DNA methylation at the 5-position of cytosine (5-mC) in DBDPE-exposed preimplantation embryos. Simultaneously, MLT ameliorated the DBDPE-induced mitochondrial dysfunction by increasing the mitochondrial membrane potential (MMP), ATP, and Trp1 expression. Additionally, MLT restored DBDPE-induced changes in zona pellucida (ZP) hardness and trophectoderm (TE) cortical tension. Finally, the protective effect of MLT on embryos ameliorated the adverse reproductive outcomes (dead fetus, fetus with abnormal liver, fetal weight loss) induced by DBDPE. Collectively, DBDPE induced preimplantation embryo damage leading to adverse reproductive outcomes, and MLT has emerged as a potential tool to rescue adverse reproductive outcomes induced by DBDPE.

Protective Mechanism of Luteinizing Hormone and Follicle-Stimulating Hormone Against Nicotine-Induced Damage of Mouse Early Folliculogenesis

Previous studies have shown that nicotine could impair the germ cell cyst breakdown and the primordial follicle assembly by autophagy. In this paper, we discovered that luteinizing hormone (LH) and follicle-stimulating hormone (FSH) could counteract the damage caused by nicotine of mouse germ cell cyst breakdown. The neonatal mice were separately intraperitoneally injected with nicotine, nicotine plus LH, nicotine plus FSH, and saline (control) for 4 days. Compared with the nicotine group, the quality of oocytes and the number of follicles were remarkably increased in the nicotine plus LH group or nicotine plus FSH group. LH and FSH could alleviate nicotine-induced oocyte autophagy by different pathways. LH reduced the nicotine-induced autophagy by restoring the phosphorylation level of adenosine 5′-monophosphate-activated protein kinase α-1, while FSH by downregulating the phosphorylation level of Forkhead box class O 1. In addition, in a subsequent study of 6-week mice in different treated groups, we found that LH and FSH supplementation significantly improved normal maturation rates, fertilization rates, and embryo’s developmental potential of oocytes in oocytes exposed to nicotine. Taken together, these results suggested that LH and FSH could counteract the damage caused by nicotine and finally ensure normal germ cell cyst breakdown and early embryo development.

Third-hand smoke exposure is associated with abnormal serum melatonin level via hypomethylation of CYP1A2 promoter: Evidence from human and animal studies

This study aimed to examine whether and how third-hand smoke (THS) exposure would influence serum melatonin level. 1083 participants with or without exposure to THS were enrolled. Serum ROS, SOD, GSH-Px, and melatonin were measured by ELISA. Methylation microarrays detection and WGCNA were performed to identify hub methylated-sites. The methylation levels of hub-sites were validated in addtional samples. Moreover, mice were exposed to THS for 6 months mimicking exposure of human and the serum, liver, and pineal were collected. Oxidative stress-related indicators in serum, pineal, and liver were measured by ELISA. The expressions of mRNA and protein and methylation levels of hub-gene discovered in human data were further explored by RT-PCR, western-blot, and TBS. The results showed the participants exposed to THS had lower melatonin-level. 820 differentially methylated sites associated with THS were identified. And the hub-site located on the CYP1A2 promoter was identified, which mediated the association between THS and decreased melatonin-level. Decreased peak of serum melatonin, increased ROS and reduced SOD and GSH-Px in pineal and liver, and elevated CYP1A2 expression in liver was also found in the THS-exposed mice. Hypo-methylation of 7 CPG sites on the CYP1A2 promoter was identified, which accelerated the catabolism of melatonin. Overall, THS exposure is associated with abnormal melatonin catabolism through hypo-methylation of CYP1A2-promoter.