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Polyethylene microplastics as emerging reproductive toxicants: Evidence from an oocyte-based mammalian model
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Scientists exposed cow egg cells to tiny plastic particles (polyethylene microplastics) at levels similar to what's already found in human blood and ovarian fluid, and found the plastics disrupted key steps in egg cell maturation, including energy production and antioxidant defenses. The good news: eggs still went on to fertilize and develop into embryos normally in this study, but the fact that eggs showed stress signals at all suggests they could be an early warning sign of how microplastics might affect fertility over time. More research is needed to know if this holds true in humans, but it's a reason to take everyday plastic exposure seriously.
Microplastics (MPs) are emerging environmental contaminants detected in biological fluids, including blood and follicular fluid, raising concern about their potential effects on mammalian reproduction. The present study investigated whether polyethylene microplastics (PE-MPs; 10-30 μm), at concentrations reported in vivo, affect bovine oocyte maturation and subsequent embryonic development. Bovine cumulus-oocyte complexes were matured in vitro for 24 h in the presence of 0, 0.025, 0.5, or 1.5 μg/mL PE-MPs. Nuclear maturation, mitochondrial distribution, mitochondrial content, mitochondrial membrane potential (ΔΨm), intracellular glutathione (GSH) in oocytes, progesterone secretion by cumulus cells, and embryo development after in vitro fertilization were evaluated. PE-MPs exposure significantly impaired meiotic progression. Mitochondrial content decreased at all concentrations, accompanied by abnormal mitochondrial aggregation and altered distribution, particularly at intermediate concentration, whereas ΔΨm remained unchanged. Intracellular GSH levels were reduced at 0.5 and 1.5 μg/mL. In contrast, progesterone secretion and early embryo development were not affected. Nuclear maturation, mitochondrial aggregation and migration and GSH levels exhibited quadratic dose-response patterns, suggesting a non-monotonic response consistent with adaptive cellular stress rather than overt cytotoxicity. The combination of preserved bioenergetic activity with mitochondrial redistribution and oxidative imbalance indicates activation of mitochondrial quality-control mechanisms. These findings support an endocrine-disruptor-like mode of action affecting regulatory pathways controlling meiotic maturation rather than steroidogenic capacity. In conclusion, PE-MPs disrupt bovine oocyte maturation by targeting mitochondrial organization and redox homeostasis without compromising overall cellular viability or embryonic competence. The oocyte therefore represents a highly sensitive early indicator of reproductive toxicity.
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Oxidative-stress-mediated apoptosis triggered by microplastics disrupts bovine oocyte maturation
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Scientists found that microplastics can damage cow egg cells by causing internal stress that harms their energy-producing structures (mitochondria), which reduced the eggs' ability to mature and develop into embryos. While this study was done in cattle, not humans, it adds to growing evidence that microplastics may affect reproductive health in animals — and the good news is that melatonin, a natural antioxidant your body already makes, helped protect the eggs from this damage. More research is needed to know if this applies to human fertility, but it's a promising clue for future protective strategies.
In vitro exposure to polystyrene microplastics exerts oocyte toxicity through cumulus cells damage in the sheep model
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Scientists exposed sheep egg cells to tiny plastic particles called microplastics and found that higher amounts damaged the cells that support egg development, leading to lower-quality eggs. The plastic particles caused harmful stress and cell death in these support cells, which then prevented the eggs from developing properly. This research suggests that microplastics in our environment could potentially harm fertility by interfering with how eggs mature, though more studies are needed to confirm effects in humans.
Microplastics are present in women’s and cows’ follicular fluid and polystyrene microplastics compromise bovine oocyte function in vitro
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Researchers detected microplastics in the follicular fluid of both women and cows, marking one of the first studies to find these particles in reproductive tissues. In laboratory tests, polystyrene microplastics impaired bovine egg cell function at concentrations comparable to what was found in the follicular fluid. The findings raise questions about whether microplastic exposure could be a contributing factor in the widespread declines in reproductive health observed in recent decades.
Micro- and nanoplastics-induced oocyte toxicity: molecular mechanisms and potential intergenerational and transgenerational risks
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This review summarizes existing animal and human research on how tiny plastic particles may affect egg cells, finding links to cell stress, inflammation, and disrupted egg development. Studies in animals suggest effects may pass to offspring, but evidence for effects across multiple generations, and for human reproductive health, remains limited.
Author Response: Microplastics are present in women’s and cows’ follicular fluid and polystyrene microplastics compromise bovine oocyte function in vitro
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Researchers found microplastics — predominantly polystyrene — in the follicular fluid surrounding eggs in both women and cows undergoing fertility treatment, and showed in laboratory tests that these concentrations were enough to impair the development of bovine egg cells. This is one of the first studies to directly link real-world microplastic exposures in reproductive tissue to measurable harm, raising the possibility that the global rise in plastic pollution may be contributing to declining fertility rates in humans and animals.
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