Effects of Phthalate Metabolite Mixture Exposure on Mouse Oocyte Development

Area of Science:

• Reproductive Toxicology
• Environmental Health
• Molecular Biology

Background:

• Phthalates are widespread endocrine-disrupting chemicals (EDCs) found in numerous consumer products.
• Chronic human exposure often involves complex mixtures of phthalate metabolites, not single compounds.
• The impact of combined phthalate metabolite exposure on oogenesis is not well understood.

Purpose of the Study:

• To investigate the effects of a defined phthalate metabolite mixture on meiotic progression in oocytes.
• To elucidate the molecular mechanisms underlying phthalate-induced oocyte developmental defects.

Main Methods:

• Development of a microinjection-based single-oocyte toxicological assay.
• Assessment of meiotic maturation, spindle and chromosome alignment, cytoskeletal organization, mitochondrial function, reactive oxygen species (ROS) levels, and DNA damage.
• Single-cell transcriptomic profiling to identify affected biological pathways and signaling cascades.

Main Results:

• Phthalate mixture exposure significantly inhibited oocyte maturation, with most oocytes failing to extrude the first polar body.
• Observed defects included disrupted spindle morphology, chromosome misalignment, disorganized actin cytoskeleton, and impaired mitochondrial function.
• Elevated ROS accumulation and DNA damage were detected, alongside significant alterations in gene expression related to exocytosis, cytoskeletal organization, and key signaling pathways (MAPK, JAK-STAT, GnRH).

Conclusions:

• Combined phthalate exposure directly compromises female gamete quality by inducing severe meiotic and molecular defects.
• These findings highlight the critical need to assess the risks of chemical mixtures for women's reproductive health.
• The study emphasizes the direct impact of EDCs on oocyte maturation and potential fertility.