Background: Cadmium (Cd) is toxic heavy metal that accumulates in organisms after passing through their respiratory and digestive tracts. Although several studies have reported the toxic effects of Cd exposure on human health, its role in embryonic development during preimplantation stage remains unclear. We investigated the effects of Cd on porcine embryonic development and elucidated the mechanism. Methods: We cultured parthenogenetic embryos in media treated with 0, 20, 40, or 60 μM Cd for 6 days and evaluated the rates of cleavage and blastocyst formation. To investigate the mechanism of Cd toxicity, we examined intracellular reactive oxygen species (ROS) and glutathione (GSH) levels. Moreover, we examined mitochondrial content, membrane potential, and ROS. Results: Cleavage and blastocyst formation rates began to decrease significantly in the 40 μM Cd group compared with the control. During post-blastulation, development was significantly delayed in the Cd group. Cd exposure significantly decreased cell number and increased apoptosis rate compared with the control. Embryos exposed to Cd had significantly higher ROS and lower GSH levels, as well as lower expression of antioxidant enzymes, compared with the control. Moreover, embryos exposed to Cd exhibited a significant decrease in mitochondrial content, mitochondrial membrane potential, and expression of mitochondrial genes and an increase in mitochondrial ROS compared to the control. Conclusions: We demonstrated that Cd exposure impairs porcine embryonic development by inducing oxidative stress and mitochondrial dysfunction. Our findings provide insights into the toxicity of Cd exposure on mammalian embryonic development and highlight the importance of preventing Cd pollution.

INTRODUCTION
MATERIALS AND METHODS
    Chemicals
    Oocyte preparation and in vitro maturation (IVM)
    Parthenogenetic activation (PA) and in vitro culture(IVC)
    Chemical treatment
    CDX2 staining
    TdT-mediated dUTP nick-end labelling (TUNEL)assays
    Measurement of ROS and GSH levels
    Analysis of mitochondrial contents, ROS, andmembrane potential
    Real-time polymerase chain reaction (qRT-PCR)
    Statistical analyses
RESULTS
    Cd exposure impairs porcine embryonic development
    Cd exposure reduces blastocyst quality in porcineembryos
    Exposure to Cd induces oxidative stress in porcineembryos
    Cd exposure negatively affects mitochondrial contentand function in porcine embryos
DISCUSSION
CONCLUSION
REFERENCES

• Min Ju Kim(Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju 28116, Korea, Department of Animal Science, College of Natural Resources & Life Science, Pusan National University, Miryang 50463, Korea)
• Se‑Been Jeon(Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju 28116, Korea, Department of Animal Science, College of Natural Resources & Life Science, Pusan National University, Miryang 50463, Korea)
• Hyo‑Gu Kang(Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju 28116, Korea, Department of Animal Science and Biotechnology, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea)
• Bong‑Seok Song(Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju 28116, Korea)
• Bo‑Woong Sim(Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju 28116, Korea, Department of Functional Genomics, University of Science and Technology, Daejeon 34113, Korea)
• Sun‑Uk Kim(Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju 28116, Korea, Department of Functional Genomics, University of Science and Technology, Daejeon 34113, Korea)
• Pil‑Soo Jeong(Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju 28116, Korea) Corresponding author
• Seong‑Keun Cho(Department of Animal Science, College of Natural Resources and Life Science, Life and Industry Convergence Research Institute, Pusan National University, Miryang 50463, Korea) Corresponding author