Zinc eluted from glassware is a risk factor for embryo development in human and animal assisted reproduction†

In assisted reproduction, many factors in the culture environment, including light, temperature, pH, and culture media, can reduce preimplantation embryo viability. Laboratory glassware is also a known risk factor for in vitro embryos; however, the underlying mechanisms that disrupt embryonic development remain unclear. We identified Zn eluted from glassware as an embryotoxic substance. In mouse embryos, Zn induced delayed development, abnormalities in chromosome segregation, cytokinesis, zygotic gene activation (e.g. Zscan4a and murine endogenous retrovirus with leucine, also known as MERVL), and aberrantly upregulated developmental gene expression (e.g. Hoxa1, Hoxb9, T, and Fgf8) that could be mediated through metal regulatory transcription factors (e.g. Mtf1). Subsequently, Zn exposure led to significantly reduced blastocyst formation. Post-implantation, Zn-exposed embryos were associated with normal birth rates, however, the birth weight increased by an average of 18% compared with embryos cultured without Zn. Furthermore, Zn exposure affected the development of bovine and human embryos, with species-based variation in the strength and timing of these effects. To mitigate these embryotoxic effects, we identified a method to prevent glass toxicity using chelating agents. This research not only highlights the importance of risk control in embryo culture but also facilitates the development of safe and effective methods for assisted reproduction.