Improvement of bovine in vitro embryo production by vitamin K₂ supplementation.

Mitochondria play an important role during early development in mammalian embryos. It has been shown that properly controlled follicular preparation increases the likelihood of in-vitro-produced bovine embryos reaching the blastocyst stage and that competent embryos exhibit heightened expression of genes associated with mitochondrial function. We hypothesized that apparently incompetent embryos could be rescued by restoring mitochondrial function. It has been shown that vitamin K2 (a membrane-bound electron carrier similar to ubiquinone) can restore mitochondrial dysfunction in eukaryotic cells. The aim of this study was therefore to investigate the effects of vitamin K2 on bovine embryonic development in vitro. The vitamin was found most effective when added 72 h after fertilization. It produced a significant (P<0.05) increase in the percentage of blastocysts (+8.6%), more expanded blastocysts (+7.8%), and embryos of better morphological quality. It improved the mitochondrial activity significantly and had a measurable impact on gene expression. This is the first demonstration that current standard conditions of in vitro production of bovine embryos may be inadequate due to the lack of support for mitochondrial function and may be improved significantly by supplementing the culture medium with vitamin K2.