Trophectoderm biopsy and vitrification: survival, oxidative stress and cell count in bovine embryos.

CONTEXT: Trophectoderm (TE) biopsy combined with embryo vitrification is increasingly being used; however, concerns remain regarding its effects on embryo survival and physiological stability after warming. AIMS: We aimed to evaluate whether TE biopsy performed prior to vitrification compromises early post-warming recovery and physiological responses of bovine embryos. METHODS: Expanded blastocysts were allocated into two groups, namely, Control and Biopsy. After warming, embryos were evaluated at 0, 4, 24, and 48 h for re-expansion and hatching rates. Mitochondrial activity, oxidative stress, antioxidant activity estimated by intracellular thiol content, and total cell number were assessed after 48 h. KEY RESULTS: Re-expansion differed between groups at 0 h (Control 13.40% vs Biopsy 33.90%; P = 0.005) and 4 h (Control 93.81% vs Biopsy 84.75%; P = 0.038), with no differences at 24 or 48 h (P ≥ 0.346). Hatching rates were similar at 4 h (P = 0.447), but higher in the Biopsy group at 24 h (77.56% vs 53.35%; P = 0.005) and 48 h (90.79% vs 77.39%; P = 0.027). The Biopsy group showed higher mitochondrial activity (P < 0.001), reactive oxygen species (P = 0.009), intracellular thiol content (P < 0.001), and total cell number (216.68 ± 9.75 vs 186.82 ± 10.22; P = 0.038). CONCLUSIONS: TE biopsy prior to vitrification induced oxidative stress, increased mitochondrial activity and increased thiol content, but did not compromise early post-warming recovery of bovine embryos. IMPLICATIONS: TE biopsy before vitrification is safe under short-term in vitro conditions.