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.