Effect of varying equilibration time in a two-step vitrification method on the post-warming DNA integrity of mouse blastocysts

Shortened equilibration time can compromise clinical outcomes in human embryo vitrification

“…The potential mechanism by which differences in equilibration times may affect outcome could include: (i) induction of DNA damage since animal studies (Kader et al, 2010) have shown that different equilibration times influenced DNA integrity index of mouse blastocysts; (ii) spindle damage, since a significantly higher incidence of spindle abnormalities was reported in vitrified blastocyst compared with fresh blastocyst (Chatzimeletiou et al, 2012) and (iii) osmotic stress, because it is important to keep embryo volume variation within limits ( 30% of the original volume) (Vanderzwalmen et al, 2009) and shortened equilibration time may result in insufficient recovery of embryo volume and aggravate damage to embryos.…”

“…For example, Bagis et al (2005) investigated the optimal equilibration time when mouse embryos were vitrified at 37 C. They found that vitrification with a 15-min equilibration produced higher hatched blastocyst rate compared to that seen following 5, 10 or 20 min of equilibration. Conversely, Kader et al (2010) showed that an equilibration time of 8 min at room temperature improved mouse blastocyst DNA integrity index compared to 4 min and 15 min equilibration. These animal studies have suggested that equilibration time is an important parameter in embryo cryopreservation, but to our knowledge, there have been limited studies on human embryos.…”

“…Some animal studies had shown the effects of different equilibration times (Bagis, Mercan, Cetin, & Sekmen, 2005;Kader, Choi, Sharma, Falcone, & Agarwal, 2010). For example, Bagis et al (2005) investigated the optimal equilibration time when mouse embryos were vitrified at 37 C. They found that vitrification with a 15-min equilibration produced higher hatched blastocyst rate compared to that seen following 5, 10 or 20 min of equilibration.…”

The optimal timing of blastocyst vitrification after trophectoderm biopsy of preimplantation genetic screening

“…A major difficulty with this approach is that the high cryoprotectant concentrations required for avoiding crystal formation increase the risk of osmotic and toxic damage [33]. Although vitrification shows a high survival rate, the reduction of osmotic shock and toxicity by employing an appropriate equilibration step or cryoprotectant exposure time is critical to improving survival rates and embryo development [34][35][36][37]. Moreover, Gajda and Smorag (2002) [38] reported that the vitrification solution was more toxic to hatched porcine blastocysts (a broken zona) than to expanded blastocysts.…”

Efficiency and Safety of Human Reproductive Cell/Tissue Vitrification

“…However, pretreatment with cytoskeletal stabilizers in order to improve blastocyst survival after warming obviously does not work (Chen et al, 2005). Changes in equilibration time might have a negative impact on DNA integrity as could be shown in a mouse model (Kader et al, 2010b). However, gene expression was found not to be statistically altered in warmed blastocysts treated with different vitrification protocols (but in slow freezing some 100 genes were up-or downregulated) (Larman et al, 2011).…”