Embryo cryopreservation
Cryopreservation of human embryos is routinely practiced in IVF settings as described in the article above. The subtleties of cryopreservation techniques are under constant scrutiny in order to encourage ever better outcomes for patients undergoing the stressful and difficult process of IVF.
For example, in a recent study from Sun Yat-sen University, Guangzhou in China, amino acid metabolism as an indicator of metabolic stagnation during cryopreservation was compared between frozen-thawed and fresh early-stage human embryos over time after thawing. Significant differences in amino acid metabolism were observed between culture medium of fresh embryos versus medium of post-thawed embryos at 0.5 h. These differences were gone by 1 h after thawing, suggesting that this may be the optimal time for embryo transfer in IVF.
The original article in this thread mentions that vitrification is now the most common freezing technique used. This process is also under constant review. For example, the FDA has recently approved a closed carrier for embryo vitrification called the Rapid-I which cools at a much lower rate of - 1220°C/min compared to open vitrification systems such as the cryoloop (-15,000°C/min). A study on this device from Cleveland Clinic Fertility Center in the USA found that clinical pregnancy rate (CPR) and implantation rate (IR) with Rapid-i for both vitrified blastocysts and cleavage stage embryos was comparable to that achieved with cryoloop. However, the Rapid-I has advantages in that it prevents direct contact between the embryos and liquid nitrogen and reduces the potential risk of sample cross-contamination or infection. Another study on vitrification, from Tongji University School of Medicine in Shanghai found that in vitrified-warmed embryo transfer, cryopreservation of the entire cohort of embryos on day 3 resulted in better clinical outcomes compared with day 2, particularly for poor ovarian responder patients.
One issue which sometimes arises in IVF is risk of mismatching errors or mix-ups. A study on mouse embryos in which embryos were tagged with biofunctionalized polysilicon barcodes to the outer surface of the zona pellucida provides a potentially novel solution to this problem. No adverse effects were observed in terms of tagged embryo development and the tagging process survived embryo cryopreservation.
Sources
CHI, F. et al., 2013. Vitrification of day 3 cleavage-stage embryos yields better clinical outcome in comparison with vitrification of day 2 cleavage-stage embryos. Zygote (Cambridge, England), , pp. 1-8
DESAI, N.N. et al., 2013. The new Rapid-i carrier is an effective system for human embryo vitrification at both the blastocyst and cleavage stage. Reproductive Biology And Endocrinology: RB&E, 11, pp. 41-41
FANG, C. et al., 2013. Comparison of amino acid metabolism in frozen-thawed and fresh early-stage human embryos. Australia: Wiley-Blackwell Pub. Asia].
NOVO, S. et al., 2013. Direct embryo tagging and identification system by attachment of biofunctionalized polysilicon barcodes to the zona pellucida of mouse embryos. Human reproduction (Oxford, England), 28(6), pp. 1519-1527
Cryopreservation of human embryos is routinely practiced in IVF settings as described in the article above. The subtleties of cryopreservation techniques are under constant scrutiny in order to encourage ever better outcomes for patients undergoing the stressful and difficult process of IVF.
For example, in a recent study from Sun Yat-sen University, Guangzhou in China, amino acid metabolism as an indicator of metabolic stagnation during cryopreservation was compared between frozen-thawed and fresh early-stage human embryos over time after thawing. Significant differences in amino acid metabolism were observed between culture medium of fresh embryos versus medium of post-thawed embryos at 0.5 h. These differences were gone by 1 h after thawing, suggesting that this may be the optimal time for embryo transfer in IVF.
The original article in this thread mentions that vitrification is now the most common freezing technique used. This process is also under constant review. For example, the FDA has recently approved a closed carrier for embryo vitrification called the Rapid-I which cools at a much lower rate of - 1220°C/min compared to open vitrification systems such as the cryoloop (-15,000°C/min). A study on this device from Cleveland Clinic Fertility Center in the USA found that clinical pregnancy rate (CPR) and implantation rate (IR) with Rapid-i for both vitrified blastocysts and cleavage stage embryos was comparable to that achieved with cryoloop. However, the Rapid-I has advantages in that it prevents direct contact between the embryos and liquid nitrogen and reduces the potential risk of sample cross-contamination or infection. Another study on vitrification, from Tongji University School of Medicine in Shanghai found that in vitrified-warmed embryo transfer, cryopreservation of the entire cohort of embryos on day 3 resulted in better clinical outcomes compared with day 2, particularly for poor ovarian responder patients.
One issue which sometimes arises in IVF is risk of mismatching errors or mix-ups. A study on mouse embryos in which embryos were tagged with biofunctionalized polysilicon barcodes to the outer surface of the zona pellucida provides a potentially novel solution to this problem. No adverse effects were observed in terms of tagged embryo development and the tagging process survived embryo cryopreservation.
Sources
CHI, F. et al., 2013. Vitrification of day 3 cleavage-stage embryos yields better clinical outcome in comparison with vitrification of day 2 cleavage-stage embryos. Zygote (Cambridge, England), , pp. 1-8
DESAI, N.N. et al., 2013. The new Rapid-i carrier is an effective system for human embryo vitrification at both the blastocyst and cleavage stage. Reproductive Biology And Endocrinology: RB&E, 11, pp. 41-41
FANG, C. et al., 2013. Comparison of amino acid metabolism in frozen-thawed and fresh early-stage human embryos. Australia: Wiley-Blackwell Pub. Asia].
NOVO, S. et al., 2013. Direct embryo tagging and identification system by attachment of biofunctionalized polysilicon barcodes to the zona pellucida of mouse embryos. Human reproduction (Oxford, England), 28(6), pp. 1519-1527
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