Chapter 20 Gavi-Automated Vitrification Instrument

Vitrification of human blastocysts for couples undergoing assisted reproduction: an updated review

Over the past 40 years there has been a worldwide critical change in the field of assisted reproduction technology (ART), leading to the increased application of single blastocyst transfer, which is extremely important to avoid the risks of multiple pregnancy and associated complications for both mother and babies. Indeed, advancements in ART over the last few decades have been obtained thanks to several improvements, including ovarian stimulation, embryo culture conditions and, of course, progress in cryopreservation methods, especially with the application of vitrification. The ability to cryopreserve human embryos has improved significantly with vitrification compared to the initially adopted slow-freezing procedures. Since the introduction of vitrification, it has become the gold standard method to effectively cryopreserve human blastocysts. However, some new protocols are now being explored, such as the short warming procedure and even shorter exposure to the equilibration solution before vitrification, which seem to provide optimal results. Therefore, the main aim of the current narrative review, will be to illustrate the benefit of vitrification as an effective method to cryopreserve the human blastocyst and to illustrate new protocols and variations which in future may increase the performance of vitrification protocols.

Automation in vitrification and thawing of mouse oocytes and embryos

Vitrification is a common technique for cryopreserving oocytes or embryos. However, manual vitrification is tedious and labor-intensive, and can be subject to variations caused by human factors. To address these challenges, we developed an automated vitrification-thawing system (AVTS) based on a cryo-handle. Our study firstly assessed the efficiency of cryoprotectant exchange through comparing the osmolalities of fresh and collected solutions during automated vitrification and thawing, and evaluated the cooling and warming rates of the cryo-handle. We also compared mouse oocyte survival, fertilization and embryo development after thawing and ICSI, and the development of re-frozen cleavage embryos between manual operation and automated system. The results showed that the osmolalities of collected samples were within normal range and comparable to fresh solutions. Furthermore, the automated system could obtain the reliable cooling and warming rates. Particularly, there were no significant differences in oocyte survival rates, fertilization rates, and subsequent embryo development and its quality between two procedures. Our findings suggest that AVTS has no impact on osmolalities of vitrification and thawing solutions, ensuring the proper exchange of cryoprotectants. The cryo-handle also shows the ability to achieve reliable cooling and warming rates, which benefits for the cryopreservation and thawing process. Moreover, the results from mouse oocytes and embryos indicate that automated system has effectively maintained the survival and fertilization of frozen oocytes and supported subsequent embryo development. Therefore, the automated vitrification and thawing system will inevitably represent a superior alternative to manual operation.

Comparison of oocyte vitrification using a semi-automated or a manual closed system in human siblings: survival and transcriptomic analyses

BACKGROUND

Indications of oocyte vitrification increased substantially over the last decades for clinical and ethical reasons. A semi-automated vitrification system was recently developed making each act of vitrification reproducible. In this study, we evaluated the efficiency of the semi-automated technique of oocyte vitrification by survival rate, morphometric assessment and resistance to empty micro-injection gesture as compared with a manual method. Additionally, we intended to evaluate transcriptomic consequences of both techniques using single-cell RNA-seq technology.

RESULTS

Post-warming survival rate, oocyte surfaces and resistance to empty micro-injection were comparable between semi-automated and manual vitrification groups. Both oocyte vitrification techniques showed limited differences in the resulting transcriptomic profile of sibling oocytes since only 5 differentially expressed genes were identified. Additionally, there was no difference in median transcript integrity number or percentage of mitochondrial DNA between the two groups. However, a total of 108 genes were differentially expressed between fresh and vitrified oocytes (FDR < 0.05) and showed over-represented of genes related to important cellular process.

CONCLUSIONS

Our results provide reassurance about the influence of semi-automation as compared with the manual vitrification method. Concerning oocyte vitrification itself, no tight common transcriptomic signature associated has been observed across studies.

TRIAL REGISTRATION

NCT03570073.

Clinical re-biopsy of segmental gains-the primary source of preimplantation genetic testing false positives

PURPOSE

Does re-biopsy of blastocysts classified as abnormal (ABN) due to segmental aneuploidy (SA) have clinical utility?

METHODS

The live birth (LB) outcomes of mosaic SAs, compared to other categories, were determined after transfer of 3084 PGT-A tested blastocysts. An initial 12-month trial thawed 111 blastocysts classified as ABN due to a SA for clinical re-biopsy, with an additional 58 from a subsequent 16-month revised protocol. Where re-biopsy failed to corroborate the original classification, blastocysts were reported as mosaic and suitable for clinical use.

RESULTS

Segmental mosaics had a LB rate (54.1%) which was indistinguishable from that of euploid (53.7%). Numeric mosaics had statistically significant (P < 0.05) reduced LB rates compared to euploid, with high-level numerics (19.2%) also exhibiting a significant reduction compared to low level (42.3%). Of the initial 111 blastocysts with SAs, 85 could be re-biopsied. Segmental gains became suitable for re-biopsy at a high rate (90.9%), with 84.2% (16/19) of these reclassified as mosaic. Only 73.0% of deletions and complex changes were suitable for re-biopsy, of which 73.0% (46/63) were confirmed ABN. The subsequent 16-month period primarily focused on gains, confirming the high rate at which they can be reclassified as clinically useable.

CONCLUSIONS

Blastocysts harboring mosaic segmental duplications, rather than SAs in general, are the primary source of false-positive PGT-A results and represent a category with a LB rate similar to that of euploid. A high degree of confidence in the reliability of PGT-A results can be maintained by performing confirmatory clinical TE biopsies.

Cryopreservation of Porcine Embryos: Recent Updates and Progress

Cryopreservation of embryos is important for long-distance embryo transfer and conservation of genetic resources. Porcine research is important for animal husbandry and biomedical research. However, porcine embryos are difficult to cryopreserve because of their high cytoplasmic lipid content and sensitivity to chilling stress. Vitrification is more efficient than slow freezing, and vitrification is mostly used in embryo cryopreservation. So far, the vitrification process of porcine embryos has been continuously improved, resulting in improved survival rates of warmed embryos and farrowing rates after the transplant procedure. It is worth noting that automatic vitrification has made great progress, which is expected to promote the standardization and application of vitrification. In this article, the vitrification process of porcine embryos at the blastula stage and early development stages is reviewed in detail. In addition, the efficiency of different vitrification systems was compared. In addition, we summarize technology that can improve the survival rate of cryopreserved porcine embryos, such as delipidation methods (including physical delipidation and chemical delipidation) and medium improvements (including chemically defined media and adding antioxidants). Meanwhile, gene expression changes during cryopreservation are also elaborated.

Vitrification of the human embryo: a more efficient and safer in vitro fertilization treatment

Cryopreservation has become a central pillar in assisted reproduction, reflected in the exponential increase of "freeze all" cycles in the past few years. Vitrification makes it possible to cool and warm human eggs and embryos with far less cryo-damage than 'slow-freeze' and allows nearly intact survival of embryos with very high survival rates for eggs as well. This has resulted in a complete transformation how we manage treatment for in vitro fertilization patients. Fresh transfers can be avoided without compromising outcomes, and in fact, cumulative pregnancy/delivery rates may be improved by performing sequential elective "frozen" single embryo transfers. Some recent evidence suggests that previously vitrified embryos give better perinatal outcomes than fresh embryo transfers. Frozen embryo transfer, especially when coupled with preimplantation genetic testing allows for highly efficient single embryo transfers that translate to more singleton and therefore safer pregnancies, as well as healthier babies. Additionally, vitrification has also opened new options for patients, most notably fertility preservation (through oocyte cryopreservation), and donor egg banking.

Decision points for individualized hormonal stimulation with recombinant gonadotropins for treatment of women with infertility

It is essential that fertility treatment is individualized based on a thorough diagnostic work-up, with treatment tailored to the patients' requirements. This individualization should be kept in mind during the main decision points that occur before and during treatment. Treatment customization must include consideration of both the woman and her partner involved in the process together, including their collective treatment goals. Once treatment goals have been agreed and diagnostic evaluations performed, personalization based on patient characteristics, together with an understanding of treatment goals and patient preferences, enables the selection of appropriate treatments, protocols, products and their dosing. Following treatment initiation, monitoring and adaptation of product and dose can then ensure optimal outcomes. Currently, it is not possible to base treatment decisions on every characteristic of the patient and personalization is based on biomarkers that have been identified as the most relevant. However, in the future, the use of artificial intelligence coupled with continuous monitoring should enable greater individualization and improve outcomes. This review considers the current state-of-the-art related to decision points during individualized treatment of female infertility, before looking at future developments that might further assist in making individualized treatment decisions, including the use of computer-assisted decision making.