Retrospective study of single vitrified-warmed blastocyst transfer cycles according to the presence of morphokinetic variables

Enhancement of preimplantation mouse embryo development with optimized in vitro culture dish via stabilization of medium osmolarity

OBJECTIVE

We evaluated the efficacy of the newly developed optimized in vitro culture (OIVC) dish for cultivating preimplantation mouse embryos. This dish minimizes the need for mineral oil and incorporates microwells, providing a stable culture environment and enabling independent monitoring of individual embryos.

METHODS

Mouse pronuclear (PN) zygotes and two-cell-stage embryos were collected at 18 and 46 hours after human chorionic gonadotropin injection, respectively. These were cultured for 120 hours using potassium simplex optimized medium (KSOM) to reach the blastocyst stage. The embryos were randomly allocated into three groups, each cultured in one of three dishes: a 60-mm culture dish, a microdrop dish, and an OIVC dish that we developed.

RESULTS

The OIVC dish effectively maintained the osmolarity of the KSOM culture medium over a 5-day period using only 2 mL of mineral oil. This contrasts with the significant osmolarity increase observed in the 60-mm culture dish. Additionally, the OIVC dish exhibited higher blastulation rates from two-cell embryos (100%) relative to the other dish types. Moreover, blastocysts derived from both PN zygotes and two-cell embryos in the OIVC dish group demonstrated significantly elevated mean cell numbers.

CONCLUSION

Use of the OIVC dish markedly increased the number of cells in blastocysts derived from the in vitro culture of preimplantation mouse embryos. The capacity of this dish to maintain medium osmolarity with minimal mineral oil usage represents a breakthrough that may advance embryo culture techniques for various mammals, including human in vitro fertilization and embryo transfer programs.

Non-invasive evaluation of embryo quality for the selection of transferable embryos in human in vitro fertilization-embryo transfer

The ultimate goal of human assisted reproductive technology is to achieve a healthy pregnancy and birth, ideally from the selection and transfer of a single competent embryo. Recently, techniques for efficiently evaluating the state and quality of preimplantation embryos using time-lapse imaging systems have been applied. Artificial intelligence programs based on deep learning technology and big data analysis of time-lapse monitoring system during in vitro culture of preimplantation embryos have also been rapidly developed. In addition, several molecular markers of the secretome have been successfully analyzed in spent embryo culture media, which could easily be obtained during in vitro embryo culture. It is also possible to analyze small amounts of cell-free nucleic acids, mitochondrial nucleic acids, miRNA, and long non-coding RNA derived from embryos using real-time polymerase chain reaction (PCR) or digital PCR, as well as next-generation sequencing. Various efforts are being made to use non-invasive evaluation of embryo quality (NiEEQ) to select the embryo with the best developmental competence. However, each NiEEQ method has some limitations that should be evaluated case by case. Therefore, an integrated analysis strategy fusing several NiEEQ methods should be urgently developed and confirmed by proper clinical trials.

Between-laboratory reproducibility of time-lapse embryo selection using qualitative and quantitative parameters: a systematic review and meta-analysis

PURPOSE

To investigate the between-laboratory reproducibility of embryo selection/deselection effectiveness using qualitative and quantitative time-lapse parameters.

METHODS

A systematic search was performed on MEDLINE, EMBASE, and the Cochrane Library (up to February 2020) without restriction on date, language, document type, and publication status. Measuring outcomes included implantation, blastulation, good-quality blastocyst formation, and euploid blastocyst.

RESULTS

We detected 6 retrospective cohort studies externally validating the first clinical time-lapse model (Meseguer) emphasizing quantitative parameters, of which 3 (including one involving 2 independent centers) were included for the pooled analysis. Receiver operating characteristics analysis showed reduced predictive power of the model when either including or not including sister clinic validation. Fifteen cohort studies evaluating qualitative parameters were included for meta-analysis, and the mean Newcastle-Ottawa Scale was 5.3. Overall, meta-analysis showed significantly adverse association between the presence of ≥ 1 cleavage abnormalities and embryo implantation rates (11 studies, n = 7266; RR = 0.39[0.28, 0.55]_{95% CI}; I² = 57%). Further analysis showed adverse impacts of direct cleavage (7 studies, n = 7065; RR = 0.28 [0.15, 0.54] _{95% CI}; I² = 46%), reverse cleavage (2 studies, n = 3622; RR = 0.16 [0.03, 0.75] _{95% CI}; I² = 0%), chaotic cleavage (2 studies, n = 3643; RR = 0.11 [0.02, 0.69] _{95% CI}; I² = 24%), and multinucleation (5 studies, n = 2576; RR = 0.59 [0.50, 0.69] _{95% CI}; I² = 0%), but not the < 6 intercellular contact points at the 4-cell stage (1 study, n = 185; RR = 0.17 [0.02, 1.15] _{95% CI}).

CONCLUSIONS

Qualitative time-lapse parameters are reliably associated with embryo developmental potential among laboratories, whereas the reproducibility of time-lapse embryo selection model that emphasizes quantitative parameters may be compromised when externally applied.

Multinucleation in Day Two Embryos Is Not Associated with Multinucleation in Sibling Embryos After Freezing and Thawing

BACKGROUND

Multinucleated embryos exhibit impaired implantation potential, but whether the presence of multinucleated embryos in an embryo cohort reflects the quality of the entire cohort is controversial. No data exists on multinucleation rate among frozen-thawed embryos.

METHODS

De novo multinucleation and the number of multinucleated embryos on day two of embryo culture before freezing (D2) (n=415), at thawing (D2t) (n=320) and after an overnight culture after thawing (D3t) (n=265) was recorded. Associations between multinucleation before and after cryopreservation, female age and ovarian sensitivity to hormonal stimulation were assessed.

RESULTS

The occurrence of at least one multinucleated embryo per embryo cohort was 62.4% on D2, 16.3% on D2t and 31.7% on D3t. The presence of multinucleated embryos prior to freezing was not associated with de novo multinucleation during post-thaw culture (p=0.845). On D2, multinucleation was high in young women, irrespective of the number of collected oocytes (p=0.702). In older age groups, multinucleation was highest if >17 oocytes were obtained (p<0.001) and the odds for multinucleation was the lowest if the consumption of recombinant follicle-stimulating hormone was >238 IU/oocyte (In the age group of 30-35 years OR 0.25 [0.13-0.47], and the age group of 36-40 years OR 0.35 [0.20-0.63].

CONCLUSION

Multinucleation is commonly seen in embryos and good-quality day two embryo cohorts before freezing. The presence of multinucleated embryos prior to freezing does not illustrate multinucleation in sibling embryos after thawing. Embryo multinucleation is associated with factors related to good prognosis in assisted reproduction treatments.