Human reproduction open最新文献

Study question: How different is the global proteomic and metabolic profile of mouse blastocysts generated by IVF, cultured in optimal (5% O₂) or stressful (20% O₂) conditions, compared to in vivo generated blastocysts?

Summary answer: We found that in IVF-generated embryos: (i) the proteome was more sensitive to high oxygen levels than the global metabolomic profile; (ii) enzymes involved in splicing and the spliceosome are altered; (iii) numerous metabolic pathways, particularly amino acids metabolism, are altered (iv) there is activation of the integrated stress response (ISR) and downregulation of mTOR pathways.

What is known already: IVF culture conditions are known to affect the gene expression of embryos. However, comprehensive data on the global metabolic and proteomic changes that occur in IVF-generated embryos are unknown.

Study design size duration: Mouse embryos were generated by natural mating (in vivo control or flushed blastocyst-FB-group) or by IVF using KSOM medium and two distinct oxygen concentrations: 5% O₂ (optimal) and 20% O₂ (stressful). Proteomic and metabolomic analyses were performed using state-of-the-art mass spectrometry techniques in triplicate (n = 100 blastocysts per replicate), allowing for detailed profiling of protein and metabolite alterations in each group.

Participants/materials setting methods: Mouse blastocysts were collected from CD-1 and B6D2F1 strains as specified above. High-resolution liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for proteomics, while high-performance liquid chromatography coupled with mass spectrometry (HILIC-MS) was used for metabolomics. In addition, Immunofluorescence was used to assess the activation of stress response pathways, including the ISR.

Main results and the role of chance: Proteomic analysis revealed significant changes in protein expression in embryos cultured under 20% O₂ compared to 5% O₂ and in vivo embryos. Compared to in vivo embryos, IVF embryos cultured under 20% O₂ exhibited 599 differentially expressed proteins, with an increase in proteins involved in oxidative stress responses, aminoacyl-tRNA synthesis, and spliceosome pathways. In contrast, IVF embryos cultured under 5% O₂ showed fewer changes, with 426 differentially expressed proteins, though still reflecting significant alterations compared to in vivo embryos. These results indicate that embryos in stressful conditions (20% O₂) exhibit a stronger stress response and alterations in critical pathways for protein synthesis and DNA repair. Metabolomic analysis revealed that embryos cultured under 20% O₂ showed changes in branch-chained amino acid levels, and decreased levels of key metabolites of the TCA cycle an

Embryo selection (ES) during IVF is expected to select the 'best' embryo(s) from among a cycle's embryo cohort and has been a core concept of IVF for over 40 years. However, among 36 492 articles on ES in a recent PubMed search, we were unable to locate even a single one questioning the concept that, beyond standard oocyte and embryo morphology, ES has remained an unproven hypothesis. In unselected patient populations, attempts at ES have universally, indeed, failed to improve cumulative pregnancy and live birth rates. The only benefit ES appears to offer is a marginal shortening in time to pregnancy, and even this benefit manifests only in best-prognosis patients with large oocyte and embryo numbers. Excluding in vitro maturation efforts, oocytes, once retrieved, and their resulting embryos have predetermined finite cumulative pregnancy and live birth chances that cannot be further improved. The hypothesis of ES has, however, remained a driving force for research and the introduction of a multitude of 'add-ons' to IVF. Enormous investments over decades in ES, therefore, should be better redirected from post- to pre-retrieval efforts.

Study question: Compared with embryonic cytogenetic constitution of biopsied samples in human pre-implantation embryos, are there any differences in whole embryos?

Summary answer: Whole embryos exhibit a significantly higher euploidy rate and reduction in mosaic aneuploidy rate compared to biopsied samples.

What is known already: Much of the existing evidence of cytogenetic constitution of human pre-implantation embryos is based on biopsied cells obtained from blastomeres or trophectoderm biopsies. The mosaic rate of biopsies taken from blastocyst trophectoderm ranges widely, from 2% to 25%.

Study design size duration: We investigated the embryonic cytogenetic constitution of 221 whole human embryos/blastocysts from 2019 to 2022, including 41 high-quality blastocysts, 57 low-quality blastocysts, and 123 arrested embryos/blastocysts.

Participants/materials setting methods: The cytogenetic constitution of whole embryos/blastocysts was assessed using next-generation sequencing. Mosaicism was diagnosed using a cut-off threshold of 30-70%, with embryos displaying 30-70% aneuploid cells classified as mosaic.

Main results and the role of chance: Among high-quality blastocysts, the euploidy rate was 82.9%, with a remarkably low mosaic aneuploidy of only 2.5%. The euploidy rates of viable low-quality blastocysts and arrested embryos/blastocysts were 38.6% and 13.0%, respectively. The mosaic aneuploidy rate decreased progressively with embryonic development, from 93.2% at the cleavage stage to 40% at the blastocyst stage. Chaotic aneuploidy was the primary factor (66.1%, 39/59) contributing to embryonic arrest at the cleavage stage. Additionally, 26.1% of embryos/blastocysts exhibited segmental aneuploidy, with segmental duplications (30.6%, 22/72) and deletions (54.2%, 39/72) being the most common types of segmental aneuploidy.

Limitations reasons for caution: The sample size in this study is relatively small, especially in the subgroup analysis. Furthermore, whole-embryo analysis is not a foolproof diagnostic method, since it may underestimate the presence of mosaicism.

Wider implications of the findings: The cytogenetic constitution of whole embryos provides a more accurate reflection of their physiological state compared to biopsied samples. The low mosaic aneuploidy rate in high-quality blastocysts supports the practice of transferring mosaic embryos in patients without euploid embryos. If blastocysts reach stage III by Day 6 post-fertilization, nearly half are euploid, suggesting that extending embryo culture to Day 7 may be beneficial in cases where high-quality embryos are lacking.

Study funding/competing interests: This study was supported by the Natural Science Foundation of Guangdong Province (No. 2023A1515010250) and Pilot Program-China Reprodu