Unraveling the Puzzle: Oocyte Maturation Abnormalities (OMAS)

Comparison of luteal phase and follicular phase in-vitro maturation in women with oocyte maturation abnormalities

RESEARCH QUESTION

Are there differences in immature oocyte retrieval following luteal phase in-vitro maturation (IVM) compared with follicular phase IVM in women with oocyte maturation abnormalities (OMAs).

DESIGN

From January 2019 to May 2023, a retrospective cohort study at a private IVF centre included 36 women with 53 IVM cycles in Group 1 (follicular phase) and 24 women with 32 IVM cycles in Group 2 (luteal phase). Additionally, nine women had both follicular and luteal phase IVM cycles for intracycle variability analysis.

RESULTS

There were no differences in oocyte maturation stages between the groups at collection. Group 1 and Group 2 exhibited comparable median metaphase II oocyte rates per patient at 48 h after collection [40.0%, interquartile range (IQR) 0.0-66.7% versus 22.5%, IQR 0.0-52.9%] (P = 0.53). The median fertilization rate in Group 1 (66.7%, IQR 50.0-66.7%) was found to be comparable with that in Group 2 (66.7%, IQR 50.0-66.7%). There were no significant differences in the yielded embryo grades and pregnancy rates between the groups. Comparing follicular and luteal phase IVM within the same menstrual cycle in nine patients, no differences were observed in metaphase II oocyte maturation rates (P > 0.05).

CONCLUSIONS

This study found no significant differences in oocyte maturation, fertilization rate, embryo quality or pregnancy outcomes between luteal phase and follicular phase IVM in women with OMAs. These findings suggest that luteal phase IVM can be used similarly to follicular phase IVM, offering a potential avenue to enhance embryo yield for women with OMAs.

Oocyte in-vitro maturation primed with letrozole-HCG versus FSH-HCG in women with oocyte maturation abnormalities: a retrospective study

RESEARCH QUESTION

Are there differences between in-vitro maturation (IVM) primed with letrozole-human chorionic gonadotrophin (HCG) and IVM primed with FSH-HCG in women with oocyte maturation abnormalities (OMAs), defined as at least two failed IVF cycles where immature oocytes were retrieved?

DESIGN

This retrospective study was conducted at a private fertility clinic from January 2009 to April 2023. The final analysis included 75 women in Group 1 (IVM primed with FSH-HCG) and 52 women in Group 2 (IVM primed with letrozole-HCG).

RESULTS

A significantly higher median number of oocytes was obtained in Group 1 compared with Group 2 {9 [interquartile range (IQR) 1-5] versus 5 (IQR 1-18); P < 0.001}. However, no differences in oocyte maturation stage at collection were found between the groups (P > 0.05). At the end of IVM, Group 1 had 73/666 mature oocytes and Group 2 had 106/322 mature oocytes, and the median metaphase II oocyte rate per patient was higher in Group 2 [33.3% (IQR 66.7-100.0%) versus 0.0% (IQR 0.0-22.2%); P < 0.001]. Moreover, Group 2 demonstrated a higher median fertilization rate [66.7% (IQR 50.0-100.0%) versus 50.0% (IQR 0.0-66.7%); P = 0.027]. Group 2 had a higher proportion of Grade 2 embryos (58.5% versus 6.3%), and Group 1 had a higher proportion of Grade 3 embryos (93.8% vs 24.4%; P < 0.001). Notably, all pregnancies obtained in the study were in Group 2 (5 versus 0; P = 0.042).

CONCLUSIONS

IVM primed with letrozole-HCG in women with prior failed IVF cycles due to OMAs may result in mature oocytes, clinical pregnancies and live births. The effectiveness of letrozole priming for the subtypes of OMAs needs further investigation, with studies including greater numbers of cases.

High carrier frequency of pathogenic PATL2 gene mutations predicted in population: a bioinformatics-based approach

Topoisomerase II homologue 2 (PATL2) has been confirmed to be a key gene that contributes to oocyte maturation. However, the allele distribution and carrier frequency of these mutations remain uncharacterized. So a bioinformatics subcategory analysis of PATL2 mutations from outcome data and Single Nucleotide Polymorphism (SNP) databases was conducted. Altogether, the causative PATL2 mutation number detected in patients with oocyte maturation defects in the clinical studies and pathogenic PATL2 mutation sites predicted by software based on the database was approximately 53. The estimated carrier frequency of pathogenic mutation sites was at least 1.14‰ based on the gnomAD and ExAC database, which was approximately 1/877. The highest frequency of mutations detected in the independent patients was c.223-14_223-2del13. The carrier frequency of this mutation in the population was 0.25‰, which may be a potential threat to fertility. Estimated allele and carrier frequency are relatively higher than those predicted previously based on clinical ascertainment. A review of PATL2 mutation lineage identified in 34 patients showed that 53.81%, 9.22% and 14.72% of the oocytes with PATL2 mutations were arrested at the germinal vesicle (GV) stage, metaphase I (MI) stage and first polar body stage, respectively. Oocytes that could develop to the first polar body stage were extremely rare to fertilise, and their ultimate fate was early embryonic arrest. Phenotypic variability is related to the function of the regions and degree of loss of function of PATL2 protein. A 3D protein structure changes predicted by online tools, AlphaFold, showed aberrations at the mutation sites, which may explain partially the function loss. When the mutated and wild-type proteins are not in the same amino acid category, the protein structure will be considerably unstable. The integration of additional mutation sites with phenotypes is helpful in drawing a complete picture of the disease. Bioinformatics analysis of PATL2 mutations will help reveal molecular epidemiological characteristics and provide an important reference for new mutation assessment, genetic counselling and drug research.