Mitochondrial DNA in Fresh versus Frozen Embryo Culture Media of Polycystic Ovarian Syndrome Patients Undergoing Invitro Fertilization: A Possible Predictive Marker of a Successful Pregnancy

Abnormal amino acid synthesis and glutathione metabolism may affect PCOS blastocyst development: an examination of in vitro mouse blastocysts model utilizing RNA-sequencing

BACKGROUND

Extensive research has been conducted on embryonic developmental disorders linked to Polycystic Ovary Syndrome (PCOS), a pathological condition that affects 5-10% of women and is characterized by irregularities in the menstrual cycle and infertility. By employing RNA sequencing (RNA-seq), we performed an in-depth investigation of PCOS-related changes in gene expression patterns at the mouse blastocyst stage.

METHODS

The zygotes of female B6D2 mice were obtained and then differentiated into blastocysts in K + Simplex Optimised Medium (KSOM) cultures containing exo-NC (negative control for exosomes) or exo-LIPE-AS1 (a novel exosomal marker of PCOS). Subsequently, blastocysts were collected for RNA-seq. The bioinformatics was performed to analyze and compare the differences of gene expression profile between blastocysts of control and PCOS group.

RESULTS

There were 1150 differentially expressed genes (DEGs) between the two groups of mouse blastocysts; 243 genes were upregulated and 907 downregulated in the blastocysts of the exo-LIPE-AS1 group compared to those of the exo-NC group. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the genes involved in amino acid synthesis and glutathione metabolic pathways were down-regulated in exo-LIPE-AS1 group.

CONCLUSION

This study has revealed that blastocyst developmental retardation may be associated with the downregulation of amino acid synthesis and glutathione metabolism, which may affect energy metabolism, biosynthesis, cellular osmotic pressure, antioxidant synthesis, ROS clearance or mitochondrial function, and ultimately cause blastocyst cell development abnormalities. Our research offers encouraging data on the mechanisms underlying aberrant embryonic development in patients with PCOS as well as potential treatment strategies.

Adverse effects of ovarian cryopreservation and auto-transplantation on ovarian grafts and quality of produced oocytes in a mouse model

The process of ovarian cryopreservation and transplantation is the only feasible fertility preservation method for prepubertal girls and female patients with cancer who cannot delay radiotherapy and chemotherapy. However, basic research on this technique is lacking. To better understand ovarian function and oocyte quality after ovarian tissue (OT) transplantation, we characterised the appearance, angiogenesis, and endocrine function of ovarian grafts in a murine model; the mitochondrial function and DNA damage in oocytes isolated from the OT; and the development of embryos after in vitro fertilisation. The results showed a decrease in oocyte numbers in the transplanted OT, abnormal endocrine function of ovarian grafts, as well as dysfunctional mitochondria and DNA damage in the oocytes, which could adversely affect subsequent embryonic development. However, these adverse phenotypes were partially or completely resolved within 21 days of transplantation, suggesting that ovulation induction and assisted pregnancy treatment should not be conducted too soon after OT transfer to ensure optimal patient and offspring outcomes.

Digital PCR Detection of mtDNA/gDNA Ratio in Embryo Culture Medium for Prediction of Embryo Development Potential

PURPOSE

The ratio of mitochondrial DNA to genomic DNA (mtDNA/gDNA) in embryo culture medium as a predictor of embryonic development is a new method of noninvasive embryo screening. However, current tests based on this concept have proven inconsistent. The aim of this study was to define the predictive value of the ratio of mtDNA/gDNA for embryonic developmental potential.

MATERIALS AND METHODS

We used digital PCR to measure mtDNA/gDNA ratios in day 3 culture media of 223 embryos from 56 patients. We compared the relationship between the predictive value of mtDNA/gDNA ratio and each of embryo fragmentation, embryo morphological grade, and blastocyst formation.

RESULTS

mtDNA/gDNA ratio decreased significantly with a decrease in embryo rating: 22.54 (44.66); 31.25 (36.97) and 46.33 (57.11); Grades A vs C, P = 0.006; B vs C, P = 0.015. mtDNA/gDNA ratio increased overall with an increase in embryo fragment content but did not differ significantly between high-, -medium, and poor-quality embryos. Interestingly, this trend differed from that of the unformed blastocysts. mtDNA/gDNA ratio of cleavage stage embryos forming blastocysts was lower (P=0.005). Trends of mtDNA/gDNA ratio differed according to inner cell mass (ICM) and trophectoderm (TE) levels, but not significantly. mtDNA/gDNA ratio in day 3 culture medium was not significantly improved over morphological scores.

CONCLUSION

We hereby show the correlation of mtDNA/gDNA ratio in the culture medium of developing embryos. The correlation between the mtDNA/gDNA ratio and early embryonic development was controversial. Furthermore, an increase in mtDNA/gDNA ratio might indicate reduced development potential, but the difference remains insufficient for application as a clinical predictor.