bims-gamemb 2022-02-06 papers

Biol Reprod. 2022 Jan 31. pii: ioac024. [Epub ahead of print]

Oocyte mitochondria - Key regulators of oocyte function and potential therapeutic targets for improving fertility.

Deepak Adhikari, In-Won Lee, Wai Shan Yuen, John Carroll.

The development of oocytes and early embryos is dependent on mitochondrial ATP production. This reliance on mitochondrial activity, together with the exclusively maternal inheritance of mitochondria in development, places mitochondria as central regulators of both fertility and transgenerational inheritance mechanisms. Mitochondrial mass and mtDNA content massively increase during oocyte growth. They are highly dynamic organelles and oocyte maturation is accompanied by mitochondrial trafficking around subcellular compartments. Due to their key roles in generation of ATP and reactive oxygen species, oocyte mitochondrial defects have largely been linked with energy deficiency and oxidative stress. Pharmacological treatments and mitochondrial supplementation have been proposed to improve oocyte quality and fertility by enhancing ATP generation and reducing reactive oxygen species levels. More recently, the role of mitochondria-derived metabolites in controlling epigenetic modifiers has provided a mechanistic basis for mitochondria-nuclear crosstalk, allowing adaptation of gene expression to specific metabolic states. Here, we discuss the multi-faceted mechanisms by which mitochondrial function influence oocyte quality, as well as longer-term developmental events within and across generations.

Keywords: Mitochondria; Oocyte; Therapeutic targets

DOI: https://doi.org/10.1093/biolre/ioac024

Hum Reprod. 2022 Feb 01. pii: deac016. [Epub ahead of print]

Fluorescence lifetime imaging microscopy (FLIM) detects differences in metabolic signatures between euploid and aneuploid human blastocysts.

Jaimin S Shah, Marta Venturas, Tim H Sanchez, Alan S Penzias, Daniel J Needleman, Denny Sakkas.

STUDY QUESTION: Can non-invasive imaging with fluorescence lifetime imaging microscopy (FLIM) detect metabolic differences in euploid versus aneuploid human blastocysts?
SUMMARY ANSWER: FLIM has identified significant metabolic differences between euploid and aneuploid blastocysts.
WHAT IS KNOWN ALREADY: Prior studies have demonstrated that FLIM can detect metabolic differences in mouse oocytes and embryos and in discarded human blastocysts.
STUDY DESIGN, SIZE, DURATION: This was a prospective observational study from August 2019 to February 2020. Embryo metabolic state was assessed using FLIM to measure the autofluorescence metabolic factors nicotinamide adenine dinucleotide dehydrogenase together with nicotinamide adenine phosphate dinucleotide dehydrogenase (NAD(P)H) and flavin adenine dinucleotide (FAD). Eight metabolic FLIM parameters were obtained from each blastocyst (four for NAD(P)H and four for FAD): short (T1) and long (T2) fluorescence lifetime, fluorescence intensity (I) and fraction of the molecules engaged with enzymes (F). The redox ratio (NAD(P)H-I)/(FAD-I) was also calculated for each image.
PARTICIPANTS/MATERIALS, SETTING, METHODS: This study was performed at a single academically affiliated centre where there were 156 discarded frozen blastocysts (n = 17 euploids; 139 aneuploids) included. Ploidy status was determined by pre-implantation genetic testing for aneuploidy (PGT-A). Discarded human blastocysts were compared using single FLIM parameters. Additionally, inner cell mass (ICM) and trophectoderm (TE) were also evaluated. Multilevel models were used for analysis. A post-hoc correction used Benjamini-Hochberg's false discovery rate, at a q-value of 0.05.
MAIN RESULTS AND THE ROLE OF CHANCE: Comparing euploid (n = 17) versus aneuploid (n = 139) embryos, a significant difference was seen in NAD(P)H-F (P < 0.04), FAD-I (P < 0.04) and redox ratio (P < 0.05). Euploid ICM (n = 15) versus aneuploid ICM (n = 119) also demonstrated significantly different signatures in NAD(P)H-F (P < 0.009), FAD-I (P < 0.03) and redox ratio (P < 0.03). Similarly, euploid TE (n = 15) versus aneuploid TE (n = 119) had significant differences in NAD(P)H-F (P < 0.0001) and FAD-I (P < 0.04).
LIMITATIONS, REASONS FOR CAUTION: This study utilized discarded human blastocysts, and these embryos may differ metabolically from non-discarded human embryos. The blastocysts analysed were vitrified after PGT-A biopsy and it is unclear how the vitrification process may affect the metabolic profile of blastocysts. Our study was also limited by the small number of rare donated euploid embryos available for analysis. Euploid embryos are very rarely discarded due to their value to patients trying to conceive, which limits their use for research purposes. However, we controlled for the imbalance with the bootstrap resampling analysis.
WIDER IMPLICATIONS OF THE FINDINGS: These findings provide preliminary evidence that FLIM may be a useful non-invasive clinical tool to assist in identifying the ploidy status of embryos.
STUDY FUNDING/COMPETING INTEREST(S): The study was supported by the Blavatnik Biomedical Accelerator Grant at Harvard University. Becker and Hickl GmbH and Boston Electronics sponsored research with the loaning of equipment for FLIM. D.J.N. is an inventor on patent US20170039415A1. There are no other conflicts of interest to declare.
TRIAL REGISTRATION NUMBER: N/A.

Keywords: FLIM; aneuploid; euploid; fluorescence lifetime imaging microscopy; mitochondria

DOI: https://doi.org/10.1093/humrep/deac016

Reprod Fertil. 2021 Dec;2(4): R113-R129

The role of mitophagy during oocyte aging in human, mouse, and Drosophila: implications for oocyte quality and mitochondrial disease.

Rachel T Cox, Joanna Poulton, Suzannah A Williams.

There is a worldwide trend for women to have their first pregnancy later in life. However, as oocyte quality declines with maternal aging, this trend leads to an increase in subfertility. The cellular mechanisms underlying this decline in oocyte competence are poorly understood. Oocyte mitochondria are the subcellular organelles that supply the energy that drives early embryogenesis, and thus their quality is critical for successful conception. Mitochondria contain their own DNA (mtDNA) and mutations in mtDNA cause mitochondrial diseases with severe symptoms, such as neurodegeneration and heart disease. Since mitochondrial function declines in tissues as humans age accompanied by an accumulation of mtDNA mutations, mtDNA is implicated as a cause of declining oocyte quality in older mothers. While this mutation load could be caused by declining accuracy of the mitochondrial replisome, age-related decline in mitochondrial quality control likely contributes, however knowledge is lacking. Mitophagy, a cellular process which specifically targets and recycles damaged mitochondria may be involved, but studies are scarce. And although assisted reproductive technologies can help older mothers, how these techniques affect the mechanisms that regulate mitochondrial and oocyte quality have not been studied. With the long-term goal of understanding the molecular mechanisms that control mitochondrial quality in the oocyte, model systems including Drosophila and mouse as well as human oocytes have been used. In this review, we explore the contribution of mitophagy to oocyte quality and the need for further systematic investigation in oocytes during maternal aging using different systems.
Lay summary: Mitochondria are small parts of cells called organelles that generate the chemical energy needed for life. Hundreds of thousands of mitochondria in the developing eggs of the mother support the initial growth and development of the fertilized egg. However, due to increasingly diminished function over time, mitochondria generate less energy as we age, posing real problems for older women considering pregnancy. It is possible that this declining energy could be responsible for declining fertility as women age. Energy may decline because mitochondria fail and the cell's way of keeping them healthy become less efficient as we age. This review summarizes what is known about mitochondrial quality control in developing eggs as they age. In the future, understanding how the best mitochondria are selected and maintained in the egg, and hence the future baby, may enable older women with or without mitochondrial problems, to have healthy children.

Keywords: ARTs; Drosophila; human; mitochondria; mitophagy; mouse; mtDNA; oocyte; ovary

DOI: https://doi.org/10.1530/RAF-21-0060

Postepy Biochem. 2021 12 31. 67(4): 340-348

Lipid metabolism and developmental potential of mammalian oocytes and embryos

Ewelina Warzych, Piotr Pawlak, Dorota Lechniak.

Developmental potential of oocytes and embryos is one of the key factors determining success in reproduction. In vitro produced embryos display reduced quality thus development of non-invasive approaches for quality assessment is a priority. Lipid metabolism belongs to fundamental mechanisms affecting reproductive processes and shaping the quality of gametes and embryos. The cytoplasm of oocytes and embryos contains specialized organelles for lipid storage (lipid droplets) whose number and size is species dependent. The growth and maturation of the oocyte/embryo is accompanied by a great fluctuation in lipid quality and quantity which in turn affects their quality and freezing suitability. There is a possibility to modify lipid parameters both in vivo and in vitro by supplementing fat to diet and culture media. The manuscript presents the current state of knowledge on lipid engagement in the process of quality acquirement by oocytes and embryos of two livestock species – cattle and pig.

DOI: https://doi.org/10.18388/pb.2021_412

Biol Reprod. 2022 Jan 29. pii: ioac022. [Epub ahead of print]

Progesterone and interferon tau regulate expression of polyamine enzymes during the ovine peri-implantation period.

Katherine M Halloran, Claire Stenhouse, Robyn M Moses, Heewon Seo, Gregory A Johnson, Guoyao Wu, Fuller W Bazer.

Progesterone (P4) and interferon tau (IFNT) are important for establishment and maintenance of pregnancy in ruminants. Agmatine and polyamines (putrescine, spermidine, and spermine) have important roles in the survival, growth, and development of mammalian conceptuses. This study tested the hypothesis that P4 and/or IFNT stimulate expression of genes and proteins involved in the metabolism and transport of polyamines in the ovine endometrium. Rambouillet ewes (n = 24) were surgically fitted with intrauterine catheters on Day 7 of the estrous cycle. They received daily intramuscular injections of 50 mg P4 in corn oil vehicle and/or 75 mg progesterone receptor antagonist (RU486) in corn oil vehicle from Days 8-15, and twice daily intrauterine injections (25 μg/uterine horn/day) of either control serum proteins (CX) or IFNT from Days 11-15, resulting in four treatment groups: 1) P4 + CX; 2) P4 + IFNT; 3) RU486 + P4 + CX; or 4) RU486 + P4 + IFNT. On Day 16, ewes were hysterectomized. The total amounts of arginine, citrulline, ornithine, agmatine, and putrescine in uterine flushings were affected (P < 0.05) by P4 and/or IFNT. P4 increased endometrial expression of SLC22A2 (P < 0.01) and SLC22A3 (P < 0.05) mRNAs. IFNT affected endometrial expression of MAT2B (P < 0.001), SAT1 (P < 0.01), and SMOX (P < 0.05) mRNAs, independent of P4. IFNT increased the abundance of SRM protein in uterine luminal (LE), superficial glandular (sGE), and glandular epithelia (GE), as well as MAT2B protein in uterine LE and sGE. These results indicate that P4 and IFNT act synergistically to regulate expression of key genes required for cell-specific metabolism and transport of polyamines in the ovine endometrium during the peri-implantation period of pregnancy.

Keywords: agmatine; amino acids; endometrium; gene expression; interferon tau; polyamines; progesterone

DOI: https://doi.org/10.1093/biolre/ioac022

Mol Biol Rep. 2022 Feb 03.

Association between the single nucleotide variants of the mitochondrial cytochrome B gene (MT-CYB) and the male infertility.

Mayyas Saleh Jaweesh, Mohamad Eid Hammadeh, Fatina W Dahadhah, Mazhar Salim Al Zoubi, Houda Amor.

BACKGROUND: Idiopathic male infertility can be attributed to genetic predispositions that affect sperm performance and function. Genetic alterations in the mitochondrial DNA (mtDNA) have been linked to certain types of male infertility and abnormal sperm function. Mutations in the mitochondrial cytochrome B (MT-CYB) gene might lead to some deficiencies in mitochondrial function. Thus, in the current study, we aimed to investigate the effect of mutations in the MT-CYB gene on sperm motility and male infertility.
METHODS AND RESULTS: Semen specimens were collected from 111 men where 67 men were subfertile and 44 were fertile. QIAamp DNA Mini Kit and REPLI-g Mitochondrial DNA Kit from QIAGEN were used to isolate and amplify the mitochondrial DNA. Followed by PCR and Sanger sequencing for the target sequence in the MT-CYP gene. Sequencing of the MT-CYB gene revealed a total of thirteen single nucleotide polymorphisms (SNPs). Eight SNPs were non-synonymous variant (missense variant) including: rs2853508, rs28357685, rs41518645, rs2853507, rs28357376, rs35070048, rs2853506, and rs28660155. While five SNPs were Synonymous variant: rs527236194, rs28357373, rs28357369, rs41504845, and rs2854124. Among these SNPs, three variants showed a significant difference in the frequency of the genotypes between subfertile and fertile groups: rs527236194 (T15784C) (P = 0.0005), rs28357373 (T15629C) (P = 0.0439), and rs41504845 (C15833T) (P = 0.0038). Moreover, two SNPs showed a significant association between allelic frequencies of rs527236194 (T15784C) (P = 0.0014) and rs41504845 (C15833T) (P = 0.0147) and male subfertility.
CONCLUSION: The current study showed a significant association between the MT-CYB gene polymorphisms and the development of male infertility. In particular, rs527236194, rs28357373 and rs41504845 variants were found to be the most related to the subfertility group. Further studies on larger and other populations are required to reveal the exact role of this gene in the development of male infertility. In addition, functional studies will be helpful to elucidate the molecular impact of the MT-CYP polymorphisms on mitochondrial function.

Keywords: Idiopathic infertility; MT-CYB; Polymorphisms; mtDNA mutation

DOI: https://doi.org/10.1007/s11033-022-07200-y

Postepy Biochem. 2021 12 31. 67(4):

The Balbiani body: morphogenesis and functioning in the oocytes of vertebrates and invertebrates

Wacław Tworzydło, Małgorzata Sekuła, Szczepan Biliński.

The Balbiani body is an organelle assemblage (termed sometimes a super-organelle) characteristic for the developing oocytes of almost all investigated animal species. In the vast majority of species, this complex resides next to the germinal vesicle and comprises such organelles as mitochondria, elements of endoplasmic reticulum, Golgi complexes as well as accumulations of nuage material. Comparative analyses have shown that the Balbiani bodies, even in closely related organisms, are often morphologically different. The differences concern not only the composition of this assemblage but also mutual relations between its components. So far, it has been found that the Balbiani body is implicated in several cellular processes undergoing in female germline cells. Most importantly this organelle complex is responsible for the delivery and localization of certain macromolecules and organelles to specific regions of the ooplasm (oocyte cytoplasm), as well as in the transfer of mitochondria to the zygote, i.e. to the next generation. Moreover, it has been shown recently that at least in some species the Balbiani body participates in the elimination of nonfunctional, damaged mitochondria from the developing oocytes and egg cells.

DOI: https://doi.org/10.18388/pb.2021_410