Effect of rapamycin treatment during post-activation and/or in vitro culture on embryonic development after parthenogenesis and in vitro fertilization in pigs

Addition of rapamycin or co-culture with cumulus cells from younger reproductive age women does not improve rescue in vitro oocyte maturation or euploidy rates in older reproductive age women

Both spontaneously conceived pregnancies and those achieved using assisted reproduction decline with advancing maternal age. In this study, we tested if rapamycin and/or cumulus cells (CCs) from young donors could improve oocyte maturation and euploidy rates of germinal vesicle (GV) stage oocytes obtained from older women of reproductive age. A total of 498 GVs from 201 women >38 years (40.6 ± 1.8, mean ± SD) were included. GVs were randomly assigned into five groups for rescue IVM: control (with no CCs and no rapamycin); with autologous CCs; with autologous CCs and rapamycin; with CCs from young women (<35 years); and with CCs from young women and rapamycin. After 24 h of culture, the first polar body (PB) was biopsied in metaphase II oocytes, and the cytogenetic constitution was assessed using next-generation sequencing for both oocytes and PBs. Comparable maturation rates were found (56.2%, 60.0%, 46.5%, 51.7%, and 48.5% for groups 1-5, respectively; P = 0.30). Similarly, comparable euploidy rates were observed in the five groups (41.5%, 37.8%, 47.2%, 43.6%, and 47.8% for Groups 1-5, respectively; P = 0.87). Our findings indicate that rescue IVM is effective for obtaining mature euploid oocytes in older women of reproductive age, and that incubation with rapamycin or CCs obtained from young donors does not improve the maturation or euploidy rate.

Cathepsin L regulates oocyte meiosis and preimplantation embryo development

Early embryonic loss, caused by reduced embryo developmental competence, is the major cause of subfertility in humans and animals. This embryo developmental competence is determined during oocyte maturation and the first embryo divisions. Therefore, it is essential to identify the underlying molecules regulating these critical developmental stages. Cathepsin L (CTSL), a lysosomal cysteine protease, is involved in regulating cell cycle progression, proliferation and invasion of different cell types. However, CTSL role in mammalian embryo development is unknown. Using bovine in vitro maturation and culture systems, we show that CTSL is a key regulator for embryo developmental competence. We employed a specific CTSL detection assay in live cells to show that CTSL activity correlates with meiotic progression and early embryo development. Inhibiting CTSL activity during oocyte maturation or early embryo development significantly impaired oocyte and embryo developmental competence as evidenced by lower cleavage, blastocyst and hatched blastocyst rates. Moreover, enhancing CTSL activity, using recombinant CTSL (rCTSL), during oocyte maturation or early embryo development significantly improved oocyte and embryo developmental competence. Importantly, rCTSL supplementation during oocyte maturation and early embryo development significantly improved the developmental competence of heat-shocked oocytes/embryos which are notoriously known for reduced quality. Altogether, these results provide novel evidence that CTSL plays a pivotal role in regulating oocyte meiosis and early embryonic development.

The constructive and destructive impact of autophagy on both genders' reproducibility, a comprehensive review

Reproduction is characterized by a series of massive renovations at molecular, cellular, and tissue levels. Recent studies have strongly tended to reveal the involvement of basic molecular pathways such as autophagy, a highly conserved eukaryotic cellular recycling, during reproductive processes. This review comprehensively describes the current knowledge, updated to September 2022, of autophagy contribution during reproductive processes in males including spermatogenesis, sperm motility and viability, and male sex hormones and females including germ cells and oocytes viability, ovulation, implantation, fertilization, and female sex hormones. Furthermore, the consequences of disruption in autophagic flux on the reproductive disorders including oligospermia, azoospermia, asthenozoospermia, teratozoospermia, globozoospermia, premature ovarian insufficiency, polycystic ovarian syndrome, endometriosis, and other disorders related to infertility are discussed as well.Abbreviations: AKT/protein kinase B: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ATG: autophagy related; E2: estrogen; EDs: endocrine disruptors; ER: endoplasmic reticulum; FSH: follicle stimulating hormone; FOX: forkhead box; GCs: granulosa cells; HIF: hypoxia inducible factor; IVF: in vitro fertilization; IVM: in vitro maturation; LCs: Leydig cells; LDs: lipid droplets; LH: luteinizing hormone; LRWD1: leucine rich repeats and WD repeat domain containing 1; MAP1LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MTOR: mechanistic target of rapamycin kinase; NFKB/NF-kB: nuclear factor kappa B; P4: progesterone; PCOS: polycystic ovarian syndrome; PDLIM1: PDZ and LIM domain 1; PI3K: phosphoinositide 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns3K: class III phosphatidylinositol 3-kinase; POI: premature ovarian insufficiency; ROS: reactive oxygen species; SCs: Sertoli cells; SQSTM1/p62: sequestosome 1; TSGA10: testis specific 10; TST: testosterone; VCP: vasolin containing protein.

Rapamycin encourages the maintenance of mitochondrial dynamic balance and mitophagy activity for improving developmental competence of blastocysts in porcine embryos in vitro

Rapamycin induces autophagosome formation and activity during oocyte maturation, improved fertilization ability of matured oocytes, and early embryonic developmental competence. However, potential changes in mitochondrial fission and mitophagy via regulation of autophagy in early porcine embryonic development have not been previously studied. Here, we investigated embryonic developmental ability and quality of porcine embryos 2 days after in vitro fertilization and following treatment with 1 and 10 nM rapamycin. As a results, 1 nM rapamycin exposure significantly improved (p < 0.05) blastocyst developmental competence compared to that in nontreated embryos (nontreated: 26.2 ± 5.7% vs. 1 nM rapamycin: 35.3 ± 5.1%). We observed autophagic (LC3B) and mitochondrial fission protein expression (dynamin-related protein-1 [DRP1] and pDRP1-Ser616) at the cleavage stage of 1 and 10 nM rapamycin-treated porcine embryos, using Western blot and immunofluorescence analyses. Interestingly, 1 nM rapamycin treatment significantly improved autophagy formation, mitochondrial activation, and mitochondrial fission protein levels (p < 0.05; p-DRP1 [Ser616]) at the cleavage stage of porcine embryos. Additionally, mitophagy was significantly increased in blastocysts treated with 1 nM rapamycin. In conclusion, our results suggest that rapamycin promotes blastocyst development ability in porcine embryos through mitochondrial fission, activation, and mitophagy in in vitro culture.

Metabolic and epigenetic dysfunctions underlie the arrest of in vitro fertilized human embryos in a senescent-like state

Around 60% of in vitro fertilized (IVF) human embryos irreversibly arrest before compaction between the 3- to 8-cell stage, posing a significant clinical problem. The mechanisms behind this arrest are unclear. Here, we show that the arrested embryos enter a senescent-like state, marked by cell cycle arrest, the down-regulation of ribosomes and histones and down-regulation of MYC and p53 activity. The arrested embryos can be divided into 3 types. Type I embryos fail to complete the maternal-zygotic transition, and Type II/III embryos have low levels of glycolysis and either high (Type II) or low (Type III) levels of oxidative phosphorylation. Treatment with the SIRT agonist resveratrol or nicotinamide riboside (NR) can partially rescue the arrested phenotype, which is accompanied by changes in metabolic activity. Overall, our data suggests metabolic and epigenetic dysfunctions underlie the arrest of human embryos.

Contextualizing Autophagy during Gametogenesis and Preimplantation Embryonic Development

Mammals face environmental stressors throughout their lifespan, which may jeopardize cellular homeostasis. Hence, these organisms have acquired mechanisms to cope with stressors by sensing, repairing the damage, and reallocating resources to increase the odds of long-term survival. Autophagy is a pro-survival lysosome-mediated cytoplasm degradation pathway for organelle and macromolecule recycling. Furthermore, autophagy efflux increases, and this pathway becomes idiosyncratic depending upon developmental and environmental contexts. Mammalian germ cells and preimplantation embryos are attractive models for dissecting autophagy due to their metastable phenotypes during differentiation and exposure to varying environmental cues. The aim of this review is to explore autophagy during mammalian gametogenesis, fertilization and preimplantation embryonic development by contemplating its physiological role during development, under key stressors, and within the scope of assisted reproduction technologies.

In vitro maturation on an agarose matrix improves the developmental competence of porcine oocytes

Oocytes in vivo generally mature in ovarian follicles that are soft, whereas oocytes that mature in vitro are on the hard surface of culture dishes. Embryonic ontogeny through organogenesis has greater ability in in vivo matured oocytes than it does in in vitro matured oocytes, indicating the importance of a soft culture matrix. In this study, we report the effect of using an agarose matrix as a culture substrate on the development of pig oocytes derived from medium antral follicles. The cumulus-oocyte complexes (COCs) retrieved from medium antral follicles were matured on noncoated (control) culture dishes or dishes coated with 1% and 2% (w/v) agarose matrices. Subsequently, the effect of the soft culture matrix on the developmental competence of porcine oocytes was assessed by analyzing cumulus expansion, blastocyst formation after parthenogenetic activation (PA), gene expression levels (ACTN4, BMP15, BAX, HIF1A, PFKP and VEGFA), TUNEL indices, BMP15 protein expression levels, cortical granule (CG) distribution, and intraoocyte ATP levels. In vitro maturation (IVM) of pig COCs using a 1% (w/v) agarose matrix resulted in significantly higher blastocyst formation, cumulus expansion, gene expression of BMP15, HIF1A and VEGFA, protein expression of BMP15, and intraoocyte ATP levels, and there was significantly reduced expression of a pro-apoptotic gene and ACTN4 gene and a reduction in TUNEL indices. These results demonstrate that the developmental competence of porcine oocytes can be effectively improved through IVM on a soft culture matrix made of agarose over what is observed using hard culture dishes.

Autophagy in Female Fertility: A Role in Oxidative Stress and Aging

Significance: The precipitous age-related decline in female fertility is intimately associated with a reduction in both the quantity and quality of the germline (oocytes). Although complex etiologies undoubtedly contribute to the deterioration of oocyte quality, increasing attention has focused on the pervasive impact of oxidative stress. Indeed, the prolonged lifespan of the meiotically arrested oocyte places this cell at heightened risk of oxidative lesions, which commonly manifest in dysregulation of protein homeostasis (proteostasis). Although oocytes are able to mitigate this threat via the mobilization of a sophisticated network of surveillance, repair, and proteolytic pathways, these defenses are themselves prone to age-related defects, reducing their capacity to eliminate oxidatively damaged proteins. Recent Advances: Here, we give consideration to the quality control mechanisms identified within the ovary that afford protection to the female germline. Our primary focus is to review recent advances in our understanding of the autophagy pathway and its contribution to promoting oocyte longevity and modulating pathophysiological responses to oxidative stress. In addition, we explore the therapeutic potential of emerging strategies to fortify autophagic activity. Critical Issues: The complex interplay of oxidative stress and autophagy has yet to be fully elucidated within the context of the aging oocyte and surrounding ovarian environment. Future Directions: Emerging evidence provides a strong impetus to resolve the causal link between autophagy and oxidative stress-driven pathologies in the aging oocyte. Such research may ultimately inform novel therapeutic strategies to combat the age-related loss of female fertility via fortification of intrinsic autophagic activity.

The autophagic inducer and inhibitor display different activities on the meiotic and developmental competencies of porcine oocytes derived from small and medium follicles

This study aimed to examine the effect of rapamycin (autophagy inducer) and 3-methyladenine (3-MA, autophagy inhibitor) on the meiotic and developmental competencies of porcine oocytes derived from medium follicles (MF, 3-6 mm in diameter) and small follicles (SF, 1-2 mm in diameter) during in vitro maturation (IVM) process. The presence of 1 nM but not 10 nM rapamycin significantly increased the maturation rate of MF-derived oocytes (P < 0.05). However, the maturation rate of SF-derived oocytes was not affected by rapamycin at both concentrations (1 nM and 10 nM). The maturation rate of MF-derived oocytes decreased significantly (P < 0.05) in the presence of 0.2 mM but not 2 mM 3-MA than non-supplemented control. In contrast, in SF-derived oocytes, 3-MA at both 0.2 and 2 mM concentrations did not affect the maturation rates. The presence of 1 nM rapamycin significantly increased the blastocyst formation rate of MF-derived mature oocytes following parthenogenetic activation (P < 0.05). However, the blastocyst formation rate of SF-derived mature oocytes was not affected by the presence of rapamycin. The presence of 3-MA significantly reduced the blastocyst formation rate of MF-derived mature oocytes but did not change that of SF-derived oocytes. In conclusion, our study results show differences in activity of the autophagy inducer and inhibitor on the meiotic and developmental competencies of MF- and SF-derived porcine oocytes.

Pharmacological modulation of autophagy as a novel potential target in the successful implementation of in vitro fertilization

Autophagy is an important intracellular process to maintain homeostasis and studies have shown the key role of autophagy in modulating the functions of reproductive system. Alongside with it, the activation of autophagy has also been found to regulate a number of important processes involved in in vitro fertilization including degeneration of granulosa cells and oocyte defects in obese and aging women; apoptosis of oocytes during vitrification-warming; quality and viability of embryo; developmental competence and pre-implantation development of in vitro produced blastocysts; placental vascularization and fetal growth. The different mechanisms that may contribute in autophagy-mediated increase in developmental competence and pre-implantation development include decrease in endoplasmic reticulum (ER) stress, activation of poly(ADP-ribosyl)ation (PARP) and reduction in free radical production. The present review discusses the role of autophagy activation in increasing the efficiency of in vitro fertilization by modulating different aspects related to fertilization.