In VitroAgeing of Porcine Oocytes: Changes in Phosphorylation of the Mitogen-Activated Protein Kinase (MAPK) and Parthenogenetic Activability

Epifriedelanol delays the aging of porcine oocytes matured invitro

Oocyte aging directly affects the subsequent embryonic development. Epifriedelanol is the active ingredient of Aster tataricus L.F. extract, and it possesses potential anti-cancer, anti-inflammatory and antioxidant properties. In addition, epifriedelanol can slow the aging of human skin fibroblasts. To explore the effect of epifriedelanol on the aging of porcine oocytes matured in vitro, the aging model was first established, epifriedelanol was added to in vitro maturation (IVM) medium to investigate its anti-aging effects by observing oocyte maturation and embryonic development potential, and analyzing aging-related gene expression, reactive oxygen species and mitochondrial membrane potential levels. It was found that typical aging of porcine oocytes appeared from 66 h during in vitro maturation. Compared with the 44 h group, a larger perivitelline space, increased abnormality of microtubulin formation, and significantly lower blastocyst rate were observed in the 66 h and 72 h groups. Compared with the 0 μg/mL group, the first polar body extrusion, cleavage and blastocyst rates were significantly improved (P < 0.05) in 10 μg/mL group. The expression of oocyte developmental potential-related, SIRT family-related, antioxidant and anti-apoptotic-related genes was significantly up-regulated (P < 0.05), p53 and pro-apoptotic genes were significantly down-regulated (P < 0.05). In addition, the reactive oxygen species level was significantly decreased (P < 0.01), the mitochondrial membrane potential was significantly elevated (P < 0.01) in 10 μg/mL group. In conclusion, epifriedelanol delays the aging of porcine oocytes cultured in vitro by up-regulating SIRT family gene expression, enhancing the antioxidant and anti-apoptotic capacity of oocytes.

Lab partners: oocytes, embryos and company. A personal view on aspects of oocyte maturation and the development of monozygotic twins

The present review addresses the oocyte and the preimplantation embryo, and is intended to highlight the underlying principle of the "nature versus/and nurture" question. Given the diversity in mammalian oocyte maturation, this review will not be comprehensive but instead will focus on the porcine oocyte. Historically, oogenesis was seen as the development of a passive cell nursed and determined by its somatic compartment. Currently, the advanced analysis of the cross-talk between the maternal environment and the oocyte shows a more balanced relationship: Granulosa cells nurse the oocyte, whereas the latter secretes diffusible factors that regulate proliferation and differentiation of the granulosa cells. Signal molecules of the granulosa cells either prevent the precocious initiation of meiotic maturation or enable oocyte maturation following hormonal stimulation. A similar question emerges in research on monozygotic twins or multiples: In Greek and medieval times, twins were not seen as the result of the common course of nature but were classified as faults. This seems still valid today for the rare and until now mainly unknown genesis of facultative monozygotic twins in mammals. Monozygotic twins are unique subjects for studies of the conceptus-maternal dialogue, the intra-pair similarity and dissimilarity, and the elucidation of the interplay between nature and nurture. In the course of in vivo collections of preimplantation sheep embryos and experiments on embryo splitting and other microsurgical interventions we recorded observations on double blastocysts within a single zona pellucida, double inner cell masses in zona-enclosed blastocysts and double germinal discs in elongating embryos. On the basis of these observations we add some pieces to the puzzle of the post-zygotic genesis of monozygotic twins and on maternal influences on the developing conceptus.

Marine Nemertean Worms for Immunoblotting Studies of Oocyte Aging

Immunoblotting analyses employing phospho-specific antibodies can help elucidate potential roles played by protein kinases as oocytes age and lose their ability to undergo normal fertilization. This chapter updates a previously published protocol for conducting immunoblotting analyses of oocyte maturation in marine nemertean worms by adding general methods for obtaining adult worms and for handling their gametes in experiments assessing oocyte aging.

Effect of the time interval between oocyte retrieval and ICSI on embryo development and reproductive outcomes: a systematic review

BACKGROUND

Intra-cytoplasmic sperm injection (ICSI) is used in assisted reproductive technology (ART) laboratories. However, there is no consensus regarding the precise time intervals within ICSI cycles [oocyte pick up (OPU), oocyte denudation (DN), and ICSI], and results are inconsistent and contradictory. Thus, we aim to evaluate whether there is a concordance regarding the time intervals used in different laboratories and a concrete time that gives better laboratory and reproductive results.

METHODS

A systematic review of the literature until July 25, 2020, was performed with the keywords "Oocyte Denudation/Denudation/Oocyte," "Intra-cytoplasmic Sperm Injection/ICSI," "Oocyte/Oocyte maturation/ cumulus," and "Cumulus removal/ removal." Articles and abstracts in English and involving human subjects referring to the effects of oocyte DN time on embryo development and clinical outcomes were included.

RESULTS

Of the 294 evaluated articles, 24 (including 20 full articles and 4 abstracts) were included in this review. Eighteen studies analysed the effect of OPU-DN time on embryo development and clinical outcomes. Most of these studies concluded that OPU-DN time did not influence ICSI outcomes, but some suggested that oocytes should be incubated for a short time before DN to improve oocyte maturity and enhance ICSI outcomes. In addition to reports on positive or negligible effects, adverse effects were reported in 12 studies on DN-ICSI timing. Neither OPU-DN nor DN-ICSI time could improve live birth rate.

CONCLUSIONS

Oocytes should be pre-incubated for a short duration (preferably < 4 h) before DN according to the ART laboratory schedule. More randomised controlled trials are warranted to clarify the effect of DN-ICSI timing on ICSI outcomes.

Importance of ERK1/2 in Regulation of Protein Translation during Oocyte Meiosis

Although the involvement of the extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway in the regulation of cytostatic factor (CSF) activity; as well as in microtubules organization during meiotic maturation of oocytes; has already been described in detail; rather less attention has been paid to the role of ERK1/2 in the regulation of mRNA translation. However; important data on the role of ERK1/2 in translation during oocyte meiosis have been documented. This review focuses on recent findings regarding the regulation of translation and the role of ERK1/2 in this process in the meiotic cycle of mammalian oocytes. The specific role of ERK1/2 in the regulation of mammalian target of rapamycin (mTOR); eukaryotic translation initiation factor 4E (eIF4E) and cytoplasmic polyadenylation element binding protein 1 (CPEB1) activity is addressed along with additional focus on the other key players involved in protein translation.

The potential roles of c-Jun N-terminal kinase (JNK) during the maturation and aging of oocytes produced by a marine protostome worm

Previous investigations have indicated that c-Jun N-terminal kinase (JNK) regulates the maturation and aging of oocytes produced by deuterostome animals. In order to assess the roles of this kinase in a protostome, oocytes of the marine nemertean worm Cerebratulus were stimulated to mature and subsequently aged before being probed with phospho-specific antibodies against active forms of JNK and maturation-promoting factor (MPF). Based on blots of maturing oocytes, a 40-kD putative JNK is normally activated during germinal vesicle breakdown (GVBD), which begins at 30 min post-stimulation with seawater, whereas treating immature oocytes with JNK inhibitors downregulates both the 40-kD JNK signal and GVBD, collectively suggesting a 40-kD JNK may facilitate oocyte maturation. Along with this JNK activity, mature oocytes also exhibit high levels of MPF at 2 h post-stimulation. However, by ~6-8 h post-GVBD, mature oocytes lose the 40-kD JNK signal, and at ~20-30 h of aging, an ~48-kD phospho-JNK band arises as oocytes deactivate MPF and begin to lyse during a necroptotic-like mode of death. Accordingly, JNK inhibitors reduce the aging-related 48-kD JNK phosphorylation while maintaining MPF activity and retarding oocyte degradation. Such findings suggest that a 48-kD JNK may help deactivate MPF and trigger death. Possible mechanisms by which JNK activation either together with, or independently of, protein neosynthesis might stimulate oocyte degradation are discussed.

Oocyte aging in a marine protostome worm: The roles of maturation-promoting factor and extracellular signal regulated kinase form of mitogen-activated protein kinase

The roles of maturation-promoting factor (MPF) and an extracellular signal regulated kinase form of mitogen-activated protein kinase (ERK MAPK) are analyzed during oocyte aging in the marine protostome worm Cerebratulus. About a day after removal from the ovary, unfertilized metaphase-I-arrested oocytes of Cerebratulus begin to flatten and swell before eventually lysing, thereby exhibiting characteristics of a necroptotic mode of regulated cell death. Based on immunoblots probed with phospho-specific antibodies, MPF and ERK are initially active in freshly mature specimens. However, as oocytes age, both kinase activities decline, with ERK deactivation occurring well before MPF downregulation. Experiments using pharmacological modulators indicate that oocyte degradation is promoted by the maturation-initiated activation of ERK as well as by the deactivation of MPF that occurs in extensively aged specimens. The potential significance of these findings is discussed relative to previously published results for apoptotic eggs and oocytes of echinoderm and vertebrate deuterostomes.