on ageing-induced deterioration in mouse oocyte quality

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Oxidative stress and in vitro ageing of the post-ovulatory oocyte: an update on recent advances in the field

In brief

Post-ovulatory ageing of oocytes leads to poor oocyte and embryo quality as well as abnormalities in offspring. This review provides an update on the contributions of oxidative stress to this process and discusses the current literature surrounding the use of antioxidant media to delay post-ovulatory oocyte ageing.

Abstract

Following ovulation, the metaphase II stage oocyte has a limited functional lifespan before succumbing to a process known as post-ovulatory oocyte ageing. This progressive demise occurs both in vivo and in vitro and is accompanied by a deterioration in oocyte quality, leading to a well-defined sequelae of reduced fertilisation rates, poor embryo quality, post-implantation errors, and abnormalities in the offspring. Although the physiological consequences of post-ovulatory oocyte ageing have largely been characterised, less is known regarding the molecular mechanisms that drive this process. This review presents an update on the established relationships between the biochemical changes exhibited by the ageing oocyte and the myriad of symptoms associated with the ageing phenotype. In doing so, we consider the molecular events that are potentially involved in orchestrating post-ovulatory ageing with a particular focus on the role of oxidative stress. We highlight the mounting evidence that oxidative stress acts as an initiator for a cascade of events that create the aged oocyte phenotype. Specifically, oxidative stress has the capacity to disrupt mitochondrial function and directly damage multiple intracellular components of the oocyte such as lipids, proteins, and DNA. Finally, this review addresses emerging strategies for delaying post-ovulatory oocyte ageing with emphasis placed on the promise afforded by the use of selected antioxidants to guide the development of media tailored for the preservation of oocyte integrity during in vitro fertilisation procedures.

In vivo and in vitro postovulatory aging: when time works against oocyte quality?

In mammalian species an optimal fertilization window during which successful fertilization occurs. In the majority of mammals estrus marks ovulation time and coincident with mating, thereby allowing the synchronized meeting in the fallopian tubes, between freshly ejaculated sperm and freshly ovulated oocytes. Conversely, women do not show natural visual signs of ovulation such that fertilization can occur hours later involving an aged oocyte and freshly ejaculated spermatozoa. During this time, the oocyte undergoes a rapid degradation known as “postovulatory aging” (POA). POA may become particularly important in the human-assisted reproductive technologies, as the fertilization of retrieved mature oocytes can be delayed due to increased laboratory workload or because of unforeseeable circumstances, like the delayed availability of semen samples. This paper is an updated review of the consequences of POA, either in vivo or in vitro, on oocyte quality with particular attention to modifications caused by POA on oocyte nuclear, cytoplasmic, genomic, and epigenetic maturation, and embryo development.

L-carnitine prevents bovine oocyte aging and promotes subsequent embryonic development

L-carnitine (LC) is well known for its antioxidant activity. In this study, we explored the potential mechanistic effects of LC supplementation on aged bovine oocytes in vitro. We showed that in-vitro maturation could enhance the subsequent developmental capacity of aging oocytes, when supplemented with LC. After in vitro fertilization, the blastocyst formation rate in the aged oocytes post-LC treatment significantly increased compared to that in untreated aged oocytes (29.23 ± 2.20% vs. 20.90 ± 3.05%). Furthermore, after LC treatment, the level of intracellular reactive oxygen species in aged oocytes significantly decreased, and glutathione levels significantly increased, compared to those in untreated aged oocytes. Mitochondrial membrane potential, the percentage of early apoptotic oocytes, and caspase-3 activity were significantly reduced in LC-treated aged oocytes compared to those in untreated aged oocytes. Furthermore, during in vitro aging, the mRNA levels of the anti-apoptotic genes, Bcl-xl and survivin in LC-treated aged oocytes were significantly higher than those in untreated aged oocytes. Overall, these results indicate that at least in in vitro conditions, LC can prevent the aging of bovine oocytes and improve the developmental capacity of bovine embryo.

Laminarin enhances the quality of aged pig oocytes by reducing oxidative stress

Laminarin (LAM) is a β-glucan oligomer known to possess biological activities such as anticancer and antioxidant effects. This study explored the influence of LAM supplementation on in vitro aged porcine oocytes and the underlying mechanisms behind this influence. We found that LAM delayed the aging process and improved the quality of aged oocytes. LAM supplementation enhanced the subsequent developmental competence of aged oocytes during the in vitro aging process. The blastocyst formation rate was significantly increased in aged oocytes treated with 20 µg/ml LAM compared to non-treated aged oocytes (45.3% vs. 28.7%, P < 0.01). The mRNA levels of apoptosis-related genes, B cell lymphoma-2-associated X protein (Bax) and Caspase-3, were significantly lower in blastocysts derived from the LAM-treated aged oocytes during the in vitro aging process. Furthermore, the level of intracellular reactive oxygen species was significantly decreased and that of glutathione was significantly increased in aged oocytes following LAM treatment. Mitochondrial membrane potential was increased, and the activities of caspase-3 and cathepsin B were significantly reduced in the LAM-treated aged oocytes compared with the non-treated aged oocytes. Taken together, these results suggest that LAM is beneficial for delaying the aging process in porcine oocytes.

Ethnopharmacological properties of Artemisia asiatica: A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia asiatica Nakai (Compositae) has a long history as a traditional remedy. Preparation from various parts of the plant (aerial parts and leaves) are used to treat a wide range of diseases including gastric trouble, liver dysfunction, and skin inflammation.

AIMS OF THIS REVIEW

The aims of this review were: 1) to provide an overview of recent studies and progress on A. asiatica-derived ethnopharmacological compounds and their pharmacological activities; and 2) to summarize existing evidence and provide insight for future studies.

MATERIALS AND METHODS

This investigation was carried out by analyzing published books and research papers via scientific databases, namely Science Direct, PubMed ACS Publication, Wiley Online Library, CNKI and information obtained online. The keywords "Artemisia asiatica traditional uses," "Compounds isolated and studied in Artemisia asiatica," and "Pharmacological advances in Artemisia asiatica" were used and articles published between 1995 and 2017 were considered. In total, 500 works related to biological activities of A. asiatica were identified, and only materials published in English were included in the review.

RESULTS

Comparative analysis of literature searched through sources available confirmed that the ethnopharmacological use of A. asiatica was recorded in Korea, China, and Japan. Phytochemical studies revealed the presence of flavonoids, sesquiterpene lactones, monoterpenes, and steroids in A. asiatica. Of these, flavonoids have been shown to exhibit significant pharmacological effects such as gastroprotective, anti-inflammatory, anti-tumor, and anti-microbial actions.

CONCLUSIONS

Phytochemical and pharmacological studies of Artemisia asiatica have proven that this plant is one of valuable medicinal sources with neuroprotective, gastroprotective, anti-oxidative, anti-inflammatory, and anti-cancer effects. Although ethanol extract of this plant is now being prescribed as gastroprotective and anti-ulcerative medicine, it is now time to expand its application to other human inflammatory diseases such as pancreatitis and hepatitis and further extensive study on toxicity in human. Therefore, the present review will encourage further studies of A. asiatica in the pursuit of wide range of therapeutic remedy.