A central role for ceramide in the age‐related acceleration of apoptosis in the female germline

Maturation and culture affect the metabolomic profile of oocytes and follicular cells in young and old mares

Introduction: Oocytes and follicular somatic cells within the ovarian follicle are altered during maturation and after exposure to culture in vitro. In the present study, we used a nontargeted metabolomics approach to assess changes in oocytes, cumulus cells, and granulosa cells from dominant, follicular-phase follicles in young and old mares. Methods: Samples were collected at three stages associated with oocyte maturation: (1) GV, germinal vesicle stage, prior to the induction of follicle/oocyte maturation in vivo; (2) MI, metaphase I, maturing, collected 24 h after induction of maturation in vivo; and (3) MIIC, metaphase II, mature with collection 24 h after induction of maturation in vivo plus 18 h of culture in vitro. Samples were analyzed using gas and liquid chromatography coupled to mass spectrometry only when all three stages of a specific cell type were obtained from the same mare. Results and Discussion: Significant differences in metabolite abundance were most often associated with MIIC, with some of the differences appearing to be linked to the final stage of maturation and others to exposure to culture medium. While differences occurred for many metabolite groups, some of the most notable were detected for energy and lipid metabolism and amino acid abundance. The study demonstrated that metabolomics has potential to aid in optimizing culture methods and evaluating cell culture additives to support differences in COCs associated with maternal factors.

The stromal microenvironment and ovarian aging: mechanisms and therapeutic opportunities

For decades, most studies of ovarian aging have focused on its functional units, known as follicles, which include oocytes and granulosa cells. However, in the ovarian stroma, there are a variety of somatic components that bridge the gap between general aging and ovarian senescence. Physiologically, general cell types, microvascular structures, extracellular matrix, and intercellular molecules affect folliculogenesis and corpus luteum physiology alongside the ovarian cycle. As a result of damage caused by age-related metabolite accumulation and external insults, the microenvironment of stromal cells is progressively remodeled, thus inevitably perturbing ovarian physiology. With the established platforms for follicle cryopreservation and in vitro maturation and the development of organoid research, it is desirable to develop strategies to improve the microenvironment of the follicle by targeting the perifollicular environment. In this review, we summarize the role of stromal components in ovarian aging, describing their age-related alterations and associated effects. Moreover, we list some potential techniques that may mitigate ovarian aging based on their effect on the stromal microenvironment.

Impact of NAD+ metabolism on ovarian aging

Nicotinamide adenine dinucleotide (NAD+), a crucial coenzyme in cellular redox reactions, is closely associated with age-related functional degeneration and metabolic diseases. NAD exerts direct and indirect influences on many crucial cellular functions, including metabolic pathways, DNA repair, chromatin remodeling, cellular senescence, and immune cell functionality. These cellular processes and functions are essential for maintaining tissue and metabolic homeostasis, as well as healthy aging. Causality has been elucidated between a decline in NAD levels and multiple age-related diseases, which has been confirmed by various strategies aimed at increasing NAD levels in the preclinical setting. Ovarian aging is recognized as a natural process characterized by a decline in follicle number and function, resulting in decreased estrogen production and menopause. In this regard, it is necessary to address the many factors involved in this complicated procedure, which could improve fertility in women of advanced maternal age. Concerning the decrease in NAD+ levels as ovarian aging progresses, promising and exciting results are presented for strategies using NAD+ precursors to promote NAD+ biosynthesis, which could substantially improve oocyte quality and alleviate ovarian aging. Hence, to acquire further insights into NAD+ metabolism and biology, this review aims to probe the factors affecting ovarian aging, the characteristics of NAD+ precursors, and the current research status of NAD+ supplementation in ovarian aging. Specifically, by gaining a comprehensive understanding of these aspects, we are optimistic about the prominent progress that will be made in both research and therapy related to ovarian aging.

Equine maternal aging affects the metabolomic profile of oocytes and follicular cells during different maturation time points

Introduction: Oocyte quality and fertility decline with advanced maternal age. During maturation within the ovarian follicle, the oocyte relies on the associated somatic cells, specifically cumulus and granulosa cells, to acquire essential components for developmental capacity. Methods: A nontargeted metabolomics approach was used to investigate the effects of mare age on different cell types within the dominant, follicular-phase follicle at three time points during maturation. Metabolomic analyses from single oocytes and associated cumulus and granulosa cells allowed correlations of metabolite abundance among cell types. Results and Discussion: Overall, many of the age-related changes in metabolite abundance point to Impaired mitochondrial metabolic function and oxidative stress in oocytes and follicular cells. Supporting findings include a higher abundance of glutamic acid and triglycerides and lower abundance of ceramides in oocytes and somatic follicular cells from old than young mares. Lower abundance of alanine in all follicular cell types from old mares, suggests limited anaerobic energy metabolism. The results also indicate impaired transfer of carbohydrate and free fatty acid substrates from cumulus cells to the oocytes of old mares, potentially related to disruption of transzonal projections between the cell types. The identification of age-associated alterations in the abundance of specific metabolites and their correlations among cells contribute to our understanding of follicular dysfunction with maternal aging.

Female Reproductive Aging and Oxidative Stress: Mesenchymal Stem Cell Conditioned Medium as a Promising Antioxidant

The recent tendency to delay pregnancy has increased the incidence of age-related infertility, as female reproductive competence decreases with aging. Along with aging, a lowered capacity of antioxidant defense causes a loss of normal function in the ovaries and uterus due to oxidative damage. Therefore, advancements have been made in assisted reproduction to resolve infertility caused by reproductive aging and oxidative stress, following an emphasis on their use. The application of mesenchymal stem cells (MSCs) with intensive antioxidative properties has been extensively validated as a regenerative therapy, and proceeding from original cell therapy, the therapeutic effects of stem cell conditioned medium (CM) containing paracrine factors secreted during cell culture have been reported to be as effective as that of direct treatment of source cells. In this review, we summarized the current understanding of female reproductive aging and oxidative stress and present MSC-CM, which could be developed as a promising antioxidant intervention for assisted reproductive technology.

Reprogramming of ovarian aging epigenome by resveratrol

Resveratrol is an antiaging, antioxidant, and anti-inflammatory natural polyphenolic compound. Growing evidence indicates that resveratrol has potential therapeutic effects for improving aging ovarian function. However, the mechanisms underlying prolonged reproductive longevity remain elusive. We found that resveratrol ameliorates ovarian aging transcriptome, some of which are associated with specific changes in methylome. In addition to known aging transcriptome of oocytes and granulosa cells such as decline in oxidoreductase activity, metabolism and mitochondria function, and elevated DNA damage and apoptosis, actin cytoskeleton are notably downregulated with age, and these defects are mostly rescued by resveratrol. Moreover, the aging-associated hypermethylation of actin cytoskeleton is decreased by resveratrol. In contrast, deletion of Tet2, involved in DNA demethylation, abrogates resveratrol-reprogrammed ovarian aging transcriptome. Consistently, Tet2 deficiency results in additional altered pathways as shown by increased mTOR and Wnt signaling, as well as reduced DNA repair and actin cytoskeleton with mouse age. Moreover, genes associated with oxidoreductase activity and oxidation-reduction process were hypermethylated in Tet2-deficient oocytes from middle-age mice treated with resveratrol, indicating that loss of Tet2 abolishes the antioxidant effect of resveratrol. Taking together, our finding provides a comprehensive landscape of transcriptome and epigenetic changes associated with ovarian aging that can be reprogrammed by resveratrol administration, and suggests that aberrantly increased DNA methylation by Tet2 deficiency promotes additional aging epigenome that cannot be effectively restored to younger state by resveratrol.

Ovarian aging: mechanisms and intervention strategies

Ovarian reserve is essential for fertility and influences healthy aging in women. Advanced maternal age correlates with the progressive loss of both the quantity and quality of oocytes. The molecular mechanisms and various contributing factors underlying ovarian aging have been uncovered. In this review, we highlight some of critical factors that impact oocyte quantity and quality during aging. Germ cell and follicle reserve at birth determines reproductive lifespan and timing the menopause in female mammals. Accelerated diminishing ovarian reserve leads to premature ovarian aging or insufficiency. Poor oocyte quality with increasing age could result from chromosomal cohesion deterioration and misaligned chromosomes, telomere shortening, DNA damage and associated genetic mutations, oxidative stress, mitochondrial dysfunction and epigenetic alteration. We also discuss the intervention strategies to delay ovarian aging. Both the efficacy of senotherapies by antioxidants against reproductive aging and mitochondrial therapy are discussed. Functional oocytes and ovarioids could be rejuvenated from pluripotent stem cells or somatic cells. We propose directions for future interventions. As couples increasingly begin delaying parenthood in life worldwide, understanding the molecular mechanisms during female reproductive aging and potential intervention strategies could benefit women in making earlier choices about their reproductive health.

Lacticaseibacillus rhamnosus Probio-M9 extends the lifespan of Caenorhabditis elegans

Probiotics have been characterized as useful for maintaining the balance of host gut flora and conferring health effects, but few studies have focused on their potential for delaying aging in the host. Here we show that Lacticaseibacillus rhamnosus Probio-M9 (Probio-M9), a healthy breast milk probiotic, enhances the locomotor ability and slows the decline in muscle function of the model organism Caenorhabditis elegans. Live Probio-M9 significantly extends the lifespan of C. elegans in a dietary restriction-independent manner. By screening various aging-related mutants of C. elegans, we find that Probio-M9 extends lifespan via p38 cascade and daf-2 signaling pathways, independent on daf-16 but dependent on skn-1. Probio-M9 protects and repairs damaged mitochondria by activating mitochondrial unfolded protein response. The significant increase of amino acids, sphingolipid, galactose and fatty acids in bacterial metabolites might be involved in extending the lifespan of C. elegans. We reveal that Probio-M9 as a dietary supplementation had the potential to delay aging in C. elegans and also provide new methods and insights for further analyzing probiotics in improving host health and delaying the occurrence of age-related chronic diseases.

Role of Granulosa Cells in the Aging Ovarian Landscape: A Focus on Mitochondrial and Metabolic Function

Mitochondria are at the intersection of aging and fertility, with research efforts centered largely on the role that these specialized organelles play in the relatively rapid decline in oocyte quality that occurs as females approach reproductive senescence. In addition to various roles in oocyte maturation, fertilization, and embryogenesis, mitochondria are critical to granulosa cell function. Herein, we provide a review of the literature pertaining to the role of mitochondria in granulosa cell function, with emphasis on how mitochondrial aging in granulosa cells may impact reproduction in female mammals.

DNA damage repair is suppressed in porcine aged oocytes

This study sought to evaluate DNA damage and repair in porcine postovulatory aged oocytes. The DNA damage response, which was assessed by H2A.X expression, increased in porcine aged oocytes over time. However, the aged oocytes exhibited a significant decrease in the expression of RAD51, which reflects the DNA damage repair capacity. Further experiments suggested that the DNA repair ability was suppressed by the downregulation of genes involved in the homologous recombination (HR) and nonhomologous end-joining (NHEJ) pathways. The expression levels of the cell cycle checkpoint genes, CHEK1 and CHEK2, were upregulated in porcine aged oocytes in response to induced DNA damage. Immunofluorescence results revealed that the expression level of H3K79me2 was significantly lower in porcine aged oocytes than in control oocytes. In addition, embryo quality was significantly reduced in aged oocytes, as assessed by measuring the cell proliferation capacity. Our results provide evidence that DNA damage is increased and the DNA repair ability is suppressed in porcine aged oocytes. These findings increase our understanding of the events that occur during postovulatory oocyte aging.

Reproductive aging and telomeres: Are women and men equally affected?

Successful reproduction is very important for individuals and for society. Currently, the human health span and lifespan are the object of intense and productive investigation with great achievements, compared to the last century. However, reproduction span does not progress concomitantly with lifespan. Reproductive organs age, decreasing the levels of sexual hormones, which are protectors of health through their action on several organs of the body. Thus, this is the starting point of the organismal decay and infertility. This starting point is easily detected in women. In men, it goes under the surface, undetected, but it goes, nevertheless. Regarding fertility, aging alters the hormonal equilibrium, decreases the potential of reproductive organs, diminishes the quality of the gametes and worsen the reproductive outcomes. All these events happen at a different pace and affecting different organs in women and men. The question is what molecular pathways are involved in reproductive aging and if there is a possible halting or even reversion of the aging events. Answers to all these points will be explained in the present review.

Male and female gonadal ageing: its impact on health span and life span

Ageing is linked to changes in the hypothalamic-pituitary-gonadal axis and a progressive decline in gonadal function. While women become infertile when they enter menopause, fertility decline in ageing men does not necessarily involve a complete cessation of spermatogenesis. Gonadal dysfunction in elderly people is characterized by morphological, endocrine and metabolic alterations affecting the reproductive function and quality of life. With advancing age, sexuality turns into a critical emotional and physical factor actually defining the number of years that ageing people live a healthy life. Gonadal ageing correlates with comorbidities and an increased risk of age-related diseases including diabetes, kidney problems, cardiovascular failures and cancer. This article briefly summarizes the current state of knowledge on ovarian and testicular senescence, explores the experimental models used in the study of gonadal ageing, and describes the local pro-inflammatory, oxidative and apoptotic events and the associated signalling pathways that take place in the gonads while people get older. Overall, literature reports that ageing exacerbates a mutual crosstalk among oxidative stress, apoptosis and the inflammatory response in the gonads leading to detrimental effects on fertility. Data also highlight the clinical implications of novel therapeutic interventions using antioxidant, anti-apoptotic and anti-inflammatory drugs on health span and life span.

Alteration of sphingosine-1-phosphate with aging induces contractile dysfunction of colonic smooth muscle cells via Ca2+ -activated K+ channel (BKCa ) upregulation

BACKGROUND

Age-associated changes alter calcium-activated potassium channel (BK_Ca ) expression of colon. Sphingolipids (SLs) are important cell membrane structural components; altered composition of SLs may affect BK_Ca expression. This study investigated the mechanism by which sphingosine-1-phosphate (S1P) contributes to age-associated contractile dysfunction.

METHODS

Fifty male Sprague Dawley rats of different ages were randomly assigned to five age-groups, namely 3, 6, 12, 18, and 24 months. BK_Ca expression, S1P levels, and phosphorylated myosin light chain (p-MLC) levels were tested in colonic tissues. In the absence and presence of S1P treatment, BK_Ca expression, p-MLC levels, and intracellular calcium mobilization were tested in vitro. BK_Ca small interfering RNA (siRNA) was used to investigate whether p-MLC expression and calcium mobilization were affected by BK_Ca in colonic smooth muscle cells (SMCs). The expressions of phosphorylated protein kinase B, c-Jun N-terminal kinases (JNKs), extracellular-regulated protein kinases, nuclear factor kappa-B (NF-κB), and protein kinase C_ζ (PKC_ζ ) were examined to investigate the correlation between S1P and BK_Ca .

KEY RESULTS

Sphingosine-1-phosphate levels and sphingosine-1-phosphate receptor 2 (S1PR2) and BK_Ca expressions were upregulated and p-MLC expression was downregulated in the colonic tissues, age dependently. In the cultured SMCs, S1P treatment increased BK_Ca expression and reduced calcium concentration and p-MLC was observed. BK_Ca siRNA increased calcium concentration, and p-MLC levels significantly compared with control. We also showed that S1P upregulated BK_Ca through PKC_ζ , JNK, and NF-κB pathways.

CONCLUSIONS AND INFERENCES

In conclusion, S1P and S1PR2 participate in age-associated contractile dysfunction via BK_Ca upregulation through PKC_ζ , JNK, and NF-κB pathways.

Mitofusin 2 plays a role in oocyte and follicle development, and is required to maintain ovarian follicular reserve during reproductive aging

Mitochondria change their shape through fusion and fission in order to adapt to their metabolic milieu. Mitofusin-2 (MFN2) is a key regulatory protein in this process, mediating mitochondrial fusion and interaction with endoplasmic reticulum. Targeted deletion of Mfn2 in oocytes resulted in mitochondrial dysfunction and female subfertility associated with impaired oocyte maturation and follicle development. Oocytes lacking MFN2 showed shortened telomeres and increased apoptosis, resulting in compromised oocyte quality and accelerated follicular depletion, consistent with a reproductive aging phenotype.

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.

Mitofusin 1 is required for female fertility and to maintain ovarian follicular reserve

Mitochondria are dynamic organelles that continually adapt their structure through fusion and fission in response to changes in their bioenergetic environment. Targeted deletion of mitochondrial fusion protein mitofusin1 (MFN1) in oocytes resulted in female infertility associated with failure to achieve oocyte maturation. Oocyte-granulosa cell communication was impaired, and cadherins and connexins were downregulated, resulting in follicle developmental arrest at the secondary follicle stage. Deletion of MFN1 in oocytes resulted in mitochondrial dysfunction and altered mitochondrial dynamics, as well as accumulation of ceramide, which contributed to increased apoptosis and a reproductive phenotype that was partially rescued by treatment with ceramide synthesis inhibitor myriocin. Absence of MFN1 and resulting apoptotic cell loss also caused depletion of ovarian follicular reserve, and a phenotype consistent with accelerated female reproductive aging.

Alteration of mRNA abundance, oxidation products and antioxidant enzyme activities during oocyte ageing in common carp Cyprinus carpio

Oocyte ageing is the most important factor affecting egg quality of several fish species after ovulation. Oxidative stress has been proposed as the initiator of the oocyte ageing process in other vertebrates. To identify the role of oxidative stress and apoptosis on the progress of oocyte ageing in the common carp Cyprinus carpio, changes in the relative mRNA abundance of selected transcripts were examined. The possible alteration in the oxidation status of the oocytes during ageing was also studied. In addition, the activity of antioxidant enzymes during oocyte ageing was evaluated. Oocytes from 6 females were incubated in vivo for 14 hours post-ovulation (HPO) and in vitro for 10 hours post-stripping (HPS) at 20°C before fertilization. Hatching rates were over 65% up to 4–6 HPO, finally dropping to 1.3% at 12–14 HPO.Hatching rates were over 65% up to 4–6 HPO, finally dropping to 1.3% at 12–14 HPO. Hatching rates were more than 70% for the eggs stored in vitro up to 6 HPS and then decreased to 21.3% at 10 HPS. The results demonstrated no significant changes in the relative mRNA levels of oxidative stress-related genes or genes involved in the cell cycle during the progress of oocyte ageing in common carp. Additionally, the amount of TBARS and carbonyls did not change as time elapsed following ovulation. The apoptosis-related genes however, were significantly altered following the prolonged time interval between ovulation and fertilization. The lack of response of both activities of antioxidant enzymes and oxidation products during oocyte ageing strengthens the conclusion that oxidative stress is unlikely to be a main factor determining the progress of oocyte ageing in common carp. However, an increase in the mRNA abundance of apoptosis-related genes demonstrates that apoptotic pathway might be involved in the progress of oocyte ageing.

Oocyte Aging: The Role of Cellular and Environmental Factors and Impact on Female Fertility

Female aging is one of the most important factors that impacts human reproduction. With aging, there is a natural decline in female fertility. The decrease in fertility is slow and steady in women aged 30-35 years; however, this decline is accelerated after the age of 35 due to decreases in the ovarian reserve and oocyte quality. Human oocyte aging is affected by different environmental factors, such as dietary habits and lifestyle. The ovarian microenvironment contributes to oocyte aging and longevity. The immediate oocyte microenvironment consists of the surrounding cells. Crosstalk between the oocyte and microenvironment is mediated by direct contact with surrounding cells, the extracellular matrix, and signalling molecules, including hormones, growth factors, and metabolic products. In this review, we highlight the different microenvironmental factors that accelerate human oocyte aging and decrease oocyte function. The ovarian microenvironment and the stress that is induced by environmental pollutants and a poor diet, along with other factors, impact oocyte quality and function and contribute to accelerated oocyte aging and diseases of infertility.

Sphingosine-1-phosphate reduces atresia of primordial follicles occurring during slow-freezing and thawing of human ovarian cortical strips

We aimed in this study to explore if sphingosine-1-phosphate (S1P) reduces apoptosis of primordial follicles during cryopreservation of human ovarian cortical samples. Ovarian cortical tissue fragments obtained from young patients who underwent laparoscopic excision of benign ovarian cysts were used for the experiments. The samples were slow-frozen and thawed with and without S1P at 200 and 400 μM, cultured for 1 day, and then were fixed and processed for both histomorphological assessment and detection of apoptosis with immunohistochemistry using apoptosis marker cleaved caspase-3. Follicle counts were expressed as the mean number of follicles per mm² . The mean number of primordial follicles and in vitro estradiol (E2) and anti-mullerian hormone (AMH) production of the slow-frozen and thawed samples were significantly reduced compared with fresh unfrozen samples. S1P treatment at 400 μM but not 200 μM concentration resulted in a significant increase in the number of surviving primordial follicles and in vitro E2 and AMH productions of the samples compared with their counterparts slow-frozen without S1P. We found that that there was a significant decrease in the number of primordial follicles with their oocytes stained positive for cleaved caspase-3 in the slow-frozen samples S1P 400 μM in comparison with the samples slow-frozen without S1P. These results suggest that S1P may ameliorate follicle atresia occurring in human ovarian cortical samples during cryopreservation.

Protective effects of ethanol extracts of Artemisia asiatica Nakai ex Pamp. on ageing-induced deterioration in mouse oocyte quality

Following ovulation, oocytes undergo a time-dependent deterioration in quality referred to as post-ovulatory ageing. Although various factors influence the post-ovulatory ageing of oocytes, oxidative stress is a key factor involved in deterioration of oocyte quality. Artemisia asiatica Nakai ex Pamp. has been widely used in East Asia as a food ingredient and traditional medicine for the treatment of inflammation, cancer, and microbial infections. Recent studies have shown that A. asiatica exhibits antioxidative effects. In this study, we investigated whether A. asiatica has the potential to attenuate deterioration in oocyte quality during post-ovulatory ageing. Freshly ovulated mouse oocytes were cultured with 0, 50, 100 or 200 μg/ml ethanol extracts of A. asiatica Nakai ex Pamp. After culture for up to 24 h, various ageing-induced oocyte abnormalities, including morphological changes, reactive oxygen species (ROS) accumulation, apoptosis, chromosome and spindle defects, and mitochondrial aggregation were determined. Treatment of oocytes with A. asiatica extracts reduced ageing-induced morphological changes. Moreover, A. asiatica extracts decreased ROS generation and the onset of apoptosis by preventing elevation of the Bax/Bcl-2 expression ratio during post-ovulatory ageing. Furthermore, A. asiatica extracts attenuated the ageing-induced abnormalities including spindle defects, chromosome misalignment and mitochondrial aggregation. Our results demonstrate that A. asiatica can relieve deterioration in oocyte quality and delay the onset of apoptosis during post-ovulatory ageing.

Sphingosine-1-phosphate activates the AKT pathway to inhibit chemotherapy induced human granulosa cell apoptosis

To investigate whether sphingosine-1-phosphate (S1P), an apoptosis-inhibitor would be able to inhibit chemotherapy induced human granulosa cell apoptosis. Cultures of primary granulosa cells were isolated from women undergoing in vitro fertilization (IVF). MTT assay was used to measure the optimum concentration of CTX and S1P acts on human granulosa cells. Granulosa cells were added with pertussis toxin (PTX), the PI3K inhibitor LY294002. Western blot analysis was used to analyze the signaling pathway of proteins and cell apoptosis. We found that S1P (10 mm) statistically significantly decreased granulosa cell apoptosis after cyclophosphamide (CTX) treatment. The decreased cell apoptosis induced by S1P was abolished after treatment with LY294002, PI3K inhibitor.

CONCLUSIONS

Treatment with S1P can inhibit the CTX-induced granulosa cell apoptosis. The S1P protective effect is mediated by activating the PI3K/Akt pathway.

MECHANISMS IN ENDOCRINOLOGY: Aging and anti-aging: a Combo-Endocrinology overview

Aging and its underlying pathophysiological background has always attracted the attention of the scientific society. Defined as the gradual, time-dependent, heterogeneous decline of physiological functions, aging is orchestrated by a plethora of molecular mechanisms, which vividly interact to alter body homeostasis. The ability of an organism to adjust to these alterations, in conjunction with the dynamic effect of various environmental stimuli across lifespan, promotes longevity, frailty or disease. Endocrine function undergoes major changes during aging, as well. Specifically, alterations in hormonal networks and concomitant hormonal deficits/excess, augmented by poor sensitivity of tissues to their action, take place. As hypothalamic-pituitary unit is the central regulator of crucial body functions, these alterations can be translated in significant clinical sequelae that can impair the quality of life and promote frailty and disease. Delineating the hormonal signaling alterations that occur across lifespan and exploring possible remedial interventions could possibly help us improve the quality of life of the elderly and promote longevity.

Telomere length analysis in Down syndrome birth

Human reproductive fitness depends upon telomere chemistry. Maternal age, meiotic nondisjunction error and telomere length of mother of trisomic child are someway associated. Reports exhibiting maternal inheritance of telomere length in Down syndrome child are very scanty. To investigate this, we collected peripheral blood from 170 mothers of Down syndrome child and 186 age matched mothers of euploid child with their newly born babies. Telomere length was measured by restriction digestion - southern blotting technique. Meiotic nondisjunction error was detected by STR genotyping. Subjects are classified by age (old >35 years and young ˂35 years) and by meiotic error (MI and MII). Linear regression was run to explore the age - telomere length relationship in each maternal groups. The study reveals that with age, telomere erodes in length. Old MII mothers carry the shortest (p˂0.001), control mothers have the longest telomere and MI lies in between. Babies from older mother have longer telomere (p˂0.001) moreover; telomeres are longer in Down syndrome babies than control babies (p˂0.001). To conclude, this study represents not only the relation between maternal aging and telomere length but also explore the maternal heritability of telomere length in families with Down syndrome child.

Positive and negative effects of cellular senescence during female reproductive aging and pregnancy

Cellular senescence is a phenomenon occurring when cells are no longer able to divide even after treatment with growth stimuli. Because senescent cells are typically associated with aging and age-related diseases, cellular senescence is hypothesized to contribute to the age-related decline in reproductive function. However, some data suggest that senescent cells may also be important for normal physiological functions during pregnancy. Herein, we review the positive and negative effects of cellular senescence on female reproductive aging and pregnancy. We discuss how senescent cells accelerate female reproductive aging by promoting the decline in the number of ovarian follicles and increasing complications during pregnancy. We also describe how cellular senescence plays an important role in placental and fetal development as a beneficial process, ensuring proper homeostasis during pregnancy.

Metabolites involved in cellular communication among human cumulus-oocyte-complex and sperm during in vitro fertilization

BACKGROUND

Fertilization is a key physiological process for the preservation of the species. Consequently, different mechanisms affecting the sperm and the oocyte have been developed to ensure a successful fertilization. Thus, sperm acrosome reaction is necessary for the egg coat penetration and sperm-oolema fusion. Several molecules are able to induce the sperm acrosome reaction; however, this process should be produced coordinately in time and in the space to allow the success of fertilization between gametes. The goal of this study was to analyze the metabolites secreted by cumulus-oocyte-complex (COC) to find out new components that could contribute to the induction of the human sperm acrosome reaction and other physiological processes at the time of gamete interaction and fertilization.

METHODS

For the metabolomic analysis, eighteen aliquots of medium were used in each group, containing: a) only COC before insemination and after 3 h of incubation; b) COC and capacitated spermatozoa after insemination and incubated for 16-20 hours; c) only capacitated sperm after 16-20 h in culture and d) only fertilization medium as control. Six patients undergoing assisted reproduction whose male partners provided normozoospermic samples were included in the study. Seventy-two COC were inseminated.

RESULTS

The metabolites identified were monoacylglycerol (MAG), lysophosphatidylcholine (LPC) and phytosphingosine (PHS). Analysis by PCR and in silico of the gene expression strongly suggests that the cumulus cells contribute to the formation of the PHS and LPC.

CONCLUSIONS

LPC and PHS are secreted by cumulus cells during in vitro fertilization and they could be involved in the induction of human acrosome reaction (AR). The identification of new molecules with a paracrine effect on oocytes, cumulus cells and spermatozoa will provide a better understanding of gamete interaction.

Insights into molecular features of Venerupis decussata oocytes: a microarray-based study

The production of Venerupis decussata relies on wild seed collection, which has been recently compromised due to recruitment failure and severe mortalities. To address this issue and provide an alternative source of seed, artificial spawning and larval rearing programs were developed. However, hatchery-based seed production is a relatively new industry and it is still underdeveloped. A major hurdle in the European clam seed production is the control of spawning and reproduction, which is further hindered by the impossibility of obtaining fertile gametes by gonadal "stripping", as meiosis re-initiation is constrained to a maturation process along the genital ducts. In the present study, oocytes were collected from 15 females and microarray analyses was performed to investigate gene expression profiles characterizing released and stripped ovarian oocytes. A total of 198 differentially expressed transcripts between stripped and spawned oocytes were detected. Functional analysis carried out on these transcripts highlighted the importance of a few biological processes, which are most probably implicated in the control of oocyte competence. Significant differences were observed for transcripts encoding proteins involved in meiosis progression (e.g. dual specificity phosphatase CDC25), WNT signalling (e.g. frizzled class receptor 8, wingless-type MMTV integration site family member 4), steroid synthesis (e.g. progestin and adipoQ receptor family member 3, cytochrome P450-C17), mRNA processing (e.g. zinc finger protein XlCOF28), calcium regulation (e.g. regucalcin, calmodulin) and ceramide metabolism (ceramidase B, sphingomyelinase). This study provides new information on transcriptional profiles putatively associated with ovarian egg infertility, and suggests potential mechanisms regulating early oocyte development in clams. Genes which were differentially expressed between stripped and spawned oocytes might have a pivotal role during maturation process in the gonadal duct and could be interesting targets for further functional studies aiming to make ovarian oocytes fertilizable.

Sphingolipid metabolism regulates development and lifespan in Caenorhabditis elegans

Sphingolipids are a highly conserved lipid component of cell membranes involved in the formation of lipid raft domains that house many of the receptors and cell-to-cell signaling factors involved in regulating cell division, maturation, and terminal differentiation. By measuring and manipulating sphingolipid metabolism using pharmacological and genetic tools in Caenorhabditis elegans, we provide evidence that the synthesis and remodeling of specific ceramides (e.g., dC18:1-C24:1), gangliosides (e.g., GM1-C24:1), and sphingomyelins (e.g., dC18:1-C18:1) influence development rate and lifespan. We found that the levels of fatty acid chain desaturation and elongation in many sphingolipid species increased during development and aging, with no such changes in developmentally-arrested dauer larvae or normal adults after food withdrawal (an anti-aging intervention). Pharmacological inhibitors and small interfering RNAs directed against serine palmitoyl transferase and glucosylceramide synthase acted to slow development rate, extend the reproductive period, and increase lifespan. In contrast, worms fed an egg yolk diet rich in sphingolipids exhibited accelerated development and reduced lifespan. Our findings demonstrate that sphingolipid accumulation and remodeling are critical events that determine development rate and lifespan in the nematode model, with both development rate and aging being accelerated by the synthesis of sphingomyelin, and its metabolism to ceramides and gangliosides.

Ageing, adipose tissue, fatty acids and inflammation

A common feature of ageing is the alteration in tissue distribution and composition, with a shift in fat away from lower body and subcutaneous depots to visceral and ectopic sites. Redistribution of adipose tissue towards an ectopic site can have dramatic effects on metabolic function. In skeletal muscle, increased ectopic adiposity is linked to insulin resistance through lipid mediators such as ceramide or DAG, inhibiting the insulin receptor signalling pathway. Additionally, the risk of developing cardiovascular disease is increased with elevated visceral adipose distribution. In ageing, adipose tissue becomes dysfunctional, with the pathway of differentiation of preadipocytes to mature adipocytes becoming impaired; this results in dysfunctional adipocytes less able to store fat and subsequent fat redistribution to ectopic sites. Low grade systemic inflammation is commonly observed in ageing, and may drive the adipose tissue dysfunction, as proinflammatory cytokines are capable of inhibiting adipocyte differentiation. Beyond increased ectopic adiposity, the effect of impaired adipose tissue function is an elevation in systemic free fatty acids (FFA), a common feature of many metabolic disorders. Saturated fatty acids can be regarded as the most detrimental of FFA, being capable of inducing insulin resistance and inflammation through lipid mediators such as ceramide, which can increase risk of developing atherosclerosis. Elevated FFA, in particular saturated fatty acids, maybe a driving factor for both the increased insulin resistance, cardiovascular disease risk and inflammation in older adults.

Interleukin-1 deficiency prolongs ovarian lifespan in mice

Oocyte endowment dwindles away during prepubertal and adult life until menopause occurs, and apoptosis has been identified as a central mechanism responsible for oocyte elimination. A few recent reports suggest that uncontrolled inflammation may adversely affect ovarian reserve. We tested the possible role of the proinflammatory cytokine IL-1 in the age-related exhaustion of ovarian reserve using IL-1α and IL-1β-KO mice. IL-1α-KO mice showed a substantially higher pregnancy rate and litter size compared with WT mice at advanced age. The number of secondary and antral follicles was significantly higher in 2.5-mo-old IL-1α-KO ovaries compared with WT ovaries. Serum anti-Müllerian hormone, a putative marker of ovarian reserve, was markedly higher in IL-1α-KO mice from 2.5 mo onward, along with a greater ovarian response to gonadotropins. IL-1β-KO mice displayed a comparable but more subtle prolongation of ovarian lifespan compared with IL-1α-KO mice. The protein and mRNA of both IL-1α and IL-1β mice were localized within the developing follicles (oocytes and granulosa cells), and their ovarian mRNA levels increased with age. Molecular analysis revealed decreased apoptotic signaling [higher B-cell lymphoma 2 (BCL-2) and lower BCL-2-associated X protein levels], along with a marked attenuation in the expression of genes coding for the proinflammatory cytokines IL-1β, IL-6, and TNF-α in ovaries of IL-1α-KO mice compared with WT mice. Taken together, IL-1 emerges as an important participant in the age-related exhaustion of ovarian reserve in mice, possibly by enhancing the expression of inflammatory genes and promoting apoptotic pathways.

Ovarian aging and premature ovarian failure

Physiological reproductive aging occurs as a result of a decrease in the number and quality of oocytes in ovarian cortex follicles. Although the reason for the decrease in the quality of the pool and follicular oocytes is not fully understood, endocrine, paracrine, genetic, and metabolic factors are thought to be effective. Nowadays, in order to understand the mechanisms of ovarian aging, genomic research has gained importance. The effect of co-factors, such as telomerase and ceramide, in the ovarian aging process is only getting ascertained with new research studies. The most important tests in the assessment of ovarian aging are antral follicle count and anti-Mullerian hormone.

Analysis of the phospholipid profile of metaphase II mouse oocytes undergoing vitrification

Oocyte freezing confers thermal and chemical stress upon the oolemma and various other intracellular structures due to the formation of ice crystals. The lipid profiles of oocytes and embryos are closely associated with both, the degrees of their membrane fluidity, as well as the degree of chilling and freezing injuries that may occur during cryopreservation. In spite of the importance of lipids in the process of cryopreservation, the phospholipid status in oocytes and embryos before and after freezing has not been investigated. In this study, we employed mass spectrometric analysis to examine if vitrification has an effect on the phospholipid profiles of mouse oocytes. Freshly prepared metaphase II mouse oocytes were vitrified using copper grids and stored in liquid nitrogen for 2 weeks. Fresh and vitrified-warmed oocytes were subjected to phospholipid extraction procedure. Mass spectrometric analyses revealed that multiple species of phospholipids are reduced in vitrified-warmed oocytes. LIFT analyses identified 31 underexpressed and 5 overexpressed phospholipids in vitrified mouse oocytes. The intensities of phosphatidylinositol (PI) {18∶2/16∶0} [M-H]- and phosphatidylglycerol (PG) {14∶0/18∶2} [M-H]- were decreased the most with fold changes of 30.5 and 19.1 in negative ion mode, respectively. Several sphingomyelins (SM) including SM {d38∶3} [M+H]+ and SM {d34∶0} [M+K]+ were decreased significantly in positive ion mode. Overall, the declining trend of multiple phospholipids demonstrates that vitrification has a marked effect on phospholipid profiles of oocytes. These results show that the identified phospholipids can be used as potential biomarkers of oocyte undergoing vitrification and will allow for the development of strategies to preserve phospholipids during oocyte cryopreservation.

HFE gene variants, iron, and lipids: a novel connection in Alzheimer's disease

Iron accumulation and associated oxidative stress in the brain have been consistently found in several neurodegenerative diseases. Multiple genetic studies have been undertaken to try to identify a cause of neurodegenerative diseases but direct connections have been rare. In the iron field, variants in the HFE gene that give rise to a protein involved in cellular iron regulation, are associated with iron accumulation in multiple organs including the brain. There is also substantial epidemiological, genetic, and molecular evidence of disruption of cholesterol homeostasis in several neurodegenerative diseases, in particular Alzheimer's disease (AD). Despite the efforts that have been made to identify factors that can trigger the pathological events associated with neurodegenerative diseases they remain mostly unknown. Because molecular phenotypes such as oxidative stress, synaptic failure, neuronal loss, and cognitive decline, characteristics associated with AD, have been shown to result from disruption of a number of pathways, one can easily argue that the phenotype seen may not arise from a linear sequence of events. Therefore, a multi-targeted approach is needed to understand a complex disorder like AD. This can be achieved only when knowledge about interactions between the different pathways and the potential influence of environmental factors on them becomes available. Toward this end, this review discusses what is known about the roles and interactions of iron and cholesterol in neurodegenerative diseases. It highlights the effects of gene variants of HFE (H63D- and C282Y-HFE) on iron and cholesterol metabolism and how they may contribute to understanding the etiology of complex neurodegenerative diseases.

Roles of sphingosine-1-phosphate in reproduction

Sphingosine-1-phosphate (S1P) plays crucial roles in the regulation of cell growth, proliferation, differentiation, cell survival, migration, and angiogenesis. In the reproductive system, S1P protects mammalian germ cells from irradiation or chemotherapy-induced cell death in vivo and in vitro. Moreover, S1P could improve the survival rate of thawed ovary and transplanted ovary. Furthermore, S1P could improve the developmental potential of oocyte and preimplantation embryo. In conclusion, S1P plays important roles in reproduction.

Reduced quality and accelerated follicle loss with female reproductive aging - does decline in theca dehydroepiandrosterone (DHEA) underlie the problem?

Infertility, spontaneous abortion and conception of trisomic offspring increase exponentially with age in mammals but in women there is an apparent acceleration in the rate from about age 37. The problems mostly commonly occur when the ovarian pool of follicles is depleted to a critical level with age but are also found in low follicular reserve of other etiologies. Since recent clinical studies have indicated that dehydroepiandrosterone (DHEA) supplementation may reverse the problem of oocyte quality, this review of the literature was undertaken in an attempt to find an explanation of why this is effective? In affected ovaries, oxygenation of follicular fluid is low, ultrastructural disturbances especially of mitochondria, occur in granulosa cells and oocytes, and considerable disturbances of meiosis occur. There is, however, no evidence to date that primordial follicles are compromised. In females with normal fertility, pre-antral ovarian theca cells respond to stimulation by inhibin B to provide androgen-based support for the developing follicle. With depletion of follicle numbers, inhibin B is reduced with consequent reduction in theca DHEA. Theca cells are the sole ovarian site of synthesis of DHEA, which is both a precursor of androstenedione and an essential ligand for peroxisome proliferator-activated receptor alpha (PPARα), the key promoter of genes affecting fatty acid metabolism and fat transport and genes critical to mitochondrial function. As well as inducing a plethora of deleterious changes in follicular cytoplasmic structure and function, the omega 9 palmitate/oleate ratio is increased by lowered activity of PPARα. This provides conditions for increased ceramide synthesis and follicular loss through ceramide-induced apoptosis is accelerated. In humans critical theca DHEA synthesis occurs at about 70 days prior to ovulation thus effective supplementation needs to be undertaken about four months prior to intended conception; timing which is also suggested by successful interventions to date. In humans and primates that undergo adrenarche, the adrenal zona reticularis (ZR) is the major site of DHEA production, however this is also reduced with age. Concomitant loss in function of the ZR might account for the acceleration in the rate of aging seen in humans in the late thirties' age group.

Oxidative stress and ageing of the post-ovulatory oocyte

With extended periods of time following ovulation, the metaphase II stage oocyte experiences deterioration in quality referred to as post-ovulatory oocyte ageing. Post-ovulatory ageing occurs both in vivo and in vitro and has been associated with reduced fertilization rates, poor embryo quality, post-implantation errors and abnormalities in the offspring. Although the physiological consequences of post-ovulatory oocyte ageing have largely been established, the molecular mechanisms controlling this process are not well defined. This review analyses the relationships between biochemical changes exhibited by the ageing oocyte and the symptoms associated with the ageing phenotype. We also discuss molecular events that are potentially involved in orchestrating post-ovulatory ageing with a particular focus on the role of oxidative stress. We propose that oxidative stress may act as the initiator for a cascade of events that create the aged oocyte phenotype. Specifically, oxidative stress has the capacity to cause a decline in levels of critical cell cycle factors such as maturation-promoting factor, impair calcium homoeostasis, induce mitochondrial dysfunction and directly damage multiple intracellular components of the oocyte such as lipids, proteins and DNA. Finally, this review addresses current strategies for delaying post-ovulatory oocyte ageing with a particular focus on the potential use of compounds such as caffeine or selected antioxidants in the development of more refined media for the preservation of oocyte integrity during IVF procedures.

Oxidative stress and ageing of the post-ovulatory oocyte

With extended periods of time following ovulation, the metaphase II stage oocyte experiences deterioration in quality referred to as post-ovulatory oocyte ageing. Post-ovulatory ageing occurs both in vivo and in vitro and has been associated with reduced fertilization rates, poor embryo quality, post-implantation errors and abnormalities in the offspring. Although the physiological consequences of post-ovulatory oocyte ageing have largely been established, the molecular mechanisms controlling this process are not well defined. This review analyses the relationships between biochemical changes exhibited by the ageing oocyte and the symptoms associated with the ageing phenotype. We also discuss molecular events that are potentially involved in orchestrating post-ovulatory ageing with a particular focus on the role of oxidative stress. We propose that oxidative stress may act as the initiator for a cascade of events that create the aged oocyte phenotype. Specifically, oxidative stress has the capacity to cause a decline in levels of critical cell cycle factors such as maturation-promoting factor, impair calcium homoeostasis, induce mitochondrial dysfunction and directly damage multiple intracellular components of the oocyte such as lipids, proteins and DNA. Finally, this review addresses current strategies for delaying post-ovulatory oocyte ageing with a particular focus on the potential use of compounds such as caffeine or selected antioxidants in the development of more refined media for the preservation of oocyte integrity during IVF procedures.

Melatonin prevents postovulatory oocyte aging in the mouse and extends the window for optimal fertilization in vitro

The quality of metaphase II oocytes deteriorates rapidly following ovulation as the result of an aging process associated with impaired fertilizing potential, disrupted developmental competence, and increased likelihood of embryonic resorption. Because oxidative stress accelerates the onset of apoptosis in oocytes and influences their capacity for fertilization, this study aimed to characterize the significance of such stress in the postovulatory aging of mouse oocytes in vitro. We investigated the ability of the potent antioxidant melatonin to arrest the aging process when used to supplement oocyte culture medium. This study demonstrated that oxidative stress may occur in oocytes after as little as 8 h in culture and coincides with the appearance of early apoptotic markers such as phosphatidylserine externalization, followed 16 h later by caspase activation (P < 0.05) and morphological evidence of oocyte senescence. Importantly, supplementation of oocyte culture medium with 1 mM melatonin was able to significantly relieve the time-dependent appearance of oxidative stress in oocytes (P < 0.05) and, as a result, significantly delay the onset of apoptosis (P < 0.05). Furthermore, melatonin supplementation extended the optimal window for fertilization of oocytes aged for 8 and 16 h in vitro (P < 0.05) and significantly improved the quality of the resulting embryos (P < 0.01). We conclude that melatonin may be a useful tool in a clinical setting to prevent the time-dependent deterioration of oocyte quality following prolonged culture in vitro.

Mitochondrial lipid transport at a glance

Lipids are the building blocks of cellular membranes and are synthesized at distinct parts of the cell. A precise control of lipid synthesis and distribution is crucial for cell function and survival. The endoplasmic reticulum (ER) is the major lipid-synthesizing organelle. However, a subset of lipids is synthesized within mitochondria, and this aspect has become a focus of recent lipid research. Mitochondria form a dynamic membrane network that is reshaped by fusion and fission events. Their functionality therefore depends on a continuous lipid supply from the ER and the distribution of lipids between both mitochondrial membranes. The mechanisms of mitochondrial lipid trafficking are only now emerging and appear to involve membrane contact sites and lipid transfer proteins. In this Cell Science at a Glance article, we will discuss recent discoveries in the field of mitochondrial lipid trafficking that build on long-standing observations and shed new light on the shuttling of membrane lipids between mitochondria and other organelles.

Ceramide and its transport protein (CERT) contribute to deterioration of mitochondrial structure and function in aging oocytes

In women as well as in mice, oocytes exhibit decreased developmental potential (oocyte quality) with advanced age. Our current data implicate alterations in the levels of oocyte ceramide and associated changes in mitochondrial function and structure as being prominent elements contributing to reduced oocyte quality. Both ROS levels and ATP content were significantly reduced in aged oocytes. The decreased in ROS levels are of intrigue because it is contrary to what has been previously reported. Lowered levels of both ROS and ATP indicate diminished mitochondrial function that was accompanied by alterations in mitochondrial structure. Interestingly, developmental potential of old oocytes was improved by microinjection of mitochondria isolated from young oocytes. Co-treatment of aged oocytes with ceramide and a cytoplasmic lipid carrier (l-carnitine) improved both mitochondrial morphology and function, and totally rescued spontaneous in vitro fragmentation. In addition, ceramide localization was altered in old oocytes possibly due to downregulation of the ceramide transport protein (CERT). However, knockdown of CERT alone was not sufficient to increase young oocyte's susceptibility to death, because the sequential manipulation of ceramide levels (its chronic decrease, followed by downregulation of CERT, and finally a ceramide spike) were all necessary to replicate the aging phenotype. These results indicate that oocyte aging is due to a multiplicity of events; and that with increasing biological age, changes in levels of both ceramide and its transport protein contribute to deterioration of oocyte mitochondrial structure and function. Hence, those changes may represent potential targets to manipulate when attempting to ameliorate aging phenotypes in germ cells.

Using ASMase knockout mice to model human diseases

Acid sphingomyelinase (ASMase) is a key initiator of sphingomyelin/ceramide signal transduction activated by many stress stimuli. Over the past two decades, much progress has been made in defining the clinical relevance of sphingomyelin/ceramide signaling in numerous diseases using ASMase knockout mice. Organs that operate this pathway are numerous and the disease states regulated are diverse, with ceramide generation governing injury in tumor, gut, ovary, brain, lung, heart, liver, and during infection. This chapter emphasizes evolutionary conservation of sphingolipid stress signaling and mammalian adaptations that permit transduction of organotypic responses. Recognition that the sphingomyelin/ceramide transducer calibrates extent of tissue injury, ultimately acting as a molecular switch that determines organ fate, is driving development of new pharmacologic concepts and tools to intervene therapeutically.

Current understanding of ovarian aging

The reproductive system of human female exhibits a much faster rate of aging than other body systems. Ovarian aging is thought to be dominated by a gradual decreasing numbers of follicles, coinciding with diminished quality of oocytes. Menopause is the final step in the process of ovarian aging. This review focuses on the mechanisms underlying the ovarian aging involving a poor complement of follicles at birth and a high rate of attrition each month, as well as the alternated endocrine factors. We also discuss the possible causative factors that contribute to ovarian aging, e.g., genetic factors, accumulation of irreparable damage of microenvironment, pathological effect and other factors. The appropriate and reliable methods to assess ovarian aging, such as quantification of follicles, endocrine measurement and genetic testing have also been discussed. Increased knowledge of the ovarian aging mechanisms may improve the prevention of premature ovarian failure.

Construction of conditional acid ceramidase knockout mice and in vivo effects on oocyte development and fertility

The number of resting follicles in the ovary and their successful maturation during development define the fertile female lifespan. Oocytes, enclosed within follicles, are subject to natural selection, and the majority will undergo apoptosis during prenatal life through adulthood. Our previous studies revealed high levels of the lipid hydrolase, acid ceramidase (AC), in human and mouse oocytes, follicular fluid and cumulus cells. In addition, supplementation of in vitro fertilization media with recombinant AC enhanced the survival of oocytes and preimplantation embryos. Herein we constructed and used a conditional knockout mouse model of AC deficiency (cACKO) to further investigate the role of this enzyme in oocyte survival in vivo. Immunohistochemical staining, activity assays, and western blot analysis revealed that AC expression was high in the ovaries of normal mice, particularly in the theca cells. After induction of the AC gene knockout with tamoxifen (TM), AC levels decreased in ovaries, and ceramide was correspondingly elevated. A novel immunostaining method was developed to visualize follicles at various stages, and together with light microscopic examination, the transition of the follicle from the secondary to antral stage was found to be defective in the absence of AC. Western blot analysis showed elevated BAX and PARP expression in TM-treated cACKO mouse ovaries compared to control animals. In parallel, the levels of BCL-2 and anti-Mullerian hormone, a marker of ovarian reserve, were decreased. In addition to the above, there was a significant decrease in fertility observed in the TM-treated cACKO mice. Together, these data suggest that AC plays an important role in the preservation of fertility by maintaining low ceramide levels and preventing apoptosis of theca cells, thereby promoting survival of the follicle during the transition from the secondary to antral stage.

NLRP5 mediates mitochondrial function in mouse oocytes and embryos

Unraveling molecular pathways responsible for regulation of early embryonic development is crucial for our understanding of female infertility. Maternal determinants that control the transition from oocyte to embryo are crucial molecules that govern developmental competence of the newly conceived zygote. We describe a series of defects that are triggered by a disruption of maternal lethal effect gene, Nlrp5. Previous studies have shown that Nlrp5 hypomorph embryos fail to develop beyond the two-cell stage. Despite its importance in preimplantation development, the mechanism by which the embryo arrest occurs remains unclear. We confirmed that Nlrp5 mutant and wild-type females possess comparable ovarian germ pool and follicular recruitment rates. However, ovulated oocytes lacking Nlrp5 have abnormal mitochondrial localization and increased activity in order to sustain physiological ATP content. This results in an accumulation of reactive oxygen species and increased cellular stress causing mitochondrial depletion. Compromised cellular state is also accompanied by increased expression of cell death inducer Bax and depletion of cytochrome c. However, neither genetic deletion (Bax/Nlrp5 double knockout) nor mimetic interference (BH4 domain or Bax inhibitory peptide) were sufficient to alleviate embryo demise caused by depletion of Nlrp5. We therefore conclude that lack of Nlrp5 in oocytes triggers premature activation of the mitochondrial pool, causing mitochondrial damage that cannot be rescued by inactivation of Bax.

RAD51 plays a crucial role in halting cell death program induced by ionizing radiation in bovine oocytes

Reproductive health of humans and animals exposed to daily irradiants from solar/cosmic particles remains largely understudied. We evaluated the sensitivities of bovine and mouse oocytes to bombardment by krypton-78 (1 Gy) or ultraviolet B (UV-B; 100 microjoules). Mouse oocytes responded to irradiation by undergoing massive activation of caspases, rapid loss of energy without cytochrome-c release, and subsequent necrotic death. In contrast, bovine oocytes became positive for annexin-V, exhibited cytochrome-c release, and displayed mild activation of caspases and downstream DNAses but with the absence of a complete cell death program; therefore, cytoplasmic fragmentation was never observed. However, massive cytoplasmic fragmentation and increased DNA damage were induced experimentally by both inhibiting RAD51 and increasing caspase 3 activity before irradiation. Microinjection of recombinant human RAD51 prior to irradiation markedly decreased both cytoplasmic fragmentation and DNA damage in both bovine and mouse oocytes. RAD51 response to damaged DNA occurred faster in bovine oocytes than in mouse oocytes. Therefore, we conclude that upon exposure to irradiation, bovine oocytes create a physiologically indeterminate state of partial cell death, attributed to rapid induction of DNA repair and low activation of caspases. The persistence of these damaged cells may represent an adaptive mechanism with potential implications for livestock productivity and long-term health risks associated with human activity in space.

Ceramide and mitochondrial function in aging oocytes: joggling a new hypothesis and old players

Maternal aging adversely affects oocyte quality (function and developmental potential) and consequently lowers pregnancy rates while increasing spontaneous abortions. Substantial evidence, especially from egg donation studies, implicates the decreased quality of an aging oocyte as a major factor in the etiology of female infertility. Nevertheless, the cellular and molecular mechanisms responsible for the decreased oocyte quality with advanced maternal aging are not fully characterized. Herein we present information in the published literature and our own data to support the hypothesis that during aging induced decreases in mitochondrial ceramide levels and associated alterations in mitochondrial structure and function are prominent elements contributing to reduced oocyte quality. Hence, by examining the molecular determinants that underlie impairments in oocyte mitochondria, we expect to sieve to a better understanding of the mechanistic anatomy of oocyte aging.

Prohibitin (PHB) acts as a potent survival factor against ceramide induced apoptosis in rat granulosa cells

AIM

Ceramide is a key factor in inducing germ cell apoptosis by translocating from cumulus cells into the adjacent oocyte and lipid rafts through gap junctions. Therefore studies designed to elucidate the mechanistic pathways in ceramide induced granulosa cell (GC) apoptosis and follicular atresia may potentially lead to the development of novel lipid-based therapeutic strategies that will prevent infertility and premature menopause associated with chemo and/or radiation therapy in female cancer patients. Our previous studies have shown that Prohibitin (PHB) is intimately involved in GCs differentiation, atresia, and luteolysis.

MAIN METHODS

In the present study, we have examined the functional effects of loss-/gain-of-function of PHB using adenoviral technology in delaying apoptosis induced by the physiological ligand ceramide in rat GCs.

KEY FINDINGS

Under these experimental conditions, exogenous ceramide C-8 (50 μM) augmented the expression of mitochondrial PHB and subsequently cause the physical destruction of GC by the release of mitochondrial cytochrome c and activation of caspase-3. In further studies, silencing of PHB expression by adenoviral small interfering RNA (shRNA) sensitized GCs to ceramide C8-induce apoptosis. In contrast, adenovirus (Ad) directed overexpression of PHB in GCs resulted in increased PHB content in mitochondria and delayed the onset of ceramide induced apoptosis in the infected GCs.

SIGNIFICANCE

Taken together, these results provide novel evidences that a critical level of PHB expression within the mitochondria plays a key intra-molecular role in GC fate by mediating the inhibition of apoptosis and may therefore, contribute significantly to ceramide induced follicular atresia.

Chemotherapy-induced late transgenerational effects in mice

To our knowledge, there is no report on long-term reproductive and developmental side effects in the offspring of mothers treated with a widely used chemotherapeutic drug such as doxorubicin (DXR), and neither is there information on transmission of any detrimental effects to several filial generations. Therefore, the purpose of the present paper was to examine the long-term effects of a single intraperitoneal injection of DXR on the reproductive and behavioral performance of adult female mice and their progeny. C57BL/6 female mice (generation zero; G0) were treated with either a single intraperitoneal injection of DXR (G0-DXR) or saline (G0-CON). Data were collected on multiple reproductive parameters and behavioral analysis for anxiety, despair and depression. In addition, the reproductive capacity and health of the subsequent six generations were evaluated. G0-DXR females developed despair-like behaviors; delivery complications; decreased primordial follicle pool; and early lost of reproductive capacity. Surprisingly, the DXR-induced effects in oocytes were transmitted transgenerationally; the most striking effects being observed in G4 and G6, constituting: increased rates of neonatal death; physical malformations; chromosomal abnormalities (particularly deletions on chromosome 10); and death of mothers due to delivery complications. None of these effects were seen in control females of the same generations. Long-term effects of DXR in female mice and their offspring can be attributed to genetic alterations or cell-killing events in oocytes or, presumably, to toxicosis in non-ovarian tissues. Results from the rodent model emphasize the need for retrospective and long-term prospective studies of survivors of cancer treatment and their offspring.