Maria Helena Coelho Cruz

Phytomelatonin: Assisting Plants to Survive and Thrive

This review summarizes the advances that have been made in terms of the identified functions of melatonin in plants. Melatonin is an endogenously-produced molecule in all plant species that have been investigated. Its concentration in plant organs varies in different tissues, e.g., roots versus leaves, and with their developmental stage. As in animals, the pathway of melatonin synthesis in plants utilizes tryptophan as an essential precursor molecule. Melatonin synthesis is inducible in plants when they are exposed to abiotic stresses (extremes of temperature, toxins, increased soil salinity, drought, etc.) as well as to biotic stresses (fungal infection). Melatonin aids plants in terms of root growth, leaf morphology, chlorophyll preservation and fruit development. There is also evidence that exogenously-applied melatonin improves seed germination, plant growth and crop yield and its application to plant products post-harvest shows that melatonin advances fruit ripening and may improve food quality. Since melatonin was only discovered in plants two decades ago, there is still a great deal to learn about the functional significance of melatonin in plants. It is the hope of the authors that the current review will serve as a stimulus for scientists to join the endeavor of clarifying the function of this phylogenetically-ancient molecule in plants and particularly in reference to the mechanisms by which melatonin mediates its multiple actions.

Delivery of pineal melatonin to the brain and SCN: role of canaliculi, cerebrospinal fluid, tanycytes and Virchow–Robin perivascular spaces

AbstractHistorically, the direct release of pineal melatonin into the capillary bed within the gland has been accepted as the primary route of secretion. Herein, we propose that the major route of melatonin delivery to the brain is after its direct release into the cerebrospinal fluid (CSF) of the third ventricle (3V). Melatonin concentrations in the CSF are not only much higher than in the blood, also, there is a rapid nocturnal rise at darkness onset and precipitous decline of melatonin levels at the time of lights on. Because melatonin is a potent free radical scavenger and antioxidant, we surmise that the elevated CSF levels are necessary to combat the massive free radical damage that the brain would normally endure because of its high utilization of oxygen, the parent molecule of many toxic oxygen metabolites, i.e., free radicals. Additionally, the precise rhythm of CSF melatonin provides the master circadian clock, the suprachiasmatic nucleus, with highly accurate chronobiotic information regarding the duration of the dark period. We predict that the discharge of melatonin directly into the 3V is aided by a number of epithalamic structures that have heretofore been overlooked; these include interpinealocyte canaliculi and evaginations of the posterodorsal 3V that directly abut the pineal. Moreover, the presence of tanycytes in the pineal recess and/or a discontinuous ependymal lining in the pineal recess allows melatonin ready access to the CSF. From the ventricles melatonin enters the brain by diffusion and by transport through tanycytes. Melatonin-rich CSF also circulates through the aqueduct and eventually into the subarachnoid space. From the subarachnoid space surrounding the brain, melatonin penetrates into the deepest portions of the neural tissue via the Virchow–Robin perivascular spaces from where it diffuses into the neural parenchyma. Because of the high level of pineal-derived melatonin in the CSF, all portions of the brain are better shielded from oxidative stress resulting from toxic oxygen derivatives.

Role of melatonin on production and preservation of gametes and embryos: a brief review.

The aim of this brief review is to clarify the role of melatonin in the production and preservation of mammalian gametes and embryos. Melatonin is an indoleamine synthesized from tryptophan in the pineal gland and other organs that operates as a hypothalamic-pituitary-gonadal axis modulator and regulates the waxing and waning of seasonal reproductive competence in photoperiodic mammals. A major function of the melatonin rhythm is to transmit information about the length of the daily photoperiod to the circadian and circannual systems in order to provide time-of-day and time-of-year information, respectively, to the organism. Melatonin is also a powerful antioxidant and anti-apoptotic agent, which is due to its direct scavenging of toxic oxygen derivatives and its ability to reduce the formation of reactive species. Mammalian gametes and embryos are highly vulnerable to oxidative stress due to the presence of high lipid levels; during artificial breeding procedures, these structures are exposed to dramatic changes in the microenvironment, which have a direct bearing on their function and viability. Free radicals influence the balance between oxidation-reduction reactions, disturb the transbilayer-phospholipid asymmetry of the plasma membrane and enhance lipid peroxidation. Melatonin, due to its amphiphilic nature, is undoubtedly useful in tissues by protecting them from free radical-mediated oxidative damage and cellular death. The supplementation of melatonin to semen extender or culture medium significantly improves sperm viability, oocyte competence and blastocyst development in vitro.

Clinical relevance of melatonin in ovarian and placental physiology: a review.

Abstract Within the last decade, the synthesis of melatonin in and its functions at the level of the peripheral reproductive organs has come into better focus. Melatonin is produced at several reproductive organ sites, e.g., the oocyte, ovarian follicular cells and the placental cytotrophoblasts. Moreover, these cells also contain membrane receptors for this indoleamine. In addition, via the free radical scavenging activity of melatonin and its metabolites, oxidative stress is reduced in all reproductive organ cells ensuring their optimal function. Enhancement of oocyte maturation and preservation of oocyte quality may be major functions of melatonin. Oocyte damage reduces successful fertilization and the development of a healthy fetus. The findings that melatonin protects the oocyte from toxic oxygen species have implications for improving the outcome of in vitro fertilization–embryo transfer procedures, as already shown in two published reports. Some actions of melatonin in the placenta may be context specific. Thus, melatonin is believed to function in the maintenance of optimal placental homeostasis by deferring apoptosis of villous cytotrophoblasts, while protecting syncytiotrophoblasts from oxidative damage. Melatonin reduces oxidative damage in the placenta and may improve hemodynamics and nutrient transfer at the placental–uterine interface. The use of melatonin to treat preeclampsia should also be considered.

Role of Growth Differentiation Factor 9 and Bone Morphogenetic Protein 15 in Ovarian Function and Their Importance in Mammalian Female Fertility — A Review

Growth factors play an important role during early ovarian development and folliculogenesis, since they regulate the migration of germ cells to the gonadal ridge. They also act on follicle recruitment, proliferation/atresia of granulosa cells and theca, steroidogenesis, oocyte maturation, ovulation and luteinization. Among the growth factors, the growth differentiation factor 9 (GDF9) and the bone morphogenetic protein 15 (BMP15), belong to the transforming growth factor beta (TGF-β) superfamily, have been implicated as essential for follicular development. The GDF9 and BMP15 participate in the evolution of the primordial follicle to primary follicle and play an important role in the later stages of follicular development and maturation, increasing the steroidogenic acute regulatory protein expression, plasminogen activator and luteinizing hormone receptor (LHR). These factors are also involved in the interconnections between the oocyte and surrounding cumulus cells, where they regulate absorption of amino acids, glycolysis and biosynthesis of cholesterol cumulus cells. Even though the mode of action has not been fully established, in vitro observations indicate that the factors GDF9 and BMP15 stimulate the growth of ovarian follicles and proliferation of cumulus cells through the induction of mitosis in cells and granulosa and theca expression of genes linked to follicular maturation. Thus, seeking greater understanding of the action of these growth factors on the development of oocytes, the role of GDF9 and BMP15 in ovarian function is summarized in this brief review.

HDAC inhibition decreases XIST expression on female IVP bovine blastocysts

During initial development, both X chromosomes are active in females, and one of them must be silenced at the appropriate time in order to dosage compensate their gene expression levels to male counterparts. Silencing involves epigenetic mechanisms, including histone deacetylation. Major X chromosome inactivation (XCI) in bovine occurs between hatching and implantation, although in vitro culture conditions might disrupt the silencing process, increasing or decreasing X-linked gene expression. In this study, we aimed to address the roles of histone deacetylase inhibition by trichostatin A (TSA) on female preimplantation development. We tested the hypothesis that by enhancing histone acetylation, TSA would increase the percentage of embryos achieving 16-cell stage, reducing percentage of embryos blocked at 8-cell stage, and interfere with XCI in IVF embryos. We noticed that after TSA treatment, acetylation levels in individual blastomeres of 8-16 cell embryos were increased twofold on treated embryos, and the same was detected for blastocysts. Changes among blastomere levels within the same embryo were diminished on TSA group, as low-acetylated blastomeres were no longer detected. The percentage of embryos that reached the 5th cleavage cycle 118 h after IVF, analyzed by Hoechst staining, remained unaltered after TSA treatment. Then, we assessed XIST and G6PD expression in individual female bovine blastocysts by quantitative real-time PCR. Even though G6PD expression remained unaltered after TSA exposure, XIST expression was eightfold decreased, and we also detected a major decrease in the percentage of blastocysts expressing detectable XIST levels after TSA treatment. Based on these results, we conclude that HDAC is involved on XCI process in bovine embryos, and its inhibition might delay X chromosome silencing and attenuate aberrant XIST expression described for IVF embryos.

Dual Triggering With Gonadotropin-Releasing Hormone Agonist and Standard Dose Human Chorionic Gonadotropin in Patients With a High Immature Oocyte Rate

In in vitro fertilization (IVF) cycles, some patients show a high rate of immature oocytes retrieved after controlled ovarian stimulation. In vitro oocyte maturation is an experimental technique, with poorer results than conventional IVF. For this reason, improving in vivo maturation could meliorate the reproductive outcome of these patients. We performed a retrospective, not interventional, study analyzing the difference in the number and percentage of mature oocytes retrieved in patients with more than 50% immature oocytes in a previous IVF cycle triggered with human chorionic gonadotropin (hCG) compared to the number and rate of mature oocytes retrieved in subsequent cycles, triggered with both gonadotropin-releasing hormone agonist (GnRH-a) and hCG. The number of mature oocytes retrieved with a dual trigger was significantly higher than that for hCG alone: 5.3 ± 3.6 (4.4-6.1) versus 2.4 ± 2.2 (2-2.9). The proportion of mature oocytes showed the same tendency (79.6% vs 43.6%). The implantation, clinical, and ongoing pregnancy rates were 17.3%, 26.9%, and 15.3%, respectively, for the hCG trigger and 30.8%, 43.6%, and 31.6%, respectively, for the dual trigger. In patients with a low percentage of retrieved mature oocytes, who were triggered with a combination of GnRH-a and hCG, the number and percentage of retrieved mature oocytes improved. The dual trigger also seemed to meliorate gestational outcomes after IVF.

Economic impact of ovarian stimulation with corifollitropin alfa versus conventional daily gonadotropins in oocyte donors: a randomized study

Assisted reproductive technologies are well-established treatments for many types of subfertility representing substantial economic and healthcare implications for patients, healthcare providers and society as a whole. In order to optimize outcomes according to the type of gonadotrophins within an oocyte donor programme, we performed an economic evaluation based on data collected in a multicentre, prospective, randomized study within three private clinics belonging to the IVI Group. Results showed no relevant between-group differences in the clinical variables. According to the economic analysis, ovarian stimulation with corifollitropin alfa increased the overall cost of the treatment as well as the cost per retrieved and effective oocyte, although the differences were not statistically significant. In conclusion, cost savings can be achieved using cheaper gonadotrophins during ovarian stimulation. The cost of corifollitropin alfa compared with recombinant FSH and highly purified human menopausal gonadotrophin should be considered when making treatment decisions.

Impact of very low anti-Müllerian hormone on pregnancy success

Purpose of review Biomarkers are useful tool to help clinicians to estimate the chances of pregnancy of an infertile couple prior to assisted reproductive treatment. One proposed candidate is anti-Müllerian hormone (AMH), but its role as a predictor of reproductive success, especially in patients with low or very low levels, is under discussion. This review highlights recent findings from literature regarding to reproductive outcome in women with very low levels of AMH. Recent findings Although there is a general agreement about the lower pregnancy rates of patients with very low levels of AMH compared with patients with normal AMH levels, the role of AMH as a predictor of success is still under discussion. In this sense, some authors establish a cutoff level below which the reproduction treatment is not successful; by contrast, other published data show a significant percentage of success is still observed in this group of patients, especially in young women. Summary In the following review, we discuss the usefulness of AMH as a predictor of reproductive outcome in patients with very low AMH levels and provide an update of the clinical results after assisted reproductive treatment in this group of patients. We also analyzed the different assays used to measure the AMH, focused on the differences between the manual and the new automated systems.

Real-Time Imaging Strategies to Improve Morphological Assessment

It has been more than three decades since a physician produced the first successful pregnancy through in vitro fertilization (IVF), but the success rate for a live birth still remains disappointingly low, on average round 30 %, mainly due to the low probability of an individual embryo successfully implanting in the uterus and producing a child. While transferring more than one embryo per cycle has helped to maintain IVF pregnancy rates at an acceptable level, it has also led to a dramatic rise in the number of multiple pregnancies and the subsequent risk of complications for both the mother and developing fetuses. The embryos produced in a typical IVF cycle are extremely variable in terms of their ability to form a viable pregnancy. In cases of single embryo transfer (SET) it is therefore essential that the embryo chosen for transfer is the one having the greatest potential to form a pregnancy and produce a healthy child.