Assisted reproductive technology results: Why are live-birth percentages so low?

Telomere dynamics and reproduction

The oocyte, a long-lived, postmitotic cell, is the locus of reproductive aging in women. Female germ cells replicate only during fetal life and age throughout reproductive life. Mechanisms of oocyte aging include the accumulation of oxidative damage, mitochondrial dysfunction, and disruption of proteins, including cohesion. Nobel Laureate Bob Edwards also discovered a "production line" during oogonial replication in the mouse, wherein the last oocytes to ovulate in the adult-derived from the last oogonia to exit mitotic replication in the fetus. On the basis of this, we proposed a two-hit "telomere theory of reproductive aging" to integrate the myriad features of oocyte aging. The first hit was that oocytes remaining in older women traversed more cell cycles during fetal oogenesis. The second hit was that oocytes accumulated more environmental and endogenous oxidative damage throughout the life of the woman. Telomeres (Ts) could mediate both of these aspects of oocyte aging. Telomeres provide a "mitotic clock," with T attrition an inevitable consequence of cell division because of the end replication problem. Telomere's guanine-rich sequence renders them especially sensitive to oxidative damage, even in postmitotic cells. Telomerase, the reverse transcriptase that restores Ts, is better at maintaining than elongating T. Moreover, telomerase remains inactive during much of oogenesis and early development. Oocytes are left with short Ts, on the brink of viability. In support of this theory, mice with induced T attrition and women with naturally occurring telomeropathy suffer diminished ovarian reserve, abnormal embryo development, and infertility. In contrast, sperm are produced throughout the life of the male by a telomerase-active progenitor, spermatogonia, resulting in the longest Ts in the body. In mice, cleavage-stage embryos elongate Ts via "alternative lengthening of telomeres," a recombination-based mechanism rarely encountered outside of telomerase-deficient cancers. Many questions about Ts and reproduction are raised by these findings: does the "normal" T attrition observed in human oocytes contribute to their extraordinarily high rate of meiotic nondisjunction? Does recombination-based T elongation render embryos susceptible to mitotic nondisjunction (and mosaicism)? Can some features of Ts serve as markers of oocyte quality?

It Is Premature to Use Postmortem Sperm for Reproductive Purposes: a Data-Driven Opinion

Postmortem sperm retrieval for reproductive purposes is an assisted reproduction procedure that offers women an opportunity to have a child using sperm retrieved from their deceased partners. The ethical issues of this procedure have been discussed in previous works. However, an assessment of the procedure using a scientific perspective is still lacking. Here, we aim to ascertain, using a biological standpoint, whether postmortem sperm should be rescued for reproductive purposes. Data suggest that it is premature to use postmortem sperm for reproductive purposes. This procedure should not be clinically applied until appropriate and comprehensive analyses have been completed. Such analyses should be focused not only on fertilization, embryo development, and pregnancy outcomes, but also on potential postmortem alterations of sperm DNA, RNAs, and proteins. In addition, genetic and epigenetic analyses of sperm, pre-implantation embryos, and newborns, as well as mental and physical health follow-up of the resulting offspring during a whole life cycle, using appropriate non-human mammalian models, are warranted.

Quantitative proteome profiling reveals molecular hallmarks of egg quality in Atlantic halibut: impairments of transcription and protein folding impede protein and energy homeostasis during early development

Background

Tandem mass tag spectrometry (TMT labeling-LC-MS/MS) was utilized to examine the global proteomes of Atlantic halibut eggs at the 1-cell-stage post fertilization. Comparisons were made between eggs judged to be of good quality (GQ) versus poor quality (BQ) as evidenced by their subsequent rates of survival for 12 days. Altered abundance of selected proteins in BQ eggs was confirmed by parallel reaction monitoring spectrometry (PRM-LC-MS/MS). Correspondence of protein levels to expression of related gene transcripts was examined via qPCR. Potential mitochondrial differences between GQ and BQ eggs were assessed by transmission electron microscopy (TEM) and measurements of mitochondrial DNA (mtDNA) levels.

Results

A total of 115 proteins were found to be differentially abundant between GQ and BQ eggs. Frequency distributions of these proteins indicated higher protein folding activity in GQ eggs compared to higher transcription and protein degradation activities in BQ eggs. BQ eggs were also significantly enriched with proteins related to mitochondrial structure and biogenesis. Quantitative differences in abundance of several proteins with parallel differences in their transcript levels were confirmed in egg samples obtained over three consecutive reproductive seasons. The observed disparities in global proteome profiles suggest impairment of protein and energy homeostasis related to unfolded protein response and mitochondrial stress in BQ eggs. TEM revealed BQ eggs to contain significantly higher numbers of mitochondria, but differences in corresponding genomic mtDNA (mt-nd5 and mt-atp6) levels were not significant. Mitochondria from BQ eggs were significantly smaller with a more irregular shape and a higher number of cristae than those from GQ eggs.

Conclusion

The results of this study indicate that BQ Atlantic halibut eggs are impaired at both transcription and translation levels leading to endoplasmic reticulum and mitochondrial disorders. Observation of these irregularities over three consecutive reproductive seasons in BQ eggs from females of diverse background, age and reproductive experience indicates that they are a hallmark of poor egg quality. Additional research is needed to discover when in oogenesis and under what circumstances these defects may arise. The prevalence of this suite of markers in BQ eggs of diverse vertebrate species also begs investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08859-0.

Mesenchymal Stem Cells in Preclinical Infertility Cytotherapy: A Retrospective Review

Infertility is a global reproductive disorder which is caused by a variety of complex diseases. Infertility affects the individual, family, and community through physical, psychological, social and economic consequences. The results from recent preclinical studies regarding stem cell-based therapies are promising. Stem cell-based therapies cast a new hope for infertility treatment as a replacement or regeneration strategy. The main features and application prospects of mesenchymal stem cells in the future of infertility should be understood by clinicians. Mesenchymal stem cells (MSCs) are multipotent stem cells with abundant source, active proliferation, and multidirectional differentiation potential. MSCs play a role through cell homing, secretion of active factors, and participation in immune regulation. Another advantage is that, compared with embryonic stem cells, there are fewer ethical factors involved in the application of MSCs. However, a number of questions remain to be answered prior to safe and effective clinical application. In this review, we summarized the recent status of MSCs in the application of the diseases related to or may cause to infertility and suggest a possible direction for future cytotherapy to infertility.

Genetic instability and anti-HPV immune response as drivers of infertility associated with HPV infection

Human papillomavirus (HPV) is a sexually transmitted infection common among men and women of reproductive age worldwide. HPV viruses are associated with epithelial lesions and cancers. HPV infections have been shown to be significantly associated with many adverse effects in reproductive function. Infection with HPVs, specifically of high-oncogenic risk types (HR HPVs), affects different stages of human reproduction, resulting in a series of adverse outcomes: 1) reduction of male fertility (male infertility), characterized by qualitative and quantitative semen alterations; 2) impairment of couple fertility with increase of blastocyst apoptosis and reduction of endometrial implantation of trophoblastic cells; 3) defects of embryos and fetal development, with increase of spontaneous abortion and spontaneous preterm birth. The actual molecular mechanism(s) by which HPV infection is involved remain unclear. HPV-associated infertility as Janus, has two faces: one reflecting anti-HPV immunity, and the other, direct pathogenic effects of HPVs, specifically, of HR HPVs on the infected/HPV-replicating cells. Adverse effects observed for HR HPVs differ depending on the genotype of infecting virus, reflecting differential response of the host immune system as well as functional differences between HPVs and their individual proteins/antigens, including their ability to induce genetic instability/DNA damage. Review summarizes HPV involvement in all reproductive stages, evaluate the adverse role(s) played by HPVs, and identifies mechanisms of viral pathogenicity, common as well as specific for each stage of the reproduction process.

Reproductive Outcomes from Maternal Loss of Nlrp2 Are Not Improved by IVF or Embryo Transfer Consistent with Oocyte-Specific Defect

Nlrp2 encodes a protein of the oocyte subcortical maternal complex (SCMC), required for embryo development. We previously showed that loss of maternal Nlrp2 in mice causes subfertility, smaller litters with birth defects, and growth abnormalities in offspring, indicating that Nlrp2 is a maternal effect gene and that all embryos from Nlrp2-deficient females that were cultured in vitro arrested before the blastocysts stage. Here, we used time-lapse microscopy to examine the development of cultured embryos from superovulated Nlrp2-deficient and wild-type mice after in vivo and in vitro fertilization. Embryos from Nlrp2-deficient females had similar abnormal cleavage and fragmentation and arrested by blastocyst stage, irrespective of fertilization mode. This indicates that in vitro fertilization does not further perturb or improve the development of cultured embryos. We also transferred embryos from superovulated Nlrp2-deficient and wild-type females to wild-type recipients to investigate if the abnormal reproductive outcomes of Nlrp2-deficient females are primarily driven by oocyte dysfunction or if a suboptimal intra-uterine milieu is a necessary factor. Pregnancies with transferred embryos from Nlrp2-deficient females produced smaller litters, stillbirths, and offspring with birth defects and growth abnormalities. This indicates that the reproductive phenotype is oocyte-specific and is not rescued by development in a wild-type uterus. We further found abnormal DNA methylation at two maternally imprinted loci in the kidney of surviving young adult offspring, confirming persistent DNA methylation disturbances in surviving offspring. These findings have implications for fertility treatments for women with mutations in NLRP2 and other genes encoding SCMC proteins.

Predictors of live birth in women with a history of biochemical pregnancies after assisted reproduction treatment

OBJECTIVES

To ascertain whether women with a history of biochemical pregnancies (BPs) in in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) treatment cycles have decreased chances of live birth (LB); and (2) to build a predictive model for LB in this particular population of infertile women.

METHODS

In order to achieve the first objective, data from 1536 women that had a LB using autologous fresh or frozen embryos, or dropped out of further IVF/ICSI treatments after completing one to three unsuccessful treatment cycles were retrospectively analyzed. A subpopulation of 90 women that experienced one or more BPs in our assisted reproduction unit were selected to build a predictive logistic regression model for LB.

RESULTS

LB percentages significantly decreased from a value of 55.3 % in women with no history of previous BPs to 30.9 % and 11.1 % in women that displayed a history of one or more than one BP, respectively. Three out of 35 selected potential predictors were finally included into the model: "number of the last embryo transfer cycle resulting in a BP", "women's age", and "oligo-, astheno-, and/or teratozoospermia". The value of the c-statistic was 0.819 (asymptotic 95 % CI: 0.724-0.913). The model adequately fitted the data with no significant over or underestimation of predictor effects.

CONCLUSION

(1) A history of BPs is negatively associated with later chance of LB in women undergoing a series of IVF/ICSI treatment cycles; and (2) LB probability of women with a history of BPs can be predicted using a model with excellent discriminatory capacity.

Cumulative probabilities of live birth across multiple complete IVF/ICSI cycles: a call for attention

PURPOSE

To call attention to the fact that cumulative live birth (LB) proportions exhibit an inverted pattern to that displayed by each individual oocyte retrieval cycle (ORC-specific LB proportions) as well as when grouping together all the ORCs undergone by a woman (TNORC-specific LB proportions).

METHODS

A retrospective study of 1433 infertile women that had a LB using autologous fresh or frozen embryos and/or dropped out of IVF/ICSI treatment after completing a maximum number of three treatment cycles. Generalized Estimating Equations (GEE) and standard and landmark Kaplan-Meier survival analyses were applied.

RESULTS

A standard Kaplan-Meier analysis indicated that cumulative LB proportions rose as number of ORCs increased (0.320, 0.484, and 0.550 at ORC 1, 2, and 3, respectively). In contrast, landmark ORC-specific LB proportions showed an inverted pattern (0.320, 0.242, and 0.127 at ORC 1, 2, and 3, respectively). GEE models revealed that women's clinical outcomes decreased as TNORCs increased. In particular, compared to women that experienced just one ORC, women that underwent two and three ORCs displayed higher incidences of cycle cancellations before either oocyte retrieval or embryo transfer, and clinical pregnancy losses, and lower odds of LB.

CONCLUSION

Infertile women should be informed that cumulative LB probabilities exhibit an inverted pattern to that displayed by each individual ORC as well as when grouping together all the ORCs undergone by a woman.

Does the molecular and metabolic profile of human granulosa cells correlate with oocyte fate? New insights by Fourier transform infrared microspectroscopy analysis

STUDY QUESTION

Does the molecular and metabolic profile of human mural granulosa cells (GCs) correlate with oocyte fate?

SUMMARY ANSWER

A close relation between the metabolic profile of mural GCs and the fate of the corresponding oocyte was revealed by the analysis of selected biomarkers defined by GC Fourier transform infrared microspectroscopy (FTIRM) analysis.

WHAT IS KNOWN ALREADY

In ART, oocyte selection is mainly based on the subjective observation of its morphological features; despite recent efforts, the success rate of this practice is still unsatisfactory. FTIRM is a well-established vibrational technique recently applied to evaluate oocytes quality in several experimental models, including human.

STUDY DESIGN, SIZE, DURATION

GCs retrieved from single-follicle aspirates were obtained with informed consent from 55 women undergoing controlled ovarian stimulation for IVF treatment. GCs were analysed by FTIRM to retrospectively correlate their spectral features with the fate of the companion oocytes. The study has been conducted between March 2016 and September 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients were selected according to the following inclusion criteria: age <40 years; non-smokers; no ovarian infertility diagnosis (only tubal, idiopathic and male infertility); regular ovulatory menstrual cycles (25-30 days) with FSH < 10 IU/I on Day 3 of the menstrual cycle; sperm sample with a total motility count after treatment ≥300.000; number of retrieved oocytes ≥8. Based on the clinical outcome of the corresponding oocyte, GCs were retrospectively classified into the following experimental groups: clinical pregnancy (CP), fertilization failure (FF), embryo development failure (EDF) and implantation failure (IF). All samples were analysed by the FTIRM technique. The spectral biomarker signature of different oocyte fates was derived by several feature selection procedures ('Leave-one-out' method on factorial discriminant analysis (FDA), variable characterization method and logistic regression method with the multinomial Logit model). ANOVA, permutational multivariate ANOVA, FDA and canonical analysis of principal co-ordinates statistical tools were also applied to validate the identified spectral biomarkers.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 284 GCs samples were retrieved and retrospectively classified as FF: (N = 92), EDF (N = 113), IF (N = 56) and CP (N = 23). From the spectral profiles of GCs belonging to CP, FF, EDF and IF experimental groups, 17 spectral biomarkers, were identified by several feature selection procedures (P < 0.0001). These biomarkers were then validated by applying multivariate tools, to evaluate their ability to segregate GCs samples into the four experimental groups. FDA showed a clear separation along the F1-axis (62.75% of discrimination) between GCs from oocytes able (CP, IF groups) or not (FF, EDF groups) to develop into embryos; the F2-axis (24.14% of discrimination) segregated the embryos that gave pregnancy (CP) from those that failed implantation (IF). The confusion matrix (total percentage of correctness = 80.25%) obtained from this analysis pinpointed that GCs from oocytes unable to develop into embryos (FF, EDF) were better characterized than those from oocytes able to give viable embryos (CP, IF). ANOVA (P < 0.05) analysis pinpointed that: each experimental group showed specific macromolecular traits, ascribable to different biological and metabolic characteristics of GCs; these metabolic features were likely associated with different oocytes fates, but not to patient characteristics, since from the same patient we obtained GCs with different metabolic profiles.

LIMITATIONS, REASONS FOR CAUTION

The study is based on a small sample size but provides proof of concept that the GCs' metabolic profile is associated with the companion oocyte fate. The generated model should be further tested on a larger cohort of patients, classified in a similar manner, to assess the potential predictive value of this approach. Ultimately, validity of the proposed approach should be tested in a RCT.

WIDER IMPLICATIONS OF THE FINDINGS

For the first time, the FTIRM analysis of human GCs has demonstrated an approach to better understand the molecular crosstalk between follicular cells and oocytes and has identified potential spectral biomarkers for improving human IVF success rate.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by GFI 2014 grant. The authors declare that there is no conflict of interest.

The Risk of Retinopathy of Prematurity in the Infants following Assisted Reproductive Technology: A Meta-Analysis

Currently, the use of assisted reproductive technology (ART) is increasing. Because of the poor prognosis of retinopathy of prematurity (ROP), the association between ART and the ROP has been explored in several studies, but the result was still inconclusive. Conducting a meta-analysis, we evaluated the risk of ROP in relation to the ART. Subgroup analysis as well as groups with different embryo numbers and different ROP stages was further analyzed. The PubMed, Embase, and Cochrane Library databases were searched for studies recording data about both the use of ART and ROP occurrence simultaneously. Odds ratios (ORs) and 95% confidence interval (95%CI) were calculated to analyze the association by using random- or fixed-effect models based on heterogeneity test. In total 15 observational studies containing 10392 ART cases and 39474 spontaneous conception cases were included. Results showed that there was a significant association between the use of ART and ROP occurrence in the offspring (OR = 1.34, 95% CI: 1.05 to 1.73, P = 0.02). With subgroup analysis, we found that the influence actually came from a subgroup of ART, the in vitro fertilization (IVF). Moreover, there was a significant association between ART and ROP in singletons. Though insignificant, the ORs were larger than 1 in the analysis between ART and stage 1 and 2 ROP. But ART showed significant association with stage 3 ROP. Our study preliminarily indicated that the use of IVF was associated with higher risk of ROP occurrence. And ART is more likely to result in severe ROP and ROP in singletons. Further specific, high-quality studies with large sample size are still needed to draw more precise conclusion.

Potential risks to offspring of intrauterine exposure to maternal age-related obstetric complications

Several hypotheses have been proposed to explain the negative effects of delayed motherhood on an offspring's morbidity later in life. However, these hypotheses are not supported by clinical and epidemiological evidence. Because advanced maternal age is associated with increased risk of obstetric complications, the aim of the present study was to ascertain whether the negative effects on offspring of intrauterine exposure to maternal age-related obstetric complications may explain the reported negative effects of delayed motherhood on offspring. To this end, a literature search was performed to identify relevant publications up to March 2016 on PubMed; references cited in relevant articles were also searched. There was a direct correlation between the risks to offspring conferred by intrauterine exposure to at least one of the obstetric complications present at the time of delivery in women aged ≥35 years and the risks to offspring of delayed motherhood. This correlation was not observed when comparing the risks to offspring of delayed motherhood and the risks associated with maternal transmission of defective mitochondria, chromosomal anomalies or DNA double-strand breaks. Most of the effects on offspring of intrauterine exposure to maternal age-related obstetric complications may be induced by epigenetic DNA reprogramming during critical periods of embryo or fetal development. Women wanting to enrol in a fertility preservation program to offset age-related declines in fertility should be informed not only about their chances of pregnancy and the percentage of live births, but also about the risks to themselves and their prospective offspring of delaying motherhood.

Clinical outcomes of frozen embryo versus fresh embryo transfer following in vitro fertilization: a meta-analysis of randomized controlled trials

PURPOSE

To examine available data from randomized controlled trials to assess if the freeze-all embryo and subsequent frozen-thawed embryo transfer (FET) results in better clinical outcomes than fresh embryo transfer (ET).

METHODS

Meta-analysis.

RESULTS

We conducted an electronic literature search on PubMed and Embase databases and manually supplemented another 2 articles from relevant citations. Seven studies were finally included in the meta-analysis,including 1141 women who underwent fresh embryo transfer and 1079 who underwent frozen embryo transfer. The results of the meta-analysis suggested that the live birth rate [RR (95% CI) 1.18 (1.08-1.30), P = 0.0003] and clinical pregnancy rate [RR (95% CI) 1.10 (1.02-1.19), P = 0.02] were significantly higher in FET group. Miscarriage rate [RR (95% CI) 0.62 (0.48-0.80), P = 0.0002], and moderate to severe OHSS occurrence rate [RR (95% CI) 0.22 (0.12 to 0.39), P < 0.00001] were significantly lower in FET group. Differences of biochemical pregnancy rate, ongoing pregnancy rate and implantation rate between the two groups did not reach the statistical significance.

CONCLUSIONS

Our results suggest that the IVF/ICSI with FET is more efficient and less risky for OHSS compared with ET. However, we should comprehensively inform patients with advantages, disadvantages and potential risks related to embryo cryopreservation, and carefully assess their fertility conditions to make the most beneficial clinical decision.

Time to re-evaluate ART protocols in the light of advances in knowledge about methylation and epigenetics: an opinion paper

DNA methylation is a biochemical process that modifies gene expression without changing the underlying DNA sequence, and this represents the molecular basis for imprinting and epigenetics. Recent reports have revealed alterations in DNA methylation profiles in the placenta of babies born from assisted reproductive technologies (ART). This supports several previous observations that suggested an increase in the prevalence of imprinting diseases following ART treatment, and also fits our observations regarding the metabolism and requirements of early human embryos. Human embryo culture media (HECM) are currently formulated according to requirements based on the mouse embryo model, and in fact need to pass the Mouse Embryo Assay test in order to be accepted by the relevant authorities, despite the fact that physiological (especially the time necessary to reach genomic activation) and biochemical requirements of mouse and human embryos are quite different. This commentary aims to explain some of the discrepancies, and emphasize why human embryo metabolism tells us that the composition of HECM, as well as the role of the MEA as a unique model, should be re-evaluated.

A putative role for anti-Müllerian hormone (AMH) in optimising ovarian reserve expenditure

The mammalian ovary has a finite supply of oocytes, which are contained within primordial follicles where they are arrested in a dormant state. The number of primordial follicles in the ovary at puberty is highly variable between females of the same species. Females that enter puberty with a small ovarian reserve are at risk of a shorter reproductive lifespan, as their ovarian reserve is expected to be depleted faster. One of the roles of anti-Müllerian hormone (AMH) is to inhibit primordial follicle activation, which slows the rate at which the ovarian reserve is depleted. A simple interpretation is that the function of AMH is to conserve ovarian reserve. However, the females with the lowest ovarian reserve and the greatest risk of early reserve depletion have the lowest levels of AMH. In contrast, AMH apparently strongly inhibits primordial follicle activation in females with ample ovarian reserve, for reasons that remain unexplained. The rate of primordial follicle activation determines the size of the developing follicle pool, which in turn, determines how many oocytes are available to be selected for ovulation. This review discusses the evidence that AMH regulates the size of the developing follicle pool by altering the rate of primordial follicle activation in a context-dependent manner. The expression patterns of AMH across life are also consistent with changing requirements for primordial follicle activation in the ageing ovary. A potential role of AMH in the fertility of ageing females is proposed herein.

The subcortical maternal complex: multiple functions for one biological structure?

The subcortical maternal complex (SCMC) is a multiprotein complex uniquely expressed in mammalian oocytes and early embryos, essential for zygote progression beyond the first embryonic cell divisions. Similiar to other factors encoded by maternal effect genes, the physiological role of SCMC remains unclear, although recent evidence has provided important molecular insights into different possible functions. Its potential involvement in human fertility is attracting increasing attention; however, the complete story is far from being told. The present mini review provides an overview of recent findings related to the SCMC and discusses its potential physiological role/s with the aim of inspiring new directions for future research.

Deficiencies in reporting results of lesbians and gays after donor intrauterine insemination and assisted reproductive technology treatments: a review of the first emerging studies

At a time when increasing numbers of lesbians and gays consider parenthood using reproductive assistance in infertility centers, the present review aims to summarize the results obtained so far by lesbians after intrauterine insemination (IUI) and in-vitro fertilization (IVF) using donor spermatozoa (D-IUI and D-IVF, respectively) and gays entering into gestational-surrogacy programs. Data show that gays display normal semen parameters and lesbians exhibit no specific causes of female infertility except perhaps for polycystic ovary syndrome (PCOS) and some PCOS-related factors. Pair-bonded lesbians entering into D-IUI programs, tend to have higher pregnancy and delivery percentages following spontaneous or induced ovulation than single or pair-bound heterosexual women. The only single study reporting success percentages of lesbians after D-IVF provides, however, puzzling results. In particular, pair-bonded lesbians have lower pregnancy and live-birth percentages than pair-bonded heterosexual women in fresh D-IVF cycles but percentages are similar in frozen/thawed D-IVF cycles. Like in lesbians after D-IUI, surrogate women recruited by pair-bonded gays/single men tend to have higher pregnancy percentages and lower miscarriage percentages than surrogate women recruited by heterosexual couples. Notably, all the reports reviewed in the present study are methodologically flawed because of sampling bias, small sample sizes and inadequate use of statistical methods to control for the effects of influential covariates including age, smoking habits, previous gynecological problems, hormonal stimulation type and protocol, and number of prior treatment types and pregnancies/deliveries. Clinicians, reproductive biologists and editors of fertility/infertility journals should make efforts to prevent these deficiencies in future data reporting.

Infertility etiologies are genetically and clinically linked with other diseases in single meta-diseases

The present review aims to ascertain whether different infertility etiologies share particular genes and/or molecular pathways with other pathologies and are associated with distinct and particular risks of later-life morbidity and mortality. In order to reach this aim, we use two different sources of information: (1) a public web server named DiseaseConnect ( http://disease-connect.org ) focused on the analysis of common genes and molecular mechanisms shared by diseases by integrating comprehensive omics and literature data; and (2) a literature search directed to find clinical comorbid relationships of infertility etiologies with only those diseases appearing after infertility is manifested. This literature search is performed because DiseaseConnect web server does not discriminate between pathologies emerging before, concomitantly or after infertility is manifested. Data show that different infertility etiologies not only share particular genes and/or molecular pathways with other pathologies but they have distinct clinical relationships with other diseases appearing after infertility is manifested. In particular, (1) testicular and high-grade prostate cancer in male infertility; (2) non-fatal stroke and endometrial cancer, and likely non-fatal coronary heart disease and ovarian cancer in polycystic ovary syndrome; (3) osteoporosis, psychosexual dysfunction, mood disorders and dementia in premature ovarian failure; (4) breast and ovarian cancer in carriers of BRCA1/2 mutations in diminished ovarian reserve; (5) clear cell and endometrioid histologic subtypes of invasive ovarian cancer, and likely low-grade serous invasive ovarian cancer, melanoma and non-Hodgkin lymphoma in endometriosis; and (6) endometrial and ovarian cancer in idiopathic infertility. The present data endorse the principle that the occurrence of a disease (in our case infertility) is non-random in the population and suggest that different infertility etiologies are genetically and clinically linked with other diseases in single meta-diseases. This finding opens new insights for clinicians and reproductive biologists to treat infertility problems using a phenomic approach instead of considering infertility as an isolated and exclusive disease of the reproductive system/hypothalamic-pituitary-gonadal axis. In agreement with a previous validation analysis of the utility of DiseaseConnect web server, the present study does not show a univocal correspondence between common gene expression and clinical comorbid relationship. Further work is needed to untangle the potential genetic, epigenetic and phenotypic relationships that may be present among different infertility etiologies, morbid conditions and physical/cognitive traits.

Different chromatin and energy/redox responses of mouse morulae and blastocysts to slow freezing and vitrification

BACKGROUND

The ability to cryopreserve mammalian embryos has become an integral part of assisted reproduction, both in human and veterinary medicine. Despite differences in the size and physiological characteristics of embryos from various species, the embryos have been frozen by either of two procedures: slow freezing or vitrification. The aim of our study was to compare the effect of slow freezing and vitrification to the chromatin structure, energy status and reactive oxygen species production of mouse morulae and blastocysts.

METHODS

Mouse morulae and blastocysts were randomly allocated into vitrification, slow freezing and control groups. For slow freezing, Dulbecco phosphate buffered saline based 10% glicerol solution was used. For vitrification, G-MOPS™ based solution supplemented with 16% ethylene glycol, 16% propylene glycol, Ficoll (10 mg/ml) and sucrose (0.65 mol/l) was used. After warming, the chromatin integrity, mitochondrial distribution pattern and energy/oxidative status were compared among groups.

RESULTS

Cryopreservation affected chromatin integrity at a greater extent at the morula than the blastocyst stage. Chromatin damage induced by slow freezing was more relevant compared to vitrification. Slow freezing and vitrification similarly affected mitochondrial distribution pattern. Greater damage was observed at the morula stage and it was associated with embryo grade. Cryopreservation altered the quantitative bioenergy/redox parameters at a greater extent in the morulae than in the blastocysts. Effects induced by slow freezing were not related to embryo grade or mitochondrial pattern, as affected embryos were of all grades and with both mitochondrial patterns. However, effects induced by vitrification were related to mitochondrial pattern, as only embryos with homogeneous mitochondrial pattern in small aggregates had reduced energy status.

CONCLUSIONS

This study shows for the first time the joint assessment of chromatin damage and mitochondrial energy/redox potential in fresh and frozen mouse embryos at the morula and blastocyst stage, allowing the comparison of the effects of the two most commonly used cryopreservation procedures.

Trends, fads and ART!

Morphological selection techniques of gametes and embryos are of current interest to clinical practice in ART. Although intracytoplasmic morphologically selected sperm injection (IMSI), time lapse imaging morphometry (TLIM) or quantification of chromosome numbers (PGS) are potentially useful in research, they have not been shown to be of statistically predictive value and, thus, have only limited clinical usefulness. We make the point that morphological markers alone cannot predict the success of the early embryo, which depends on the correct orchestration of a myriad of physiological and biochemical activation events that progress independently of the maternal or zygotic genome. Since previous attempts to identify metabolic markers for embryo quality have failed and there is no evidence that the intrinsic nature of gametes and embryos can be improved in the laboratory, embryologists can only minimize environmental or operator induced damage while these cells are manipulated ex vivo.