Variable expressivity of the tumour suppressor protein TRP53 in cryopreserved human blastocysts

Leptin improves the in vitro development of preimplantation rabbit embryos under oxidative stress of cryopreservation

Vitrification is an economically effective method for embryo cryopreservation in human and livestock animals; however, it carries the risk of damage by the exposure to severe oxidative stress. The present study was conducted to evaluate the effect of leptin at different levels on the in vitro development of fresh and vitrified preimplantation embryos in a rabbit model. Normal embryos at morulae stage were randomly cultured for 2 h with 0, 10, 20 or 100 ng/mL of leptin, then were cultured for further 48 h as freshly or after vitrification. Thereafter, developed blastocysts form the best leptin level in fresh and vitrified embryos along with their controls were allocated to analyze the pro-oxidant (malondialdehyde, MDA; nitric oxide, NO), antioxidant (total antioxidant capacity, TAC; superoxide dismutase, SOD; glutathione peroxidase, GPx), apoptotic (Bcl-2 associated X protein, BAX; heat shock 60kD protein member 1, HSP60; tumor necrosis factor alpha, TNFα) and developmental (sex determining region Y box protein 2, SOX2; Nanog homeobox protein, NANOG; Octamer-binding protein 4, OCT4) biomarkers. Results indicate that expanding and hatching rates of embryos were significantly higher at 20 ng/mL leptin than the other levels, while vitrification had an independent suppression effect on the in vitro development rates. The MDA and NO were significantly higher, while TAC, SOD and GPx were significantly lower in the vitrified than fresh embryos. In contrast, leptin treatment significantly decreased the pro-oxidant biomarkers and increased the antioxidant biomarkers in both fresh and vitrified embryos. Vitrification significantly increased the antiapoptotic biomarkers, and decreased the developmental biomarkers in embryos. In contrast, leptin decreased the BAX and TNFα, increased the HSP60, and moreover, ameliorated the reduction of developmental biomarkers in the vitrified embryos. These results conclude that leptin could be used as antiapoptotic and antioxidant promotor to support the in vitro embryonic development, particularly under oxidative stress emerged from cryopreservation programs.

Comparing different sperm separation techniques for ART, through quantitative evaluation of p53 protein

Context:

In the last 10 years, assisted reproductive technologies (ARTs) have offered infertile couples an opportunity to complete their reproductive project. However, the high failure rate could be explained with the complex human reproduction system. In ART, the decrease of the success is due to the conditions far from the natural ones.

Aims:

The aim of this study is to evaluate deoxyribonucleic acid (DNA) damage of spermatozoa before and after selection procedures, using a new technique able to quantize sperm DNA damage.

Settings and Design:

They were involved 43 males domiciled permanently in two areas with different Environmental Impact, HEI (high environmental impact) and LEI (Low environmental impact), they are aged between 24 and 31 years with various degrees of dyspermia.

Subjects and Methods:

The 43 males were divided into two groups: 21 in Group A (EIL) and 22 in Group B (EIH). The samples must be aliquoted into parts of 0.5 mL: Group (a) Control, no processing; Group (b) Swim-up (SUP) from semen; Group (c) classic SUP; Group (d) density gradient centrifugation (DGC). All samples were subjected to a quantitative dosage of p53 protein, before and after processing.

Statistical Analysis Used:

For the development of the probability and significance of the data, the Student's t-test was used.

Results:

From our data, it emerges that Groups D and B provide a superior quality about motility, vitality, and apoptosis indexes compared to other conventional techniques. In Group B, apoptosis is comparable to Group D, but they have slightly lower about motility and vitality. Group C is the one that has lower parameters than the other techniques. Regarding the evaluation of p53 protein, the results are conflicting with the evaluation of apoptosis; in fact, in Group D, the values are significantly higher than the other techniques.

Conclusions:

Sperm separation is an important moment in ART techniques. From our data, it emerges a greater fragility of DNA in the male spermatozoa who reside permanently in areas with high environmental impact.

The role of Trp53 in the mouse embryonic response to DNA damage

Apoptosis occurs primarily in the blastocyst inner cell mass, cells of which go on to form the foetus. Apoptosis is likely to play a role in ensuring the genetic integrity of the foetus, yet little is known about its regulation. In this study, the role of the mouse gene, transformation-related protein 53 (Trp53) in the response of embryos to in vitro culture and environmentally induced DNA damage was investigated using embryos from a Trp53 knockout mouse model. In vivo-derived blastocysts were compared to control embryos X-irradiated at the two-cell stage and cultured to Day 5. An analysis of DNA by comet assay demonstrated that 1.5 Gy X-irradiation directly induced damage in cultured two-cell mouse embryos; this was correlated with retarded development to blastocyst stage and increased apoptosis at the blastocyst stage but not prior to this. Trp53 null embryos developed to blastocysts at a higher frequency and with higher cell numbers than wild-type embryos. Trp53 also mediates apoptosis in conditions of low levels of DNA damage, in vivo or in vitro in the absence of irradiation. However, following DNA damage induced by X-irradiation, apoptosis is induced by Trp53 independent as well as dependent mechanisms. These data suggest that Trp53 and apoptosis play important roles in normal mouse embryonic development both in vitro and in vivo and in response to DNA damage. Therefore, clinical ART practices that alter apoptosis in human embryos and/or select embryos for transfer, which potentially lack a functional Trp53 gene, need to be carefully considered.

p53 Protein Evaluation on Spermatozoa DNA in Fertile and Infertile Males

Introduction and Objectives:

Protein p53 role in the spermatogenesis is demonstrated, it guarantees both the appropriate quality and quantity of mature spermatozoa. In this observational study we evaluate the eventual correlation between “corrected” p53 concentration on human spermatozoa DNA and male fertility potential.

Materials and Methods:

Our work is based on an observational study made of 169 male in a period between March 2012 and February 2017. The entire study group is composed by 208 male partners aged between 26-38 years with ejaculate volume from 0.6 to 5.8 mL and heterogeneous seminal valuation: 86/208 (41,3%) normospermic; 19/208 (9,1%) mild oligospermic; 51/208 (24,5%) moderate oligospermic to; 52/208 (25,1%) with severe oligospermic. The “control” group A includes 39 male partners considered “fertile”, because we did the p53 “corrected” test on their spermatozoa after 28 ± 3,5 days from the positives of their partners pregnancy test (betaHCG> 400 m U/m L). The group B, subdivided in B1, B2 and B3, includes 169 male partners for a observational period of 60 months. This partners don't report previous conceptions, they aren't smokers, don't make use neither of alcohol nor drugs and don't present pathologic varicocele studied with ecoColorDoppler. They are all married or stable cohabitants from a period of 27-39 months and report to have frequent sex without protection with their partners. Determination of p53 procedure: To separate the spermatozoa from seminal fluid we utilized the Differex™ kit System and the DNA IQ™ kit (Promega). For the p53 test we used the direct DuoSet IC kit and quantitative (R&D System). The p53 values were corrected in respect to the spermatozoa concentration expressed in ng/millions of spermatozoa.

Results:

Group A (39 male) presents “correct” p53 values that vary from 0.35 to 3.20 ng/millions of spermatozoa and group B presents values that vary from 0.68 to 14.53. From group B (48 male) in the observational period we have recorded 21 pregnancies with initial “correct” p53 values that vary from a minimum of 0.84 to a maximum of 3.29. In the subgroup B1 we obtained 8 pregnancies from male partners with a “correct” p53 concentration included between 0.84 to 1.34. In the subgroup B2 we obtained 13 pregnancies from male partners with a “correct” p53 concentration included between 1.66 and 3.29. In the subgroup B3 (121 male) there weren't neither pregnancies nor miscarriages and “correct” p53 values were included between 3.58 and 14.53.

Conclusion:

The results show that the member of the group A with values of 'corrected' p53 between 0.35 and 3.20 were considered “Fertile”, although in the observational period 3 miscarriages happened for 3 partners. 36 partners on 39 (92,3%) had a p53 concentration inferior to 1.65, this value were considered as the extreme to identify this group. The member of the group B1 had “corrected” p53 concentration that were included in the group. In the group B2 were observe 13 pregnancies, so its member were considered “potentially fertile” In the group B3 (121 male) weren't observe neither pregnancies nor miscarriages, so its member were considered “potentially infertile”. If further studies confirm these data, we will consider the p53 test ELISA inspected in “correct” p53 as a new and accurate marker of the potential of male fertility.

Global, Survival, and Apoptotic Transcriptome during Mouse and Human Early Embryonic Development

Survival and cell death signals are crucial for mammalian embryo preimplantation development. However, the knowledge on the molecular mechanisms underlying their regulation is still limited. Mouse studies are widely used to understand preimplantation embryo development, but extrapolation of these results to humans is questionable. Therefore, we wanted to analyse the global expression profiles during early mouse and human development with a special focus on genes involved in the regulation of the apoptotic and survival pathways. We used DNA microarray technology to analyse the global gene expression profiles of preimplantation human and mouse embryos (metaphase II oocytes, embryos at the embryonic genome activation stage, and blastocysts). Components of the major apoptotic and survival signalling pathways were expressed during early human and mouse embryonic development; however, most expression profiles were species-specific. Particularly, the expression of genes encoding components and regulators of the apoptotic machinery were extremely stable in mouse embryos at all analysed stages, while it was more stage-specific in human embryos. CASP3, CASP9, and AIF were the only apoptosis-related genes expressed in both species and at all studied stages. Moreover, numerous transcripts related to the apoptotic and survival pathway were reported for the first time such as CASP6 and IL1RAPL1 that were specific to MII oocytes; CASP2, ENDOG, and GFER to blastocysts in human. These findings open new perspectives for the characterization and understanding of the survival and apoptotic signalling pathways that control early human and mouse embryonic development.

The induction of tumour suppressor protein P53 limits the entry of cells into the pluripotent inner cell mass lineage in the mouse embryo

The early preimplantation embryo is susceptible to a range of exogenous stresses which result in their reduced long-term developmental potential. The P53 tumour suppressor protein is normally held at low levels in the preimplantation embryo and we show that culture stress induces the expression of a range of canonical P53-response genes (Mdm2, Bax and Cdkn1a). Culture stress caused a P53-dependent loss of cells from resulting blastocysts, and this was most evident within the inner cell mass population. Culture stress increased the proportion of cells expressing active caspase-3 and undergoing apoptosis, while inhibition of caspase-3 increased the number of cells within the inner cell mass. The P53-dependent loss of cells from the inner cell mass was accompanied by a loss of NANOG-positive epiblast progenitors. Pharmacological activation of P53 by the MDM2 inhibitor, Nutlin-3, also caused increased P53-dependent transcription and the loss of cells from the inner cell mass. This loss of cells could be ameliorated by simultaneous treatment with the P53 inhibitor, Pifithrin-α. Culture stress causes reduced signalling via the phosphatidylinositol-3-kinase signalling pathway, and blocking this pathway caused P53-dependent loss of cells from the inner cell mass. These results point to P53 acting to limit the accumulation and survival of cells within the pluripotent lineage of the blastocyst and provide a molecular framework for the further investigation of the factors determining the effects of stressors on the embryo's developmental potential.

Impacts of and interactions between environmental stress and epigenetic programming during early embryo development

The processes of assisted reproductive technologies (ART) involve a variety of interventions that impact on the oocyte and embryo. Critically, these interventions cause considerable stress and coincide with important imprinting events throughout gametogenesis, fertilisation and early embryonic development. It is now accepted that the IVM and in vitro development of gametes and embryos can perturb the natural course of development to varying degrees of severity. Altered gene expression and, more recently, imprinting disorders relating to ART have become a focused area of research. Although various hypotheses have been put forward, most research has been observational, with little attempt to discover the mechanisms and periods of sensitivity during embryo development that are influenced by the culture conditions following fertilisation. The embryo possesses innate survival factor signalling pathways, yet when an embryo is placed in culture, this signalling in response to in vitro stress becomes critically important in mitigating the effects of stresses caused by the in vitro environment. It is apparent that not all embryos possess this ability to adequately adapt to the stresses experienced in vitro, most probably due to an inadequate oocyte. It is speculated that it is important that embryos use their survival signalling mechanisms to maintain normal epigenetic programming. The seeming redundancy in the function of various survival signalling pathways would support this notion. Any invasion into the natural, highly orchestrated and dynamic process of sexual reproduction could perturb the normal progression of epigenetic programming. Therefore the source of gametes and the subsequent culture conditions of gametes and embryos are critically important and require careful attention. It is the aim of this review to highlight avenues of research to elucidate the effects of stress and the relationship with epigenetic programming. The short- and long-term health and viability of human and animal embryos derived in vitro will also be discussed.

Markers of cellular senescence are elevated in murine blastocysts cultured in vitro: molecular consequences of culture in atmospheric oxygen

PURPOSE

We aimed to determine whether embryo culture induces markers of cellular senescence and whether these effects were dependent on culture conditions.

METHODS

Murine blastocysts were derived in vitro and in vivo and assessed for 2 primary markers of senescence: senescence-associated β-galactosidase (SA-β-gal) and phosphorylated H2A.X (γ-H2A.X), the latter being a mark of DNA oxidative damage. Expression of senescence-associated genes p21, p16, and interleukin 6 (IL6) were also assessed.

RESULTS

Compared with in vivo-derived blastocysts, in vitro embryos had high levels of SA-β-gal, nuclear γ-H2A.X, and p21 mRNA expression, indicating that a senescence-like phenotype is induced by in vitro culture. To determine the role of culture conditions, we studied the effect of oxygen (5 % vs 20 %) and protein supplementation on senescence markers. Blastocysts in reduced oxygen (5 %) had low levels of both SA-β-gal and γ-H2A.X compared with blastocysts cultured in ambient oxygen. Senescence markers also were reduced in the presence of protein, suggesting that antioxidant properties of protein reduce oxidative DNA damage in vitro.

CONCLUSION

Elevated SA-β-gal, γ-H2A.X, and p21 suggest that in vitro stress can induce a senescence-like phenotype. Reduced oxygen during embryo culture minimizes these effects, providing further evidence for potential adverse effects of culturing embryos at ambient oxygen concentrations.

DDX3X regulates cell survival and cell cycle during mouse early embryonic development

DDX3X is a highly conserved DEAD-box RNA helicase that participates in RNA transcription, RNA splicing, and mRNA transport, translation, and nucleo-cytoplasmic transport. It is highly expressed in metaphase II (MII) oocytes and is the predominant DDX3 variant in the ovary and embryo. However, whether it is important in mouse early embryo development remains unknown. In this study, we investigated the function of DDX3X in early embryogenesis by cytoplasmic microinjection with its siRNA in zygotes or single blastomeres of 2-cell embryos. Our results showed that knockdown of Ddx3x in zygote cytoplasm led to dramatically diminished blastocyst formation, reduced cell numbers, and an increase in the number of apoptotic cells in blastocysts. Meanwhile, there was an accumulation of p53 in RNAi blastocysts. In addition, the ratio of cell cycle arrest during 2-cell to 4-cell transition increased following microinjection of Ddx3x siRNA into single blastomeres of 2-cell embryos compared with control. These results suggest that Ddx3x is an essential gene associated with cell survival and cell cycle control in mouse early embryos, and thus plays key roles in normal embryo development.

Global gene expression profiling of individual human oocytes and embryos demonstrates heterogeneity in early development

Early development in humans is characterised by low and variable embryonic viability, reflected in low fecundity and high rates of miscarriage, relative to other mammals. Data from assisted reproduction programmes provides additional evidence that this is largely mediated at the level of embryonic competence and is highly heterogeneous among embryos. Understanding the basis of this heterogeneity has important implications in a number of areas including: the regulation of early human development, disorders of pregnancy, assisted reproduction programmes, the long term health of children which may be programmed in early development, and the molecular basis of pluripotency in human stem cell populations. We have therefore investigated global gene expression profiles using polyAPCR amplification and microarray technology applied to individual human oocytes and 4-cell and blastocyst stage embryos. In order to explore the basis of any variability in detail, each developmental stage is replicated in triplicate. Our data show that although transcript profiles are highly stage-specific, within each stage they are relatively variable. We describe expression of a number of gene families and pathways including apoptosis, cell cycle and amino acid metabolism, which are variably expressed and may be reflective of embryonic developmental competence. Overall, our data suggest that heterogeneity in human embryo developmental competence is reflected in global transcript profiles, and that the vast majority of existing human embryo gene expression data based on pooled oocytes and embryos need to be reinterpreted.

Pro-apoptotic Effect of Pifithrin-α on Preimplantation Porcine In vitro Fertilized Embryo Development

The aim of this study was to investigate the impact of a reported p53 inhibitor, pifithrin-α (PFT-α), on preimplantation porcine in vitro fertilized (IVF) embryo development in culture. Treatment of PFT-α was administered at both early (0 to 48 hpi), and later stages (48 to 168 hpi) of preimplantation development, and its impact upon the expression of five genes related to apoptosis (p53, bak, bcl-xL, p66Shc and caspase3), was assessed in resulting d 7 blastocysts, using real-time quantitative PCR. Total cell numbers, along with the number of apoptotic nuclei, as detected by the in situ cell death detection assay, were also calculated on d 7 in treated and non-treated control embryos. The results indicate that PFT-α, when administered at both early and later stages of porcine IVF embryo development, increases the incidence of apoptosis in resulting blastocysts. When administered at early cleavage stages, PFT-α treatment was shown to reduce the developmental competence of porcine IVF embryos, as well as reducing the quality of resulting blastocysts in terms of overall cell numbers. In contrast, at later stages, PFT-α administration resulted in marginally increased blastocyst development rates amongst treated embryos, but did not affect cell numbers. However, PFT-α treatment induced apoptosis and apoptotic related gene expression, in all treated embryos, irrespective of the timing of treatment. Our results indicate that PFT-α may severely compromise the developmental potential of porcine IVF embryos, and is a potent apoptotic agent when placed into porcine embryo culture media. Thus, caution should be exercised when using PFT-α as a specific inhibitor of p53 mediated apoptosis, in the context of porcine IVF embryo culture systems.

Comparison of gene expression in fresh and frozen–thawed human preimplantation embryos

Identification and characterisation of differentially regulated genes in preimplantation human embryonic development are required to improve embryo quality and pregnancy rates in IVF. In this study, we examined expression of a number of genes known to be critical for early development and compared expression profiles in individual preimplantation human embryos to establish any differences in gene expression in fresh compared to frozen–thawed embryos used routinely in IVF. We analysed expression of 19 genes by cDNA amplification followed by quantitative real-time PCR in a panel of 44 fresh and frozen–thawed human preimplantation embryos. Fresh embryos were obtained from surplus early cleavage stage embryos and frozen–thawed embryos from cryopreserved 2PN embryos. Our aim was to determine differences in gene expression between fresh and frozen–thawed human embryos, but we also identified differences in developmental expression patterns for particular genes. We show that overall gene expression among embryos of the same stage is highly variable and our results indicate that expression levels between groups did differ and differences in expression of individual genes was detected. Our results show that gene expression from frozen–thawed embryos is more consistent when compared with fresh, suggesting that cryopreserved embryos may represent a reliable source for studying the molecular events underpinning early human embryo development.

The effect of Trp53 gene-dosage and parent-of-origin of inheritance on mouse gamete and embryo function in vitro

The transformation-related protein 53 (TRP53) has a canonical role as the "guardian of the genome," serving to protect against the propagation of cells with genomic damage. Autocrine trophic signals act to block the accumulation of TRP53 in the normal preimplantation embryo. Culture of the early embryo at limiting dilutions in simple defined media limits autocrine signaling, resulting in the accumulation of TRP53. This TRP53 reduces the rate of development of embryos. In this study we show that deletion of the Trp53 gene improved development in vitro in a dose-dependent manner. Development to morphological blastocysts increased as the dose of Trp53 was reduced, and this was accompanied by a Trp53-dependent increase in the allocation of cells to the inner cell mass. The intermediate developmental response of heterozygous mice provides evidence for haploinsufficiency of this trait. This haploinsufficiency was evident irrespective of the parent-of-origin of the null allele; however, zygotes with paternal inheritance of the Trp53-null allele had better development in vitro than those with maternal inheritance. There was a beneficial effect of the Trp53-null allele on the number of oocytes released by Trp53(+/-) females, and heterozygous males produced higher fertilization rates than controls, although this was independent of the genotype of the fertilizing sperm. The study shows that ovulation induction or culture of embryos in limiting conditions creates conditions that favor the early development of embryos inheriting loss of Trp53 function. This occurs even in the heterozygous state, showing that the conditions provide a potential basis for accelerated accumulation of deleterious mutations within a population.

Survival signaling in the preimplantation embryo

The autopoietic development of the preimplantation embryo may in part be explained by the actions of autocrine tropic ligands. The net effect of these mediators is to support the survival of cells within the early embryo. In the mouse, the actions of autocrine ligands are required by the 2-cell stage of development, and they can act in concert with paracrine mediators present within the reproductive tract. These mediators act via 1-o-phosphatidylinositol-3-kinase signaling which has the dual effects of activating calcium/calmodulin-dependent kinase/CREB transcription factor and AKT (protein kinase B)/MDM2 mediated survival pathways. The activated CREB drives transcription of prosurvival effectors, including the proto-oncogenes c-Fos and Bcl2. The AKT induces the phosphorylation and activation of MDM2 which causes the ubiquitination and resultant degradation of P53 resulting in the latency of P53 action. Tropic signals provide coordinated mechanisms for maintaining the survival of the cells of the early embryo. Disturbance of survival signaling has the net effect of reducing the number of cells populating the early embryo, due in part to the P53-mediated reduction in the pluripotent inner cell mass stem cell population within the embryo. The resultant embryos have a markedly reduced capacity for development beyond the implantation stage and those that do implant tend to be anembryonic.

Transformation-related protein 53 expression in the early mouse embryo compromises preimplantation embryonic development by preventing the formation of a proliferating inner cell mass

The developmental viability of the preimplantation embryo requires the successful formation of a cluster of pluripotent stem cells called the inner cell mass. Development is variably compromised by a range of exogenous stressors (including their production by assisted reproductive technologies). Inbred C57BL/6 strain embryos are particularly susceptible to the stresses associated with embryo culture, whereas hybrid embryos are more resistant, and this is accounted for in part by the overexpression of transformation-related protein 53 in cultured inbred embryos compared with similarly treated hybrid embryos or embryos not subjected to culture. We show here that this loss of viability is a consequence of the Trp53-dependent reduction in the capacity of blastocysts to form a proliferating inner cell mass. Formation of the trophectodermal line was not adversely affected by these stresses.

Preimplantation embryo development in the mouse requires the latency of TRP53 expression, which is induced by a ligand-activated PI3 kinase/AKT/MDM2-mediated signaling pathway

A universal response to cellular stress is the expression of transformation-related protein 53 (TRP53). This transcription factor reduces cell proliferation and/or survival and is classed as a tumour suppressor protein. Several stresses (including culture) cause increased TRP53 expression in blastocysts and their reduced long-term developmental potential. This study shows that culture from the zygote stage (but not the 2-cell stage) reduced the development of C57BL6 inbred (but not hybrid) strain mouse embryos. Reduced viability was TRP53 dependent, being partially reversed by a TRP53 inhibitor (Pifithrin-alpha). However, the presence of culture did not cause an increase in Trp53 mRNA levels (levels were reduced following culture, P < 0.001). Transformed mouse 3T3 cell double minute 2 (MDM2) causes the ubiquitination and degradation of TRP53. MDM2 activation is accompanied by phosphorylation of Ser-166, and this is commonly catalyzed by the phosphatidylinositol-3 kinase and RAC-alpha serine/threonine-protein kinase (AKT) signaling pathway. Paf is an autocrine embryotrophin that activates the phosphatidylinositol-3 kinase/AKT pathway. High levels of TRP53 expression occurred following the culture of zygotes lacking the Paf receptor (Ptafr(-/-)) and following inhibition of phosphatidylinositol-3 kinase or AKT. Inhibition of MDM2 caused a Trp53-dependent reduction in zygote development. Inbred strain embryos cultured from the zygote stage expressed less phosphorylated MDM2 than similar embryos collected from the uterus. The addition of Paf to the media caused increased phosphorylation of MDM2, and this was blocked by inhibitors of phosphatidylinositol-3 kinase and AKT. The study identifies trophic ligand signaling via the activation of phosphatidylinositol-3 kinase and AKT as a mechanism resulting in the activation of MDM2.