Effect of postthaw change in embryo score on single euploid embryo transfer success rates.

OBJECTIVE: To assess whether the change in embryo morphology from precryopreservation to postthaw is associated with the embryo transfer success rates in single euploid embryo transfer cycles. DESIGN: Retrospective cohort study. SETTING: Academic affiliated fertility clinic. PATIENT(S): Patients who underwent a single euploid embryo transfer cycle from September 2016 to April 2022 were included. A decision support tool was used to assign each embryo a reproductive potential score on the basis of the day of biopsy, expansion, and grade of trophectoderm and inner cell mass at the time of cryopreservation and after thaw. Embryos were divided into 4 groups: group 1 included embryos with the same score after thaw (reference); group 2 included those with a higher score; group 3 included those with a lower score; and group 4 included those that did not re-expand after thaw. INTERVENTION(S): No interventions administered. MAIN OUTCOME MEASURE(S): The primary outcome was the live birth rates (LBRs) per embryo transfer. The secondary outcomes included the chemical pregnancy, clinical pregnancy, and clinical pregnancy loss rates. Comparative statistics and univariate analyses were performed using the Kruskal-Wallis and χ2tests. Multivariate logistic regression fitted with generalized estimating equation was performed to compare the odds of live birth between groups. RESULT(S): A total of 7,750 embryo transfers performed for 4,613 patients met inclusion criteria: 5,331 in group 1; 486 in group 2; 1,726 in group 3; and 207 in group 4. In the univariate analysis, there was a statistically significant difference in the LBR between groups 1, 2, 3, and 4 (55.8% vs. 51.4%, 47.5%, and 26.6%). Logistic regression controlling for oocyte age, antimüllerian hormone, body mass index, endometrial thickness, year of embryo transfer, time from thaw to final grading, and embryo score before cryopreservation showed significantly lower odds of live birth when the embryo was downgraded (odds ratio [OR], 0.70; confidence interval [CI], 0.62-0.79) or did not re-expand (OR, 0.36; CI, 0.26-0.51) than those with no change in score. When controlling for all variables, there was a significant increase in the odds of live birth between embryos that had a higher score after thaw and those without a change (OR, 1.42; CI, 1.14-1.76). There was no significant difference in the clinical pregnancy loss rate among the 4 groups. CONCLUSION(S): The change in the quality of the embryo after thaw is an important factor in embryo transfer success. In an adjusted analysis, the chemical and clinical pregnancy rates and LBR per embryo transfer all significantly decrease in embryos that were downgraded or did not expand on the day of single euploid embryo transfer. Embryos that re-expand and have improved quality after thaw have the highest odds of live birth.

External bending of cryodevice during vitrification leads to cryoprotectant cracks and damage to embryo blastomeres.

RESEARCH QUESTION: Embryo blastomeres and the zona pellucida are occasionally damaged during vitrification; is this a result of crack-induced mechanical damage in the glass state, caused by external bending of the device? DESIGN: A stereomicroscope was used to observe external bending-induced cracks in a cryoprotectant. Thereafter, 309 human cleavage-stage embryos derived from abnormally fertilized eggs were used to assess embryo damage under two external bending conditions: forward bending and backward bending, with three bending degrees applied. Three distinct embryo positions were used to examine the correlation between bending and embryo damage. Damage was assessed by looking at blastomere lysis rates, and overall rates of damaged and surviving embryos. RESULTS: A series of parallel cracks were identified in the cryoprotectant used for external bending, which led to damage to the embryo blastomeres. Compared with forward bending and control, the embryos were found to be more easily damaged by backward bending, indicated by significantly higher blastomere lysis and embryo damage rates, and lower embryo survival rate of backward bending than forward bending (P < 0.001). The degree of embryo damage also increased as the degree of external forces increased. Embryo position correlated with degree of embryo damage. CONCLUSIONS: Cryoprotectant crack-induced damage was identified as the cause of embryo damage. Mechanical damage to the glass state occurs because of improper external bending of the cryodevice strip in liquid nitrogen during vitrification. To prevent damage, bending of the strip should be avoided and the embryos should be placed near the tip of the strip.

The adverse effects of vitrification on mouse embryo development and metabolic phenotype in offspring.

Embryo vitrification is a standard procedure in assisted reproductive technology. Previous studies have shown that frozen embryo transfer is associated with an elevated risk of adverse maternal and neonatal outcomes. This study aimed to explore the effects of mouse blastocyst vitrification on the phenotype of vitrified-warmed blastocysts, their intrauterine and postnatal development, and the long-term metabolic health of the derived offspring. The vitrified-warmed blastocysts (IVF + VT group) exhibited reduced mitochondrial activity, increased apoptotic levels, and decreased cell numbers when compared to the fresh blastocysts (IVF group). Implantation rates, live pup rates, and crown-rump length at E18.5 were not different between the two groups. However, there was a significant decrease in fetal weight and fetal/placental weight ratio in the IVF + VT group. Furthermore, the offspring of the IVF + VT group at an age of 36 weeks had reduced whole energy consumption, impaired glucose and lipid metabolism when compared with the IVF group. Notably, RNA-seq results unveiled disturbed hepatic gene expression in the offspring from vitrified-warmed blastocysts. This study revealed the short-term negative impacts of vitrification on embryo and fetal development and the long-term influence on glucose and lipid metabolism that persist from the prenatal stage into adulthood in mice.

Resveratrol Reduces ROS by Increasing GSH in Vitrified Sheep Embryos.

The in vitro production and cryopreservation of mammalian embryos generates reactive oxygen species (ROS) due to conditions of the system that can overcome their antioxidant protection. Resveratrol is an antioxidant used in in vitro systems to improve blastocyst rates, but its effect on antioxidant enzymes such as glutathione (GSH) in embryos produced by in vitro fertilization (IVF) after vitrification has not been reported. The objective of this study was to evaluate the effects of resveratrol on the in vitro maturation medium (IVM) of sheep oocytes (Ovis aries) on the levels of ROS and GSH in embryos produced by IVF subjected to vitrification. Resveratrol was added at 0 µM, 0.25 µM, 0.5 µM, and 1 µM during oocyte in vitro maturation (IVM). Matured oocytes were fertilized with thawed ram sperm. Embryos were cultured in sequential media until blastocysts, were then vitrified for 24 h, and, after heating, they were stained with DCFH-DA (2',7'-dichlorodihydrofluorescein diacetate) to determine the presence of ROS and with Cell Tracker Blue® for the presence of GSH. The quantitative values of ROS and GSH were obtained through the Image J image processor. The results showed that resveratrol increased GSH and decreased ROS production (p < 0.05) in a dose-dependent manner. It is concluded that its use in sheep oocytes during IVM has a beneficial effect on embryos produced by IVF subjected to vitrification by decreasing reactive oxygen species levels and facilitating the generation of embryo antioxidant enzymes like glutathione.

Effect of blastocyst shrinkage on assisted reproductive outcomes: a retrospective cohort study describing a new morphological evaluation of blastocyst pre-vitrification and post-warming.

BACKGROUND: The failure of frozen-thawed blastocysts to re-expand adequately within a few hours after warming has been reported to have a negative impact on assisted reproductive technology (ART) outcomes. However, the extent to which this failure truly affects ART outcomes has not yet been presented in a manner that is easily understandable to medical practitioners and patients. This study aimed to assess the effects of blastocyst shrinkage on ART outcomes and determine a more effective morphological evaluation approach for use in clinical settings. METHODS: This retrospective observational cohort study of frozen-thawed blastocyst transfer cycles was conducted from April 2017 to March 2022. Overall, 1,331 cycles were eligible for inclusion, of which 999 were good-quality blastocysts (GQB) and 332 were non-good-quality blastocysts (non-GQB). All frozen-thawed blastocyst transfer cycles performed during the specified study period were included in the study. Exclusion criteria were established to mitigate potential sources of bias as these cycles could impact implantations. We calculated rates and age-adjusted odds ratios of implantation, clinical pregnancy, ongoing pregnancy, and live birth of the re-expansion group, which showed sufficient expansion, and shrinkage group, which showed insufficient expansion. We also calculated the implantation, clinical pregnancy, ongoing pregnancy, and live birth rates of the re-expansion and shrinkage groups for each morphological scoring system parameter. RESULTS: A reduced ART outcome was observed with use of blastocysts with shrinkage after vitrification/warming. The age-adjusted odds ratios for implantation, clinical pregnancy, ongoing pregnancy, and live birth were lower in the shrinkage group than in the re-expansion group. CONCLUSIONS: This study examined the adverse effect of blastocyst shrinkage after warming and recovery culturing on reproductive outcomes in a clinically useful manner by retrospectively examining a substantial number of frozen-thawed embryo transfer cycles. The study findings can possibly reduce concerns regarding over- or under-estimation of blastocyst implantation by allowing providers and patients to refer to the data.

The international transportation of frozen embryos does not affect IVF outcomes.

PURPOSE: The regulated transportation of cryopreserved human embryos resulting from assisted reproduction treatments offers opportunities for patients undergoing embryo transfer in other regions/countries. However, the principal concern for fertility clinics is maintaining unaltered embryo quality to ensure satisfactory clinical outcomes. The aim of the study was to evaluate the efficacy of the transportation process comparing the survival rate and competence of transported embryos to embryos produced and transferred on-site, in frozen embryo transfer cycles. METHODS: This retrospective study assessed the outcomes of 621 blastocysts thawed at IVI Roma (Italy) between March 2021 and March 2022. Autologous or donated oocytes fertilized in vitro, cultured to the blastocyst stage, and cryopreserved in IVI Roma clinic (Group A, n = 450), were compared to embryos generated in IVI Spain clinics and transported to IVI Roma (Group B, n = 171). RESULTS: Groups A and B respectively showed no significant difference in embryo survival rates after thawing (N = 440/450, 97.8% vs. N = 168/171, 98.2%, p = 0.71), pregnancy rates (N = 221/440, 50.23% vs. N = 77/168, 45.83%, p = 0.33), clinical pregnancy rates (N = 200/440, 45.45% vs. N = 62/168, 36.90%, p = 0.06), and miscarriage rates (N = 42/221, 19,00% vs. 21/77, 28.57%, p = 0.13), even after stratification for the source of the oocyte. Logistic binomial regression considering donor oocytes, preimplantation genetic testing, and patients' age, did not show any significant results on embryo survival and IVF outcomes. CONCLUSION: The regulated transport of cryopreserved blastocysts did not affect embryo survival rate or IVF outcomes. Our data support the safety of embryo cryopreservation and medical transportation services, allowing clinics and patients to transport embryos with no significant risk to embryo competence.

Impact of embryo vitrification on children's health, including growth up to two years of age, in comparison with results following a fresh embryo transfer.

OBJECTIVE: To assess health outcomes, including growth up to 2 years of age, in children born after embryo vitrification in comparison with children born after fresh embryo transfer. DESIGN: A prospective cohort study. SETTING: A single-center university hospital. PATIENT(S): Singletons born after the transfer of vitrified or fresh embryos, either at the cleavage or blastocyst stage between 2014 and 2018, were included. INTERVENTION(S): Multiple linear and logistic regression analyses were used to study the association between outcomes after vitrified versus fresh embryo transfer, controlling for neonatal, treatment, and maternal characteristics. Subgroup analysis according to cycle protocol (hormone replacement vs. natural cycle) and strategy (freeze-all vs. previous fresh cycle) was also performed. MAIN OUTCOME MEASURE(S): Measurements at birth and growth in infancy and childhood, as well as health outcomes, including congenital malformations, interventions, medication use, and hospitalizations are reported. RESULT(S): Birth characteristics were available for 1237 and 2063 children born after embryo vitrification and fresh embryo transfer, respectively. Follow-up data were available for 582 and 757 children at infancy and for 233 and 296 children at 2 years, respectively. Birthweight, height, and head circumference SD scores of children born after embryo vitrification were higher than children born after fresh embryo transfer, even after adjustment for neonatal, treatment, and maternal characteristics. In infancy, weight and height SD scores were larger for children born after embryo vitrification, but not after adjustment for covariates. In childhood, no differences in anthropometry were observed between the groups. Weight and height gain from birth to infancy and from infancy to early childhood were comparable between the groups. Comparable rates of severe developmental problems, hospital admissions, surgical interventions, and of chronic medication use were observed up to the age of 2 years. Subgroup analysis showed that growth parameters were not affected by the cycle protocol or strategy at any age. CONCLUSION(S): Our study indicated that embryo vitrification is associated with higher birthweight, even after controlling for confounders. However, in early childhood, anthropometry and weight and height gain was not different in children born after vitrified or fresh embryo transfer.

Quality assurance (QA) for monitoring the performance of assisted reproductive technology (ART) staff using artificial intelligence (AI).

PURPOSE: Deep learning neural networks have been used to predict the developmental fate and implantation potential of embryos with high accuracy. Such networks have been used as an assistive quality assurance (QA) tool to identify perturbations in the embryo culture environment which may impact clinical outcomes. The present study aimed to evaluate the utility of an AI-QA tool to consistently monitor ART staff performance (MD and embryologist) in embryo transfer (ET), embryo vitrification (EV), embryo warming (EW), and trophectoderm biopsy (TBx). METHODS: Pregnancy outcomes from groups of 20 consecutive elective single day 5 blastocyst transfers were evaluated for the following procedures: MD performed ET (N = 160 transfers), embryologist performed ET (N = 160 transfers), embryologist performed EV (N = 160 vitrification procedures), embryologist performed EW (N = 160 warming procedures), and embryologist performed TBx (N = 120 biopsies). AI-generated implantation probabilities for the same embryo cohorts were estimated, as were mean AI-predicted and actual implantation rates for each provider and compared using Wilcoxon singed-rank test. RESULTS: Actual implantation rates following ET performed by one MD provider: "H" was significantly lower than AI-predicted (20% vs. 61%, p = 0.001). Similar results were observed for one embryologist, "H" (30% vs. 60%, p = 0.011). Embryos thawed by embryologist "H" had lower implantation rates compared to AI prediction (25% vs. 60%, p = 0.004). There were no significant differences between actual and AI-predicted implantation rates for EV, TBx, or for the rest of the clinical staff performing ET or EW. CONCLUSIONS: AI-based QA tools could provide accurate, reproducible, and efficient staff performance monitoring in an ART practice.

Fitness of calves born from in vitro-produced fresh and cryopreserved embryos.

In cattle, vitrified/warmed (V/W) and frozen/thawed (F/T), in vitro-produced (IVP) embryos, differ in their physiology and survival from fresh embryos. In this study, we analyzed the effects of embryo cryopreservation techniques on the offspring. IVP embryos cultured with albumin and with or without 0.1% serum until Day 6, and thereafter in single culture without protein, were transferred to recipients on Day 7 as F/T, V/W, or fresh, resulting in N = 24, 14, and 13 calves, respectively. Calves were clinically examined at birth, and blood was analyzed before and after colostrum intake (Day 0), and subsequently on Day 15 and Day 30. On Day 0, calves from V/W and F/T embryos showed increased creatinine and capillary refill time (CRT) and reduced heartbeats. Calves from F/T embryos showed lower PCO2, hemoglobin, and packed cell volume than calves from V/W embryos while V/W embryos led to calves with increased Na+ levels. Colostrum effects did not differ between calves from fresh and cryopreserved embryos, indicating similar adaptive ability among calves. However, PCO2 did not decrease in calves from V/W embryos after colostrum intake. Serum in culture led to calves with affected (P < 0.05) temperature, CRT, HCO 3 - , base excess (BE), TCO2, creatinine, urea, and anion gap. On Day 15, the effects of embryo cryopreservation disappeared among calves. In contrast, Day 30 values were influenced by diarrhea appearance, mainly in calves from V/W embryos (i.e., lower values of TCO2, HCO 3 - , and BE; and increased glucose, anion gap, and lactate), although with no more clinical compromise than calves from fresh and F/T embryos. Diarrhea affected PCO2 and Na+ in all groups. Embryo cryopreservation, and/or culture, yield metabolically different calves, including effects on protein and acid-base metabolism.

Thermally conductive graphene-based nanofluids, a novel class of cryosolutions for mouse blastocysts vitrification.

Limited heating and cooling rates have long been recognized as bottlenecks in improving embryo cryopreservation. As a result, efforts to achieve higher heat transfer rates gave rise to milestones like open cryodevices and minimal media loading. A crucial but commonly ignored variable is heat conduction by cryosolutions. The low heat conductivity of the aqueous media surrounding embryos slows down cooling and heating rates of the embryo, imposing the risk of preventable damages. In this study, we introduce a novel thermally conductive cryosolution based on graphene oxide nanoparticles and test its performance against conventional sucrose-based solutions for vitrification of mouse blastocysts. Replacing sucrose with graphene oxide brought about similar re-expansion, hatching, and implantation rates of post-vitrification embryos while also preventing an array of cellular and molecular stresses. Our results showed significantly reduced oxidative stress, characterized by control-level expression of Sod1 and significant downregulation of Sod2 transcription when graphene oxide was used instead of sucrose. This molecular response was in agreement with the reduced level of reactive oxygen species produced in vitrified/warmed embryos using graphene-based solutions. The downstream impacts of this stress reduction manifested in significant downregulation of two major pro-apoptotic genes, Bax and Trp53, down to the same level as fresh embryos. Interestingly, embryos maintained their spherical shape during dehydration in graphene-based solutions and did not "collapse" when shrinking, like in sucrose-based solutions. These results provide new insights into the benefits of thermally conductive cryosolutions and showcase the potential of graphene oxide as a cryoprotectant in embryo vitrification.

A comparative study of post-warming survival rates and clinical outcomes of human blastocysts vitrified/warmed by CryoTouch and Cryotop methods.

OBJECTIVE: Advances in embryo culture conditions and the development of vitrification as a revolutionary cryopreservation method have allowed for routine use of blastocyst transfer in assisted reproduction technology (ART) cycles. Several vitrification/warming media and devices have been introduced for commercial use so far. The aim of this retrospective study was to compare post-warming survival rates and clinical outcomes of human blastocysts vitrified/warmed by two different commercial methods (CryoTouch and Cryotop) during ART cycles. METHODS: This retrospective study assessed a total of 50 frozen embryo transfer (FET) cycles conducted on 56 warmed blastocysts between January 2018 and December 2020. Post-warming blastocyst survival rates and clinical outcomes including clinical pregnancy and live birth rates were calculated after single blastocyst transfer cycles. RESULTS: The results revealed no significant differences between two groups in post-warming survival rate (p-value=0.8381), clinical pregnancy rate (p-value=0.8157) and live birth rate (p-value=0.7041). CONCLUSIONS: Post-warming survival rates and clinical outcomes were comparable with no significant difference in blastocysts vitrified/warmed by CryoTouch and Cryotop commercial methods.

The Impact of Embryo Storage Time on Pregnancy and Perinatal Outcomes and the Time Limit of Vitrification: A Retrospective Cohort Study.

Background: The technique of embryo cryopreservation has been increasingly applied in clinical settings. However, there has been a concern about the safety and efficacy of long-term freezing of embryos. Therefore, the aim of this study was to evaluate whether storage time of vitrification had any effects on pregnancy as well as perinatal outcomes, further, to explore the appropriate time limit of vitrification. Methods: The study included women who underwent at least one frozen-thawed cycle with single embryo transfer between January 1st, 2016 and September 30th, 2019. Patients were assigned into 3 groups according to the storage time (<3 months, 3-12 months and >12 months) to evaluate the impact of embryo storage time on pregnancy and perinatal outcomes. To further investigate the time limit of vitrification, propensity score matching was used to compare the primary outcomes of patients with storage time of 1-3 years, 3-5 years, and >5 years to those stored for ≤1 year. Results: A total of 9806 frozen-thawed embryo transfer cycles were included in our study. After adjustment for confounding variables, no significant differences were found in pregnancy outcomes among groups. However, postponement of transfer increased the risks of large for gestational age and placenta previa. In addition, after propensity score matching, 171 cycles with storage time >5 years were matched with those ≤1 year, both the clinical pregnancy rate and live birth rate decreased significantly when the storage time exceeded 5 years. Conclusions: The duration of vitrification did not significantly affect the pregnancy outcomes within 5 years period. However, the clinical pregnancy rate and live birth rate both decreased significantly when the duration of vitrification exceeded 5 years. It is worth noting that the conclusion was drawn from a small sample study after propensity score matching and should be treated with caution. In addition, the cycles were from different time periods, which could have an impact on the results.

Rederivation by Cryopreservation of a Paternal Line of Rabbits Suggests Exhaustion of Selection for Post-Weaning Daily Weight Gain after 37 Generations.

Rabbit selection programmes have mainly been evaluated using unselected or divergently selected populations, or populations rederived from cryopreserved embryos after a reduced number of generations. Nevertheless, unselected and divergent populations do not avoid genetic drift, while rederived animals seem to influence phenotypic traits such as birth and adult weights or prolificacy. The study aimed to evaluate the effect of a long-term selection for post-weaning average daily weight gain (ADG) over 37 generations with two rederived populations. Specifically, two coetaneous populations were derived from vitrified embryos with 18 generational intervals (R19 and R37), reducing or avoiding genetic drift and environmental and cryopreservation effects. After two generations of both rederived populations (R21 vs. R39 generations), all evaluated traits showed some progress as a result of the selection, the response being 0.113 g/day by generation. This response does not seem to affect the estimated Gompertz growth curve parameters in terms of the day, the weight at the inflexion point or the adult weight. Moreover, a sexual dimorphism favouring females was observed in this paternal line. Results demonstrated that the selection programme had improved ADG without variations in adult body weight but, after 37 generations of selection, this trait seems exhausted. Given the reduction in the cumulative reproductive performance and as a consequence in the selection pressure, or possibly/perhaps due to an unexpected effect, rederivation could be the cause of this weak selection response observed from generation 18 onwards.

Long-Term Phenotypic and Proteomic Changes Following Vitrified Embryo Transfer in the Rabbit Model.

Nowadays, assisted reproductive technologies (ARTs) are considered valuable contributors to our past, but a future without their use is inconceivable. However, in recent years, several studies have evidenced a potential impact of ART on long-term development in mammal species. To date, the long-term follow-up data are still limited. So far, studies have mainly focused on in vitro fertilization or in vitro culture, with information from gametes/embryos cryopreservation field being practically missing. Herein, we report an approach to determine whether a vitrified embryo transfer procedure would have long-term consequences on the offspring. Using the rabbit as a model, we compared animals derived from vitrified-transferred embryos versus those naturally conceived, studying the growth performance, plus the weight throughout life, and the internal organs/tissues phenotype. The healthy status was assessed over the hematological and biochemical parameters in peripheral blood. Additionally, a comparative proteomic analysis was conducted in the liver tissue to investigate molecular cues related to vitrified embryo transfer in an adult tissue. After vitrified embryo transfer, birth weight was increased, and the growth performance was diminished in a sex-specific manner. In addition, vitrified-transferred animals showed significantly lower body, liver and heart weights in adulthood. Molecular analyses revealed that vitrified embryo transfer triggers reprogramming of the liver proteome. Functional analysis of the differentially expressed proteins showed changes in relation to oxidative phosphorylation and dysregulations in the zinc and lipid metabolism, which has been reported as possible causes of a disturbed growth pattern. Therefore, we conclude that vitrified embryo transfer is not a neutral procedure, and it incurs long-term effects in the offspring both at phenotypic and molecular levels. These results described a striking example of the developmental plasticity exhibited by the mammalian embryo.

Developmental Plasticity in Response to Embryo Cryopreservation: The Importance of the Vitrification Device in Rabbits.

In this study, we evaluated the effect of embryo vitrification using two different devices on adulthood phenotype in rabbits. In vitro development, prenatal embryo survival, body weight, growth performance, haematological and biochemical peripheral blood analysis, reproductive performance, and lactation performance traits were compared between the experimental groups. They derived from naturally-conceived embryos (NC), fresh-transferred embryos (FT), vitrified-transferred embryos using mini-straw (VTs), or vitrified-transferred embryos using Cryotop (VTc). Straw-vitrified embryos exhibited lower in vitro developmental rates and in vivo survival rates following embryo transfer compared to its Cryotop-vitrified counterparts. Moreover, the VTs group exhibited higher foetal losses than VTc, FT, and NC groups. Independently of the vitrification device, vitrified-transferred (VT) offspring showed a skewed sex ratio in favour of males, and an increased birth bodyweight. In contrast, postnatal daily growth was diminished in all ART (i.e., FT and VT) animals. In adulthood, significant differences in body weight between all groups was founded-all ART progenies weighed less than NC animals and, within ART, VT animals weighed less than FT. For VT groups, weight at adulthood was higher for the VTs group compared with the VTc group. Peripheral blood parameters ranged between common values. Moreover, no differences were found in the fertility rates between experimental groups. Furthermore, similar pregnancy rates, litter sizes, and the number of liveborns were observed, regardless of the experimental group. However, decreased milk yield occurred for VTc and FT animals compared to VTs and NC animals. A similar trend was observed for the milk composition of dry matter and fat. Concordantly, reduced body weight was found for suckling kits in the VTc and FT groups compared to VTs and NC animals. Our findings reveal that developmental changes after the embryo vitrification procedure could be associated with an exhibition of the embryonic developmental plasticity. Moreover, to our best knowledge, this study reports the first evidence demonstrating that the vitrification device used is not a trivial decision, providing valuable information about how the cooling-warming rates during vitrification can be partly responsible of the postnatal phenotypic variations.

Cryobanking and Recovery of Genetically Modified Mice.

Cryobanking of sperm, oocytes, and embryos is a useful means to efficiently maintain mouse colonies without breeding live animals. Cryopreserved cells can be permanently stored in well-managed systems in liquid nitrogen tanks at -196 °C and quickly reanimated for use via in vitro fertilization and/or embryo transfer. Recent improvements of reproductive technology markedly enhanced the efficiency of recovering and producing animals using cryopreserved cells. The establishment of a cryobanking system will increase the performance of animal experiments, meet the principles of 3Rs (replacement, reduction, and refinement), and reduce labour and costs. In this chapter, we described the latest techniques of sperm cryopreservation, in vitro fertilization, and oocyte and two-cell embryo vitrification developed at the Center for Animal Resources and Development (CARD).

Aberrant expression of miR-29a/29b and methylation level of mouse embryos after in vitro fertilization and vitrification at two-cell stage.

Proper epigenetic modifications during preimplantation embryo development are important for a successful pregnancy. We aim to investigate the putative influence of in vitro fertilization (IVF) and vitrification on DNA methylation in mouse preimplantation embryos. The study groups consisted of blastocyst-derived vitrified two-cell embryos, nonvitrified embryos, and a control group of in vivo derived blastocysts. We assessed developmental competence, global DNA methylation, relative expression levels of miR-29a/29b, and their target genes, Dnmt3a/3b. Vitrified embryos had a lower developmental rate as compared with nonvitrified embryos. There was no significant decrease in blastocyst cell numbers among studied groups, whereas there was a steady decline in DNA methylation after IVF and vitrification. The levels of miR-29a/29b upregulated in the experimental groups as compared with the control group. IVF and vitrification caused Dnmt3a/3b downregulations in blastocysts. The results of this study have suggested that a relationship exists between IVF and embryo vitrification with methylation interruptions in the blastocysts.

[Comparison of birth weights of children born after slow frozen embryo replacement versus fresh embryo transfer]. / Embryons vitrifiés, embryons frais : comparaison des poids de naissance.

OBJECTIVE: It is already known that children born after slow frozen embryo replacement have a significantly higher birth weight compared to children born after fresh embryo transfer. Similar data have been reported related to frozen embryo transfer using an open vitrification system. However, few data relative to birth weight using a complete embryo closed vitrification system has been reported. The purpose of this study was to know if frozen embryo in closed vitrification system is associated with a higher birth weight compared to fresh embryo replacement. DESIGN: This was a monocentric retrospective cohort study, 371 children were issued from fresh embryo replacement and 127 from vitrified embryo transfer. MATERIALS AND METHODS: All singletons born after fresh or vitrified embryo transfer between January 2011 and April 2015 were included. Births from the vitrified or fresh transfers of egg or sperm donation, and preimplantation genetic diagnosis were excluded. In addition, pregnancies with more than one gestational sac at the first ultrasound were excluded. An analysis of covariance (ANCOVA) was used for multivariate analysis. RESULTS: Mean birth weight was 205g higher in the frozen embryo compared with fresh embryos transfer groups (3368g vs. 3163g respectively, P<0.001). This difference remained after multivariate analysis adjusted on confounding factors such as gestational age, maternal age, maternal body mass index (BMI), tobacco exposure, number of embryo transferred and birth order (P<0.001).. CONCLUSIONS: Embryo frozen in closed vitrification system is associated with a higher birth weight compared to fresh embryo replacement. Our findings are consistent with the previous studies related to slow freezing and open vitrification systems data. The effects of controlled ovarian stimulation (COS), ex vivo culture conditions and cryopreservation systems on birth weight of children born should be further explored.

Impact of in vitro fertilization by fresh and frozen semen on developmental competence and cryotolerance of buffalo embryos.

Production of high quality embryos in vitro needs an efficient in vitro fertilization (IVF). Seminal origin is one of the important factors that affects the success of in vitro embryo production. So our goal was to determine the effect of using fresh and frozen semen in fertilization on developmental competence and cryo-survival of buffalo embryos. Buffalo oocytes were matured and fertilized in vitro by fresh and frozen semen. After embryos evaluation, good quality morula and blastocysts were vitrified using 0.25 ml straws and the post-warmed viability was assessed by further culture for 24 h. There was no significant difference in cleavage rate between embryos derived from fresh and frozen semen, whereas the rate of embryo development to the morula (P<0.05) and blastocysts (P<0.01) stages was significantly decreased in embryos derived from frozen compared to fresh semen. After warming the vitrified embryos, there was no significant difference between embryos derived from fresh and frozen semen in the percentages of morphologically viable embryos. However, 24 h after culture, the rate of morphologically normal and survived embryos was increased (P<0.05) in embryos derived from fresh compared to the frozen semen. In conclusion, in buffalo, the use of fresh semen could improve the rate of embryo development and their crytolerance compared to the frozen semen.

Neonatal outcomes following fresh as compared to frozen/thawed embryo transfer in in vitro fertilization.

In vitro fertilization (IVF) and embryo cryopreservation have become increasingly common in recent years. As utilization increases, it is important to understand the clinical effects these technologies have on offspring, as well as the mechanisms behind these effects. Many epidemiologic studies have observed that pregnancies following IVF are more likely to be affected by obstetric complications such as pre-eclampsia, preterm birth, and small for gestational age neonates compared with naturally conceived pregnancies. There has been a great deal of research emerging suggesting that these differences are related to the supraphysiologic hormonal environment that results from ovarian superovulation. While pregnancies resulting from frozen embryo transfer are less likely to experience these complications, babies born after frozen transfer are more likely to be large for gestational age. Epigenetic studies point toward differential methylation of genes critical for growth that may be responsible for the increased incidence of larger neonates following transfer of vitrified embryos. Although it does appear that perinatal outcomes are improved by transferring frozen embryos instead of fresh, it would be premature at this time to recommend universal freeze-all protocols in all patients. This article, as part of the "IVF Reviews" special issue of this journal, aims to expound on the issues outlined above.