Three years of routine vitrification of human zygotes: is it still fair to advocate slow-rate freezing?

Comparing the effects of vitrification, before and after mouse oocyte in vitro maturation on developmental competence, changes in epigenetic regulators and stress oxidative response

Since the developmental stage of oocyte is a challenging issue in the success of vitrification, this study investigated the effects of vitrification, before and after in vitro maturation, on the survival and maturation rates, developmental competence and the expression levels of genes involved in apoptosis, oxidative stress and epigenetic modifications. Mouse germinal vesicle (GV) oocytes were divided into four groups: fresh in vitro matured oocytes without vitrification (fIVM), in vitro matured oocytes after vitrification (vIVM), in vitro matured oocytes before vitrification (IVMv). In addition, in vivo matured oocytes (MII) were used as control. After oocytes collection, maturation and survival rates as well as the intracellular reactive oxygen species (ROS) level were evaluated. Also, the expression level of various genes was analyzed by qRT-PCR. In addition, following artificial activation (parthenogenesis), the developmental competence of oocytes to the blastocyst stage was evaluated. A significant decrease in maturation rate and survival of vIVM oocytes was observed compared to fIVM and IVMv oocytes. Intracellular ROS levels were significantly increased in both vitrified groups compared to the fIVM group, and no significant difference between vitrified groups. Pro-apoptotic genes; BAX and Bcl2 as well as genes related to oxidative stress response Hsp1a, Hsp1b and SOD1were significantly increased in the vIVM group compared to the IVMv group. Interestingly, epigenetic regulators genes DNMT1, DNMT3a and DNMT3b were highly expressed in IVMv oocytes along with a decrease in the artificial activation rate compared to the vIVM oocytes. Our results indicated that despite observing more negative effects of vitrification before IVM on the survival rate and maturation as well as apoptosis status, less epigenetic changes in vIVM oocytes can make this process a better option in the treatment of infertility than IVM of oocytes followed by vitrification, a hypothesis that needs to be investigation in human oocytes.

Impact of Ovarian Factor Mediums on the Apoptotic Gene Expression and Embryo Quality Derived From Vitrified Immature Human Oocytes

Background

Condition mediums have a potential role in oocyte development. In this study, we evaluated the effects of different mediums on the developmental potential of vitrified immature human oocyte after IVM and parthenogenesis by ionomycin.

Methods

Immature oocytes were collected from 184 women after vitrification/thawing and maturation, in three types of IVM mediums separately. Finally, 151 IVM MΙΙ oocytes were obtained and randomly divided into six groups and underwent the following intervention. Fresh and vitrified-thawing MΙΙ oocytes were activated after IVM in three conditioned mediums by ionomycin. Mediums included 1) Minimum Essential Medium Alpha (α-MEM) (as control medium), 2) α-MEM supplemented with supernatants of Mesenchyme bone marrow (B.M), 3) α-MEM with ovarian growth factors (O.F). Then, scoring of parthenote embryos was undertaken in accordance with pertinent morphological properties. Moreover, the expression of Bax and Bcl2 were determined in the parthenote embryos.

Result

Percentage of the degenerated oocyte, 2-4 cells, 4-8 cells, and 16 cells, was different in the experimental groups. Also, cytoplasmic maturation and blastocyst formation rates were significantly different (p < 0.05) between the control and the other mediums. The highest mRNA expression levels of Bcl2 and Bax genes in parthenotes were observed in the fIVM O.F and vIVM α-MEM mediums, respectively. vIVM, α-MEM and fIVM O.F showed the lowest expression of Bcl2 and Bax genes, respectively.

Conclusion

Our findings indicate that the O.F. medium had more potent effects on oocyte growth and cytoplasmic maturation up to the blastocyst stage with the highest expression level of the BCL2 gene and the lowest relative amount of the BAX gene in this medium. The results of the present study have been verified only for parthenogenetically activated embryos, and any positive effect of the environment on the egg/embryo fertilized with sperm requires more extensive studies.

Prolong cryopreservation duration negatively affects pregnancy outcomes of vitrified-warmed blastocyst transfers using an open-device system: A retrospective cohort study

OBJECTIVE

To investigate the impact of cryopreservation (CP) duration on pregnancy outcomes of vitrified-warmed blastocysts transfers using an open-device liquid-nitrogen (LN₂) system.

METHODS

This retrospective cohort study was conducted on 6327 first vitrified-warmed single blastocyst transfer cycles with autologous oocytes from January 2015 to December 2020. The CP duration was initially divided into six groups: Group I: 0-3 months (n = 4309); Group II: 4-6 months (n = 1061); Group III: 7-12 months (n = 304); Group IV: 13-24 months (n = 113); Group V: 25-72 months (n = 466); Group VI: 73-120 months (n = 74). Multivariate logistic regression was performed to evaluate the independent effect of CP duration on pregnancy outcomes. To further examine the time limit of vitrification, propensity score matching (PSM) was applied to compare pregnancy outcome of patients with storage duration of 25-120 months to those of 0-24 months. After that, pregnancy outcomes were compared among the subgroups of Group I': 0-24 months, Group II': 25-48 months, Group III': 49-72 months, Group IV': 73-120 months. Stratification analysis based on embryo quality was also performed. Primary outcomes were clinical pregnancy rate and live birth rate. Secondary outcomes were implantation, biochemical pregnancy rate, ongoing pregnancy rate and early miscarriage rate.

RESULTS

Logistic regression demonstrated that the odds of pregnancy outcomes were similar across Group I to IV. However, the implantation rate, chances of biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth significantly decreased as the storage duration increased up to 25 months, while miscarriage rate did not significantly differ between groups. Subgroup analysis confirmed a dramatical decrease of clinical pregnancy and live birth rate when cryopreserved for more than 24 months. After that, the slope was relatively steady between 25 and 72 months, then steeply decreased again as CP reached 73-120 months. In addition, there was a more remarkable decline of pregnancy outcomes in the average quality embryo transfers than in the high quality embryo transfers as cryopreservation storage increased.

CONCLUSION

Prolonged cryopreservation of vitrified blastocysts in an open-device LN₂ system up to 24 months might negatively affect pregnancy outcomes. This negative impact progresses as storage duration increases, especially when exceeds 72 months. Average quality embryo appears to be less sustainable with long-term cryo-storage.

The impact of zygote vitrification timing on pregnancy rate in frozen-thawed IVF/ICSI cycles

Introduction: Cryopreservation of bipronuclear (2PN) stage zygotes is an integral part of IVF laboratory practice in countries with strict embryo culture legislation. Vitrification of zygotes is compatible with several strategies in infertility treatments holding a freeze-all indication and allows for effective workload management in settings with limited resources. Although it yields high survival rates and clinical outcomes, the ideal timing to commence vitrification of zygotes is elusive while it is empirically practiced in the window between 17 and 21 h post-insemination (hpi). We aimed to deduce the association between pregnancy rate and the time interval from insemination (IVF and ICSI) to vitrification to contribute to the standardization ofzygote cryopreservation. Methods: A retrospective analysis of data on vitrification timings and pregnancy outcomes collected between 2011 and 2019 was performed. All included women received an embryo transfer after warming of vitrified zygotes at the 2PN stage. Results: A total of 468 embryo transfers were included of which 182 (38.9%) resulted in pregnancy and 286 (61.1%) not. Vitrification was on average performed 18.74 ±0.63 hpi in the pregnant group and 18.62 ± 0.64 hpi in the non-pregnant group (OR 1.36, 95% CI 1.01; 1.83, p = 0.045). A multivariate analysis controlling for uterine pathologies, maternal age, AMH, the number of MII oocytes, previous history of pregnancy success, endometriosis, AFC, nicotine intake and male factor infertility showed no predictive value of vitrification timing on pregnancy rate. Three time intervals between insemination and vitrification were defined: 17:00 to 18:00 hpi (Group A), 18:01 to 19:00 hpi (Group B) and 19:01 to 21:00 hpi (Group C). Pregnancy occurred in 40/130 women (30.80%) in Group A, in 115/281 women (40.90%) in Group B and in 27/57 women (47.40%) in Group C. Univariate but not multivariate analysis showed a significantly higher pregnancy rate after the latest time interval between insemination and 2PN vitrification when compared to the earliest (Group C vs. A, OR 2.03, 95% CI 1.07; 3.84, p = 0.031). Discussion: These findings encourage further investigation on the impact of vitrification timing on clinical outcomes and hold the potential to standardize cryopreservation of zygotes from IVF/ICSI cycles to eventually improve the quality of long-term ART outcomes.

Fertility preservation practices for female oncofertility differ significantly across the USA: results of a survey of SREI members

PURPOSE

The field of oncofertility has maintained an important focus on improving access, yet standardized practices are lacking. To assess how female cancer patients are provided oncofertility care, we sought to determine provider-level differences and whether there are physician or practice characteristics that predict these variations.

METHODS

A cross-sectional survey was sent to SREI members. The survey included fifteen questions about physician practice characteristics and oncofertility cryopreservation protocols. Topics included ovarian stimulation protocols, fertilization techniques, stage of embryo cryopreservation, routine use of pre-implantation genetic testing for aneuploidy (PGT-A), and ovarian tissue cryopreservation (OTC). Statistical analyses assessed whether practice setting, geographic region, time in practice, and mandatory state insurance coverage had effects on cryopreservation protocols.

RESULTS

A total of 141 (17%) from diverse REI practice backgrounds completed the survey. The median number of new female oncofertility consults per year was 30 (range 1 to 300). Providers in academic settings treated more patients (median 40 vs. 15, p < 0.001). Providers in academic settings more often use gonadotropin-releasing hormone agonists (85% vs. 52%, p < 0.001) and perform OTC (41% vs. 4%, p < 0.001). Providers in academic practices were less likely to perform intracytoplasmic sperm injection in every cycle (37% vs. 55%, p = 0.032) and less likely to usually advise PGT-A (21% vs. 36%, p = 0.001). Mandated state insurance coverage had no effect on oncofertility practices.

CONCLUSION

Oncofertility practices vary among providers. Factors such as practice setting and region may affect the services provided. We do not yet know the best practices in oncofertility patients, and future research is needed.

Effects of melatonin and human follicular fluid supplementation of in vitro maturation medium on mouse vitrified germinal vesicle oocytes: A laboratory study

Background

Vitrification as the most efficient method of cryopreservation, enables successful storage of oocytes for couples who undergo specific procedures including surgery and chemotherapy. However, the efficacy of in vitro maturation (IVM) methods with vitrified germinal vesicle (GV) oocytes could be improved.

Objective

As melatonin and follicular fluid (FF) might enhance IVM conditions, we used these supplements to assess the maturation rate of vitrified GV oocytes and their artificial fertilization rate.

Materials and Methods

Four hundred mouse GV oocytes were harvested, vitrified, and assigned into control (C-Vit-GV) and treatment groups of melatonin (M-Vit-GV), human follicular fluid (HFF-Vit-GV), and a combination (M + HFF-Vit-GV). A non-vitrified group of GV oocytes (non-Vit-GV) and a group of in vivo matured metaphase II (Vivo-MII) oocytes served as control groups to evaluate the vitrification and IVM conditions, respectively. Maturation of GV oocytes to MII and further development to two-cell-stage embryos were determined in the different groups.

Results

Development to two-cell embryos was comparable between the Vivo-MII and non-Vit-GV groups. IVM and in vitro fertilization (IVF) results in the non-Vit-GV group were also comparable with the C-Vit-GV oocytes. In addition, the IVM and IVF outcomes were similar across the different treatment groups including the M-Vit-GV, HFF-Vit-GV, M + HFF-Vit-GV, and C-Vit-GV oocytes.

Conclusion

Employing an appropriate technique of vitrification followed by suitable IVM conditions can lead to reasonable IVF outcomes which may not benefit from extra supplementations. However, whether utilizing other supplementation formulas could improve the outcome requires further investigation.

Regenerative Medicine Approaches in Bioengineering Female Reproductive Tissues

Diseases, disorders, and dysfunctions of the female reproductive tract tissues can result in either infertility and/or hormonal imbalance. Current treatment options are limited and often do not result in tissue function restoration, requiring alternative therapeutic approaches. Regenerative medicine offers potential new therapies through the bioengineering of female reproductive tissues. This review focuses on some of the current technologies that could address the restoration of functional female reproductive tissues, including the use of stem cells, biomaterial scaffolds, bio-printing, and bio-fabrication of tissues or organoids. The use of these approaches could also be used to address issues in infertility. Strategies such as cell-based hormone replacement therapy could provide a more natural means of restoring normal ovarian physiology. Engineering of reproductive tissues and organs could serve as a powerful tool for correcting developmental anomalies. Organ-on-a-chip technologies could be used to perform drug screening for personalized medicine approaches and scientific investigations of the complex physiological interactions between the female reproductive tissues and other organ systems. While some of these technologies have already been developed, others have not been translated for clinical application. The continuous evolution of biomaterials and techniques, advances in bioprinting, along with emerging ideas for new approaches, shows a promising future for treating female reproductive tract-related disorders and dysfunctions.

Ceratonia siliqua (Carob) extract improved in vitro development of vitrified-warmed mouse germinal vesicle oocytes: assessment of possible mechanism

Oocyte banking is a vital step for safekeeping and spreading genetic resources of animals. It is also used for fertility preservation of human. Oocyte vitrification is closely related to the lower developmental competence which includes the cryo-injury arisen during vitrification. The aim of the present study was to evaluate the maturation, embryonic development and production of reactive oxygen species (ROS) of mice oocytes following the supplementation vitrification media with different concentrations of Ceratonia siliqua (carob) extracts. In this experimental study, germinal vesicle oocytes collected from 8 to 10 week-old female NMRI mice (30-40 gr) were randomly divided into six groups of vitrification media supplemented with 0 (control), 5, 10, 20, 30 and 50 µg/ml C. siliqua. After thawing, oocytes were put in an in vitro maturation medium (IVM) (α-MEM: Alpha Minimum Essential Medium). 3-4 and 24 h (hr) later, the oocyte nuclear maturity was checked. Standard in vitro fertilization was performed on the matured oocytes (MII), and embryonic development was followed. Extra- and intra-cellular ROS was measured in IVM medium after 24 h of oocyte incubation. The addition of 20 and 30 μg/ml C. siliqua extract to vitrification media improved normal morphology of warmed germinal vesicle (GV) oocytes, rate of germinal vesicle break down (GVBD), and metaphase 2 (MII) oocyte formation significantly (p < 0.05). Fertilization rate, (embryonic development to 2 cells stage, 4-8 cells stage, and > 8 cells stage increased in the 30 μg/ml C. siliqua group significantly (p < 0.05). Furthermore, supplementation of 30 μg/ml C. siliqua in vitrification media significantly decreased extra- and intra-cellular of ROS as well as embryonic fragmentation (p < 0.05). In conclusion, supplementation of GV oocyte vitrification media with carob extract improved maturation, fertilization, and embryonic development rate and decreased extra- and intra-cellular ROS levels.

Investigation of transfer results of human embryos that were vitrified and thawed at the cleavage, morula and blastocyst stages

The objective of this study was to compare the rates of clinical pregnancy after the transfer of vitrified and thawed human embryos on days 3, 4 and 5 of embryonic development. In this retrospective study, the results of 148 embryo transfer cycles, using embryos frozen and thawed over the 3-year period between January 2016 and December 2018 at the Gülhane Training and Research Hospital Department of Gynecology and Obsterics Reproductive Medical Center of the University of Health Sciences, Ankara, Turkey were examined. Following embryo transfer – including 29 dissolved embryos frozen on day 3, 80 frozen on day 4, and 39 frozen on day 5 – results were examined in terms of clinical pregnancy rates. In this study, across all three groups, no significant differences were observed in terms of patient age, the number of oocytes collected, infertility reasons, the number of embryos dissolved, transfer day, or the number of embryos transferred. According to the transfer day, the rates of clinical pregnancy and ongoing pregnancy were significantly higher for embryos frozen on day 4 and transferred on day 5. Significantly higher rates of pregnancy and live birth were determined during in vitro fertilization (IVF) treatment with the freezing of human embryos on day 4 and the transfer of those embryos on day 5.

Growth differentiation factor 9 and cumulus cell supplementation in in vitro maturation culture media enhances the viability of human blastocysts

Objective

In vitro maturation (IVM) of immature oocytes can be useful for some infertile patients. In IVM programs, the rates of embryo formation and pregnancy are low. Therefore, it is essential to recognize the main factors involved in regulating oocyte maturation in vitro. The purpose of this study was to investigate the effects of growth differentiation factor 9 (GDF9) and cumulus cell (CC) supplementation in IVM medium on the rates of embryo formation and viability of human blastocysts.

Methods

A total of 80 germinal vesicle oocytes from stimulated cycles underwent an IVM program. The oocytes were divided into four groups, where group I consisted of IVM media only and served as the control, group II consisted of IVM+CCs, group III consisted of IVM+GDF9 (200 ng/mL), and group IV consisted of IVM+CCs+GDF9 (200 ng/mL). Intracytoplasmic sperm injection was performed on the IVM oocytes, and the cleavage embryos that were generated were vitrified. Following thawing, the embryos were cultured for 3 additional days, and the viability rates of the developed blastocysts were determined.

Results

The maturation rate of the oocytes did not differ significantly across the four groups. The fertilization rate in group II was significantly higher than that in the control group (76.5% vs. 46.2%). Embryo formation was significantly more frequent in all experimental groups than in the control group, while blastocyst formation did not show significant differences in the three experimental groups compared to the control. The mean viability rates in groups II, III, and IV were 58.16%, 55.91%, and 55.95%, respectively, versus 37.78% in the control group (p<0.05).

Conclusion

Supplementation of IVM culture media with GDF9 and CCs enhanced the fertilization, embryo formation, and viability rates of blastocysts generated from vitrified cleavage embryos.

Human cumulus cell sensitivity to vitrification, an ultrastructural study

SummaryCumulus cells (CCs) play an important role in the regulation of female gamete development, meiotic maturation, oocyte-sperm interaction, capacitation and acrosome reaction. However, their role in maintaining oocyte competence after vitrification is unclear as controversial data on their protecting action against oocyte cryoinjuries are available. Here we described the effects of vitrification on the ultrastructure of human CCs collected from women undergoing assisted reproductive technologies (ARTs). In total, 50 patches of CCs, sampled from high-quality human cumulus-oocyte complexes, were randomly allocated into two groups after patient informed consent: 1, fresh CCs (controls, n = 25); 2, vitrified CCs (n = 25). Samples were then prepared and observed by transmission electron microscopy. In fresh CCs, in which small cell clusters were visible, cell membranes were joined by focal gap junctions. Microvilli were rare and short. Nuclei, mitochondria, smooth endoplasmic reticulum (SER), Golgi apparatus and lipid droplets appeared well preserved; vacuoles were scarce. After vitrification, we observed two populations of CCs: light CCs, with a smooth appearance and few short microvilli; and dark CCs, with numerous and long microvilli. In both, most of the organelles appeared similar to those of fresh CCs. Lipid droplets were denser and more numerous, with respect to fresh CCs. They were mainly located in the peri-nuclear and sub-plasmalemmal regions. Numerous packed electron-negative vacuoles were visible. The vitrification procedure did not cause alterations in the fine structure of major organelles, except for an increased amount of lipid droplets and vacuoles. This specific sensitivity of human CCs to vitrification should be considered during ARTs.

Mesenchymal Stem Cell-Conditioned Medium Modulates Apoptotic and Stress-Related Gene Expression, Ameliorates Maturation and Allows for the Development of Immature Human Oocytes after Artificial Activation

The aim of the present study was to determine whether mesenchymal stem cell-conditioned medium (MSC-CM) modulates apoptotic and stress-related gene expression, and ameliorates maturation and developmental potential of immature human oocytes after artificial activation. A total of 247 surplus immature germinal vesicle (GV) oocytes obtained from infertile women were allocated into two in vitro maturation (IVM) groups: 1: GV oocytes (n = 116) matured in vitro (fIVM), and 2: GV oocytes (n = 131) that were vitrified, then in vitro matured (vIVM). Also, two maturation media were used: Alpha-minimum essential medium (α-MEM) and human umbilical cord-derived MSCs (hUCM). After 36 h of incubation, the IVM oocytes were examined for nuclear maturation. In IVM-matured oocytes, cytoplasmic maturation was evaluated after artificial activation through Ionomycin. Moreover, the quantitative expressions of B-cell CLL/lymphoma 2 (BCL2), BCL2-associated X protein (BAX), superoxide dismutase (SOD), and Heat shock proteins (HSP70) in matured oocytes were assessed by quantitative Real-time polymerase chain reaction (qRT-PCR) and compared with fresh and vitrified in vivo matured oocytes, which were used as fIVM and vIVM controls, respectively. The highest maturation rate was found in hUCM in fIVM, and the lowest maturation rate was found using α-MEM in vIVM (85.18% and 71.42%, respectively). The cleavage rate in fIVM was higher than that in vIVM (83.4% vs. 72.0%). In addition, the cleavage rate in α-MEM was lower than that in the hUCM (66.0% vs. 89.4%). Furthermore, the difference between parthenote embryo arrested in 4-8 cells (p < 0.04) and the quality of embryo arrested in 8-cell (p < 0.007) were significant. The developmental stages of parthenote embryos in hUCM versus α-MEM were as follows: 2-4 cell (89.45% vs. 66.00%, respectively), 4-8 cell (44.31% vs. 29.11%, respectively), morula (12.27% vs. 2.63%, respectively), and blastocysts (2.5% vs. 0%, respectively). The messenger RNA (mRNA) expression levels of BCL2, BAX and SOD were significantly different (p < 0.05) between the matured IVM oocytes. Overall, hUCM showed potential efficacy in terms of ameliorating oocyte maturation and in promoting the development and mRNA expression of BAX, BCL2, and SOD.

Survival and developmental competence of bovine embryos at different developmental stages and separated blastomeres after vitrification in different solutions

Generating techniques to enhance the success of blastomere separation is important for bovine economy, because it increases the number of transferable embryos. This study aimed to identify the optimum cryoprotectants for the vitrification of bovine embryos and the separation of blastomeres at different stages. In experiment 1, expanded blastocysts were vitrified in two different vitrification solutions, either (1) ethylene glycol (EG) + propylene glycol (PG) or (2) EG. The survival rate of blastocysts in the EG + PG was higher than that of the EG. In experiment 2, intact two-cell and eight-cell stage embryos were vitrified in the same solutions used in experiment 1. The EG + PG produced more dead embryos than the EG (P < 0.05). In the EG, the rate of blastocyst formation was similar for the vitrified two- and eight-cell embryos and the non-vitrified ywo-cell embryos. In experiment 3, separated blastomeres of two- and eight-cell embryos were vitrified in EG. There was no difference in the rate of blastocyst formation and total number of cells between the two vitrified groups. In summary, at the blastocyst stage, EG + PG was superior, based on both survival rates and cell numbers; however, at the 2-8 cell stage, the use of EG alone was better than the other groups.

Vitrification of mouse MII oocytes: Developmental competency using paclitaxel

OBJECTIVE

Oocyte cryopreservation provides an important alternative for fertility preservation for women who will be treated with cytotoxic drugs. However, it can cause spindle disorganization of microtubules, putting the zygote at risk for aneuploidy. Paclitaxel is known to stabilize the microtubules that constitute the spindle. The aim of this study was to investigate the suitable concentration of paclitaxel for adding to the vitrification media to improve the developmental potential of post-thawed mature oocytes to blastocyst formation in mice.

MATERIALS AND METHODS

A total of 300 MII oocytes were retrieved from superovulated mice, and were divided into three groups of control, Experimental I, and Experimental II. Oocytes in Experimental I and Experimental II were cryopreserved in the presence of 0.5μM or 1μM of paclitaxel in vitrification media, respectively. After thawing, all oocytes were incubated in G-IVF medium for 1 hour. From each group,12 oocytes were selected for viability evaluation by Hoechst/propidium iodide nuclear staining. Standard in vitro fertilization was performed on the rest of the oocytes and embryo development was followed to the blastocyst stage.

RESULTS

Fertilization rate was not significantly different between the three groups. However, the cleavage rate (55%) in Experimental II group was significantly lower compared to Experimental I (88%) and control groups (83%). There was a detectable difference between the three groups at the blastocyst rate (Experimental I and control groups, p = 0.004; Experimental II vs. control and Experimental I, p < 0.001). The highest rates of parthenogenesis and arrest were in Experimental II (16% and 21%, respectively) compared with control (6% and 5%, respectively) and Experimental I (5% and 3%, respectively). There was also a significant decrease in viability rate of oocytes in Experimental II compared to the other groups.

CONCLUSION

A high concentration of paclitaxel, an anticancer drug, interrupted the mouse oocyte competency when supplemented to vitrification media. Consequently, the optimal concentration of this cytoskeleton stabilizer may improve the post-thawed developmental abilities of oocytes.

The effects of different types of media on in vitro maturation outcomes of human germinal vesicle oocytes retrieved in intracytoplasmic sperm injection cycles

OBJECTIVE

Optimizing in vitro maturation (IVM) media to achieve better outcomes has been a matter of interest in recent years. The aim of this prospective clinical trial was to investigate the effects of different media on the IVM outcomes of immature oocytes at the germinal vesicle (GV) stage.

METHODS

A total of 400 immature oocytes at the GV stage with normal morphology were retrieved from 320 infertile women aged 31±4.63 years during stimulated intracytoplasmic sperm injection (ICSI) cycles. They were divided into groups of homemade IVM medium (I, n=100), cleavage medium (II, n=100), blastocyst medium (III, n=100), and Sage IVM medium (IV, n=100) and cultured for 24 to 48 hours at 37℃. ICSI was performed, and the rates of fertilization and embryo formation were compared across the four groups.

RESULTS

In the 400 retrieved GV oocytes, the total maturation rates showed significant differences in groups I to IV (55%, 53%, 78%, and 68%, respectively, p<0.001). However, there were no significant differences in the fertilization, embryo formation, or arrest rates of metaphase II oocytes across these groups. In all groups, GV maturation was mostly completed after 24 hours, with fewer oocytes requiring 48 hours to mature (p<0.01). Moreover, the rate of high-quality embryos was higher in group IV than in the other groups (p=0.01).

CONCLUSION

The quality of the IVM medium was found to affect clinical IVM outcomes. Additionally, blastocyst medium may be a good choice in IVM/ICSI cycles as an alternative IVM medium.

Artificial shrinkage of blastocoel using a laser pulse prior to vitrification improves clinical outcome

PURPOSE

Blastocysts contain a large amount of fluid in the blastocoel, which may pose a risk for ice crystal formation during vitrification. This study aimed to evaluate the effectiveness of laser-induced artificial shrinkage of blastocoel before vitrification on clinical outcome.

METHODS

Patients were divided into two groups: a control group with untreated, expanded blastocysts (n = 115) and a study group with blastocoel artificially eliminated by a laser pulse prior to vitrification (n = 309). Blastocyst survival, clinical pregnancy, and implantation rates were compared.

RESULT(S)

The survival rate was significantly higher in the study group compared with the control group (97.3 and 74.9 %, respectively; p > 0.01). The clinical pregnancy and implantation rates of the study group were significantly higher (p < 0.01) than that of the control group (clinical pregnancy, 67.2 vs. 41.1 %; implantation, 39.1 vs. 24.5 %.

CONCLUSION(S)

This study demonstrated that the removal of blastocoel fluid before vitrification by laser pulse of in vitro-produced human blastocysts significantly improves blastocyst survival, clinical pregnancy, and implantation rates.

Safe and efficient method for cryopreservation of human induced pluripotent stem cell-derived neural stem and progenitor cells by a programmed freezer with a magnetic field

Stem cells represent a potential cellular resource in the development of regenerative medicine approaches to the treatment of pathologies in which specific cells are degenerated or damaged by genetic abnormality, disease, or injury. Securing sufficient supplies of cells suited to the demands of cell transplantation, however, remains challenging, and the establishment of safe and efficient cell banking procedures is an important goal. Cryopreservation allows the storage of stem cells for prolonged time periods while maintaining them in adequate condition for use in clinical settings. Conventional cryopreservation systems include slow-freezing and vitrification both have advantages and disadvantages in terms of cell viability and/or scalability. In the present study, we developed an advanced slow-freezing technique using a programmed freezer with a magnetic field called Cells Alive System (CAS) and examined its effectiveness on human induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NS/PCs). This system significantly increased cell viability after thawing and had less impact on cellular proliferation and differentiation. We further found that frozen-thawed hiPSC-NS/PCs were comparable with non-frozen ones at the transcriptome level. Given these findings, we suggest that the CAS is useful for hiPSC-NS/PCs banking for clinical uses involving neural disorders and may open new avenues for future regenerative medicine.

[Vitrification: Principles and results]

Sperm and embryos cryopreservation is a commonly applied technique for several years. Recently authorized in France, vitrification tends to replace gradually the conventional technique of slow freezing, so upsetting the practices in the management of patients. It allows from now on the cryopreservation of oocytes and opens new perspectives in egg donation either still in fertility preservation. This review thus attempted to examine the contribution of vitrification in the freezing of oocytes and human embryos at various stages of development. If obviously vitrification appears as the current method of choice for the cryopreservation of oocytes as well as blastocysts, the results are less cut as regards embryos to early stages. No increase in adverse obstetric and perinatal outcomes in children conceived from vitrified oocytes or embryos is noted in the literature.

The effect of vitrification on maturation and viability capacities of immature human oocytes

BACKGROUND

15 % of oocytes collected from Assisted Reproductive Technology (ART) cycles are immature. These oocytes may be matured following in vitro maturation (IVM) program. It is possible to cryopreserve the immature oocytes for further use in ART after application of IVM.

OBJECTIVE

The aim was to determine the maturation rate and viability of human oocytes that were matured in vitro after vitrification program.

MATERIALS AND METHODS

63 women (19-43 years old) who underwent controlled ovarian stimulation for ART were included in this study. 53 immature oocytes were used for fresh group (fIVM) and 50 immature oocytes for vitrification group (vIVM). The maturation medium was Ham's F10 supplemented with 0.75 IU FSH, 0.75 IU LH and 40 % human follicular fluid (HFF). After 36 h, maturation and morphology of all oocytes were assessed. Also, the oocyte viability was assessed using PI/Hoechst immunostaining technique.

RESULTS

The maturation rates were reduced in vIVM group (56.0 %) in comparison to fIVM group (88.7 %; P < 0.001). Oocyte viability rate were also reduced in vIVM group (56.0 %) in comparison to fIVM (86.8 %, P < 0.007).

CONCLUSIONS

Cryopreservation via vitrification reduced both the maturation capacity and viability of human oocytes in IVM technology. It is, therefore, recommended to apply IVM on fresh immature oocytes, instead.

Outcomes of day 3 embryo transfer with vitrification using Cryoleaf: a 3-year follow-up study

OBJECTIVE

To compare success rates of vitrified-warmed with fresh and frozen-thawed ETs

DESIGN

Retrospective.

SETTING

Public fertility center.

PATIENT(S)

Cryopreserved- thawed/warmed ETs were included in this study. Fresh cycles, in which supernumerary embryos were cryopreserved, were set as the fresh control group.

INTERVENTION(S)

Supernumerary day 3 embryos were cryopreserved by slow-freezing or vitrification and transferred after thawing or warming.

MAIN OUTCOME MEASURE(S)

Comparison of two cryopreservation techniques with respect to post-thaw survival of embryos, implantation and pregnancy rates, neonatal outcome, and congenital birth defects.

RESULTS

A total of 962 fresh, 151 freezing-thawed and 300 vitrified-warmed cycles were included in this study. The survival and intact cell rates in the vitrification group were significantly higher compared with those in the slow freezing group (88.5 % vs 74.5 % and 86.6 % vs 64.0 %). The implantation, clinical pregnancy and live birth rates of the vitrification group were similar to the fresh and significant higher than slow freezing group. There were no significant differences in mean gestational age, birth weight, stillbirth, birth defects and the prevalence of neonatal diseases among three groups.

CONCLUSION

Vitrified-warmed ETs yield comparable outcomes with fresh ETs and is superior to frozen-thawed ETs regarding the survival rate and clinical outcomes.

A critical appraisal of cryopreservation (slow cooling versus vitrification) of human oocytes and embryos

BACKGROUND

Vitrification is now a commonly applied technique for cryopreservation in assisted reproductive technology (ART) replacing, in many cases, conventional slow cooling methodology. This review examines evidence relevant to comparison of the two approaches applied to human oocytes and embryos at different developmental stages.

METHODS

Critical review of the published literature using PubMed with particular emphasis on studies which include data on survival and implantation rates, data from fresh control groups and evaluation of the two approaches in a single setting.

RESULTS

Slow cooling is associated with lower survival rates and compromised development relative to vitrification when applied to metaphase II (MII) oocytes, although the vitrification results have predominantly been obtained using direct contact with liquid nitrogen and there is some evidence that optimal protocols for slow cooling of MII oocytes are yet to be established. There are no prospective randomized controlled trials (RCTs) which support the use of either technique with pronuclear oocytes although vitrification has become the method of choice. Optimal slow cooling, using modifications of traditional methodology, and vitrification can result in high survival rates of early embryos, which implant at the same rate as equivalent fresh counterparts. Many studies report high survival and implantation rates following vitrification of blastocysts. Although slow cooling of blastocysts has been reported to be inferior in some studies, others comparing the two approaches in the same clinical setting have demonstrated comparable results. The variation in the extent of embryo selection applied in studies can lead to apparent differences in clinical efficiency, which may not be significant if expressed on a 'per oocyte used' basis.

CONCLUSIONS

Available evidence suggests that vitrification is the current method of choice when cryopreserving MII oocytes. Early cleavage stage embryos can be cryopreserved with equal success using slow cooling and vitrification. Successful blastocyst cryopreservation may be more consistently achieved with vitrification but optimal slow cooling can produce similar results. There are key limitations associated with the available evidence base, including a paucity of RCTs, limited reporting of live birth outcomes and limited reporting of detail which would allow assessment of the impact of differences in female age. While vitrification has a clear role in ART, we support continued research to establish optimal slow cooling methods which may assist in alleviating concerns over safety issues, such as storage, transport and the use of very high cryoprotectant concentrations.

Predicting and preventing ovarian hyperstimulation syndrome (OHSS): the need for individualized not standardized treatment

Ovarian hyperstimulation syndrome (OHSS) is the most serious complication of controlled ovarian stimulation (COS) as part of assisted reproductive technologies (ART). While the safety and efficacy of ART is well established, physicians should always be aware of the risk of OHSS in patients undergoing COS, as it can be fatal. This article will briefly present the pathophysiology of OHSS, including the key role of vascular endothelial growth factor (VEGF), to provide the foundation for an overview of current techniques for the prevention of OHSS. Risk factors and predictive factors for OHSS will be presented, as recognizing these risk factors and individualizing the COS protocol appropriately is the key to the primary prevention of OHSS, as the benefits and risks of each COS strategy vary among individuals. Individualized COS (iCOS) could effectively eradicate OHSS, and the identification of hormonal, functional and genetic markers of ovarian response will facilitate iCOS. However, if iCOS is not properly applied, various preventive measures can be instituted once COS has begun, including cancelling the cycle, coasting, individualizing the human chorionic gonadotropin trigger dose or using a gonadotropin-releasing hormone (GnRH) agonist (for those using a GnRH antagonist protocol), the use of intravenous fluids at the time of oocyte retrieval, and cryopreserving/vitrifying all embryos for subsequent transfer in an unstimulated cycle. Some of these techniques have been widely adopted, despite the scarcity of data from randomized clinical trials to support their use.

Efficiency of aseptic open vitrification and hermetical cryostorage of human oocytes

The present study reports, as far as is known for the first time, the safety of UV sterilization of liquid nitrogen and hermetical cryostorage of human oocytes by comparing the efficiency of fresh and vitrified sibling oocytes of infertile patients. A prospective randomized study on sibling oocytes of 31 patients was carried out. Metaphase-II oocytes were randomized for intracytoplasmic sperm injection and the supernumerary sibling oocytes were vitrified using a novel Cryotop aseptic procedure (UV liquid nitrogen sterilization and hermetical cryostorage). After unsuccessful attempts with fresh oocytes, vitrified sibling oocytes were injected. Mean outcome measures observed were fertilization, cleavage and top-quality embryo rates. No significant differences were observed between the fresh and vitrified-warmed sibling oocytes: oocyte fertilization was 88.3% versus 84.9%; cleavage 72.6% versus 71.0%; top-quality embryos 33.8% versus 26.3% and mean number of transferred embryos 2.6 ± 0.1 versus 2.5 ± 0.1, respectively. Clinical pregnancy rate per cycle with vitrified-warmed oocytes was 35.5% (implantation rate 17.1%) and seven healthy babies were born. This study demonstrated that UV liquid nitrogen sterilization and hermetical cryostorage does not adversely affect the developmental competence of vitrified oocytes, allowing safe aseptic open vitrification applicable under strict directives on tissue manipulation.