In vitro oocyte maturation and subsequent delayed fertilization is associated with increased embryo aneuploidy

Stereological study of organelle distribution in human mature oocytes

The ultrastructure of human oocytes has been described only qualitatively. To offer a precise organelle spatial distribution and organelle volume during the main maturation stages, we previously conducted stereological studies on prophase-I (GV) and metaphase-I (MI) oocytes, and here we present results on metaphase-II (MII) oocytes. Five donor oocytes from different donors were processed for transmission electron microscopy, and quantification of organelle distribution was performed using point-counting stereology. Statistical tests compared the means of the relative volumes occupied by organelles among oocyte regions. The most abundant organelles were elements of the smooth endoplasmic reticulum (SER), such as SER small vesicles, SER medium vesicles, SER large vesicles and SER isolated tubules, along with mitochondria, followed by SER tubular aggregates, cortical vesicles and lysosomes. Significant differences between oocyte regions were found for lysosomes, cortical vesicles and SER large vesicles. Comparisons of MII oocytes to previous findings in GV and MI oocytes evidenced specific patterns of organelle distribution and relative volumes. This final evaluation thus enables to track organelle spatial reorganization across oocyte stages, which, in addition to gathered knowledge, may be useful to assist in improvements of stimulation protocols, in-vitro maturation media and cryopreservation techniques.

Assessing the developmental competence of oocytes matured following rescue in vitro maturation: a systematic review and meta-analysis

PURPOSE

To assess the developmental competence of oocytes matured following rescue in vitro maturation (IVM).

METHODS

PubMed, EmBASE, and SCOPUS were systematically searched for peer-reviewed original papers using relevant keywords and Medical Subject Heading terms. Study quality was assessed using the Newcastle-Ottawa Scale. Odds ratios with a 95% confidence interval were calculated by applying a random effects model. The primary outcomes were fertilization and blastulation rates. Secondary outcomes included abnormal fertilization, cleavage, euploidy, clinical pregnancy, and live-birth rates.

RESULT

Twenty-four studies were included in the meta-analysis. The oocytes matured following rescue IVM showed significantly reduced fertilization, cleavage, blastulation, and clinical pregnancy rates compared to sibling in vivo-matured oocytes. No significant differences were found for the euploidy and live-birth rates in euploid blastocyst transfer. In poor responders, a reduced fertilization rate was observed using in vitro-matured GV but not with in vitro-matured MI. A reduced cleavage rate in MI matured overnight compared to < 6 incubation hours was found.

CONCLUSION

Our results showed compromised developmental competence in oocytes matured following rescue IVM. However, in poor responders, rescue IVM could maximize the efficiency of the treatment. Notably, our data suggests using in vitro MI matured within 6 incubation hours.

CLINICAL TRIAL REGISTRATION NUMBER

CRD42023467232.

The developmental potential of mature oocytes derived from rescue in vitro maturation

OBJECTIVE

To examine the developmental competence of immature oocytes in stimulated cycles, that matured after rescue in vitro maturation (IVM) compared with their sibling in vivo matured oocytes.

DESIGN

Retrospective cohort study.

SETTING

IVF clinic.

PATIENTS

A total of 182 patients underwent 200 controlled ovarian stimulation cycles with intracytoplasmic sperm injection cycles in which immature oocytes were retrieved and at least one mature oocyte was obtained through rescue IVM.

INTERVENTION

In vitro culture of immature germinal vesicle (GV) and metaphase I (MI) oocytes, retrieved in stimulated cycles.

MAIN OUTCOME MEASURES

Fertilization rate, cleavage rate, blastulation rate, ploidy of embryos evaluated using preimplantation genetic testing for aneuploidy, morphokinetic parameters and pregnancy outcomes.

RESULTS

In total, 2,288 oocytes were retrieved from 200 cycles. After denudation, 1,056 of the oocytes (46% ± 16%) were classified as metaphase II (MII). A total of 333/375 (89%) of MI oocytes and 292/540 (54%) of GV oocytes matured overnight and underwent intracytoplasmic sperm injection. The fertilization rates of matured oocytes from MI rescue IVM (R-MI) and from GV rescue IVM (R-GV) were comparable with those of their sibling MII oocytes (71% vs. 66%; 66% vs. 63%, respectively). Early cleavage rates (80% ± 35% vs. 92% ± 20%; 80% ± 42% vs. 95% ± 28%, respectively) and blastulation rates (32 ± 40% vs. 62 ± 33%; 24 ± 37% vs. 60 ± 35%, respectively) were significantly decreased in rescue IVM matured oocytes (R-oocytes)-derived zygotes, but the blastocyst (BL) euploidy rate and "good quality" BL rate were comparable with those of MII sibling-derived embryos. In addition, rescue IVM embryos showed significantly higher levels of multinucleation at the 2- and 4-cell stages, as well as higher rates of zygote direct cleavage from one to 3 to 4 cells. Overall, 21 transfers of rescue IVM embryos resulted in 3 healthy live births.

CONCLUSIONS

For patients with a low maturation rate and/or low numbers of mature oocytes at retrieval, rescue IVM may contribute more competent oocytes and additional viable BLs for transfer from the same stimulation cycle, maximizing the chances for pregnancy and live birth.

Brief and long co-incubation of sperm and oocytes for in vitro fertilization: a meta-analysis of randomized controlled trials

Background

There is still no consensus on the optimal time of oocyte–sperm co-incubation during in vitro fertilization and embryo transfer (IVF-ET). The aim of this meta-analysis was to compare the effects of brief (1-6 h) and long (16-24 h) gametes co-incubation time on IVF outcomes.

Methods

The study protocol was registered online through PROSPERO (CRD42022337503) and PRISMA guidelines were followed in the present study. The following databases were searched from inception to May 2022 for randomized controlled trials (RCTs): PubMed, Embase, Cochrane library, Web of Science, using search terms related to IVF, gametes, time of co-incubation and reproductive outcome measure. Studies comparing outcomes of brief co-incubation to that of long co-incubation during IVF, and reporting primary outcome (live birth rate), secondary outcomes (clinical pregnancy rate; ongoing pregnancy rate; miscarriage rate; normal fertilization rate; polyspermy rate; top-quality embryo rate; implantation rate) were searched. A total of 11 studies were included in the meta-analysis. Combined odds ratio (OR) and 95% confidence interval (CI) were calculated for the data. Statistical heterogeneity analysis between studies was assessed by Cochran Q and I² statistic with a significant threshold of P < 0.05. Methodologic quality assessment of RCTs was made for potential risk of bias with Cochrane Risk of Bias Tool.

Results

Compared to long-term co-incubation, brief co-incubation had an advantage in increasing implantation rate (OR: 1.97, 95% CI: 1.52–2.57), ongoing pregnancy rate (OR: 2.18, 95% CI: 1.44–3.29) and top-quality embryo rate (OR: 1.17, 95% CI: 1.02–1.35). However, brief co-incubation of gametes had no advantages in the live-birth rate (OR: 1.09, 95% CI: 0.72–1.65), miscarriage rate (OR: 1.32, 95% CI: 0.55–3.18), clinical pregnancy rate (OR: 1.36, 95% CI: 0.99–1.87) and polyspermy rate (OR: 0.80, 95% CI: 0.48–1.33) than long-term co-incubation. Additionally, the brief co-incubation was associated with lower normal fertilization rate (OR: 0.89, 95% CI: 0.80–0.99), compared with long co-incubation.

Conclusions

Brief co-incubation of gametes had the advantages in increasing implantation rate, ongoing pregnancy rate and top-quality embryo rate than long-term co-incubation. However, the live-birth rate displayed no difference between the two in vitro fertilization methods. Gametes co-incubation time should be individualized according to each patient’s IVF history, infertility causes and the semen parameters.

Developmental potential of immature human oocytes aspirated after controlled ovarian stimulation

PURPOSE

Intracytoplasmic sperm injection (ICSI) for initially immature oocytes that mature in vitro is controversial and practice varies widely. While it may increase the number of usable embryos, it may also be time-intensive and potentially low-yield. This study sought to elucidate which patients may benefit from ICSI of initially immature oocytes that matured in vitro.

METHODS

A retrospective study comparing fertilization, cleavage, blastulation, and embryo usage rates between sibling initially immature and mature oocytes that underwent ICSI between 2015 and 2019 was performed. Outcomes of initially immature oocytes were stratified by initial maturation stage, timing of progression to metaphase II (MII) in vitro, percentage of mature oocytes in the cycle, and female age.

RESULTS

Ten thousand eight hundred seventeen oocytes from 889 cycles were included. Of 3137 (29.0%) initially immature oocytes, 418 (13.3%) reached MII later on the day of retrieval (day 0) and 1493 (47.6%) on day 1. Overall, embryos originating from initially immature oocytes had lower cleavage and blastulation rates compared to those from initially mature oocytes (P<0.05, all groups). However, embryos from oocytes that matured later on day 0 comprised a unique subset that had clinically similar cleavage (75% vs 80%, RR 0.93, P=0.047) and blastulation rates (41% vs 50%, RR 0.81, P=0.024) compared to initially mature oocytes. Women with low percentages of mature oocytes in the cycle overall and women ≥40 in cleavage cycles derived the highest relative benefit from the use of immature oocytes.

CONCLUSION

ICSI of immature oocytes, particularly those that mature later on the day of retrieval, may improve numbers of usable embryos. This study supports routine reassessment of immature oocytes for progression to MII and ICSI on day 0. An additional reassessment on day 1 may also be of use in older women or those with low percentage of mature oocytes.

Immature oocyte incidence: Contributing factors and effects on mature sibling oocytes in intracytoplasmic sperm injection cycles

Objective

The aim of this study was to investigate which factors contribute to the incidence of immature oocytes (germinal vesicle -GV- and metaphase I -MI-) and how they impact the intracytoplasmic sperm injection (ICSI) outcomes of sibling mature oocytes.

Methods

Data from 3,920 cycles performed from June/2010 to August/2016 in a private university-affiliated IVF center were evaluated for the influence of controlled ovarian stimulation protocol (COS) on immature oocytes incidence and its effects on ICSI outcomes.

Results

MI (p=0.004) and GV (p=0.029) number were negatively correlated with gonadotropin dose. Patients stimulated by rFSH had increased GV/oocyte rate in both GnRH agonists (p<0.001) and antagonist (p=0.042) protocols, in comparison to rFSH associated with rLH protocol. MI and GV/oocyte rates were negatively correlated to fertilization (p<0.001), high-quality embryo on da p<0.001; GV/oocyte p=0.033) and pregnancy (MI/oocyte p=0.002; GV/oocyte p=0.013) rates. Cycles above a 10.5% MI/oocyte cut-off were correlated to higher response to ovarian stimulation, poor embryo development and almost two times lower pregnancy rate. Immature oocyte incidence is affected by COS and impacts on ICSI outcomes.

Conclusion

Our evidence suggests that oocytes derived from a cohort with high incidence of maturation fail may have detrimental clinical outcomes.

Could fertility clinics offer a sizable improvement of live birth rates by maturing post-GVBD oocytes in vitro?

PURPOSE

The objective of this study is to analyze the potential of immature, denuded, post-GVBD (germinal vesicle breakdown) oocytes (including prometaphase I, metaphase I, and prometaphase II stages) to result live birth after in vitro maturation. Furthermore, we compared two culture media to identify which of them provides better reproductive outcomes when used for in vitro maturation.

METHODS

We performed a retrospective cohort study including 4022 IVF-ICSI (in vitro fertilization-intracytoplasmic sperm injection) cycles between 2011 and 2015. A total of 4450 immature post-GVBD oocytes from 1442 cycles were cultured in vitro; of these, 2364 oocytes reached MII (metaphase II) stage (IVMC oocytes, in vitro meiotic completion) and were fertilized. Overall, 3933 embryo transfers were performed: 3579 were embryos derived from MII oocytes (ET-MII); 264 were embryos derived from MII + IVMC oocytes (ET-MIX), and 90 embryos from IVMC oocytes (ET-IVMC). In total, 399 IVMC embryos were transferred.

RESULTS

Maturation rate for immature post-GVBD oocytes was 54.1%. G-2™PLUS (Vitrolife) medium provided significantly higher maturation rate (p < 0.001) than G-IVF™PLUS (Vitrolife) (65.7% vs. 42.5%, p < 0.001). Embryos in ET-IVMC in cleavage stage had an average morphological score of 6.8/10 (7.7 in ET-MII; p < 0.001). Regarding reproductive outcomes, ET-IVMC gave 11.1% biochemical pregnancy rate, 10.0% clinical pregnancy rate, 7.8% ongoing pregnancy rate, and 5.6% live birth rate.

CONCLUSIONS

Embryos arising from IVMC oocytes resulted in a live birth rate of 5.6%. We suggest that in vitro maturation of denuded immature post-GVBD oocytes should be performed at the very least when few MII are collected, and likely in all patients, as they provide acceptable maturation and fertilization rates, and a sizeable increase in live birth.

Advanced mare age impairs the ability of in vitro-matured oocytes to correctly align chromosomes on the metaphase plate

Background

Advanced mare age is associated with declining fertility and an increased risk of early pregnancy loss. Compromised oocyte quality is probably the primary reason for reduced fertility, but the defects predisposing to embryonic death are unknown. In women, advanced age predisposes to chromosome segregation errors during meiosis, which lead to embryonic aneuploidy and a heightened risk of miscarriage.

Objectives

To evaluate the effect of advanced mare age on chromosome alignment and meiotic spindle morphology in in vitro‐matured (IVM) oocytes.

Study design

Morphometric and morphological analysis.

Methods

To investigate differences in spindle organisation and chromosome alignment between young and old mares, oocytes collected from slaughtered mares were divided into two groups depending on mare age (young, ≤14 years and old, ≥16 years), IVM and stained to visualise chromatin and alpha‐tubulin. Spindle morphology, morphometry and chromosome (mis)alignment were evaluated by confocal microscopy and 3D image analysis.

Results

Oocytes from old mares showed a higher incidence of chromosome misalignment (47.4% vs. 4.5%; P<0.001) and a thicker metaphase plate (mean ± s.d.: 5.8 ± 1.0 μm vs. 4.9 ± 0.9 μm; P = 0.04) than oocytes from young mares. Although no differences in spindle morphometry were detected between old and young mares, an increased major spindle axis length was associated with chromosome misalignment (mean ± s.d.: 25.3 ± 6.1 μm vs. 20.8 ± 3.3 μm; P = 0.01) irrespective of age.

Main limitations

The oocytes were IVM and may not exactly reflect chromosome misalignment in vivo.

Conclusions

Advanced mare age predisposes to chromosome misalignment on the metaphase II spindle of IVM oocytes. The compromised ability to correctly align chromosomes presumably predisposes to aneuploidy in resulting embryos and thereby contributes to the age‐related decline in fertility and increased incidence of early pregnancy loss.

The Summary is available in Portuguese – see Supporting Information

In vitro maturation affects chromosome segregation, spindle morphology and acetylation of lysine 16 on histone H4 in horse oocytes

Implantation failure and genetic developmental disabilities in mammals are caused by errors in chromosome segregation originating mainly in the oocyte during meiosis I. Some conditions, like maternal ageing or in vitro maturation (IVM), increase the incidence of oocyte aneuploidy. Here oocytes from adult mares were used to investigate oocyte maturation in a monovulatory species. Experiments were conducted to compare: (1) the incidence of aneuploidy, (2) the morphology of the spindle, (3) the acetylation of lysine 16 on histone H4 (H4K16) and (4) the relative amount of histone acetyltransferase 1 (HAT1), K(lysine) acetyltransferase 8 (KAT8, also known as MYST1), histone deacetylase 1 (HDAC1) and NAD-dependent protein deacetylase sirtuin 1 (SIRT1) mRNA in metaphase II stage oocytes that were in vitro matured or collected from peri-ovulatory follicles. The frequency of aneuploidy and anomalies in spindle morphology was increased following IVM, along with a decrease in H4K16 acetylation that was in agreement with our previous observations. However, differences in the amount of the transcripts investigated were not detected. These results suggest that the degradation of transcripts encoding for histone deacetylases and acetyltransferases is not involved in the changes of H4K16 acetylation observed following IVM, while translational or post-translational mechanisms might have a role. Our study also suggests that epigenetic instabilities introduced by IVM may affect the oocyte and embryo genetic stability.

Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes

The field of assisted reproduction has been developed to treat infertility in women, companion animals, and endangered species. In the horse, assisted reproduction also allows for the production of embryos from high performers without interrupting their sports career and contributes to an increase in the number of foals from mares of high genetic value. The present manuscript describes the procedures used for collecting immature and mature oocytes from horse ovaries using ovum pick-up (OPU). These oocytes were then used to investigate the incidence of aneuploidy by adapting a protocol previously developed in mice. Specifically, the chromosomes and the centromeres of metaphase II (MII) oocytes were fluorescently labeled and counted on sequential focal plans after confocal laser microscope scanning. This analysis revealed a higher incidence in the aneuploidy rate when immature oocytes were collected from the follicles and matured in vitro compared to in vivo. Immunostaining for tubulin and the acetylated form of histone four at specific lysine residues also revealed differences in the morphology of the meiotic spindle and in the global pattern of histone acetylation. Finally, the expression of mRNAs coding for histone deacetylases (HDACs) and acetyl-transferases (HATs) was investigated by reverse transcription and quantitative-PCR (q-PCR). No differences in the relative expression of transcripts were observed between in vitro and in vivo matured oocytes. In agreement with a general silencing of the transcriptional activity during oocyte maturation, the analysis of the total transcript amount can only reveal mRNA stability or degradation. Therefore, these findings indicate that other translational and post-translational regulations might be affected. Overall, the present study describes an experimental approach to morphologically and biochemically characterize the horse oocyte, a cell type that is extremely challenging to study due to low sample availability. However, it can expand our knowledge on the reproductive biology and infertility in monovulatory species.

Effects of sperm insemination on the final meiotic maturation of mouse oocytes arrested at metaphase I after in vitro maturation

Objective

The aims of this study were to investigate whether fertilization could induce the resumption of meiosis in mouse oocytes arrested at metaphase I (MI) after in vitro maturation (IVM), and to investigate the effect of Ca²⁺ chelator treatment at the time of fertilization on the transition from MI to metaphase II (MII).

Methods

MII-stage and arrested MI-stage mouse oocytes after IVM were fertilized, and then embryonic development was monitored. Blastocysts from each group were transferred into 2.5 days post-coitum pseudo-pregnant ICR mice. MI oocytes after IVM were treated with a Ca²⁺ chelator to investigate the effect of Ca²⁺ oscillations on their maturation.

Results

As insemination time increased, the number of oocytes in the MI group that reached the MII stage also increased. The blastocyst rates and total cell numbers in the MII group were significantly higher than in the MI group. No pregnancy occurred in the MI group, but 10 pregnancies were achieved (10 of 12) in the MII group. The proportion of MI oocytes that matured to MII oocytes after fertilization was significantly higher in the non-treated group than in the Ca²⁺ chelator-treated group.

Conclusion

The findings that a higher proportion of MI-arrested oocytes progressed to MII after fertilization and that the MI-to-MII transition was blocked by Ca²⁺ chelator treatments before fertilization indicate that the maturation of MI oocytes to MII oocytes is associated with intracellular Ca²⁺ oscillations driven by fertilization.

Analysis of meiotic spindle and zona pellucida birefringenceof IVM oocytes in PCOS patients

BACKGROUND/AIM

Polycystic ovarian syndrome (PCOS) is one of the most common causes of infertility. One of the best therapeutic options for PCOS patients is intracytoplasmic sperm injection (ICSI). In vitro maturation (IVM) can also be a useful technique for these women. The goal of this study was to evaluate both the zona pellucida (ZP) birefringence and meiotic spindle (MS) of in vivo- and in vitro-matured oocytes from PCOS patients using the PolScope system.

MATERIALS AND METHODS

Immature oocytes undergoing IVM and MII oocytes were obtained from PCOS patients in an ICSI program. Using PolScope, the presence of MS and ZP birefringence was assessed in both in vivo-matured oocytes (n = 32) and IVM oocytes (n = 24). Oocytes were classified as having highly birefringent (HB) ZP and lowly birefringent (LB) ZP. Furthermore, the rates of fertilization after ICSI were evaluated.

RESULTS

The maturation rate was 68.5% after IVM. The percentage of a HB-ZP was significantly higher in the IVM oocytes than in vivo-matured ones (58.3% vs. 31.2%, respectively; P = 0.04). There were similar outcomes for the fertilization rates and MS detection between the two groups (P = 0.80 and P = 0.53, respectively).

CONCLUSION

Clinical IVM is a safe technology for the maturation and maintenance of oocyte integrity in PCOS patients. The use of the noninvasive PolScope is recommended for detection of healthy oocytes in ICSI.

Delayed intracytoplasmic sperm injection (ICSI) with trophectoderm biopsy and preimplantation genetic screening (PGS) show increased aneuploidy rates but can lead to live births with single thawed euploid embryo transfer (STEET)

PURPOSE

The aim of this study was to report the results of IVF with trophectoderm biopsy and preimplantation genetic screening (PGS) following delayed intracytoplasmic sperm injection (ICSI).

METHODS

Patients undergoing IVF with PGS and delayed ICSI were included in the study. Indications for delayed ICSI included absent or poor fertilization via standard insemination or more than 50 % immature oocytes, noted post-cumulus stripping for standard ICSI procedure. Delayed ICSI was performed the day after retrieval due to absent or poor fertilization. The immature oocytes were kept in extended culture, and if demonstrated maturity, ICSI was performed. Primary outcome included fertilization rate and blastocyst stage formation, defined by the number of blastocysts for biopsy. Secondary outcome included aneuploidy rate and pregnancy outcomes following single thawed euploid embryo transfers (STEET).

RESULTS

Sixteen patients with delayed ICSI were included in the study. Twelve were due to poor fertilization and four secondary to immature oocytes. A total of 219 oocytes were retrieved; ten were frozen upon patient request, 168 had standard insemination, and 13 had routine ICSI on the day of retrieval. A total of 129 oocytes underwent delayed ICSI. Sixty-three (49 %) fertilized, 19 (14.7 %) reached blastocysts for biopsy; fivw of which were chromosomally normal (26.3 %). Three patients underwent STEET of a delayed ICSI embryo; all three resulted in live births, including one embryo biopsied on day 8 of development.

CONCLUSION

Fertilization failure or an excessive proportion of immature oocytes in an IVF cycle, necessitating delayed ICSI, showed equivalent fertilization and blast formation rates. With the implementation of trophectoderm biopsy and PGS, these embryos can lead to healthy live born babies.

Paternal influence of sperm DNA integrity on early embryonic development

STUDY QUESTION

Does sperm DNA damage affect early embryonic development?

SUMMARY ANSWER

Increased sperm DNA damage adversely affects embryo quality starting at Day 2 of early embryonic development and continuing after embryo transfer, resulting in reduced implantation rates and pregnancy outcomes.

WHAT IS KNOWN ALREADY

Abnormalities in the sperm DNA in the form of single and double strand breaks can be assessed by an alkaline Comet assay. Some prior studies have shown a strong paternal effect of sperm DNA damage on IVF outcome, including reduced fertilization, reduced embryo quality and cleavage rates, reduced numbers of embryos developing into blastocysts, increased percentage of embryos undergoing developmental arrest, and reduced implantation and pregnancy rates.

STUDY DESIGN, SIZE, DURATION

A cross-sectional study of 215 men from infertile couples undergoing assisted reproduction techniques at the University of Utah Center for Reproductive Medicine.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Sperm from men undergoing ART were analyzed for DNA damage using an alkaline Comet assay and classified into three groups: 'low damage' (0-30%), 'intermediate damage' (31-70%) and 'high damage' (71-100%). The cause of couples' infertility was categorized into one of the three types (male, female or unexplained). Each embryo was categorized as 'good', 'fair' or 'poor' quality, based on the number and grade of blastomeres. The influence of sperm DNA damage on early embryonic development was observed and classified into four stages: peri-fertilization effect (fertilization rate), early paternal effect (embryonic days 1-2), late paternal effect (embryonic days 3-5) and implantation stage effect.

MAIN RESULTS AND THE ROLE OF CHANCE

The paternal effect of sperm DNA damage was observed at each stage of early embryonic development. The peri-fertilization effect was higher in oocytes from patients with female infertility (20.85%) compared with male (8.22%; P < 0.001) and unexplained (7.30%; P < 0.001) infertility factors. In both the early and late paternal effect stages, the low DNA damage group had a higher percentage of good quality embryos (P < 0.05) and lower percentage of poor quality embryos (P < 0.05) compared with the high DNA damage group. Implantation was lower in the high DNA damage (33.33%) compared with intermediate DNA damage (55.26%; P < 0.001) and low DNA damage (65.00%; P < 0.001) groups. The implantation rate was higher following blastocyst transfer (58.33%), when compared with early stage blastocyst (53.85%; P = 0.554) and cavitating morula transfers (34.40%; P < 0.001). Implantation was higher when the female partner age was ≤35 years when compared with >35 year age group (52.75 versus 35.44%; P = 0.008).

LIMITATIONS, REASONS FOR CAUTION

A potential limitation of this study is that it is cross-sectional. Generally in such studies more than one variable could affect the outcome. Analyzing sperm is one part of the equation but a number of environmental and female factors also have the potential to influence embryo development and implantation. Furthermore, the selection of morphologically normal and physiologically motile sperm may result in isolation of sperm with reduced DNA damage. Therefore, selecting the best available sperm for ICSI may lead to experimental bias, as the selected sperm do not represent the overall sperm population in which the DNA damage is measured. Similar studies on selected sperm and with a larger sample size are now required.

WIDER IMPLICATIONS OF THE FINDINGS

The paternal influence of damaged chromatin is more prominent after zygotic transcriptional activation. A prolonged paternal effect on the developing embryo may be due to the active repair mechanism present in oocytes that tends to overcome the damaged paternal chromatin. The probability of eliminating an embryo fertilized by a sperm with damaged DNA is higher at the blastocyst stage than the cleavage stage; therefore blastocyst transfer could be recommended for better implantation success. Finally, we recommend ICSI treatment for patients with a higher percentage of sperm with DNA damage as well as additional studies with a larger sample size aimed at assessing DNA damage analysis as a diagnostic tool for IVF.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the University of Utah internal funds. The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Chromosomal aberrations in in-vitro matured oocytes influence implantation and ongoing pregnancy rates in a mouse model undergoing intracytoplasmic sperm injection

Implantation failure and early pregnancy loss have been reported to be closely related to the quality of mammalian oocytes; however, the pregnant outcome of embryos from in-vitro matured (IVM) oocytes remains unknown. In this study we examined spindle assembly and chromosome segregation during differentiation, and the duration of IVM of mouse oocytes. The resulting implantation and pregnancy outcomes were analyzed to clarify the relationship between the spindle and chromosomes of IVM oocytes and implantation and early pregnancy. Cumulus-enclosed germinal vesicle oocytes were collected and randomly cultured in IVM medium with different IVM durations. One part of IVM oocytes were analyzed the spindle and chromosome morphology by immunofluorescence method, and the other part of them were fertilized by intracytoplasmic sperm injection. The resulting embryos were transferred into pseudo-pregnant female mice, and the post-implantation and full term development was observed. The chromosome aberrations and incorrect spindle assembly seems not affect the early development and blastocyst cell number derived from IVM oocytes, however the development potential of the resulting embryos after implantation were significant decreased with the ratio increasing of chromosome aberrations and incorrect spindle assembly. Accordingly, the full-term development was also decreased. In conclusion, the present study showed the spindle assembly of in vitro-matured oocytes was one of the most important factors that affected the implantation and ongoing pregnancy rates of IVM oocytes, and the improvement by an appropriate duration of maturation in vitro will enhance the post-implantation development potential of the resulting embryos, and decrease implantation failure and early pregnancy loss.

Short co-incubation of gametes combined with early rescue ICSI: an optimal strategy for complete fertilization failure after IVF

Failed fertilization after conventional IVF is one of the most frustrating experiences in assisted reproductive technology. "Late" rescue ICSI may be not an optimal strategy for treating unfertilized oocytes. Short co-incubation of gametes combined with early rescue ICSI has some advantages for complete fertilization failure after IVF. We evaluate the strategy and the optimal time for early rescue ICSI. A total of 180 patients underwent short co-incubation of gametes combined with early rescue ICSI treatment for complete fertilization failure after IVF (study group). A total of 494 ICSI patients with male factor infertility served as a control group. Clinical pregnancy rate, implantation rate, and live birth rate in the two groups were compared. The study group was divided into three different rescue time intervals (＜6 h, 6-8 h, and ＞8 h). Clinical pregnancy rate, implantation rate, and live birth rate were comparable between the study group and the control group. There was a negative correlation between clinical outcomes and rescue time interval.

Contributing factors for the incidence of aneuploidy in older patients undergoing intracytoplasmic sperm injection cycles

PURPOSE

To evaluate different factors that might affect the incidence of embryo aneuploidy in intracytoplasmic sperm injection cycles (ICSI).

METHODS

One hundred and ninety ICSI cycles in conjunction with preimplantation genetic screening (PGS) were included. The influence of the following variables on the aneuploidy incidence was evaluated: (i) maternal and (ii) paternal ages, (iii) dose of FSH administered, (iv) dose of FSH per number of retrieved matured oocytes (FSH/MII), (v) serum 17β-oestradiol levels on the ovulation trigger day, (vi) aspirated follicles and (vii) retrieved oocytes.

RESULTS

A total of 440 embryos were successfully biopsied, of which 240 were considered euploid and 200 were considered aneuploid. The paternal age (Slope: 0.2, p = 0.372), total dose of FSH (Slope: 0.2, p = 0.218), FSH/MII (Slope: 0.1, p = 0.296) and 17β-oestradiol levels (Slope: 0.2, p = 0.378) were not correlated with the presence of aneuploidy. However, the maternal age (Slope: 1.7, p < 0.01), aspirated follicles (Slope: 1.9, p < 0.01) and retrieved oocytes (Slope: 2.6, p < 0.01) were negatively correlated with the incidence of aneuploidy.

CONCLUSIONS

Even in older patients, lower oocyte yields may represent a more appropriate response to ovarian stimulation, allowing the most competent follicles and oocytes to develop and thereby reducing the occurrence of embryo aneuploidy.

Insufficient histone-3 lysine-9 deacetylation in human oocytes matured in vitro is associated with aberrant meiosis

OBJECTIVE

To characterize histone acetylation during meiosis in human oocytes matured in vitro or in vivo.

DESIGN

Experimental study.

SETTING

University reproductive medical center.

PATIENT(S)

Patients undergoing routine intracytoplasmic sperm injection (ICSI) cycles.

INTERVENTION(S)

Immature and mature oocytes were collected from patients undergoing intracytoplasmic sperm injection.

MAIN OUTCOME MEASURE(S)

Immunohistochemical assessment of the levels of acetylated lysine-9 of histone-3 (H3K9) and lysine-12 of histone-4 (H4K12) combined with spindle and chromosome configurations in in vitro- and in vivo-matured human oocytes. Transcript levels of histone deacetylases (HDACs) 1 and 2 were measured by single-cell quantitative polymerase chain reaction.

RESULT(S)

Acetylation of H3K9 and H4K12 decreased during human oocyte maturation. Residual H3K9 acetylation was found in 37.7% of oocytes matured in vitro, compared with 11.8% in oocytes matured in vivo. Abnormal metaphase spindle was more frequent in oocytes with residual histone acetylation than without (51.6% vs. 25.4%, respectively). Treatment with the HDAC inhibitor trichostatin A increased the incidence of an abnormal metaphase but had no adverse effect on maturation efficiency. Furthermore, expression of HDAC1 transcripts was significantly lower in oocytes matured in vitro versus in vivo.

CONCLUSION(S)

Reduced HDAC1 expression and insufficient histone deacetylation are associated with metaphase defects in human oocytes matured in vitro.

Preimplantation genetic screening: does it help or hinder IVF treatment and what is the role of the embryo?

Despite an ongoing debate over its efficacy, preimplantation genetic screening (PGS) is increasingly being used to detect numerical chromosomal abnormalities in embryos to improve implantation rates after IVF. The main indications for the use of PGS in IVF treatments include advanced maternal age, repeated implantation failure, and recurrent pregnancy loss. The success of PGS is highly dependent on technical competence, embryo culture quality, and the presence of mosaicism in preimplantation embryos. Today, cleavage stage biopsy is the most commonly used method for screening preimplantation embryos for aneuploidy. However, blastocyst biopsy is rapidly becoming the more preferred method due to a decreased likelihood of mosaicism and an increase in the amount of DNA available for testing. Instead of using 9 to 12 chromosome FISH, a 24 chromosome detection by aCGH or SNP microarray will be used. Thus, it is advised that before attempting to perform PGS and expecting any benefit, extended embryo culture towards day 5/6 should be established and proven and the clinical staff should demonstrate competence with routine competency assessments. A properly designed randomized control trial is needed to test the potential benefits of these new developments.

Chromosome abnormality rates in human embryos obtained from in-vitro maturation and IVF treatment cycles

The aim of this retrospective study was to compare the incidence of chromosomal abnormality in embryos from in-vitro maturation (IVM) and IVF cycles. The copy numbers of chromosomes 13, 15, 16, 18, 21, 22, X and Y were assessed with fluorescence in-situ hybridization (FISH) in single blastomeres biopsied from cleavage stage embryos. Spare embryos that were not transferred or cryopreserved were also analysed in full. IVM and IVF groups comprised six and 30 couples, with mean ± SD embryos with FISH result of 8.0 ± 4.4 and 11.7 ± 3.8, respectively. The incidence of chromosomal abnormality per FISH result was similar in IVM and IVF embryos (58.7% versus 57.4%, respectively). When embryos were categorized based on maturation time of oocytes in IVM cycles, embryos derived from oocytes that matured 48 h after collection had a higher chromosomal abnormality rate compared with embryos derived from in-vivo matured oocytes and to embryos derived from oocytes that matured in the first 24 h after collection.

Extended in vitro maturation of immature oocytes from stimulated cycles: an analysis of fertilization potential, embryo development, and reproductive outcomes

PURPOSE

To investigate 24 h in vitro maturation (IVM) of cumulus-stripped immature oocytes from stimulated cycles.

METHODS

263 oocytes identified as immature after cumulus stripping for ICSI were subjected to in vitro maturation (IVM). Fertilization rates and reproductive outcomes of matured oocytes were compared against 234 in vivo matured sibling oocytes (IVO-MII-Sib) from the same cycles (n = 41). Day 2 embryo development was compared against 116 embryos from ICSI cycles having no IVM (IVO-Ext controls).

RESULTS

While fertilization rates were similar between IVM and IVO-MII-Sib oocytes (62.1% vs. 64.0%, p = 0.9909), day 2 embryo quality was reduced in the IVM group compared with IVO-Ext controls as evidenced by fewer embryos having 4 cells (28.3% vs. 54.3%, p = 0.0026), low fragmentation (30.0% vs. 65.2%, p < 0.0001) or perfectly symmetric blastomeres (28.6% vs. 46.9%, p = 0.0371). 0 of 17 IVM embryos with known fate implanted.

CONCLUSION

Efficacy of 24 h IVM for cumulus-stripped GV and MI oocytes for either clinical use or study of normal meiotic maturation is questionable.

Artificial oocyte activation and intracytoplasmic sperm injection

OBJECTIVE

To review different methods for artificial oocyte activation and its impact on intracytoplasmic sperm injection (ICSI).

DESIGN

Literature review.

SETTING

University-based and university-affiliated medical centers.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

None.

RESULT(S)

The ICSI procedure improves fertilization rates in cases of male factor infertility; however, fertilization failure still occurs in 2% to 3% of ICSI cycles. The main cause of failed fertilization is failure to complete oocyte activation. The investigators do not use a variety of mechanical, electrical, and chemical methods to mimic the calcium rise necessary to activate oocytes after ICSI. Chemical activation is the most commonly used method for artificial oocyte activation, resulting in high fertilization rates.

CONCLUSION(S)

Artificial oocyte activation (AOA) may be useful in selected patients who have low fertilization potential. Further studies are required to establish the biosafety of AOA, and clinical tests are needed to evaluate the activation potential of semen samples for proper patient selection.

Rhesus macaque embryos derived from MI oocytes maturing after retrieval display high rates of chromosomal anomalies

BACKGROUND

Rhesus macaque and human preimplantation embryos display similar rates of chromosomal abnormalities. The aim of this study was to determine whether embryos developing from MI oocytes that mature post-retrieval display more chromosomal anomalies than those embryos that are generated from oocytes that are at MII at the time of retrieval.

METHODS

Rhesus macaque oocytes were obtained after hormonal ovarian stimulation. Immediately after retrieval, the oocytes were classified according to their maturational status. Following in vitro fertilization, Day 3 embryos with good morphology and development derived from oocytes maturing post-retrieval and those from oocytes that were mature at the time of retrieval were cytogenetically assessed using a five-color fluorescent in situ fluorescent hybridization assay developed for rhesus macaque chromosomes homologous to human chromosomes 13, 16, 18, X and Y.

RESULTS

Blastomeres from 53 embryos were analyzed. Of the 27 embryos that developed from oocytes that were mature at collection, 18 embryos were chromosomally normal (66.7%), while from the 26 embryos that developed from oocytes that matured post-retrieval, only 9 embryos were chromosomally normal (34.6%).

CONCLUSIONS

These results indicate that embryos developing from oocytes maturing post-retrieval display high rates of chromosomal abnormalities and have therefore a reduced developmental competence. As a result, the clinical relevance of using immature oocytes that are retrieved after stimulated cycles in human IVF warrants further investigation.

Failed fertilization after ICSI and spermiogenic defects

OBJECTIVE

To evaluate the relationship between late spermiogenic events, including histone-protamine replacement, acrosome integrity, and sperm morphology, with fertilization rate after intracytoplasmic sperm injection (ICSI).

DESIGN

Prospective study.

SETTING

Isfahan Fertility and Infertility Center, Royan Institute, Tehran, Iran.

PATIENT(S)

Semen samples from 68 infertile couples undergoing ICSI at Isfahan Fertility and Infertility center were assessed during this study.

INTERVENTION(S)

Semen analysis was carried out according to World Health Organization criteria. Protamine deficiency, acrosin activity, sperm morphology, and acrosome size were assessed by chromomycin A3 (CMA3) staining, gelatinolysis test, and Papanicolaou staining (strict criteria), respectively.

MAIN OUTCOME MEASURE(S)

The correlation between protamine deficiency, sperm morphology, acrosin activity, and acrosome size with each other and fertilization rate were assessed.

RESULT(S)

Percentage CMA3 positivity and mean halo diameter show a significant correlation with fertilization rate. However, no correlation was found between sperm normal morphology and fertilization rate. The mean values of acrosome size and fertilization rate were significantly different when patients were grouped for CMA3 positivity of 40%. Multiple linear regression analysis revealed that only protamine deficiency has direct effect on fertilization rate.

CONCLUSION(S)

Protamine deficiency appears to have a more significant effect on fertilization after ICSI than acrosin activity and semen parameters.

Prognostic value of meiotic spindle imaging on fertilization rate and embryo development in in vitro-matured human oocytes

OBJECTIVE

To evaluate the relationship between spindle visualization and intracytoplasmic sperm injection (ICSI) outcomes in controlled ovarian stimulation (COS) cycles.

DESIGN

Prospective study.

SETTING

Assisted reproduction center.

PATIENT(S)

Thirty patients undergoing ICSI cycles.

INTERVENTION(S)

Meiotic spindle was evaluated before ICSI in 234 in vivo- and 101 in vitro-matured oocytes

MAIN OUTCOME MEASURE(S)

Meiotic spindle imaging, fertilization rate, and embryo development.

RESULT(S)

Spindle was present in 74.3% and 73.8% of the in vivo- and in vitro-matured oocytes, respectively. Spindle detection rate in oocytes derived from germinal vesicle and metaphase-I stage was, respectively, 50% and 86%. The fertilization rate achieved by the in vivo-matured oocytes was 71.8%, and spindle was detected in 75.6% of the fertilized oocytes and only 34.8.% of the nonfertilized oocytes. In the in vitro-matured oocytes, the fertilization rate was 66.1%, and spindle was detected in 81.4% of the fertilized oocytes and in 59.1% of the nonfertilized oocytes. Ten out of 43 (23.2%) in vitro-matured derived embryos were considered to be high quality, all derived from spindle-detected oocytes, which represents an increase of 13.0% on the overall number of high-quality embryos.

CONCLUSION(S)

Meiotic spindle imaging may be useful to predict in vitro-matured oocyte development. However, other factors may contribute to the decreased developmental competence of in vitro-matured oocytes.

Fertilization, embryo development, and clinical outcome of immature oocytes from stimulated intracytoplasmic sperm injection cycles

OBJECTIVE

To evaluate the fertilization and developmental potential of immature oocytes obtained from controlled ovarian hyperstimulated cycles of patients undergoing intracytoplasmic sperm injection (ICSI).

DESIGN

Retrospective study.

SETTING

Academic assisted reproductive technology program.

PATIENT(S)

Two hundred patients with at least one mature oocyte and one immature oocyte (study 1), and 44 patients with no mature oocytes (study 2) at time of oocyte denudation.

INTERVENTION(S)

Oocyte denudation was performed immediately after retrieval. Oocytes were cultured in vitro for 4-6 hours before ICSI and then categorized into four groups: group I, metaphase II (MII) oocytes at denudation; group II, in vitro matured MII oocytes; group III, metaphase I (MI) oocytes that did not progress to MII; and group 4, germinal-vesicle (GV) oocytes that converted to MI.

MAIN OUTCOME MEASURE(S)

Fertilization and embryo development were compared among groups in study 1. Pregnancy and implantation rates were evaluated in study 2.

RESULT(S)

Although the fertilization rate in group III was significantly lower than in groups I and II, no significant difference was found between groups I and II. Day 3 embryos in group I had the highest mean number of blastomeres, proportions of good embryos, and blastocyst formation rate when compared with groups II and III. Two clinical pregnancies were achieved from 26 transfer cycles in study 2, resulting in pregnancy and implantation rates of 7.7% and 4% per transfer cycle, respectively.

CONCLUSION(S)

Although our results show that immature oocytes from stimulated cycles can be normally fertilized and used to increase the number of embryos available for transfer, the increase in number of embryos derived from immature oocytes cannot be efficiently translated into pregnancies and live births. The clinical significance of using immature oocytes in stimulated cycles needs further investigation.

Cystathionine beta synthase participates in murine oocyte maturation mediated by homocysteine

Our previous study demonstrated that cystathionine beta synthase (CBS) is highly expressed in the cumulus-oocyte complex during ovulation. However, the role of CBS during oocyte maturation remains uncertain. In this study, a small-interfering (si) RNA interference (siRNA) approach was used to investigate the potential role of CBS during oocyte maturation. Accompanied with a gradual increase of homocysteine, the introduction of CBS-siRNA into murine granulosa cells selectively depleted the corresponding target mRNA and protein for CBS as assessed by semi-quantitative reverse-transcriptase PCR (RT-PCR) and immunofluorescence staining. When fully grown, germinal vesicle (GV) oocytes matured in vitro for 16 h using medium from transfected granulosa cells, the functional suppression of CBS resulted in a significant increase in the rate of GV-arrested oocytes. The results of this study provide evidence that CBS participates in the process of oocyte maturation. Furthermore, this effect may be fulfilled by conditioning the level of homocysteine in the microenvironment of the oocyte.

In vitro maturation of human oocytes for assisted reproduction

OBJECTIVE

To describe and evaluate the current practice of in vitro maturation of oocytes for assisted reproduction.

DESIGN

Review of the available and relevant literature regarding in vitro maturation of oocytes.

CONCLUSION(S)

In vitro maturation of human oocytes retrieved from antral ovarian follicles is an emerging procedure quickly being incorporated into the realm of assisted reproductive technologies. This new technology has several potential advantages over traditional controlled ovarian hyperstimulation for IVF, such as reduction of costs by minimizing gonadotropin and GnRH analogue use, elimination of ovarian hyperstimulation syndrome, and simplicity of protocol. In vitro maturation of oocytes for assisted reproduction in human beings still is undergoing refinement but currently is providing efficacy and safety outcome comparable to that of traditional IVF in recent selected studies. Implementing in vitro maturation into an established IVF practice is feasible and requires only a few simple adjustments. Crucial to the advancement and optimization of the technology is a better understanding of how to maximize immature oocyte developmental competence and endometrial receptivity.