Improved implantation rate after chemical removal of the zona pellucida

Unlocking the Potential of Assisted Hatching in Assisted Reproductive Technology: A Narrative Review

The present study is set in the broad field of assisted reproductive technologies (ARTs) and examines various procedures under assisted hatching (AH). It also reviews their effects on implantation success rates. The primary emphasis is on explaining who has benefited and how many have benefited from these interventions. The most important factor determining the success rate of ART is implantation. To increase these rates, we use AH in our clinics to enhance each embryo's chances at life and substantially improve overall results. This comprehensive review includes various approaches, such as chemical-based measures (such as applying Tyrode's solution) and mechanical techniques (such as zona drilling and partial zona dissection). The individual techniques are carefully scrutinized, considering their mechanical detailing, methods of applying therapeutic effects, and the appropriateness of matching present social circumstances. The review begins by analyzing the basic nature of AH as a medium for embryo implantation and then focuses on how this detailed view reveals the advantages and drawbacks of various methods. Moreover, the articles discuss improvements in AH technology and many of the most modern technological developments that can help fine-tune ART issues. A major problem with these methodologies is that they involve serious risks and legal complications. However, a broad assessment of these topics allows us to understand their impact on fertility treatments. This review is written as a guidebook for physicians and researchers working in reproductive medicine. It compiles all current knowledge, providing literature to build on successes that will make breakthroughs possible in ART. Indeed, this is a valuable reference for guiding us in navigating complex AH procedures. It advances ARTs step by step toward perfection.

Zona pellucida removal resulted in a successful live birth: Report on a case with recurrent implantation failure due to embryonic bacteria contamination

Key clinical message

In in vitro fertilization (IVF), laser offers several advantages. In this study, we employed laser to eliminate the zona pellucida of a contaminated embryo. This approach helps to rescue embryo with bacterial contamination, and improve embryo-endometrium interaction.

Abstract

To present a case report on the removal of a contaminated zona pellucida from an embryo of patient with a history of recurrent implantation failure (RIF), which was followed by a successful live birth. We present the case of a 34-year-old patient with a history of 3 years of infertility who underwent in vitro fertilization. During the culture process, the embryos became contaminated, leading to three failed implantations. Despite the aneuploidy of the embryo and the implementation of a washing technique, the contamination persisted. In the final attempt, the contaminated zona pellucida was successfully removed using laser, followed by embryo transfer, resulting in a live birth. We provided detailed clinical information, including patient demographics, infertility history, ovarian response, evidence of bacterial contamination, embryo development, treatment protocols, and outcomes. Laser excision of the zona pellucida is a safe and effective method for addressing bacterial infection in embryos.

Domestic cat embryos generated without zona pellucida are capable of developing in vitro but exhibit abnormal gene expression and a decreased implantation rate

The removal of the zona pellucida has been used to improve the in vitro development of domestic cat embryos generated by IVF and SCNT. However, the in vivo development of domestic cat embryos generated without the zona pellucida has not been evaluated. The objective of this study was to evaluate the effects of zona pellucida removal on the in vitro and in vivo development of domestic cat embryos generated by IVF. For this purpose, two experimental groups were created: 1) domestic cat embryos cultured in vitro (Zona-intact group, ZI) and 2) domestic cat embryos cultured in vitro without the zona pellucida (Zona-free group, ZF). Domestic cat embryos were generated by IVF and cultured in vitro for 8 days. In the ZF group, the zona pellucida was removed after IVF, and embryos were cultured using the well of the well system (WOW). Cleavage, morula and blastocyst rates were evaluated in both groups. The diameter and total cell number of blastocysts were assessed. Relative expression of pluripotency (OCT4, SOX2 and NANOG), differentiation (CDX2 and GATA6) and apoptotic markers (BAX and BCL2) was evaluated in blastocysts. Finally, to evaluate in vivo development, embryos at days 5, 6 and 7 of development were transferred into recipient domestic cats, and ultrasonography was performed to evaluate implantation. No differences were observed in the cleavage, morula or blastocyst rates between embryos from the ZI and ZF groups. The diameter (mean ± SD) of blastocysts from the ZF group was greater (253.4 ± 83.3 μm) than that from the ZI group (210.5 ± 78.5 μm). No differences were observed in the relative expression of OCT4, CDX2 or GATA6. However, the relative expression of SOX2 and NANOG was significantly reduced in ZF blastocysts compared to ZI blastocysts. Furthermore, the relative expression of BAX was higher in ZF blastocysts than in ZI blastocysts. Finally, four pregnancies were confirmed after the transfer of ZI embryos (n = 110). However, no pregnancies were observed after the transfer of ZF embryos at the morula or blastocyst stage (n = 56). In conclusion, domestic cat embryos cultured without the zona pellucida were able to develop in vitro until the blastocyst stage. However, the removal of the zona pellucida negatively affected the gene expression of pluripotency and apoptosis markers, and ZF embryos were unable to implant. This might indicate that the removal of the zona pellucida is detrimental for the implantation and in vivo development of domestic cat embryos.

Laser-assisted hatching zona thinning does not improve the pregnancy outcomes of poor-quality blastocysts in frozen-thawed embryo transfer cycle: a retrospective cohort study

It had been suggested, after facilitating the hatching process, improved pregnancy outcomes could be attained in embryos with thick and hard zona. This study aimed to determine the effect of zona thinning on pregnancy outcomes in poor-quality frozen-thawed blastocysts. This retrospective study included 230 women (≤ 40 years) who underwent frozen embryo transfer of poor-quality blastocysts (scored < 3BB). In total, 105 patients were in the assisted hatching group in which the zona was thinned by laser before transfer and 125 patients were in the control group in which the blastocysts were non-manipulated. Patients' demographics, cycle characteristics, and pregnancy outcomes were compared between the assisted hatching group and the control group. Further, regression analysis was applied to test the correlation between assisted hatching and live birth. All parameters in the patients' demographic characteristics and the cycle's characteristics were not significantly different between two groups. As for pregnancy outcomes, the second trimester pregnancy loss was significantly higher in the assisted hatching group (P = 0.035). Other pregnancy outcomes, including implantation rate, clinical pregnancy rate, biochemical miscarriage rate, the first trimester pregnancy loss, ongoing pregnancy rate, and live birth rate were comparable between two groups. The logistic regression analysis demonstrated no association between live birth and assisted hatching (univariate, OR = 0.787, P > 0.05; multivariate, OR = 0.652, P > 0.05), and the area under the receiver operating characteristic curve of the regression model was almost 0.7. It suggested that zona thinning may not be supposed to perform on poor-quality, frozen-thawed blastocysts. The indications of assisted hatching were still needed to further investigate.

Laser-assisted hatching in lower grade cleavage stage embryos improves blastocyst formation: results from a retrospective study

Background

Laser-assisted hatching (LAH) has been widely applied to facilitate blastocyst hatching in IVF-ET treatment, however, the effect of LAH on subsequent development and clinical outcomes of the lower grade cleavage stage embryos (LGCE) remains unknown. Our study aimed at evaluating the effect of LAH on blastocyst formation and the clinical pregnancy outcomes of LGCE embryos after transfer.

Methods

A total of 608 cycles of IVF/ICSI treatment from November 2017 to September 2019 were included in our study as follows: 296 in the LAH group and 312 in the N-LAH group. The total blastocyst rate, usable blastocyst rate, good-grade blastocyst rate and clinical pregnancy rate were statistically compared between the two groups.

Results

The total blastocyst rate (50.7% vs 40.2%, P < 0.001), usable blastocyst rate (31.0% vs 18.6%, P < 0.001) were significantly higher in the LAH group than those in the N-LAH group. After analysis of generalized estimating equations, LAH was positively correlated with the blastocyst rate (B = 0.201, OR 95% CI = 1.074–1.393, P = 0.002), usable blastocyst rate (B = 0.478, OR 95% CI = 1.331–1.955, P < 0.001). However, the clinical pregnancy rate after blastocyst transfer did not differ between LAH group and N-LAH group (49.4% vs 40.0%, P > 0.05, respectively).

Conclusions

A higher proportion of total blastocysts and usable blastocysts can be obtained by LAH in LGCE, which may be beneficial to the outcome of the IVF/ICSI-ET cycle.

Contamination of ART culture Media-The role of semen and strategies for prevention

OBJECTIVE

Microbial contamination of ART culture media is rare but serious. We examined our own experience and conducted a review of the literature with a view to preventing its occurrence and recurrence.

CASE REPORT

A total of 12 cases were recorded during January 2006 to March 2019. The contaminations were caused by semen and were shown to be bacteria that were resistant to the prophylactic antibiotics used in the medium. After the procedures were cancelled due to contaminations, nine husbands received antibiotic treatment, while nine couples changed over to the ICSI program. Eventually, eight couples concluded the study with live birth deliveries, and there was no recurrence of contamination.

CONCLUSION

ART laboratories should preserve all sperm suspension samples until embryo transfer has been completed for the purpose of checking whether contamination has occurred. In addition to antibiotic treatment, implementation of the ICSI procedure during the next ART cycle has already been proven to be effective. In the future, the zona-removal technique may be considered as another potential option.

Assisted hatching on assisted conception (in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI))

BACKGROUND

Failure of implantation and conception may result from inability of the blastocyst to escape from its outer coat, which is known as the zona pellucida. Artificial disruption of this coat is known as assisted hatching and has been proposed as a method for improving the success of assisted conception by facilitating embryo implantation.

OBJECTIVES

To determine effects of assisted hatching (AH) of embryos derived from assisted conception on live birth and multiple pregnancy rates.  SEARCH METHODS: We searched the Cochrane Gynaecology and Fertility Group Specialised Register (until May 2020), the Cochrane Central Register of Controlled Trials (CENTRAL; until May 2020), in the Cochrane Library; MEDLINE (1966 to May 2020); and Embase (1980 to May 2020). We also searched trial registers for ongoing and registered trials (http://www.clinicaltrials.gov - a service of the US National Institutes of Health; http://www.who.int/trialsearch/Default.aspx - The World Health Organization International Trials Registry Platform search portal) (May 2020).

SELECTION CRITERIA

Two review authors identified and independently screened trials. We included randomised controlled trials (RCTs) of AH (mechanical, chemical, or laser disruption of the zona pellucida before embryo replacement) versus no AH that reported live birth or clinical pregnancy data.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. Two review authors independently performed quality assessments and data extraction.

MAIN RESULTS

We included 39 RCTs (7249 women). All reported clinical pregnancy data, including 2486 clinical pregnancies. Only 14 studies reported live birth data, with 834 live birth events. The quality of evidence ranged from very low to low. The main limitations were serious risk of bias associated with poor reporting of study methods, inconsistency, imprecision, and publication bias. Five trials are currently ongoing. We are uncertain whether assisted hatching improved live birth rates compared to no assisted hatching (odds ratio (OR) 1.09, 95% confidence interval (CI) 0.92 to 1.29; 14 RCTs, N = 2849; I² = 20%; low-quality evidence). This analysis suggests that if the live birth rate in women not using assisted hatching is about 28%, the rate in those using assisted hatching will be between 27% and 34%. Analysis of multiple pregnancy rates per woman showed that in women who were randomised to AH compared with women randomised to no AH, there may have been a slight increase in multiple pregnancy rates (OR 1.38, 95% CI 1.13 to 1.68; 18 RCTs, N = 4308; I² = 48%; low-quality evidence). This suggests that if the multiple pregnancy rate in women not using assisted hatching is about 9%, the rate in those using assisted hatching will be between 10% and 14%. When all of the included studies (39) are pooled, the clinical pregnancy rate in women who underwent AH may improve slightly in comparison to no AH (OR 1.20, 95% CI 1.09 to 1.33; 39 RCTs, N = 7249; I² = 55%; low-quality evidence). However, when a random-effects model is used due to high heterogeneity, there may be little to no difference in clinical pregnancy rate (P = 0.04). All 14 RCTs that reported live birth rates also reported clinical pregnancy rates, and analysis of these studies illustrates that AH may make little to no difference in clinical pregnancy rates when compared to no AH (OR 1.07, 95% CI 0.92 to 1.25; 14 RCTs, N = 2848; I² = 45%). We are uncertain about whether AH affects miscarriage rates due to the quality of the evidence (OR 1.13, 95% CI 0.82 to 1.56; 17 RCTs, N = 2810; I² = 0%; very low-quality evidence).

AUTHORS' CONCLUSIONS

This update suggests that we are uncertain of the effects of assisted hatching (AH) on live birth rates. AH may lead to increased risk of multiple pregnancy. The risks of complications associated with multiple pregnancy may be increased without evidence to demonstrate an increase in live birth rate, warranting careful consideration of the routine use of AH for couples undergoing in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI). AH may offer a slightly increased chance of achieving a clinical pregnancy, but data quality was of low grade. We are uncertain about whether AH influences miscarriage rates.

Efficacy of therapies and interventions for repeated embryo implantation failure: a systematic review and meta-analysis

The aim of the present systematic review and meta-analysis was to assess the effect of the different therapeutic options for repeated embryo implantation failure (RIF) on a subsequent IVF cycle outcome. Twenty-two RCTs and nineteen observational studies were included. Pooling of results showed a beneficial effect of intrauterine PBMC infusion on both CPR (RR 2.18; 95% CI 1.58-3.00; p < 0.00001; OR 2.03; 95% CI 1.22-3.36; p = 0.006) and LBR (RR 2.41; 95% CI 1.40-4.16; p = 0.002; OR 3.73; 95% CI 1.13-12.29; p = 0.03), of subcutaneous G-CSF administration on CPR (RR 2.29; 95% CI 1.58-3.31; p < 0.0001) and of intrauterine PRP infusion on CPR (RR 2.45; 95% CI 1.55-3.86; p = 0.0001). Observational studies also demonstrated a positive effect of IVIG and intrauterine hCG infusion on both CPR and LBR and of atosiban on CPR. Studies investigating intrauterine G-CSF infusion, LMWH, intravenous intralipid, hysteroscopy, blastocyst-stage ET, ZIFT, PGT-A and AH failed to observe an impact on IVF outcome. The quality of the evidence that emerged from RCTs focused on intrauterine PBMC infusion and subcutaneous G-CSF administration was moderate. For all other therapies/interventions it varied from low to very low. In conclusion, intrauterine PBMC infusion and subcutaneous G-CSF administration are the most promising therapeutic options for RIF. However, further well conducted RCTs are necessary before their introduction into clinical practice.

Effects of three-area laser-assisted zona thinning in 8-cell human embryos on pregnancy outcomes in vitro fertilization

Objective

This study conducted a preliminary examination of the effects of three-area laser-assisted zona thinning (LAZT) during the cleavage stage of embryo development on the hatching process in human in vitro fertilization-embryo transfer (IVF-ET) with subjects of advanced female age or frozen-thawed (FT) embryos.

Methods

Eight-cell stage embryos were treated with LAZT in three areas of the zona pellucida at 120° intervals. The control group was embryos without LAZT. Of the 72 consecutive fresh cycles and the 28 FT embryo transfer cycles, the patients in 55 fresh cycles and 17 FT cycles declined LAZT, and those cycles were defined as the control group.

Results

In the fresh cycles, the pregnancy rates were similar in the LAZT and control groups. However, in the FT cycles, the pregnancy rate was significantly higher in the LAZT group than in the control group (45.5% in the LAZT group vs. 23.5% in the control group, p<0.05).

Conclusion

These results show that multi-area LAZT resulted in significantly improved pregnancy outcomes in human 8-cell embryos compared to controls.

Revisiting embryo assisted hatching approaches: a systematic review of the current protocols

Zona pellucida (ZP) manipulation, termed "assisted hatching" (AH), has been introduced in order to favor embryo hatching and ultimately improve assisted reproductive technology success but with poor proofs of safety and biological plausibility. We herein provide a systematic review of clinical outcomes following the application of different methods of ZP manipulation on fresh or frozen/thawed embryos at different developmental stages in different groups of patients. Out of the 69 papers that compared the clinical outcomes deriving from hatched versus non-hatched embryos, only 11 considered blastocysts while the rest referred to cleavage stage embryos. The ZP thinning of fresh embryos either by chemical or laser approach was shown to provide very limited benefit in terms of clinical outcomes. Better results were observed with procedures implying a higher degree of zona manipulation, including zona removal. Studies comparing the mechanical or chemical procedures to those laser-mediated consistently reported a superiority of the latter ones over the former. Literature is consistent for a benefit of ZP breaching in thawed blastocysts. This review provides the current knowledge on the AH procedure in order to improve its efficacy in the appropriate context. Embryologists might benefit from the approaches presented herein in order to improve Assisted Reproduction Technologies (ART) outcomes.

Effect of assisted hatching on pregnancy outcomes: a systematic review and meta-analysis of randomized controlled trials

Emerging evidence suggests that assisted hatching (AH) techniques may improve clinical pregnancy rates, particularly in poor prognosis patients; however, there still remains considerable uncertainty. We conducted a meta-analysis to verify the effect of AH on pregnancy outcomes. We searched for related studies published in PubMed, Web of Science, and Cochrane library databases from start dates to October 10, 2015. Totally, 36 randomized controlled trials with 6459 participants were included. Summary odds ratios (ORs) with 95% confidence intervals (CIs) for whether by AH or not were estimated. We found a significant increase in clinical pregnancy (OR = 1.16, 95% CI = 1.00–1.36, I² = 48.3%) and multiple pregnancy rates (OR = 1.50, 95% CI = 1.11–2.01, I² = 44.0%) with AH when compared to the control. Numerous subgroup analyses stratified by hatching method, conception mode, extent of AH, embryos transfer status, and previous failure history were also carried out. Interestingly, significant results of clinical pregnancy as well as multiple pregnancy rates were observed among women who received intracytoplasmic sperm injection, and who received AH which the zona were completely removed. In summary, this meta-analysis supports that AH was associated with an increased chance of achieving clinical pregnancy and multiple pregnancy. Whether AH significantly changes live birth and miscarriage rates needs further investigations.

Transfer of IVF-contaminated blastocysts with removal of the zona pellucida resulted in live births

PURPOSE

Bacterial contamination may cause loss or damage to cultured oocytes or embryos, resulting in cancelation or delaying of a fresh embryo transfer. While live births have been reported following the transfer of embryos contaminated with yeast, very little information is available on how to handle embryos with bacterial contamination. We report two cases of successful pregnancy in patients with bacterial contamination of embryo culture dishes.

METHODS

We retrospectively reviewed 878 oocyte retrievals performed between January 2011 and December 2014. Bacterial contamination was recorded in two split IVF/ICSI cases, where contamination occurred in embryo culture drops containing embryos from conventional insemination but not from ICSI on day 3.

RESULTS

To minimize the adverse effects of bacterial contamination on transfer outcomes, we removed the zona pellucida of contaminated frozen blastocysts and successfully obtained clinical pregnancies following transfer of zona-free blastocysts that were previously contaminated during IVF culture.

CONCLUSIONS

Removal of the zona pellucida is an appropriate approach to handle blastocysts contaminated with bacteria during in vitro culture.

Effect of laser-assisted multi-point zona thinning on development and hatching of cleavage embryos in mice

OBJECTIVE

This study aimed to examine the effect of laser-assisted zona thinning (LAZT) at one or four-points on the blastocyst formation and hatching process in mice with respect to female age.

METHODS

Eight-cell or morula embryos collected from superovulated C57BL female mice with different ages (6-11 and 28-31 weeks) were treated with LAZT at one-point (LAZT1) or four-points (LAZT4). The zona pellucida was thinned to more than 70% of its initial thickness by making two holes of 15-20 µm.

RESULTS

In the young mice, LAZT resulted in a significant increase in early hatching and hatching rates compared to the control group (p<0.05). However, in the old mice, LAZT significantly increased blastocyst formation as well as early hatching and hatching compared to the controls (p<0.05). These effects were more remarkable in LAZT4 than in LAZT1 and in aged mice than in young ones.

CONCLUSION

These results show that multi-point LAZT leads to a significant improvement of blastocyst formation and hatching in mice compared to controls.

Time-lapse observations to analyze the effects of assisted hatching

Purpose

Assisted hatching (AH) is an artificial disruption of the zona pellucida with the aim of facilitating embryo implantation. We used time-lapse observations of mouse embryos to examine the effect of AH in mouse blastocysts.

Methods

AH techniques were performed with acid Tyrode's solution. We compared the rates of blastocyst formation and blastocyst attachment to Ishikawa cells between the control (n = 28) and the AH group (n = 24). To analyze the effects of AH, 8-cell mice embryos were cultured under time-lapse observations (every 15 min). The time required for hatching, the hatching rates, the frequency of contraction, and the contraction rates in the blastocysts were analyzed.

Results

There were no significant differences between the two groups in hatching rate or attachment rate. The times required for hatching were 286 ± 22 min in the AH group and 990 ± 437 min in the control group (P = 0.018). The contraction frequencies in blastocysts were 3.5 ± 0.7 times in the AH group and 7.5 ± 2.5 times in the control group (P = 0.020).

Conclusions

From the time-lapse observations we found that the time required for hatching and the frequency of contraction in blastocysts were both reduced by AH, although blastocyst formation and attachment were not affected.

Assisted hatching on assisted conception (in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI)

BACKGROUND

Failure of implantation and conception may result from an inability of the blastocyst to escape from its outer coat, which is known as the zona pellucida. Artificial disruption of this coat is known as assisted hatching and has been proposed as a method for improving the success of assisted conception by facilitating embryo implantation.

OBJECTIVES

To determine the effect of assisted hatching (AH) of embryos from assisted conception on live birth and multiple pregnancy rates. 

SEARCH METHODS

We searched the Cochrane Menstrual Disorders and Subfertility Group Specialised Register (August 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (August 2012), MEDLINE (1966 to August 2012) and EMBASE (1980 to August 2012).

SELECTION CRITERIA

Three authors identified and independently screened trials. We included randomised controlled trials (RCTs) of AH (mechanical, chemical or laser disruption of the zona pellucida prior to embryo replacement) versus no AH that reported live birth or clinical pregnancy.

DATA COLLECTION AND ANALYSIS

Three authors independently performed quality assessments and data extraction.

MAIN RESULTS

Thirty-one trials reported clinical pregnancy data, including 1992 clinical pregnancies in 5728 women. There was no significant difference in the odds of live birth in the AH group compared with the control group (9 RCTs; odds ratio (OR) 1.03, 95% confidence interval (CI) 0.85 to 1.26, moderate quality evidence), with no evidence of significant heterogeneity (P = 0.38) or inconsistency (I(2) = 6%). Analysis of the clinical pregnancy rates from the nine studies which reported live birth showed a non-significant result (OR 1.03, 95% CI 0.85 to 1.25 ).Analysis of all of the studies included in this update (31 RCTs) showed that the clinical pregnancy rate in women who underwent AH was slightly improved, but the level only just reached statistical significance (OR 1.13, 95% CI 1.01 to 1.27, moderate quality evidence). However, it is important to note that the heterogeneity for this combined analysis for clinical pregnancy rate was statistically significant (P = 0.001) and the I(2) was 49%. Subgroup analysis of women who had had a previous failed attempt at IVF found improved clinical pregnancy rates in the women undergoing AH compared with the women in the control group (9 RCTs, n = 1365; OR 1.42, 95% CI 1.11 to 1.81) with I(2) = 20%. Miscarriage rates per woman were similar in both groups (14 RCTs; OR 1.03, 95% CI 0.69 to 1.54, P = 0.90, moderate quality evidence). Multiple pregnancy rates per woman were significantly increased in women who were randomised to AH compared with women in the control groups (14 RCTs, 3447 women; OR 1.38, 95% CI 1.11 to 1.70, P = 0.004, low quality evidence).

AUTHORS' CONCLUSIONS

This update has demonstrated that whilst assisted hatching (AH) does appear to offer a significantly increased chance of achieving a clinical pregnancy, the extent to which it may do so only just reaches statistical significance. The 'take home' baby rate was still not proven to be increased by AH. The included trials provided insufficient data to investigate the impact of AH on several important outcomes. Most trials still failed to report on live birth rates.

High doses of medroxyprogesterone as the cause of disappearance of adherence of the zona pellucida to an oocyte

The zona pellucida (ZP) is an external glycoprotein membrane of oocytes of mammals and embryos in the early stage of their development. ZP first appears in growing ovarian follicles as an extracellular substance between the oocyte and granular cells. The zona pellucid markedly affects the development and maturation of the oocyte. The morphology of the ZP-oocyte complex allows a more precise determination of the oocyte maturity. According to numerous experimental studies, ZP is essential for preimplantation embryonic development of humans and other mammals. It prevents dispersion of blastomeres and enhances their mutual interactions. ZP is a dynamic structure responsible for the provision of nutrients to early forms of oocytes in mammals. The aim of the present study was untrastructural evaluation of the ZP-oocyte contact during inhibited ovulation. Female white rats (Wistar strain) received a suspension of medroxyprogesterone acetate (MPA) in incremental intramuscular bolus doses of 3.7 mg (therapeutic dose), 7.4 mg and 11.1 mg. The animals were decapitated 5 days after the administration of MPA. Ovarian sections were evaluated under a transmission electron microscope (TEM) Zeiss EM 900. Morphometric analysis of ZP was conducted using the cell imaging system by Olympus. In females exposed to therapeutic doses of MPA, ZP showed the structure of granular-fibrous reticulum of a medium electron density with single cytoplasmic processes originating from the surrounding structures. The oocyte cell membrane generated single, delicate processes directed toward ZP. Microvilli of the oocyte were short and thin. In the group receiving 7.4 mg of MPA, ZP had the structure of a delicate, loose granular-fibrous reticulum, and the oocyte cell membrane generated single microvilli directed toward ZP. In both those groups, the close ZP-oocyte contact was observed. Otherwise, in the group exposed to the highest MPA doses (11.1 mg), thicker and more numerous oocyte microvilli were found, which did not penetrate ZP matrix. They were dense, irregularly separated contour, forming a barrier between ZP and oocyte. The present findings are likely to suggest that MPA has inhibiting effects on the synthesis of binding proteins and causes the loss of the oocyte contact with ZP.

Zona-free embryo culture: is it a viable option to improve pregnancy rates?

Sporadic reports published during the previous decade have documented pregnancies achieved with transfer of zona-free human embryos. Although the overall efficiency seems to be good and some authors have suggested systematic application for special infertility problems, there have been only a few attempts to compare the benefits of zona-free embryo culture and transfer with the traditional approach using zona-intact embryos. So far, the majority of instances in which zona-free culture has been applied have occurred accidentally. This review summarizes the known functions of the zona pellucida, analyses natural and artificial situations where its function is compromised, including zona hardening and difficult hatching that seem to be related to in-vitro embryo culture, and discusses possible methods and timing for artificial zona removal. With the availability of in-vitro systems capable of replacing important functions of the zona pellucida, routine use of zona-free culture for the whole in-vitro period, after or even before fertilization, is a realistic possibility with potential additional benefits. Based on the increasing amount of animal studies, a systematic comparison is suggested that may eventually diminish the handicaps of the in-vitro situation and lead to simplification of manipulations as well as higher success rates after embryo transfer.

Assisted hatching on assisted conception (IVF and ICSI)

BACKGROUND

Failure of implantation and conception may result from an inability of the blastocyst to escape from its outer coat, known as the zona pellucida. Artificial disruption of this coat is known as assisted hatching (AH) and has been proposed as a method for improving the success of assisted conception.

OBJECTIVES

To determine whether assisted hatching (AH) of embryos facilitates live births and clinical pregnancy.

SEARCH STRATEGY

We previously searched the Cochrane Menstrual Disorders and Subfertility Group Specialsed Register (February 2007), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2007), MEDLINE (1966 to February 2007) and EMBASE (1980 to February 2007).

SELECTION CRITERIA

Two authors identified and independently screened trials. We included randomised controlled trials (RCTs) of AH (mechanical, chemical or laser disruption of the zona pellucida prior to embryo replacement) versus no AH, which reported live birth or clinical pregnancy rates.

DATA COLLECTION AND ANALYSIS

Two authors independently performed qualitative assessments and data extraction.

MAIN RESULTS

Twenty-eight trials reported clinical pregnancy data, including 1228 clinical pregnancies in 3646 women. There was no significant difference in the odds of live births in the AH compared with control groups (seven RCTs; OR 1.13, 95% CI 0.83 to 1.55; 255 births from 719 women, with no heterogeneity (P = 0.37) or inconsistency I(2) = 8%)). We also analysed the clinical pregnancy rate from the seven studies that reported live births, which was non-significant (OR 1.13, 95% CI 0.83 to 1.54). Inclusion of studies which were more robust in methodology showed an increase in clinical pregnancy rate which was just statistically significant (16 RCTs; OR 1.20, 95% CI 1.00 to 1.45, P = 0.05). Analysis of all the studies included in this update (28 RCTs) showed a marked increase in clinical pregnancy rate (OR 1.29, 95% CI 1.12 to 1.49).Miscarriage rates per women were similar in both groups (14 RCTs; OR 1.13, 95% CI 0.74 to 1.73). Multiple pregnancy rates per woman were significantly increased in women who were randomised to AH compared with women in control groups (12 RCTs; OR 1.67, 95% CI 1.24 to 2.26).

AUTHORS' CONCLUSIONS

The improvement in clinical pregnancy rate (CPR) with AH means that a clinic with a success rate of 25% could anticipate improving the CPR to between 29% and 49%, all things being equal. The included trials provided insufficient data to investigate the impact of assisted hatching on several important outcomes.

The antibody against a nuclear autoantigenic sperm protein can result in reproductive failure

To study whether the antibody against the testis form of the nuclear autoantigenic sperm protein (tNASP) could result in reproductive failure, we successfully cloned and expressed a 339-bp cDNA fragment of mouse tNASP (mtNASP). Using mouse as a model, recombinant mtNASP (rmtNASP) and a synthetic peptide, human tNASP(393-408) (htNASP(393-408)), were investigated for their antifertility effect. Active immunization with rmtNASP or the synthesized peptide raised high antibody titers in the immunized mice. Sperm-egg binding and fusion assay were carried out in 8-10-week-old BALB/c mice. Sperm-egg binding and in vitro fertilization of mouse oocytes were inhibited by co-incubation of zona-free mouse oocytes with capacitated mouse spermatozoa in the presence of varying concentrations of the antisera against rmtNASP. There was a significant antifertility effect in animals immunized with rmtNASP or the synthesized peptide. The effect on fertility in the mice immunized with the synthesized peptide was reversible. Our data indicate that active immunization with rmtNASP antigen may induce a strong antibody response that causes an inhibition of fertility.

Zona-free versus laser zona-assisted hatching blastocyst transfer: a comparison of outcomes

In unselected IVF patients, zona-free and laser zona-assisted hatching produced a comparable effect on blastocyst transfer.

Beneficial effect of long zona dissection on frozen-thawed blastocysts at a young age

Aim:  To assess the appropriateness of assisted hatching using long zona dissection of human frozen-thawed blastocysts at the time of warming, especially in women over 35 years of age or with repeated implantation failures. Methods:  Of 177 frozen-thawed blastocyst transfer cycles, 89 control cycles had an intact zona and 88 cycles had assisted hatching using long zona dissection of human thawed blastocyst at the time of warming. These two groups were further subdivided by age to a total of four subgroups: ≤34 years (assisted hatching, n = 39; controls, n = 39) and ≥35 years (assisted hatching, n = 49; controls, n = 50). Twenty-seven cycles in the control group and 28 cycles in the assisted-hatching group had repeated implantation failures. The clinical and ongoing pregnancy rates and the implantation rate between the two groups were analyzed retrospectively. Results:  The clinical pregnancy and implantation rates in women ≤34 years were significantly higher after the application of assisted hatching compared with the control group (87.2% and 71.2%vs 56.4% and 46.6%, P < 0.001). The clinical pregnancy and implantation rates of women with repeated implantation failures were higher after the application of assisted hatching compared with the control group (64.3% and 46.3%vs 48.1% and 34.1%), but this difference was not statistically significant. Conclusions:  Routine assisted hatching using long zona dissection at the time of warming on frozen-thawed blastocysts is a safe and easy method to perform and is extremely beneficial for increasing the pregnancy rate in young women ≤34 years of age, but not in women ≥35 years of age. Despite increased pregnancy and implantation rates in patients with repeated implantation failures, statistical significance was not achieved. (Reprod Med Biol 2007; 6: 211-218).

Second cycle: to hatch or not to hatch?

The objective of this study was to assess the impact of assisted hatching (AH) on pregnancy rate (PR), clinical pregnancy rate (CPR), and implantation rate (IR) after a single failed, fresh, nondonor IVF cycle. Accordingly, we report that patients with one prior implantation failure benefit from AH with improved PR, CPR, and IR in a subsequent cycle.

Chemical removal of zona pellucida versus laser assisted hatching after repeated failures of assisted reproductive technology

Background and Aims:  To evaluate outcomes after zona pellucida removal by pronase or laser assisted hatching in women with repeated assisted reproduction failures. Methods:  Of 389 procedures (January 2004 to November 2005), 203 control cycles had an intact zona, 116 cycles had chemical removal of the zona and 70 cycles had laser assisted hatching. Rates of pregnancy, implantation and abortion were compared, and pregnancy rate was secondarily evaluated for fresh or frozen-thawed blastocysts. Results:  Pregnancy rates were 33.5% (68/203) for controls, 29.3% (34/116) for chemical removal and 30.0% (21/70) for laser. Implantation rates were 24.8% (68/274) for controls, 21.8% (34/156) for chemical removal and 30.0% (21/105) for laser. There were no significant differences among groups. Abortion rates were 15.6% (10/64) for controls, 13.9% (5/36) for chemical removal and 14.3% (3/21) for laser. No difference was observed by blastocyst type for control or laser assisted hatching cycles. In the chemical removal group, both pregnancy and implantation rates were higher for frozen-thawed blastocysts than for fresh blastocysts. (41.5%vs 13.2% and 30.7%vs 11.1%, respectively). Conclusions:  Assisted hatching did not show a significant benefit. Chemical zona pellucida removal might increase pregnancy rates for frozen-thawed blastocysts. (Reprod Med Biol 2006; 5: 263-267).

Assisted hatching on assisted conception (IVF & ICSI)

BACKGROUND

Failure of implantation and conception may result from an inability of the blastocyst to escape from its outer coat, know as the zona pellucida. In vitro culture conditions and/or advancing maternal age may alter the architecture of the zona pellucida and result in hatching difficulties. Artificial disruption of this coat is known as assisted hatching (AH) has been proposed as a method of improving the success of assisted conception.

OBJECTIVES

To determine whether assisted hatching (AH) of embryos facilitates live births and clinical pregnancy and whether it impacts on negative outcomes (such as multiple pregnancy and miscarriage).

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group trials register (1 June 2005), the Cochrane Controlled Trials Register (Cochrane Library Issue 2, 2005), MEDLINE (1996 to June 2003), EMBASE (1980 to June 2005) and reference lists of articles. Authors were contacted for missing and/or unpublished data.

SELECTION CRITERIA

Trials were identified and independently screened by two reviewers. Randomised controlled trials of AH (mechanical, chemical or laser disruption of the zona pellucida prior to embryo replacement) versus no AH that reported live birth, clinical pregnancy or implantation rates were included.

DATA COLLECTION AND ANALYSIS

Qualitative assessments and data extraction were performed independently by two reviewers. Outcomes were extracted as rates and combined using random effects meta-analysis, sensitivity analysis, sub grouping and meta-regression where appropriate.

MAIN RESULTS

Twenty-three randomised controlled trials consisting of 2668 women reported on 849 pregnancy outcomes. There was no significant difference in the odds of live births in the AH compared with control groups (6 RCTs; OR 1.19 95% CI 0.81 to 1.73; 163 births from 516 women). Women undergoing assisted hatching were significantly more likely to achieve clinical pregnancy (23 RCTs, OR 1.33, 95% CI 1.12 to 1.57). Miscarriage rates per woman were similar in both groups (12 RCTs OR 1.23 (95% CI 0.73 to 2.05). Multiple pregnancy rates per woman was increased in women who were randomised to AH compared with control women (9 RCTs OR 1.83 (95% CI 1.19 to 2.83). The improvement in clinical pregnancy rate means for a clinic with a success rate of 25% could anticipate improving the CPR to between 28 and 39%, all things being equal. The trials provided insufficient data to investigate the impact of assisted hatching on several important outcomes, including monozygotic twinning, embryo damage, congenital and chromosomal abnormalities, and in vitro blastocyst development.

AUTHORS' CONCLUSIONS

Despite significantly improved odds of clinical pregnancy, there is insufficient evidence to determine any effect of AH on live birth rates. The increased multiple pregnancy rate is of concern although it likely that with a policy of single embryo transfer this may be lowered. Currently, there is insufficient evidence to recommend assisted hatching.

Hand-made cloning approach: potentials and limitations

Two major drawbacks hamper the advancement of somatic cell nuclear transfer in domestic animals. The first is a biological problem that has been studied extensively by many scientists and from many viewpoints, including the cell, molecular and developmental biology, morphology, biochemistry and tissue culture. The second is a technical problem that may be responsible for 50% or more of quantitative and/or qualitative failures of routine cloning experiments and is partially the result of the demanding and complicated procedure. However, even the relatively rare documented efforts focusing on technique are usually restricted to details and accept the principles of the micromanipulator-based approach, with its inherent limitations. Over the past decade, a small alternative group of procedures, called hand-made cloning (HMC), has emerged that has the common feature of removal of the zona pellucida prior to enucleation and fusion, resulting in a limited (or no) requirement for micromanipulators. The benefits of HMC are low equipment costs, a simple and rapid procedure and an in vitro efficiency comparable with or higher than that of traditional nuclear transfer. Embryos created by the zona-free techniques can be cryopreserved and, although data are still sparse, are capable of establishing pregnancies and resulting in the birth of calves. Hand-made cloning may also open the way to partial or full automation of somatic cell nuclear transfer. Consequently, the zona- and micromanipulator-free approach may become a useful alternative to traditional cloning, either in special situations or generally for the standardisation and widespread application of somatic cell nuclear transfer.

Efficacy of blastocyst transfer after implantation failure

Clinicians who treat unsuccessful couples despite repeated transfers of good quality embryos face a challenge. Among the various strategies that have been described, embryo transfer at the blastocyst stage has been postulated to improve implantation. A prospective non-randomized analysis was performed in 276 IVF patients who failed to conceive after at least two early embryo transfers of at least two grade 1-2 embryos per cycle. For the next attempt, couples chose between day 2 embryo transfer (D2 group; n = 147) and day 5/6 blastocyst transfer (D5/D6 group; n = 129) before starting the following attempt. Embryo quality was assessed and results were expressed as clinical pregnancy, live birth and implantation rates per cycle. Embryo grade 1 number was similar between both groups, whereas mean embryo score of the whole cohort was slightly higher in the D2 group. The live birth rates per cycle (27.9 versus 19.7%) and implantation rates per cycle (25.4 versus 12.4%) were higher in the D5/D6 group compared with the D2 group. Improved embryo selection and uterine receptivity may explain the additional benefit of embryo transfer at the blastocyst stage for couples with repeated implantation failures.

A Comparison of Established and New Approaches in Ovine and Bovine Nuclear Transfer

Several breakthroughs in nuclear transfer research were first achieved in sheep, although cattle soon became the main livestock species of interest. However, sheep still offer significant advantages both in basic and applied research. With increased interest in cloning of livestock, new approaches have been developed for both sheep and cattle nuclear transfer technology. These include methods for zona-free nuclear transfer that can be performed with or without the use of micromanipulator. Here we describe four different nuclear transfer methods including the traditional micromanipulation-assisted method in sheep, zona-free method in sheep in which the order of enucleation and nucleus delivery have been reversed ("reverse-order" cloning) and zona free manual cloning methods ("hand-made cloning") for embryonic and somatic cloning in cattle. The purpose of this paper is to encourage people to familiarize themselves with these different methods available and to help them choose and test the method most suitable for their particular circumstances.