Efficiency of laser-assisted intracytoplasmic sperm injection in a human assisted reproductive techniques program

A brief history of technical developments in intracytoplasmic sperm injection (ICSI). Dedicated to the memory of J.M. Cummins

Intracytoplasmic sperm injection (ICSI) is an assisted reproductive technology for treatment of severe male infertility introduced into clinical practice in 1992. This review provides a brief history of the development of ICSI by acknowledging major developments in the field. The review addresses key developments in pre-clinical and early studies, how ICSI compares with in vitro fertilisation, long-term consequences, how the mechanistic approach to ICSI has changed in both manual and semi-automated approaches, and how sperm selection procedures are integrated into ICSI. From the beginnings using animal models in the 1960-1970s, the development of ICSI is a remarkable and transformative success story. Indeed, its broad use (70% of cycles globally) exceeds the need required for treating infertile males, and this remains a controversial issue. There remain questions around the long-term health impacts of ICSI. Furthermore, advances in automation of the ICSI procedure are occurring. An estimated 6million children have been born from the ICSI procedure. With further automation of sperm selection technologies, coupled with automation of the injection procedure, it is likely that the proportion of children born from ICSI will further increase.

From Zygote to Blastocyst: Application of Ultrashort Lasers in the Field of Assisted Reproduction and Developmental Biology

Although the use of lasers in medical diagnosis and therapies, as well as in fundamental biomedical research is now almost routine, advanced laser sources and new laser-based methods continue to emerge. Due to the unique ability of ultrashort laser pulses to deposit energy into a microscopic volume in the bulk of a transparent material without disrupting the surrounding tissues, the ultrashort laser-based microsurgery of cells and subcellular components within structurally complex and fragile specimens such as embryos is becoming an important tool in developmental biology and reproductive medicine. In this review, we discuss the mechanisms of ultrashort laser pulse interaction with the matter, advantages of their application for oocyte and preimplantation embryo microsurgery (e.g., for oocyte/blastomere enucleation and embryonic cell fusion), as well as for nonlinear optical microscopy for studying the dynamics of embryonic development and embryo quality assessment. Moreover, we focus on ultrashort laser-based approaches and techniques that are increasingly being applied in the fundamental research and have the potential for successful translation into the IVF (in vitro fertilization) clinics, such as laser-mediated individual embryo labelling and controlled laser-assisted hatching.

A randomized controlled trial of laser-assisted ICSI

STUDY QUESTION

Does the use of a laser to open the zona pellucida during ICSI (laser assisted or LA-ICSI) improve oocyte survival, embryo development and clinical outcomes?

SUMMARY ANSWER

Compared to conventional ICSI, LA-ICSI increased rates of oocyte survival and some aspects of embryo development but it did not alter the ongoing pregnancy rate; after adjusting for oocyte survival, there was no beneficial effect of LA-ICSI on embryo development and utilization.

WHAT IS KNOWN ALREADY

Oocyte degeneration occurs in a 10th of mature oocytes after ICSI. Pilot studies suggest that LA-ICSI may improve oocyte survivability.

STUDY DESIGN, SIZE, DURATION

In a randomized controlled trial, 966 couples (16 122 metaphase II oocytes) were allocated to receive LA-ICSI (intervention) or conventional ICSI (control) between 17 September 2018 and 5 August 2019. Oocyte survival (primary endpoint), embryo development and ongoing pregnancy rates were compared.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Couples included in this study were recommended for ICSI due to female or male factor, unexplained infertility or a combination of factors. Patients were ineligible to participate in the study if they had uterine abnormality including thin endometrium, recurrent pregnancy loss, endometriosis or a severe medical condition. Concealed randomization to LA-ICSI or conventional ICSI, allocated in a 1:1 ratio, took place on stimulation Day 1 with replacement of blastocysts on only Day 5. The primary endpoint was oocyte survival with membrane integrity 24 h after the ICSI procedure. The sample size was estimated to detect a 3% increase in oocyte survival after LA-ICSI with 99% power at a 1% significance level. This also permitted the detection of 10% increase in ongoing pregnancy rate after LA-ICSI with 85% power at 5% alpha level. We used Poisson regression with zero-inflation for count data to estimate relative risk (RR) with 95% CI and logistic regression for clinical outcomes to estimate odds ratio (OR) with 95% CI. Both models adjusted for age as a covariate.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared with conventional ICSI, LA-ICSI resulted in a higher number of surviving oocytes (RR 1.08, 95% CI 1.05-1.12, P < 0.001), as well as a higher number of fertilized oocytes (RR 1.08, 95% CI 1.04-1.13, P < 0.001) and utilizable blastocysts (RR 1.09, 95% CI 1.04-1.15, P < 0.001). Sensitivity analyses adjusted for oocyte survival showed no between-group difference in utilizable blastocysts (OR 1.01, 95% CI 0.95-1.08, P = 0.73) and by calculating the mean rate, a reduction in utilizable blastocysts was shown (RR 0.95, 95% CI 0.94-0.97, P < 0.001). Ongoing pregnancy showed no between-group difference (LA-ICSI 179/489 (37%) vs ICSI 201/477 (42%), OR 0.79, 95% CI 0.61-1.03, P = 0.09).

LIMITATIONS, REASONS FOR CAUTION

It was not possible to blind the embryologists involved in the ICSI procedure. However, there was concealment of randomization and blinding of outcome assessments reducing the risk of selection and measurement bias.

WIDER IMPLICATIONS OF THE FINDINGS

A beneficial effect of LA-ICSI on oocyte survival should be shown to improve clinical outcomes, before its use in clinical practice is justified.

STUDY FUNDING/COMPETING INTEREST(S)

The study received no funding, and the authors declare that there are no conflicts of interest.

TRIAL REGISTRATION NUMBER

NCT03665103.

TRIAL REGISTRATION DATE

11 September 2018.

DATE OF FIRST PATIENT'S ENROLMENT

17 September 2018.

Controlled hatching at the prescribed site using femtosecond laser for zona pellucida drilling at the early blastocyst stage

PURPOSE

To study whether the application of femtosecond laser pulses for zona pellucida (ZP) drilling of blastocysts at the embryonic or abembryonic poles can promote hatching to start immediately through the hole formed and ensure high hatching rates and embryo viability.

METHODS

Mouse blastocyst (E3.5) ZP were microdissected with femtosecond laser pulses (514-nm wavelength, 280-fs pulse duration, 2.5-kHz repetition rate) close to the trophoblast or inner cell mass (ICM). The sizes of the holes formed were in the range of 4.5-8.5 μm. Additional longitudinal incisions (5-7-μm long) on either side of the hole were created to determine whether hatching had started at the correct position. Embryos post-laser-assisted ZP drilling and intact embryos were cultured under standard conditions for 2 days; embryo quality was assessed twice daily. The hatching rates and in vitro and in vivo implantation rates (only for embryos with ZP dissected close to the ICM) were estimated.

RESULTS

Femtosecond laser-assisted ZP drilling at the early blastocyst stage facilitated embryo hatching to start at the artificial opening with probability approaching 100%. Despite the artificial opening's small size, no embryo trapping during hatching was observed. Both experimental groups had higher hatching rates than the control groups (93.3-94.7% vs. 83.3-85.7%, respectively). The in vitro implantation rate was comparable with that of the control group (92.3% vs. 95.4%). No statistically significant differences were obtained in the in vivo implantation rates between the experimental and control groups.

CONCLUSIONS

Blastocyst-stage femtosecond laser microsurgery of ZP is fast and delicate and enables the hatching process to be initiated in a controlled manner through a relatively small opening, with no embryo trapping.

Oocyte Degeneration After ICSI Is Not an Indicator of Live Birth in Young Women

INTRODUCTION

Intracytoplasmic sperm injection (ICSI) was introduced in 1990s as one of the most dramatic breakthroughs in assisted reproductive technology. Even with advances in ICSI technology, this mechanical micromanipulation carries a 5 to 19% risk of oocyte degeneration. Whether the presence of oocyte degeneration reflects the sibling oocyte quality and predicts the sibling embryo development potential and clinical pregnancy outcomes remains controversial. There is no study showing the competence of the sibling embryos from the prospective of cumulative live birth rate. Whether oocyte degeneration is associated with poor quality of the remainder of the cohort remains further to be elucidated.

METHOD

This retrospective observational study included a total of 488 OPU cycles underwent ICSI with fresh cleavage stage embryo transfer and successive frozen/thawed embryo transfer (FET) cycles from January 2018 to December 2019. All female patients were under the age of 35 years, and underwent ICSI with or without oocyte degeneration (OD). Cycles with at least one oocyte degenerated were defined as oocyte degeneration group (OD group), and cycles with no oocyte degenerated were defined as non-OD group. The OD group was further divided to three subgroups according to different oocyte degeneration rate (<10%, 10-20%, and >20%).

RESULTS

There were no significant differences with regards to implantation rate (38.5% vs 35.1%, P=0.302), clinical pregnancy rate (54.9% vs 50.3%, P=0.340), and LBR per OPU cycle (47.0% vs 42.9%, P=0.395) between OD and non-OD groups. Initial gonadotropin dosage, E₂ level on hCG day and the number of matured oocytes appeared to be independent risk factors for OD. The adjusted odds ratio of live birth rate per OPU cycle were similar in different oocyte degeneration rate subgroups. The ongoing pregnancy/LBR per transfer in FET cycles was not significantly different between OD group and non-OD groups (38.8% vs 43.9%, P=0.439). The cumulative LBR per OPU cycle was also comparable between OD and non-OD group (63.4% vs 64.8%, P=0.760).

CONCLUSION

The results provide cycle-based evidence that the presence of oocyte degeneration after ICSI is not an indicator for predicting the cumulative live birth rate per OPU cycle in young women.

The effect of ICSI in infertility couples with non-male factor: a systematic review and meta-analysis

PURPOSE

We performed a systematic review and meta-analysis of available literature to investigate the efficacy of the intracytoplasmic sperm injection (ICSI) in couples with non-male factor with respect to the clinical outcomes.

METHODS

The literature search was based on EMBASE, PubMed, and the Cochrane Library. All studies published after 1992 until February 2020 and written in English addressing patients in the presence of normal semen parameters subjected to ICSI and in vitro fertilization (IVF) were eligible. Reference lists of retrieved articles were hand-searched for additional studies. The primary outcomes were fertilization rate, clinical pregnancy rate, and implantation rate; the secondary outcomes were good-quality embryo rate, miscarriage rate, and live birth rate.

RESULTS

Four RCTs and twenty-two cohort studies fulfilling the inclusion criteria were included. Collectively, a meta-analysis of the outcomes in RCTs showed that compared to IVF, ICSI has no obvious advantage in fertilization rate (RR = 1.16, 95% CI: 0.83-1.62), clinical pregnancy rate (RR = 1.04, 95% CI: 0.66-1.64), implantation rate (RR = 1.12, 95% CI: 0.67-1.86), and live birth rate (RR = 1.17, 95% CI: 0.43-3.15). Pooled results of cohort studies demonstrated a statistically significant higher fertilization rate (RR = 1.16, 95% CI: 1.03-1.31) and miscarriage rate (RR = 1.04, 95% CI: 1.01-1.06) in the ICSI group; furthermore, higher clinical pregnancy rate (RR = 0.85, 95% CI: 0.77-0.94), implantation rate (RR = 0.78, 95% CI: 0.65-0.95), and live birth rate (RR = 0.86, 95% CI: 0.79-0.94) was founded in the IVF group; no statistically significant difference was observed in good-quality embryo rate (RR = 0.98, 95% CI: 0.93-1.04).

CONCLUSION

ICSI has no obvious advantage in patients with normal semen parameters. Enough information is still not available to prove the efficacy of ICSI in couples with non-male factor infertility comparing to IVF.

Thoughts on the popularity of ICSI

Purpose

Intracytoplasmic sperm injection (ICSI) is the most widely utilized assisted reproductive technique (ART) worldwide. In this feature, we review the early assisted fertilization attempts that eventually led to the development of ICSI, and discuss its current utilization in cases of male and non-male factor infertility.

Methods

We researched the literature related to the development, indications, and current use of ICSI, such as sperm structural abnormalities, male genetic indications, surgically retrieved sperm, high sperm chromatin fragmentation, oocyte dysmorphism, and preimplantation genetic testing (PGT). We also describe the potential future applications of ICSI.

Results

This review summarizes the early micromanipulation techniques that led to the inception of ICSI. We also explore its current indications, including non-male factor infertility, where its use is more controversial. Finally, we consider the benefits of future advancements in reproductive biology that may incorporate ICSI, such as in vitro spermatogenesis, neogametogenesis, and heritable genome editing.

Conclusion

The versatility, consistency, and reliability of ICSI have made it the most prevalently utilized ART procedure worldwide.

Strategies to improve fertilisation rates with assisted conception: a systematic review

Successful fertilisation is one of the key steps determining success of assisted conception. Various factors including sperm or oocyte pathology and environmental factors have a significant impact on fertilisation rates. This systematic review is aimed to evaluate the existing evidence about factors affecting fertilisation and strategies to improve fertilisation rates. A literature search was performed using Ovid MEDLINE ® (Jan 1950-April 2016), EMBASE (Jan 1950-April 2016), Ovid OLDMEDLINE ®, Pre-MEDLINE (Jan 1950-April 2016) and the Cochrane Library. Relevant key words were used to combine sets of results and a total 243 papers were screened. Only qualitative analysis was performed, as there was major heterogeneity in study design and methodology for quantitative synthesis. Factors affecting fertilisation were divided into sperm- and oocyte-related factors. The methods to improve fertilisation rates were grouped together based on the approach used to improve fertilisation rates. Optimising laboratory condition and procedural effects in techniques is associated with improved fertilisation rates. Various techniques are described to improve fertilisation rates including assisted oocyte activation, physiological intracytoplasmic sperm injection (PICSI) and intracytoplasmic morphologically selected sperm injection (IMSI). This review highlights the promising strategies under research to enhance fertilisation rates. Adequately powered multicentre randomised trials are required to evaluate these techniques before considering clinical application.