Improved fertilization and implantation rates after non-touch zona pellucida microdrilling of mouse oocytes with a 1.48 microm diode laser beam

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.

Comparative study of fertilization rates of C57BL/6NKorl and C57BL/6N mice obtained from two other sources

C57BL/6N is the most widely used inbred mouse strain applied in a wide variety of research areas including cancer, cardiovascular biology, developmental biology, diabetes and obesity, genetics, immunology, neurobiology, and sensorineural research. To compare the fertilization rates of C57BL/6NKorl mice with two commercial C57BL/6N stocks, differences in reproductive organ structures, sperm and egg numbers, fertilization rates, and embryo development rates among C57BL/6NKorl (Korea FDA source), C57BL/6NA (USA source), and C57BL/6NB (Japan source) mice were determined. Among the stocks, no significant differences were detected in organ weight and histological structure of male and female reproductive organs, although body weight was higher in C57BL/6NKorl mice than that in the other groups. The concentration and morphology of sperm and eggs in C57BL/6NKorl mice were similar to those of C57BL/6NA and C57BL/6NB mice. Furthermore, the three stocks had similar in vitro fertilization and embryo development rates, although these rates tended to be higher in C57BL/6NB mice. Pup body weight was higher in C57BL/6NKorl and C57BL/6NB mice than that in C57BL/6NA mice. The results of the present study suggest that C57BL/6NKorl, C57BL/6NA, and C57BL/6NB mice obtained from three different sources have similar fertilization and embryo development rates, although there were slight differences in the magnitude of their responses rates.

Laser-assisted in vitro fertilization facilitates fertilization of vitrified-warmed C57BL/6 mouse oocytes with fresh and frozen-thawed spermatozoa, producing live pups

The utility of cryopreserved mouse gametes for reproduction of transgenic mice depends on development of assisted reproductive technologies, including vitrification of unfertilized mouse oocytes. Due to hardening of the zona pellucida, spermatozoa are often unable to penetrate vitrified-warmed (V-W) oocytes. Laser-assisted in vitro fertilization (LAIVF) facilitates fertilization by allowing easier penetration of spermatozoa through a perforation in the zona. We investigated the efficiency of V-W C57BL/6NTac oocytes drilled by the XYClone laser, compared to fresh oocytes. By using DAP213 for cryoprotection, 83% (1,470/1,762) of vitrified oocytes were recovered after warming and 78% were viable. Four groups were evaluated for two-cell embryo and live offspring efficiency: 1) LAIVF using V-W oocytes, 2) LAIVF using fresh oocytes, 3) conventional IVF using V-W oocytes and 4) conventional IVF using fresh oocytes. First, the groups were tested using fresh C57BL/6NTac spermatozoa (74% motile, 15 million/ml). LAIVF markedly improved the two-cell embryo efficiency using both V-W (76%, 229/298) and fresh oocytes (69%, 135/197), compared to conventional IVF (7%, 12/182; 6%, 14/235, respectively). Then, frozen-thawed C57BL/6NTac spermatozoa (35% motile, 15 million/ml) were used and LAIVF was again found to enhance fertilization efficiency, with two-cell embryo rates of 87% (298/343) using V-W oocytes (P<0.05, compared to fresh spermatozoa), and 73% (195/266) using fresh oocytes. Conventional IVF with frozen-thawed spermatozoa using V-W (6%, 10/168) and fresh (5%, 15/323) oocytes produced few two-cell embryos. Although live offspring efficiency following embryo transfer was greater with conventional IVF (35%, 18/51; LAIVF: 6%, 50/784), advantage was seen with LAIVF in live offspring obtained from total oocytes (5%, 50/1,010; conventional IVF: 2%, 18/908). Our results demonstrated that zona-drilled V-W mouse oocytes can be used for IVF procedures using both fresh and frozen-thawed spermatozoa, producing live pups. The ability to cryopreserve mouse gametes for LAIVF may facilitate management of large-scale transgenic mouse production facilities.

Safety, efficacy and efficiency of laser-assisted IVF in subfertile mutant mouse strains

In the present report we studied the safety, efficacy and efficiency of using an infrared laser to facilitate IVF by assessing fertilization, development and birth rates after laser-zona drilling (LZD) in 30 subfertile genetically modified (GM) mouse lines. We determined that LZD increased the fertilization rate four to ten times that of regular IVF, thus facilitating the derivation of 26 of 30 (86.7%) GM mouse lines. Cryopreserved two-cell stage embryos derived by LZD-assisted IVF were recovered and developed to blastocysts in vitro at the same rate as frozen-thawed embryos derived by regular IVF. Surprisingly after surgical transfer to pseudopregnant recipients the birth rate of embryos derived by LZD-assisted IVF was significantly lower than that of embryos derived by regular IVF. However this result could be completely mitigated by the addition of 0.25 M sucrose to the culture medium during LZD which caused the oocyte to shrink in volume relative to the perivitelline space. By increasing the distance from the laser target site on the zona pellucida, we hypothesize that the hyperosmotic effect of sucrose reduced the potential for laser-induced cytotoxic thermal damage to the underlying oocytes. With appropriate preparation and cautious application, our results indicate that LZD-assisted IVF is a safe, efficacious and efficient assisted reproductive technology for deriving mutant mouse lines with male factor infertility and subfertility caused by sperm-zona penetration defects.

Laser confers less embryo exposure than acid tyrode for embryo biopsy in preimplantation genetic diagnosis cycles: a randomized study

We compared two methods of zona pellucida drilling. 213 embryos were biopsied with acid Tyrode. Each biopsy took 3 minutes and the entire procedure ~29 minutes. 5% of blastomeres lysed, 49% of embryos became blastocyst and 36% of patients became pregnant. 229 embryos were biopsied with laser. Each biopsy took 30 seconds and the entire procedure ~7 minutes. 2.5% of blastomeres lysed, 50.6% of embryos became blastocyst and 47% of patients became pregnant. We can conclude that laser can be used for embryo biopsy. Reduction of embryo exposure and of removed blastomeres is associated with increased blastocysts available for transfer and a better clinical outcome.

Enhancement of IVF in the mouse by zona-drilling

Cryopreservation of mouse sperm has become an essential method for the long-term storage of novel, genetically modified mouse lines. Cryopreserved sperm from most hybrid lines can be effectively used for in vitro fertilization (IVF) of mouse oocytes. Unfortunately, IVF recovery with cryopreserved sperm from inbred lines is very inefficient. This is especially troublesome since many transgenic lines are created on the popular C57Bl/6 inbred strain. Cryopreserved sperm from C57Bl/6 inbred and genetically modified lines is generally very inefficient when used in standard IVF recovery experiments, with fertilization rates that can be lower than 10%. Assisted reproductive techniques have been developed to improve the IVF efficiencies of cryopreserved inbred sperm. These techniques include zona-drilling, which introduces a hole into the zona pellucida (ZP) surrounding mouse oocytes, using a chemical solution (acid Tyrode's), mechanical disruption (partial zona dissection or piezo-driven micropipette drilling), or laser photoablation. By allowing direct access of the sperm to the cytoplasmic membrane, zona-drilling can improve the efficiency of IVF fertilization rates with inbred sperm to greater than 90%, thus improving the chances of recovering mouse lines on inbred backgrounds that are maintained with cryopreserved sperm. The technique described in this chapter makes use of a piezo controller to mechanically disrupt the ZP, resulting in dramatic increases in the fertilization efficiency of cryopreserved sperm.

Engineering Approaches to Biomanipulation

This article presents a review on the existing techniques for manipulating biological cells. Because biomanipulation involves a wide range of disciplines, from biology to engineering, we concentrate on some of the key methodologies that would result in an efficient biomanipulation system. Some of the key methodologies discussed in this article for cell manipulation relate to the use of magnetics, microelectromechanical systems (MEMS)-based approaches, optics, electric field, and mechanical techniques. Recent advances in engineering have allowed researchers worldwide to address the problems arising from conventional manipulation techniques. This paper assimilates significance and limitations of biomanipulation techniques described in the literature.

A randomized, prospective study comparing laser-assisted hatching and assisted hatching using acidified medium

OBJECTIVE

To compare the clinical outcomes of patients whose transferred embryos underwent either laser-assisted hatching or hatching with acidified medium.

DESIGN

Randomized, prospective, double-blinded study.

SETTING

University-based IVF center.

PATIENT(S)

Clinical outcomes following IVF were compared in 159 patient cycles who randomly had all transferred embryos undergo laser-assisted hatching (Laser; n = 57) or hatching with acidified medium (Acid; n = 54). Patients whose embryos had zonae thickness <13 mum were not hatched (Thin; n = 8) and patients with > or =4 embryos at the 7- to 8-cell stage or higher on Day 3 were transferred on Day 5 (Day 5; n = 40).

MAIN OUTCOME MEASURE(S)

Implantation rates, clinical pregnancy rates, ongoing pregnancy rates, multiple pregnancy rates.

RESULT(S)

No significant differences were noted in clinical, ongoing, or multiple pregnancy rates between the four groups. The implantation rate for Day 5 transfers was significantly greater than both the Laser and Acid treatment groups.

CONCLUSION

The use of a 1.48-micron infrared diode laser beam provides a safe and rapid method for performing assisted hatching and did not have a negative impact on patient care when compared to outcomes achieved using acidified medium.

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).

Laser assisted hatching in good prognosis patients undergoing in vitro fertilization-embryo transfer: a randomized controlled trial

OBJECTIVE

To evaluate whether assisted hatching improves clinical outcomes of embryo transfers to good prognosis patients, defined as patients < or =39 years with normal follicle-stimulating hormone (FSH) and E(2) levels, no more than one previous unsuccessful cycle of in vitro fertilization (IVF)-embryo transfer, and good embryo quality.

DESIGN

Prospective randomized controlled trial.

SETTING

Private assisted reproductive technology (ART) center.

PATIENT(S)

One hundred ninety-nine good prognosis patients undergoing IVF-embryo transfer.

INTERVENTION(S)

In vitro fertilization followed by embryo transfer on day 3 after oocyte retrieval with or without assisted hatching using a 1,480-nm wavelength infrared laser.

MAIN OUTCOME MEASURE(S)

Clinical intrauterine pregnancy, spontaneous pregnancy loss, and live birth.

RESULT(S)

Rates of clinical intrauterine pregnancy with fetal cardiac activity (53% vs. 54% per cycle), spontaneous pregnancy loss (13% vs. 16% per pregnancy), and live birth (47% vs. 46% per cycle) were very similar between treatment cycles with laser-assisted hatching and control cycles in which embryos were transferred without assisted hatching. There were no significant differences between treatment and control groups in any measured clinical outcome parameters.

CONCLUSION(S)

Assisted hatching does not improve clinical outcomes among good prognosis patients.

Laser versus mechanical assisted hatching: a prospective study of clinical outcomes

OBJECTIVE

To compare clinical outcomes after laser or mechanical techniques of assisted hatching (AH) in women of advanced age undergoing IVF or intracytoplasmic sperm injection (ICSI).

DESIGN

Prospective randomized study.

SETTING

Center for Human Reproduction, Genesis Clinic, Athens, Greece.

PATIENTS

Three hundred and sixteen consenting women of advanced age (> or =39 years) with primary infertility undergoing IVF/ICSI programs and having available embryos for transfer on day 3. Patients were randomized into laser or mechanical AH of their transferred embryos.

INTERVENTIONS

Controlled ovarian hyperstimulation, oocyte retrieval, IVF/ICSI, laser or mechanical AH, and embryo-transfer.

MAIN OUTCOME MEASURES

Implantation rate, clinical pregnancy rate, and viable pregnancy rate.

RESULTS

The implantation rate was significantly higher in the laser AH group. Clinical and viable pregnancy rates were higher (but not significantly) in the laser AH group.

CONCLUSIONS

Laser AH of embryos may result in better clinical outcomes when compared to the mechanical technique in women of advanced age undergoing IVF or ICSI.

Screening oocytes by polar body biopsy

Preimplantation genetic aneuploidy screening performed by polar body biopsy has become a frequently used method, especially as in several countries only preconceptional genetic diagnosis is allowed. To penetrate the zona pellucida, mechanical, chemical and laser-assisted techniques have been introduced. In this paper, the advantages, disadvantages, efficacy and safety of these techniques are elucidated.

Evaluation of laser-assisted lentiviral transgenesis in bovine

Lentiviral transduction of oocytes or early embryos is an efficient strategy to generate transgenic rodents and livestock. We evaluated laser-based microdrilling (MD) of the zona pellucida, which is a physical barrier for viral infection, and subsequent incubation in virus suspension as a new route for lentiviral transgenesis in bovine. Lentiviral vectors carrying an eGFP expression cassette were used to transduce oocytes or zygotes after MD as compared to the established subzonal virus injection technique (MI). The type of manipulation (MD vs. MI) did not affect cleavage rates, but had a significant effect on blastocyst rates (P < 0.001). MI of virus or sham-MI (buffer) resulted in higher blastocyst rates as compared to MD, both in the oocyte and zygote treatment groups. The latter exhibited higher rates of early cleavage (P < 0.05) and blastocyst rates (P < 0.01). The proportion of eGFP expressing blastocysts was higher after infection of oocytes (MD: 44 +/- 9%; MI: 67 +/- 8%) than after infection of zygotes (MD: 26 +/- 8%; MI: 26 +/- 9%). Overall efficacy (eGFP-positive blastocysts per treated oocytes or zygotes) was highest after MI of oocytes (18 +/- 2%). Our study demonstrates the feasibility of laser-assisted lentiviral gene transfer into bovine oocytes and zygotes. However, further optimization of the procedure is required, mainly to reduce the incidence of polyspermy after MD of oocytes and to eliminate negative effects of MD on early embryonic development.

Risk assessment of mouse hepatitis virus infection via in vitro fertilization and embryo transfer by the use of zona-intact and laser-microdissected oocytes

The aim of this study was to estimate the risk of mouse hepatitis virus (MHV) transmission by the in vitro fertilization and embryo transfer (IVF-ET) procedure. In addition, resistance to infection of zona-intact and laser-microdissected oocytes was compared. For this purpose, infectious mouse hepatitis virus, a common viral pathogen in mouse facilities, was used. Oocytes having an intact or laser-microdissected zona pellucida were incubated for fertilization in media containing MHV-A59 and resulting embryos were transferred to the oviduct of specific pathogen-free (SPF) Swiss recipients. The oocytes were divided into three experimental groups: 1) zona-intact oocytes continuously exposed to MHV in fertilization (HTF), culture (KSOM), and embryo transfer (M2) media; 2) zona-intact oocytes exposed to MHV in HTF medium and transferred after a standard washing procedure with virus-free KSOM and M2; and 3) laser-microdissected oocytes exposed to MHV in HTF medium and transferred after a standard washing procedure with virus-free KSOM and M2. Respective serum samples of embryo recipients and their offspring were tested for MHV antibodies using ELISA. In experiment 1, 10 out of 14 embryo recipients seroconverted to MHV and only their offspring (8 of 19) received maternal antibodies. In experiments 2 and 3, MHV antibodies were detected neither in the recipients nor in the offspring. These results indicate, for the first time, that even if the zona pellucida is partially disrupted by laser microdissection, the transmission of MHV-A59 can be avoided by correctly performed washing steps in the IVF-ET procedure.

The role of aromatase inhibitors in ameliorating deleterious effects of ovarian stimulation on outcome of infertility treatment

Clinical utilization of ovulation stimulation to facilitate the ability of a couple to conceive has not only provided a valuable therapeutic approach, but has also yielded extensive information on the physiology of ovarian follicular recruitment, endometrial receptivity and early embryo competency. One of the consequences of the use of fertility enhancing agents for ovarian stimulation has been the creation of a hyperestrogenic state, which may influence each of these parameters. Use of aromatase inhibitors reduces hyperestrogenism inevitably attained during ovarian stimulation. In addition, the adjunct use of aromatase inhibitors during ovarian stimulation reduces amount of gonadotropins required for optimum stimulation. The unique approach of reducing hyperestrogenism, as well as lowering amount of gonadotropins without affecting the number of mature ovarian follicles is an exciting strategy that could result in improvement in the treatment outcome by ameliorating the deleterious effects of the ovarian stimulation on follicular development, endometrial receptivity, as well as oocyte and embryo quality.

Possible applications of a non-contact 1.48 μm wavelength diode laser in assisted reproduction technologies

Recently, one laser system has been introduced in IVF fulfilling all safety requirements, while achieving a high standard of reproducibility in terms of ablation diameter. This 1.48 microm wavelength indium-gallium-arsenic-phosphorus (InGaAsP) semiconductor laser offers a variety of laser applications to the embryologist. On the one hand, zona pellucida of oocytes or embryos can be manipulated in order to facilitate ICSI or biopsy and assist hatching, and on the other, spermatozoa may be paralysed or immobilized prior to usage. To conclude, the 1.48 microm diode laser provides a promising tool for the microdissection of subcellular targets. The diode laser stands out due to the rapidity, the simplicity and the safety of the procedure which is supported by healthy offspring after laser application.

Comparison of effects of zona drilling by non-contact infrared laser or acid Tyrode's on the development of human biopsied embryos as revealed by blastomere viability, cytoskeletal analysis and molecular cytogenetics

Use of a non-contact infrared laser (IRL) or acid Tyrode's for zona drilling before embryo biopsy was compared by assessing blastomere viability using various fluorescent markers or culture of the single biopsied blastomere, and, by cytoskeletal and molecular cytogenetic analysis of the biopsied embryos following culture to the blastocyst stage. There was no significant difference in the proportion of biopsied embryos that showed no damage in both the biopsied blastomere and in the remaining embryo (acid Tyrode's: 75% versus IRL: 68%), or in the proportion of single biopsied blastomeres that divided in culture (P > 0.05). However, single biopsied blastomeres from laser drilled embryos showed a greater tendency to form miniblastocysts. The proportion of laser or acid Tyrode's biopsied embryos that reached the blastocyst stage by day 6 was similar, although evident earlier (day 5) in the laser biopsied embryos. Spindle abnormalities at the blastocyst stage included tripolar and tetrapolar spindles, but their incidence was not significantly different from controls. In addition, no significant difference was observed in the incidence of chromosomal abnormalities and mosaicism between the two groups. It is concluded that using an IRL at a safe working distance does not cause adverse immediate or longer term effects on the development of human biopsied embryos, although damage can occur if drilling within this distance is unavoidable. Acid Tyrode's drilling can also cause damage, and tended to retard blastocyst development.

Hatching: How to Select the Clinical Indications

Currently, most fertility centers around the world use assisted hatching (AH) techniques to help embryo release out of the zona pellucida (ZP) and thus increase the implantation rate. For the last 13 years, several retrospective and prospective studies, assessing AH in different clinical indications, have given disparate results, making the selection of patients or embryos in need of this treatment complex. The most relevant conclusion obtained so far is that AH has a beneficial effect in women with repeated failures of embryo implantation. The place of AH in clinical practice in comparison with other approaches has to be reevaluated based on the selection of viable embryos using strict morphometric criteria and/or prolonged culture up to the blastocyst stage. Finally, the potential value of AH for indications other than repeated failure has to be weighed carefully to make sure that AH does not reduce the chances of implantation.

A European multicentre prospective randomized study to assess the use of assisted hatching with a diode laser and the benefit of an immunosuppressive/antibiotic treatment in different patient populations

BACKGROUND

Assisted hatching (AH) techniques, designed for facilitating the embryo escape out of the zona pellucida (ZP) have been used in IVF centres since 1992. The initial indications for AH were patient's age, ZP thickness, high basal FSH and repeated IVF failures. Several retrospective and prospective studies assessing AH in these indications have given disparate results. Our aims were to evaluate the benefits of AH and immunosuppressive/antibiotic treatment (IA) in patients with either a poor prognosis of success, previous implantation failures or transfers of cryopreserved embryos.

METHODS

Four IVF centres allocated 426 patients, randomized for AH and IA, into four groups of AH indications between 1997 and 1999. AH was performed with a diode laser. ZP thickness, opening size and embryo score were recorded. Outcome measures were implantation and delivery rates.

RESULTS

Patients coming for a first or third transfer of cryopreserved embryos and poor prognosis patients admitted for a first trial did not benefit from AH. Even patients with repeated implantation failures of fresh embryos did not gain significantly from AH.

CONCLUSIONS

Among AH indications, absence of implantation after several transfers of good quality embryos remains the strongest patient selection criterion. Prescription of an immunosuppressive/antibiotic treatment is essential.

Technical aspects of the piezo, laser-assisted, and conventional methods for nuclear transfer of mouse oocytes and their efficiency and efficacy: Piezo minimizes damage of the ooplasmic membrane at injection

Assessment of the advantages and disadvantages of the piezo, laser, and conventional methods for nuclear transfer has remained elusive. Furthermore, although the piezo method had been used by some investigators for research of sperm injection and nuclear transfer for several years, many researchers have failed to operate the technique smoothly and achieve reproducible results. The procedures of nuclear transfer using piezo were ascertained and described in detail. Mouse oocytes were enucleated, and injected with cumulus cells using the piezo, laser, or conventional methods. We investigated the time needed and survival of nuclear transfer. Development was compared among the three methods and parthenogenetic control specimens. The average time of nuclear transfer for each oocyte was significantly shorter using the piezo (118 +/- 9 s) and laser methods (120 +/- 11 s) than using the conventional method (170 +/- 11 s). The damage rate was smaller for the piezo group (10%) than the laser (37%) and conventional (40%) groups. The percentages of blastocyst formation (14%, 12%, and 11%) and the number of nuclei of blastocysts (54 +/- 13, 51 +/- 11, and 52 +/- 12) were similar among the piezo, laser, and conventional groups, but significantly lower than for the control group (83%, 105 +/- 14). The piezo technique is more efficient than the conventional method for nuclear transfer. The laser method is easy to operate, but the equipment is expensive. In addition, piezo induced fewer traumas while breaking the membrane than the aspiration techniques used in the laser and conventional methods.

Randomized controlled study of human zona pellucida dissection using the zona infrared laser optical system: evaluation of blastomere damage, embryo development, and subsequent hatching

OBJECTIVE

To assess the effect of laser hatching on human embryo damage and subsequent development using the Zona Infrared Laser Optical System (ZILOS).

DESIGN

Randomized controlled study.

SETTING

Tertiary care fertility clinic.

PATIENT(S)

One hundred fourteen donated and discarded frozen human embryos.

INTERVENTION(S)

Embryos were thawed, cultured with cleavage and morphology evaluated periodically, and randomized into control, partial hatching, or complete hatching groups. The laser hatching procedure was performed by ZILOS. Zona thickness and embryo diameter were recorded. Complete hatching involved the production of a full-thickness defect in the zona and partial hatching, a defect in the outer half of the zona. No laser treatment was administered to the control group.

MAIN OUTCOME MEASURE(S)

Blastocyst development and completion of hatching process.

RESULT(S)

No significant difference was noted between the three study groups for their baseline characteristics. There was no significant difference in blastocyst development among the three groups. However, the complete hatching group showed a significant increase in hatching compared to the control group.

CONCLUSION(S)

Complete laser hatching of human embryos using the ZILOS does not have an adverse effect on subsequent development and increases the rate of completion of hatching.

Birth of healthy children after preimplantation diagnosis of beta-thalassemia by whole-genome amplification

Preimplantation genetic diagnosis (PGD) offers couples at risk for transmitting an inherited disorder the possibility to avoid the need to terminate affected pregnancies. PGD for monogenic diseases is most commonly accomplished by blastomere biopsy from cleavage-stage embryos, followed by PCR-based DNA analysis. However, the molecular heterogeneity of many monogenic diseases requires a diagnostic strategy capable of detecting a range of mutations and compound genotypes. With the above considerations, we developed an accurate and reliable strategy for analysis of beta-globin gene mutations, applicable for PGD for the wide spectrum of beta-thalassemia major mutations in the Chinese population. The strategy involves primer-extension preamplification (PEP), followed by nested PCR and reverse dot blot (RDB) for mutation detection since it facilitates simultaneous analysis of more than one mutation in a single cell. This report describes the application of the strategy in two clinical IVF/PGD cycles at risk for transmitting beta-thalassemia major, which resulted in the first thalassemia-free children born after PGD in China.

Zona dissection by infrared laser: developmental consequences in the mouse, technical considerations, and controlled clinical trial

Infrared laser systems are currently being marketed for application in clinical zona pellucida dissection. However, these systems have undergone only limited animal testing and minor clinical trials that lacked proper controls. Two of these systems have been evaluated in protocols that addressed potential detrimental effects on embryonic development in the mouse. Exaggerated large openings were made in the zona pellucida of 8-16 cell mouse embryos. Embryonic development and subsequent implantation and viability were assessed. A definite negative effect on these parameters was observed following the use of one of these systems. Following this animal trial, the second system was evaluated in a clinical trial for assisted hatching and embryo biopsy. Laser dissection was directly compared with the standard zona drilling using acidified Tyrode's solution. While no significant difference was evident between the two protocols, it was felt that laser dissection presented some problems in both consistency between operators and in the efficacy of subsequent manipulations such as blastomere biopsy and fragment removal. These results argue that laser zona dissection is far from a simple technique and should be carefully evaluated before any clinical application is made.

Zona thinning with a noncontact diode laser in ICSI embryos from women of advanced age

PURPOSE

The objective of this study was to determine if the zona thinning (ZT) technique improved the rates of implantation and clinical pregnancy for patients aged > or = 38 years submitted to an ICSI program.

METHODS

A total of 100 patients submitted to ICSI and aged > or = 38 years were divided in a prospective and randomized manner into two groups: Group I - patients submitted to ZT (n = 50); a laser diode with 1.48 microm wavelength (Fertilaser) was used for the ZT procedure with 1-2 irradiations of 10 ms applied to four different positions on the zona pellucida (ZP) of each embryo to thin 60-90% of the ZP (each point with a 15-20 microm length of ZT). Group II - patients with no ZT (n = 50). In both groups, embryo transfer was performed on the second or third day.

RESULTS

The age of Group I patients (39.8 +/- 1.3) did not differ (p = 0.67) from that of Group II patients (40 +/- 1.9). The number of oocytes retrieved at metaphase II from Group I (6.4 +/- 4.2) and Group II (6.8 +/- 5) was similar (p = 0.94). Normal fertilization rates and cleavage rates were similar (p = 0.78 and p = 0.63, respectively) for Group I (71.5 +/- 22% and 96.7 +/- 11%) and Group II (73.5 +/- 19.7% and 96 +/- 11%, respectively). The number of embryos transferred was similar (p = 0.53) for the two groups (Group I = 3.1 +/- 1.3; Group II = 2.9 +/- 1.1). The thickness of the ZP of Group I embryos (16.9 +/- 2.4 microm) did not differ (p = 0.97) from that of Group II embryos (16.9 +/- 2.3 microm). The rates of embryo implantation and clinical pregnancy per embryo transfer were similar (p = 0.67, p = 0.61) for Group I (7 and 16%, respectively) and for Group II (8.2 and 22%, respectively).

CONCLUSIONS

These results suggest that ZT in the population aged > or = 38 years may have no impact on ICSI success rates. However, this conclusion is limited to a situation in which length of the laser ZT was < or = 20 microm and the laser was applied to four different positions.

Five years experiences with microinjection of testicular spermatozoa into oocytes in Hungary

The aim of the study was to summarize our five years experience (1996-2000) of testicular spermatozoa for intracytoplasmic sperm injection in Hungary. The influence of sperm count, maternal age, number of transferred embryos, and application of assisted hatching on outcome was investigated. Testicular spermatozoa were retrieved by microsurgical testicular sperm extraction. Samples were classified depending on the number of spermatozoa. Indication for testicular sperm extraction in conjunction with intracytoplasmic sperm injection was severe azoospermia or azoospermia combined with tubal origin infertility. Ovarian stimulation was carried out using an ultrashort protocol with GnRH agonist and gonadotrophin. Intracytoplasmic sperm injection was performed without PVP. Embryos were cultured for 48 or 72 h before embryo transfer. Indications for assisted hatching included elevated maternal age, increased zona thickness or at least two previous unsuccessful IVF cycles. Testicular spermatozoa were successfully retrieved in 218 out of 273 cases. Extreme low sperm count was found more frequently in cases of nonobstructive azoospermia. No significant differences were observed in fertilization rate (61.1% vs. 51.7%) or clinical pregnancy rate (29.0% vs. 26.7%) between patients with obstructive or nonobstructive azoospermia. Maternal age, number of transferred embryos and application of assisted hatching had a significant effect on outcome. A total of 55 clinical pregnancies were achieved, including 14 sets of twins, three sets of triplets and two sets of quadruplets. It is concluded that testicular sperm extraction is an efficient way of obtaining testicular spermatozoa, allowing not only successful fertilization by ICSI, but also freezing of testicular spermatozoa for use in subsequent cycles.

Laser-assisted hatching of embryos is better than the chemical method for enhancing the pregnancy rate in women with advanced age

OBJECTIVE

Assisted hatching may enhance embryo implantation. This study was conducted to examine the efficacy of the laser- and chemical-assisted hatching for promotion of implantation (IR), pregnancy (PR), and delivery rate (DR) in older women undergoing IVF cycles.

DESIGN

Prospective study.

SETTING

An IVF unit of a medical center.

PATIENT(S)

A total of 601 embryos from 141 women aged > or =38 years underwent controlled ovarian hyperstimulation (COH) and assisted hatching.

INTERVENTION(S)

The study population was divided into two groups: group 1 had laser-assisted hatching (n = 85) and group 2 had chemical-assisted hatching (n = 56). Before the transfer, the day 3 embryos were hatched by using a 1.48-microm noncontact diode laser or acid Tyrode's solution.

MAIN OUTCOME MEASUREMENT(S)

The IR, PR, and DR between the groups were compared.

RESULT(S)

There were no statistical differences between groups in age, E2 concentrations during hCG administration, gonadotrophin dosage, embryo grade, the numbers of oocytes retrieved, oocytes fertilized, and embryos transferred. Higher IR, PR, and DR were noted in the laser-assisted hatching group. The IR, PR, and DR were: group 1, 8.2%/31.8%/24.7% and group 2, 3.8%/16.1%/10.7%, respectively.

CONCLUSION(S)

Laser-assisted hatching of embryos is more effective than the chemical method in enhancing the IR and PR of women with advanced age. The laser system allows an easier, faster, and safer micromanipulation of the zona pellucida, which provided a better method in zona drilling.

Noncontact, laser-mediated extraction of polar bodies for prefertilization genetic diagnosis

PURPOSE

We tested an entirely noncontact polar body-extraction method using an ultraviolet laser beam for laser zona drilling and a near infrared laser beam for polar body (PB) trapping and extraction.

METHODS

A hole was drilled into the zona pellucida of an oocyte. Then, the PB was trapped with optical tweezers and dragged through the drilled hole.

RESULTS

Bovine first PBs could be extracted in 49 out of 63 oocytes (78%) using this method. In human oocytes, PB extraction was successfully demonstrated, which however was more time consuming. A number of extracted PBs were dried on a special membrane, circumcised with the laser microbeam, and successfully catapulted into the lid of a microfuge tube (laser pressure catapulting).

CONCLUSIONS

This solely laser-mediated extraction method allows convenient procurement of PBs without the danger of contamination and is a promising approach that might replace standard micromanipulation methods in the future.

Laser assisted immobilization of spermatozoa prior to intracytoplasmic sperm injection in humans

BACKGROUND

The conventional method of immobilization of spermatozoa prior to intracytoplasmic sperm injection (ICSI) is mechanical breakage of the tail by pressing it against the bottom of the injection dish.

METHODS

This prospective self-controlled study was set up to evaluate the potential of a non-contact 1.48 microm wavelength diode laser in terms of immobilization. In addition, the fertilization rate and further development potential of such zygotes were investigated. The patients included in our study (n = 60) had oestradiol concentrations >2000 pg/ml, and thus a relatively high number of MII oocytes could be expected. Approximately half the oocytes were injected with laser treated spermatozoa (n = 262, study group) and the other half with mechanically immobilized spermatozoa (n = 252, control group).

RESULTS

No significant differences between the two groups in terms of fertilization rate, early cleavage or blastocyst formation were observed. However, time required for identification, aspiration and injection of a potential spermatozoa was significantly shorter in the laser immobilized sperm group (P < 0.001).

CONCLUSIONS

The application of a non-contact diode laser for sperm immobilization prior to ICSI is a potentially useful alternative to the conventional mechanical approach.

A comparison between quarter, partial and total laser assisted hatching in selected infertility patients

BACKGROUND

The object of this study was to evaluate the efficacy of laser assisted hatching (LAH) of embryos on implantation and pregnancy rates of a selected group of infertility patients.

METHODS

A total of 322 cycles using LAH was undertaken in our Centre between June 1998 and September 1999. Patients were offered LAH if they fell in either one or more of the following categories: (i) Patients over 37 years of age undergoing either IVF or intracytoplasmic sperm injection (ICSI) treatment cycles; (ii) patients with more than 2 previous treatment cycle failures; (iii) patients undergoing frozen embryo replacement cycles and (iv) women who were considered to be poor responders. The initial results of totally breaching the zona pellucida (total LAH; group 1) did not meet with our expectations. We subsequently modified the technique to thinning one area of the zona pellucida (partial LAH; group 2) and this thinned area was then extended to a quarter segment (quarter LAH; group 3).

RESULTS

In group 1, the pregnancy rate was 14.6% with a clinical pregnancy rate of 5.2%. In group 2 the pregnancy rate was 20.9% with a clinical pregnancy rate of 18% and for patients in group 3 the pregnancy rate was 29.0% with a clinical pregnancy rate of 22.1%.

CONCLUSIONS

Overall there was firm statistical evidence that the pregnancy and clinical pregnancy rates arising from quarter LAH were higher in comparison with partial and total LAH.

Laser zona pellucida thinning--an alternative approach to assisted hatching

BACKGROUND

The purpose of this study was to assess the efficacy and hatching characteristics of in-vitro cultured human embryos subjected to laser zona pellucida thinning.

METHOD

Zona thinning was performed on 110 embryos using a non-contact 1.48 microm diode laser and the hatch rate in vitro was compared with 42 control embryos. Variation of zona thickness and degree of zona expansion was assessed. Scanning electron microscopy was performed on embryos entrapped during hatching to identify the site of hatching.

RESULTS

The rate of hatching was significantly higher in laser thinned blastocysts compared with control embryos (68 versus 33% respectively, P < 0.01). Laser thinning increased the variation of zona thickness in embryos from 11.6-27.3%. Natural zona thinning occurred in 92% of laser thinned hatching blastocysts and 100% of control embryos.

CONCLUSION

These results suggest that laser zona thinning is effective and may provide significant advantages over conventional assisted hatching techniques, which create holes.

Aspects of biopsy procedures prior to preimplantation genetic diagnosis

Today, preimplantation genetic diagnosis (PGD) is offered in over 40 centres worldwide for an expanded range of genetic defects causing disease. This very early form of prenatal diagnosis involves the detection of affected embryos by fluorescent in situ hybridization (FISH) (sex determination or chromosomal defects) or by polymerase chain reaction (PCR) (monogenic diseases) prior to implantation. Genetic analysis of the embryos involves the removal of some cellular mass from the embryos (one or two blastomeres at cleavage-stage or some extra-embryonic trophectoderm cells at the blastocyst stage) by means of an embryo biopsy procedure. Genetic analysis can also be performed preconceptionally by removal of the first polar body. However, additional information is then often gained by removal of the second polar body and/or a blastomere from the embryo. Removal of polar bodies or cellular material from embryos requires an opening in the zona pellucida, which can be created in a mechanical way (partial zona dissection) or chemical way (acidic Tyrode's solution). However, the more recent introduction of laser technology has facilitated this step enormously. Different biopsy procedures at different preimplantation stages are reviewed here, including their pros and cons and their clinical applications. The following aspects will also be discussed: safety of zona drilling by laser, use of Ca2+/Mg2+-free medium for decompaction, and removal of one or two cells from cleavage-stage embryos.

Islet-brain1/JNK-interacting protein-1 is required for early embryogenesis in mice

Islet-brain1/JNK-interacting protein-1 (IB1/JIP-1) is a scaffold protein that organizes the JNK, MKK7, and MLK1 to allow signaling specificity. Targeted disruption of the gene MAPK8IP1 encoding IB1/JIP-1 in mice led to embryonic death prior to blastocyst implantation. In culture, no IB1/JIP-1(-/-) embryos were identified indicating that accelerated cell death occurred during the first cell cycles. IB1/JIP-1 expression was detected in unfertilized oocytes, in spermatozoa, and in different stages of embryo development. Thus, despite the maternal and paternal transmission of the IB1/JIP-1 protein, early transcription of the MAPK8IP1 gene is required for the survival of the fertilized oocytes.

Thermal effects in laser-assisted pre-embryo zona drilling

Diode lasers [lambda=1480 nm] are used with in vitro fertilization to dissect the zona pellucida (shell) of pre-embryos. A focused laser beam is applied in vitro to form a channel or trench in the zona pellucida. The procedure is used to facilitate biopsy or as a promoter of embryo hatching. We present examples and measurements of zona pellucida ablation using animal models. In using the laser it is vital not to damage pre-embryo cells, e.g., by overheating. In order to define safe regimes we have derived some thermal side effects of zona pellucida removal. The temperature profile in the beam and vicinity is predicted as function of laser pulse duration and power. In a crossed-beam experiment a HeNe laser probe is used to detect the temperature-induced change in the refractive index of an aqueous solution, and estimate local thermal gradient. We find that the diode laser beam produces superheated water approaching 200 degrees C on the beam axis. Thermal histories during and following the laser pulse are given for regions in the neighborhood of the beam. We conclude that an optimum regime exists with pulse duration < or =5 ms and laser power approximately 100 mW.

Cryopreservation of mouse oocytes using a medium with low sodium content: effect of plunge temperature

The effect of various combinations of plunge temperature and thawing protocol on the survival and viability of mouse oocytes was examined. The oocytes were frozen either in a standard freezing medium (ETFM, embryo transfer freezing medium) or in a low-sodium, choline-based freezing medium (CJ2), with 1.5 M 1,2-propanediol and 0.1 M sucrose, and using a conventional slow cooling method. The criteria used to assess survival were morphological state after thawing (intact or lysed), ability to become fertilized, and ability to develop to the two-cell, morula, and blastocyst stage in vitro. Oocytes frozen in CJ2 and plunged into liquid nitrogen (LN(2)) from -10, -20, or -33 degrees C remained intact and developed to the blastocyst stage at significantly higher rates than oocytes frozen in ETFM. For oocytes plunged into LN(2) from -33 degrees C, very rapid thawing (10 s in 30 degrees C water) was more detrimental than rapid or slow thawing (holding in air at room temperature for 10 or 30 s, respectively, prior to submersion in water at 30 degrees C for 10 s). By contrast, oocytes plunged into LN(2) from -10 or -20 degrees C survived better when thawing was very rapid or rapid than when thawing was slow. With the current protocol CJ2 was very effective over a wide range of plunge temperatures (-20 to -33 degrees C), although the optimal thawing protocol depended on the particular plunge temperature. Over 90% of oocytes surviving after slow cooling in CJ2 to -33 degrees C could be plunged to -196 degrees C with little or no further damage.

Viable spermatozoa can be recovered from refrigerated mice up to 7 days after death

To develop a model for utilizing germ cells collected from dead animals, male mice were euthanized and refrigerated for various periods, and the viability of the epididymal spermatozoa was examined by in vitro fertilization, embryo culture, and embryo transfer. Higher proportions of fresh oocytes were fertilized when males had been stored at 4-6 or 8-10 degrees C than at 0 degrees C. By partially dissecting the zona of freshly ovulated oocytes, spermatozoa from ICR male mice could fertilize oocytes (21% fertilization rate) after being stored for 5 days at 4-6 degrees C, and spermatozoa from BDF1 male mice could fertilize oocytes (39%) after being stored for 7 days at 4-6 degrees C. The resulting two-cell embryos had the ability to develop into expanded blastocysts in culture (81-100%) and into live young after transfer (34-47%). With further refinement of this system, it should be applicable not only for rescuing valuable genetic variants in laboratory animals or livestock animals but also for wild species in the future.

Cryopreservation of unfertilized mouse oocytes: the effect of replacing sodium with choline in the freezing medium

Although embryo cryopreservation has become commonplace in many species, effective methods are not available for routine freezing of unfertilized eggs. Cryopreservation-induced damage may be caused by the high concentration of sodium ions in conventional freezing media. This study investigates the effect of a newly developed low-sodium choline-based medium (CJ2) on the ability of unfertilized, metaphase II mouse eggs to survive cryopreservation and develop to the blastocyst stage in vitro. Specifically, the effects of cooling to subzero temperatures, thawing rate, LN2 plunge temperature, and equilibration with a low-sodium medium prior to freezing are examined. In contrast to cooling to 23, 0, or -7.0 degreesC in a sodium-based freezing medium (ETFM), cooling in CJ2 had no significant negative effect on oocyte survival or development. Oocytes frozen in CJ2 survived plunging into LN2 from -10, -20, or -33 degreesC at significantly higher rates than oocytes frozen in ETFM. With the protocol used (1.5 M PrOH, 0.1 M sucrose, -0.3 C/min, plunging at -33 degreesC) rapid thawing by direct submersion in 30 degreesC water was more detrimental to oocyte survival than holding in air for 30 or 120 s prior to transfer to water. Equilibration of unfertilized oocytes with a low-sodium medium prior to cryopreservation in CJ2 significantly increased survival and blastocyst development. These results demonstrate that the high concentration of sodium in conventional freezing media is detrimental to oocyte cryopreservation and show that choline is a promising replacement. Reducing the sodium content of the freezing medium to a very low level or eliminating sodium altogether may allow oocytes and other cells to be frozen more effectively.

Detrimental effects of sodium during mouse oocyte cryopreservation

Cryopreservation is an established way of storing embryos, but effective methods are not available for freezing eggs. Most freezing damage is caused by high solute concentration (solution effects) and intracellular ice. Sodium salts are the major components of cryopreservation media, and the main contributor to the solution effects. The present experiments examine the effect of substituting choline for sodium as the major extracellular cation in the cryopreservation of mouse eggs. The effects of serum and various cryoprotectants were also examined. Survival, fertilization, and development were inversely related to the concentration of sodium in the freezing medium. Oocytes frozen in a choline-based medium had the highest (p < 0.001) survival and development rates. The absence of serum during thawing inhibited fertilization, whereas exposure to serum or opening the zona allowed fertilization to reach the control level. Dimethyl sulfoxide was as effective as 1,2 propanediol for obtaining high survival and fertilization rates. These results support the hypothesis that the high concentration of sodium in conventional freezing media is detrimental to cells and show that choline is a promising replacement for sodium. Reducing or eliminating sodium may allow oocytes and other cells to be frozen more efficiently.

Successful use of a laser for human embryo biopsy in preimplantation genetic diagnosis: report of two cases

PURPOSE

The use of Tyrode's acid to drill the zona pellucida for embryo biopsy is the most widely used methodology in preimplantation genetic diagnosis. Instead of this, we propose the use of a 1.48-micron diode noncontact laser, which is quicker, simpler, and safer.

METHODS

The laser beam was tangentially guided to the zona pellucida of the embryo. Depending on zona pellucida measurement, two to four consecutive shots of 8-22 msec were necessary to drill the zona pellucida of the 13 embryos biopsied for two patients (hemophilia carriers).

RESULTS

Female embryos were replaced into the uterus of the patients (1.5 embryos/replacement). One single pregnancy was established (33.3% implantation rate). Coculture of untransferable embryos showed a blastocyst rate of 66.7% (4/6) for male embryos and 25% (1/4) for abnormal ones.

CONCLUSIONS

These results demonstrate the safety and usefulness of laser methodology in preimplantation genetic diagnosis.

Laser blastocyst biopsy for preimplantation diagnosis in the human

A new methodology for blastocyst biopsy that uses a 1.48 microm diode laser is described. Trophectoderm cells are biopsied after laster zona drilling and culture, fixed and processed for fluorescent in situ hybridisation (FISH) analysis. Preliminary results on the efficiency of the procedure and blastocyst recovery rate are promising. Blastocyst laser biopsy is a useful tool in preimplantation genetic diagnosis (PGD) as it allows a more reliable diagnosis and widens the diagnostic possibilities on account of the higher number of cells obtained in the biopsy.