Rational approach to assisted fertilization

Evolution of intracytoplasmic sperm injection: From initial challenges to wider applications

Background

In vitro fertilization (IVF) has revolutionized infertility treatment. Nevertheless, male infertility requires more effective solutions. In 1992, the first-ever case of human birth via intracytoplasmic sperm injection (ICSI) was reported. ICSI involves microscopically injecting a sperm into an ovum. Successful ICSI has become a reliable therapy for couples facing infertility, a significant milestone. However, it has also introduced various challenges. This study also delves into ethical dilemmas arising from widespread ICSI use.

Methods

This review traces the history of ICSI, presenting pioneering attempts, first successful attempts, and critical reports on account of the initial skepticism toward the technology. The review also focuses on chronological progress until ICSI was recognized as effective and became widely applied.

Main findings

The review reveals that ICSI, although transformative, presents challenges. Successes include addressing male infertility and aiding fertilization. However, concerns arise regarding optimal sperm and embryo selection, genetic mutations, and long-term health implications. Ethical considerations surrounding ICSI's broad applications also surface.

Conclusions

Despite its success and effectiveness, ICSI is still evolving as a therapeutic method. By comprehensively evaluating the historical progress and the current status of ICSI and exploring its future prospects, this study highlights the importance of ICSI in infertility treatment.

Comparison of the assisted reproductive technology outcomes between conventional IVF and ICSI with donor oocytes in normozoospermic patients

There is no evidence for the superiority of conventional in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) using donor oocytes. This retrospective descriptive study aimed to compare the outcomes of conventional IVF (n = 506) and ICSI (n = 613) with donor oocytes in (n = 968) normozoospermic patients. Although the fertilization rate was statistically higher in the ICSI group (p < 0.001), conventional IVF provided better results than ICSI with respect to embryo quality (number of grade A embryos, p < 0.001). In addition, we observed more blastocysts in the conventional IVF group (p < 0.001) and more good quality embryos were obtained for cryopreservation compared to ICSI (p < 0.001). Regarding clinical results, there were no statistical significant differences in the positive pregnancy test, clinical pregnancy and clinical miscarriage rates between IVF and ICSI. However, the implantation rate was statistically higher when IVF was performed (50.4% vs. 43.0%, p = 0.031, OR (95% CI): 1.185 (1.050-2.530)). In conclusion, with the use of normozoospermic samples in our oocyte donation programme, IVF offers more embryo efficiency and increased implantation rates than ICSI.

Re-evaluation of post-wash sperm is a helpful tool in the decision to perform in vitro fertilisation or intracytoplasmic sperm injection

The aim of this study was to find discriminatory parameters, based on sperm characteristics on the day of ovum pickup, that can help guide the decision to perform either intracytoplasmic sperm injection (ICSI) or in vitro fertilisation (IVF). We evaluated 112 cycles fertilised with both regular and ICSI insemination during the same cycle. A total of 112 cycles were analysed. In 62 cycles, fertilisation was obtained with both ICSI and IVF, and in 50 cycles, fertilisation was obtained by ICSI alone. The sperm samples were re-evaluated after the preparation process. The mean initial total motile sperm count (TMSC) was 66.3 × 10(6) ± 47.5 in the group that underwent both methods and 23.1 × 10(6) ± 20.4 in the ICSI only group (P < 0.05). After sperm preparation, the mean post-wash TMSC was 4.4 × 10(6) ± 3.4 and 1.06 × 10(6) ± 0.9 respectively (P < 0.05). A cutoff of 1.5 × 10(6) or fewer sperm after preparation as an indicator for ICSI has a sensitivity of 80% and a specificity of 77%. Re-evaluation of TMSC can prevent unexpected fertilisation failure. Fewer than 1.5 million TMSC after wash should be considered an indication for ICSI fertilisation.

Experiences with intracytoplasmic sperm injection

Mammalian fertilization, whether it takes place within the female reproductive tract or within a laboratory dish, is comprised of many processes which must follow a specific sequence. The spermatozoon must bind to and pass through the zona pellucida, fuse with the oolemma and become incorporated into the cytoplasm of the oocyte. Fusion of the two gametes triggers oocyte activation, resulting in exocytosis of the cortical granules and completion of the second meiotic division of the oocyte. A block in one or more of these processes, due either to abnormalities in the spermatozoon or oocyte, may result in fertilization failure.

Should ICSI be used in non-male factor infertility?

There is general agreement that intracytoplasmic sperm injection (ICSI) should be used in male factor infertility cases, such as oligoasthenoteratozoospermia, presence of anti-sperm antibodies, or azoospermia, these cases being diagnosed through abnormal semen analysis. There are no randomized clinical trials comparing ICSI with IVF (or other interventions) where semen quality is so poor that IVF would not achieve fertilization. It is accepted that ICSI is the only treatment option in those circumstances. The role of ICSI where IVF can be expected to give a reasonable fertilization rate is the question that needs to be answered. The argument is whether or not ICSI should be used for all cases of infertility. This paper proposes and strongly supports the use of ICSI for all indications. Considerations of fertilization and embryo development, cost effectiveness and safety will be clearly discussed.

Intracytoplasmic sperm injection versus in vitro fertilization: a randomized controlled trial and a meta-analysis of the literature

OBJECTIVE

To compare ICSI with IVF using two insemination concentrations in moderate male infertility and to compare these data with other randomized controlled trials (RCTs).

DESIGN

Prospective, randomized, controlled trial and meta-analysis.

SETTING

University-based tertiary referral center.

PATIENT(S)

Seventy-three couples undergoing ART.

INTERVENTION(S)

In one IVF group a standard insemination concentration of 0.2 x 10(6)/mL was used, whereas in the other group a high insemination concentration (HIC) of 0.8 x 10(6)/mL was used. Each protocol was compared with ICSI on sibling oocytes.

MAIN OUTCOME MEASURE(S)

Fertilization, fertilization failure, and embryonic development.

RESULT(S)

The overall fertilization rate was significantly lower after standard IVF than after ICSI: 37.4% vs. 64.3%. Where HIC IVF was used, the overall fertilization rate was not significantly different from that after ICSI: 59.6% vs. 67.6%. Eight randomized controlled trials were selected and reviewed together with the present randomized controlled trial by meta-analysis. The risk ratio for an oocyte to become fertilized was 1.9 (95% confidence interval of 1.4 to 2.5) in favor of ICSI, and 3.1 ICSI cycles may be needed to avoid one complete fertilization failure after conventional IVF (95% CI of 1.7 to 12.4).

CONCLUSION(S)

The data from this study and the meta-analysis show that ICSI is a more efficient technique in terms of fertilization, but not in comparison with HIC IVF.

Should ICSI be the treatment of choice for all cases of in-vitro conception?

The objective of this study was to examine different clinical scenarios of in-vitro conception, viz. fertilization with conventional IVF, IVF with high insemination concentration (HIC) and intracytoplasmic sperm injection (ICSI), and assess on a sibling oocyte comparison the hypothesis that ICSI should be performed in all cases requiring in-vitro conception. ICSI with husband's spermatozoa had a higher incidence of fertilization as compared with IVF or IVF with HIC with donor spermatozoa (if previous failure of fertilization had occurred) for unexplained infertility. Similarly, ICSI with husband's spermatozoa had as high an incidence of fertilization as IVF with donor spermatozoa for patients with severe oligozoospermia, asthenozoospermia and/or teratozoospermia, even when the spermatozoa were not selected for their morphology. Two studies were performed to assess ICSI in potential oocyte-related failure of IVF, viz. when fertilization occurred in >50% of oocytes for one group of patients, and in <50% of oocytes in a second group. In both of these studies a significant proportion of the oocytes that failed to fertilize with conventional IVF eventually fertilized after ICSI. The overall conclusion was that ICSI as a first option offers a higher incidence of fertilization, maximizes the number of embryos and minimizes the risk of complete failure of fertilization for all cases requiring in-vitro conception. However, among other concerns, current knowledge of ICSI as an outcome procedure does not provide the confidence to use this process in all cases of IVF for the time being.

Preconceptional sex selection: past, present, and future

Predetermination of sex in human and in farm animals is reviewed. Preconceptional sex selection has generated great interest and controversy over the years. Medical and commercial benefits outweigh the ethical issues. Technology has not yet provided a routine method for separating the X- and Y-chromosome-bearing sperm. Flow cytometry is the only technique that produces a clinically significant enrichment of X- or Y-bearing spermatozoa However, concern has been raised about the methodological implications of the flow technique because of the use of DNA stains and UV light. Some other techniques, such as gradient columns, appear to produce a slight enrichment of one type of sperm over the other, but this level of enrichment appears unlikely to affect the sex ratio at birth. It thus remains speculative whether 100% pure preparation of X or Y sperm can be obtained unless a major improvement in methodology is achieved. Fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) are currently the methods of choice for evaluating the validity of the sex selection procedure. In view of the extraordinary pace of the technological and scientific progress, it can be expected that the clinical and commercial application of the technology of preconceptional sex selection by X and Y sperm separation will be a reality in near future.

In vitro fertilization for male infertility: when and how?

The first observation that in vitro fertilization (IVF) was useful for treating oligozoospermia and oligoasthenozoospermia was reported by Fishel and Edwards in 1982. This was followed by a series of cases indicating the value of IVF in such cases. Conventional IVF has been modified and refined to achieve increased rates of conception in cases of male factor infertility. Methods such as high insemination concentration IVF for the treatment of teratozoospermia and microscopic IVF for the treatment of oligozoospermia have had some impact on fertilization and pregnancy rates; however, reports of success are varied. The recent advent of micromanipulation and, in particular, intracytoplasmic sperm injection (ICSI) has overshadowed the use of these modified IVF procedures. Because of the high fertilization and pregnancy rates achieved with ICSI, other micromanipulation techniques (subzonal insemination and partial zona dissection) have been abandoned; there have also been suggestions that other more conventional techniques, i.e. IVF, should also be abandoned and that ICSI become the sole technique for the treatment of infertility. The rapid increase in the number of centres using ICSI has led to extreme pressure for individual units to achieve high fertilization and pregnancy rates and there is a temptation to assign all patients to ICSI treatment. It is important that, in this highly competitive environment, new techniques are not applied haphazardly and reduced to the mere injection of gametes and achievement of pregnancy regardless of the cause of infertility. In his 1986 IVF--Historical Perspective, Fishel quoted Auguste Comte: 'to understand science it is necessary to know its history'. IVF has much recent history in animal and also human work. Although ICSI is the most significant therapeutic advance in male infertility treatment, its application to human IVF is only 4 years old, with a paucity of animal studies on which to rely. For this reason IVF still plays a very important role in the treatment of male factor infertility and should only be ruled out when it has failed previously or the number of available sperm is limited.

Relationship of acrosin activity to sperm function tests

Acrosin activity of spermatozoa from infertile patients and fertile volunteers was measured. Acrosin activity of spermatozoa from asthenozoospermic patients and patients with unexplained infertility was lower than that from fertile volunteers. We utilize the zona-free hamster egg-sperm penetration test to select candidates for conventional in vitro fertilization among unexplained infertile patients. The zona-free hamster egg sperm penetration test, however, requires several hours and special equipment which are not used in the clinical setting. It is preferable that other sperm function tests or a combination of them can replace this test. Thus three distinct tests of sperm function, namely, acrosin activity, Penetrak test, hypo-osmotic swelling test, were compared with the hamster test, using spermatozoa from patients with unexplained infertility. A combination of the Penetrak test and measurement of acrosin activity could predict the results of the zona-free hamster egg sperm penetration test with 88.2% accuracy. Thus, the hamster test should be done when either Penetrak test or measurement of acrosin activity showed abnormal values.

Practical evolution and application of direct intracytoplasmic sperm injection for male factor and idiopathic fertilization failure infertilities

OBJECTIVE

To analyze the introduction of a new assisted fertilization technique for the treatment of severe male factor and idiopathic fertilization failure infertilities.

DESIGN

Retrospective analysis of 16-month clinical application of IVF-ET where insemination was performed solely by direct intracytoplasmic sperm injection.

SETTING

Clinical IVF-ET program.

PATIENTS

Ninety-two couples undergoing 105 cycles of sperm injection.

RESULTS

One hundred embryo transfers yielded 28 viable pregnancies (28%) from which eight normal deliveries have occurred to date. Complete cleavage arrest or fertilization failure occurred in four cycles, and one couple had all embryos cryopreserved. One thousand one hundred forty-three eggs were injected of which 173 (15%) degenerated. Four hundred seventy-nine of the surviving 970 eggs became normally fertilized (49%), and 381 of these zygotes (79.5%) developed suitably for cryopreservation or for transfer. Thirty-four of 310 embryos transferred implanted, yielding an implantation rate of 11%. Both testicular and epididymal sperm were used successfully to achieve fertilization and pregnancies, as was sperm retrieved by electroejaculation. Older women and couples suffering from prior idiopathic fertilization failure had a markedly poorer outcome.

CONCLUSIONS

These results confirm that the intracytoplasmic sperm injection technique is a successful form of assisted fertilization that can be applied to a wide range of couples at significant risk from fertilization failure.

A simple approach to intracytoplasmic sperm injection

OBJECTIVE

To describe a simple injection apparatus and method for performing intracytoplasmic sperm injection in a clinical IVF program.

DESIGN

A prospective clinical trial of intracytoplasmic sperm injection.

SETTING

A private office-based fertility program.

PATIENTS

Five couples undergoing IVF-ET with intracytoplasmic sperm injection as a treatment for male factor infertility.

INTERVENTIONS

Intracytoplasmic sperm injection was performed at room temperature (23.5 to 24.5 degrees C) in a simple zwitterion-buffered medium.

MAIN OUTCOME MEASURES

Fertilization rates, cleavage rates, clinical pregnancy rates, implantation rates.

RESULTS

Intracytoplasmic sperm injection was performed on 44 fresh oocytes from five patients. Twenty-three oocytes fertilized (52.3%) and 22 zygotes cleaved (95.7%). Three of five patients became pregnant (60%), resulting in the live birth of one normal male infant, one continuing singleton pregnancy, and one continuing twin gestation (46XX, 46XY). The implantation rate was 23.5%.

CONCLUSION

Intracytoplasmic sperm injection can be performed successfully in a simple medium at room temperature using commercially available microtools.

Micromanipulative and conventional insemination strategies for assisted reproductive technology

Micromanipulative techniques, such as subzonal insemination and direct intracytoplasmic sperm injection, are used when standard in vitro fertilization techniques have failed. These new approaches are currently under investigation in a variety of centers across the country. The projected results and the strengths and weaknesses of these techniques are reviewed.

More than 90% fertilization rates after intracytoplasmic sperm injection and artificial induction of oocyte activation with calcium ionophore

OBJECTIVE

To examine whether fertilization rates after intracytoplasmic sperm injection can be increased by artificial oocyte activation.

DESIGN

Oocytes that failed to fertilize spontaneously by 24 hours after intracytoplasmic sperm injection were treated either with calcium ionophore to induce activation or with solvent only to serve as control. The ability of ionophore-treated and control oocytes to achieve delayed fertilization was compared.

SETTING

Private hospital and public research center.

PATIENTS

Infertile couples treated by intracytoplasmic sperm injection.

INTERVENTIONS

Intracytoplasmic sperm injection.

MAIN OUTCOME MEASURES

Fertilization and cleavage rates.

RESULTS

The mean rate of spontaneous fertilization after intracytoplasmic sperm injection was 32%, but 88% of the oocytes that failed to fertilize spontaneously did so after subsequent exposure to calcium ionophore. Most of these oocytes underwent at least one apparently normal cleavage division. In contrast, delayed fertilization of oocytes not treated with ionophore was an exceptional finding. If only oocytes remaining intact after intracytoplasmic sperm injection are taken into account, the mean global fertilization rate of ionophore-enhanced intracytoplasmic sperm injection was 91%.

CONCLUSIONS

These results show that the failure of oocyte activation is the main cause of fertilization failure after intracytoplasmic sperm injection. If an appropriate, clinically applicable treatment is found to overcome this problem, intracytoplasmic sperm injection can be expected to yield fertilization rates far exceeding those of standard IVF with normal spermatozoa.

Gamete microsurgery for assisted fertilization

Several methods of gamete microsurgery have been proposed to facilitate the union of the spermatozoon and oocyte in infertile couples. Partial zona dissection, subzonal sperm insertion, and intracytoplasmic sperm insertion are the three techniques currently being used for assisted fertilization in human in vitro fertilization laboratories. Fertilization and pregnancy rates after partial zona dissection and subzonal insertion have been variable and rather low. Recent reports of relatively high fertilization and pregnancy rates achieved after intracytoplasmic sperm insertion have rejuvenated interest in gamete microsurgery. Methods for each procedure are described. Studies which have attempted patient selection for gamete microsurgery are discussed.