Review: microinjection of human sperm directly into human oocytes

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.

Ultrastructure of human gametes, fertilization and embryos in assisted reproduction: a personal survey

This extensively illustrated review will cover the progression of recent research on the ultrastructure of human gametes, fertilization and embryos performed in collaboration with colleagues in In vitro fertilization (IVF) centers over the past three decades, in Australia, Singapore, India, England, Sri Lanka, Spain and Italy. It will also include some aspects of gametogenesis and embryogenesis, particularly in relation to the centrosome that activates embryonic development, and is inherited from the father at fertilization. Assessment of both normal and abnormal gametes and embryos and some clinical aspects of assisted reproduction will be discussed. Full reference will also be made to the contribution of other groups to the ultrastructure of reproduction, particularly in humans.

Timing and ultrastructure of events following intracytoplasmic sperm injection in a marsupial, the tammar wallaby (Macropus eugenii)

The aim of the present study was to determine the timing of oocyte activation, sperm decondensation and pronucleus formation after intracytoplasmic sperm injection (ICSI) in the tammar wallaby and to determine the fate of sperm structures at an ultrastructural level. Metaphase II-stage tammar wallaby oocytes were injected with spermatozoa and cultured for 1 (n = 15), 2 (n = 24), 4 (n = 30), 6 (n = 14), 8 (n = 32), 10 (n = 25), 12 (n = 29) or 19 h (n = 12). Oocytes were assessed using light, fluorescence and electron microscopy. The timing of oocyte activation and sperm decondensation after ICSI in the tammar wallaby is relatively similar to that of some eutherian species. Resumption of meiosis II was observed from 1 h and the first female pronucleus was seen 6 h after ICSI. Most oocytes (88%) possessed a female pronucleus by 10 h. Intact acrosomes persisted with intact sperm heads up to 2 h after ICSI. At 10 h, 80% of oocytes possessed a male pronucleus. The sperm tail had undergone considerable degeneration by 10 h after ICSI, including breakdown of the fibrous sheath dense fibres. The identification of sperm tail and midpiece remnants adjacent to pronuclei confirms that the events observed in wallaby oocytes after ICSI are not due to parthenogenetic activation.

Comparison of G1.2/G2.2 and Sydney IVF cleavage/blastocyst sequential media for the culture of human embryos: a prospective, randomized, comparative study

OBJECTIVE

To compare two commercially available sequential media, G1.2/G2.2 and Sydney IVF cleavage/blastocyst media, as supports for human embryo culture.

DESIGN

Prospective randomized study.

SETTING

University-based IVF clinic.

PATIENT(S)

Two hundred forty-nine patients undergoing IVF treatment for the first or second time, randomly allocated at the time of oocyte retrieval, to either culture in G1.2/G2.2 or Sydney IVF media.

INTERVENTION(S)

Oocyte recovery, IVF or intracytoplasmic sperm injection, embryo culture, transfer on day 3 or day 5/6.

MAIN OUTCOME MEASURE(S)

Developmental stage on day 3, blastocyst rate, pregnancy outcome as assessed by beta hCG positive test, implantation rates, and ongoing pregnancies.

RESULT(S)

Embryos cultured in G1.2/G2.2 media displayed a faster kinetics of cleavage, compaction, blastulation, and hatching, but a lower day 3 embryo quality than those grown in Sydney IVF media. For patients with at least five embryos, G1.2/G2.2 media yielded higher implantation rates (26.2%) in our day 3 embryo transfer program when compared to Sydney IVF medium (15.5%), whereas similar implantation rates were obtained for day 5/6 embryo transfer for both media (43.1% and 36.1%, respectively).

CONCLUSION(S)

In our day 3 embryo transfer program, G1.2/G2.2 media were superior to Sydney IVF media, whereas both media yielded similar outcomes in our blastocyst transfer program.

Cytogenetic analysis of uncleaved oocytes after intracytoplasmic sperm injection

PURPOSE

This work analyzes the causes of cleavage failure after intracytoplasmic sperm injection (ICSI) and the effect of the procedure on the chromosomes of the oocytes.

METHODS

Ninety-seven uncleaved oocytes from 39 patients with severe male infertility or repeated IVF failure were fixed; 79 were analyzable. We checked the decondensation stage of spermatozoa nucleus and the chromosomal abnormalities of the oocytes.

RESULTS

Among the fixed oocytes, the spermatozoa nucleus was present in 97% of the cases, and it was undecondensed in 89% of the cases, showing no evolution at all. A low rate (2.6%) of premature chromosome condensation (PCC) of the spermatozoa and a low rate (2.5%) of female diploïdy were observed. Among the oocytes that could be karyotyped, we observed a high rate (45%) of chromosome breakage.

CONCLUSION

ICSI fertilization failure was due mostly to the complete lack of evolution of the spermatozoa nucleus. Oocyte selection before ICSI seemed to lower the PCC rate. The high rate of oocyte chromosomal breakage rate has to be confirmed.