研究開発・学会発表

Study question:

Does piezo-assisted intracytoplasmic sperm injection (ICSI) for human oocyte lead to a different outcome from conventional ICSI?

Summary answer:

When compared to conventional ICSI, the blastocyst and good-quality blastocyst development rate was positively affected by Piezo-ICSI in patients with age older than 35.

What is known already:

In conventional-ICSI, an injection needle penetrates the oolemma through the zona pellucida, which can cause harmful effect to the zona. Piezo-actuated micromanipulation makes the constant vibration to the tip, which makes the smooth puncture of the zona without need for suction of ooplasm, minimizing the damage of oocyte during procedure. Piezo-ICSI is now widespread among the animal laboratory especially mice, because it’s plasma membrane has high extendibility and ooplasm has low viscosity. However there are few evidences among human oocyte and no prospective randomized controlled trail (RCT) is reported at this time.

Study design, size, duration:

In this study, we performed prospective paired RCT with sibling oocyte retrieved more than two oocytes per women at our institution, between October 2017 and July 2018. Oocytes were randomly allocated to Piezo-ICSI and conventional ICSI for fertilization subsequently to oocyte retrieval, all ICSI procedures were performed by single expert technician.

Participants/ materials, setting, methods:

Retrieved oocytes were cultured after 3-5 hours of culture and pipetting was conducted to remove cumulus cells. For conventional ICSI, microinjector of NARISHIGE was used, to which gauge of outside diameter 6.0 um and inside diameter 4.7 um needle was attached. A injection tube was connected through a needle holder. For piezo-ICSI, microinjector of outside diameter 6.7 um and inside diameter 4.5 um was connected to the drive unit of piezo-micromanupulator.

Main results and the role of chance:

We randomized 957 matured oocytes retrieved from 137 women to conventional-ICSI (472 oocytes) and piezo-ICSI (475 oocytes). The overall outcomes were similar among conventional-ICSI vs piezo-ICSI; fertilization rate 82.0% vs 86.5% p=NS, blastocyst development rate 50.2% vs 54.9% p=NS and good quality blastocyst development rate 51.2% vs 54.9% p=NS respectively. However, subgroup analysis among patient’s age > 35 revealed that the oocytes underwent piezo-ICSI showed significantly better outcomes (conventional vs Piezo-ICSI: fertilization rate 79.7% vs 86.3% p<.05, blastocyst development rate 39.6% vs 52.4% p<.05, good-quality blastocyst development rate;50.7% vs 56.0% p<.05). There were no differences among the patients age 35 or younger between two groups.

Limitations, reasons for caution:

This study only evaluated fertilization and blastocyst development and there is no data about the pregnancy rate or live birth rate.

Wider implications of the findings:

Piezo-ICSI showed more favorable outcomes than conventional-ICSI in case with patient’s age was older than 35 years, indicating that flat tip and vibration of the piezo can be more protective to oocyte and cause less damage to the aging oocyte.