Clinical efficiency of Piezo-ICSI using micropipettes with a wall thickness of 0.625 μm

Abstract

Purpose: The purposes of the present study are to assess the clinical efficiency of Piezo-intracytoplasmic sperm injection (ICSI) and to improve the Piezo-ICSI method for human oocytes.

Methods: We examined three ICSI methods to determine their clinical efficiency by comparing the survival, fertilization, good-quality day-3 embryo, pregnancy, and live birth rates. The three ICSI methods tested were conventional ICSI (CI) (using beveled spiked micropipettes with a wall thickness of 1 μm), conventional Piezo-ICSI (CPI) (using flat-tipped micropipettes with a wall thickness of 0.925 μm), and improved Piezo-ICSI (IPI) (using flat-tipped micropipettes with a wall thickness of 0.625 μm). We collectively investigated 2020 mature oocytes retrieved from 437 patients between October 2010 and January 2014.

Results: The survival rates after CI, CPI, and IPI were 90, 95, and 99 %, respectively. The fertilization rates after CI, CPI, and IPI were 68, 75, and 89 %, respectively. The good-quality day-3 embryo rates after CI, CPI, and IPI were 37, 43, and 55 %, respectively. The pregnancy rates after the transfer of good-quality day-3 embryo of CI, CPI, and IPI were 19, 21, and 31 %, respectively. The live birth rates of CI, CPI, and IPI were 15, 16, and 25 %, respectively. Significantly higher survival, fertilization, good-quality day-3 embryo, pregnancy, and live birth rates were obtained using IPI.

Conclusions: When comparing the IPI to the CI and CPI, the results revealed that the Piezo-ICSI using flat-tipped micropipettes with a wall thickness of 0.625 μm significantly improves survival, fertilization, good-quality day-3 embryo, pregnancy, and live birth rates.

Keywords: Fertilization; Human; ICSI; Lysis; Piezo; Wall thickness.

Fig. 1

Photographs of micropipettes. a Micropipette used for conventional ICSI with a beveled and spiked tip (5-μm inner diameter and 1-μm wall thickness: micro-injection pipette, K-MPIP-1035, Cook Ireland Ltd., Ireland). b Micropipette used for conventional Piezo-ICSI with flat tip (5-μm inner diameter and 0.925-μm wall thickness: PIN07-20FT, PRIME TECH Ltd., Japan). c Micropipette used for improved Piezo-ICSI (5-μm inner diameter and 0.625-μm wall thickness: PINU06-20FT, PRIME TECH Ltd., Japan)

Fig. 2

Drive unit of a Piezo-micromanipulator (MB-U, PRIME TECH Ltd., Japan) attached to the micropipette holder

Fig. 3

Zona drilling of conventional ICSI (CI) and Piezo-ICSI (PI) prior to ICSI. CI: before drilling (a), during drilling (b), and after drilling (c). PI: before drilling (a’), during drilling (b’), and after drilling (c’)