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Piezo-ICSI Kenichiro Hiraoka, Kiyotaka Kawai, Tatsuya Harada, and Tomonori Ishikawa 39.1

Introduction – 482

39.1.1

Brief History of Intracytoplasmic Sperm Injection (ICSI) – 482

39.2

Summary – 488

Review Questions – 489 References – 489

© Springer Nature Switzerland AG 2019 Z. P. Nagy et al. (eds.), In Vitro Fertilization, https://doi.org/10.1007/978-3-319-43011-9_39

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482

K. Hiraoka et al.

Learning Objectives 55 To review the current techniques for intracytoplasmic sperm injection (ICSI) in human oocytes 55 To clarify the problems in the current ICSI technique (Conventional-­ICSI) 55 To introduce a new technology of ICSI (Piezo-ICSI) to improve the survival and fertilization rates for injected oocytes 55 To survey how Piezo-ICSI can contribute to the human assisted reproductive technology field

Key Points 55 In the Conventional-ICSI technique, the cytoplasm is aspirated into the micropipette to break the membrane. 55 The volume of cytoplasm aspirated into the micropipette at the membrane breakage point affects the fertilization rate after ICSI. 55 In the Piezo-ICSI technique, the cytoplasm is not aspirated into the micropipette. 55 Piezo-ICSI results in higher survival and fertilization rates than Conventional-ICSI. 55 The micropipette wall thickness used for Piezo-ICSI affects the survival and fertilization rates after ICSI. 55 Piezo-ICSI can contribute to shortening the training period for ICSI for junior embryologists.

39.1  Introduction 39.1.1  Brief History of Intracytoplasmic

39

Sperm Injection (ICSI)

The first four pregnancies achieved by ICSI were reported by Palermo in 1992 [1], and ICSI is now an essential technique in human assisted reproductive technology (ART). ICSI uses beveled and spiked micropipettes (. Fig.  39.1a) for mechanical penetration of the zona pellucida and the membrane as well as aspiration of the cytoplasm into the micropipette to break the membrane. After membrane breakage, the sperm is injected into the cytoplasm (ConventionalICSI). However, the survival rate of mouse oocytes (oocyte diameter 80 μm) was as low as 16% (8% fertilization rate) after Conventional-­ICSI [2].  

a

..      Fig. 39.1  Micropipettes for Conventional-ICSI a and Piezo-ICSI b

Kimura and Yanagimachi performed membrane breakage by applying a piezo pulse, which produced ultrafast submicron forward momentum using uniquely shaped flat-tipped micropipettes with no bevel or spike (. Fig. 39.1b) (Piezo-ICSI), in 1995 for mouse oocytes [2]. The survival rate of mouse oocytes was dramatically improved to 80% (78% fertilization rate) by using PiezoICSI [2]. Therefore, the Piezo-ICSI may be a less invasive method also for human oocytes (oocyte diameter 160 μm). However, to the best of our knowledge, only four reports detail the application of Piezo-ICSI to human oocytes, and little information is available regarding its clinical efficiency [3–6]. The goal of this chapter is to compare Conventional-ICSI and Piezo-ICSI techniques and to show the superiority of the Piezo-ICSI technique.  

39.1.