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A Review of the Human Oocyte and ICSI Practice

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A Review of the Human Oocyte and ICSI Practice in vivo 30 : 387-400 (2016) Review Making ICSI Safer and More Effective: A Review of the Human Oocyte and ICSI Practice MARA SIMOPOULOU 1,2 , POLINA GIANNELOU 2, PANAGIOTIS BAKAS 2, LAERTIS GKOLES 2, THEODOROS KALAMPOKAS 2, KONSTANTINOS PANTOS 3 and MICHAEL KOUTSILIERIS 1 1Department of Physiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece; 2Assisted Conception Unit, Second Department of Obstetrics and Gynecology, Aretaieion Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece; 3Centre for Human Reproduction, Genesis Hospital, Athens, Greece Abstract. Intracytoplasmic sperm injection (ICSI) has separately. However, ICSI is a multifaceted procedure become an indispensable procedure of every assisted involving several consecutive steps and when evaluating one reproduction unit. This has created as much controversy as we cannot exclude the end effect of the previous, or the it has awe. As this is a multistep invasive technique, every overall effect of the different practitioners involved form part of the procedure has become subject to investigation. beginning to end. We contribute this review aspiring to offer the embryologist insight into all available approaches of securing an effective Recent global demographic surveys indicate that infertility ICSI practice. Herein we present all the different approaches remains an ongoing reproductive problem and is estimated with respect to handling of the human oocyte, taking into to affect as many as 186 million people worldwide (1) . The consideration the important steps of the technique such as assisted reproductive technology (ART) community is the oocyte positioning, timing of performing ICSI, the option committed to working towards not just a positive pregnancy of viewing the meiotic spindle and further individual action test but rather striving to secure excellent obstetric and such as artificial oocyte activation, rescue ICSI and in vitro perinatal outcomes. An estimated 3.75 million births have maturation. We enrich this by including our view based on resulted from assisted conceptions (2) During the last 37 our collective experience and current practice. Published years since the birth of Louise Brown, the world of in vitro studies have led to various options for performing ICSI, fertilization (2) has changed dramatically from overcoming resulting in in vitro fertilization units around the world blocked fallopian tubes into the era of the ‘omics’ evaluation adopting different approaches. The steps that ICSI technique of the embryo, employing equally invasive and non-invasive entails discussed from the oocyte perspective are still a long tools that promise to predict and improve results. way from being organized into one secure and optimal The evolution of several techniques dedicated to assist protocol. Our stressing of the need to secure an efficient ICSI male factor infertility in the IVF laboratory incidentally led protocol could be the trigger for further well-designed larger to the birth of intracytoplasmic sperm injection (ICSI) (1) scale studies with all the latest technological advantages. We and the face of IVF has never been the same since. The ICSI aim to approach this subject in categories and assess them procedure entails the deposition of a single spermatozoon directly into the cytoplasm of the oocyte, thus bypassing the zona pellucida (3) and the oolemma. Due to the invasive nature of ICSI, which goes hand in hand with eliminating Correspondence to: Mara Simopoulou, Assistant Professor of natural selection barriers by bypassing many steps in the Physiology, Clinical Embryologist/Geneticist, 75, Mikras Asias, 11527 normal process of fertilization, numerous studies have Athens Greece, Building 16, Department of Physiology-Department focused on assessing the associated potential health risks. of Obstetrics and Gynaecology, Medical School, National and Studies have concluded that both IVF and ICSI could pose Kapodistrian University of Athens, Greece. Tel: +30 2107286278, Fax: +30 2107462592, e-mail: [email protected] a risk factor for both mother and baby, form pregnancy complications such as pre-eclampsia, growth retardation, and Key Words: ART, fertilization, oocytes, ICSI technique, oocyte prematurity (4), as well as higher rate of congenital handling, improving ICSI rates, review. malformations, developmental abnormalities and a higher 0258-851X/2016 $2.00+.40 387 in vivo 30 : 387-400 (2016) risk of increased aberrations in imprinting patterns due to the disruption of the meiotic spindle can lead to rearrangement of possible transmission to progeny from ICSI of chromosomal chromosomes in the cytoplasm and may contribute to alterations leading to all the above (5, 6). However, an equal aneuploidy after fertilization (13). Therefore, in order to avoid number of studies negate any correlation (7-9) and damage to the spindle that may lead to genetic abnormalities, emphasize that any association could very well be attributed embryologists orientate the oocyte on the holding pipette on to the increased risk for health problems present in couples the basis of the position of the first polar body (14). undergoing IVF/ICSI cycles and not the actual techniques Understanding the risks of such a delicate procedure, in themselves. Before placing the blame, we need to remember order to reduce possible damage to the precious oocyte, the that in the frame of ART, it is not feasible to dissociate the most common clinical practice of ICSI involves positioning the effect of a certain technique from the effect of the existing first polar body at 6 or 12 o’clock (see Figure 1) and injection biological and clinical profile of the prospective parents, let of spermatozoa into the oocyte at 3 to 9 o’clock (14). alone the effect of the overall treatment during an ICSI cycle, In 1995, exploring the different practices for ICSI, from ovarian simulation to embryo culture conditions. The including sperm deposition and oolemma breakage, Nagy et follow-up studies on children from ICSI have shown that the al. reported that there were no differences in the survival rate procedure is safe and the slightly higher incidence of and in the normal fertilization rate between the 6 and the 12 neonatal malformations or de novo gonosomal abnormalities o’clock positioning of the polar body, but a significantly are related to the genetics of the infertile couples (10). higher rate of good-quality embryos after two days in culture There has been much hype lately within the clinical was noted for the 6 o’clock position group. In the same embryology community with respect to how best to approach decade, Westerlaken et al. also found that orientation of the ICSI practice, especially with respect to controversial first polar body at 6 o’clock resulted in a significantly higher procedures suggested for extremely challenging and rare proportion of good quality embryos in comparison to that at circumstances, such as zona-free oocytes or globozoospermia 12 o’clock. (15, 16). Subsequent studies that compared the (11). With this review, our principal intention is to offer the two accepted clinical practices of positioning the first polar embryologist and the standard IVF laboratory insight as to body at 6 and 12 o’clock demonstrated different outcomes the clinical options practiced in routine typical ICSI cases and slowed that the orientation of the first polar body during and the challenges arising from such. In the following ICSI does not seem to affect the clinical outcome (17, 18). sections, we provide insight into the various approaches In 2000, Blake et al. , on the assumption that the second regarding the oocyte in relation to ICSI and evaluate their meiotic metaphase II spindle lies in close proximity to the clinical significance in improving the outcome. An outline first polar body, attempted injection in nine distinct of our approach analysis is clearly illustrated in Table I. Our orientations so that the first polar body was stabilized at 5, review is arranged in the following categories: handling and 6, 7, 8, 9, 10, 11, 12, or 1 o’clock, excluding the most rarely positioning of the oocyte, timing of performing ICSI, the performed positions (2, 3 and 4 o’clock) with greater risk of option of viewing the meiotic spindle during the procedure, damaging the spindle. A total of 10.417 metaphase II oocytes the effect of the numerous stimulation protocols that yield were assessed for this study and showed that the location of oocytes, and further special treatments deemed necessary the meiotic spindle in relation with the sperm deposition can such as artificial oocyte activation (AOA) and in vitro in fact affect the fertilization rate as well as embryo maturation (IVM). Finally with respect to the procedure, we development. Therefore, the study suggested the polar body acknowledge the effect of the medium environment and not to be positioned at 8, 9 or 10 o’clock, nor at 5, 6, 12 and physical conditions during ICSI, the several options 1 o’clock because of the potential delay in pronuclear available, and even the human element namely the differing syngamy. Furthermore, orientation of the polar body at the experience from practitioner to practitioner which always 7 or 11 o’clock position during ICSI appears to ensure higher adds another level of complexity when aiming to conclude fertilization rates and the development of the greatest to what should be avoided and what should be adopted in proportion of high-quality embryos (19).
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