Human Reproduction

Updates and New Horizons

Heide Schatten, Heide Schatten

• Publisher: Wiley-Blackwell
• Year: 2016
• ISBN:
  9781118849576
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

In vitro fertilization (IVF) and other assisted reproductive technologies (ART) have become a significant part of human reproduction, with already one in 50 children worldwide being born through ART and the demand steadily increasing. To accommodate the various kinds of infertility problems, new methods have been developed to increase IVF and ART success rates and it has also become possible to treat sperm, eggs, and embryos in culture to improve reproductive success, to increase the health state of an embryo, and to prevent disease in the developing child.

Human Reproduction: Updates and New Horizons focuses on recent developments and new approaches to study egg and sperm cells and embryo development, as well as addressing the increasing demand for IVF and ART to overcome infertility problems of various kinds that are encountered by an increasing number of couples worldwide. The book includes 10 chapters written by experts in their specific fields to provide information on sperm selection techniques and their relevance to ART; In vitro maturation of human oocytes: current practices and future promises; Molecular biology of endometriosis; Novel immunological aspects for the treatment of age-induced ovarian and testicular infertility, other functional diseases, and early and advanced cancer immunotherapy; Mitochondrial manipulation for infertility treatment and disease prevention; Novel imaging techniques to assess gametes and preimplantation embryos; Clinical application of methods to select in vitro fertilized embryos; New horizons/developments in time-lapse morphokinetic analysis of mammalian embryos; The non-human primate model for early human development; Cytoskeletal functions, defects, and dysfunctions affecting human fertilization and embryo development.

This book will appeal to a large interdisciplinary audience, including researchers from both the basic science and medical communities. It will be a valuable reference for IVF clinicians, patients and prospective patients who are considering ART procedures, embryologists, cell biologists and students in the field of reproduction.

Chapter 1
Sperm Selection Techniques and their Relevance to ART

Luke Simon¹, Monis B. Shamsi² and Douglas T. Carrell^1,2,3

¹Andrology and IVF Laboratory, Department of Surgery (Urology), University of UT, Salt Lake City, UT, USA

²Department of Obstetrics and Gynecology, University of UT, Salt Lake City, UT, USA

³Department of Human Genetics, University of UT, Salt Lake City, UT, USA

1.1 Introduction

Fertilization is now possible using any available sperm through intra-cytoplasmic sperm injection (ICSI) treatment (Palermo et al., 1992). As a result, andrological research has raised questions regarding the selection of suboptimal sperm used for assisted reproductive technology (ART) (Avendano and Oehninger, 2011). In recent years, the role of sperm in ART has been highlighted as the sperm provides one half of the genome to the developing embryo. The use of healthier sperm has showed to improved ART outcomes and subsequently, sperm selection has become an integral part of ART procedure (Said and Land, 2011). Since the birth of first in vitro fertilization conceived baby in 1978, sperm selection for ART has been focused on selecting physiologically motile and morphologically normal sperm (Bartoov et al., 2002). Despite success, it has become evident that physical appearances of the sperm are inefficient to identify the most suitable sperm for ART success (Yetunde and Vasiliki, 2013). Hence, recent research is focused on developing novel sperm biomarkers to identify non-apoptotic sperm with high DNA integrity for successful use in ART.

Our understanding of sperm physiology, as well as the technology to select healthier sperm has progressively been improved. Initially, sperm selection was based on simple semen washing procedures and now more sophisticated sperm separation measures have evolved (Simon et al., 2015). The sperm is regarded unusable for the use in ART, after being analyzed for its molecular parameters such as DNA integrity, histone retention, protamine content, or ratio, and so on. Therefore, preserving the structural and functional integrity of the sperm is been the goal for recently introduced novel sperm selection approaches (Berkovitz et al., 2006a, 2006b). Some novel sperm selection approaches aim to mimic the natural selection process, where the female reproductive tract is known to eliminate poor quality sperm to enhance the chances of a successful fertilization (Holt and Fazeli, 2015). Other methods have focused on sperm physiological changes in the female reproductive tract, like capacitation, which are functionally important for acrosome reaction (Bedford, 1963). Inclusion of such novel biomarkers along with standard sperm preparation procedures has shown promises to enhanced fertilizing ability and improves ART success (Nasr-Esfahani et al., 2008a; Kheirollahi-Kouhestani et al., 2009; Polak de Fried and Denaday, 2010; Wilding et al., 2011).

1.2 Need of Sperm Selection in ART

Human semen is comprised of heterogeneous sperm population with varying degrees of structural differentiation, maturity, fertilizing ability, and functional quality (Huszar et al., 1993, 1998). During natural conception the sperm from these subpopulations compete to traverse through several anatomical and physiological barriers in the female tract. The most competent and reproductively efficient sperm are able to migrate through the cervical mucosa, uterus, uterine tube, cumulus cells, zona pellucida, and finally oolemma to participate in the fertilization (Suarez and Pacey, 2006). Further, selection takes place at the level of sperm-oocyte interaction and out of a population of millions, a single sperm is able to fertilize the oocyte and develop into an offspring. These barriers for natural selection exclude the sperm with structural abnormalities as acrosomal absence, flagellar deformity, immature sperm, and sperm with aneuploidy or other chromatin abnormalities from participating in a successful fertilization (Suarez and Pacey, 2006). On the contrary, during ART, sperm are brought in proximity to oocyte, outside the female body, where no such anatomical and physiological barriers exist. Depending upon the technique of ART, either the sperm fertilize the oocyte on their own as in IVF or the sperm are injected into oocyte for fertilization as in ICSI. During ART, sperm does not have to overcome any anatomical and physiological barriers present in the female reproductive tract, natural sperm selection are bypassed. Therefore, it is imperative to have an efficient artificial selection process that maximizes the probability of successful pregnancy and birth of a healthy offspring. Further, the sperm selection procedures also help to enrich the concentration of good quality sperm that increases the chance of ART success.

Sperm contribute half of the genome to the offspring. Therefore, selection of sperm with intact chromatin and free of chromosomal abnormalities is important for ART success. Studies indicate that even if the best quality sperm are used for ICSI, approximately, 55% of the selected sperm have normal DNA (Ramos et al., 2004). The primary objective of sperm selection approaches is to select good quality or healthier sperm. In addition, sperm selection approaches are designed to reduce the physiological and oxidative damage induced to the sperm during the selection process. With these perspectives in sight, recent developments in sperm selection approaches are focused on physiological properties or morphological characteristics or behavior in the electric field or basis on their fluid kinetic properties. This chapter discusses some of the novel sperm selection techniques that have been the focus of recent research and may have the ability to revolutionize ART by improving the success rate, even in patients with severely compromised sperm parameters.

1.3 Methodology of Sperm Selection

1.3.1 Intracytoplasmic Sperm Injection

Intracytoplasmic sperm injection (ICSI) is a very useful gamete micromanipulation technique for treating couples with severely compromised sperm parameters. Since its introduction in 1992, ICSI has revolutionized ART by providing hope to couples to achieve a pregnancy, who had few chances of a natural conception or by in vitro fertilization (IVF). The basic principle of ICSI is to manually select the best sperm on the basis of motility and/or morphology and to inject it into an oocyte. The premise for such gamete micromanipulation is that it enables a successful fertilization, when a sperm is unable to fertilize on its own. During this procedure, initial events of fertilization like acrosome reaction are bypassed and now fertilization is possible with any available sperm.

1.3.1.1 Methodology

The oocytes retrieved after ovarian hyper-stimulation is placed in a petri dish (specific for ART) in which they are fertilized with a sperm. The whole process is done with the help of a CCD attached microscope using a micromanipulator. The basic steps for ICSI manipulation are as follows: the oocytes retrieved after hyper-stimulation are held by a specialized holding pipette in a micromanipulator. The most visually normal sperm by virtue of its motility and morphology are picked by ICSI pipette. During this step, sperm are usually visualized at 400× magnification to increase the chances of detecting and eliminating any sperm with morphological abnormalities. The pipette containing sperm is then carefully inserted through the membrane of the oocyte, into the cytoplasm. A sperm is injected into the cytoplasm and the pipette is carefully removed. The oocytes are then incubated and checked for pronuclear appearance to confirm fertilization after 24 hours. After a successful fertilization, the embryos are cultured until cleavage stage (Day 3 embryo transfer) or until blastocyst stage (Day 5 embryo transfer) into the uterus.

1.3.1.2 Advantages and Limitations

ICSI is the most widely used ART, accounting to 70–80% of the cycles performed (Palermo et al., 2009). ICSI has assisted millions of infertile couples to conceive, even with severely compromised sperm parameters, as severe oligozoospermia, asthenozoospermia, or both in the male partner. This technique has dropped down the number of sperm required for fertilization from several thousand to a single viable sperm. In men with...

Table of contents

• Cover
• Title Page
• Copyright
• Table of Contents
• List of Contributors
• Chapter 1: Sperm Selection Techniques and their Relevance to ART
• Chapter 2: In Vitro Maturation of Human Oocytes: Current Practices and Future Promises
• Chapter 3: Molecular Biology of Endometriosis
• Chapter 4: Novel Immunological Aspects for the Treatment of Age-induced Ovarian and Testicular Infertility, Other Functional Diseases, and Early and Advanced Cancer Immunotherapy
• Chapter 5: Mitochondrial Manipulation for Infertility Treatment and Disease Prevention
• Chapter 6: Novel Imaging Techniques to Assess Gametes and Preimplantation Embryos
• Chapter 7: Clinical Application of Methods to Select In Vitro Fertilized Embryos
• Chapter 8: New Horizons/Developments in Time-Lapse Morphokinetic Analysis of Mammalian Embryos
• Chapter 9: The Non-Human Primate Model for Early Human Development
• Chapter 10: Cytoskeletal Functions, Defects, and Dysfunctions Affecting Human Fertilization and Embryo Development
• Index
• End User License Agreement