Sperm Chromatin: Biological and Clinical Applications in Male Infertility and Assisted Reproduction

535 Pages·2011·12.18 MB·English

by  Rod Balhorn PhD (auth.)

Sperm Chromatin

Armand Zini • Ashok Agarwal
Editors
Sperm Chromatin
Biological and Clinical Applications
in Male Infertility and Assisted
Reproduction
Editors
Armand Zini, MD Ashok Agarwal, PhD, HCLD (ABB)
Department of Surgery Center for Reproductive Medicine
Division of Urology Glickman Urological and Kidney Institute
McGill University OB-GYN and Women’s Health Institute
St. Mary’s Hospital Center Cleveland Clinic, Cleveland, OH, USA
Montreal, QC, Canada [email protected]
[email protected]
ISBN 978-1-4419-1781-2 e-ISBN 978-1-4419-6857-9
DOI 10.1007/978-1-4419-6857-9
Springer New York Dordrecht Heidelberg London
Library of Congress Control Number: 2011932679
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Foreword
The composition, stability, and integrity of sperm chromatin have major
bearings on the fertilizing potential of male gametes and their capacity to sup-
port normal embryonic development. This assertion is supported by clinical
data generated over the past 10–15 years, indicating the existence of signifi-
cant correlations between DNA damage in spermatozoa and a variety of
adverse reproductive outcomes including reduced conception rates, a high fre-
quency of miscarriage and an escalation in the incidence of birth defects.
Despite this wealth of correlative data, uncertainties remain with respect to
such key questions as the precise nature of the DNA damage, the relative
importance of genetic, epigenetic and environmental factors in its etiology,
and the most effective method for detecting its presence. Answers to these
questions are critical if we are to develop rational strategies for alleviating or,
ultimately, preventing DNA damage in spermatozoa. Furthermore, answers to
these questions are needed if clinicians are to provide patients with informed
v
v i Foreword
advice about the signicfi ance of their DNA damage results. In Sperm
Chromatin: Biological and Clinical Application in Male Infertility and Assisted
Reproduction Ashok Agarwal and Armand Zini have assembled contributions
from a panel of world experts in this area and, in so doing, created an invalu-
able text that brings us up-to-date with recent advances in this efi ld.
The remodeling of sperm chromatin during spermiogenesis is as remarkable
as it is complex. It involves a dramatic morphological and biochemical trans-
formation of chromatin structure through the coordinated movement of pro-
teins in and out of the nucleus to generate a unique, highly compacted matrix.
Furthermore, this extraordinary metamorphosis takes place in the absence of
de novo gene transcription. Indeed, spermiogenesis is an object lesson in how
biological processes can be controlled through the regulated translation of pre-
existing mRNA species. If we could only replicate this process in vitro, research
into the underlying control mechanisms would be greatly facilitated.
Unfortunately, this is not possible at the present time and, as a result, progress
in this area has been painfully slow. Nevertheless, as the pioneer of sperm chro-
matin research, Rod Balhorn, indicates in Chap. 1, we might anticipate more
rapid progress in this area in the future because we now have an array of sophis-
ticated tools to investigate the chromatin remodeling process.
Thus, our new found ability to generate detailed inventories of proteins
and mRNA species in selected cells and tissues is one of the driving forces
behind the modern systems approach to biological research, and the analysis
of sperm chromatin will be one of the major beneficiaries of these technical
developments. In the first section of this book, we see beautifully illustrated
reviews of spermatogenesis (Chap. 2) and chromatin organization (Chaps. 4
and 5) followed by a number of authoritative reviews on aspects of the genome
(Chap. 6), epigenome (Chap. 7), transcriptome (Chap. 8), and proteome
(Chap. 3) from a spermatozoon’s perspective. The detailed chemical analysis
of sperm chromatin using the tools of the -omics revolution will certainly
provide important clues as to the formation and ultimate function of this
material and act as a major stimulus for increased understanding in this area.
The impetus to study the composition and integrity of sperm chromatin
from a clinical perspective can be traced back to the pioneering studies of Don
Evenson, who not only initiated research in this area long before it became
fashionable but also pioneered one of the major analytical techniques used in
the assessment of sperm chromatin, the Sperm Chromatin Structure Assay
(SCSA) (Chap. 9). This assay has now become the industry standard against
all other techniques. In the second section of this book Agarwal and Zini have
gathered together a very impressive list of authors, all of whom share an inter-
est in the laboratory evaluation of sperm chromatin composition and integrity.
The list of techniques is extensive and comprises, in addition to SCSA, meth-
ods that have been borrowed from research in toxicology (Comet; Chap. 15)
or somatic cell apoptosis (TUNEL; Chap. 14) as well as a range of protocols
that are more specicfi to the male germ line including the Sperm Chromatin
Dispersion assay (Chap. 10), the acridine orange test (Chap. 13), the isolation,
puricfi ation and quanticfi ation of protamines (Chap. 16), the aniline blue test
for histone retention (Chap. 12), gene expression prolfiing (Chap. 18), and
analyses of epigenetic modicfi ations to the haploid paternal genome (Chap. 17).
Foreword vii
Additional probes such as toluidine blue and chromomycin 3 (CMA3) are also
important because they provide indirect evidence of the efcfi iency of chroma-
tin packaging (Chap. 11). In this context, Denny Sakkas deserves special men-
tion for his work on the development of CMA3 as an extremely valuable
diagnostic probe, which has consistently been found to generate signicfi ant
information about sperm chromatin status in infertile men.
The clinical and environmental factors that contribute to the etiology of
DNA damage are reviewed in the third section of this book. The range of pos-
sible contributory factors is again extensive and includes oxidative stress
(Chap. 19), apoptosis (Chap. 20), and defective repair of physiological DNA
nicks (Chap. 21). The primary drivers for the oxidative stress, abortive apop-
tosis, and defective DNA repair include infertility (Chap. 22), age (Chap. 23),
cancer (Chap. 24), environmental pollutants (Chap. 25), infection (Chap. 26),
and cryopreservation (Chap. 27). If we understood more about the chemical
nature of the DNA damage seen in human spermatozoa, we might be able to
reduce this long list of potential causative factors down to the major culprits.
However, at present, the only clue we have to the types of DNA damage pres-
ent in human spermatozoa is the high prevalence of oxidative base lesions
detected in the patient population. The mechanism by which such stress is
generated is still something of an unresolved mystery.
If we do not understand the etiology of DNA damage, then there is little
we can do to treat this condition or prevent it from arising. However, we can
try to develop strategies for limiting the impact of such damage on human
embryos conceived in vitro including antioxidant therapy (Chap. 30), electro-
phoretic sperm isolation (Chap. 29), and the selective binding properties of
hyaluronic acid polymers (Chap. 28), all of which help select non-DNA dam-
aged spermatozoa for the insemination of oocytes.
The importance of developing strategies for avoiding conception with
DNA damaged spermatozoa is generally supported by the clinical data,
although the results are not always as clean cut as one would like (Chaps. 31
and 32). A major problem with such clinical studies is that pregnancy is a
very bad test of sperm function because it depends on so many confounding
variables. By contrast, the animal data are incontrovertible in demonstrating
that DNA damage in the male germ line has profound, lasting effects on the
viability of pregnancy and the health of the offspring (Chap. 33). In light of
such certainty, it is critical that the information available on this topic is
assembled and presented for careful consideration. Agarwal and Zini have
done a remarkable job of pulling together the protagonists in this field and
creating a compendium of knowledge that will be of intense interest to clini-
cians and scientists who share an appreciation of the significant contributions
made by the male gamete to a healthy start to life.
Callaghan, NSW R. John Aitken, PhD, ScD, FRSE

Preface

The evaluation of sperm DNA and chromatin abnormalities has gained
significant importance in the past several years, largely as a result of the
recent advances in assisted reproductive technologies (ARTs). In vitro fertil-
ization (IVF) and intracytoplasmic sperm injection (ICSI) have revolution-
ized the treatment of male-factor infertility. However, we have come to realize
that in the context of these ARTs, the genetic integrity of the sperm is a key
aspect of the paternal contribution to the offspring. With the growing concerns
about the long-term safety of ARTs (especially ICSI), we have seen an
increasing number of studies on the male genome’s influence on reproductive
outcomes. These studies now shed some light on the influence of sperm chro-
matin and DNA abnormalities on reproductive outcomes. Along with these
clinical studies, we also have made real advances in our understanding of the
basic aspects of sperm chromatin and DNA integrity. We are now starting to
better understand the unique organization of the sperm chromatin, as well as
the nature and etiology of sperm DNA damage.
We assembled this textbook with the idea of bringing together the key
fundamental and practical elements of this rapidly evolving efi ld. The 34
chapters in our book and four supplementary sections covering test protocols
and guidelines are written by contributors from 16 countries. These authors
were carefully selected based on their expertise and proven track record of
high-quality research in the efi ld. Our book is intended for researchers and
clinicians alike and is meant to bridge the gap between our basic and clinical
knowledge on sperm chromatin and DNA integrity. For the basic scientist,
this textbook will serve as a sound foundation for any further studies in this
efi ld. For the clinician, this book will help guide clinical practice in this area.
We would like to thank Richard Lansing, executive editor, for his support
and advice and Margaret Burns, developmental editor, for her tireless efforts in
reviewing and editing each of the manuscripts. Furthermore, we would like to
thank all of the outstanding contributors for sharing their knowledge and for
submitting their manuscripts on time. Finally, we are indebted to our families
who have endured many long nights when we were working late on this book.
Montreal, QC Armand Zini
Cleveland, OH Ashok Agarwal
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