Robert John Aitken

• PhD, ScD, FAHMS, FRSN, FRSE, FAA
• Pro Vice Chancellor, Faculty of Health and Medicine at University of Newcastle Australia

Context Equine reproductive technologies are crucial for overcoming challenges in natural fertilisation, particularly in sub-fertile stallions and breeding programs focused on genetic conservation and performance enhancement. Assisted reproductive technologies (ARTs), such as artificial insemination (AI), intracytoplasmic sperm injection (ICSI), an...

Oxidative stress, characterized by an imbalance between prooxidants and antioxidants in favor of the former, can lead to cellular damage due to the accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). In spermatozoa, oxidative stress plays a crucial role in signaling pathways associated with capacitation, a process ess...

(1) Background: The RoXstaTM system has been developed as a rapid, effective means of profiling different types of antioxidant activity. The purpose of this study was to examine its performance utilizing a diverse array of biological fluids including semen, blood plasma, serum, urine, saliva, follicular fluid and plant extracts. (2) Methods: The Ro...

(1) Background: The RoXstaTM system has been developed as a potential diagnostic tool to profile the antioxidant activity of complex biological fluids. (2) Methods: This methodology was used to assess the ability of different biofluids (semen, blood plasma, serum, urine, saliva, follicular fluid and plant extracts) to suppress free radical formatio...

(1) Background: This study set out to develop a series of simple, novel, rapid methods for assessing different forms of antioxidant activity. (2) Methods: An ABTS platform was used to engineer: (i) an electrochemical post-activation assay to assess free radical scavenging activity; (ii) an electrochemical pre-activation strategy to assesses the sup...

The lipidomic secretions of embryos provide a unique opportunity to examine the cellular processes of the early conceptus. In this study we profiled lipids released by the early equine conceptus, using high-resolution mass spectrometry to detect individual lipid species. This study examined the lipidomic profile in embryo-conditioned media from in...

This Directions article examines the mechanisms by which a father’s age impacts the health and wellbeing of his children. Such impacts are significant and include adverse birth outcomes, dominant genetic conditions, neuropsychiatric disorders, and a variety of congenital developmental defects. As well as age, a wide variety of environmental and lif...

In vitro semen purification techniques have been developed that seek to mimic the in vivo selection process in order to generate the highest possible chance of oocyte fertilization following artificial insemination. Numerous methods have been developed to isolate functional spermatozoa for artificial insemination, yet only one method, single-layer...

Background The escalating prevalence of fertility problems in the aging population necessitates a comprehensive exploration of contributing factors, extending beyond environmental concerns, work‐related stress, and unhealthy lifestyles. Among these, the rising incidence of testicular disorders emerges as a pivotal determinant of fertility issues. C...

Study question Does an electrophoretically sperm isolation method, the Felix™ system, have clinical or operational advantages over the combined density gradient centrifugation and swim-up (DGCS) method? Summary answer The Felix™ system produces results that are comparable to the DGCS method, however, Felix™ has the ability to isolate spermatozoa m...

Study question What is the impact of escalating doses of common water-soluble antioxidant nutrients on semen parameters and fertility in healthy (CD1) and stressed (Gpx5-/-) mice? Summary answer High-dose supplementation of previously “thought-to-be-safe” common water-soluble antioxidant nutrients can cause significant DNA damage/impaired fertilit...

In Brief In many mammals, the lipid platelet-activating factor (PAF) has important functions in female reproduction and fertility. This study shows that PAF is present in the reproductive tissues of mares and is involved in processes related to ovulation and early pregnancy. Abstract Platelet-activating factor (PAF) has been implicated in a number...

The in vitro storage of stallion spermatozoa for use in artificial insemination leads to oxidative stress and imbalances in calcium homeostasis that trigger the formation of the mitochondrial permeability transition pore (mPTP), resulting in premature cell death. However, little is understood about the dynamics and the role of mPTP formation in mam...

An intense period of human population expansion over the past 250 years is about to cease. Total fertility rates are falling dramatically all over the world such that highly industrialized nations, including China and the tiger economies of SE Asia, will see their populations decline significantly in the coming decades. The socioeconomic, geopoliti...

BACKGROUND The widespread interest in male reproductive health (MRH), fueled by emerging evidence, such as the global decline in sperm counts, has intensified concerns about the status of MRH. Consequently, there is a pressing requirement for a strategic, systematic approach to identifying critical questions, collecting pertinent information, and u...

The surgical sterilization of cats and dogs has been used to prevent their unwanted breeding for decades. However, this is an expensive and invasive procedure, and often impractical in wider contexts, for example the control of feral populations. A sterilization agent that could be administered in a single injection, would not only eliminate the ri...

In brief Over the past half century, the world has witnessed an unprecedented decline in human fertility rates. This analysis reviews the various socioeconomic, cultural, and biological factors involved in driving this change and considers whether low fertility rates are a temporary or permanent feature of our future demographic profile. Abstract...

Over the past half a century many countries have witnessed a rapid fall in total fertility rates, particularly in the world’s most advanced economies including the industrial powerhouses of Eastern Asia and Europe. Such nations have now passed through the first and second demographic transitions and are currently exhibiting fertility rates well bel...

Exposure to systemic heat stress in mammals adversely affects sperm production, male fertility, and DNA integrity. To date, few studies have investigated this phenomenon in horses, particularly in industry-relevant environments. Therefore, this study examined the relationship between ambient climatic conditions and fertility within a population of...

Cryopreservation of human spermatozoa is a necessity for males suffering from infertility who cannot produce fresh semen for insemination. However, current ART cryopreservation protocols are associated with losses of sperm motility, vitality and DNA integrity, which are thought to be linked to the induction of oxidative damage and the toxic propert...

Over the last half century, the world has seen a steep decline in fertility in virtually every country on Earth, with the result that most advanced industrialized societies now have fertility rates that are well below replacement levels (conventionally set at 2.1 children per woman). This decline in fertility has been particularly marked in the Tig...

Background Sperm DNA integrity is increasingly seen as a critical characteristic determining reproductive success, both in natural reproduction and in assisted reproductive technologies (ART). Despite this awareness, sperm DNA and nuclear integrity tests are still not part of routine examinations for either infertile men or fertile men wishing to a...

The surgical sterilization of cats and dogs has been used to prevent their unwanted breeding for decades, but this is an expensive and invasive procedure, and often impractical in wider contexts, for example the control of feral populations. A sterilization agent that could be administered in a single injection would not only eliminate the risks im...

In modern post-transition societies, we are reproducing later and living longer. While the impact of age on female reproductive function has been well studied, much less is known about the intersection of age and male reproduction. Our current understanding is that advancing age brings forth a progressive decline in male fertility accompanied by a...

Nanoparticles have gained considerable attention as one of the pollutants released into the environment through consumer products. This study describes the sub-chronic and generational effects of TiO2 (rutile) nanoparticles on earthworms over a 252-day duration, with exposure ranging from 0.1 to 1000 mg kg-1. Results indicate that sub-chronic expos...

Study question Do common chemicals in plastic, BPAF and DBP, negatively impact sperm parameters and DNA integrity, and can oral antioxidant supplementation mitigate their impact? Summary answer Short-term, low-dose exposure to BPAF or DBP did not impact testicular/epididymal histology but caudal epididymal sperm parameters, particularly DNA integr...

Oxidative stress can be induced in the testes by a wide range of factors, including scrotal hyperthermia, varicocele, environmental toxicants, obesity and infection. The clinical consequences of such stress include the induction of genetic damage in the male germ line which may, in turn, have serious implications for the health and wellbeing of the...

Routine exposure to chemicals omnipresent in the environment, particularly the so-called endocrine-disrupting chemicals (EDCs), has been associated with decreased sperm quality and increased anomalies in testis. The decline in semen quality and testicular abnormalities have been attributed to the disruption of endocrine signaling as well as oxidati...

The present study focuses on the effects of TiO2 and ZnO nanoparticles to the earthworm, Eisenia fetida. Upon 48 h of exposure of earthworms to TiO2/ ZnO nanoparticles in filter paper (0.1, 1, 10, 100, 500, 1000 mg L−1), no acute toxicity was evidenced. Two soil types (sandy loam soil and clay loam soil) with different characteristics were used in...

Simple Summary The outcome of equine artificial inseminations can be predicted with a high level of accuracy—87.9% if analyzed pre-chilling, and 95% if analyzed post-chilling—by optimizing a fertility prediction algorithm for individual stallions in conjunction with the Samson™ system and the reduction of the probe WST-1. Abstract This study aimed...

Mutations in the type III receptor tyrosine kinase FLT3 are frequent in patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. AML is characterized by the overproduction of reactive oxygen species (ROS), which can induce cysteine oxidation in redox-sensitive signaling proteins. Here, we sought to characterize the speci...

Organoid technology has provided a unique opportunity to study early human development and decipher various steps involved in the pathogenesis of disease. The technology is already used in clinics to improve human patient outcomes. However, limited knowledge of the methodologies required to establish organoid culture systems in domestic animals has...

Sperm cryopreservation is a valuable tool for the long-term preservation of male fertility. Thus, determining the optimal technique for isolating spermatozoa post-thaw is vital to ensure recovery of the highest quality spermatozoa with minimal iatrogenic damage. This not only enhances the chances of successful conception but also reduces the risk o...

This review surveys the causes and consequences of DNA damage in the male germ line from spermatogonial stem cells to fully differentiated spermatozoa. Within the stem cell population, DNA integrity is well maintained as a result of excellent DNA surveillance and repair; however, a progressive increase in background mutation rates does occur with p...

The cryopreservation of spermatozoa is an important reproductive technology for the preservation of fertility in man and animals. Since the serendipitous discovery of glycerol as an effective cryoprotectant in 1947, sperm cryopreservation has undergone many changes in terms of the freezing methods employed, the rates at which samples are frozen and...

Purpose Developing optimized techniques for the isolation of human spermatozoa possessing low levels of DNA damage is an important objective for the ART industry. The purpose of this study was to compare a novel electrophoretic system (Felix™) of sperm isolation with a conventional method involving density gradient centrifugation (DGC). Methods Fi...

In brief: A capacity to predict the likelihood of pregnancy following natural matings would be of considerable benefit to the Thoroughbred horse breeding industry. In this article, we describe a strategy for achieving this outcome through the analysis of dismount samples, that achieved an overall accuracy of 94.6%. Abstract: The purpose of this...

Organoid technology has provided us with a unique opportunity to study early human development and decipher various steps involved in the pathogenesis of human diseases. The technology is already used in clinics to improve human patient outcomes. However, limited knowledge of the methodologies required to establish organoid culture systems in domes...

In brief Post-ovulatory ageing of oocytes leads to poor oocyte and embryo quality as well as abnormalities in offspring. This review provides an update on the contributions of oxidative stress to this process and discusses the current literature surrounding the use of antioxidant media to delay post-ovulatory oocyte ageing. Abstract Following ovul...

Biomedical science is rapidly developing in terms of more transparency, openness and reproducibility of scientific publications. This is even more important for all studies that are based on results from basic semen examination. Recently two concordant documents have been published: the 6th edition of the WHO Laboratory Manual for the Examination a...

Over the past decade, mounting evidence has shown an alarming association between male subfertility and poor somatic health, with substantial evidence supporting the increased incidence of oncological disease, cardiovascular disease, metabolic disorders and autoimmune diseases in men who have previously received a subfertility diagnosis. This parad...

Lipid/polymer hybrid nanoparticles loaded with red fluorescent protein (RFP) encoded plasmid DNA (pDNA) was formulated using poly-lactic-co-glycolic acid (PLGA), cationic lipid DC-cholesterol and surfactant mPEG2000- DSPE. A lipid/ polymer ratio of 1: 10 at 1 mg/ mL surfactant concentration was found to be optimal for producing nanoparticles with d...

In brief Many aspects of the reproductive process are impacted by oxidative stress. This article summarizes the chemical nature of reactive oxygen species and their role in both the physiological regulation of reproductive processes and the pathophysiology of infertility. Abstract This article lays out the fundamental principles of oxidative stres...

In brief Oxidative stress is recognized as an underlying driving factor of both telomere dysfunction and human subfertility/infertility. This review briefly reassesses telomere integrity as a fertility biomarker before proposing a novel, mechanistic rationale for the role of oxidative stress in the seemingly paradoxical lengthening of sperm telomer...

The gathering storm – the creation of an Infertility TrapWhile previous publications have looked at individual aspects of the issues shaping our population size, the reality is that many different factors are working together to drive human fertility into a cul-de-sac of its own making. From a social perspective many young people, particularly youn...

Prologue- the pending collapse of human populationsA perfect storm of social, political, environmental and biological factors is conspiring to suppress the fertility of our species. In this book, we shall explore the fundamental nature of human population dynamics and the wide range of factors responsible for the change that is about to come. Socie...

The miracle of conception – how we all got to be here Successful conception requires spermatozoa to exhibit a wide range of sophisticated behaviours and biochemical changes. They are capable of exhibiting rheotaxis, thermotaxis and chemotaxis on their voyage to the site of fertilization in the oviduct. Once these cells have successfully engaged the...

Female fertility: hostage to affluence, age and the search for self-fulfilment In modern industrialized societies female fertility is compromised due to a perfect storm of social, economic, educational and political factors that far outweigh any attempt by Governments to encourage women to have more children. In affluent societies, there is no need...

Why are men infertile?Oxidative stress is one of the major causes of male infertility can be induced by a wide range of biological (age), clinical (varicocele), lifestyle (diet) and environmental (electromagnetic radiation and chemical pollutants) factors. Oxidative stress may impact all aspects of spermatogenesis but is particularly damaging when...

How do we escape the trap?Many of the social, biological and environmental mechanisms that are driving down human fertility, are self-reinforcing. They operate to accelerate the rate of fertility loss, not stabilize it. Escape from this downward spiral will involve several initiatives that, working together, may provide a measure of control over th...

The Janus faces of IVFIn vitro fertilization therapy was originally pioneered by Edwards, Steptoe and Purdy in order to help women suffering from bilateral tubal occlusion. The subsequent rise of Assisted Reproductive Therapy (ART) as a default treatment for many different forms of human infertility has been successful to the point that it has now...

What is happening to the human male?Something strange is happening to the human male. The incidence of testicular cancer is increasing dramatically in all the advanced economies on Earth, male infertility has reached epidemic proportions, sperm counts are declining at an alarming rate and paternal impacts on offspring health are becoming increasing...

A journey into the demographic heart of the matterDespite 300 years of unrelenting population growth, the world is now witnessing an unprecedented decline in human fertility. Counterintuitively, the global population continues to grow because infant mortality rates are low, lifespan is increasing, and population momentum is high. The net effect of...

A potential crisis in human fertility is brewing. As societies become more affluent, they experience changes that have a dramatic impact on reproduction. As average family sizes fall, the selection pressure for high-fertility genes decreases; exacerbated by the IVF industry which allows infertility-linked genes to pass into the next generation. Mal...

FLT3-mutations are diagnosed in 25-30% of patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. AML is associated with the overproduction of reactive oxygen species (ROS), which drives genomic instability through the oxidation of DNA bases, promoting clonal evolution, treatment resistance and poor outcomes. ROS are al...

Spermatogonial stem cells exhibit a low level of spontaneous mutation that is heavily impacted by paternal age via mechanisms that appear to involve the aberrant repair of DNA damage. This background de novo mutation frequency can be increased 1000 fold by mutations affecting a key signal transduction pathway which confers upon its descendants a se...

MTT is a commonly used cell vitality probe, due to its ability to form insoluble formazan deposits at cellular locations of intense oxidoreductase activity. Although this response is considered a reflection of mitochondrial redox activity, extra-mitochondrial sites of MTT reduction have been recognized within the spermatozoa of several mammalian sp...

Breeding soundness examinations (BSEs) for bulls rely heavily on the subjective, visual assessment of sperm motility and morphology. Although these criteria have the potential to identify infertile males, they cannot be used to guarantee fertility or provide information about varying degrees of bull fertility. Male factor fertility is complex, and...

Reactive oxygen species (ROS) play a critical role in defining the functional competence of human spermatozoa. When generated in moderate amounts, ROS promote sperm capacitation by facilitating cholesterol efflux from the plasma membrane, enhancing cAMP generation, inducing cytoplasmic alkalinization, increasing intracellular calcium levels, and st...

Male infertility is a relatively common condition responsible for around 30% of all infertility cases and contributing to another 20%. Although the traditional semen profile is used to diagnose this condition, the criteria at the heart of this analysis are purely descriptive and shed no light on the underlying aetiology. Recent research on the caus...

Lipids are dynamic biological molecules that play key roles in metabolism, inflammation, cell signalling and structure. They are biologically significant in the physiology of conception and reproduction. Many of the mechanisms surrounding equine conception and the early feto-maternal dialogue are yet to be understood at a biochemical level. Recentl...

Over the past half-century, the world has witnessed a steep decline in fertility rates in virtually every country on Earth. This universal decline in fertility is being driven by increasing prosperity largely through the mediation of social factors, the most powerful of which are the education of women and an accompanying shift in life’s purpose aw...

Stallions experience transient fluctuations in fertility throughout the breeding season. Considering pregnancy diagnoses cannot be ascertained until ~14 days post-breeding, the timely detection of decreases in stallion fertility would enhance industry economic and welfare outcomes. Therefore, this study aimed to identify the proteomic signatures re...

Among the two hundred or so cell types that make up mammals, spermatozoa have an ambiguous relationship with the reactive oxygen species (ROS) inherent in the consumption of oxygen that supports aerobic metabolism. In this review, we shall see that on the one hand, spermatozoa need the action of ROS to reach their structural and functional maturity...

A growing body of research has confirmed that nanoparticle (NP) systems can enhance delivery of therapeutic and imaging agents as well as prevent potentially damaging systemic exposure to these agents by modifying the kinetics of their release. With a wide choice of NP materials possessing different properties and surface modification options with...

Anthropogenic chemical pollution has the potential to pose one of the largest environmental threats to humanity, but global understanding of the issue remains fragmented. This article presents a comprehensive perspective of the threat of chemical pollution to humanity, emphasising male fertility, cognitive health and food security. There are seriou...

Background The seminal vesicles synthesise bioactive factors that support gamete function, modulate the female reproductive tract to promote implantation, and influence developmental programming of offspring phenotype. Despite the significance of the seminal vesicles in reproduction, their biology remains poorly defined. Here, to advance understand...

Background: The use of flow cytometry (FC) to evaluate sperm DNA fragmentation via deoxynucleotidyl transferase terminal fluorescein dUTP nick-end labeling (TUNEL) has shown inconsistencies compared with conventional fluorescent microscopic analyses. It has been hypothesized that the observed discrepancies could be attributed to the presence of ap...

Stallion sperm membranes comprise a high proportion of polyunsaturated fatty acids, making stallion spermatozoa especially vulnerable to peroxidative damage from reactive oxygen species generated as a by-product of cell metabolism. Membrane lipid replacement therapy with glycerophospholipid (GPL) mixtures has been shown to reduce oxidative damage i...

The world was first alerted to the existence of a novel coronavirus (COVID-19) on December 31st, 2019. In the 2 years that have elapsed since the beginning of this outbreak, sporadic reports have emerged of an impact on male reproductive health. It is now timely to look at this information to see what conclusions can be drawn. The evidence collecte...

Seminal vesicles are an integral part of the male reproductive accessory gland system. They produce a complex array of secretions containing bioactive constituents that support gamete function and promote reproductive success, with emerging evidence suggesting these secretions are influenced by our environment. Despite their significance, the biolo...

Selecting good-quality sperm for use in in-vitro fertilization is a key step in assisted reproduction. For many years purely morphological attributes have been used to assess suitability, but increasingly biochemical and molecular biological techniques are now identifying sperm with the best chances of producing viable and healthy embryos. Focusing...

This new edition provides a much-needed reference book to accommodate emerging and expanding knowledge in fertility preservation, the rapidly growing field of reproductive medicine associated with advances in oncology. Written by a team of world-leading experts in the field and comprehensive in its scope, the book covers the full range of technique...

Assessments of sperm DNA damage are controversial because of perceived uncertainties over the relationship with pregnancy and the limited range of therapies available should positive results be returned. In this article, we highlight recent data supporting a chain of associations between oxidative stress in the male germ line, DNA damage in spermat...

Evidence is presented for expression of the insulin receptor on the surface of mammalian spermatozoa as well as transcripts for the receptor substrate adaptor proteins (IRS1-4) needed to mediate insulin action. Exposure to this hormone resulted in insulin receptor phosphorylation (pTyr972), activation of AKT (pSer473) and the stimulation of sperm m...

Oxidative stress generates a large amount of reactive oxygen species (ROS) and affects sperm quality via damaging sperm DNA and compromising the intracellular homeostasis in human spermatozoa. In assisted reproductive technology (ART), it is substantial to prevent spermatozoa from ROS attack. The pineal hormone melatonin has the natural antioxidant...

A unique opportunity to conduct a longitudinal analysis of semen quality in a male subject immediately before, during and after COVID-19 infection, has revealed new insights into the impact of this virus on male reproductive function. A moderate COVID infection that did not require hospitalization resulted in a state of azoospermia that persisted f...

A prevalent cause of sperm dysfunction in male infertility patients is the overproduction of reactive oxygen species, an attendant increase in lipid peroxidation and the production of cytotoxic reactive carbonyl species such as 4-hydroxynonenal. Our previous studies have implicated arachidonate 15-lipoxygenase (ALOX15) in the production of 4-hydrox...

Due to their antimicrobial activity, parabens are commonly used as preservatives in a variety of consumer goods- including cosmetics, pharmaceuticals, and personal care products. During the production, usage and disposal of these products, parabens are released into the environment. In this study, the persistence of three widely used parabens; meth...

Spermatogonial stem cells (SSCs) are generally characterized by excellent DNA surveillance and repair, resulting in one of the lowest spontaneous mutation rates in the body. However, the barriers to mutagenesis can be overwhelmed under two sets of circumstances. First, replication errors may generate age-dependent mutations that provide the mutant...

Male infertility is recognized as a relatively common, complex condition, generated by a broad array of environmental and genetic factors. Historical reliance on the conventional semen profile has tended to underestimate the true contribution of “the male factor” to human infertility. This review highlights the importance of genetic and epigenetic...