The impact of mitochondrial impairments on sperm function and male fertility: a systematic review.

BACKGROUND: Besides adenine triphosphate (ATP) production for sustaining motility, the mitochondria of sperm also host other critical cellular functions during germ cell development and fertilization including calcium homeostasis, generation of reactive oxygen species (ROS), apoptosis, and in some cases steroid hormone biosynthesis. Normal mitochondrial membrane potential with optimal mitochondrial performance is essential for sperm motility, capacitation, acrosome reaction, and DNA integrity. RESULTS: Defects in the sperm mitochondrial function can severely harm the fertility potential of males. The role of sperm mitochondria in fertilization and its final fate after fertilization is still controversial. Here, we review the current knowledge on human sperm mitochondria characteristics and their physiological and pathological conditions, paying special attention to improvements in assistant reproductive technology and available treatments to ameliorate male infertility. CONCLUSION: Although mitochondrial variants associated with male infertility have potential clinical use, research is limited. Further understanding is needed to determine how these characteristics lead to adverse pregnancy outcomes and affect male fertility potential.

Testosterone restores TM3 and TM4 cell viability, reduces reactive oxygen species generation, and protects against atrazine-induced stereological changes in rat testes.

In this study, we performed the stereological examination of rat testes and evaluated the protective effect of testosterone against atrazine (ATZ) toxicity in TM3 Leydig and TM4 Sertoli cells. Testosterone intake in rats increased the volumetric density of the seminiferous tubules; tubular diameter; germinal epithelial height; number of spermatogonia, primary and secondary spermatocytes, round spermatids, Sertoli cells, and Leydig cells; and Johnsen scores compared with the values after ATZ treatment (p < 0.05). Furthermore, testosterone increased the viability of TM3 cells and reduced reactive oxygen species (ROS) generation in TM4 cells compared to the ATZ-treated group. In conclusion, exogenous testosterone intake maintains testicular morphometry and spermatogenesis in rats, and minimizes cell death and ROS generation in testicular cell lines exposed to ATZ. However, TM4 cells are more responsive to testosterone-mediated regulation of ROS generation induced by ATZ than TM3 cells.

Male infertility.

It is estimated that infertility affects 8-12% of couples globally, with a male factor being a primary or contributing cause in approximately 50% of couples. Causes of male subfertility vary highly, but can be related to congenital, acquired, or idiopathic factors that impair spermatogenesis. Many health conditions can affect male fertility, which underscores the need for a thorough evaluation of patients to identify treatable or reversible lifestyle factors or medical conditions. Although semen analysis remains the cornerstone for evaluating male infertility, advanced diagnostic tests to investigate sperm quality and function have been developed to improve diagnosis and management. The use of assisted reproductive techniques has also substantially improved the ability of couples with infertility to have biological children. This Seminar aims to provide a comprehensive overview of the assessment and management of men with infertility, along with current controversies and future endeavours.

Standards in semen examination: publishing reproducible and reliable data based on high-quality methodology.

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 and Processing of Human Semen, and the International Standard ISO 23162:2021. With these tools, we propose that authors should be instructed to follow these laboratory methods in order to publish studies in peer-reviewed journals, preferable by using a checklist as suggested in an Appendix to this article.

Predictive value of seminal oxidation-reduction potential analysis for reproductive outcomes of ICSI.

RESEARCH QUESTION: Is seminal oxidation-reduction potential (ORP) clinically relevant to reproductive outcome? DESIGN: Prospective observational study including a total of 144 couples who had an intracytoplasmic sperm injection (ICSI) cycle between June 2018 and December 2020. The study included patients undergoing fresh ICSI cycles with autologous gametes. Cycles that had day 3 embryo transfers and cryopreservation cycles were excluded. There was no restriction on patients with severe male infertility; couples with unexplained infertility and unexplained male infertility were included, those with azoospermia were excluded. Semen analysis, seminal ORP as determined by means of the MiOXSYS system, sperm DNA fragmentation (SDF) and reproductive outcomes (fertilization, blastocyst development, clinical pregnancy and live birth) were determined. RESULTS: Seminal ORP was significantly negatively correlated with fertilization rate (r = -0.267; P = 0.0012), blastocyst development rate (r = -0.432; P < 0.0001), implantation/clinical pregnancy (r = -0.305; P = 0.0003) and live birth (r = -0.366; P < 0.0001). Receiver operating characteristic curve analysis showed significant predictive power for ORP for fertilization (≥80%; area under the curve [AUC] 0.652; P = 0.0012), blastocyst development rate (≥60%; AUC 0.794; P < 0.0001), implantation/clinical pregnancy (AUC 0.680; P = 0.0002) and live birth (AUC 0.728; P < 0.0001). Comparable results were obtained for SDF (fertilization: AUC 0.678; blastocyst development: AUC 0.777; implantation/clinical pregnancy: AUC 0.665; live birth: AUC 0.723). Normal sperm morphology showed the lowest predictive power for all reproductive outcome parameters. With male age as confounding factor, ORP (cut-off value of 0.51 mV/106 sperm/ml) has significant (P < 0.04667) effects on odds ratios for all reproductive outcome parameters. Multivariate logistic regression to investigate potential seminal and female confounding factors revealed that seminal ORP significantly (P < 0.0039; P < 0.0130) affects reproductive outcome. CONCLUSION: Seminal ORP is relevant for good fertilization, blastocyst development, implantation, clinical pregnancy and live birth.

Oxidative Stress and Toxicity in Reproductive Biology and Medicine: Historical Perspectives and Future Horizons in Male Fertility.

Since the discovery by John MacLeod in 1943 that spermatozoa produce small amounts of hydrogen peroxide, a member of the so-called reactive oxygen species (ROS), the importance and functions of these highly reactive oxygen derivatives in physiology and pathology are a subject of numerous studies. It has been shown that they play essential roles, not only in causing oxidative stress if their concentration is excessively high, but also in triggering crucial cellular functions if their concentration is low. On the other hand, antioxidants counterbalance the action of ROS to maintain a fine balance between oxidation and reduction as an excessive amount of antioxidants leads to a condition called reductive stress and is as harmful as oxidative stress. This book "Oxidative Stress and Toxicity in Reproductive Biology and Medicine - A Comprehensive Update on Male Infertility" authoritatively summarizes the current knowledge of various causes of oxidative stress including various andrological conditions and environmental pollution as well as the physiological effects of ROS. Moreover, this book expands into the treatment of oxidative stress with antioxidants and phytomedicine, a rapidly developing area. As a first of its kind, this book also sheds light on the effects of the redox potential during the fertilization process and thus highlights the importance of the correct balance of oxidants and antioxidants, even in the culture medium in assisted reproduction. The editors have brought together an impressive group of renowned experts to share their knowledge on the topic of oxidative stress and its clinical management in andrology and assisted reproduction.

Oxidative Stress and Toxicity in Reproductive Biology and Medicine: A Comprehensive Update on Male Infertility Volume II - Conclusion.

Infertility is a globally under-recognized public health problem significantly impacting individual health and socioeconomics affecting millions of couples. The reasons for infertility are manifold and not only include many couples decision to postpone having children but also diseases (e.g., diabetes, infections, or varicocele), lifestyle (e.g., obesity), and environmental factors (e.g., bisphenol A, DTT or dioxin). In the pathology of many causes of infertility, oxidative stress plays a significant role as reactive oxygen species (ROS) exert significant detrimental effects. On the other hand, a small amount of ROS is essential to trigger physiological events such as capacitation. Therefore, a fine balance between oxidation and reduction has to be maintained. Apart from treating the underlying disease or correcting the cause of the infertility, oxidative stress can be treated by antioxidant supplementation. Since plants and their extracts contain numerous phytochemicals which exhibit antioxidant activity, many people tend to use herbal products. Alternatively, isolated antioxidants such as vitamin C or E are also used. However, when using purified antioxidants, it is essential that the redox balance is maintained to avoid a "reductive stress" situation, which is as harmful as oxidative stress.

Role of Infection and Leukocytes in Male Infertility.

Male infertility is considered as a multifactorial complex reproductive illness, and male urogenital infection and inflammation are crucial etiologies contributing up to 35% of all cases. Mostly triggered by sexually transmitted diseases and uropathogens, chronic manifestation of such infection may cause irreversible infertility in the male. Male urogenital infection involves bacterial, viral, protozoal, and fungal infections many of which remain asymptomatic most of the time and are passed to the sexual partner leading to fertilization failure, pregnancy loss, and even development of illness in the offspring. The abundance of leukocytes in semen can be used as an indicator of urogenital infection. Its contribution in male infertility can be as high as 30% and the clinical condition is referred to as leukocytospermia. Seminal bacterial load together with increased leukocytes contribute to the impairment of male fertility parameters such as, sperm motility, DNA integrity, acrosome reaction, and damage sperm molecular structure. Pathophysiology of bacteriospermia-induced impairment of male infertility is probably mediated by the involvement of bacterial pathogens in the intrinsic apoptotic pathway resulting in sperm death, whereas that of seminal leukocytes operates through excessive generation of ROS. Although the application of antibiotics forms the frontline therapeutic approach, the growing resistance to antibiotics poses a concern in the management of microbes-induced male urogenital infection. Complementary and alternative medicine may offer additional management options in combating such infections. On the other hand, both broad spectrum antibiotics and antioxidant therapy have showed promising results in the management of infertile men with leukocytospermia. Use of herbal medicine may also play a promising role in the management of such patients. However, recent molecular biology techniques have noted the association of elevated levels of IL-8 with both the Chlamydial infection of the male urogenital tract as well as the clinical condition of leukocytospermia. On the basis of such common pathogenesis, further research involving advanced molecular techniques may pave the way towards the development of better diagnostic tools in the clinical management of male urogenital infection and leukocytospermia.

In vitro effects of aqueous extract of unfermented rooibos on human spermatozoa.

The inability to conceive is a baleful experience for thousands of couples worldwide. Among different well-known reproductive techniques, medicinal plants have been utilized to treat male infertility. Medicinal plants, provide a therapeutic alternative, which is available and affordable for infertile couples. We investigated the direct effect of unfermented rooibos aqueous extract on human spermatozoa. Semen samples (n = 50) collected from donors and patients consulting for fertility were reassigned as normal (n = 22) and abnormal (n = 28) samples based on the outcome of the baseline semen analysis, using the World Health Organization (WHO) cut off value. Semen samples were allowed to liquefy and subsequently washed with human tubular fluid in bovine serum albumin medium. The samples were then treated with aqueous extracts of unfermented rooibos (0, 0.15, 1.5, 15, 150 µg/ml) at 37°C for 1 h and assessed thereafter. Sperm motility, vitality, DNA fragmentation, intracellular reactive oxygen species and mitochondrial membrane potential in both groups remained unchanged (p > 0.05). However, aqueous extract of unfermented rooibos (only at 1.5 µg/ml) significantly increased capacitation and acrosome reaction in the abnormal sample group (p > 0.05). Unfermented rooibos aqueous extract had no deleterious impact on human spermatozoa's function and might be attributed to its antioxidant properties.

Association among sperm chromatin condensation, sperm DNA fragmentation and 8-OHdG in seminal plasma and semen parameters in infertile men with oligoasthenoteratozoospermia.

The present study aimed to investigate the clinical role of standard sperm diagnosis parameters (sperm concentration, motility, morphology) as well as aniline blue staining of histones, 8-OHdG, TUNEL assay were performed on semen samples in infertile men with oligoasthenoteratozoospermia (OAT). Thirty-two infertile and ten proven fertile men were included in the study. Chromatin condensation sperm in infertile men was significantly lower compared to the fertile men (p < 0.0001). Age, sperm concentration, morphology and motility were significantly negatively correlated with chromatin condensation (p < 0.05). However, no significant correlations among the chromatin condensation, SDF and sperm DNA damage were detected in terms of 8-OHdG concentration.

Polymorphisms of androgens-related genes and idiopathic male infertility in Turkish men.

Androgens, testosterone and dihydrotestosterone (DHT) are endocrine regulators of spermatogenesis and act via androgen receptor (AR). The aim of this study was to investigate the association(s) of AR (CAG repeat length), SRD5A2 (rs523349, V89L) and TNF-α (rs1800629, -308G/A) polymorphisms with idiopathic male infertility in Turkish men. This case-control study consisted of 312 men with idiopathic infertility and 113 fertile men. Polyacrylamide gel electrophoresis (PAGE) or PCR-restriction fragment length polymorphism methods were used for genotyping. The mean AR CAG repeat length was significantly longer in infertile men than in fertile men (p = 0.015). However, there was no significant association between the SRD5A2 genotypes (VV, VL and LL) and the risk of infertility (p = 0.516). The genotype frequency and allele distribution of TNF-α -308G/A polymorphism (GG, GA, AA genotypes and G, A alleles) were not associated with male infertility (p = 0.779 and p = 0.743 respectively). AR CAG repeat expansion might be one of the risk factors for idiopathic male infertility in Turkish men. Further studies investigating the association of male infertility with AR CAG, V89L and -308G/A polymorphisms are warranted to understand the possible associations among them.

A systemic review and meta-analysis exploring the predictors of sperm retrieval in patients with non-obstructive azoospermia and chromosomal abnormalities.

To identify the most prevalent chromosomal abnormalities in patients with non-obstructive azoospermia (NOA), consolidate their surgical sperm retrieval (SSR) rates and determine the significant predictors of positive SSR in this patient population. A systematic review and meta-analysis were performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Fifty-three studies including 2965 patients were identified through searching the PubMed database. Klinefelter Syndrome (KS) was the most prevalent chromosomal abnormality reported in 2239 cases (75.5%). Azoospermia factor c (AZFc) microdeletions were the second most common (18.6%), but men with these deletions had higher SSR rates than patients with KS (41.95% with AZFc vs. 38.63% with KS). When examining predictors of SSR in KS patients, younger age was a significant predictor of positive SSR in patients undergoing microsurgical testicular sperm extraction (micro-TESE). Higher testosterone was a favourable predictor in those undergoing micro-TESE and conventional TESE. Lower luteinizing hormone (LH) and follicular stimulating hormone (FSH) values were significantly associated with positive SSR with testicular sperm aspiration (TESA). No parameter predicted SSR rates in patients with AZFc microdeletions. Overall, genetic abnormalities have significant implications on SSR success in patients with NOA.

Effect of redo varicocelectomy on semen parameters and pregnancy outcome: An original report and meta-analysis.

Recurrence following varicocelectomy is an important cause of treatment failure and persistence of subnormal semen parameters. This original study was combined with a systemic review and meta-analysis aiming to evaluate the efficacy of redo varicocelectomy on male fertility potential and pregnancy outcome. The retrospective study included 32 patients who underwent microsurgical subinguinal varicocelectomy for patients with recurrent varicocele. Changes in semen parameters and hormone profiles before and after surgery were compared. The literature review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and included seven articles in addition to our original report. Results of the original study revealed statistically significant improvements in sperm concentration, progressive motility, total motile sperm count and normal morphology following redo varicocelectomy. The meta-analysis results echoed those reported in our original study and depicted significant improvements in sperm concentration (mean difference [MD] = +20.281 million/ml, p < 0.001), total motility (MD = +9.659%, p = 0.001), total motile sperm count (MD = +23.258 million sperm, p < 0.001) and normal morphology (MD = +4.460%, p < 0.001). Overall pregnancy outcome was reported in seven studies with a rate of 34.6%. No significant changes were noted in any of the collected hormone results both in this original report and in the meta-analysis. In conclusion, redo varicocelectomy has a beneficial role on male fertility potential and can be offered for men with recurrent varicocele as directed by their individual clinical condition.

ANXA2, SP17, SERPINA5, PRDX2 genes, and sperm DNA fragmentation differentially represented in male partners of infertile couples with normal and abnormal sperm parameters.

This study aims to evaluate the expression of genes associated with the fertilisation potential and embryo development, sperm DNA fragmentation (SDF), and acrosome reaction in male partners of infertile couples with different sperm parameters compared to fertile men. First, male partners of infertile couples with abnormal (N = 25) and normal sperm parameters (N = 25), and fertile men (N = 10) were included in experimental groups I, II, and controls respectively. The mRNA levels of the Annexin A2 (ANXA2), Sperm protein 17 (SP17), Plasma serine protease inhibitor (SERPINA5), and Peroxiredoxin-2 (PRDX2) genes and SDF were evaluated. To evaluate the maturity of the sperm and oxidative stress, the acrosome reaction, the lipid peroxidation, and total antioxidant were measured. As result, SP17 showed a significantly lower expression in both experimental groups. SERPINA5 was significantly down-regulated in experimental group I that was aligned with the low rate of acrosome reaction. Significant overexpression of PRDX2 was found between experimental group II and controls. Significant higher rates of SDF were seen in both experimental groups compared to the controls. Finally, our data suggest that differentially gene expression of SP17 is a potential diagnostic biomarker in infertile men either with normal or abnormal sperm parameters. SDF is one of the causes of male infertility, independent of the sperm parameters.

Environmental contaminants and male infertility: Effects and mechanisms.

The escalating prevalence of male infertility and decreasing trend in sperm quality have been correlated with rapid industrialisation and the associated discharge of an excess of synthetic substances into the environment. Humans are inevitably exposed to these ubiquitously distributed environmental contaminants, which possess the ability to intervene with the growth and function of male reproductive organs. Several epidemiological reports have correlated the blood and seminal levels of environmental contaminants with poor sperm quality. Numerous in vivo and in vitro studies have been conducted to investigate the effect of various environmental contaminants on spermatogenesis, steroidogenesis, Sertoli cells, blood-testis barrier, epididymis and sperm functions. The reported reprotoxic effects include alterations in the spermatogenic cycle, increased germ cell apoptosis, inhibition of steroidogenesis, decreased Leydig cell viability, impairment of Sertoli cell structure and function, altered expression of steroid receptors, increased permeability of blood-testis barrier, induction of peroxidative and epigenetic alterations in spermatozoa resulting in poor sperm quality and function. In light of recent scientific reports, this review discusses the effects of environmental contaminants on the male reproductive function and the possible mechanisms of action.

Diagnostic value of advanced semen analysis in evaluation of male infertility.

Conventional semen analysis is the standard of care to initially evaluate the fertility status of a male patient. However, it has some limitations and among these are failure to correctly identify the aetiology underlying fertility problems, intra- and inter-observer variability and incomplete information about sperm function. Considering these drawbacks, advanced semen tests have been developed to assess male infertility, including sperm function tests, oxidative stress (OS) and sperm DNA fragmentation (SDF) tests. This review illustrates the commonly utilised sperm function techniques, along with the assays used to assess SDF and OS and their diagnostic value.

Obesity and male infertility: Mechanisms and management.

Obesity is considered a global health problem affecting more than a third of the population. Complications of obesity include cardiovascular diseases, type 2 diabetes mellitus, malignancy (including prostatic cancer), neurodegeneration and accelerated ageing. In males, these further include erectile dysfunction, poor semen quality and subclinical prostatitis. Although poorly understood, important mediators of obesity that may influence the male reproductive system include hyperinsulinemia, hyperleptinemia, chronic inflammation and oxidative stress. Obesity is known to disrupt male fertility and the reproduction potential, particularly through alteration in the hypothalamic-pituitary-gonadal axis, disruption of testicular steroidogenesis and metabolic dysregulation, including insulin, cytokines and adipokines. Importantly, obesity and its underlying mediators result in a negative impact on semen parameters, including sperm concentration, motility, viability and normal morphology. Moreover, obesity inhibits chromatin condensation, DNA fragmentation, increases apoptosis and epigenetic changes that can be transferred to the offspring. This review discusses the impact of obesity on the male reproductive system and fertility, including associated mechanisms. Furthermore, weight management strategies, lifestyle changes, prescription medication, and complementary and alternative medicine in the management of obesity-induced subfertility is discussed.

Total antioxidant capacity-Relevance, methods and clinical implications.

Oxidative stress is pre-empted by an adequate level of antioxidants, which scavenge oxidants when they are produced in excess by different sources, including leukocytes and immature spermatozoa. Enzymatic antioxidants, such as superoxide dismutase, catalase and glutathione peroxidase, and several non-enzymatic antioxidants (proteins, vitamins and minerals), working as oxidant scavengers and cofactors of enzymatic antioxidants have been identified in seminal plasma. The total antioxidant capacity (TAC) is a diagnostic test that can be utilised in the male infertility workup. TAC measures the amount of total antioxidants in seminal plasma. Therefore, it provides an assessment of the reductive potential in seminal plasma. Several studies have investigated the diagnostic application of TAC in various andrology conditions. There is substantial evidence in the literature to show that infertile patients have lower seminal TAC in comparison with fertile men. Moreover, there is a positive correlation between TAC and seminal parameters, such as sperm concentration, motility and morphology. Evaluation of TAC together with reactive oxygen species (ROS) and sperm DNA fragmentation index (DFI) may be beneficial in the diagnosis of male infertility.

Diagnostic value of routine semen analysis in clinical andrology.

Infertility is a major health issue affecting over 48.5 million couples around the world, with the male factor accounting for about 50% of the cases. The conventional semen analysis recommended by the World Health Organization (WHO) is the cornerstone in the evaluation of male fertility status. It includes macroscopic and microscopic evaluation of the ejaculate, which reflects the production of spermatozoa in the testes, the patency of the duct system and the glandular secretory activity. Evaluation of seminal fructose, sperm vitality and leucocytes (Endtz test) are useful adjuncts to semen analysis that provide information on specific clinical conditions. Though several computer-assisted sperm analysis (CASA) systems have been developed, conventional methods for semen analysis are still widely accepted in clinical practice. This review summarises the conventional techniques used in routine semen analysis and their diagnostic value in clinical andrology.

Causes and consequences of sperm mitochondrial dysfunction.

Mitochondria have multiple functions, including synthesis of adenine triphosphate, production of reactive oxygen species, calcium signalling, thermogenesis and apoptosis. Mitochondria have a significant contribution in regulating the various physiological aspects of reproductive function, from spermatogenesis up to fertilisation. Mitochondrial functionality and intact mitochondrial membrane potential are a pre-requisite for sperm motility, hyperactivation, capacitation, acrosin activity, acrosome reaction and DNA integrity. Optimal mitochondrial activity is therefore crucial for human sperm function and semen quality. However, the precise role of mitochondria in spermatozoa remains to be fully explored. Defects in sperm mitochondrial function severely impair the maintenance of energy production required for sperm motility and may be an underlying cause of asthenozoospermia. Sperm mtDNA is susceptible to oxidative damage and mutations that could compromise sperm function leading to infertility. Males with abnormal semen parameters have increased mtDNA copy number and reduced mtDNA integrity. This review discusses the role of mitochondria in sperm function, along with the causes and impact of its dysfunction on male fertility. Greater understanding of sperm mitochondrial function and its correlation with sperm quality could provide further insights into their contribution in the assessment of the infertile male.