Male infertility: current concepts

Spermatotoxic Effects of Single-Walled and Multi-Walled Carbon Nanotubes on Male Mice

Carbon-based nanomaterials possess a remarkably high potential for biomedical applications due to their physical properties; however, their detrimental effects on reproduction are also concerned. Several reports indicate the toxicity of carbon nanotubes (CNT); nevertheless, their impact on intracellular organelles in the male reproductive organs has not been fully elucidated. Herein, we report on the reprotoxicity of single-walled (SWCNT) and multi-walled carbon nanotubes (MWCN) on several intracellular events and histological criteria in pubertal male BALB/c mice orally treated with 0, 10, and 50 mg/kg/day doses for 5 weeks. Biomarkers of oxidative stress and mitochondrial functionality, histopathological alterations, and epididymal sperm characteristics were determined. Oral administration of CNTs at 10 and 50 mg/kg evoked a significant decrement in weight coefficient, sperm viability and motility, hypo-osmotic swelling (HOS) test, sperm count, mitochondrial dehydrogenase activity, ATP content, total antioxidant capacity, and GSH/GSSH ratio in the testis and epididymal spermatozoa. On the other hand, percent abnormal sperm, testicular and sperm TBARS contents, protein carbonylation, ROS formation, oxidized glutathione level, and sperm mitochondrial depolarization were considerably increased. Significant histopathological and stereological alterations in the testis occurred in the groups challenged with CNTs. The current findings indicated that oxidative stress and mitochondrial impairment might substantially impact CNTs-induced reproductive system injury and sperm toxicity. The results can also be used to establish environmental standards for CNT consumption by mammals, produce new chemicals for controlling the rodent populations, and develop therapeutic approaches against CNTs-associated reproductive anomalies in the males exposed daily to these nanoparticles.

Repeated administrations of Mn3O4 nanoparticles cause testis damage and fertility decrease through PPAR-signaling pathway

Potential health hazards of nanomaterials on male reproductive system have received raising concerns. Even though Mn₃O₄ nanoparticles (Mn₃O₄-NPs) is highly effective in clinical diagnostic and therapeutic applications of human disease, its potential toxic effect on the male reproductive system has not been reported. In this study, the testis damage and fertility decrease of male rats were conducted to testify the experimental reproductive injury induced by Mn₃O₄-NPs. After repeated tail vein injection with 10 mg/kg/week Mn₃O₄-NPs for 0, 60 and 120 days, Mn₃O₄-NPs accumulated in the testes resulted in oxidative stress and disorder of normal serum sex hormones. Experiments in vivo and in vitro indicated that mitochondria-mediated cell apoptosis were triggered via oxidative stress, demonstrated by the upregulation of malondialdehyde (MDA) and the depolarization of mitochondrial membrane potential. Notably, Mn₃O₄-NPs significantly resulted in a reduction of the quantity/quality of sperm and finally caused astonishing fertility decrease. Our preliminary result implied that the application of Mn₃O₄-NPs could be a double-edged sword and careful consideration should be given to the clinical uses.

Exposure to PbSe Nanoparticles and Male Reproductive Damage in a Rat Model

PbSe nanoparticles (PbSe-NPs) attract ever-growing interest owing to their great promise in various fields. However, potential toxic effects of PbSe-NPs on male reproductive systems have not been reported. This study aimed to determine whether early-life exposure to PbSe-NPs could affect male reproductive systems and other related health effects in rats. The male rats were intraperitoneally injected with 10 mg/kg/week PbSe-NPs for 60 days followed by a series of reproductive-related analyses. We found that the nanoparticles could accumulate in testes in a size-dependent manner. Furthermore, accumulation of PbSe-NPs resulted in oxidative stress and disorder of normal serum sex hormones. Endoplasmic reticulum and mitochondria-mediated cell apoptosis were triggered via oxidative stress, as shown by upregulation of cytoplasmic Cyt-c, Bax, cleaved Caspase-3, GRP78, and Caspase-12. Notably, PbSe-NP administration led to reduction in the quantity and quality of sperm, which caused a great fertility decrease. In contrast, released Pb²⁺ from PbSe-NPs did not result in any testis toxicity and fertility declines. These results demonstrate that PbSe-NPs could cause severe reproductive toxicity in a size-dependent manner and these toxic effects should be responsible for PbSe-NPs themselves rather than released Pb²⁺. The application of PbSe-NPs might be a double-edged sword, and corresponding measures should be taken before use.

Prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium and Ureaplasma urealyticum infections using a novel isothermal simultaneous RNA amplification testing method in infertile males

Background

The purpose of this study was to evaluate the prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium and Ureaplasma urealyticum infections in infertile men that consulted our outpatient departments using a novel simultaneous amplification testing (SAT) that is RNA-detection based. The possible impact of C. trachomatis, N. gonorrhoeae, M. genitalium and U. urealyticum infections on semen parameters was also noted in the present study.

Methods

A total of 2607 males that were diagnosed with infertility were included in this study. C. trachomatis, N. gonorrhoeae, M. genitalium and U. urealyticum infections were detected in the urine samples using SAT method. Related data, including semen parameters and age as well as C. trachomatis, N. gonorrhoeae, M. genitalium and U. urealyticum infections were collected and analyzed.

Results

A total of 51 and 1418 urine samples were found positive for M. genitalium RNA and U. urealyticum RNA, respectively, while the prevalence of C. trachomatis and N. gonorrhoeae was relatively lower. Men with positive M. genitalium RNA and U. urealyticum RNA had higher sperm DNA fragmentation index (DFI) while the comparisons of other semen parameters yielded nonsignificant results between the RNA positive and negative group. A multivariate linear regression analysis revealed that U. urealyticum and M. genitalium infections posed significant factors of DFI (adjusted R² = 46.2%).

Conclusions

Our study suggested a relative high prevalence of U. urealyticum and M. genitalium infection based on this novel SAT detection method. U. urealyticum and M. genitalium infection could possibly impair male fertility potential through promoting sperm DNA damage.

Relevance of peroxynitrite formation and 3-nitrotyrosine on spermatozoa physiology

HIGHLIGHTS

Male fertility decline has been attributed, in part, to increased oxidative stress.Here we will focus on spermatozoa ROS, namely O2•-, NO and ONOO- and their contribution to protein tyrosine nitration, namely by 3-NT formation.An in depth review will be made on the methods used to detect protein oxidation.Detecting 3-NT in sperm proteins will have a crucial clinical impact, namely on the follow up of anti-oxidant therapies.

ABSTRACT

Infertility is a clinical condition that affects around 15% of reproductive-aged couples worldwide. Around half of these cases are due to male factors, the most owing to idiopathic causes. The increase of reactive oxygen species (ROS), which leads to oxidative stress (OS), has been discussed in the last years as a possible cause of male idiopathic infertility. Superoxide anion (O2 •-) and nitric oxide (NO) can react with each other contributing to the formation of peroxynitrite (ONOO-). This molecule can then act on spermatozoa proteins, leading to nitration of protein tyrosines - addition of a nitro (NO2) group - that is then manifested by the formation of 3-nitrotyrosine (3-NT). In turn, 3-NT may be responsible for the alteration or inactivation of the protein function.This review will focus on the description of spermatozoa ROS, namely O2 •-, NO and ONOO- and in their contribution to protein tyrosine nitration, namely by 3-NT formation. Previous results about the effect of ONOO- and 3-NT in spermatozoa will be presented, as well as, the methods that can be performed to detect the protein oxidation by these species. The impact of measuring, at the clinical level, 3-NT, considered a marker of OS, in spermatozoa will be discussed.

Toxicology Study of Single-walled Carbon Nanotubes and Reduced Graphene Oxide in Human Sperm

Carbon-based nanomaterials such as single-walled carbon nanotubes and reduced graphene oxide are currently being evaluated for biomedical applications including in vivo drug delivery and tumor imaging. Several reports have studied the toxicity of carbon nanomaterials, but their effects on human male reproduction have not been fully examined. Additionally, it is not clear whether the nanomaterial exposure has any effect on sperm sorting procedures used in clinical settings. Here, we show that the presence of functionalized single walled carbon nanotubes (SWCNT-COOH) and reduced graphene oxide at concentrations of 1-25 μg/mL do not affect sperm viability. However, SWCNT-COOH generate significant reactive superoxide species at a higher concentration (25 μg/mL), while reduced graphene oxide does not initiate reactive species in human sperm. Further, we demonstrate that exposure to these nanomaterials does not hinder the sperm sorting process, and microfluidic sorting systems can select the sperm that show low oxidative stress post-exposure.

The effect of adjuvant vitamin C after varicocele surgery on sperm quality and quantity in infertile men: a double blind placebo controlled clinical trial

Varicocele is one of the most common causes of male infertility and spontaneous pregnancy rate after varicocelectomy is only about 30%. The most important seminal antioxidant is vitamin C but recent studies about the effects of vitamin C on spermatogenesis are controversial; therefore, we decided to evaluate its role after varicocelectomy. In a double blind randomized controlled clinical trial, 115 men with infertility and clinical varicocele with abnormal semen analyses were recruited. After surgery, the intervention group received vitamin C (250 mg bid) and the control group received placebo for three months. Mean sperm count, motility, and morphology index of two semen analyses (before and after surgery) were compared between the two groups. Univariate general linear model and stepwise linear regression were used in analysis. The mean age (±SD) of participants was 27.6±5.3 years. Vitamin C group had statistically significant better normal motility (20.8 vs. 12.6, P=0.041) and morphology (23.2 vs. 10.5, P<0.001) than placebo group. Considering the values prior to surgery as covariate, vitamin C was not effective on sperm count (P=0.091); but it improved sperm motility (P=0.016) and morphology (P<0.001) even after excluding the confounding effect of age (P=0.044 and P=0.001, respectively). Vitamin C was also an independent factor in predicting motility and normal morphology after surgery. Ascorbic acid can play a role as adjuvant treatment after varicocelectomy in infertile men.

Antiperoxidative Activity of Tetracarpidium conophorum Leaf Extract in Reproductive Organs of Male Rats

Tetracarpidium conophorum (Mull. Arg.) Hutch. & Dalz is one of the many medicinal plants used in folklore as male fertility enhancers. This research was aimed at evaluating the anti-peroxidative activity of the leaves of this plant by determining their capacity to reduce malondialdehyde (MDA) level in reproductive organs and accessory glands of rats. Adult male rats were administered orally with the aqueous leaf extract from T. conophorum at 50, 500 and 1000 mg/kg body weight for 21 consecutive days while clomiphene citrate (1.04 mg/kg body weight), a fertility drug was used as standard. The results of the study indicated that there was increase in relative organ weight, body weight, mean total food and water consumed by the treated groups. Testicular MDA level was highly significantly different from that of the control (p < 0.0001) although a tentatively decreased MDA level was observed. However, MDA levels in the reproductive accessory glands, epididymis, seminal vesicle and prostate gland were insignificantly (p < 0.05) lower than those of controls. The highest percentage decrease of MDA level (66.35, 42.68, 62.50 and 63.36%) was observed at the highest concentration of the extract (1000 mg/kg) in the testis, epididymis, seminal vesicle and prostate gland respectively. These values were two-fold greater than the values obtained for the standard drug. Interestingly, the treatment of rats with the extract significantly increased the activities of superoxide dismutase, catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and the levels of GSH, vitamin C and total protein. Collectively, the results suggest that the extract from T. conophorum leaves had greater capacity to reduce lipid peroxidation in reproductive organs and accessory glands and thus, this plant may be useful in the treatment/management of reproductive cellular damage involving reactive oxygen species.

Environmental toxins

This review comprehensively summarizes the effects of more than 15 mostly used pesticides on male reproductive physiology, as recent experimental and epidemiological research have indicated their alarming impact on overall human health. Mechanisms have described that pesticide exposure damages spermatozoa, alter Sertoli or Leydig cell function, both in vitro and in vivo and thus affects semen quality. But, the literature suggests a need for more intricate research in those pesticides that are defined as mutagens or carcinogens and directly affect the hypothalamic–pituitary–gonadal axis. This literature review also proposes specific solutions to overcome these health effects.

Gold nanoparticles elevate plasma testosterone levels in male mice without affecting fertility

ω-Methoxy and ω-aminoethyl poly(ethylene glycol)-modified 14-nm gold nanoparticles can accumulate in mouse testes, pass through the blood-testis barrier, and enter germ cells. Furthermore, PEG-NH2 @AuNP accumulate more easier in the testes and increase plasma T levels. However, these two gold nanoparticle types have no effect on male fertility, fetal survival, or fetal development.

Cholesterol and male fertility: what about orphans and adopted?

The link between cholesterol homeostasis and male fertility has been clearly suggested in patients who suffer from hyperlipidemia and metabolic syndrome. This has been confirmed by the generation of several transgenic mouse models or in animals fed with high cholesterol diet. Next to the alteration of the endocrine signaling pathways through steroid receptors (androgen and estrogen receptors); "orphan" and "adopted" nuclear receptors, such as the Liver X Receptors (LXRs), the Proliferating Peroxisomal Activated Receptors (PPARs) or the Liver Receptor Homolog-1 (LRH-1), have been involved in this cross-talk. These transcription factors show distinct expression patterns in the male genital tract, explaining the large panel of phenotypes observed in transgenic male mice and highlighting the importance of lipid homesostasis and the complexity of the molecular pathways involved. Increasing our knowledge of the roles of these nuclear receptors in male germ cell differentiation could help in proposing new approaches to either treat infertile men or define new strategies for contraception.

Chlamydia, Mycoplasma and Ureaplasma infections in infertile couples and effects of these infections on fertility

OBJECTIVE

In our study, we aimed to determine the prevalence of Chlamydia trachomatis, Mycoplasma hominis and Ureaplasma urealyticum infections among infertile couples and effects of these infections on infertility.

MATERIALS AND METHODS

Prevalence of Chlamydia, Mycoplasma, Ureaplasma antibodies and Chlamydia IgM antibodies and its effect on these agents' sperm parameters, namely, morphology, density, and motility were investigated among a total of 212 patients including fertile and infertile couples. Chlamydia, Mycoplasma, Ureaplasma antigens were evaluated using ELISA in the cervical and urethral samples. Chlamydia IgM antibody was measured using micro-ELISA in blood samples.

RESULTS

No difference was detected among the fertile and infertile groups in the serological investigation of urethral and cervical samples with respect to the prevalence of Chlamydia, Mycoplasma, Ureaplasma antigens and Chlamydia IgM antibody and sperm parameters (p > 0.05).

DISCUSSION

There is no significant difference between fertile and infertile couples in terms of the prevalence of the above mentioned infections. Accordingly, during the infertility assessment, infertile couples should not be routinely screened for these infective agents without any clinically sound evidence.

Repeated administrations of carbon nanotubes in male mice cause reversible testis damage without affecting fertility

Soluble carbon nanotubes show promise as materials for in vivo delivery and imaging applications. Several reports have described the in vivo toxicity of carbon nanotubes, but their effects on male reproduction have not been examined. Here, we show that repeated intravenous injections of water-soluble multiwalled carbon nanotubes into male mice can cause reversible testis damage without affecting fertility. Nanotubes accumulated in the testes, generated oxidative stress and decreased the thickness of the seminiferous epithelium in the testis at day 15, but the damage was repaired at 60 and 90 days. The quantity, quality and integrity of the sperm and the levels of three major sex hormones were not significantly affected throughout the 90-day period. The fertility of treated male mice was unaffected; the pregnancy rate and delivery success of female mice that mated with the treated male mice did not differ from those that mated with untreated male mice.

Alterations of branching and differential expression of sialic acid on alpha-1-acid glycoprotein in human seminal plasma

BACKGROUND

The degree of branching and types of fucosylation of glycans on alpha(1)-acid glycoprotein (AGP) have been found to be associated with alpha(1)-acid glycoprotein concentrations in human seminal plasma. The glycosylation pattern of alpha(1)-acid glycoprotein in seminal plasma obtained from men living in infertile couples can undergo alterations in relation to sperm analysis and/or alpha(1)-acid glycoprotein concentrations.

METHODS

The glycosylation of alpha(1)-acid glycoprotein was studied upon the reactivity with specific lectins by crossed affinity immunoelectrophoresis (concanavalin A), and by glycoprotein lectin immunosorbent assay (Maackia amurensis and Sambucus nigra lectins), as well as high pH anion-exchange chromatography with pulsed amperometric detection.

RESULTS

Nonsignificant differences in alpha(1)-acid glycoprotein glycan branching and degree of its sialylation were observed among the AGP derived from seminal plasmas in relation to spermiogram and sperm morphology. However, significant concentration-dependent differences were found in extent of branching and type of sialylation.

CONCLUSIONS

The presence in seminal plasma of high concentrations of aberrantly glycosylated AGP molecules might be indicative for a chronic inflammatory condition in the reproductive tract, and can be used as additional tool to subdivide the seminal plasmas of men living in infertile couples.

Occupational risk for male infertility: a case-control study of 218 infertile and 227 fertile men

The aim of the study was to determine if certain occupations pose an increased risk for infertility (of no known cause) among a group of infertile men compared with a group of fertile men. A total of 640 consecutive men whose spouses were unable to conceive were recruited from an infertility clinic. Of these, 218 men (cases) were found to have no known cause for their infertility. A total of 227 men whose spouses were pregnant at the time of the study were recruited as controls. The Singapore Standard Occupational Classification was used to code the subjects' occupations. Semen parameters (density, total sperm counts, motility, viability, and normal morphology) in all of the cases were significantly poorer than those in the controls. The risk for infertility is associated with smoking adjusted odds ratio (OR) 2.85 and 95% confidence interval (CI) 1.91 to 4.24. Work, independently, is not a risk factor for infertility. Engineering technicians (adjusted OR, 2.75; 95% CI, 1.36 to 5.54), finance analysts (adjusted OR, 4.66; 95% CI, 1.90 to 11.40), corporate and computing managers (adjusted OR, 2.49; 95% CI, 1.04 to 5.98), and teachers (adjusted OR, 7.72; 95% CI, 1.86 to 32.10) were at a greater risk of infertility compared with "services and clerical workers." Using services and clerical workers as a reference group, certain occupations are at a higher risk for infertility. Higher work demands and possible electromagnetic field exposure could be contributory factors for infertility.

The role of reactive oxygen species in testicular dysfunction associated with varicocele

OBJECTIVE

To determine the level of malondialdehyde (MDA), an indirect indicator of lipid peroxidation-induced injury by reactive oxygen species, in testicular biopsy specimens from infertile patients with and without varicocele.

PATIENTS AND METHODS

Levels of MDA were measured in the testicular biopsy specimens from 25 infertile men (15 with varicocele, mean age 30.0 years, SD 5.7, range 23-45, and 10 without, mean age 28.7 years, SD 4.2, range 21-34). All patients were evaluated by a detailed history, physical examination, semen analysis (at least twice), serum follicle-stimulating hormone and free testosterone levels, testicular biopsy and contact imprint. Scrotal colour Doppler ultrasonography was used to confirm suspected varicocele. The level of MDA in testicular biopsy specimens was measured using the thiobarbituric acid test and the results expressed per unit tissue weight.

RESULTS

As a causal factor for infertility, varicocele was identified in 15 men (60%), testicular failure in four (16%), idiopathic infertility in four (16%) and obstruction in two (8%). Of the 15 patients with varicocele, eight had bilateral varicocele and it was subclinical in three; the varicocele was grade I in four, grade II in six and grade III in two. The mean (SD) MDA level in the men with a subclinical varicocele was 15.7 (3.1) pmol/mg tissue, while in those with grade I-III varicocele it was 32.9 (12.25), 37.1 (12.25) and 86.9 (2.89) pmol/mg tissue, respectively. The levels in patients with grade III varicocele were significantly greater than in the other groups (P < 0.05). The mean MDA level in patients with or without varicocele was 38.3 (22.92) and 33.5 (18.93) pmol/mg tissue, respectively (P > 0.05).

CONCLUSION

These results suggest that increasing levels of MDA are associated with higher grades of varicocele and support a possible rationale for controlled trials in infertile men with varicocele.

Factors associated with male infertility: a case-control study of 218 infertile and 240 fertile men

OBJECTIVE

To determine the likely risk factors, such as smoking and drinking habits, and occupational groups, for infertility in a group of infertile men with no known cause, compared with a group of fertile men; and to examine the effects of the semen parameters, such as volume, density, motility, viability and normal morphology, on fertility.

DESIGN

A case-control study.

SETTING

The department of obstetric and gynaecology of a tertiary general hospital.

PARTICIPANTS

Six hundred and forty consecutive male partners of couples trying to conceive were recruited from an infertility clinic. Of these, the cases comprised 218 men who had no known cause for their infertility. Two hundred and forty men whose wives were pregnant at the time of the study were recruited as controls.

RESULTS

The semen parameters (e.g. density, total sperm counts, motility, viability and normal morphology) of all cases were significantly poorer than that of the controls. The risk of infertility is associated with smoking (crude OR 2 x 82, 95% CI 1 x 93-4 x 13; adjusted OR 2 x 96; 95% CI 1 x 98-4 x 42). Technicians (adjusted OR 2 x 81; 95% CI 1 x 51-4 x 24) and professional, senior officials and managers were also at a greater risk of infertility (adjusted OR 2 x 36; 95% CI 1 x 26-4 x 40), compared with service and clerical workers. The significant factors predicting infertility were smoking, density of sperm, and viability of sperm. Smoking increased the odds of being infertile. Higher sperm counts and larger percentage of viable sperm decrease the odds of infertility. Based on the multiple logistic regression model, the odds ratio for infertility = (94 x 70) x (2 x 88(smoking)) X (0 x 29(logdensity)) X (0 x 95(viability)).

CONCLUSION

Smoking, density of sperm and the viability of sperm are significant predictors for infertility among men.

Chlamydial infections and male infertility

Chlamydial infections may be difficult to diagnose due to the silent symptoms and difficulty in culturing. An infectious process may impair fertility by adversely affecting sperm functions, resulting in testicular damage or causing obstruction of the genital tract. In our study, we tried to find Chlamydial antigen by using EIA (Enzyme Immune Assay) and to compare the Ag(+) and Ag(-) groups according to semen parameters. Except for semen volume, we found significant differences in density, morphology, motility and viability (intervolume p > 0.05, interdensity p < 0.01, intermorphology p < 0.001, intermotility p < 0.001 and interviability p < 0.001).