Human spermatozoa: revelations on the road to conception

Efficacy of Chlorogenic Acid in Treating Tripterygium Glycoside-Induced Asthenozoospermia in Rats and Its Possible Mechanisms

Tripterygium glycosides (TGs) are the most common form of traditional Chinese medicine, known as Tripterygium wilfordii Hook F (TWHF) [...].

Impact of oxidative stress SNPs on sperm DNA damage and male infertility in a south-east Iranian population

AIM

We examined four single nucleotide polymorphisms in four antioxidant genes (PON1 , CAT , GPx1 and SOD2 ) in 100 infertility cases and 100 controls from an Iranian population-based case-control study to confirm the assumption that polymorphisms in oxidative stress genes increase the risk of sperm DNA damage and idiopathic male infertility.

METHODS

Restriction fragment length polymorphism and tetra-primer amplification refractory mutation system PCR were used to identify genotypes. Sperm DNA damage was assessed using the Sperm Chromatin Dispersion test (Halo Sperm), and the total antioxidant capacity of seminal fluid was determined using the FRAP assay.

KEY RESULTS

Our findings demonstrated that alleles Arg-PON1 (rs662) and Ala-MnSOD (rs4880) variant genotypes were considerably linked with a higher risk of male infertility.

CONCLUSIONS

Linear regression analysis revealed that those with the PON1 Gln192Arg or SOD2 Val16Ala variants have significantly higher levels of sperm DNA fragmentation and lower levels of the total antioxidant capacity in seminal fluid.

IMPLICATIONS

These findings suggest that genetic differences in antioxidant genes may be linked to oxidative stress, sperm DNA damage, and idiopathic male infertility.

Correlation of Sperm Mitochondrial DNA 7345 bp and 7599 bp Deletions with Asthenozoospermia in Jordanian Population

BACKGROUND

Alterations in sperm mitochondrial DNA (mtDNA) affect the functions of some OXPHOS proteins which will affect sperm motility and may be associated with asthenozoospermia. The purpose of this study was to investigate the correlation between 7599-bp and 7345-bp sperm mtDNA deletions and asthenozoospermia in Jordan.

METHODS

Semen specimens from 200 men including 121 infertile and 79 healthy individuals were collected at the Royal Jordanian Medical Services In-vitro fertilization (IVF) units. The mtDNA was extracted followed by mtDNA amplification. Polymerase chain reaction (PCR) was conducted for the target sequences, then DNA sequencing was performed for the PCR products. Chi-square, Fisher's and Spearman's tests were used to calculate the correlation.

RESULTS

The results showed a significant correlation between the presence of 7599-bp mtDNA deletion and infertility where the frequency of the 7599-bp deletion was 63.6% in the infertile group compared to the fertile 34.2% (p<0.001, (OR=3.37, 95% CI=1.860 to 6.108)). Additionally, the sperm motility showed a significant association with the frequency of the 7599-bp deletion (p=0.001, r=-0.887). The 7345-bp mtDNA deletion showed no assoctiation with the infertility (p=0.65, (OR=0.837, 95% CI= 0.464-1.51)) or asthenozoospermia (p=0.98, r=0.008).

CONCLUSION

We demonstrated a significant correlation between asthenozoospermia and the 7599-bp mtDNA deletion but not the 7345-bp mtDNA deletion in the infertile men in Jordan. Screening for deletions in sperm mtDNA can be used as a pre-diagnostic molecular marker for male infertility.

Whole-body exposures to radiofrequency-electromagnetic energy can cause DNA damage in mouse spermatozoa via an oxidative mechanism

Artificially generated radiofrequency-electromagnetic energy (RF-EME) is now ubiquitous in our environment owing to the utilization of mobile phone and Wi-Fi based communication devices. While several studies have revealed that RF-EME is capable of eliciting biological stress, particularly in the context of the male reproductive system, the mechanistic basis of this biophysical interaction remains largely unresolved. To extend these studies, here we exposed unrestrained male mice to RF-EME generated via a dedicated waveguide (905 MHz, 2.2 W/kg) for 12 h per day for a period of 1, 3 or 5 weeks. The testes of exposed mice exhibited no evidence of gross histological change or elevated stress, irrespective of the RF-EME exposure regimen. By contrast, 5 weeks of RF-EME exposure adversely impacted the vitality and motility profiles of mature epididymal spermatozoa. These spermatozoa also experienced increased mitochondrial generation of reactive oxygen species after 1 week of exposure, with elevated DNA oxidation and fragmentation across all exposure periods. Notwithstanding these lesions, RF-EME exposure did not impair the fertilization competence of spermatozoa nor their ability to support early embryonic development. This study supports the utility of male germ cells as sensitive tools with which to assess the biological impacts of whole-body RF-EME exposure.

Effects of media and promoters on different lipid peroxidation assays in stallion sperm

Effects of different media and promoters on lipid peroxidation (LPO) in viable stallion sperm have not been reported. Aims of this study were to determine effects of three media (INRA-96™, Equipro CoolGuard™, and Biggers, Whitten and Whittingham [BWW]), and promoters (iron sulfate-Fe; ultraviolet light-UV; or control-no exposure to promoters) on viable sperm LPO using four different flow cytometric assays (i.e., BODIPY, Liperfluo, 4-hydroxylnonenal [4HNE], malonaldehyde [MDA]). Significant media x promoter interactions were detected using the Liperfluo, 4HNE, and MDA assays (P <  0.05); therefore, data were sorted by media and by promoters. With inclusion of milk-based media, there were similar concentrations of LPO in control samples with use of all LPO assays. The effect of iron, as a promoter of LPO production, was media dependent, and milk-based media protected sperm from iron-induced LPO production when there were assessments with all assays. In contrast, iron promoted LPO in sperm diluted in BWW when there was use of in all assays, except BODIPY, probably because of the different target molecule with use of this assay. Ultraviolet light was the most potent LPO promoter with all media and assays evaluated. Data indicate milk-based extenders are generally more LPO-protective than BWW early in the LPO production pathway (based on BODIPY and Liperfluo assays), but are less protective during the later stages of LPO production (based on 4HNE and MDA assays). The use of different media and promoters of LPO allowed for determination of early and late stages of LPO in viable stallion sperm.

Transgenerational inheritance: how impacts to the epigenetic and genetic information of parents affect offspring health

BACKGROUND

A defining feature of sexual reproduction is the transmission of genomic information from both parents to the offspring. There is now compelling evidence that the inheritance of such genetic information is accompanied by additional epigenetic marks, or stable heritable information that is not accounted for by variations in DNA sequence. The reversible nature of epigenetic marks coupled with multiple rounds of epigenetic reprogramming that erase the majority of existing patterns have made the investigation of this phenomenon challenging. However, continual advances in molecular methods are allowing closer examination of the dynamic alterations to histone composition and DNA methylation patterns that accompany development and, in particular, how these modifications can occur in an individual’s germline and be transmitted to the following generation. While the underlying mechanisms that permit this form of transgenerational inheritance remain unclear, it is increasingly apparent that a combination of genetic and epigenetic modifications plays major roles in determining the phenotypes of individuals and their offspring.

OBJECTIVE AND RATIONALE

Information pertaining to transgenerational inheritance was systematically reviewed focusing primarily on mammalian cells to the exclusion of inheritance in plants, due to inherent differences in the means by which information is transmitted between generations. The effects of environmental factors and biological processes on both epigenetic and genetic information were reviewed to determine their contribution to modulating inheritable phenotypes.

SEARCH METHODS

Articles indexed in PubMed were searched using keywords related to transgenerational inheritance, epigenetic modifications, paternal and maternal inheritable traits and environmental and biological factors influencing transgenerational modifications. We sought to clarify the role of epigenetic reprogramming events during the life cycle of mammals and provide a comprehensive review of how the genomic and epigenomic make-up of progenitors may determine the phenotype of its descendants.

OUTCOMES

We found strong evidence supporting the role of DNA methylation patterns, histone modifications and even non-protein-coding RNA in altering the epigenetic composition of individuals and producing stable epigenetic effects that were transmitted from parents to offspring, in both humans and rodent species. Multiple genomic domains and several histone modification sites were found to resist demethylation and endure genome-wide reprogramming events. Epigenetic modifications integrated into the genome of individuals were shown to modulate gene expression and activity at enhancer and promoter domains, while genetic mutations were shown to alter sequence availability for methylation and histone binding. Fundamentally, alterations to the nuclear composition of the germline in response to environmental factors, ageing, diet and toxicant exposure have the potential to become hereditably transmitted.

WIDER IMPLICATIONS

The environment influences the health and well-being of progeny by working through the germline to introduce spontaneous genetic mutations as well as a variety of epigenetic changes, including alterations in DNA methylation status and the post-translational modification of histones. In evolutionary terms, these changes create the phenotypic diversity that fuels the fires of natural selection. However, rather than being adaptive, such variation may also generate a plethora of pathological disease states ranging from dominant genetic disorders to neurological conditions, including spontaneous schizophrenia and autism.

Antioxidant and anti-apoptotic effects of royal jelly against nicotine-induced testicular injury in mice

This study describes the effects of royal jelly (RJ) on testicular injury induced by nicotine (NIC) in mice. Thirty-six male BALB/c mice were randomly divided into six groups (n = 6). Group 1 received normal saline, group 2 received 100 mg/kgBW/day RJ, groups 3 and 4 received NIC at doses of 0.50 and 1.00 mg/kgBW/day, respectively, and groups 5 and 6 received NIC at doses of 0.50 and 1.00 mg/kg BW/day, respectively, plus RJ. Following 35 days, the serum level of testosterone, histopathological changes, germ cell apoptosis, proliferating cell nuclear antigen (PCNA), malondialdehyde (MDA) content, and antioxidant indexes including total antioxidant capacity (TAC) and catalase (CAT) activity were determined. In addition, the mitochondria-dependent apoptosis was investigated by assessing the Bcl-2, p53, and Caspase-3 mRNA levels expression by reverse transcription-PCR (RT-PCR). Compared to NIC receiving groups, the concomitant administration of RJ could protect the testosterone reduction and histological damages. After RJ treatment, the level of tissue MDA content decreased, while tissue TAC and CAT levels were remarkably increased compared to NIC-exposed groups. Remarkable higher TUNEL-positive germ cells and low PCNA index were observed in NIC receiving groups. Besides, the expression level of Bcl-2 was significantly higher and the p53 and Caspase-3 levels were significantly lower in the RJ co-administration groups than NIC-only receiving groups. Our results confirmed that RJ effectively protects the testis against NIC evoked damages by antioxidant and anti-apoptotic effects involving the up regulation of the antioxidant status, mitochondria-dependent apoptosis pathway prevention, and the proliferating activity improvement.

Molecular Mechanisms and Signaling Pathways Involved in Sertoli Cell Proliferation

Sertoli cells are somatic cells present in seminiferous tubules which have essential roles in regulating spermatogenesis. Considering that each Sertoli cell is able to support a limited number of germ cells, the final number of Sertoli cells reached during the proliferative period determines sperm production capacity. Only immature Sertoli cells, which have not established the blood-testis barrier, proliferate. A number of hormonal cues regulate Sertoli cell proliferation. Among them, FSH, the insulin family of growth factors, activin, and cytokines action must be highlighted. It has been demonstrated that cAMP/PKA, ERK1/2, PI3K/Akt, and mTORC1/p70SK6 pathways are the main signal transduction pathways involved in Sertoli cell proliferation. Additionally, c-Myc and hypoxia inducible factor are transcription factors which participate in the induction by FSH of various genes of relevance in cell cycle progression. Cessation of proliferation is a pre-requisite to Sertoli cell maturation accompanied by the establishment of the blood-testis barrier. With respect to this barrier, the participation of androgens, estrogens, thyroid hormones, retinoic acid and opioids has been reported. Additionally, two central enzymes that are involved in sensing cell energy status have been associated with the suppression of Sertoli cell proliferation, namely AMPK and Sirtuin 1 (SIRT1). Among the molecular mechanisms involved in the cessation of proliferation and in the maturation of Sertoli cells, it is worth mentioning the up-regulation of the cell cycle inhibitors p21Cip1, p27Kip, and p19INK4, and of the gap junction protein connexin 43. A decrease in Sertoli cell proliferation due to administration of certain therapeutic drugs and exposure to xenobiotic agents before puberty has been experimentally demonstrated. This review focuses on the hormones, locally produced factors, signal transduction pathways, and molecular mechanisms controlling Sertoli cell proliferation and maturation. The comprehension of how the final number of Sertoli cells in adulthood is established constitutes a pre-requisite to understand the underlying causes responsible for the progressive decrease in sperm production that has been observed during the last 50 years in humans.

Oxidative stress and male infertility

DNA damage, largely owing to oxidative stress, is a leading cause of defective sperm function. High levels of oxidative stress result in damage to sperm DNA, RNA transcripts, and telomeres and, therefore might provide a common underlying aetiology of male infertility and recurrent pregnancy loss, in addition to congenital malformations, complex neuropsychiatric disorders, and childhood cancers in children fathered by men with defective sperm cells. Spermatozoa are highly vulnerable to oxidative stress owing to limited levels of antioxidant defence and a single, limited DNA-damage detection and repair mechanism. Oxidative stress is predominantly caused by a host of lifestyle-related factors, the majority of which are modifiable. Antioxidant regimens and lifestyle modifications could both be plausible therapeutic approaches that enable the burden of oxidative-stress-induced male factor infertility to be overcome. Lifestyle interventions including yoga and meditation can substantially improve the integrity of sperm DNA by reducing levels of oxidative DNA damage, regulating oxidative stress and by increasing the expression of genes responsible for DNA repair, cell-cycle control and anti-inflammatory effects. Oxidative stress is caused by various modifiable factors, and the use of simple interventions can decrease levels of oxidative stress, and therefore reduce the incidence of both infertility and complex diseases in the resultant offspring.

[Social freezing - the male perspective]

BACKGROUND

In Germany there is an emerging trend for postponing parenthood due to non-medical, sociocultural reasons. This clearly impacts on the reproductive success due to an age-dependent decrease in fertility. Thus, strategies and techniques are currently discussed which could preserve the female fertility status, among which social freezing (cryopreservation of oocytes) for later fertilization is the most realistic one; however, while there is an intensive discussion on the procedure and timing of oocyte cryopreservation, virtually no attention has been paid to the male side and the aging effects on the male germ cells.

AIM

To evaluate the risk paternal age poses for the integrity of germ cells.

METHODS

For this review a literature search using PubMed, data from the Federal Statistical Office of Germany, the German in vitro fertilization (IVF) register as well as own data were used.

RESULTS

Sperm cell integrity is clearly affected by age both at the genetic as well as at the epigenetic levels. The estimated mutation rate for spermatozoa doubles every 16.5 years. Monogenic and multifactorial diseases are strongly associated with paternal age. Men aged >40 years have an increased risk of passing age-related mutations to their children.

CONCLUSIONS

Cryopreservation of spermatozoa is an option for men who postpone planning a family. Genetic counseling is recommended for couples undertaking social freezing and a male age of >40 years.

Are sperm capacitation and apoptosis the opposite ends of a continuum driven by oxidative stress?

This chapter explores the possibility that capacitation and apoptosis are linked processes joined by their common dependence on the continued generation of reactive oxygen species (ROS). According to this model capacitation is initiated in spematozoa following their release into the female reproductive tract as a consequence of intracellular ROS generation, which stimulates intracellular cAMP generation, inhibits tyrosine phosphatase activity and enhances the formation of oxysterols prior to their removal from the sperm surface by albumin. The continued generation of ROS by capacitating populations of spermatozoa eventually overwhelms the limited capacity of these cells to protect themselves from oxidative stress. As a result the over-capacitation of spermatozoa leads to a state of senescence and the activation of a truncated intrinsic apoptotic cascade characterized by enhanced mitochondrial ROS generation, lipid peroxidation, motility loss, caspase activation and phosphatidylserine externalization. The latter may be particularly important in instructing phagocytic leukocytes that the removal of senescent, moribund spermatozoa should be a silent process unaccompanied by the generation of proinflammatory cytokines. These observations reveal the central role played by redox chemistry in defining the life and death of spermatozoa. A knowledge of these mechanisms may help us to engineer novel solutions to both support and preserve the functionality of these highly specialized cells.

Sperm aneuploidy in infertile male patients: a systematic review of the literature

Males with abnormal karyotypes and subgroups of fertile and infertile males with normal karyotypes may be at risk of producing unbalanced or aneuploid spermatozoa. Biological, clinical, environmental and other factors may also cause additional sperm aneuploidy. However, increased risk of sperm aneuploidy is directly related to chromosomally abnormal embryo production and hence to poor reproductive potential. This systemic literature review focuses on the identification of these males because this is an essential step in the context of assisted reproduction. This research may allow for a more personalised and, hence, more accurate estimation of the risk involved in each case, which in turn will aid genetic counselling for affected couples and help with informed decision-making.

Endocannabinoids as biomarkers of human reproduction

BACKGROUND

Infertility is a condition of the reproductive system that affects ∼10-15% of couples attempting to conceive a baby. More than half of all cases of infertility are a result of female conditions, while the remaining cases can be attributed to male factors, or to a combination of both. The search for suitable biomarkers of pregnancy outcome is a challenging issue in human reproduction, aimed at identifying molecules with predictive significance of the reproductive potential of male and female gametes. Among the various candidates, endocannabinoids (eCBs), and in particular anandamide (AEA), represent potential biomarkers of human fertility disturbances. Any perturbation of the balance between synthesis and degradation of eCBs will result in local changes of their tone in human female and male reproductive tracts, which in turn regulates various pathophysiological processes, oocyte and sperm maturation included.

METHODS

PubMed and Web of Science databases were searched for papers using relevant keywords like 'biomarker', 'endocannabinoid', 'infertility', 'pregnancy' and 'reproduction'.

RESULTS

In this review, we discuss different studies on the measurements of AEA and related eCBs in human reproductive cells, tissues and fluids, where the local contribution of these bioactive lipids could be critical in ensuring normal sperm fertilizing ability and pregnancy.

CONCLUSION

Based on the available data, we suggest that the AEA tone has the potential to be exploited as a novel diagnostic biomarker of infertility, to be used in association with assays of conventional hormones (e.g. progesterone, β-chorionic gonadotrophin) and semen analysis. However further quantitative research of its predictive capacity is required.