Status of sperm mitochondrial functions and DNA methylation in infertile men with clinical varicocele before and after treatment

Varicocele has been associated with reduced male fertility potential. Treatment modalities for varicocele improve semen parameters, yet more than 50% of cases remain infertile. Varicocele-induced heat and hypoxia stress may affect sperm mitochondrial functions, possibly leading to aberrant epigenetic modifications. This study includes 30 fertile men and 40 infertile men with clinical varicocele. The effect of varicocele treatment (antioxidant supplementation and or varicocelectomy) was evaluated after 3 months of treatment. Mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (iROS) were measured by flow cytometry using JC-1 and DCFDA, respectively. mtDNA copy number and deletions were determined by PCR. DNA methylation was analysed by pyrosequencing. Present investigations suggest that infertile men with varicocele have abnormal semen parameters; significantly low MMP, high iROS, and high mtDNA copy number. Semen parameters were improved in a subset of men of both the treatment modalities; however, it was noted that varicocelectomy helped better in improving sperm parameters compared to antioxidant treatment. Both treatment modalities helped in reducing iROS and mtDNA copy number significantly; however, they were noneffective in improving MMP. Altered DNA methylation at mitochondria D loop and mitochondrial structure and function genes UQCRC2, MIC60, TOM22, and LETM1 (promoter region) were observed in varicocele group. The DNA methylation levels were restored after varicocele treatment; however, the restoration was not consistent at all CpG sites. Both the treatment modalities helped in restoring the altered DNA methylation levels of mitochondrial genes but the restoration is nonhomogeneous across the studied CpG sites.

Molecular characterization of DNAH6 and ATPase6 (Mitochondrial DNA) genes in asthenozoospermia patients in the northern region of India

BACKGROUND

Male infertility due to spermatogenesis defects affects millions of men worldwide. However, the genetic etiology of the vast majority remains unclear. The present study was undertaken to assess the association of DNAH6 and ATPase6 genes in asthenozoospermia patients in the northern region of India.

METHODS

A total of 60 semen samples were collected for the study, of which 30 were from the case group and 30 were from the control group. The semen samples for the case group (asthenozoospermia) and control groups were collected from IVF and Reproductive Biology Centre, Maulana Azad Medical College, New Delhi. Sperm count and motility were classified as per World Health Organization (WHO 2021) protocol. A total genomic DNA was extracted as per the stranded TRIZOL method with little modification.

RESULTS

In-vitro molecular characterizations of DNAH6 and ATPase6 genes in both groups were checked by Polymerase Chain Reaction (PCR). The 675 bp and 375 bp amplicons were amplified using PCR for ATPase6 and DNAH6 genes. Our study results showed a significant (P ≤ 0.05) null deletion of DNAH6 and ATPase6 genes in asthenozoospermia patients as compared to the control. We found the significant null deletion of DNAH6 in case 45.0%, and the control group was 11.7%. However, in the case of APTase6, it was 26.7% and 10.0%, respectively.

CONCLUSIONS

Our study concluded that the presence of DHAH6 and ATPase6 genes had a significant impact on male infertility.

Varicocele associated male infertility: cellular and molecular perspectives of pathophysiology

BACKGROUND

Varicocele is a common risk factor associated with reduced male fertility potential. The current understanding of varicocele pathophysiology does not completely explain the clinical manifestation of infertility. The present treatment options such as antioxidant supplementation and varicocelectomy only helps ∼35% of men to achieve spontaneous pregnancy.

OBJECTIVE

This review aims to summarize the available knowledge on cellular and molecular alterations implicated to varicocele associated male infertility and also highlights the new knowledge generated by 'Omics' technologies.

MATERIALS AND METHODS

PubMed, MEDLINE, Cochrane and Google Scholar databases are searched using different combinations of keywords (varicocele, infertile/fertile men with varicocele, cellular changes, molecular mechanisms, proteome, epigenome, transcriptome and metabolome). A total of 229 relevant human and animal studies published till 2021 were included in this review.

RESULTS

Current understanding advocates oxidative stress (OS) as a major contributory factor to the varicocele associated male infertility. Excessive OS causes alteration in testicular microenvironment and sperm DNA fragmentation which further contributes to infertility. Molecular and omics studies have identified several promising biomarkers such as AAMP, SPINT1, MKI67 (genetic markers), sperm quality and function related protein markers, global sperm DNA methylation level (epigenetic marker), Hspa2, Protamine, Gadd7, Dynlt1 and Beclin1 (mRNA markers), PRDX2, HSPA, APOA2, YKL40 (seminal protein markers), total choline and PHGDH (metabolic markers).

DISCUSSION

Mature spermatozoa harbours a plethora of molecular information in form of proteome, epigenome and transcriptome; which could provide very important clues regarding pathophysiology of varicocele associated infertility. Recent molecular and omics studies in infertile men with varicocele have identified several promising biomarkers. Upon further validation with larger and well-defined studies, some of these biomarkers could aid in varicocele management.

CONCLUSION

The present evidences suggest inclusion of OS and sperm DNA fragmentation tests could be useful to the diagnostic workup for men with varicocele. Furthermore, including precise molecular markers may assist in diagnostics and prognostics of varicocele associated male infertility. This article is protected by copyright. All rights reserved.

The Role of NLRP3 Inflammasome Activation and Oxidative Stress in Varicocele-Mediated Male Hypofertility

Varicocele (VC) is the most common abnormality identified in men evaluated for hypofertility. Increased levels of reactive oxygen species (ROS) and reduced antioxidants concentrations are key contributors in varicocele-mediated hypofertility. Moreover, inflammation and alterations in testicular immunity negatively impact male fertility. In particular, NLRP3 inflammasome activation was hypothesized to lead to seminal inflammation, in which the levels of specific cytokines, such as IL-1β and IL-18, are overexpressed. In this review, we described the role played by oxidative stress (OS), inflammation, and NLRP3 inflammasome activation in VC disease. The consequences of ROS overproduction in testis, including inflammation, lipid peroxidation, mitochondrial dysfunction, chromatin damage, and sperm DNA fragmentation, leading to abnormal testicular function and failed spermatogenesis, were highlighted. Finally, we described some therapeutic antioxidant strategies, with recognized beneficial effects in counteracting OS and inflammation in testes, as possible therapeutic drugs against varicocele-mediated hypofertility.

A novel protein biochip screening serum anti-sperm antibody expression and natural pregnancy rate in a follow-up study in Chinese infertility

Production of anti-sperm antibody (ASA) often suffers from autoimmune reaction against sperms in human infertility. The antibodies are measured in both blood and seminal plasma of males. Here, we reported a simple protein biochip methodology that takes advantage of a functionalized self-assembled monolayer modified by N-hydroxysuccinimide (NHS) and enables identification of anti-sperm antibody in Chinese male infertility. To validate this biochip platform, we immobilized purified sperm protein on the biochip surface and tested a variety of parameters in quality controls for the protein assay, respectively. Then, we analyzed serum samples from 368 patients with infertility and 116 healthy donors by means of this biochip simultaneously. We found that positive rate of serum ASA was 20.92% (77/368) in the cases and 1.72% (2/116) in the controls, respectively. Furthermore, we further corroborated the biochip assay in comparison with ELISA method. We found that both methods were compatible for the detection of serum ASA in the patients. In addition, a follow-up study for natural conception in ASA-positive and ASA-negative patients was conducted. The result showed a significant correlation between serum ASA expression and natural pregnancy rate 6.5% in ASA-positive patients while 18.9% in ASA-negative patients, indicating the potential roles of ASA in naturally reproductive processes.

Assessment of correlation between asthenozoospermia and mitochondrial DNA mutations in Egyptian infertile men

BACKGROUND

Asthenozoospermia is a chief reason for male seminal pathologies with an impression of around 19% of infertile patients. Spermatozoa mitochondrial DNA variations seem to link with low sperm motility. The objective of the study was to assess the relation between mitochondrial mutations and male sterility, especially in asthenozoospermia. The patient semen samples were investigated by studying the sperm physical characters; motility, viability, and morphological parameters were then classified into normozoospermia and asthenozoospermia. In addition, the level of malondialdehyde (MDA) as a bio-indicator of lipid peroxidation, seminal fructose, and total antioxidant capacity (TAC) were estimated. For molecular analysis, DNA from the semen samples was extracted using a DNA extraction kit. ND1, ND2, and ATPase6 genes were amplified by using a specific primer. After the purification procedure, each PCR product was sequenced to identify the single nucleotide polymorphisms (SNPs) in selected genes.

RESULTS

A significant negative correlation between seminal plasma malondialdehyde levels and sperm motility was detected. Meanwhile, TAC analysis revealed significantly lower activity (p ≤ 0.05) in the sample of asthenozoospermic than in normozoospermic men. As regards the seminal plasma fructose, there was no significant difference in the fructose level of normozoospermia and asthenozoospermia cases. At the molecular level, 31 diverse nucleotide substitutions were recognized in mitochondrial DNA. Only ten (10) mutations led to amino acid transformation: four have deleterious effects, four are benign, and the other two have conflicting effectiveness.

CONCLUSIONS

This study is the first in Egypt that is concerned with studying the relationship between the mitochondrial DNA mutations in human spermatozoa of asthenozoospermic patients and fertility. The results displayed scientific indications evidenced that there is an association between mitochondrial mutations and male infertility.

Associations of mitochondrial DNA copy number and deletion rate with early pregnancy loss

Early pregnancy loss (EPL) is a common event worldwide. Previous studies show that mitochondrial DNA (mtDNA) copy number (CN) is associated with semen parameters and preimplantation embryo viability, indicating the predictive potential of mtDNA CN for ongoing pregnancy outcomes. However, no relevant study has assessed the relationship between mtDNA CN and EPL. Thus, we aimed to determine whether mtDNA CN and mtDNA 4977-bp deletion rate (DR) in chorionic villous tissue are associated with EPL. Chorionic villous tissue total DNA was extracted from 75 EPL cases and 75 healthy controls. Chromosomal analysis was conducted using copy number variation (CNV) sequencing. The mtDNA CN and DR were measured in samples without pathogenic CNVs. The association between mtDNA CN or DR and EPL risk were estimated using logistic regression. The EPL group had a significantly different mtDNA CN (P < 0.001) and DR (P = 0.005) compared to the control group. Both biomarkers were independent risk factors for EPL (CN odds ratio 1.71, 95% confidence interval 1.17 to 2.49, P = 0.005; DR odds ratio 1.07, 95% confidence interval 1.02 to 1.12, P = 0.006). These results suggest that higher mtDNA CN and DR levels are strongly associated with EPL and represent independent risk factors for EPL. Further studies validating these findings and exploring the underlying biological mechanisms are warranted.

Molecular Changes Induced by Oxidative Stress that Impair Human Sperm Motility

A state of oxidative stress (OS) and the presence of reactive oxygen species (ROS) in the male reproductive tract are strongly correlated with infertility. While physiological levels of ROS are necessary for normal sperm functioning, elevated ROS production can overwhelm the cell's limited antioxidant defenses leading to dysfunction and loss of fertilizing potential. Among the deleterious pleiotropic impacts arising from OS, sperm motility appears to be particularly vulnerable. Here, we present a mechanistic account for how OS contributes to altered sperm motility profiles. In our model, it is suggested that the abundant polyunsaturated fatty acids (PUFAs) residing in the sperm membrane serve to sensitize the male germ cell to ROS attack by virtue of their ability to act as substrates for lipid peroxidation (LPO) cascades. Upon initiation, LPO leads to dramatic remodeling of the composition and biophysical properties of sperm membranes and, in the case of the mitochondria, this manifests in a dissipation of membrane potential, electron leakage, increased ROS production and reduced capacity for energy production. This situation is exacerbated by the production of cytotoxic LPO byproducts such as 4-hydroxynonenal, which dysregulate molecules associated with sperm bioenergetic pathways as well as the structural and signaling components of the motility apparatus. The impact of ROS also extends to lesions in the paternal genome, as is commonly seen in the defective spermatozoa of asthenozoospermic males. Concluding, the presence of OS in the male reproductive tract is strongly and positively correlated with reduced sperm motility and fertilizing potential, thus providing a rational target for the development of new therapeutic interventions.

Genetics and epigenetics of varicocele pathophysiology: an overview

Varicocele is found in approximately 20% of adults and adolescents and in 19-41% of men seeking treatment for infertility. It is associated with a decrease in sperm count as well as sperm motility and morphology. The currently accepted description of the pathophysiology of varicocele does not explain all its clinical manifestations; therefore, other factors such as genetic and epigenetic changes, associated with the environment, might be involved in causing infertility and decrease in sperm quality. It has been reported that the varicocele-induced deterioration of testicular function is progressive and interferes with fertility; hence, early and efficient assessment of the genetic manifestations in patients would be important for developing future medical interventions. Chromosomal disorders, mutations, polymorphisms, changes in gene expression, and epigenetic changes have all been reported to be associated with varicocele. Several studies are underway to unravel the genetic basis of this disease, as it is important to understand the origin and the aggravating factors to ensure appropriate guidance and intervention. Here, we review the available literature regarding the genetic and epigenetic changes associated with varicocele, and how these alterations are related to the different clinical manifestations of the disease.

Large Scale 7436-bp Deletions in Human Sperm Mitochondrial DNA with Spermatozoa Dysfunction and Male Infertility

INTRODUCTION

Mitochondria and mitochondrial DNA are essential to sperm motility and fertility. It controls growth, development and differentiation through oxidation energy supply. Mitochondrial (mtDNA) deletions or mutation are frequently attributed to defects of sperm motility and finally these deletions lead to sperm dysfunction and causes infertility in male.

AIM

To investigate the correlation between large scale 7436-bp deletions in sperm mtDNA and non-motility of sperm in asthenozoospermia and Oligoasthenoteratozoospermia (OAT) infertile men.

MATERIALS AND METHODS

The present prospective study was carried out in Human Genetic Division, Department of Anatomy, Mahatma Gandhi Institute of Medical Sciences, Sevagram from June 2014 to July 2016. We have studied 110 asthenozoospermia and OAT infertile men whose semen profile indicated abnormal motility and 50 normal fertile controls. Of 110 infertile men, 70 had asthenozoospermia and 40 had OAT. Fractionations of spermatozoa were done in each semen sample on the basis of their motility by percoll gradients discontinuous technique. Long-range PCR was used for detection of 7436-bp deletions in sperm mtDNA and was confirmed by primer shift technique.

RESULTS

Overall eight subjects (8/110; 7.2%) of which six (6/70; 8.57%) asthenozoospermia and two (2/40; 5%) OAT had shown deletions of 7436-bp. In 40% percoll fraction had more non-motile spermatozoa than 80% percoll fraction. The non-motile spermatozoa in 40% percoll fractions showed more mtDNA deletions (7.2%) than the motile spermatozoa in 80% percoll fraction (2.7%). The sequencing of flanking regions of deleted mtDNA confirmed 7436-bp deletions. Interestingly, no deletions were found in control subjects.

CONCLUSION

Though, the frequency of 7436-bp deletions in sperm mtDNA was low in infertile cases but meaningful indications were there when results were compared with controls. It is indicated that large scale deletions 7436-bp of mtDNA is associated with abnormal sperm motility. The 7436-bp deletions of mtDNA in spermatozoa may be one of the important causes of dysfunction and non-motile sperm.

A novel large-scale deletion of the mitochondrial DNA of spermatozoa of men in north iran

Background

To investigate the level of correlation between large-scale deletions of the mitochondrial DNA (mtDNA) with defective sperm function.

Materials and Methods

In this analytic study, a total of 25 semen samples of the nor- mozoospermic infertile men from North of Iran were collected from the IVF center in an infertility clinic. The swim-up procedure was performed for the separation of spermatozoa into two groups; (normal motility group and abnormal motility group) by 2.0 ml of Ham’s F-10 medium and 1.0 ml of semen. After total DNA extraction, a long-range polymerase chain reaction (PCR) technique was used to determine the mtDNA deletions in human spermatozoa.

Results

The products of PCR analysis showed a common 4977 bp deletion and a novel 4866 bp deletion (flanked by a seven-nucleotide direct repeat of 5΄-ACCCCCT-3΄ within the deleted area) from the mtDNA of spermatozoa in both groups. However, the frequency of mtDNA deletions in abnormal motility group was significantly higher than the normal motility group (56, and 24% for 4866 bp-deleted mtDNA and, 52, and 28% for 4977 bp-deleted mtDNA, respectively).

Conclusion

It is suggested that large-scale deletions of the mtDNA is associated with poor sperm motility and may be a causative factor in the decline of fertility in men.

Relevance of genetic investigation in male infertility

Genetic causes can be directly responsible for various clinical conditions of male infertility and spermatogenic impairment. With the increased use of assisted reproduction technologies our understanding of genetic basis of male infertility has large implications not only for understanding the causes of infertility but also in determining the prognosis and management of such couples. For these reasons, the genetic investigations represent today an essential and useful tool in the treatment of male infertility. Several evidences are available for the clinical practice regarding the diagnosis; however, there are less information relative to the treatment of the genetic causes of male infertility. Focus of this review is to discuss the main and more common genetic causes of male infertility to better direct the genetics investigation in the treatment of spermatogenic impairment.