Genetic mutation of Cep76 results in male infertility due to abnormal sperm tail composition

The transition zone is a specialised gate at the base of cilia/flagella, which separates the ciliary compartment from the cytoplasm and strictly regulates protein entry. We identified a potential new regulator of the male germ cell transition zone, CEP76. We demonstrated that CEP76 was involved in the selective entry and incorporation of key proteins required for sperm function and fertility into the ciliary compartment and ultimately the sperm tail. In the mutant, sperm tails were shorter and immotile as a consequence of deficits in essential sperm motility proteins including DNAH2 and AKAP4, which accumulated at the sperm neck in the mutant. Severe annulus, fibrous sheath, and outer dense fibre abnormalities were also detected in sperm lacking CEP76. Finally, we identified that CEP76 dictates annulus positioning and structure. This study suggests CEP76 as a male germ cell transition zone protein and adds further evidence to the hypothesis that the spermatid transition zone and annulus are part of the same functional structure.

A metabolomic perspective on the mechanisms by which environmental pollutants and lifestyle lead to male infertility

The incidence of male infertility (MI) is rising annually. According to epidemiological studies, environmental pollution (e.g., organic, inorganic, and air pollutants), occupational exposure (e.g., high temperature, organic solvents, and pesticides), and poor lifestyle (e.g., diet, sleep, smoking, alcohol consumption, and exercise) are important non-genetic causative factors of MI. Due to multiple and complex causative factors, the dose-effect relationship, and the uncertainty of pathogenicity, the pathogenesis of MI is far from fully clarified. Recent data show that the pathogenesis of MI can be monitored by the metabolites in serum, seminal plasma, urine, testicular tissue, sperm, and other biological samples. It is considered that these metabolites are closely related to MI phenotypes and can directly reflect the individual pathological and physiological conditions. Therefore, qualitative and quantitative analysis of the metabolome, the related metabolic pathways, and the identification of biomarkers will help to explore the MI-related metabolic problems and provide valuable insights into its pathogenic mechanisms. Here, we summarized new findings in MI metabolomics biomarkers research and their abnormal metabolic pathways triggered by the presented non-genetic risk factors, providing a metabolic landscape of semen and seminal plasma in general MI patients. Then, we compared the similarities and differences in semen and seminal plasma biomarkers between MI patients exposed to environmental and poor lifestyle factors and MI patients in general, and summarized some common biomarkers. We provide a better understanding of the biological underpinnings of MI pathogenesis, which might offer novel diagnostic, prognostic, and precise treatment approaches to MI.

Clinical Utility of Sperm Function Tests in Predicting Male Fertility: A Systematic Review

Routine semen analysis provides considerable information regarding sperm parameters; however, it is not solely adequate to predict male fertility potential. In the past two decades, several advance sperm function tests have been developed. The present systematic review intends to assess the clinical utility of available advance sperm function tests in predicting the male fertility potential. A systematic literature search was conducted as per PRISMA guidelines using PubMed, MEDLINE, Google Scholar, and Cochrane Library. Different keywords either singly or in combination were used to retrieve the relevant articles related to sperm function tests, male fertility, and pregnancy outcomes. A total of 5169 articles were obtained, out of which 110 meeting the selection criteria were included in this review. The majorly investigated sperm function tests are hypo-osmotic swelling test, acrosome reaction test, sperm capacitation test, hemizona binding assay, sperm DNA fragmentation test, seminal reactive oxygen species test, mitochondrial dysfunction tests, antisperm antibody test, nuclear chromatin de-condensation (NCD) test, etc. The different advance sperm function tests analyse different aspects of sperm function. Hence, any one test may not be helpful to appropriately predict the male fertility potential. Currently, the unavailability of high-quality clinical data, robust thresholds, complex protocols, high cost, etc., are the limiting factors and prohibiting current sperm function tests to reach the clinics. Further multi-centric research efforts are required to fulfil the existing lacunas and pave the way for these tests to be introduced into the clinics.

A multi-modal approach to investigate Desmodium gangeticum's influence on stress-induced male infertility: In vivo, in vitro, and in silico assessments

Physical and psychological stress has an inverse relation with male libido and sperm quality. The present study investigates the potential fertility-enhancing properties of Desmodium gangeticum (DG) root extracts in male Wister rats subjected to immobilization-induced stress (SIMB). DG roots were extracted using n-hexane (HEDG), chloroform (CEDG), and water (AEDG). In the pilot study, aphrodisiac protentional was investigated at two doses (125 and 250 mg kg-1) of each extract. In the main study, the HEDG and AEDG at 125 and 250 mg kg-1 were challenged for the stress by immobilization (SIMB), for 6 h daily over 28 days. Parameters assessed included aphrodisiac effects, gonadosomatic index (GSI), semen quality, sperm quantity, fructose content, serum hormonal levels, testicular oxidative stress, and testicular histopathology. Additional in silico studies, including the lipid solubility index, molecular docking, molecular dynamics, and SymMap studies were conducted for validation. HEDG demonstrated significant aphrodisiac activity, improved - GSI, sperm quality and quantity, and fructose content, serum testosterone levels, histological changes induced by SIMB in the testes. Swiss ADME studies indicated Gangetin (a pterocarpan) had a high brain permeation index (4.81), a superior docking score (-8.22), and higher glide energy (-42.60), compared with tadalafil (-7.17). The 'Lig fit Prot' plot in molecular dynamics simulations revealed a strong alignment between Gangetin and phosphodiesterase type 5 (PDE5). HEDG exerts aphrodisiac effects by increasing blood testosterone levels and affecting PDE5 activity. The protective effects on spermatozoa-related parameters and testicular histological changes are attributed to the antioxidant and anti-inflammatory properties, of pterocarpan (gangetin).

CCDC157 is essential for sperm differentiation and shows oligoasthenoteratozoospermia-related mutations in men

Oligoasthenoteratospermia (OAT), characterized by abnormally low sperm count, poor sperm motility, and abnormally high number of deformed spermatozoa, is an important cause of male infertility. Its genetic basis in many affected individuals remains unknown. Here, we found that CCDC157 variants are associated with OAT. In two cohorts, a 21-bp (g.30768132_30768152del21) and/or 24-bp (g.30772543_30772566del24) deletion of CCDC157 were identified in five sporadic OAT patients, and 2 cases within one pedigree. In a mouse model, loss of Ccdc157 led to male sterility with OAT-like phenotypes. Electron microscopy revealed misstructured acrosome and abnormal head-tail coupling apparatus in the sperm of Ccdc157-null mice. Comparative transcriptome analysis showed that the Ccdc157 mutation alters the expressions of genes involved in cell migration/motility and Golgi components. Abnormal Golgi apparatus and decreased expressions of genes involved in acrosome formation and lipid metabolism were detected in Ccdc157-deprived mouse germ cells. Interestingly, we attempted to treat infertile patients and Ccdc157 mutant mice with a Chinese medicine, Huangjin Zanyu, which improved the fertility in one patient and most mice that carried the heterozygous mutation in CCDC157. Healthy offspring were produced. Our study reveals CCDC157 is essential for sperm maturation and may serve as a marker for diagnosis of OAT.

Novel Mutations Reduce Expression of Meiotic Regulators SYCE1 and BOLL in Testis of Azoospermic Men from West Bengal, India

We investigated the polymorphisms/mutations in synaptonemal complex central element protein 1 (SYCE1) and CDC25A mRNA-binding protein (BOLL) to test whether they increase the risk of azoospermia among Bengali-speaking men from West Bengal, India. Sanger's dideoxy sequencing was used to genotype 140 azoospermic individuals who tested negative for Y chromosome microdeletion and 120 healthy controls. In both cases and controls, qRT-PCR was used to determine the expression summary of SYCE1 and BOLL. The perceived harmful consequences of identified mutations were inferred using in silico analysis. Suitable statistical approaches were used to conduct the association study. We found SYCE1 177insT (ON245141), 10650T > G (ON257012), 10093insT (ON257013), 10653insG (ON292504), rs10857748A > G, rs10857749G > A, and rs10857750T > A and BOLL 7708T > A (ON245141insT), rs72918816T > C, and rs700655C > T variants with the prevalence of azoospermia. Data from qRT-PCR and in silico studies projected that the variations would either disrupt the transcript's natural splice junctions or cause probable damage to the structure of the genes' proteins. SYCE1 gene variants [177insT (ON245141), 10650T > G (ON257012), 10093insT (ON257013), 10653insG (ON292504), rs10857748A > G, rs10857749G > A, rs10857750T > A] and BOLL gene variants [7708T > A (ON245141insT), rs72918816T > C, rs700655C > T] reduce the expression of respective gene in testicular tissue among azoospermic male as revealed from qRT-PCR result. These genetic variations could be utilized as screening tools for male infertility to determine the best course of treatment in routine ART practise.

Deleterious variant in FAM71D cause male infertility with asthenoteratospermia

Asthenoteratospermia is a significant cause of male infertility. FAM71D (Family with sequence similarity 71, member D), as a novel protein exclusively expressed in the testis, has been found to be associated with sperm motility. However, the association of FAM71D mutation with male infertility has yet to be examined. Here, we conducted whole-exome sequencing and identified a homozygous missense mutation c.440G > A (p. Arg147Gln) of FAM71D in an asthenoteratospermia-affected man from a consanguineous family. The FAM71D variant is extremely rare in human population genome databases and predicted to be deleterious by multiple bioinformatics tools. Semen analysis indicated decreased sperm motility and obvious morphological abnormalities in sperm cells from the FAM71D-deficient man. Immunofluorescence assays revealed that the identified FAM71D mutation had an important influence on the assembly of sperm structure-related proteins. Furthermore, intra-cytoplasmic sperm injection (ICSI) treatment performed on the infertile man with FAM71D variant achieved a satisfactory outcome. Overall, our study identified FAM71D as a novel causative gene for male infertility with asthenoteratospermia, for which ICSI treatment may be suggested to acquire good prognosis. All these findings will provide effective guidance for genetic counselling and assisted reproduction treatments of asthenoteratospermia-affected subjects.

Autophagy core protein BECN1 is vital for spermatogenesis and male fertility in mice†

Mammalian spermatogenesis is a highly complex multi-step biological process, and autophagy has been demonstrated to be involved in the process of spermatogenesis. Beclin-1/BECN1, a core autophagy factor, plays a critical role in many biological processes and diseases. However, its function in spermatogenesis remains largely unclear. In the present study, germ cell-specific Beclin 1 (Becn1) knockout mice were generated and were conducted to determine the role of Becn1 in spermatogenesis and fertility of mice. Results indicate that Becn1 deficiency leads to reduced sperm motility and quantity, partial failure of spermiation, actin network disruption, excessive residual cytoplasm, acrosome malformation, and aberrant mitochondrial accumulation of sperm, ultimately resulting in reduced fertility in male mice. Furthermore, inhibition of autophagy was observed in the testes of germ cell-specific Becn1 knockout mice, which may contribute to impaired spermiogenesis and reduced fertility. Collectively, our results reveal that Becn1 is essential for fertility and spermiogenesis in mice.

Decreased AdipoR1 signaling and its implications for obesity-induced male infertility

Obesity is among the risk factors for male infertility. Although several mechanisms underlying obesity-induced male subfertility have been reported, the entire mechanism of obesity-induced male infertility still remains unclear. Here, we show that sperm count, sperm motility and sperm fertilizing ability were decreased in male mice fed a high-fat diet and that the expression of the AdipoR1 gene and protein was decreased, and the expression of pro-apoptotic genes and protein increased, in the testis from mice fed a high-fat diet. Moreover, we demonstrate that testes weight, sperm count, sperm motility and sperm fertilizing ability were significantly decreased in AdipoR1 knockout mice compared to those in wild-type mice; furthermore, the phosphorylation of AMPK was decreased, and the expression of pro-apoptotic genes and proteins, caspase-6 activity and pathologically apoptotic seminiferous tubules were increased, in the testis from AdipoR1 knockout mice. Furthermore, study findings show that orally administrated AdipoRon decreased caspase-6 activity and apoptotic seminiferous tubules in the testis, thus ameliorating sperm motility in male mice fed a high-fat diet. This was the first study to demonstrate that decreased AdipoR1/AMPK signaling led to increased caspase-6 activity/increased apoptosis in the testis thus likely accounting for male infertility.

Impact of semen microbiota on the composition of seminal plasma

Several studies have found associations between specific bacterial genera and semen parameters. Bacteria are known to influence the composition of their niche and, consequently, could affect the composition of the seminal plasma. This study integrated microbiota profiling and metabolomics to explore the influence of seminal bacteria on semen metabolite composition in infertile couples, revealing associations between specific bacterial genera and metabolite profiles. Amino acids and acylcarnitines were the predominant metabolite groups identified in seminal plasma. Different microbiota profiles did not result in globally diverse metabolite compositions in seminal plasma. Nevertheless, levels of specific metabolites increased in the presence of a dysbiotic microbiota. Urocanate was significantly increased in abnormal semen samples (adjusted P-value < 0.001) and enriched in samples dominated by Prevotella spp. (P-value < 0.05), which was previously linked to a negative impact on semen. Therefore, varying microbiota profiles can influence the abundance of certain metabolites, potentially having an immunomodulatory effect, as seen with urocanate.IMPORTANCEMale infertility is often considered idiopathic since the specific cause of infertility often remains unidentified. Recently, variations in the seminal microbiota composition have been associated with normal and abnormal semen parameters and may, therefore, influence male infertility. Bacteria are known to alter the metabolite composition of their ecological niches, and thus, seminal bacteria might affect the composition of the seminal fluid, crucial in the fertilization process. Our research indicates that distinct seminal microbiota profiles are not associated with widespread changes in the metabolite composition of the seminal fluid. Instead, the presence of particular metabolites with immunomodulatory functions, such as urocanate, could shed light on the interplay between seminal microbiota and variations in semen parameters.

Discovery of a novel miRNA involved in the regulation of male infertility in zebrafish

Azoospermia and asthenospermia are common manifestations of male infertility, but it needs further studies to understand the intrinsic regulation mechanism. As a popular model organism, zebrafish is often used to assess reproductive complications. In this study, by analyzing miRNA transcriptome of the mature triploid zebrafish testis afflicted with spermatogenic dysfunctions, leading to the identification of 36 miRNAs that are differentially expressed in comparison with diploid, which are predicted to target 2737 genes. Subsequent functional annotation of these genes pinpointed two miRNAs might association with spermatogenesis. Inhibitory experiments showed that NC_007115.7.7_998413 inhibited conducts a substantial decline in sperm density, and conducted lower embryo fertilization rate than control. And putative target genes qRT-PCR evaluation showed that spata2 was significant down-regulate upon inhibited NC_007115.7.7_998413. In summary, this research positions newly identified miRNA NC_007115.7.998413 as a regulatory factor in male zebrafish reproductive development, enhancing our comprehension of the molecular regulated pathways involved in spermatogenesis.

Scrutinizing the human TEX genes in the context of human male infertility

BACKGROUND

Infertility affects around 15% of all couples worldwide and is increasingly linked to variants in genes specifically expressed in the testis. Well-established causes of male infertility include pathogenic variants in the genes TEX11, TEX14, and TEX15, while few studies have recently reported variants in TEX13B, TEX13C, FAM9A (TEX39A), and FAM9B (TEX39B).

OBJECTIVES

We aimed at screening for novel potential candidate genes among the human TEX ("testis expressed") genes as well as verifying previously described disease associations in this set of genes.

MATERIALS AND METHODS

To this end, we screened the exome sequencing data of 1305 men, including 1056 crypto- and azoospermic individuals, and determined cell-specific expression by analyzing testis-specific single-cell RNA sequencing data for genes with identified variants. To investigate the overarching role in male fertility, we generated testis-specific knockdown (KD) models of all 10 orthologous TEX genes in Drosophila melanogaster.

RESULTS

We detected rare potential disease-causing variants in TEX10, TEX13A, TEX13B, TEX13C, TEX13D, ZFAND3 (TEX27), TEX33, FAM9A (TEX39A), and FAM9B (TEX39B), in 28 infertile men, of which 15 men carried variants in TEX10, TEX27, and TEX33. The KD of TEX2, TEX9, TEX10, TEX13, ZFAND3 (TEX27), TEX28, TEX30, NFX1 (TEX42), TEX261, and UTP4 (TEX292) in Drosophila resulted in normal fertility.

DISCUSSION

Based on our findings, the autosomal dominant predicted genes TEX10 and ZFAND3 (TEX27) and the autosomal recessive predicted gene TEX33, which all three are conceivably required for germ cell maturation, were identified as novel potential candidate genes for human non-obstructive azoospermia. We additionally identified hemizygous loss-of-function (LoF) variants in TEX13B, TEX13C, and FAM9A (TEX39A) as unlikely monogenic culprits of male infertility as LoF variants were also found in control men.

CONCLUSION

Our findings concerning the X-linked genes TEX13B, TEX13C, and FAM9A (TEX39A) contradict previous reports and will decrease false-positive reports in genetic diagnostics of azoospermic men.

Unravelling the epigenetic impact: Oxidative stress and its role in male infertility-associated sperm dysfunction

Male infertility is a multifactorial condition influenced by epigenetic regulation, oxidative stress, and mitochondrial dysfunction. Oxidative stress-induced damage leads to epigenetic modifications, disrupting gene expression crucial for spermatogenesis and fertilization. Paternal exposure to oxidative stress induces transgenerational epigenetic alterations, potentially impacting male fertility in offspring. Mitochondrial dysfunction impairs sperm function, while leukocytospermia exacerbates oxidative stress-related sperm dysfunction. Therefore, this review focuses on understanding these mechanisms as vital for developing preventive strategies, including targeting oxidative stress-induced epigenetic changes and implementing lifestyle modifications to prevent male infertility. This study investigates how oxidative stress affects the epigenome and sperm production, function, and fertilization. Unravelling the molecular pathways provides valuable insights that can advance our scientific understanding. Additionally, these findings have clinical implications and can help to address the significant global health issue of male infertility.

Nickel-induced oxidative stress causes cell death in testicles: implications for male infertility

Aligarh region is well known for its lock industry. This lock industry utilises nickel for electroplating. There have been informal reports of infertility in men and women living near the lock industry. We analysed field water samples to investigate this link, and the results showed considerable nickel contamination. To further validate our results, we exposed male rats to relevant nickel levels in drinking water. This experimental exposure resulted in abnormal sperm morphology, decline in sperm count, significant change in activities of antioxidant enzymes, pronounced oxidative stress in the rat spermatocytes and decrease in serum testosterone level, as well as damage in the hypothalamus and pituitary (in all cases, the changes were most significant at the highest concentration used i.e 2.5 mg/l). The breeding experiments showed decline in live birth rate, while pups did not survive post birth in cages where males were given 2 and 2.5 mg/l concentrations of nickel in drinking water prior to mating. Our data strongly indicate a link between industrial nickel exposure and male infertility.

Serum exosomes from hepatitis B virus-infected patients inhibit glycolysis in Sertoli cells via miR-122-5p/ALDOA axis

Hepatitis B virus (HBV) infection is associated with male infertility. The mechanism includes an increase in chromosomal instability in sperm, which has an adverse effect on sperm viability and function. Sertoli cells (SCs) are vital in spermatogenesis because they use glycolysis to provide energy to germ cells and themselves. HBV infection impairs sperm function. However, whether HBV infection disrupts energy metabolism in SCs remains unclear. This study aimed to determine the role of serum exosomes of HBV-infected patients in SC viability and glycolysis. Serum exosomes were obtained from 30 patients with (HBV+_exo) or without (HBV-_exo) HBV infection using high-speed centrifugation and identified by transmission electron microscopy and western blot analysis. Cell viability is determined by CCK-8 assay. Glycolysis is determined by detecting extracellular acidification rate and ATP levels. miR-122-5p expression levels are detected by quantitative RT-PCR, and a dual-luciferase gene reporter assay confirms the downstream target gene of miR-122-5p. Protein expression is determined by western blot analysis. The results show that HBV+ _exo inhibited cell viability, extracellular acidification rate, and ATP production of SCs. miR-122-5p is highly expressed in HBV+ _exo compared with that in HBV-_exo. Furthermore, HBV+ _exo is efficiently taken up by SCs, whereas miR-122-5p is efficiently transported to SCs. miR-122-5p overexpression downregulates ALDOA expression and inhibits SC viability and glycolysis. However, ALDOA overexpression reverses the effects of miR-122-5p and HBV+ _exo on SC viability and glycolysis. HBV+ _exo may deliver miR-122-5p to target ALDOA and inhibit SC viability and glycolysis, thus providing new therapeutic ideas for treating HBV-associated male infertility.

Evaluation of telomere length, reactive oxygen species, and apoptosis in spermatozoa of patients with oligospermia

50% of cases of infertility are caused by male factor, which acquired or congenital problems may bring on. Male infertility can be caused by oligospermia and asthenozoospermia, which are common. Since the same mutations that cause azoospermia in some people also cause oligozoospermia in others, oligozoospermia may be thought of as a less severe form of azoospermia. Studies have demonstrated telomere length, catalase activity, super oxide dismutase (SOD), and DNA fragmentation can be influential factors for male infertility. The amount of apoptosis, oxidative stress factors, telomere length, and DNA fragmentation were some aspects of healthy sperm that we chose to look into in this study and compare to oligospermia individuals. Oligospermia patients (n = 24) and fertile men (n = 27) semen samples were collected, and the apoptosis rate of sperms in both groups was analyzed (Flow cytometry). Also, gene expression of apoptotic and antiapoptotic markers and telomere length were examined (real-time polymerase chain reaction). The sperm DNA fragmentation kit was used to determine DNA fragmentation and to evaluate catalase and SOD activity; the specific kits and methods were utilized. Higher expression levels of caspase3 (p = .0042), caspase8 (p = .0145), caspase9 (p = .0275), and BAX (p = .0202) mRNA were observed in patients who had oligospermia. In contrast, lower mRNA expression of BCL-2 (p = .0009) was detected in this group. In addition, telomere length was decreased in the oligospermia group (p < .0001) compared to the health group. Moreover, the frequency of apoptosis is induced in patients (p = .0026). The catalase activity is low (p = .0008), but the SOD activity is high (p = .0015) in the patient group. As a result of our findings, we may list the sperm cell apoptosis rate, telomere length, the degree of sperm DNA fragmentation, and lastly, the measurement of significant and efficient oxidative stress markers like SOD and catalase in semen plasma among the principal diagnostic characteristics for oligospermia. Future studies will be better able to treat oligospermia by showing whether these indicators are rising or falling.

The role of oral antioxidants in the improvement of sperm parameters in infertile men

PURPOSE

A variety of pathologic conditions may increase oxidative stress in semen resulting in structural modifications to spermozoa's plasma membrane that interfere with sperm motility, morphology, and count. Antioxidants are currently being marketed to treat male infertility. In semen, antioxidants may decrease oxidative stress and potentially improve sperm parameters. In this narrative, mini-review we evaluated the effectiveness of antioxidants in infertility.

METHODS

This mini-review of the current literature has been carried out through searching of the PubMed and Google scholar databases.

RESULTS AND CONCLUSIONS

The literature review suggests that there is evidence that oral antioxidants such as selenium, carnitine, zinc, coenzymeQ10, vitamins E and C, etc. alone or in combinations, improve sperm count, motility, morphology as well as pregnancy rates in infertile men with idiopathic oligoasthenospermia. Unfortunately, most of these studies are poorly designed, limited by sample size, varying in dosage, differing in primary end points, and most notably lacking live birth data. Importantly, large randomized, well-designed, placebo-controlled trials are needed.

Metabolic characterization of human sperm cells using the Seahorse metabolic flux analyzer

BACKGROUND

The concerning trend on male infertility global prevalence, together with the unexplainable causes in half of those cases, highlights that there are still aspects of this disease to be understood and solved. To address this issue, one should not only be aware of the limitations of the implemented diagnostic tools, but also understand the sperm cell in depth, structurally, biochemically, molecularly in order to develop reliable and ready-to-be new/improved diagnostic tools. In this sense, the sperm cells metabolism, highly related to its functionality, seems to be a promising aspect to explore. Though there is much information on the human sperm metabolism, there is still a lack of a quick integrated and comprehensive analysis that may be introduced with the potential to reveal innovative clinically relevant information.

OBJECTIVES

Find metabolic details on human sperm that can be accessed easily, in real time and using few cells, relying on the bivalent potential of the Seahorse flux analyzer (SFA).

RESULTS

We have obtained standard records on human sperm cells' oxygen consumption rate (OCR) and extracellular acidification rate (ECAR), that together with the metabolic metrics provided information on sperm cells' oxidative and glycolytic metabolism. Furthermore, a metabolic interindividual variation was observed.

DISCUSSION AND CONCLUSION

Although the comparison with other species or cell types is not linear and warrant further studies, the metabolic profile of human sperm cells seems to be similar to that of other species. Altogether our results corroborate the value of SFA for metabolic human sperm cell analysis, warranting new studies, and anticipating several applications in the male infertility field.

Advancements in the ERK1/2 Signaling Pathway Affecting Male Reproduction

Male infertility, age-related changes, and tumors have been increasingly studied in the field of male reproductive health due to the emergence of environmental stressors, declining fertility rates, and aging populations. Numerous studies have demonstrated that the ERK1/2 signaling pathway plays a significant role in male reproduction. The ERK1/2 pathway is associated with several signaling pathways and has a complex interplay that influences the spermatogenic microenvironment, sperm viability, gonadal axis regulation, as well as resistance to testicular aging and tumors. Moreover, the ERK1/2 pathway directly or indirectly regulates testicular somatic cells, which are crucial for maintaining spermatogenesis and microenvironment regulation. Given the critical role of the ERK1/2 signaling pathway in male reproductive health, comprehensive exploration of its multifaceted effects on male reproduction and underlying mechanisms is necessary. This study aims to provide a solid foundation for in-depth research in the field of male reproduction and further enhance the reproductive health of males.

SperMD: the expression atlas of sperm maturation

The impairment of sperm maturation is one of the major pathogenic factors in male subfertility, a serious medical and social problem affecting millions of global couples. Regrettably, the existing research on sperm maturation is slow, limited, and fragmented, largely attributable to the lack of a global molecular view. To fill the data gap, we newly established a database, namely the Sperm Maturation Database (SperMD, http://bio-add.org/SperMD ). SperMD integrates heterogeneous multi-omics data (170 transcriptomes, 91 proteomes, and five human metabolomes) to illustrate the transcriptional, translational, and metabolic manifestations during the entire lifespan of sperm maturation. These data involve almost all crucial scenarios related to sperm maturation, including the tissue components of the epididymal microenvironment, cell constituents of tissues, different pathological states, and so on. To the best of our knowledge, SperMD could be one of the limited repositories that provide focused and comprehensive information on sperm maturation. Easy-to-use web services are also implemented to enhance the experience of data retrieval and molecular comparison between humans and mice. Furthermore, the manuscript illustrates an example application demonstrated to systematically characterize novel gene functions in sperm maturation. Nevertheless, SperMD undertakes the endeavor to integrate the islanding omics data, offering a panoramic molecular view of how the spermatozoa gain full reproductive abilities. It will serve as a valuable resource for the systematic exploration of sperm maturation and for prioritizing the biomarkers and targets for precise diagnosis and therapy of male subfertility.

The role of the intrinsic pathway of apoptosis in human ejaculated sperm damage under a state of scrotal heat stress

PURPOSE

The study aimed to determine the associations among standard sperm characteristics and oxidative/apoptotic markers in ejaculated sperm of men exposed to prolonged scrotal hyperthermia of either environmental or clinical origin.

METHODS

The original study design included four research groups: professional drivers (n = 54), infertile men with varicocele (n = 78), infertile men not exposed to prolonged genital heat stress (n = 37), and fertile individuals serving as the control group (n = 29). Standard semen analysis was performed according to the 5th WHO laboratory manual. The following oxidative and apoptotic parameters of sperm were investigated: mitochondrial superoxide anion generation (MitoSOX Red dye), phosphatidylserine externalization (Annexin V binding assay), mitochondrial membrane potential (JC-1 dye), DNA fragmentation (TUNEL/PI assay), and membrane fluidity (merocyanine 540 dye).

RESULTS

All the studied groups presented a strong deterioration in routine sperm parameters and a strongly apoptotic phenotype in sperm, characterized by both decreased mitochondrial membrane potential and enhanced DNA fragmentation, regardless of the thermal insult. Significant induction of mitochondrial superoxide anion generation was noted only in the groups exposed to genital heat stress. A positive correlation between the production of superoxide anion in the mitochondrial chain and the level of DNA fragmentation in drivers was also noted.

CONCLUSION

Long-term exposure to scrotal hyperthermia in real-life situations is sufficient to reduce sperm quality in humans. The thermal stress directly induces the oxidative stress cascade in ejaculated sperm, affecting the plasma membrane fluidity, mitochondrial homeostasis, and sperm DNA integrity.

Relationship between degree of methylation of sperm long interspersed nuclear element-1 (LINE-1) gene and alteration of sperm parameters and age: a meta-regression analysis

INTRODUCTION

The long interspersed nuclear element-1 (LINE1) gene is a retrotransposon whose methylation status appears to play a role in spermatogenesis, the outcome of assisted reproductive techniques (ART), and even in recurrent pregnancy loss (RPL). Advanced paternal age appears associated with altered sperm parameters, RPL, poor ART outcomes, and compromised offspring health. The methylation status of LINE1 has been reported to be affected by age. The latest meta-analysis on the LINE1 methylation pattern in spermatozoa found no significant differences in methylation levels between infertile patients and fertile controls. However, to the best of our knowledge, no updated meta-analysis on this topic has been published recently. Furthermore, no comprehensive meta-regression analysis was performed to investigate the association between sperm LINE1 methylation pattern and age.

OBJECTIVES

To provide an updated and comprehensive systematic review and meta-analysis on sperm LINE1 gene methylation degree in patients with abnormal sperm parameters compared to men with normal sperm parameters and to probe the association between sperm LINE1 methylation status and age and/or sperm concentration.

METHODS

This meta-analysis was registered in PROSPERO (registration n. CRD42023397056). It was performed according to the MOOSE guidelines for Meta-analyses and Systematic Reviews of Observational Studies and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols (PRISMA-P). Only original articles evaluating LINE1 gene methylation in spermatozoa from patients with infertility or abnormalities in one or more sperm parameters compared to fertile or normozoospermic men were included.

RESULTS

Of 192 abstracts evaluated for eligibility, only 5 studies were included in the quantitative synthesis, involving a total of 340 patients and 150 controls. Our analysis showed no significant difference in LINE1 gene methylation degree in patients with infertility and/or abnormal sperm parameters compared to fertile controls and/or men with normal sperm parameters, although there was significant heterogeneity across studies. No significant evidence of publication bias was found, and no study was sensitive enough to alter the results. In meta-regression analysis, we found that the results were independent of both ages and sperm concentration. A sub-analysis examining patients and controls separately was also conducted and we found a trend for a positive correlation between LINE1 methylation and sperm concentration in the control group only.

CONCLUSIONS

The results of this systematic review and meta-analysis do not suggest a determining role of sperm LINE1 gene methylation degree in patients with infertility and/or abnormal sperm parameters. Therefore, we do not suggest including LINE1 in the genetic panel of prospective studies aimed at identifying the most representative and cost-effective genes to be analyzed in couples undergoing ART cycles.

Deleterious genetic changes in AGTPBP1 result in teratozoospermia with sperm head and flagella defects

Approximately 10%-15% of couples worldwide are infertile, and male factors account for approximately half of these cases. Teratozoospermia is a major cause of male infertility. Although various mutations have been identified in teratozoospermia, these can vary among ethnic groups. In this study, we performed whole-exome sequencing to identify genetic changes potentially causative of teratozoospermia. Out of seven genes identified, one, ATP/GTP Binding Protein 1 (AGTPBP1), was characterized, and three missense changes were identified in two patients (Affected A: p.Glu423Asp and p.Pro631Leu; Affected B: p.Arg811His). In those two cases, severe sperm head and tail defects were observed. Moreover, AGTPBP1 localization showed a fragmented pattern compared to control participants, with specific localization in the neck and annulus regions. Using murine models, we found that AGTPBP1 is localized in the manchette structure, which is essential for sperm structure formation. Additionally, in Agtpbp1-null mice, we observed sperm head and tail defects similar to those in sperm from AGTPBP1-mutated cases, along with abnormal polyglutamylation tubulin and decreasing △-2 tubulin levels. In this study, we established a link between genetic changes in AGTPBP1 and human teratozoospermia for the first time and identified the role of AGTPBP1 in deglutamination, which is crucial for sperm formation.

Insertional Variations of Human Endogenous Virus K6 and K11 in Normozoospermic Men

Male infertility is a multifactorial heterogeneous reproductive disorder in which genetic, epigenetic, and environmental factors play a role in the development of disease. Recent studies have shown that retrotransposon expression alterations may be related to impairment of spermatogenesis. Therefore, in this pilot study, we aimed to investigate whether HERV-K6 and HERV-K11 insertional variations have a role in idiopathic infertility among normozoospermic men. Genomic DNA isolated from the blood samples of 41 infertile normozoospermic and 45 fertile normozoospermic men were analyzed by inter-retrotransposon polymorphism polymerase chain reaction. HERV-K6 variation rates in the infertile and the fertile group were 0-58.3% and 0-53.4%, respectively. The variation rates of HERV-K11 were 0-75.0% in infertile and 0-77.8% in fertile men. The HERV-K6 and HERV-K11 insertion rates of the fertile group were higher than the infertile group (P < 0.0001 and P = 0.007, respectively). The findings of the study suggest that HERV-K6 and HERV-K11 retrotransposon insertion show variation among individuals, and their insertions might be associated with male infertility.

A variant in sperm-specific glycolytic enzyme enolase 4 (ENO4) causes human male infertility

BACKGROUND

Although defects in sperm morphology and physiology lead to male infertility, in many instances, the exact disruption of molecular pathways in a given patient is often unknown. The glycolytic pathway is an essential process to supply energy in sperm cell motility. Enolase 4 (ENO4) is crucial for the glycolytic process, which provides the energy for sperm cells in motility. ENO4 is located in the sperm principal piece and is essential for the motility and organization of the sperm flagellum. In the present study, we characterized a family with asthenozoospermia and abnormal sperm morphology as a result of a variant in the enolase 4 (ENO4) gene.

METHODS

Computer-assisted semen analysis, papanicolaou smear staining and scanning electron microscopy were used to examine sperm motility and morphology for semen analysis in patients. For genetic analysis, whole-exome sequencing followed by Sanger sequencing was performed.

RESULTS

Two brothers in a consanguineous family were being clinically investigated for sperm motility and morphology issues. Genetic analysis by whole-exome sequencing revealed a homozygous variant [c.293A>G, p.(Lys98Arg)] in the ENO4 gene that segregated with infertility in the family, shared by affected but not controls.

CONCLUSIONS

In view of the association of asthenozoospermia and abnormal sperm morphology in Eno4 knockout mice, we consider this to be the first report describing the involvement of ENO4 gene in human male infertility. We also explore the possible involvement of another variant in explaining other phenotypic features in this family.

Utility of vitamin C in ameliorating citalopram-induced testicular toxicity via modulating nitro-oxidative stress and apoptosis in mice

There is a growing concern that antidepressant drugs impair sexual function and adversely impact spermatogenesis and male fertility. Vitamin C is a natural antioxidant that plays a vital role in the male reproductive system. The present study investigated the ameliorating potential of vitamin C against citalopram (CTL)-evoked testicular toxicity and spermatogenesis impairment in mice. Mice were randomly divided into six groups: control, CTL, vitamin C 100, vitamin C 200, CTL plus vitamin C 100, and CTL plus vitamin C 200. Adult male mice were intraperitoneally (ip) injected with 10 mg/kg of CTL for 35 days with or without vitamin C. At the end of the study, body and testes weight, sperm parameters, histopathology of testes, testosterone level, testicular levels of malondialdehyde (MDA), nitric oxide (NO), total antioxidant capacity (TAC), and apoptosis (TUNEL assay) were evaluated. Our findings revealed that vitamin C restored spermatogenesis by improving sperm count, motility, viability, morphology, and chromatin integrity. Testosterone levels and testes histopathology were significantly improved in the vitamin C-administrated groups. Furthermore, vitamin C administration markedly alleviated CTL-induced nitro-oxidative damage, enhancing TAC levels, and reducing NO and MDA levels. Whilst CTL therapy induced a significant increase in the number of TUNEL-positive cells compared to the control, the administration of vitamin C significantly prevented the apoptotic effects of CTL. Together, vitamin C therapy protects against CTL-induced testicular damage via mitigating nitro-oxidative stress and apoptosis, which provides evidence for vitamin C as a beneficial therapy against antidepressant drug-associated reproductive toxicity and male sub/infertility.

Single-cell RNA sequencing and UPHLC-MS/MS targeted metabolomics offer new insights into the etiological basis for male cattle-yak sterility

The variety of species can be efficiently increased by interspecific hybridization. However, because the males in the hybrid progeny are usually sterile, this heterosis cannot be employed when other cattle and yaks are hybridized. While some system-level studies have sought to explore the etiological basis for male cattle-yak sterility, no systematic cellular analyses of this phenomenon have yet been performed. Here, single-cell RNA sequencing and UPHLC-MS/MS targeted metabolomics methods were used to study the differences in testicular tissue between 4-year-old male yak and 4-year-old male cattle-yak, providing new and comprehensive insights into the causes of male cattle-yak sterility. Cattle-yak testes samples detected 6 somatic cell types and one mixed germ cell type. Comparisons of these cell types revealed the more significant differences in Sertoli cells (SCs) and [Leydig cells and myoid cells (LCs_MCs)] between yak and cattle-yak samples compared to other somatic cell clusters. Even though the LCs and MCs from yaks and cattle-yaks were derived from the differentiation of the same progenitor cells, a high degree of overlap between LCs and MCs was observed in yak samples. Still, only a small overlap between LCs and MCs was observed in cattle-yak samples. Functional enrichment analyses revealed that genes down-regulated in cattle-yak SCs were primarily enriched in biological activity, whereas up-regulated genes in these cells were enriched for apoptotic activity. Furthermore, the genes of up-regulated in LCs_MCs of cattle-yak were significantly enriched in enzyme inhibitor and molecular function inhibitor activity. On the other hand, the genes of down-regulated in these cells were enriched for signal receptor binding, molecular function regulation, positive regulation of biological processes, and regulation of cell communication activity. The most significant annotated differences between yak and cattle-yak LCs_MCs were associated with cell-to-cell communication. While yak LCs_MCs regulated spermatogenic cells at spermatogonia, spermatocyte, and spermatid levels, no such relationships were found between cattle-yak LCs_MCs and germ cells. This may suggest that the somatic niche in male cattle-yak testes is a microenvironment that is ultimately not favorable for spermatogenesis.

ARRDC5 deficiency impairs spermatogenesis by affecting SUN5 and NDC1

Sperm with normal morphology and motility are essential for successful fertilization, and the strong attachment of the sperm head-tail coupling apparatus to the nuclear envelope during spermatogenesis is required to ensure the integrity of sperm for capacitation and fertilization. Here, we report that Arrdc5 is associated with spermatogenesis. The Arrdc5 knockout mouse model showed male infertility characterized by a high bent-head rate and reduced motility in sperm, which led to capacitation defects and subsequent fertilization failure. Through mass spectrometry, we found that ARRDC5 affects spermatogenesis by affecting NDC1 and SUN5. We further found that ARRDC5 might affect the vesicle-trafficking protein SEC22A-mediated transport and localization of NDC1, SUN5 and other head-tail coupling apparatus-related proteins that are responsible for initiating the attachment of the sperm head and tail. We finally performed intracytoplasmic sperm injection as a way to explore therapeutic strategies. Our findings demonstrate the essential role and the underlying molecular mechanism of ARRDC5 in anchoring the sperm head to the tail during spermatogenesis.

Higher incidence of embryonic defects in mouse offspring conceived with assisted reproduction from fathers with sperm epimutations

Assisted reproductive technologies (ART) account for 1-6% of births in developed countries. While most children conceived are healthy, increases in birth and genomic imprinting defects have been reported; such abnormal outcomes have been attributed to underlying parental infertility and/or the ART used. Here, we assessed whether paternal genetic and lifestyle factors, that are associated with male infertility and affect the sperm epigenome, can influence ART outcomes. We examined how paternal factors, haploinsufficiency for Dnmt3L, an important co-factor for DNA methylation reactions, and/or diet-induced obesity, in combination with ART (superovulation, in vitro fertilization, embryo culture and embryo transfer), could adversely influence embryo development and DNA methylation patterning in mice. While male mice fed high-fat diets (HFD) gained weight and showed perturbed metabolic health, their sperm DNA methylation was minimally affected by the diet. In contrast, Dnmt3L haploinsufficiency induced a marked loss of DNA methylation in sperm; notably, regions affected were associated with neurodevelopmental pathways and enriched in young retrotransposons, sequences that can have functional consequences in the next generation. Following ART, placental imprinted gene methylation and growth parameters were impacted by one or both paternal factors. For embryos conceived by natural conception, abnormality rates were similar for WT and Dnmt3L+/- fathers. In contrast, paternal Dnmt3L+/- genotype, as compared to WT fathers, resulted in a 3-fold increase in the incidence of morphological abnormalities in embryos generated by ART. Together, the results indicate that embryonic morphological and epigenetic defects associated with ART may be exacerbated in offspring conceived by fathers with sperm epimutations.

Phase-separated CCER1 coordinates the histone-to-protamine transition and male fertility

Idiopathic fertility disorders are associated with mutations in various genes. Here, we report that coiled-coil glutamate-rich protein 1 (CCER1), a germline-specific and intrinsically disordered protein (IDP), mediates postmeiotic spermatid differentiation. In contrast, CCER1 deficiency results in defective sperm chromatin compaction and infertility in mice. CCER1 increases transition protein (Tnp1/2) and protamine (Prm1/2) transcription and mediates multiple histone epigenetic modifications during the histone-to-protamine (HTP) transition. Immiscible with heterochromatin in the nucleus, CCER1 self-assembles into a polymer droplet and forms a liquid-liquid phase-separated condensate in the nucleus. Notably, we identified loss-of-function (LoF) variants of human CCER1 (hCCER1) in five patients with nonobstructive azoospermia (NOA) that were absent in 2713 fertile controls. The mutants led to premature termination or frameshift in CCER1 translation, and disrupted condensates in vitro. In conclusion, we propose that nuclear CCER1 is a phase-separated condensate that links histone epigenetic modifications, HTP transitions, chromatin condensation, and male fertility.

Proteomics of human spermatozoa

Proteomic methodologies offer a robust approach to identify and quantify thousands of proteins from semen components in both fertile donors and infertile patients. These strategies provide an unprecedented discovery potential, which many research teams are currently exploiting. However, it is essential to follow a suitable experimental design to generate robust data, including proper purification of samples, appropriate technical procedures to increase identification throughput, and data analysis following quality criteria. More than 6000 proteins have been described so far through proteomic analyses in the mature sperm cell, increasing our knowledge on processes involved in sperm function, intercommunication between spermatozoa and seminal fluid, and the transcriptional origin of the proteins. These data have been complemented with comparative studies to ascertain the potential role of the identified proteins on sperm maturation and functionality, and its impact on infertility. By comparing sperm protein profiles, many proteins involved in the acquisition of fertilizing ability have been identified. Furthermore, altered abundance of specific protein groups has been observed in a wide range of infertile phenotypes, including asthenozoospermia, oligozoospermia, and normozoospermia with unsuccessful assisted reproductive techniques outcomes, leading to the identification of potential clinically useful protein biomarkers. Finally, proteomics has been used to evaluate alterations derived from semen sample processing, which might have an impact on fertility treatments. However, the intrinsic heterogeneity and inter-individual variability of the semen samples have resulted in a relatively low overlap among proteomic reports, highlighting the relevance of combining strategies for data validation and applying strict criteria for proteomic data analysis to obtain reliable results. This mini-review provides an overview of the most critical steps to conduct robust sperm proteomic studies, the most relevant results obtained so far, and potential next steps to increase the impact of sperm proteomic data.

CCDC146 is required for sperm flagellum biogenesis and male fertility in mice

Multiple morphological abnormalities of the flagella (MMAF) is a severe disease of male infertility, while the pathogenetic mechanisms of MMAF are still incompletely understood. Previously, we found that the deficiency of Ccdc38 might be associated with MMAF. To understand the underlying mechanism of this disease, we identified the potential partner of this protein and found that the coiled-coil domain containing 146 (CCDC146) can interact with CCDC38. It is predominantly expressed in the testes, and the knockout of this gene resulted in complete infertility in male mice but not in females. The knockout of Ccdc146 impaired spermiogenesis, mainly due to flagellum and manchette organization defects, finally led to MMAF-like phenotype. Furthermore, we demonstrated that CCDC146 could interact with both CCDC38 and CCDC42. It also interacts with intraflagellar transport (IFT) complexes IFT88 and IFT20. The knockout of this gene led to the decrease of ODF2, IFT88, and IFT20 protein levels, but did not affect CCDC38, CCDC42, or ODF1 expression. Additionally, we predicted and validated the detailed interactions between CCDC146 and CCDC38 or CCDC42, and built the interaction models at the atomic level. Our results suggest that the testis predominantly expressed gene Ccdc146 is essential for sperm flagellum biogenesis and male fertility, and its mutations might be associated with MMAF in some patients.

The methylation status of GATA3 potentially predicts the outcomes of assisted reproductive technologies

Evaluation of methylation status of genes in sperm samples has been suggested for diagnosis of male infertility as well as prognosis of assisted reproductive technologies (ART) outcomes. In this study, we compared the methylation pattern of the GATA3 gene in infertile and fertile men as well as in infertile men with positive and negative ART outcome based on clinical pregnancy. Ejaculates were obtained from 42 infertile men with a negative ART outcome (group 1), 30 infertile men with a positive ART outcome (group 2), and 21 fertile men (control). Then, samples were subjected to genomic DNA isolation and subsequent TUNEL assay and methylation-specific PCR. The number of infertile men with at least one methylated allele of GATA3 was significantly higher compared to the control group (p = 0.022). Also, the number of patients with at least one methylated allele was significantly higher in group 1 compared to group 2 (p = 0.013). Moreover, the TUNEL assay revealed that the amount of sperm DNA fragmentation is higher in group 1 compared to group 2 (p = 0.008). The findings of our study demonstrated that the degree of GATA3 methylation can potentially differentiate between infertile and fertile men and more importantly can potentially predict the outcome of ART.

MACS-DGC sperm preparation method resulted in high-quality sperm, top-quality embryo, and higher blastocyst rate in male factor infertile couples with high DNA fragmented sperm

Conventional sperm selection based on motility and morphology fails to provide detailed information on sperm functional and molecular status. Magnetic-activated cell sorting (MACS) protocol aims to optimize this process by selecting apoptotic sperm cells. Phospholipase C zeta-1 (PLCz1) is a physiological stimulus for oocyte activation and early embryonic development. The purpose of this study was to examine seminal parameters, DNA fragmentation index (DFI), and PLCz1 expression levels in MACS-DGC sorted specimens (DFI > 30%) and assess early development in resulting embryos. Semen specimens from 60 patients diagnosed with male factor infertility were collected and processed by either density gradient centrifugation (DGC) or MACS-DGC protocols. Pre and post-preparation analysis was performed. PLCz1 expression was assessed using the RT-PCR method. Retrieved eggs from their partners were divided into two groups in which they were injected with different sorted sperm. The fertilization rate and embryonic development were evaluated. While sperm's progressive motility and morphology significantly improved, there was a substantial decline in DFI following MACS-DGC. Fertilization rates were almost the same between the groups, and the latter resulted in remarkably more top-quality embryos and more blastocysts. PLCz1 expression was considerably higher in the MACS-DGC group. By eliminating apoptotic cells, the MACS-DGC technique could sort highly PLCz1-expressed sperm, optimize sperm selection in individuals with elevated DFI, development of resulting embryos.

Metabolomic analysis of seminal fluids in infertile individuals

OBJECTIVE

Infertility impacts a substantial number of couples worldwide, and about 50% of cases are linked to male factors. The analysis of seminal fluid composition can improve diagnostic accuracy and offer deeper insights into the pathophysiology of male factor infertility. This study seeks to identify novel markers for diagnosing and treating male infertility by comparing organic acid profiles in the seminal fluid of individuals with normospermia, oligospermia, and azoospermia.

PATIENTS AND METHODS

Semen samples were collected from men with normospermia, oligospermia, and azoospermia. The organic acid profile in the seminal fluid was analyzed using liquid chromatography-mass spectrometry/mass spectrometry (LC/MS-MS). Data analysis was performed using SPSS and MetaboAnalyst.

RESULTS

The study revealed significant differences in metabolite levels among normospermic, oligospermic, and azoospermic individuals. In groups with oligospermia, there were significant decreases in the levels of 2-OH-Isovaleric Acid, 3-Methyl-2-Oxovaleric Acid, Ethyl-Malonic Acid, Citric Acid, Oxoproline, Malic Acid, N-Acetyl-Aspartic Acid, Suberic Acid, Glutaconic Acid, and Succinic Acid. Similarly, individuals with azoospermia exhibited a notable reduction in the levels of Citric Acid, Malic Acid, and Suberic Acid. Furthermore, according to the Variable Importance in the Projection (VIP) score analysis, Ethyl-Malonic Acid, Glycolic Acid, and 3-Methyl-2-Oxovaleric Acid were identified as crucial factors for diagnosis and potential treatment strategies.

CONCLUSIONS

The data obtained from the study highlights the significant potential of metabolites in assessing infertility and gaining a more in-depth understanding of the underlying pathological mechanisms.

New allele of mouse DNA/RNA helicase senataxin causes meiotic arrest and infertility

In brief

A new allele of the senataxin gene Setxspcar3 causes meiotic arrest of spermatocytes with aberrant DNA damage and accumulation of R-loops.

Abstract

An unbiased screen for discovering novel mouse genes for fertility identified the spcar3, spermatocyte arrest 3, mutant phenotype. The spcar3 mutation identified a new allele of the Setx gene, encoding senataxin, a DNA/RNA helicase that regulates transcription termination by resolving DNA/RNA hybrid R-loop structures. The Setxspcar3 mutant mice exhibit male infertility and female subfertility. Histology of the Setxspcar3 mutant testes revealed the absence of spermatids and mature spermatozoa in the seminiferous tubules. Cytological analysis of chromosome preparations of the Setxspcar3 mutant spermatocytes revealed normal synapsis, but aberrant DNA damage in the autosomes, defective formation of the sex body, and arrest of meiosis in mid-prophase. Additionally, Setxspcar3 testicular cells exhibit abnormal accumulation of R-loops. Transient expression assays identified regions of the senataxin protein required for sub-nuclear localization. Together, these results not only confirm that senataxin is required for normal meiosis and spermatogenesis but also provide a new resource for the determination of its role in maintaining R-loop formation and genome integrity.

The role of the transsulfuration pathway in spermatogenesis of vitamin D deficient mice

Vitamin D deficiency is a global health problem and has been linked to defective spermatogenesis and male infertility. In this study, we aimed to investigate the main enzymes involved in the transsulfuration pathway of 1-carbon metabolism, and spermatogenesis function. Therefore, sixteen male C57 mice were addressed to a control (standard diet) or vitamin D deficient (VDD) diet for 14 weeks. The results show that compared to the standard diet, VDD increased final body weight and reduced sperm quality, caused damage to the testicular structure, and decreased the serum levels of testosterone. In addition, serum concentrations of homocysteine, vitamin B12, and sperm oxidative stress markers increased. In testicular tissues, the CBS and CSE protein levels were down-regulated whereas HO-1 was up-regulated at both mRNA and protein expression levels. Within a mice deprivation model, VDD deeply suppressed testosterone and impaired spermatogenesis with oxidative stress-mediated mechanisms. The effects of the deprivation appeared to be at least in part independent of genomic and receptor-mediated vitamin D actions and suggest a specific impairment of the alternative transsulfuration pathway.

Small RNAs, spermatogenesis, and male infertility: a decade of retrospect

Small non-coding RNAs (sncRNAs), being the top regulators of gene expression, have been thoroughly studied in various biological systems, including the testis. Research over the last decade has generated significant evidence in support of the crucial roles of sncRNAs in male reproduction, particularly in the maintenance of primordial germ cells, meiosis, spermiogenesis, sperm fertility, and early post-fertilization development. The most commonly studied small RNAs in spermatogenesis are microRNAs (miRNAs), PIWI-interacting RNA (piRNA), small interfering RNA (siRNA), and transfer RNA-derived small RNAs (ts-RNAs). Small non-coding RNAs are crucial in regulating the dynamic, spatial, and temporal gene expression profiles in developing germ cells. A number of small RNAs, particularly miRNAs and tsRNAs, are loaded on spermatozoa during their epididymal maturation. With regard to their roles in fertility, miRNAs have been studied most often, followed by piRNAs and tsRNAs. Dysregulation of more than 100 miRNAs has been shown to correlate with infertility. piRNA and tsRNA dysregulations in infertility have been studied in only 3-5 studies. Sperm-borne small RNAs hold great potential to act as biomarkers of sperm quality and fertility. In this article, we review the role of small RNAs in spermatogenesis, their association with infertility, and their potential as biomarkers of sperm quality and fertility.

The Role of Circular RNAs in Male Infertility and Reproductive Cancers: A Narrative Review

Infertility is a global health problem affecting about 15% of all couples, of which 50% are due to male infertility. Although the etiology of infertility is known in most infertile men, idiopathic male infertility remains a challenge. Therefore, there is a need for novel diagnostic methods to detect the underlying mechanisms and develop appropriate therapies. Recent studies have focused on the role of non-coding RNAs (ncRNAs) in male infertility. Circular RNAs (CircRNAs), a type of ncRNAs, are found to play a key role in the development of some pathological conditions, including cardiovascular diseases, diabetes, cancers, autoimmune diseases, etc. Several studies have reported the presence of CircRNAs and their target genes in the human reproductive system. In addition, their expression in testicular tissues, sperm cells, and seminal fluid has been identified. Abnormal expression of CircRNAs has been associated with azoospermia and asthenozoospermia in infertile men. The present narrative review provides a brief description of the role of CircRNAs in spermatogenic cells, male infertility, and reproductive cancers. In addition, some CircRNAs have been identified as potential biomarkers for disease detection and treatment.

Cell-type-specific determination of reactive oxygen species by flow cytometry

BACKGROUND

Seminal leukocyte-generated reactive oxygen species may have a significant impact on sperm intracellular reactive oxygen species levels, therefore contributing to oxidative damage and consequent functional impairment of spermatozoa. This relationship may be utilized for male urogenital inflammation-driven oxidative stress diagnostics.

OBJECTIVE

To obtain seminal cell-specific, reactive oxygen species-related fluorescence intensity cut-off values to differentiate leukocytospermic samples displaying reactive oxygen species overproduction (oxidative burst) from normozoospermic seminal samples.

MATERIAL AND METHODS

Ejaculates gained by masturbation were obtained from patients in the framework of andrology consultations. The results published in this paper were generated from samples for which the attending physician requested spermatograms and seminal reactive oxygen species laboratory tests. Routine seminal analyses were performed according to World Health Organization guidelines. Samples were divided into normozoospermic "non-inflamed," and leukocytospermic groups. The semen was stained by 2',7'-dichlorodihydrofluorescein diacetate and the reactive oxygen species-related fluorescence signal and the percentage of reactive oxygen species-positive spermatozoa within the living population were quantified by flow cytometry.

RESULTS

Reactive oxygen species-related mean fluorescence intensity was higher in both spermatozoa and leukocytes from leukocytospermic samples than in those from normozoospermic samples. Mean fluorescence intensity in spermatozoa was positively and linearly correlated with mean fluorescence intensity measured in leukocytes in both groups.

DISCUSSION

The capacity of spermatozoa to generate reactive oxygen species is at least three log lower than that of granulocytes. The question is whether the reactive oxygen species-producing machinery of spermatozoa is capable of causing autologous oxidative stress or whether leukocytes are the predominant source of seminal oxidative stress. Based on our observations, the reactive oxygen species production of leukocytes may have a significant impact on the overall reactive oxygen species levels measured in spermatozoa.

CONCLUSION

Reactive oxygen species-overproducing leukocytospermic and normozoospermic seminal samples can reliably be differentiated based on reactive oxygen species mean fluorescence intensity measurement.

A single-cell transcriptomic landscape of mouse testicular aging

INTRODUCTION

Advanced paternal age of reproduction is an increasing trend, especially in developed countries and areas. This trend results in elevated risks of adverse reproductive outcomes such as reduced fertility rates, increased pregnancy loss, and poor childhood health. Yet, a systematic profiling of aging-associated molecular and cellular alterations in testicular tissue is still missing.

OBJECTIVES

We aimed to dissect aging-associated molecular characteristics in testes of mice.

METHODS

Single-cell transcriptomic sequencing and analysis were conducted in testes of young (2 months old) and old mice (24 months old). Immunofluorescences and immunochemistry were used to characterize aging-associated phenotypes and verify single cell sequence results.

RESULTS

Here, we constructed the first single-cell transcriptomic atlases of testes of young and old mice. In-depth dissection of aging-dependent transcriptional alterations in specific cell types revealed multiple dysregulated biological processes such as increased 'senescence-associated secretory phenotype' and 'inflammation', which were major aging-associated characteristics. Further analysis of aging-related differentially expressed genes uncovered a disrupted balance of undifferentiated and differentiated spermatogonia stem cells in spermatogonia, indicative of a potential role of spermatogonia stem cells in aging-associated subfertility. Importantly, for the first time, our results identified an increased subtype of aging-specific macrophages, which may contribute to a hostile proinflammatory microenvironment during testicular aging.

CONCLUSION

Taken together, our findings depict the distinct single-cell transcriptional features of the aged mouse testes and provide enormous resources for a comprehensive understanding of the cell-type-specific molecular mechanisms underlying mouse testicular aging, which may shed light on developing novel potential diagnostic biomarkers and therapeutic targets for age-associated male subfertility.

Dose-Dependent Protective Effect of Hygrophila auriculata Seeds on Cyproterone Acetate-Induced Testicular Dysfunction

Infertility affects 15% of global population. This study was designed to search out the most effective dose of chloroform fraction of hydro-ethanolic extract of Hygrophila auriculata seed to ameliorate cyproterone acetate (CPA)-treated male subfertility. The rats were made subfertile by CPA at the dose of 2.5 mg/100gm body weight for 45 days. The male subfertility represented by low sperm concentration, less motile, less viable, and less hypo osmotic tail swelled spermatozoa in CPA-treated group. Serum LH, FSH, and testosterone levels were significantly decreased in CPA-treated group in respect to control. Androgenic key enzyme Δ5,3β-HSD, 17β-HSD activities and gene expression pattern were also decreased significantly in respect to control. These antispermatogenic and antiandrogenic activities of CPA were significantly recovered after the treatment of Hygrophila auriculata at the dose of 2.5 mg, 5mg, and 10 mg/100gm body weight. CPA also generate oxidative free radical that indicated by altered catalase, superoxide dismutase, and peroxidase activities and protein expression pattern along with conjugated diene and thiobarbituric acid reactive substance levels in testis. Expression pattern of Bax and Bcl2 genes were deviated from control after CPA treatment. Significant diminution of body weight, organo-somatic indices, and SGOT, SGPT activities were observed in CPA-treated group. All these biomarkers significantly recovered towards control after the treatment of Hygrophila auriculata at different doses. More significant recovery was observed in 5 mg and 10 mg of chloroform fraction-treated group and 5 mg dose, i.e., the minimum therapeutic dose to recover the CPA-induced subfertility.

Age-Related COVID-19 Influence on Male Fertility

The impact of coronavirus on the reproductive health of men attracts the special attention of many researchers. While studies suggest changes in sperm parameters and the possibility of testicular inflammation, further studies are needed to elucidate any potential age-related changes in these findings, which is the purpose of the present study. The semen quality parameters, cytokine concentration, and markers of the pro- and antioxidant system were assessed in 60 men five to seven months after the coronavirus infection and in 77 controls (without a history of coronavirus infection). Additionally, participants were divided into two age groups: less than 35 years and 35 years or older. Notably increased round cell count in ejaculate and reduced sperm hyaluronan binding ability were observed among post-infection patients younger than 35 years. In the same group, a decline in seminal plasma zinc levels and nitrotyrosine in the cell fraction was found. In men over 35 years of age, Coronavirus Disease 2019 (COVID-19) led to increased sperm DNA fragmentation, a decrease in the total antioxidant capacity, and an elevation in the levels of interleukin-1β and interleukin-10. The concentration of interleukin-1β decreased over time following recovery in all affected patients. The data obtained suggest the potential adverse impact of the coronavirus infection on male reproductive health; however, these effects appear to be age-dependent.

X-linked RBBP7 mutation causes maturation arrest and testicular tumors

Maturation arrest (MA) is a subtype of non-obstructive azoospermia, and male infertility is a known risk factor for testicular tumors. However, the genetic basis for many affected individuals remains unknown. Here, we identified a deleterious hemizygous variant of X-linked retinoblastoma-binding protein 7 (RBBP7) as a potential key cause of MA, which was also found to be associated with the development of Leydig cell tumors. This mutation resulted in premature protein translation termination, affecting the sixth WD40 domain of the RBBP7 and the interaction of the mutated RBBP7 with histone H4. Decreased BRCA1 and increased γH2AX were observed in the proband. In mouse spermatogonial and pachytene spermatocyte-derived cells, deprivation of rbbp7 led to cell cycle arrest and apoptosis. In Drosophila, knockdown of RBBP7/Caf1-55 in germ cells resulted in complete absence of germ cells and reduced testis size, whereas knockdown of RBBP7/Caf1-55 in cyst cells resulted in hyperproliferative testicular cells. Interestingly, male infertility caused by Caf1-55 deficiency was rescued by ectopic expression of wild-type human RBBP7 but not mutant variants, suggesting the importance of RBBP7 in spermatogenesis. Our study provides insights into the mechanisms underlying the co-occurrence of MA and testicular tumors and may pave the way for innovative genetic diagnostics of these 2 diseases.

Rhox8 homeobox gene ablation leads to rete testis abnormality and male subfertility in mice†

The reproductive homeobox X-linked (Rhox) genes encode transcription factors that are expressed selectively in reproductive tissues including the testis, epididymis, ovary, and placenta. While many Rhox genes are expressed in germ cells in the mouse testis, only Rhox8 is expressed exclusively in the Sertoli cells during embryonic and postnatal development, suggesting a possible role of Rhox8 in embryonic gonad development. Previously, Sertoli cell-specific knockdown of RHOX8 resulted in male subfertility due to germ cell defects. However, this knockdown model was limited in examining the functions of Rhox8 as RHOX8 knockdown occurred only postnatally, and there was still residual RHOX8 in the testis. In this study, we generated new Rhox8 knockout (KO) mice using the CRISPR/Cas9 system. Sex determination and fetal testis development were apparently normal in mutant mice. Fertility analysis showed a low fecundity in Rhox8 KO adult males, with disrupted spermatogenic cycles, increased germ cell apoptosis, and reduced sperm count and motility. Interestingly, Rhox8 KO testes showed an increase in testis size with dilated seminiferous tubules and rete testis, which might be affected by efferent duct (ED) Rhox8 ablation dysregulating the expression of metabolism and transport genes in the EDs. Taken together, the data presented in this study suggest that Rhox8 in the Sertoli cells is not essential for sex determination and embryonic testis differentiation but has an important role in complete spermatogenesis and optimal male fertility.

Deficiency in AK9 causes asthenozoospermia and male infertility by destabilising sperm nucleotide homeostasis

BACKGROUND

Asthenozoospermia is the primary cause of male infertility; however, its genetic aetiology remains poorly understood. Adenylate kinase 9 (AK9) is highly expressed in the testes of humans and mice and encodes a type of adenosine kinase that is functionally involved in cellular nucleotide homeostasis and energy metabolism. We aimed to assess whether AK9 is involved in asthenozoospermia.

METHODS

One-hundred-and-sixty-five Chinese men with idiopathic asthenozoospermia were recruited. Whole-exome sequencing (WES) and Sanger sequencing were performed for genetic analyses. Papanicolaou staining, Haematoxylin and eosin staining, scanning electron microscopy, and transmission electron microscopy were used to observe the sperm morphology and structure. Ak9-knockout mice were generated using CRISPR-Cas9. Sperm adenosine was detected by liquid chromatography-mass spectrometry. Targeted sperm metabolomics was performed. Intracytoplasmic sperm injection (ICSI) was used to treat patients.

FINDINGS

We identified five patients harbouring bi-allelic AK9 mutations. Spermatozoa from men harbouring bi-allelic AK9 mutations have a decreased ability to sustain nucleotide homeostasis. Moreover, bi-allelic AK9 mutations inhibit glycolysis in sperm. Ak9-knockout male mice also presented similar phenotypes of asthenozoospermia. Interestingly, ICSI was effective in bi-allelic AK9 mutant patients in achieving good pregnancy outcomes.

INTERPRETATION

Defects in AK9 induce asthenozoospermia with defects in nucleotide homeostasis and energy metabolism. This sterile phenotype could be rescued by ICSI.

FUNDING

The National Natural Science Foundation of China (82071697), Medical Innovation Project of Fujian Province (2020-CXB-051), open project of the NHC Key Laboratory of Male Reproduction and Genetics in Guangzhou (KF202004), Medical Research Foundation of Guangdong Province (A2021269), Guangdong Provincial Reproductive Science Institute Innovation Team grants (C-03), and Outstanding Young Talents Program of Capital Medical University (B2205).

Current Progress in Stem Cell Therapy for Male Infertility

Infertility has become one of the most common issues worldwide, which has negatively affected society and infertile couples. Meanwhile, male infertility is responsible for about 50% of infertility. Accordingly, a great number of researchers have focused on its treatment during the last few years; however, current therapies such as assisted reproductive technology (ART) are not effective enough in treating male infertility. Because of their self-renewal and differentiation capabilities and unlimited sources, stem cells have recently raised great hope in the treatment of reproductive system disorders. Stem cells are undifferentiated cells that can induce different numbers of specific cells, such as male and female gametes, demonstrating their potential application in the treatment of infertility. The present review aimed at identifying the causes and potential factors that influence male fertility. Besides, we highlighted the recent studies that investigated the efficiency of stem cells such as spermatogonial stem cells (SSCs), embryonic stem cells (ESCs), very small embryonic-like stem cells (VSELs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs) in the treatment of various types of male infertility.

The human sperm proteome-Toward a panel for male fertility testing

BACKGROUND

Although male factor accounts for 40%-50% of unintended childlessness, we are far from fully understanding the detailed causes. Usually, affected men cannot even be provided with a molecular diagnosis.

OBJECTIVES

We aimed at a higher resolution of the human sperm proteome for better understanding of the molecular causes of male infertility. We were particularly interested in why reduced sperm count decreases fertility despite many normal-looking spermatozoa and which proteins might be involved.

MATERIAL AND METHODS

Applying mass spectrometry analysis, we qualitatively and quantitatively examined the proteomic profiles of spermatozoa from 76 men differing in fertility. Infertile men had abnormal semen parameters and were involuntarily childless. Fertile subjects exhibited normozoospermia and had fathered children without medical assistance.

RESULTS

We discovered proteins from about 7000 coding genes in the human sperm proteome. These were mainly known for involvements in cellular motility, response to stimuli, adhesion, and reproduction. Numbers of sperm proteins showing at least threefold deviating abundances increased from oligozoospermia (N = 153) and oligoasthenozoospermia (N = 154) to oligoasthenoteratozoospermia (N = 368). Deregulated sperm proteins primarily engaged in flagellar assembly and sperm motility, fertilization, and male gametogenesis. Most of these participated in a larger network of male infertility genes and proteins.

DISCUSSION

We expose 31 sperm proteins displaying deviant abundances under infertility, which already were known before to have fertility relevance, including ACTL9, CCIN, CFAP47, CFAP65, CFAP251 (WDR66), DNAH1, and SPEM1. We propose 18 additional sperm proteins with at least eightfold differential abundance for further testing of their diagnostic potential, such as C2orf16, CYLC1, SPATA31E1, SPATA31D1, SPATA48, EFHB (CFAP21), and FAM161A.

CONCLUSION

Our results shed light on the molecular background of the dysfunctionality of the fewer spermatozoa produced in oligozoospermia and syndromes including it. The male infertility network presented may prove useful in further elucidating the molecular mechanism of male infertility.

Puerarin improves busulfan-induced disruption of spermatogenesis by inhibiting MAPK pathways

Male infertility is a global concern, with a noticeable increase in the decline of spermatogenesis and sperm quality. However, there are limited clinically effective treatments available. This study aimed to investigate the potential effectiveness of puerarin in treating male infertility, which leads to gonadal changes. The results obtained from various analyses such as CASA, immunofluorescence, DIFF-Quick, hematoxylin and eosin (H&E), and periodic acid-Schiff (PAS) staining demonstrated that puerarin supplementation significantly alleviated the busulfan-induced reduction in spermatogenesis and sperm quality in both young and adult mice. Furthermore, puerarin exhibited a marked improvement in the damage caused by busulfan to the architecture of seminiferous tubules, causal epididymis, blood-testicular barrier (BTB), as well as spermatogonia and Sertoli cells. Similarly, puerarin significantly reduced the levels of total antioxidant capacity (T-AOC), malondialdehyde (MDA), and caspase-3 in the testes of busulfan-induced mice, as determined by microplate reader analysis. Additionally, RNA-seq data, RT-qPCR, and western blotting revealed that puerarin restored the abnormal gene expressions induced by busulfan to nearly healthy levels. Notably, puerarin significantly reversed the impact of busulfan on the expression of marker genes involved in spermatogenesis and oxidative stress. Moreover, puerarin suppressed the phosphorylation of p38, ERK1/2, and JNK in the testes, as observed through testicular analysis. Consequently, this study concludes that puerarin may serve as a potential alternative for treating busulfan-induced damage to male fertility by inactivating the testicular MAPK pathways. These findings may pave the way for the use of puerarin in addressing chemotherapy- or other factors-induced male infertility in humans.