Multiomics analysis of male infertility

Long-read single-cell sequencing reveals the transcriptional landscape of spermatogenesis in obstructive azoospermia and Sertoli cell-only patients

BACKGROUND

High-throughput single-cell RNA sequencing (scRNA-seq) is widely used in spermatogenesis. However, it only reveals short reads in germ and somatic cells, limiting the discovery of novel transcripts and genes.

AIM

This study shows the long-read transcriptional landscape of spermatogenesis in obstructive azoospermia (OA) and Sertoli cell-only patients.

DESIGN

Single cells were isolated from testicular biopsies of OA and non-obstructive azoospermia (NOA) patients. Cell culture was identified by comparing PacBio long-read single-cell sequencing (OA n = 3, NOA n = 3) with short-read scRNA-seq (OA n = 6, NOA n = 6). Ten germ cell types and eight somatic cell types were classified based on known markers.

METHODS

PacBio long-read single-cell sequencing, short-read scRNA-seq, polymerase chain reaction.

RESULTS

A total of 130 426 long-read transcripts (100 517 novel transcripts and 29 909 known transcripts) and 49 508 long-read transcripts (26 002 novel transcripts and 23 506 known transcripts) have been detected in OA and NOA patients, respectively. Moreover, 36 373 and 1642 new genes are identified in OA and NOA patients, respectively. Importantly, specific expressions of long-read transcripts were detected in germ and stomatic cells during normal spermatogenesis.

CONCLUSION

We have identified total full-length transcripts in OA and NOA, and new genes were found. Furthermore, specific expressed full-length transcripts were detected, and the genomic structure of transcripts was mapped in different cell types. These findings may provide valuable information on human spermatogenesis and the treatment of male infertility.

A critical review of the recent concept of regulatory performance of DNA Methylations, and DNA methyltransferase enzymes alongside the induction of immune microenvironment elements in recurrent pregnancy loss

Recurrent pregnancy Loss (RPL)is a frequent and upsetting condition. Besides the prevalent cause of RPL including chromosomal defects in the embryo,the effect of translational elements like alterations of epigenetics are of great importance. The emergence of epigenetics has offered a fresh outlook on the causes and treatment of RPL by focusing on the examination of DNA methylation. RPL may arise as a result of aberrant DNA methylation of imprinted genes, placenta-specific genes, immune-related genes, and sperm DNA, which may have a direct or indirect impact on embryo implantation, growth, and development. Moreover, the distinct immunological tolerogenic milieu established at the interface between the mother and fetus plays a crucial role in sustaining pregnancy. Given this, there has been a great deal of interest in the regulation of DNA methylation and alterations in the cellular components of the maternal-fetal immunological milieu. The research on DNA methylation's role in RPL incidence and the control of the mother-fetal immunological milieu is summed up in this review.

Exploring pathogenesis and biomarkers through establishment of a rat model of male infertility with liver depression and kidney deficiency

OBJECTIVES

To establish a rat model that accurately replicates the clinical characteristics of male infertility (MI) with Liver Depression and Kidney Deficiency (LD & KD) and investigate the pathogenesis.

METHODS

After subjecting the rats to chronic restraint stress (CRS) and adenine treatment, a series of tests were conducted, including ethological assessments, evaluations of reproductive characteristics, measurements of biochemical parameters, histopathological examinations, and analyses of urinary metabolites. Additionally, bioinformatics predictions were performed for comprehensive analysis.

RESULTS

Compared to the control, the model exhibited significant manifestations of MI with LD & KD, including reduced responsiveness, diminished frequency of capturing estrous female rats, and absence of mounting behavior. Additionally, the kidney coefficient increased markedly, while the coefficients of the testis and epididymis decreased significantly. Sperm counts and viabilities decreased notably, accompanied by an increase in sperm abnormalities. Dysregulation of reproductive hormone levels in the serum was observed, accompanied by an upregulation of proinflammatory cytokines expressions in the liver and kidney, as well as exacerbated oxidative stress in the penile corpus cavernosum and testis. The seminiferous tubules in the testis exhibited a loose arrangement, loss of germ cells, and infiltration of inflammatory cells. Furthermore, utilizing urinary metabolomics and bioinformatics analysis, 5 key biomarkers and 2 crucial targets most closely linked to MI were revealed.

CONCLUSION

The study successfully established a clinically relevant animal model of MI with LD & KD. It elucidates the pathogenesis of the condition, identifies key biomarkers and targets, and provides a robust scientific foundation for the prediction, diagnosis, and treatment of MI with LD & KD.

Achilles' heel of male infertility: good LEGO players

In a recent journal article, Chen et al. identified a germ cell-specific cofactor, STYXL1, associated with male fertility function. Deletion of STYXL1 prevents the LEGO player CCT complex from properly folding key microtubule proteins of the sperm flagellum, which affects sperm motility and male fertility function.

Oxidative Stress Biomarkers in Male Infertility: Established Methodologies and Future Perspectives

Male fertility can be affected by oxidative stress (OS), which occurs when an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralize them arises. OS can damage cells and influence sperm production. High levels of lipid peroxidation have been linked to reduced sperm motility and decreased fertilization ability. This literature review discusses the most commonly used biomarkers to measure sperm damage caused by ROS, such as the high level of OS in seminal plasma as an indicator of imbalance in antioxidant activity. The investigated biomarkers include 8-hydroxy-2-deoxyguanosine acid (8-OHdG), a marker of DNA damage caused by ROS, and F2 isoprostanoids (8-isoprostanes) produced by lipid peroxidation. Furthermore, this review focuses on recent methodologies including the NGS polymorphisms and differentially expressed gene (DEG) analysis, as well as the epigenetic mechanisms linked to ROS during spermatogenesis along with new methodologies developed to evaluate OS biomarkers. Finally, this review addresses a valuable insight into the mechanisms of male infertility provided by these advances and how they have led to new treatment possibilities. Overall, the use of biomarkers to evaluate OS in male infertility has supplied innovative diagnostic and therapeutic approaches, enhancing our understanding of male infertility mechanisms.

Therapeutic effect of sodium alginate on bleomycin, etoposide and cisplatin (BEP)-induced reproductive toxicity by inhibiting nitro-oxidative stress, inflammation and apoptosis

Impaired spermatogenesis and male infertility are common consequences of chemotherapy drugs used in patients with testicular cancer. The present study investigated the effects of sodium alginate (NaAL) on testicular toxicity caused by bleomycin, etoposide, and cisplatin (BEP). Rats in group 1 received normal saline, while groups 2 and 3 were treated with 25 and 50 mg/kg of NaAL, respectively. Group 4 was treated with a 21-day cycle of BEP (0.5 mg/kg bleomycin, 5 mg/kg etoposide, and 1 mg/kg cisplatin), and groups 5 and 6 received BEP regimen plus 25 and 50 mg/kg of NaAL, respectively. Then, sperm parameters, testosterone levels, testicular histopathology and stereological parameters, testicular levels of malondialdehyde (MDA), nitric oxide (NO), and total antioxidant capacity (TAC), and the expression of apoptosis-associated genes including Bcl2, Bax, Caspase3, p53, and TNF-α were evaluated. Our findings revealed that NaAL improved sperm parameters, testosterone levels, histopathology, and stereology parameters in BEP-administrated rats. NaAL also improved testis antioxidant status by enhancing TAC and ameliorating MDA and NO. Further, modifications to the expression of Bcl2, Bax, Caspase3, p53, and TNF-α suggested that NaAL alleviated BEP-induced apoptosis and inflammation. Collectively, NaAL protects rats' testes against BEP-evoked toxicity damage through the modulation of nitro-oxidative stress, apoptosis, and inflammation.

Leptin promotes proliferation of human undifferentiated spermatogonia by activating the PI3K/AKT/mTOR pathway

BACKGROUND

Male infertility is a common disease affecting male reproductive health. Leptin is an important hormone that regulates various physiological processes, including reproductive function. However, few experimental studies have been carried out to elucidate the mechanism of leptin's effects on male reproductive function.

OBJECTIVE

The purpose of this study was to investigate the effects of leptin on testicular spermatogenesis and its mechanism, so as to provide potential targets for the treatment of patients with spermatogenic dysfunction.

METHODS

Testicular tissues were collected from eight prostate cancer patients undergoing surgical castration. GPR125-positive spermatogonia were isolated by two consecutive magnetic activated cell sorting (MACS), followed by incubation with conditioned medium. To identify the signaling pathway(s) involved in the effects of leptin, undifferentiated spermatogonia were treated with different concentrations of leptin and antagonists of leptin-related pathways. The proliferative effect of leptin was evaluated by cell counting using a hemocytometer. Expressions of p-AKT, p-ERK, p-STAT, and p-S6K were determined by western blotting analysis.

RESULTS

Leptin promoted the growth of human GPR125-positive spermatogonia in a concentration-dependent manner. The most significant proliferative effect was observed using 100 ng/mL leptin after 6 days of culture. Leptin significantly increased the phosphorylation of STAT3, AKT, and ERK in undifferentiated spermatogonia. Phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 inhibited the leptin-induced activation of AKT, ERK, and downstream S6K. Treatment with the mammalian target of rapamycin (mTOR) inhibitor rapamycin also inhibited S6K phosphorylation. Moreover, both LY294002 and rapamycin were found to inhibit the leptin-induced proliferation of undifferentiated spermatogonia. These results suggested that the leptin-induced proliferation of GPR125-positive spermatogonia was dependent on the PI3K/AKT/mTOR pathway. Further exploration of proliferation and apoptotic markers suggested that leptin may alleviate cell apoptosis by regulating the expression of Bax and FasL.

CONCLUSIONS

A certain concentration of leptin (25∼100 ng/mL) could promote proliferation of undifferentiated spermatogonia, which was mediated by PI3K/AKT/mTOR pathway.

Integrated single cell transcriptome sequencing analysis reveals species-specific genes and molecular pathways for pig spermiogenesis

Mammalian spermatogenesis is a highly complicated and intricately organized process involving spermatogonia propagation (mitosis) and meiotic differentiation into mature sperm cells (spermiogenesis). In pigs, spermatogonia development and the role of somatic cells in spermatogenesis were previously investigated in detail. However, the characterization of key molecules fundamental to pig spermiogenesis remains less explored. Here we compared spermatogenesis between humans and pigs, focusing on spermiogenesis, by integrative testicular single-cell RNA sequencing (scRNA-seq) analysis. Human and pig testicular cells were clustered into 26 different groups, with cell-type-specific markers and signalling pathways. For spermiogenesis, pseudo-time analysis classified the lineage differentiation routes for round, elongated spermatids and spermatozoa. Moreover, markers and molecular pathways specific to each type of spermatids were examined for humans and pigs, respectively. Furthermore, high-dimensional weighted gene co-expression network analysis (hdWGCNA) identified gene modules specific for each type of human and pig spermatids. Hub genes (pig: SNRPD2.1 related to alternative splicing; human: CATSPERZ, Ca[2+] ion channel) potentially involved in spermiogenesis were also revealed. Taken together, our integrative analysis found that human and pig spermiogeneses involve specific genes and molecular pathways and provided resources and insights for further functional investigation on spermatid maturation and male reproductive ability.

CFAP61 knockdown aggravates male infertility by inhibiting testosterone secretion by Leydig cells via the MAPK/COX-2 pathway

This study aimed to elucidate the roles of cilia- and flagella-associated protein 61 (CFAP61) in male infertility and its underlying mechanisms. CFAP61 expression levels in the testicular tissues of male patients with infertility were determined using quantitative real-time polymerase chain reaction, immunohistochemical assay, and western blotting. Moreover, the specific roles of CFAP61 in male infertility were evaluated using cell counting kit-8, 5-ethynyl-2'-deoxyuridine, flow cytometry, and enzyme-linked immunosorbent assays. Here, CFAP61 was expressed at low levels in the testicular tissues of male patients with infertility. Functionally, CFAP61 knockdown reduced the Leydig cell viability and testosterone secretion and enhanced apoptosis. A mechanistic study further revealed that silencing CFAP61 promoted the expression levels of mitogen-activated protein kinase (MAPK)/cyclooxygenase-2 (COX-2) signaling pathway-related proteins (p-extracellular signal-regulated kinase (p-ERK), p-c-Jun N-terminal kinase (p-JNK), p-P38, and COX-2). In conclusion, CFAP61 knockdown facilitated male infertility by suppressing Leydig cell viability and testosterone secretion and enhanced cell apoptosis by activating the MAPK/COX-2 pathway. Our data suggest CFAP61 as a potential therapeutic target for male infertility.

Altered G-Protein Transduction Protein Gene Expression in the Testis of Infertile Patients with Nonobstructive Azoospermia

Recent studies have shown that several members of the G-protein-coupled receptors (GPCR) superfamily play crucial roles in the maintenance of ion-water homeostasis of the sperm and Sertoli cells, development of the germ cells, formation of the blood barrier, and maturation of sperm. The GPCR, guanyl-nucleotide exchange factor, membrane traffic protein, and small GTPase genes were analyzed by microarray and bioinformatics (3513 sperm and Sertoli cell genes). In the microarray analyses of three human cases with different nonobstructive azoospermia sperm, the expression of GOLGA8IP, OR2AT4, PHKA1, A2M, OR56A1, SEMA3G, LRRC17, APP, ARHGAP33, RABGEF1, NPY2R, GHRHR, LTB4R2, GRIK5, OR6K6, NAPG, OR6C65, VPS35, FPR3, and ARL4A was upregulated, while expression of MARS, SIRPG, OGFR, GPR150, LRRK1, and NGEF was downregulated. There was an increase in GBP3, GBP3, TNF, TGFB3, and CLTC expression in the Sertoli cells of three human cases with NOA, whereas expression of PAQR4, RRAGD, RAC2, SERPINB8, IRPB1, MRGPRF, RASA2, SIRPG, RGS2, RAP2A, RAB2B, ARL17, SERINC4, XIAP, DENND4C, ANKRA2, CSTA, STX18, and SNAP23 were downregulated. A combined analysis of Enrich Shiny Gene Ontology (GO), STRING, and Cytoscape was used to predict proteins' molecular interactions and then to recognize master pathways. Functional enrichment analysis showed that the biological process (BP), regulation of protein metabolic process, regulation of small GTPase-mediated signal transduction were significantly expressed in up-/downregulated differentially expressed genes (DEGs) in sperm. In molecular function (MF) experiments of DEGs that were up-/downregulated, it was found that GPCR activity, guanyl ribonucleotide binding, GTPase activity and nucleoside-triphosphatase activity were overexpressed. An analysis of GO enrichment findings of Sertoli cells showed BP and MF to be common DEGs. When these gene mutations have been validated, they can be used to create new GPCR antagonists or agonists that are receptor-selective.

Absence of MerTK disrupts spermatogenesis in an age-dependent manner

Spermatogenesis is a highly specialized cell differentiation process regulated by the testicular microenvironment. During the process of spermatogenesis, phagocytosis performs an essential role in male germ cell development, and its dysfunction in the testis can cause reproduction defects. MerTK, as a critical protein of phagocytosis, facilitates the removal of apoptotic substrates from the retina and ovaries through cooperation with several phagocytosis receptors. However, its role in mammalian spermatogenesis remains undefined. Here, we found that 30-week-old MerTK^-/- male mice developed oligoasthenospermia due to abnormal spermatogenesis. These mice showed damaged seminiferous tubule structure, as well as altered spermatogonia proliferation and differentiation. We also found that Sertoli cells from MerTK^-/- mice had decreased phagocytic activity on apoptotic germ cells in vitro. Moreover, a transcriptomic analysis demonstrated that the pivotal genes involved in spermatid differentiation and development changed expression. These results indicate that MerTK is crucial for spermatogenesis, as it regulates the crosstalk between germ cells and Sertoli cells. This provides us insight into the molecular mechanism of MerTK on spermatogenesis and its implications for the diagnosis and treatment of human male infertility.