Characteristics of testis-specific phosphoglycerate kinase 2 and its association with human sperm quality

Gut-Gonad Perturbations in Type-1 Diabetes Mellitus: Role of Dysbiosis, Oxidative Stress, Inflammation and Energy-Dysbalance

Type 1 diabetes mellitus is a major metabolic disorder that affects people of all age groups throughout the world. It is responsible for the alterations in male gonadal physiology in experimental models as well as in clinical cases. On the other side, diabetes mellitus has also been associated with perturbations in the gut physiology and microbiota dysbiosis. The accumulating evidence suggests a link between the gut and gonad as evident from the i) experimental data providing insights into type 1 diabetes mellitus induced gut perturbations, ii) link of gut physiology with alterations of testicular health, iii) role of gut microbiota in androgen metabolism in the intestine, and iv) epidemiological evidence linking type 1 diabetes mellitus with inflammatory bowel disease and male infertility. Considering all the pieces of evidence, it is summarized that gut dysbiosis, oxidative stress, inflammation and energy dys-balance are the prime factors involved in the gonadal damage under type 1 diabetes mellitus, in which the gut contributes significantly. Identification of novel biomarkers and intervention of suitable agents targeting these prime factors may be a step forward to restore the gonadal damage in diabetic conditions.

The Germ Cell-Specific Markers ZPBP2 and PGK2 in Testicular Biopsies Can Predict the Presence as well as the Quality of Sperm in Non-obstructive Azoospermia Patients

To assess the role of three testis-specific genes including ZPBP2, PGK2, and ACRV1 in the prediction of sperm retrieval result and quality of retrieved sperm by microdissection testicular sperm extraction (micro-TESE) in non-obstructive azoospermia (NOA) patients. This was a case-control study including 57 testicular samples of NOA patients including 32 patients with successful sperm retrieval (NOA+) and 25 patients with failed sperm retrieval (NOA-), and 9 samples of men with normal spermatogenesis in the testes as the positive control (OA). We investigated the expression of candidate genes by RT-qPCR and germ cell population patterns by DNA flow cytometry in testicular biopsy samples. The association between PGK2 expressions with the quality of retrieved spermatozoa was also evaluated. The RT-qPCR data revealed a significantly higher expression of ZPBP2 and PGK2 in the NOA+ in comparison to NOA- group (P = 0.002, and P = 0.002, respectively). Flow cytometry results revealed that the haploid cell percentage was significantly higher in NOA+ vs. NOA- group (P = 0.0001). In samples with a higher percentage of haploid cells, expression levels of ZPBP2 and PGK2 were higher (P = 0.001). The PGK2 expression was significantly associated with retrieved sperm quality (P = 0.01). Our results contribute to the search for the biomarkers for predicting the presence of testicular sperm and would be useful to avoid unnecessary multiple micro-TESE. Overall, the expression pattern of the ZPBP2 and PGK2 may be useful in predicting sperm recovery success and quality of retrieved sperm in NOA patients.

Identification of abnormal protein expressions associated with mouse spermatogenesis induced by cyclophosphamide

Cyclophosphamide (CP) is a clinical anticancer drug that can cause male reproductive abnormalities, but the underlying mechanisms for this remain unknown. The present study aimed to explore the potential toxicity induced by CP in spermatogenesis events of germ cell proliferation, meiosis, and blood-testis barrier integrity at the molecular level. CP-treated mice showed significantly reduced serum testosterone levels, sperm motility and concentration. The results of immunohistochemistry and Western blot showed that CP reduced the proliferation of germ cells (PCNA, PLZF) and increased germ cell apoptosis (Bax and TUNEL-positive cells) in CP-treated mice testes. The expression of meiotic related proteins (SYCP3, REC8, MLH1) decreased significantly in the fourth week after administration, and the expression of blood-testis barrier related proteins (β-catenin, ZO-1) and sperm quality-associated proteins (PGK2, HSPA4) decreased significantly in the first week after administration. CP leads to the apoptosis of male germ cells, inhibits the proliferation of germ cells, and affects meiosis and the blood-testis barrier, resulting in the decline of sperm quality. This study provides information to further the study of molecular mechanism and protective strategy of CP influence.

Phosphoproteomics and Bioinformatics Analyses Reveal Key Roles of GSK-3 and AKAP4 in Mouse Sperm Capacitation

Protein phosphorylation can induce signal transduction to change sperm motility patterns during sperm capacitation. However, changes in the phosphorylation of sperm proteins in mice are still incompletely understood. Here, capacitation-related phosphorylation in mouse sperms were firstly investigated by label-free quantitative (LFQ) phosphoproteomics coupled with bioinformatics analysis using ingenuity pathway analysis (IPA) methods such as canonical pathway, upstream regulator, and network analysis. Among 1632 phosphopeptides identified at serine, threonine, and tyrosine residues, 1050 novel phosphosites, corresponding to 402 proteins, were reported. Gene heatmaps for IPA canonical pathways showed a novel role for GSK-3 in GP6 signaling pathways associated with capacitation for 60 min. At the same time, the reduction of the abundant isoform-specific GSK-3α expression was shown by western blot (WB) while the LFQ pY of this isoform slightly decreased and then increased. The combined results from WB and LFQ methods explain the less inhibitory phosphorylation of GSK-3α during capacitation and also support the predicted increases in its activity. In addition, pAKAP4 increased at the Y156 site but decreased at the Y811 site in a capacitated state, even though IPA network analysis and WB analysis for overall pAKAP revealed upregulated trends. The potential roles of GSK-3 and AKAP4 in fertility are discussed.

Amalgamated cross-species transcriptomes reveal organ-specific propensity in gene expression evolution

The origins of multicellular physiology are tied to evolution of gene expression. Genes can shift expression as organisms evolve, but how ancestral expression influences altered descendant expression is not well understood. To examine this, we amalgamate 1,903 RNA-seq datasets from 182 research projects, including 6 organs in 21 vertebrate species. Quality control eliminates project-specific biases, and expression shifts are reconstructed using gene-family-wise phylogenetic Ornstein-Uhlenbeck models. Expression shifts following gene duplication result in more drastic changes in expression properties than shifts without gene duplication. The expression properties are tightly coupled with protein evolutionary rate, depending on whether and how gene duplication occurred. Fluxes in expression patterns among organs are nonrandom, forming modular connections that are reshaped by gene duplication. Thus, if expression shifts, ancestral expression in some organs induces a strong propensity for expression in particular organs in descendants. Regardless of whether the shifts are adaptive or not, this supports a major role for what might be termed preadaptive pathways of gene expression evolution.

Proteomic Changes in Human Sperm During Sequential in vitro Capacitation and Acrosome Reaction

The male gamete is not completely mature after ejaculation and requires further events in the female genital tract to acquire fertilizing ability, including the processes of capacitation and acrosome reaction. In order to shed light on protein changes experienced by the sperm cell in preparation for fertilization, a comprehensive quantitative proteomic profiling based on isotopic peptide labeling and liquid chromatography followed by tandem mass spectrometry was performed on spermatozoa from three donors of proven fertility under three sequential conditions: purification with density gradient centrifugation, incubation with capacitation medium, and induction of acrosome reaction by exposure to the calcium ionophore A23187. After applying strict selection criteria for peptide quantification and for statistical analyses, 36 proteins with significant changes in their relative abundance within sperm protein extracts were detected. Moreover, the presence of peptide residues potentially harboring sites for post-translational modification was revealed, suggesting that protein modification may be an important mechanism in sperm maturation. In this regard, increased levels of proteins mainly involved in motility and signaling, both regulated by protein modifiers, were detected in sperm lysates following incubation with capacitation medium. In contrast, less abundant proteins in acrosome-reacted cell lysates did not contain potentially modifiable residues, suggesting the possibility that all those proteins might be relocated or released during the process. Protein-protein interaction analysis revealed a subset of proteins potentially involved in sperm maturation, including the proteins Erlin-2 (ERLIN2), Gamma-glutamyl hydrolase (GGH) and Transmembrane emp24 domain-containing protein 10 (TMED10). These results contribute to the current knowledge of the molecular basis of human fertilization. It should now be possible to further validate the potential role of the detected altered proteins as modulators of male infertility.

Transcriptomic analysis of reproductive damage in the epididymis of male Kunming mice induced by chronic infection of Toxoplasma gondii PRU strain

BACKGROUND

Some researchers have reported that Toxoplasma gondii can cause serious reproductive impairment in male animals. Specifically, T. gondii destroy the quality of sperm in the epididymis, which affects their sexual ability. However, among such studies, none have investigated the male reproductive transcriptome. Therefore, to investigate the relationship between T. gondii and sperm maturation, we infected mice with T. gondii prugniaud (PRU) strain and performed transcriptome sequencing of the epididymis.

RESULTS

Compared with the control group, 431 upregulated and 229 downregulated differentially expressed genes (DEGs) were found (P-value < 0.05, false discovery rate (FDR) < 0.05 and |log2 (fold change)| ≥ 1). According to results of a bioinformatics analysis, Gene Ontology (GO) function is divided into three categories: cellular component, molecular function and biological process. Upon performing GO analysis, we found that some DEGs correlated with an integral part of membrane, protein complex, cell surface, ATP binding, immune system process, signal transduction and metabolic process which are responsible for the epididymal injury. DEGs were mapped to 101 unique KEGG pathways. Pathways such as cytokine-cytokine receptor interaction, glycolysis/gluconeogenesis and apoptosis are closely related to sperm quality. Moreover, Tnfsf10 and spata18 can damage the mitochondria in sperm, which decreases sperm motility and morphology.

CONCLUSIONS

We sequenced the reproductive system of male mice chronically infected with T. gondii, which provides a new direction for research into male sterility caused by Toxoplasma infection. This work provides valuable information and a comprehensive database for future studies of the interaction between T. gondii infection and the male reproductive system.

Integrated Analyses of Phenotype and Quantitative Proteome of CMTM4 Deficient Mice Reveal Its Association with Male Fertility

The chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family (CMTM) is a gene family that has been implicated in male reproduction. CMTM4 is an evolutionarily conserved member that is highly expressed in the testis. However, its function in male fertility remains unknown. Here, we demonstrate that CMTM4 is associated with spermatogenesis and sperm quality. Using Western blotting and immunohistochemical analyses, we found CMTM4 expression to be decreased in poor-quality human spermatozoa, old human testes, and testicular biopsies with nonobstructive azoospermia. Using CRISPR-Cas9 technology, we knocked out the Cmtm4 gene in mice. These Cmtm4 knockout (KO) mice showed reduced testicular daily sperm production, lower epididymal sperm motility and increased proportion of abnormally backward-curved sperm heads and bent sperm midpieces. These mice also had an evident sub-fertile phenotype, characterized by low pregnancy rates on prolonged breeding with wild type female mice, reduced in vitro fertilization efficiency and a reduced percentage of acrosome reactions. We then performed quantitative proteomic analysis of the testes, where we identified 139 proteins to be downregulated in Cmtm4-KO mice, 100 (71.9%) of which were related to sperm motility and acrosome reaction. The same proteomic analysis was performed on sperm, where we identified 3588 proteins with 409 being differentially regulated in Cmtm4-KO mice. Our enrichment analysis showed that upregulated proteins were enriched with nucleosomal DNA binding functions and the downregulated proteins were enriched with actin binding functions. These findings elucidate the roles of CMTM4 in male fertility and demonstrates its potential as a promising molecular candidate for sperm quality assessment and the diagnosis or treatment of male infertility.

Aberrant expression of sperm‑specific glycolytic enzymes are associated with poor sperm quality

The energy required for normal sperm function is mainly generated by glycolysis and oxidative phosphorylation. Testis‑specific glycolytic enzymes are expressed in germ cells and present in mature spermatozoa. The objective of the present study was to investigate the association between aberrant expression of glycolytic enzymes and human sperm quality. In silico analysis of glyceraldehyde‑3‑phosphate dehydrogenase, testis‑specific (GAPDHS), phosphoglycerate kinase 2 (PGK2) and lactate dehydrogenase (LDHC) identified that they were exclusively expressed in post‑meiotic germ cells and this was validated in human testes using immunohistochemistry. Compared with the testes of young adults, markedly lower expression levels of these glycolytic enzymes were observed in the testes of elderly adults. Similarly, low levels were observed in immature and asthenozoospermic spermatozoa. The expression levels of GAPDHS, PGK2 and LDHC in the spermatozoa were closely correlated with progressive sperm motility. The results indicated that the expression of GAPDHS, PGK2 and LDHC in sperm may be associated with sperm quality, and there may be a similar molecular mechanism underlying sperm quality in immature and asthenozoospermic spermatozoa. This study reveals a close association of glycolytic enzymes with sperm quality. The data may greatly contribute to the molecular evaluation of sperm quality and the diagnosis and treatment of asthenozoospermia.

Detection of sperm-reactive antibodies in wild sika deer and identification of the sperm antigens

Antisperm antibodies potentially inhibit sperm functions causing the sterility in humans and experimentally treated animals. However, there is no information about antisperm antibodies emerging spontaneously in wildlife. In this study, we searched for the sperm-reactive antibodies, spontaneously produced in wild sika deer (Cervus nippon), and identified the sperm antigens. We collected 529 fecal masses of sika deer in Japanese cities, from which we extracted the mucosal antibodies to test them for reactivities to deer sperm proteins by ELISA. Two of the extracts contained IgAs that were highly reactive to the sperm proteins. The molecular weights of the active IgAs, partially purified by DEAE-sephadex A-50, were estimated at more than 100 kDa, suggesting that the IgAs evaded drastic digestion in the gastrointestinal tract. Two-dimensional electrophoresis and immunoblotting detected three major antigens, and the following LC-MS/MS analysis identified them as alpha-enolase, phosphoglycerate kinase 2 and acrosin-binding protein. The antibodies were cross-reactive to a recombinant human acrosin-binding protein. To our knowledge, this is the first research to find that the sperm-reactive antibodies are produced spontaneously in wildlife and they recognize a common antigen found in humans.

Differential expression of peroxiredoxin 3 in laryngeal squamous cell carcinoma

Peroxiredoxin (PRDX) proteins are involved in carcinogenesis. PRDX3, which is predominantly localized in mitochondria and up-regulated in several human cancers, seems to confer increased treatment resistance and aggressive phenotypes. This study examined the expression profile of PRDX3 and its possible clinical value in laryngeal squamous cell carcinoma (LSCC). The expression of PRDX3 in LSCC samples was confirmed by Western blotting and further analyzed by immunohistochemistry in LSCC samples of different clinical pathological stages. The results showed that up-regulated expression of PRDX3 was observed in LSCC and associated with poor differentiation (P < 0.01), primary tumor location, N category and tumor stage (P < 0.05). Knockdown of PRDX3 in the Hep-2 laryngeal carcinoma epithelial cell line significantly enhanced Hep-2 cells’ apoptosis and inhibited their proliferation and migration. Taken together, our results suggest that PRDX3 has substantial clinical impact on the progression of LSCC and shed new light on the role of PRDX3 in treatment resistance and aggressive phenotypes in LSCC.

Association between RNA-binding protein Ptbp2 and germ cell injury in an experimentally-induced unilateral cryptorchidism murine model

RNA binding protein polypyrimidine tract binding protein 2 (Ptbp2) as a key alternative splicing regulator for male germ cell development is well established. However, its expression levels and role in cryptorchidism testes tissues has not been explored. Additionally, the molecular mechanism of heat stress impacts the correct proliferation and differentiation of germ cells is unclear. To investigate whether changes in Ptbp2 expression are correlated with heat stress-induced germ cell injury in testicular tissue, we used a murine model of intraperitoneal cryptorchidism with surgical operation. Here we present compelling evidence that germ cells are severely damaged in mice with unilateral cryptorchidism, with non-obstructive azoospermia. And the Ptbp2 and Pgk2 mRNA levels were significantly decreased in parallel, leading us to conclude that the negative correlation between Ptbp2 levels and germ cell injury in unilateral cryptorchidism murine model. We hypothesize that Ptbp2 is susceptible to heat stress and its disruption has resulted in stability decline of germ cell transcripts Pgk2 mRNA, which consequently lead to germ cell injury in cryptorchidism testes. Thus, we confirm that Ptbp2 is an essential factor in heat stress-induced sperm cell injury and non-obstructive azoospermia.

Molecular effect of human umbilical cord blood CD34-positive and CD34-negative stem cells and their conjugate in azoospermic mice

Currently, azoospermia is one of the most common diseases of male infertility. Stem cell research is the new hope for novel therapy with a higher degree of safety and lower cost. This study aimed to investigate the effect of umbilical cord blood-derived stem cells (" and mesenchymal "UCB-MSCs") and mono-cell layer implanted into the induced azoospermic mice testis. Stem cells were isolated from umbilical cord blood and CD34+ve cells were separated from negative one by Mini MACs column. At 5th week after single injection of busulfan, stained mesenchymal (CD34-ve), hematopoietic stem cells (CD34+ve) and their conjugate (mono-cell layer) were injected locally into testis. At the end of the study, MSCs group showed that mRNA levels of genes related to meiosis (Vasa, SCP3, and PgK2) were increased with significant decrease of FSH and LH levels, compared to control group. Histologically, most of the tubules restored normal architecture. In contrast, HSCs and mono-cell layer groups showed statically insignificant change of FSH, LH, and gene expression, compared to control group. Histologically, distorted seminiferous tubules, with reduction in sperm content, and interstitial mononuclear cellular infiltration were seen. There was significant increase in the optical density of PCNA immune reaction in MSCs group than azoospermia, HSCs, and mono-cell layer, while there was non-significant difference between MSCs and control group. The present study suggested that injection of MSCs into chemotherapeutic-induced azoospermia in mice improved testicular failure; histologically and functionally, by restoration of spermatogenic gene expression while HSC and mono-cell layer showed no effect on spermatogenesis added to that mono-cell layer may induce testicular tissue damage.