Identification of New Epididymal Luminal Fluid Proteins Involved in Sperm Maturation in Infertile Rats Treated by Dutasteride Using iTRAQ

Single-cell and spatial transcriptomic investigation reveals the spatiotemporal specificity of the beta-defensin gene family during mouse sperm maturation

Low sperm motility is a significant contributor to male infertility. beta-defensins have been implicated in host defence and the acquisition of sperm motility; however, the regulatory mechanisms governing their gene expression patterns and functions remain poorly understood. In this study, we performed single-cell RNA and spatial transcriptome sequencing to investigate the cellular composition of testicular and epididymal tissues and examined their gene expression characteristics. In the epididymis, we found that epididymal epithelial cells display a region specificity of gene expression in different epididymal segments, including the beta-defensin family genes. In particular, Defb15, Defb18, Defb20, Defb25 and Defb48 are specific to the caput; Defb22, Defb23 and Defb26 to the corpus; Defb2 and Defb9 to the cauda of the epididymis. To confirm this, we performed mRNA fluorescence in situ hybridisation (FISH) targeting certain exon region of beta-defensin genes, and found some of their expression matched the sequencing results and displayed a close connection with epididimosome marker gene Cd63. In addition, we paid attention to the Sertoli cells and Leydig cells in the testis, along with fibroblasts and smooth muscle cells in the epididymis, by demonstrating their gene expression profile and spatial information. Our study provides a single-cell and spatial landscape for analysing the gene expression characteristics of testicular and epididymal environments and has important implications for the study of spermatogenesis and sperm maturation.

Kisspeptin Receptor on the Sperm Surface Reflects Epididymal Maturation in the Dog

Alongside the well-known central modulatory role, the Kisspeptin system, comprising Kiss1, its cleavage products (Kisspeptins), and Kisspeptin receptor (Kiss1R), was found to regulate gonadal functions in vertebrates; however, its functional role in the male gamete and its localization during maturation have been poorly understood. The present study analyzed Kisspeptin system in dog testis and spermatozoa recovered from different segments of the epididymis, with focus on Kiss1R on sperm surface alongside the maturation during epididymal transit, demonstrated by modification in sperm kinetic, morphology, and protamination. The proteins Kiss1 and Kiss1R were detected in dog testis. The receptor Kiss1R only was detected in total protein extracts from epididymis spermatozoa, whereas dot blot revealed Kiss1 immunoreactivity in the epidydimal fluid. An increase of the Kiss1R protein on sperm surface along the length of the epididymis, with spermatozoa in the tail showing plasma membrane integrity and Kiss1R protein (p < 0.05 vs. epididymis head and body) was observed by flow cytometry and further confirmed by epifluorescence microscopy and Western blot carried on sperm membrane preparations. In parallel, during the transit in the epididymis spermatozoa significantly modified their ability to move and the pattern of motility; a progressive increase in protaminization also occurred. In conclusion, Kisspeptin system was detected in dog testis and spermatozoa. Kiss1R trafficking toward plasma membrane along the length of the epididymis and Kiss1 in epididymal fluid suggested a new functional role of the Kisspeptin system in sperm maturation and storage.

Proteomic Profile of Sperm in Infertile Males Reveals Changes in Metabolic Pathways

The objective of the present study was to investigate the differences in the proteomic profiles of sperm from infertile males with severe oligoasthenoteratozoospermia requiring intracytoplasmic sperm injection (ICSI) and normal control sperm from fertile males. Isobaric tag for relative and absolute quantitation labeling and liquid chromatography-tandem mass spectrometry was performed for identifying proteins in the sperm of infertile and fertile males. Differentially expressed proteins were analyzed via the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases through the Database for Annotation, Visualization, and Integrated Discovery, and protein-protein networks were produced using the Search Tool for Retrieval of Interacting Genes. Immunofluorescence and western blotting verified the differential expression of Y-box-binding protein 1(YBX1), adenylate kinase 1 (AK1), and aconitase 2, mitochondrial (ACO2) proteins. Altogether, 3444 proteins were identified in the sperm of infertile and fertile males, and 938 were differentially expressed between the two groups. Pairwise comparisons revealed that 226 and 712 proteins were significantly upregulated and downregulated in infertile males, respectively. These proteins were significantly enriched in metabolic pathways as per KEGG enrichment analysis. YBX1 expression was upregulated in the sperm heads of patients requiring ICSI treatment, whereas AK1 and ACO2, which are critical enzymes involved in energy metabolism, were downregulated in the sperm tails of the same patients. This result indicates that metabolism may have a crucial role in maintaining normal sperm function. Overall, our results provide insights that will further help in investigating the pathogenic mechanisms of infertility and possible therapeutic strategies.

Identification of new protein biomarkers associated with the boar fertility using iTRAQ-based quantitative proteomic analysis

In this study, we performed the isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis in the spermatozoa of Landrace boars with different fertility potentials and investigated the ability of sperm acrosome associated 4 (SPACA4) and IZUMO family member 2 (IZUMO2) to predict the reproductive perform of boars. The iTRAQ results revealed that 202 proteins were up-regulated and 43 proteins were down-regulated in the spermatozoa from high fertility boars. SPACA4 and IZUMO2 protein levels were significantly up-regulated in the spermatozoa from high fertility boars. SPACA4 and IZUMO2 expression were specifically detected in the adult boar testis. SPACA4 levels were positively correlated with Sow's farrowing rate and reproductive efficiency, but not litter size. IZUMO2 were positively correlated with litter size, Sow's farrowing rate and reproductive efficiency. Treating the boar semen with SPACA4 or IZUMO2 antibodies for 30 min and 60 min failed to affect the sperm motility; while treating the semen with SPACA4 antibody significantly reduced the fertilization and cleavage rates. Similar results for fertilization and cleavage rates were found in IZUMO2 antibody-treated semen. Collectively, our results indicated that protein levels of SPACA4 and IZUMO2 in the spermatozoa were positively related to the reproductive performance of Landrace boars.

Quantitative analysis of proteins related to chemoresistance to paclitaxel and carboplatin in human SiHa cervical cancer cells via iTRAQ

Objective

This study aimed to identify proteins related to paclitaxel and carboplatin chemoresistance in cervical cancer.

Methods

Quantitative proteomic analysis was performed on normal SiHa cells and those treated with paclitaxel and carboplatin for 14 days, with isobaric tags for relative and absolute quantitation (iTRAQ) analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to identify related processes and differentially expressed proteins.

Results

A total of 67 and 96 differentially expressed proteins were identified in the paclitaxel- and carboplatin- treated groups, respectively. GO and KEGG enrichment analyses identified 53 (43 upregulated and 10 downregulated) and 85 differentially expressed proteins (70 upregulated and 15 downregulated) in the paclitaxel- and carboplatin-treated groups, respectively. The cell counting kit-8 results revealed that APOA1 was overexpressed in both the paclitaxel- and carboplatin- resistant SiHa cells compared with the control cells. Immunohistochemistry showed that APOA1 was highly expressed in the paclitaxel- and carboplatin- resistant squamous cell carcinoma of the cervix.

Conclusion

This study is the first to use iTRAQ to identify paclitaxel- and carboplatin- resistance proteins in cervical cells. We identified several proteins previously unassociated with paclitaxel and carboplatin resistance in cervical cancer, thereby expanding our understanding of paclitaxel and carboplatin resistance mechanisms. Moreover, these findings indicate that the APOA1 protein could serve as a potential marker for monitoring and predicting paclitaxel and carboplatin resistance levels.

Cellular Mechanism Underlying Hydrogen Sulfide Mediated Epithelial K+ Secretion in Rat Epididymis

As a novel gasotransmitter, hydrogen sulfide (H₂S) elicits various physiological actions including smooth muscle relaxation and promotion of transepithelial ion transport. However, the pro-secretory function of H₂S in the male reproductive system remains largely unclear. The aim of this study is to elucidate the possible roles of H₂S in modulating rat epididymal intraluminal ionic microenvironment essential for sperm storage. The results revealed that endogenous H₂S-generating enzymes cystathionine β-synthetase (CBS) and cystathionine γ-lyase (CSE) were both expressed in rat epididymis. CBS located predominantly in epithelial cells whilst CSE expressed primarily in smooth muscle cells. The relative expression level of CBS and CSE escalated from caput to cauda regions of epididymis, which was paralleled to the progressively increasing production of endogenous H₂S. The effect of H₂S on epididymal epithelial ion transportation was investigated using short-circuit current (I_SC), measurement of intracellular ion concentration and in vivo rat epididymal microperfusion. Our data showed that H₂S induced transepithelial K⁺ secretion via adenosine triphosphate-sensitive K⁺ (K_ATP) channel and large conductance Ca²⁺-activated K⁺ (BK_Ca) channel. Transient receptor potential vanilloid 4 (TRPV4) channel-mediated Ca²⁺ influx was implicated in the activation of BK_Ca channel. In vivo studies further demonstrated that H₂S promoted K⁺ secretion in rat epididymal epithelium. Inhibition of endogenous H₂S synthesis caused a significant decrease in K⁺ concentration of cauda epididymal intraluminal fluid. Moreover, our data demonstrated that high extracellular K⁺ concentration actively depressed the motility of cauda epididymal sperm in a pH-independent manner. Collectively, the present study demonstrated that H₂S was vital to the formation of high K⁺ concentration in epididymal intraluminal fluid by promoting the transepithelial K⁺ secretion, which might contribute to the maintenance of the cauda epididymal sperm in quiescent dormant state before ejaculation.

Influence of antifertility agents Dutasteride and Nifedipine on CatSper gene level in epididymis during sperm maturation in BALB/c mice

Calcium (Ca²⁺) signaling is critical for successful fertilization. In spermatozoa, capacitation, hyperactivation of motility and the acrosome reaction are all mediated by increases in intracellular Ca²⁺ through CatSper (sperm-specific cation channel). The CatSper channel complex contains four pore-forming α subunits (CatSper1-4) and five accessory subunits called β, δ, ε, γ and ζ. Genetic deletion of any of the four CatSper genes in mice results in loss of hyperactivated motility and male infertility. Despite their vital role in male fertility, almost very little is known about influence of antifertility agents on CatSper gene expression in epididymis and epididymal spermatozoa. Therefore, we performed quantitative real-time qPCR analysis for CatSper expression in the epididymis and epididymal sperm of BALB/c mice after treatment with Dutasteride (DS), a dual 5-α reductase inhibitor and Nifedipine (NF) a calcium channel blocker as positive control. We observed that treatment with antifertility agents Dutasteride and Nifedipine induced significant decreases in the caput and cauda epididymal sperm counts, motility and fertility which could partly be attributed to alteration in the normal morphology of the sperm associated with downregulation/upregulation of CatSper mRNAs in epididymis and epididymal spermatozoa of male BALB/c mice. These can be explained on the basis of interference with mechanisms affecting calcium ion signaling resulting in changes in intracellular calcium required for sperm activity, finally affecting sperm maturation and fertility of male BALB/c mice. These studies provide some novel avenues for developing new male contraceptives in future.

Age-associated expression of vitamin D receptor and vitamin D-metabolizing enzymes in the male reproductive tract and sperm of Hu sheep

The cellular response to 1,25-dihydroxyvitamin D₃ (Vit D₃; biologically active form of Vitamin D) is complex and depends not only on Vitamin D receptor (VDR) expression but also on cellular uptake of circulating Vit D₃ and the presence and activity of Vitamin D-metabolizing enzyme. This study evaluated the expression of VDR and Vitamin D-metabolizing enzymes in the ram reproductive tract at different developmental stages and in spermatozoa. Nearly all cell types in the testes and epithelial cells of the caput, corpus, and cauda expressed VDR, CYP27B1, and CYP24A1 proteins. The mRNA and protein expression of CYP2R1, CYP27A1, and CYP27B1 in the testes and cauda increased significantly with increasing age (P < 0.05). However, epididymal VDR mRNA and protein expression showed no significant difference (P < 0.05) between adult (9- and 24-month-old) and prepubertal (3-month-old) rams. Furthermore, VDR and CYP24A1 were mainly concentrated in the mid-piece of ejaculated or cauda epididymis spermatozoa or both. Additionally, VDR and CYP27B1 mRNA and protein expression levels were significantly higher in ejaculated spermatozoa than in cauda epididymal spermatozoa (P < 0.05). Moreover, VDR and CYP24A1 expression was significantly higher in high-motility than in low-motility spermatozoa (P < 0.05). The diverse expression patterns of VDR and Vitamin D-metabolizing enzymes in the ram reproductive tract at different developmental stages and spermatozoa suggest it plays a potential role in spermatogenesis.

Seasonal changes in the protein profile and enzyme activity of the epididymal luminal fluid in the lizard, Eutropis carinata (Schneider, 1801)

The epididymis of the male reproductive system is known to be involved in sperm maturation via the production of polypeptides, glycoproteins, surface proteins, enzymes and other factors. During the annual reproductive cycle, the epididymis of the lizard Eutropis carinata undergoes dramatic changes, both morphologically and biochemically, that occur in a well-organized sequence. The present study reveals the sequential changes that occur in the production and concentration of proteins in the epididymal luminal fluid throughout the annual reproductive cycle. A one-dimensional electrophoretic profile of the epididymal luminal proteins revealed a total of 18 bands in the regenerative phase, 22 bands during breeding and 17 bands in the post-breeding as well as regressed phases of the reproductive cycle. By two-dimensional electrophoresis, the protein complexes that are unique to the breeding phase were further resolved based on their pI and the molecular weight of each protein of the protein complex was determined. This is the first study to observe that proteins that are present during the reproductively inactive phase disappear during the reproductively active phase. The Periodic Acid Schiff (PAS) test for protein profiles revealed the presence of proteins with a carbohydrate moiety. Certain enzymes, such as acid phosphatase, alkaline phosphatase, and α-glucosidase, are highly sensitive to seasonal changes and their activity parallels the production of the epididymal proteins. This study provides evidence for androgen-dependent cyclical changes in the pattern of protein profiles and enzyme activity of the epididymal lumen in the lizard E. carinata.

The dynamic metabolomic changes throughout mouse epididymal lumen fluid potentially contribute to sperm maturation

Epididymal lumen fluids are directly responsible for sperm maturation. However, very little is known about the molecular details of small molecule metabolites in the epididymal lumen fluids until now. Here we identified and compared the metabolic profiles of mouse caput and cauda epididymal lumen fluids using GC-MS technique. Among 236 metabolites identified in caput and cauda epididymis, 36 were significantly enriched in caput epididymis while 18 were significantly enriched in cauda epididymis. Pathway analysis identified ascorbate and aldarate metabolism and beta-alanine metabolism as most relevant pathways in caput and cauda epididymis, respectively. Ascorbate, dehydroascorbic acid and beta-alanine associated with these two pathways were firstly reported in mouse epididymal lumen fluids and might play important roles in sperm maturation.