Morphological and histochemical characterization of the seminiferous epithelial and Leydig cells of the turkey

Comparative Analysis of mRNA and lncRNA Expression Profiles in Testicular Tissue of Sexually Immature and Sexually Mature Mongolian Horses

Testicular development and spermatogenesis are tightly regulated by both coding and non-coding genes, with mRNA and lncRNA playing crucial roles in post-transcriptional gene expression regulation. However, there are significant differences in regulatory mechanisms before and after sexual maturity. Nevertheless, the mRNAs and lncRNAs in the testes of Mongolian horses have not been systematically identified. In this study, we first identified the testicular tissues of sexually immature and sexually mature Mongolian horses at the tissue and protein levels, and comprehensively analyzed the expression profiles of mRNA and lncRNA in the testes of 1-year-old (12 months, n = 3) and 10-year-old (n = 3) Mongolian horses using RNA sequencing technology. Through gene expression analysis, we identified 16,582 mRNAs and 2128 unknown lncRNAs that are commonly expressed in both sexually immature and sexually mature Mongolian horses. Meanwhile, 9217 mRNAs (p < 0.05) and 2191 unknown lncRNAs (p < 0.05) were identified as differentially expressed between the two stages, which were further validated by real-time fluorescent quantitative PCR and analyzed using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). The analysis results showed that genes in the sexually immature stage were mainly enriched in terms related to cellular infrastructure, while genes in the sexually mature stage were enriched in terms associated with hormones, metabolism, and spermatogenesis. In summary, the findings of this study provide valuable resources for a deeper understanding of the molecular mechanisms underlying testicular development and spermatogenesis in Mongolian horses and offer new perspectives for future related research.

A first complete catalog of highly expressed genes in eight chicken tissues reveals uncharacterized gene families specific for the chicken testis

Based on next-generation sequencing, we established a repertoire of differentially overexpressed genes (DoEGs) in eight adult chicken tissues: the testis, brain, lung, liver, kidney, muscle, heart, and intestine. With 4,499 DoEGs, the testis had the highest number and proportion of DoEGs compared with the seven somatic tissues. The testis DoEG set included the highest proportion of long noncoding RNAs (lncRNAs; 1,851, representing 32% of the lncRNA genes in the whole genome) and the highest proportion of protein-coding genes (2,648, representing 14.7% of the protein-coding genes in the whole genome). The main significantly enriched Gene Ontology terms related to the protein-coding genes were "reproductive process," "tubulin binding," and "microtubule cytoskeleton." Using real-time quantitative reverse transcription-polymerase chain reaction, we confirmed the overexpression of genes that encode proteins already described in chicken sperm [such as calcium binding tyrosine phosphorylation regulated (CABYR), spermatogenesis associated 18 (SPATA18), and CDK5 regulatory subunit associated protein (CDK5RAP2)] but whose testis origin had not been previously confirmed. Moreover, we demonstrated the overexpression of vertebrate orthologs of testis genes not yet described in the adult chicken testis [such as NIMA related kinase 2 (NEK2), adenylate kinase 7 (AK7), and CCNE2]. Using clustering according to primary sequence homology, we found that 1,737 of the 2,648 (67%) testis protein-coding genes were unique genes. This proportion was significantly higher than the somatic tissues except muscle. We clustered the other 911 testis protein-coding genes into 495 families, from which 47 had all paralogs overexpressed in the testis. Among these 47 testis-specific families, eight contained uncharacterized duplicated paralogs without orthologs in other metazoans except birds: these families are thus specific for chickens/birds.NEW & NOTEWORTHY Comparative next-generation sequencing analysis of eight chicken tissues showed that the testis has highest proportion of long noncoding RNA and protein-coding genes of the whole genome. We identified new genes in the chicken testis, including orthologs of known mammalian testicular genes. We also identified 47 gene families in which all the members were overexpressed, if not exclusive, in the testis. Eight families, organized in duplication clusters, were unknown, without orthologs in metazoans except birds, and are thus specific for chickens/birds.

Steps of spermiogenesis in the ostrich (Struthio camelus)

Few studies describe the sequence of morphological events that characterize spermiogenesis in birds. In this paper, the clearly observable steps of spermiogenesis are described and illustrated for the first time in a commercially important ratite, the ostrich, based on light microscopy of toluidine blue-stained plastic sections. Findings were supplemented and supported by ultrastructural observations, PNA labeling of acrosome development, and immunocytochemical labeling of isolated spermatogenic cells. Spermiogenesis in the ostrich followed the general pattern described in non-passerine birds. Eight steps were identified based on changes in nuclear shape and contents, positioning of the centriolar complex, and acrosome development. Only two steps could be recognized with certainty during development of the round spermatid which contributed to the fewer steps recorded for the ostrich compared to that described in some other bird species. The only lectin that displayed acrosome reactivity was PNA and only for the first three steps of spermiogenesis. This suggests that organizational and/or compositional changes may occur in the acrosome during development and merits further investigation. Immunological labeling provided additional evidence to support the finding of previous studies that the tip of the nucleus in the ostrich is shaped by the forming acrosome and not by the microtubular manchette. To our knowledge, this is the first complete description of spermiogenesis in ostrich and one of few in any avian species. In addition to comparative reproduction and animal science, this work has implications for evolutionary biology as the reported germ cell features provide a bridge between reptile and ratite-avian spermatogenesis.

Morpho-Histology and Morphometry of Chicken Testes and Seminiferous Tubules among Yellow-Feathered Broilers of Different Ages

Simple Summary

Testes are important male reproductive organs that in chickens have been greatly investigated, from pre-hatch to after sexual maturity. The present study investigated the changes in components that occur during growth, and evaluated morphometry of the seminiferous tubules (ST), as well as gonadosomatic index (GSI) in Gallus domesticus at different age stages. The left and right testes were harvested from 70 chickens, then fixed in alcoholic acetate formalin (AAF) fixative solution, and hematoxylin- and eosin-stained tissues were used for microscopic observations. The results revealed that the left testis (LT) and the right testis (RT) exhibited fuzzy ST features, with apoptotic resorption of many tubules observed in both testes of 1-wk-old chicks only. ST formation was completed at 1 month, with an increase of all morphometric parameters in both testes until sexual maturity (3-mo-old): the age at which we recorded the greatest GSI. This study provides details on ST apoptotic resorption, which is a process not yet reported in existing publications, as well as ST morphometry and GSI, from a juvenile stage of growth towards sexual maturity. This can serve as reference material and also as a data update to better understand the morpho-histological changes that occur in chicken testes during growth.

Abstract

Unlike in many mammals, poultry testes are found in the abdominal cavity where they develop and perform spermatogenesis at high body temperature. Scarce reports among current publications detail the growth of testes and ST morphometry among juvenile chicks. Therefore, this study aims to investigate changes in components occurring in Gallus domesticus testes, by assessing the GSI and morphologically and histologically evaluating the testes and ST morphometry from 1-wk- to 4-mo-old. Right and left testes were collected from 70 healthy chickens divided into seven age-related groups (n = 10) and then immersed into the alcoholic acetate formalin (AAF) fixative solution. Hematoxylin- and eosin-stained tissues were used for microscopic observations. The findings revealed that both testes exhibited smooth features from 1-wk-old to 1-mo-old, and thereafter showed a consistent increase in vascularization until 4-mo-old. Histologically, both testes exhibited unclear ST, with ST apoptotic resorption observed in the 1-wk-old chicks. Until 1-mo-old, ST formed and few spermatogonia differentiated into primary spermatocytes, with all spermatogenic cells observed at 3-mo-old, i.e., sexual maturity. These findings suggest that both testes develop in analogy, and their sizes including increases in length and diameter are related to the spermatogenic activity in the ST. Subsequently, ST resorption by apoptosis is assumed to participate in the physiological mechanism regulating germ cells (GC). Finally, the GSI tended to increase with growth.

Models and Molecular Markers of Spermatogonial Stem Cells in Vertebrates: To Find Models in Nonmammals

Spermatogonial stem cells (SSCs) are the germline stem cells that are essential for the maintenance of spermatogenesis in the testis. However, it has not been sufficiently understood in amphibians, reptiles, and fish because numerous studies have been focused mainly on mammals. The aim of this review is to discuss scientific ways to elucidate SSC models of nonmammals in the context of the evolution of testicular organization since rodent SSC models. To further understand the SSC models in nonmammals, we point out common markers of an SSC pool (undifferentiated spermatogonia) in various types of testes where the kinetics of the SSC pool appears. This review includes the knowledge of (1) common molecular markers of vertebrate type A spermatogonia including putative SSC markers, (2) localization of the markers on the spermatogonia that have been reported in previous studies, (3) highlighting the most common markers in vertebrates, and (4) suggesting ways of finding SSC models in nonmammals.

Chronic Dietary Exposure of Roosters to a Glyphosate-Based Herbicide Increases Seminal Plasma Glyphosate and AMPA Concentrations, Alters Sperm Parameters, and Induces Metabolic Disorders in the Progeny

The effects of chronic dietary Roundup (RU) exposure on rooster sperm parameters, fertility, and offspring are unknown. We investigated the effects of chronic RU dietary exposure (46.8 mg kg⁻¹ day⁻¹ glyphosate) for 5 weeks in 32-week-old roosters (n = 5 RU-exposed and n = 5 control (CT)). Although the concentrations of glyphosate and its main metabolite AMPA (aminomethylphosphonic acid) increased in blood plasma and seminal fluid during exposure, no significant differences in testis weight and sperm concentrations were observed between RU and CT roosters. However, sperm motility was significantly reduced, associated with decreased calcium and ATP concentrations in RU spermatozoa. Plasma testosterone and oestradiol concentrations increased in RU roosters. These negative effects ceased 14 days after RU removal from the diet. Epigenetic analysis showed a global DNA hypomethylation in RU roosters. After artificial insemination of hens (n = 40) with sperm from CT or RU roosters, eggs were collected and artificially incubated. Embryo viability did not differ, but chicks from RU roosters (n = 118) had a higher food consumption, body weight and subcutaneous adipose tissue content. Chronic dietary RU exposure in roosters reduces sperm motility and increases plasma testosterone levels, growth performance, and fattening in offspring.

Symbiont Transmission onto the Cell Surface of Early Oocytes in the Deep-Sea Clam Phreagena okutanii

Symbiotic associations with beneficial microorganisms endow a variety of host animals with adaptability to the environment. Stable transmission of symbionts across host generations is a key event in the maintenance of symbiotic associations through evolutionary time. However, our understanding of the mechanisms of symbiont transmission remains fragmentary. The deep-sea clam Phreagena okutanii harbors chemoautotrophic intracellular symbiotic bacteria in gill epithelial cells, and depends on these symbionts for nutrition. In this study, we focused on the association of these maternally transmitted symbionts with ovarian germ cells in juvenile female clams. First, we established a sex identification method for small P. okutanii individuals, and morphologically classified female germ cells observed in the ovary. Then, we investigated the association of the endosymbiotic bacteria with germ cells. We found that the symbionts were localized on the outer surface of the cell membrane of primary oocytes and not within the cluster of oogonia. Based on our findings, we discuss the processes and mechanisms of symbiont vertical transmission in P. okutanii.

Histological, histochemical, immunohistochemical and ultrastructural characterization of the testes of the dove

Avian testes have been used in the study of germ cell transfer, importantly for understanding the preservation and control of birds. For this purpose, we use light microscopy, electron microscopy and immunohistochemistry to understand the reproductive efficiency of dove testes. The tunica albuginea was thin and septula testes were not observed. The testicular parenchyma was formed mainly of closely packed convoluted seminiferous tubules with little interstitial area. Three types of spermatogonia were distinguished. The primary spermatocyte appeared as the largest spermatogenic cell and was identified at different stages of meiosis. Different morphological stages of the spermatid were categorized. Various cellular associations were described within the seminiferous epithelium. The cytoplasm of Sertoli cells was pale and ill defined due to its close relationship to the germinal epithelium. The spermatid attached to the luminal border of Sertoli cells and germ cells were closely associated. A single layer of myoid cells surrounded the seminiferous tubule. Testicular telocytes of doves were located in the peritubular region and near the blood vessels. Telopods appeared as long cytoplasmic processes arising from the cell body. Leydig cells were distributed singly or in small groups and cords. The intensity of androgen receptor (AR) immunostaining in the testes of the dove was established for the first time and is described in this paper.

Characterization of in vivo autophagy during avian spermatogenesis1

Spermatogenesis is a complex cellular process that includes many subcellular events that are essential for the production of healthy spermatozoa. Autophagy is a physiological process that plays a significant role in the process of spermatogenesis; however, autophagy during avian spermatogenesis has not yet been reported. In the current study, we characterized in vivo autophagy throughout the process of domestic fowl spermatogenesis. Autophagy-specific markers, including microtubule-associated protein light chain 3 (LC3), sequestosome 1 (p62), and autophagy-related 7 (Atg7), were used to confirm the occurrence of autophagy in testicular germ cells. The protein expression of Atg7, LC3, and p62 in domestic fowl testes was confirmed by Western blotting. The immunohistochemical staining indicated a strong localization of LC3 and Atg7 within spermiogenic cells (intermediate and late spermatids) and primary spermatocytes. However, poorly expressed in cells (spermatogonia) that were located near the basement membrane. The immunofluorescence staining results showed the opposite tendency for LC3 and p62. LC3 was more strongly localized within the elongated spermatids, while p62 was strongly localized within the early spermatids. Moreover, the ultrastructural components of autophagy were revealed by transmission electron microscopy. Well-developed autophagosomes and multivesicular bodies were found to be prominent in primary spermatocytes (zygotene and pachytene) and spermiogenic cells. Furthermore, other vesicular structures, such as early endosomes and amphisomes, were also observed during spermatogenesis. The above findings collectively suggest that autophagy is active during spermatogenesis and that the level of autophagy increases from the basal to the luminal regions of the seminiferous tubules of domestic fowl testes. We propose that autophagic pathways may be involved in multiple functions to sustain spermatogenesis.

An evolutionary approach to recover genes predominantly expressed in the testes of the zebrafish, chicken and mouse

Background

Previously, we have demonstrated that genes involved in ovarian function are highly conserved throughout evolution. In this study, we aimed to document the conservation of genes involved in spermatogenesis from flies to vertebrates and their expression profiles in vertebrates.

Results

We retrieved 379 Drosophila melanogaster genes that are functionally involved in male reproduction according to their mutant phenotypes and listed their vertebrate orthologs. 83% of the fly genes have at least one vertebrate ortholog for a total of 625 mouse orthologs. This conservation percentage is almost twice as high as the 42% rate for the whole fly genome and is similar to that previously found for genes preferentially expressed in ovaries. Of the 625 mouse orthologs, we selected 68 mouse genes of interest, 42 of which exhibited a predominant relative expression in testes and 26 were their paralogs. These 68 mouse genes exhibited 144 and 60 orthologs in chicken and zebrafish, respectively, gathered in 28 groups of paralogs. Almost two thirds of the chicken orthologs and half of the zebrafish orthologs exhibited a relative expression ≥50% in testis. Finally, our focus on functional in silico data demonstrated that most of these genes were involved in the germ cell process, primarily in structure elaboration/maintenance and in acid nucleic metabolism.

Conclusion

Our work confirms that the genes involved in germ cell development are highly conserved across evolution in vertebrates and invertebrates and display a high rate of conservation of preferential testicular expression among vertebrates. Among the genes highlighted in this study, three mouse genes (Lrrc46, Pabpc6 and Pkd2l1) have not previously been described in the testes, neither their zebrafish nor chicken orthologs. The phylogenetic approach developed in this study finally allows considering new testicular genes for further fundamental studies in vertebrates, including model species (mouse and zebrafish).

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1462-8) contains supplementary material, which is available to authorized users.

Ethyl Pyruvate Ameliorates The Damage Induced by Cyclophosphamide on Adult Mice Testes

Background

Cyclophosphamide (CP) is a chemotherapy drug which causes deleterious effects on testicular tissue and increases free radicals in the body. The aim of this study is to investigate the protective effects of ethyl pyruvate (EP) on testicular improvement in CP treated animals.

Materials and Methods

In this experimental study, 15 male mice (6-8 weeks) were divided into 3 groups. The control group received normal saline (0.1 ml/day), intraperitoneal (IP), CP group received CP (15 mg/kg/week, IP), and the CP+EP group received EP (40 mg/kg/day, IP) plus CP. After 35 days, we assessed serum total antioxidant capacity (TAC) along with histomorphometric and histochemical analyses of the testicles.

Results

The mean thickness of the germinal epithelium, diameter of seminiferous tubules, and the number of Leydig cells in the CP+EP group were higher than those of the CP group (P<0.05). The number of the mast cells in the CP+EP group significantly reduced compared with the CP group (P<0.05). Alkaline phosphatase (ALP), periodic acid-schiff (PAS) positive reactions and lipid granules in cytoplasm of the Leydig cells in the CP group increased compared with the other groups (P<0.05). TAC in the CP group significantly reduced compared with the other groups (P<0.05).

Conclusion

This study showed the ability of EP to reduce the destructive side effects of CP in the adult mice reproductive system.

Identification of side population cells in chicken embryonic gonads

The side population (SP) phenotype, defined by the ability of a cell to efflux fluorescent dyes such as Hoechst, is common to several stem/progenitor cell types. In avian species, SP phenotype has been identified in pubertal and adult testes, but nothing is known about its expression during prenatal development of a male gonad. In this study, we characterized the Hoechst SP phenotype via the cytofluorimetric analysis of disaggregated testes on different days of chicken embryonic development. Male prenatal gonads contained a fraction of SP cells at each stage analyzed. At least two main SP fractions, named P3 and P4, were identified. The percentage of P3 fraction decreased as development proceeds, whereas P4 cell number was not affected by gonad growth. Functional inhibition of BCRP1 channel membrane using Verapamil and/or Ko143 showed that P3, but not P4 phenotype, was dependent on BCRP1 activity. Molecular analysis of both P3- and P4-sorted fractions revealed a differential RNA expression pattern, indicating that P3 cells mainly contained germinal stem cell markers, whereas P4 was preferentially composed of both Sertoli and Leydig cell progenitor markers. Finally, these findings provided evidence that the SP phenotype is a common feature of both germ and somatic cells detected in chicken developing testis.

Effects of mono-(2-ethylhexyl) phthalate (MEHP) on chicken germ cells cultured in vitro

In recent decades, many toxicological tests based on in vivo or in vitro models, mainly from mammalian (rat-mouse) and fish species, were used to assess the risks raised by contact or ingestion of molecules of pharmaceutical, agricultural, or natural origin. But no, or few, in vitro tests using other non-mammalian models such as bird have been explored despite their advantages: the embryonic gonads of birds have a high plasticity of development sensitive to estrogen, and sperm production is nearly two times faster than in rodents. Hence, we have established an in vitro culture of germ cells and somatic cells from chicken post-natal testis, and we have evaluated the sensitivity against the endocrine disruptor compound mono-(2-ethylhexyl) phthalate (MEHP) in comparison to previous studies using rodent and human models. After 96 h of exposure in presence of 10 μM MEHP, chicken seminiferous tubules cultures present a structural alteration, a reduction in cell proliferation and in germ cells population. Apoptosis of germ and somatic cells increases in presence of 1 μM MEHP. Furthermore, MEHP does not affect inhibin B and lactate production by Sertoli cells. These results are in accordance with previous studies using rat, mice, or human culture of testicular cells and in similar range of exposures or even better sensitivity for some "end-points" (biological parameters). In conclusion, the establishment of this postnatal testicular cells culture could be considered as an alternative method to in vivo experiments frequently used for evaluating the impact on the terrestrial wildlife species. This method could be also complementary to mammal model due to the limiting number of animals used and its elevated sensitivity.

Restoration of spermatogenesis after transplantation of c-Kit positive testicular cells in the fowl

Transplantation of male germ line cells into sterilized recipients has been used in mammals for conventional breeding as well as for transgenesis. We have previously adapted this approach for the domestic chicken and we present now an improvement of the germ cell transplantation technique by using an enriched subpopulation of c-Kit-positive spermatogonia as donor cells. Dispersed c-Kit positive testicular cells from 16 to 17 week-old pubertal donors were transplanted by injection directly into the testes of recipient males sterilized by repeated gamma irradiation. We describe the repopulation of the recipient's testes with c-Kit positive donor testicular cells, which resulted in the production of functional heterologous spermatozoa. Using manual semen collection, the first sperm production in the recipient males was observed about nine weeks after the transplantation. The full reproduction cycle was accomplished by artificial insemination of hens and hatching of chickens.