Inhibition of testicular germ cell apoptosis and differentiation in mice misexpressing Bcl-2 in spermatogonia

Ultrastructural Analysis of Large Japanese Field Mouse (Apodemus speciosus) Testes Exposed to Low-Dose-Rate (LDR) Radiation after the Fukushima Nuclear Power Plant Accident

Since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, great attention has been paid to the impact of chronic low-dose-rate (LDR) radiation exposure on biological systems. The reproductive system is sensitive to radiation, with implications connected to infertility. We investigated the testis ultrastructure of the wild large Japanese field mouse (Apodemus speciosus) from three areas contaminated after the FDNPP accident, with different levels of LDR radiation (0.29 µSv/h, 5.11 µSv/h, and 11.80 µSv/h). Results showed good preservation of the seminiferous tubules, comparable to the unexposed animals (controls), except for some ultrastructural modifications. Increases in the numerical density of lipid droplet clusters in spermatogenic cells were found at high levels of LDR radiation, indicating an antioxidant activity rising due to radiation recovery. In all groups, wide intercellular spaces were found between spermatogenic cells, and cytoplasmic vacuolization increased at intermediate and high levels and vacuolated mitochondria at the high-level. However, these findings were also related to the physiological dynamics of spermatogenesis. In conclusion, the testes of A. speciosus exposed to LDR radiation associated with the FDNPP accident showed a normal spermatogenesis, with some ultrastructural changes. These outcomes may add information on the reproductive potential of mammals chronically exposed to LDR radiation.

Starvation-induced autophagy modulates spermatogenesis and sperm quality in Nile tilapia

Spermatogenesis is a finely regulated process that involves the interaction of several cellular mechanisms to ensure the proper development and maturation of germ cells. This study assessed autophagy contribution and its relation to apoptosis in fish spermatogenesis during starvation. To that end, Nile tilapia males were subjected to 0 (control), 7, 14, 21, and 28 days of starvation to induce autophagy. Testes samples were obtained for analyses of spermatogenesis by histology, electron microscopy, immunohistochemistry, and western blotting. Sperm quality was assessed using a computer-assisted sperm analysis (CASA) system. Data indicated a significant reduction in gonadosomatic index, seminiferous tubule area, and spermatozoa proportion in fish subject to starvation compared to the control group. Immunoblotting revealed a reduction of Bcl2 and Beclin 1 associated with increased Bax and Caspase-3, mainly after 21 and 28 days of starvation. LC3 and P62 indicated reduced autophagic flux in these starvation times. Immunolabeling for autophagic and apoptotic proteins occurred in all development stages of the germ cells, but protein expression varied throughout starvation. Beclin 1 and Cathepsin D decreased while Bax and Caspase-3 increased in spermatocytes, spermatids, and spermatozoa after 21 and 28 days. Autophagic and lysosomal proteins colocalization indicated the fusion of autophagosomes with lysosomes and lysosomal degradation in spermatogenic cells. The CASA system indicated reduced sperm motility and velocity in animals subjected to 21 and 28 days of starvation. Altogether, the data support autophagy acting at different spermatogenesis stages in Nile tilapia, with decreased autophagy and increased apoptosis after 21 and 28 days of starvation, which results in a decrease in the spermatozoa number and sperm quality.

Effect of Different Vitrification Techniques on Viability and Apoptotic Index of Domestic Cat Testicular Tissue Cells

Vitrification is essential for successful tissue cryopreservation and biobanking in wild cats. This study aimed to compare different methods of vitrification (Ovarian Tissue Cryosystem-OTC, Straws-STW, and Solid Surface vitrification-SSV) for testicular fragment vitrification in tom cats. Testicular fragments were recovered from five adult tom cats and subjected to equilibrium vitrification using different cryovials and methods under the same conditions of vitrification solutions and cryoprotectants. The efficiencies of the methods were evaluated using histological analysis of spermatogonia and Sertoli cell nuclei, seminiferous tubular basement membrane detachment, and the gonadal epithelium shrinkage score scale. Cell viability was assessed using Hoechst PI and Terminal deoxynucleotidyl transferase nick end labeling (TUNEL) assay. The results showed that OTC is an effective vitrification method for maintaining the distinction between spermatogonia and Sertoli cells. OTC was similar to the control for basal membrane detachment parameters (p = 0.05). Epithelial shrinkage was low in the SSV group, which showed the highest percentage of viable cells among the vitrified groups (p = 0.0023). The OTC and SSV vitrification methods were statistically similar in terms of the percentage of TUNEL-positive cells (p = 0.05). Therefore, OTC and SSV provide favorable conditions for maintaining viable cat testicular tissue cells after vitrification.

Evidence of the inhibitory role of visfatin in the testicular activity of mice during the infantile stage

Adipokines have emerged as regulators of gonadal function in many mammalian and non-mammalian species. In the present study, we have investigated the developmental expression of testicular and ovarian visfatin along with its possible role in the testicular activity infantile stages. Previously, our group has the extensive role of ovarian visfatin in relation to steroidogenesis, proliferation, and apoptosis in female mice. To the best of our knowledge, no study has shown the role of visfatin in mice testis. Our results from the previous study and present study showed that visfatin in the testis and ovaries are developmentally regulated. To unravel the role of visfatin, we have used FK866, as visfatin inhibitor. FK866 was used as a visfatin inhibitor, to decipher the role of visfatin in the testis of mice. Our results showed that visfatin expression in the testis was developmentally regulated in the testis. Leydig cells as well as germ have shown the presence of visfatin in mice testis, which suggest its role in testicular steroidogenesis and spermatogenesis. Furthermore, visfatin inhibition by FK866 significantly increased the testosterone secretion, and expression of AR, Bcl2, and ERα. The expression of GCNA was upregulated by FK866 treatment. These results suggest that visfatin has an inhibitory role in testicular steroidogenesis and germ cell proliferation in the infantile stage. Further research is required to define the precise role of visfatin in infantile mice testis.

Postnatal developmental expression of apelin receptor proteins and its role in juvenile mice testis

The expression of apelin system has been shown in the adult testis of rat and mice. It has also been emphasized that regulation of testicular activity in early stages is important to sustain normal testicular activity in adulthood. Since the expression of apelin receptor (APJ) has been shown in the adult testis, moreover, developmental expression of APJ and its role has not been explored yet. Thus, we have examined the testicular expression of APJ during postnatal stages with special reference to proliferation, apoptosis and hormone secretion in early postnatal stage. Postnatal analysis showed that circulating apelin was lowest at PND1 and maximum at PND42. Among testosterone, estrogen and androstenedione, only circulating testosterone showed a gradual increase from PND1 to PND42. Testicular expression of APJ was also developmenatly regulated from PND1 to PND42, revealing a positive correlation with circulating apelin, testosterone, and androstenedione. Immunohistochemical study showed that APJ was mainly confined to Leydig cells of early postnatal stages, whereas, seminiferous tubules at PND42 showed immunostaining in the round spermatids. APJ inhibition from PND14-PND20 by ML221 suppressed the testicular proliferation, increased apoptosis and increased estrogen secretion. However, expression of AR was down-regulated by ML221 treatment. Furthermore, ML221 decreased the abundance of p-Akt. In vitro study also showed that APJ antagonist, ML221 decreased AR expression. These results suggests that apelin signaling during early developmental stages might be required to stimulate the germ cell proliferation, and inhibition of apoptosis. Both in vivo and in vitro study have shown that expression of AR was regulated by apelin signaling. Since the first wave spermatogenesis involves proliferation and apoptosis, therefore, further study would be required to unravel the exact mechanism of apelin mediated regulation of testicular activity during early postnatal stages. In conclusion, the present results are an indicative of apelin mediated signaling during early postnatal stage for regulation of germ cell proliferation, apoptosis and AR expression.

Influence of Vitrification Device, Warming Protocol, and Subsequent In Vitro Culture on Structural Integrity of Testicular Fragments from Adult Domestic Cats

The objective of the study was to evaluate the integrity of cat testicular tissues after vitrification with different devices followed by different warming conditions. The influence of vitro culture for 24 hours after warming also was examined. Testicular tissues from adult domestic cats were dissected in small fragments that were vitrified using Cryotop^® or threaded on fine needles, warmed (directly at 37°C or with a preliminary 10 seconds exposure to 50°C), and/or cultured in vitro for an additional 24 hours. For each treatment group, tissues were assessed based on histology, apoptosis, and sperm DNA integrity. Results showed that fragments of testicular tissues were efficiently cryopreserved (maintaining the quality of all cell types) with vitrification with Cryotop followed by direct warming at 37°C, and additional culture of 24 hours at 38.5°C. These encouraging results are paving the road to optimize preservation protocols and use them for systematic banking of tissues from genetically valuable felids.

Repression precedes independent evolutionary gains of a highly specific gene expression pattern

Highly specific expression patterns can be caused by the overlapping activities of activator and repressor sequences in enhancers. However, few studies illuminate how these sequences evolve in the origin of new enhancers. Here, we show that expression of the bond gene in the semicircular wall epithelium (swe) of the Drosophila melanogaster male ejaculatory bulb (EB) is controlled by an enhancer consisting of an activator region that requires Abdominal-B driving expression in the entire EB and a repressor region that restricts this expression to the EB swe. Although this expression pattern is independently gained in the distantly related Scaptodrosophila lebanonensis and does not require Abdominal-B, we show that functionally similar repressor sequences are present in Scaptodrosophila and also in species that do not express bond in the EB. We suggest that during enhancer evolution, repressor sequences can precede the evolution of activator sequences and may lead to similar but independently evolved expression patterns.

Pu et al. show that the independent gain of a highly specific expression pattern across distantly related species may be because of the preexistence of repressor sequences that precedes the diversification of these species. This may reflect a general mechanism underlying the evolution of highly specific enhancers.

Maternal undernutrition during pregnancy and lactation increases transcription factors, ETV5 and GDNF, and alters regulation of apoptosis and heat shock proteins in the testis of adult offspring in the rat

We tested whether changes in Sertoli cell transcription factors and germ cell heat shock proteins (HSPs) are linked to the effects of maternal undernutrition on male offspring fertility. Rats were fed ad libitum with a standard diet (CONTROL) throughout pregnancy and lactation or with 50% of CONTROL intake throughout pregnancy (UNP) or lactation (UNL) or both periods (UNPL). After postnatal Day 21, 10 male pups per group were fed a standard diet ad libitum until postnatal Day 160 when testes were processed for histological, mRNA and immunohistochemical analyses. Compared with CONTROL: caspase-3 was increased in UNP and UNPL (P=0.001); Bax was increased in UNL (P=0.002); Bcl-2 (P<0.0001) was increased in all underfed groups; glial cell line-derived neurotrophic factor (P=0.002) was increased in UNP and UNL; E twenty-six transformation variant gene 5 and HSP70 were increased, and HSP90 was diminished in all underfed groups (P<0.0001). It appears that maternal undernutrition during pregnancy and lactation disrupts the balance between proliferation and apoptosis in germ cells, increasing germ cell production and perhaps exceeding the support capacity of the Sertoli cells. Moreover, fertility could be further compromised by changes in meiosis and spermiogenesis mediated by germ cell HSP90 and HSP70.

Protective Effects of Taif Rosewater Against Testicular Impairment Induced By Lead Intoxication In Rats

This study explored treatment with Taif rosewater (RW) to protect against lead acetate-(PbAc) induced male testicular impairment. Male Wistar rats were divided into four groups and provided drinking water containing 4% Taif RW, PbAc, 4% Taif RW followed by PbAc or normal water (controls). Serum for hormonal assays and testicular tissue for histopathological and immunohistochemical examinations and molecular study were obtained. Epididymal spermatozoa were collected for analysis. PbAc significantly reduced serum levels of follicle-stimulating hormone (FSH), luteinising hormone (LH) and testosterone, as well as sperm count and motility percentage. It also caused a significant reduction in SOD and catalase activities, testicular CYTP450_SCC , CYP17α, StAR mRNA expressions and the percentage of Bcl-2 immunoreactivity. The percentage of caspase-3 and NF-ĸB immunoreactivities, as well as sperm abnormalities, was increased, as did the testicular degeneration associated with vacuolation and necrosis of spermatogenic cells. Pretreatment with Taif RW significantly reduced the negative effects of PbAc as shown by the increases in serum gonadotropins level, SOD and catalase activities, and percentage of Bcl-2 immunoreactivity, decreases in the percentage of caspase-3 and NF-ĸB immunoreactivities, and improved testicular histology and sperm parameters. These data provide evidence that Taif RW protects against testicular toxicity caused by PbAc.

Homo Sapiens (Human) microRNA 187 Expression Is Dysregulated in Testis of Non-obstructive Azoospermic Men

Introduction: MiRNA expression alterations are closely related to growth, proliferation, and cell development. In addition, miR-187 has been found to regulate cellular proliferation. Further, spermatogenesis is a highly complicated process which is regulated through several genes targeted by miRNAs. However, no study has completely addressed the etiology of spermatogenic impairments. Accordingly, the present study examined the expression pattern of Homo sapiens (human) microRNA (hsa-mir-187) in the testicular biopsies of infertile men with non-obstructive azoospermia (NOA) and Sertoli cell-only syndrome (SCOS) subtype in comparison with those with obstructive azoospermia (OA). Methods: Quantitative reverse‐transcription polymerase chain reaction analysis was performed to assess the expression level of hsa-mir-187 using the ΔΔCt method. Results: Our data indicated that hsa-mir-187 was significantly up-regulated in the testis of the SCOS group (P˂ 0.05) in comparison with the OA group. Conclusion: In general, the findings suggest that the differential expression of hsa-mir-187 is linked with male infertility and shed more light on molecular defects that underlie spermatogenic impairments.

Cuscuta chinensis flavonoids alleviate bisphenol A-induced apoptosis of testicular cells in male mice offspring

Bisphenol A (BPA) is a widespread environmental endocrine disruptor that has multiple effects on reproductive organ development. To investigate the effect of Cuscuta chinensis flavonoids (CCFs) on testicular apoptosis induced by BPA in male mice offspring, pregnant mice were administered intragastrically with BPA and CCF at gestation day (GD) 0.5-17.5. The testes of male offspring (F1 males) were collected at post-natal day (PND) 21 and PND 56 for the detection of related indicators. The results showed that compared with the BPA group, the testicular index in CCF groups was significantly increased at PND 21 (p < .01). For the mice of different concentrations of CCF groups, the expression levels of bax, caspase-9 and caspase-7 proteins were significantly decreased at PND 21 and PND 56, while the expression level of bcl-2 protein was significantly increased, and testicular apoptotic cells were also decreased significantly (p < .01 or p < .05). Forty mg/kg CCF has no significant difference compared with the control group. The results indicated that CCF could protect the testis development of F1 male mice by alleviating the apoptosis of testicular cells induced by BPA.

Effects of Exposure to Bisphenol A during Pregnancy on the Pup Testis Function

Testosterone plays an important prenatal role in male testis development. Bisphenol A (BPA) exposure during pregnancy affects testosterone levels and germ cell apoptosis of male pups, but little information is available for the mechanism. The aim of the present study was to investigate the mechanism by which BPA alters testosterone levels and germ cell apoptosis. Pregnant female C57BL/6J mice, throughout gestation, had access to drinking water containing BPA at 5 and 50 μg/mL. Male pups were euthanized on postnatal days (PNDs) 1, 14, and 35. Relative to control, BPA exposure at 5 and 50 μg/ml decreased testosterone level, as measured by chemiluminescent immunoassay, on PND14. Real-time PCR indicated mRNA levels for steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 3-β-hydroxysteroid dehydrogenase/△-5-4 isomerase (3β-HSD) were significantly lower in the BPA pups compared to control. Additionally, BPA increased the percentage of TUNEL-positive seminiferous tubules, decreased the mRNA level of Bcl-2, and increased Bax expression, indicative of increased apoptosis. These results suggest that BPA exposure in utero decreases the testosterone concentration by decreasing steroidogenic enzymes (StAR, CYP11A1, and 3β-HSD). Furthermore, BPA exposure increases the apoptosis of germ cells, which is associated with proapoptotic changes in the levels of Bcl-2 and Bax.

Dynein axonemal intermediate chain 2 plays a role in gametogenesis by activation of Stat3

We previously identified the mouse dynein axonemal intermediate chain 2 (Dnaic2) gene. This gene expresses a component of the axonemal dynein complex that functions in cilia or flagella. We found that overexpression of Dnaic2 results in female subfertility and male infertility. In this study, we generated Dnaic2 knockdown (KD) mice and identified the potential regulatory mechanisms involved in Dnaic2 function. For phenotype analysis, we found that body weight was lighter and size was smaller in Dnaic2 KD mice than in wild‐type mice. A total of 45% of these Dnaic2 KD mice were infertile due to sperm abnormalities in males, or had oocyte abnormalities and pathological changes in the tunica mucosa in the oviduct of females. Moreover, Dnaic2 overexpression enhanced the expression of proliferating cell nuclear antigen (PCNA) in the ovaries, which suggested that Dnaic2 stimulated proliferation of cells in the ovaries. However, PCNA expression in the testis of Dnaic2‐overexpressed mice was lower than that in controls. Additionally, the ratio of Bax/B‐cell lymphoma‐2(Bcl‐2) in the testis of Dnaic2‐overexpressed mice was higher than that in controls, which suggested that Dnaic2 inhibited cellular proliferation in the testis. To examine the molecular action of Dnaic2, immunoprecipitation analysis was used and showed that Dnaic2 protein interacted with signal transducer and activator of transcription 3 (Stat3). Molecular modelling analysis showed that Dnaic2 bound with the linker and SH2 domains of Stat3. Furthermore, overexpression of Dnaic2 promoted phosphorylation of Stat3. In conclusion, our study suggests that Dnaic2 plays a role in oogenesis and spermatogenesis by activation of Stat3.

Male infertility is associated with altered treatment course of men with cancer

This study aims to evaluate whether cancer treatments differ in infertile men compared to men who have undergone vasectomy and age-matched controls. We analyzed subjects from the Truven Health MarketScan Claims database from 2001 to 2009. Infertile men were identified through diagnosis and treatment codes. Comparison groups included vasectomized men and an age-matched cohort who were not infertile and had not undergone vasectomy. We considered cancer types previously associated with infertility that were diagnosed after the diagnosis of infertility. The treatment regimens were determined based on the presence of claims with CPT codes for chemotherapy (CTX), radiation (RTX) or surgical treatment (ST) for each entity in all study groups. Cases with multimodal treatments were also identified. As a result, CTX was similarly distributed among the infertile, vasectomized, and control groups. In contrast, RTX treatment length was shorter in infertile men. The frequency of multimodal treatment (i.e., radiation and chemotherapy) was twofold lower in men with infertility compared to other men. By focusing on treatment patterns for each cancer type among these groups, the duration of RTX and CTX was shorter in infertile men diagnosed with NHL compared to controls. We conclude that Infertile men diagnosed with cancer and specific cancer types experience different treatment courses, with shorter RTX and less combined RTX/CTX compared to fertile and vasectomized men. These differences could reflect differences in stage at presentation, biological behavior, or treatment responses in infertile men.

VEGFC/VEGFR3 Signaling Regulates Mouse Spermatogonial Cell Proliferation via the Activation of AKT/MAPK and Cyclin D1 Pathway and Mediates the Apoptosis by affecting Caspase 3/9 and Bcl-2

We have previously shown that the transcript levels of Vegfc and its receptor Vegfr3 were high in spermatogonia and extremely low in spermatocytes and spermatids. However, it remains unknown about the functions and the mechanisms of VEGFC/VEGFR3 signaling in regulating the fate determinations of spermatogonia. To this end, here we explored the role and signaling pathways of VEGFC/VEGFR3 by using a cell line derived from immortalized mouse spermatogonia retaining markers of mitotic germ cells, namely GC-1 cells. VEGFR3 was expressed in mouse primary spermatogonia and GC-1 cells. VEGFC stimulated the proliferation and DNA synthesis of GC-1 cells and enhanced the phosphorylation of PI3K-AKT and MAPK, whereas LY294002 (an inhibitor for AKT) and CI-1040 (an inhibitor for MAPK) blocked the effect of VEGFC on GC-1 cell proliferation. Furthermore, VEGFC increased the transcripts of c-fos and Egr1 and protein levels of cyclin D1, PCNA and Bcl-2. Conversely, the blocking of VEGFC/VEGFR3 signaling by VEGFR3 knockdown reduced the phosphorylation of AKT/MAPK and decreased the levels of cyclin D1 and PCNA. Additionally, VEGFR3 knockdown not only resulted in more apoptosis of GC-1 cells but also led to a decrease of Bcl-2 and promoted the cleavage of Caspase-3/9 and PARP. Collectively, these data suggested that VEGFC/VEGFR3 signaling promotes the proliferation of GC-1 cells via the AKT /MAPK and cyclin D1 pathway and it inhibits the cell apoptosis through Caspase-3/9, PARP and Bcl-2. Thus, this study sheds a novel insight to the molecular mechanisms underlying the fate decisions of mammalian spermatogonia.

The inhibitory effects of soybean isoflavones on testicular cell apoptosis in mice with type 2 diabetes

The aim of the study was to investigate the inhibitory effects of soybean isoflavones (SI) on testicular cell apoptosis in mice with type-2 diabetes, as well as any possible mechanisms of action. Thirty male C57BL/6J mice were randomly divided into the control, diabetic (model), and treatment (SI) groups (n=10 each). After treatment for 20 weeks, testicular cell apoptosis was detected and evaluated using DAPI staining. The expression and distribution of caspase-3 protein in testicular tissues was detected via immunohistochemistry, while caspase-3 mRNA expression was detected using RT-PCR. Bax and Bcl-2 protein expression was detected by western blot analysis. At week 20, DAPI staining showed that SI treatment significantly decreased testicular tissue cell apoptosis in diabetic mice. Immunohistochemical staining revealed that caspase-3 expression in the SI group was significantly reduced relative to the model group. RT-PCR showed that SI treatment significantly decreased caspase-3 mRNA expression relative to the model group. Western blot analysis revealed that SI treatment significantly decreased Bax protein expression and increased Bcl-2 protein expression (P<0.01). SI exhibited an inhibitory effect on testicular tissue cell apoptosis in mice with type 2 diabetes, with this effect possibly mediated by a decreased expression of caspase-3 and Bax and increased Bcl-2 protein expression.

Germ cell apoptosis and expression of Bcl-2 and Bax in porcine testis under normal and heat stress conditions

The aim of this study was to examine whether an elevated ambient temperature (37-40°C) had an effect on the apoptosis of germ cells and the expression of Bcl-2 and Bax in porcine testis. Six boars were used. Three boars were subjected to an elevated ambient temperature (37-40°C, 7days, 3h per day) as a heat stress (HS) group. The other 3 boars were kept in a room temperature house (20-27°C) as a control group. All boars were castrated and the testes were harvested. TUNEL assay was used for the detection of apoptotic cells. Immunohistochemistry, Western blotting and quantitative real-time PCR were used to analyze protein and mRNA levels of Bcl-2 and Bax in response to heat treatment. The results showed that apoptotic signals increased under heat stress conditions compared with the control (P<0.01), and the cell types most affected by heat treatment were spermatocytes and spermatids. In both the control and experimental groups, Bcl-2 was expressed in the cytoplasm and nucleus of spermatogonia, spermatocytes and differentiating spermatids and Bcl-2 preferentially localized close to the seminiferous tubule's luminal surface in late spermatocytes and spermatids. Compared with the control group, the expression levels of Bcl-2 protein and mRNA significantly increased in heat treatment group, while the expression levels of Bax protein and mRNA did not show significant changes between the control and experimental group. Low to moderate Bax immunoreactivity staining was observed in all kinds of germ cells in the control group. Strong staining was observed in spermatogonia, and low to moderate Bax staining was observed in spermatocytes and spermatids. A redistribution of Bax from a cytoplasmic to perinuclear or nuclear localization could be observed in the spermatogonia, spermatocytes and spermatids obtained in the heat treated group. These results showed that elevated ambient temperatures induced germ cell apoptosis. In response to heat stress, the expression of Bcl-2 increased and a redistribution of Bax from a cytoplasmic to a perinuclear or nuclear localization. This indicates that Bcl-2 and Bax may be involved in regulation of germ cell apoptosis induced by heat stress in boars.

Molecular and Cellular Mechanisms of Apoptosis during Dissociated Spermatogenesis

Apoptosis is a tightly controlled process by which tissues eliminate unwanted cells. Spontaneous germ cell apoptosis in testis has been broadly investigated in mammals that have an associated spermatogenesis pattern. However, the mechanism of germ cell apoptosis in seasonally breeding reptiles following a dissociated spermatogenesis has remained enigmatic. In the present study, morphological evidence has clearly confirmed the dissociated spermatogenesis pattern in Pelodiscus sinensis. TUNEL and TEM analyses presented dynamic changes and ultrastructural characteristics of apoptotic germ cells during seasonal spermatogenesis, implying that apoptosis might be one of the key mechanisms to clear degraded germ cells. Furthermore, using RNA-Seq and digital gene expression (DGE) profiling, a large number of apoptosis-related differentially expressed genes (DEGs) at different phases of spermatogenesis were identified and characterized in the testis. DGE and RT-qPCR analysis revealed that the critical anti-apoptosis genes, such as Bcl-2, BAG1, and BAG5, showed up-regulated patterns during intermediate and late spermatogenesis. Moreover, the increases in mitochondrial transmembrane potential in July and October were detected by JC-1 staining. Notably, the low protein levels of pro-apoptotic cleaved caspase-3 and CytC in cytoplasm were detected by immunohistochemistry and western blot analyses, indicating that the CytC-Caspase model might be responsible for the effects of germ cell apoptosis on seasonal spermatogenesis. These results facilitate understanding the regulatory mechanisms of apoptosis during spermatogenesis and uncovering the biological process of the dissociated spermatogenesis system in reptiles.

Erasure of DNA methylation, genomic imprints, and epimutations in a primordial germ-cell model derived from mouse pluripotent stem cells

The genome-wide depletion of 5-methylcytosines (5meCs) caused by passive dilution through DNA synthesis without daughter strand methylation and active enzymatic processes resulting in replacement of 5meCs with unmethylated cytosines is a hallmark of primordial germ cells (PGCs). Although recent studies have shown that in vitro differentiation of pluripotent stem cells (PSCs) to PGC-like cells (PGCLCs) mimics the in vivo differentiation of epiblast cells to PGCs, how DNA methylation status of PGCLCs resembles the dynamics of 5meC erasure in embryonic PGCs remains controversial. Here, by differential detection of genome-wide 5meC and 5-hydroxymethylcytosine (5hmeC) distributions by deep sequencing, we show that PGCLCs derived from mouse PSCs recapitulated the process of genome-wide DNA demethylation in embryonic PGCs, including significant demethylation of imprint control regions (ICRs) associated with increased mRNA expression of the corresponding imprinted genes. Although 5hmeCs were also significantly diminished in PGCLCs, they retained greater amounts of 5hmeCs than intragonadal PGCs. The genomes of both PGCLCs and PGCs selectively retained both 5meCs and 5hmeCs at a small number of repeat sequences such as GSAT_MM, of which the significant retention of bisulfite-resistant cytosines was corroborated by reanalysis of previously published whole-genome bisulfite sequencing data for intragonadal PGCs. PSCs harboring abnormal hypermethylation at ICRs of the Dlk1-Gtl2-Dio3 imprinting cluster diminished these 5meCs upon differentiation to PGCLCs, resulting in transcriptional reactivation of the Gtl2 gene. These observations support the usefulness of PGCLCs in studying the germline epigenetic erasure including imprinted genes, epimutations, and erasure-resistant loci, which may be involved in transgenerational epigenetic inheritance.

E2F1 controls germ cell apoptosis during the first wave of spermatogenesis

Cell cycle control during spermatogenesis is a highly complex process owing to the control of the mitotic expansion of the spermatogonial cell population and following meiosis, induction of DNA breaks during meiosis and the high levels of physiological germ-cell apoptosis. We set out to study how E2F1, a key controller of cell cycle, apoptosis, and DNA damage responses, functions in the developing and adult testis. We first analyzed the expression pattern of E2f1 during post-natal testis development using RNA in situ hybridization, which showed a differential expression pattern of E2f1 in the adult and juvenile mouse testes. To study the function of E2f1, we took advantage of the E2F1(-/-) mouse line, which was back-crossed to C57Bl/6J genetic background. E2f1 loss led to a severe progressive testicular atrophy beginning at the age of 20 days. Spermatogonial apoptosis during the first wave of spermatogenesis was decreased. However, already in the first wave of spermatogenesis an extensive apoptosis of spermatocytes was observed. In the adult E2F1(-/-) testes, the atrophy due to loss of spermatocytes was further exacerbated by loss of spermatogonial stem cells. Surprisingly, only subtle changes in global gene expression array profiling were observed in E2F1(-/-) testis at PND20. To dissect the changes in each testicular cell type, an additional comparative analysis of the array data was performed making use of previously published data on transcriptomes of the individual testicular cell types. Taken together, our data indicate that E2F1 has a differential role during first wave of spermatogenesis and in the adult testis, which emphasizes the complex nature of cell cycle control in the developing testis.

Expression patterns of taste receptor type 1 subunit 3 and α-gustducin in the mouse testis during development

Taste receptor type 1 subunit 3 (T1R3) and its associated heterotrimeric G protein α-gustducin (Gα) are involved in sweet and umami sensing in taste cells. They are also strongly expressed in the testis and sperm, but their expression patterns and potential roles involved were previously unknown. In present study, we investigated the expression patterns of T1R3 and Gα in the mouse testis at critical stages of postnatal life, and throughout the spermatogenic cycle. Our results indicated that T1R3 and Gα exhibited a stage-dependent expression pattern during mouse development, and a cell-specific pattern during the spermatogenic cycle. Their expressions have been increased significantly from prepubertal to pubertal periods (P<005), and decreased significantly in aged mice (P<005). The changes were mainly attributed to the differential expression of T1R3 or Gα in elongated spermatids and Leydig cells at different stages of the spermatogenic cycle. In addition, the expression of T1R3 and Gα were first observed in residual bodies of spermatozoa and endothelial cells of blood vessels at post-pubertal mice, while Gα was located in apoptotic spermatogonia of postnatal mice. These novel expression patterns suggest a role of T1R3 and Gα in the onset of spermatogenesis, pace of spermatogenic cycle, and aging of the testis.

Disruption of histone methylation in developing sperm impairs offspring health transgenerationally

A father's lifetime experiences can be transmitted to his offspring to affect health and development. However, the mechanisms underlying paternal epigenetic transmission are unclear. Unlike in somatic cells, there are few nucleosomes in sperm, and their function in epigenetic inheritance is unknown. We generated transgenic mice in which overexpression of the histone H3 lysine 4 (H3K4) demethylase KDM1A (also known as LSD1) during spermatogenesis reduced H3K4 dimethylation in sperm. KDM1A overexpression in one generation severely impaired development and survivability of offspring. These defects persisted transgenerationally in the absence of KDM1A germline expression and were associated with altered RNA profiles in sperm and offspring. We show that epigenetic inheritance of aberrant development can be initiated by histone demethylase activity in developing sperm, without changes to DNA methylation at CpG-rich regions.

Active vitamin D deficiency mediated by extracellular calcium and phosphorus results in male infertility in young mice

We used mice with targeted deletion of 25-hydroxyvitamin D-1 α-hydroxylase [1α(OH)ase(-/-)] to investigate whether 1,25(OH)2D3 deficiency results in male infertility mediated by 1,25(OH)2D3 or extracellular calcium and phosphorus. Male 1α(OH)ase(-/-) and their wild-type littermates fed either a normal diet or a rescue diet from weaning were mated at 6-14 wk of age with female wild-type mice on the same diet. The fertility efficiency of females was analyzed, and the reproductive phenotypes of males were evaluated by histopathological and molecular techniques. Hypocalcemic and hypophosphatemic male 1α(OH)ase(-/-) mice on a normal diet developed infertility characterized by hypergonadotropic hypogonadism, with downregulation of testicular calcium channels, lower intracellular calcium levels, decreased sperm count and motility, and histological abnormalities of the testes. The proliferation of spermatogenic cells was decreased with downregulation of cyclin E and CDK2 and upregulation of p53 and p21 expression, whereas apoptosis of spermatogenic cells was increased with upregulation of Bax and p-caspase 3 expression and downregulation of Bcl-xl expression. When serum calcium and phosphorus were normalized by the rescue diet, the defective reproductive phenotype in the male 1α(OH)ase(-/-) mice, including the hypergonadotropic hypogonadism, decreased sperm count and motility, histological abnormalities of testis, and defective spermatogenesis, was reversed. These results indicate that the infertility seen in male 1,25(OH)2D3-deficient mice is not a direct effect of active vitamin D deficiency on the reproductive system but is an indirect effect mediated by extracellular calcium and phosphorus.

A novel testis-enriched gene Spata33 is expressed during spermatogenesis

With an increasing incidence of male idiopathic infertility, identification of novel genes involved in spermatogenesis is an important aspect for the understanding of human testicular failure. In the present study, we have identified a novel gene Spata33, also called as 4732415M23Rik or C16orf55, which is conserved in mammalian species. Spata33 was predominantly expressed in the postpartum and adult mouse testes at mRNA and protein levels. Its expression was increased during the first wave of the spermatogenesis, indicating that Spata33 may be associated with the meiotic process. Further immunohistochemistry analysis revealed that Spata33 was mainly expressed in the spermatocytes, spermatogonia and round spermatids. Its expression was uniformly distributed in the nucleus and cytosol in these germ cells, which was further confirmed by Spata33-tagged with GFP staining in the GC-1 and TM4 cells. These results indicated that Spata33 was predominantly expressed in the mouse testis and associated with spermatogenesis. Identification and characterization of the novel testis-enriched gene Spata33 may provide a new route for understanding of spermatogenesis failure.

Effect of Ocimum basilicum extract on cadmium-induced testicular histomorphometric and immunohistochemical alterations in albino rats

The present study examined the efficacy of Ocimum basilicum (basil) extract, a natural herb, with antioxidant properties, against testicular toxicity induced by cadmium (Cd), which is one of the most important toxic heavy metals. The intoxicated rats showed significant alterations in the testicular tissue including decreased seminiferous epithelium height and changes in the arrangement of spermatogenic layers. Hypospermatogensis with cytoplasmic vacuolization and pyknotic nuclei were observed. Intertubular hemorrahage and absence of spermatozoa were noted. Decreased cell proliferation was reflected by a decrease in Ki-67 expression, whereas the increase in apoptotic rate was associated with a decrease in the Bcl/Bax ratio. Concomitant treatment with aqueous basil extract led to an improvement in histological, morphometrical and immunohistochemical changes induced by Cd. The beneficial effects of basil extract could be attributed to its antioxidant properties.

The apoptotic function analysis of p53, Apaf1, Caspase3 and Caspase7 during the spermatogenesis of the Chinese fire-bellied newt Cynops orientalis

BACKGROUND

Spontaneous and stress-induced germ cell apoptosis during spermatogenesis of multicellular organisms have been investigated broadly in mammals. Spermatogenetic process in urodele amphibians was essentially like that in mammals in spite of morphological differences; however, the mechanism of germ cell apoptosis in urodele amphibians remains unknown. The Chinese fire-belly newt, Cynops orientalis, was an excellent organism for studying germ cell apoptosis due to its sensitiveness to temperature, strong endurance of starvation, and sensitive skin to heavy metal exposure.

METHODOLOGY/PRINCIPAL FINDINGS

TUNEL result showed that spontaneous germ cell apoptosis took place in normal newt, and severe stress-induced apoptosis occurred to spermatids and sperm in response to heat shock (40°C 2 h), cold exposure (4°C 12 h), cadmium exposure (Cd 36 h), and starvation stress. Quantitative reverse transcription polymerase chain reactions (qRT-PCR) showed that gene expression of Caspase3 or Caspase7 was obviously elevated after stress treatment. Apaf1 was not altered at its gene expression level, and p53 was significantly decreased after various stress treatment. Caspase assay demonstrated that Caspase-3, -8, -9 enzyme activities in newt testis were significantly elevated after heat shock (40°C 2 h), cold exposure (4°C 12 h), and cadmium exposure (Cd 36 h), while Caspase3 and Caspase8 activities were increased with Caspase9 significantly decreased after starvation treatment.

CONCLUSIONS/SIGNIFICANCE

Severe germ cell apoptosis triggered by heat shock, cold exposure, and cadmium exposure was Caspase3 dependent, which probably involved both extrinsic and intrinsic pathways. Apaf1 may be involved in this process without elevating its gene expression. But starvation-induced germ cell apoptosis was likely mainly through extrinsic pathway. p53 was probably not responsible for stress-induced germ cell apoptosis in newt testis. The intriguing high occurrence of spermatid and sperm apoptosis probably resulted from the sperm morphology and unique reproduction policy of Chinese fire-belly newt, Cynops orientalis.

Inhaled hydrogen gas therapy for prevention of testicular ischemia/reperfusion injury in rats

PURPOSE

This study evaluated whether 2% hydrogen (H(2)) gas therapy protects against testicular ischemia/reperfusion injury which results in increased formation of reactive oxygen species and/or reactive nitrogen species, leading to testicular apoptosis and impaired spermatogenesis.

METHODS

Pubertal six-week-old Spraque-Dawley rats were assigned to 5 groups (10 animals/group) as follows: group A was a sham operated group; groups B, C, D, and E underwent 5 hours of left testicular ischemia followed by 0, 30, 60, and 120 minutes of 2% H(2) gas therapy, respectively. Histological analysis was performed to verify structure and morphology of the testes and to investigate Johnsen scores, mean seminiferous tubule diameter, and the number of germ cell layers to classify spermatogenesis. Germ cell apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay and Bax/Bcl-2 ratio real-time polymerase chain reaction. We also investigated malondialdehyde levels as an indicator of lipid peroxidation.

RESULTS

Compared to the sham group (A), germ cell apoptosis and lipid peroxidation in the ischemia group (B) were significantly increased with abnormal morphology and impaired spermatogenesis. In contrast, amelioration of testicular damages was evident in the H(2) therapy groups (C, D, and E).

CONCLUSIONS

Our results showed that inhalation of 2% H(2) gas may be a promising therapy with anti-apoptotic and anti-oxidant properties in cases of testicular ischemia/reperfusion injury.

MicroRNA-34c enhances murine male germ cell apoptosis through targeting ATF1

Background

MicroRNAs (miRNAs) play vital regulatory roles in many cellular processes. The expression of miRNA (miR)-34c is highly enriched in adult mouse testis, but its roles and underlying mechanisms of action are not well understood.

Methodology/Principal Findings

In the present study, we show that miR-34c is detected in mouse pachytene spermatocytes and continues to be highly expressed in spermatids. To explore the specific functions of miR-34c, we have established an in vivo model by transfecting miR-34c inhibitors into primary spermatocytes to study the loss-of-function of miR-34c. The results show that silencing of miR-34c significantly increases the Bcl-2/Bax ratio and prevents germ cell from apoptosis induced by deprivation of testosterone. Moreover, ectopic expression of the miR-34c in GC-2 cell trigger the cell apoptosis with a decreased Bcl-2/Bax ratio and miR-34c inhibition lead to a low spontaneous apoptotic ratio and an increased Bcl-2/Bax ratio. Furthermore, ectopic expression of miR-34c reduces ATF1 protein expression without affecting ATF1 mRNA level via directly binding to ATF1's 3′UTR, indicating that ATF1 is one of miR-34c's target genes. Meanwhile, the knockdown of ATF1 significantly decreases the Bcl-2/Bax ratio and triggers GC-2 cell apoptosis. Inhibition of miR-34c does not decrease the GC-2 cell apoptosis ratio in ATF1 knockdown cells.

Conclusions/Significance

Our study shows for the first time that miR-34c functions, at least partially, by targeting the ATF1 gene in germ cell apoptosis, providing a novel mechanism with involvement of miRNA in the regulation of germ cell apoptosis.

A novel marsupial pri-miRNA transcript has a putative role in gamete maintenance and defines a vertebrate miRNA cluster paralogous to the miR-15a/miR-16-1 cluster

Successful maintenance, survival and maturation of gametes rely on bidirectional communication between the gamete and its supporting cells. Before puberty, factors from the gamete and its supporting cells are necessary for spermatogonial stem cell and primordial follicle oocyte maintenance. Following gametogenesis, gametes rely on factors and nutrients secreted by cells of the reproductive tracts, the epididymis and/or oviduct, to complete maturation. Despite extensive studies on female and male reproduction, many of the molecular mechanisms of germ cell maintenance remain relatively unknown, particularly in marsupial species. We present the first study and characterisation of a novel primary miRNA transcript, pri-miR-16c, in the marsupial, the stripe-faced dunnart. Bioinformatic analysis showed that its predicted processed miRNA – miR-16c – is present in a wide range of vertebrates, but not eutherians. In situ hybridisation revealed dunnart pri-miR-16c expression in day 4 (primordial germ cells) and day 7 (oogonia) pouch young, in primary oocytes and follicle cells of primordial follicles but then only in follicle cells of primary, secondary and antral follicles in adult ovaries. In the adult testis, pri-miR-16c transcripts were present in the cytoplasm of spermatogonial cells. The oviduct and the epididymis both showed expression, but not any other somatic tissues examined or conceptuses during early embryonic development. This pattern of expression suggests that pri-miR-16c function may be associated with gamete maintenance, possibly through mechanisms involving RNA transfer, until the zygote enters the uterus at the pronuclear stage.

Proliferation and apoptosis in aged and photoregressed mammalian seminiferous epithelium, with particular attention to rodents and humans

Imbalances in the proliferation and apoptosis processes are involved in numerous epithelial alterations. In the seminiferous epithelium, normal spermatogenesis is regulated by spermatogonia proliferation and germ cell apoptosis, and both processes are involved in diverse pathological alterations of the seminiferous epithelium. Other physiological phenomena including aging and short photoperiod, in which apoptosis and proliferation seem to play important roles, cause testicular changes. Aging is accompanied by diminished proliferation and increased apoptosis, the latter occurring in specific states of the seminiferous cycle and considered the cause of epithelium involution. However, there is no clear evidence concerning whether proliferation decreases in the spermatogonia themselves or is due to an alteration in the cell microenvironment that surrounds them. As regards the factors that regulate the process, the data are scant, but it is considered that the diminution of c-kit expression in the spermatagonia, together with the diminution in antiapoptotic factors (Bcl-x(L))) of the intrinsic molecular pathway of apoptosis play a part in epithelial regression. A short photoperiod, especially in rodents, produces a gradual involution of the seminiferous epithelium, which is related with increased apoptosis during the regression phase and a diminution of apoptosis during recrudescence. Proliferative activity varies, especially during the total regression phase, when it usually increases in the undifferentiated spermatogonia. In other species showing seasonal reproduction, however, decreased proliferation is considered the main factor in the regression of the seminiferous epithelium. Little is known about how both phenomena are regulated, although data in rodents suggest that both the intrinsic and extrinsic pathways of apoptosis contribute to the increase in this process. In conclusion, regression of the seminiferous epithelium in physiological situations, as in many pathological situations, is a result of alterations in equilibrium between the proliferation and apoptosis of germinal cell types. However, both physiological phenomena showed important differences as regard proliferation/apoptosis and their regulation pathways, probably as a result of their irreversible or reversible character.

Reduced spermatogonial proliferation and decreased fertility in mice overexpressing cyclin E in spermatogonia

Cyclin E is a key component of the cell cycle regulatory machinery, contributing to the activation of Cdk2 and the control of cell cycle progression at several stages. Cyclin E expression is tightly regulated, by periodic transcription and ubiquitin-mediated degradation. Overexpression of cyclin E has been associated with tumor development and poor prognosis in several tumor types, including germ cell tumors and both cyclin E and its partner Cdk2 are required for normal spermatogenesis. Here we have generated and characterized transgenic mice overexpressing a cyclin E mutant protein, resistant to ubiquitin-mediated proteolysis, in testicular germ cells, under the control of the human EF-1alpha promoter. The transgenic mice develop normally and live a normal life span, with no signs of testicular tumor development. The transgenic mice display however reduced fertility and testicular atrophy, due to reduced spermatogonial proliferation as a consequence of deregulated cyclin E levels. Overall our results show that deregulation of cyclin E expression contribute to infertility, due to inability of the spermatogonial cells to start the mitotic cycles prior to entering meiosis.

Male germ cell apoptosis: regulation and biology

Cellular apoptosis appears to be a constant feature in the adult testis and during early development. This is essential because mammalian spermatogenesis is a complex process that requires precise homeostasis of different cell types. This review discusses the latest information available on male germ cell apoptosis induced by hormones, toxins and temperature in the context of the type of apoptotic pathway either the intrinsic or the extrinsic that may be used under a variety of stimuli. The review also discusses the importance of mechanisms pertaining to cellular apoptosis during testicular development, which is independent of exogenous stimuli. Since instances of germ cell carcinoma have increased over the past few decades, the current status of research on apoptotic pathways in teratocarcinoma cells is included. One other important aspect that is covered in this review is microRNA-mediated control of germ cell apoptosis, a field of research that is going to see intense activity in near future. Since knockout models of various kinds have been used to study many aspects of germ cell development, a comprehensive summary of literature on knockout mice used in reproduction studies is also provided.

BCL2 Ala43Thr is a functional variant associated with protection against azoospermia in a Han-Chinese population

Apoptosis is very common during various stages of mammalian germ cell development and differentiation, and the BCL2 gene is one of the most important apoptotic regulators. Although its genetic variants are reported to be involved in cancers and autoimmune diseases, little information is available regarding BCL2 polymorphisms in male spermatogenesis. In the present study, single nucleotide polymorphisms (SNPs) in coding regions of the BCL2 gene were examined in a hospital-based, case-control study including 198 infertile patients with idiopathic azoospermia and 183 fertile controls. Subsequently, a functional study was conducted for comparison of paclitaxel-induced cytotoxicity and apoptosis between the BCL2 variant and the wild type in vitro. Three SNPs were found in exon 2--A21G (rs1801018), G127A (rs1800477), and C300T (rs61733416)--with the latter first reported in the Han-Chinese population. The frequency of G127A (GA+AA) genotype was significantly lower in azoospermic, infertile men compared to the age-matched controls (P = 0.01). This genotype may confer a lower risk of azoospermia (adjusted odd ratio [OR] = 0.448, 95% confidence interval = 0.226-0.889). In addition, HeLa cells expressing the BCL2 Ala43Thr (G127A), similar to the control cells, were more sensitive to paclitaxel-induced cytotoxicity and apoptosis than those expressing wild-type BCL2. Consistently, the cleaved PARP and p-BCL2 proteins were subsequently increased after paclitaxel treatment, as also predicted by the bioinformatics analysis. Considering the decreased antiapoptotic function of BCL2, these results suggest that the Ala43Thr variant is associated with protection against azoospermia in the Han-Chinese population.

Apoptosis contributes to testicular toxicity induced by two isomers of bromopropanes

The aim of this study was to investigate the different testicular toxicity and the role of apoptosis in the possible mechanism induced by the two isomers of bromopropanes (BPs) in the same dosage. Following the 14-day treatment with a single dose of 1-BP and 2-BP (1 g/kg), male rats were killed and a series of experiments were performed. 1-BP and 2-BP both significantly decreased the epididymal sperm count, while only 2-BP induced an increase in sperms with abnormal heads. Morphological evaluation showed that 1-BP did not cause morphological changes in seminiferous epithelium, but 2-BP treatment resulted in the disappearance of spermatogonia, atrophy of the seminiferous tubules and degeneration of germ cells. 2-BP significantly increased the TUNEL-positive cells and the activation of caspase-3 and decreased the genes and proteins expression of Bax, Bcl-2 and p53. In contrast, there were no significant changes in the expression of apoptosis-related genes and proteins in 1-BP group, though the TUNEL-positive cells were significantly increased. Taken together, this study indicated that those two isomers both have toxicity in male rats, however, the testicular toxicity and the role of apoptosis in the toxic mechanism induced by 1-BP and 2-BP may be different.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

Long term testicular ischemia-reperfusion injury-induced apoptosis: involvement of survivin down-regulation

Testicular torsion is associated with damage to the testicular tissue as a result of ischemia-reperfusion injury (IRI) and induction of apoptosis leading to progressive damage to spermatogenesis. Survivin is suggested to be an important regulator in the control of the mitochondrial apoptotic pathway, although its role in torsion-induced IRI is unknown. Therefore, we sought to evaluate testicular survivin expression after long term IRI induced by testicular torsion. Survivin expression was measured by real-time PCR in 6-12 month old New Zealand white rabbits divided into three groups (4 animals/group): group (A) sham control, group (B) ischemia alone for 60 min and group (C) ischemia for 60 min followed by reperfusion for 6 months. Germ cell apoptosis was evaluated by TUNEL assay, Bax/Bcl-2 ratio and DNA fragmentation. The Johnsen score was used to assess testicular morphological damage, while lipid peroxidation was used as an indicator for oxidative stress. Survivin expression was detected in all testicular tissue samples. The rate of survivin expression after IRI was significantly higher (p<0.05) compared with ischemic only and sham control testes. Its expression in IRI samples was inversely correlated with the significant increase (p<0.05) in apoptosis, oxidative levels and spermatogenic damage. In conclusion, down-regulation of testicular survivin expression after long term IRI to the testis and its association with apoptosis induction suggests its involvement in the regulation of this apoptotic pathway. These findings also identify survivin as a potential new target for the prevention of germ cell death during testicular torsion.

A critical role of PUMA in maintenance of genomic integrity of murine spermatogonial stem cell precursors after genotoxic stress

Neonatal gonocytes are precursors of spermatogonial stem cells. Preserving their integrity by elimination of damaged germ cells may be crucial to avoid the transmission of genetic alterations to progeny. Using gamma-irradiation, we investigated by immunohistochemistry, flow cytometry and real-time PCR components of the death machinery in neonatal gonocytes. Their death was correlated with caspase 3 activation but not with AIF translocation into the nucleus. The in vivo contribution of both the extrinsic and the intrinsic pathways was then investigated. We focused on the roles of TRAIL/Death Receptor 5 (DR5) and PUMA. Our results were validated using knockout mice. Whereas DR5 expression was upregulated at the cell surface after radiation, caspase 8 was not activated. However, we detected caspase 9 cleavage associated with cytochrome c release. In mice deficient for PUMA, radiation-induced gonocyte apoptosis was reduced, whereas invalidation of TRAIL had no effect. Overall, our results show that genotoxic stress-induced apoptosis of gonocytes is caspase-dependent and involves almost exclusively the intrinsic pathway. Furthermore, PUMA plays a critical role in the maintenance of genomic integrity of spermatogonial stem cell precursors.

Constitutive WNT/beta-catenin signaling in murine Sertoli cells disrupts their differentiation and ability to support spermatogenesis

Sertoli and germ cell interactions are essential for spermatogenesis and, thus, male fertility. Sertoli cells provide a specialized microenvironment for spermatogonial stem cells to divide, allowing both self-renewal and spermatogenesis. In the present study, we used mice with a conditional activated allele of the beta-catenin gene (Ctnnb1(tm1Mmt)(/+)) in Sertoli cells expressing Cre recombinase driven by the anti-Müllerian hormone (AMH; also known as Müllerian-inhibiting substance) type II receptor promoter (Amhr2(tm3(cre)Bhr)(/+)) to show that constitutively activated beta-catenin leads to their continuous proliferation and compromised differentiation. Compared to controls, Sertoli cells in mature mutant mice continue to express high levels of both AMH and glial cell-derived neurotrophic factor (GDNF), which normally are expressed only in immature Sertoli cells. We also show evidence that LiCl treatment, which activates endogenous nuclear beta-catenin activity, regulates both AMH and GDNF expression at the transcriptional level. The epididymides were devoid of sperm in the Amhr2(tm3(cre)Bhr)(/+);Ctnnb1(tm1Mmt)(/+) mice at all ages examined. We show that the mutant mice are infertile because of defective differentiation of germ cells and increased apoptosis, both of which are characteristic of GDNF overexpression in Sertoli cells. Constitutive activation of beta-catenin in Amhr2-null mice showed the same histology, suggesting that the phenotype was the result of persistent overexpression of GDNF. These results show that dysregulated wingless-related MMTV integration site/beta-catenin signaling in Sertoli cells inhibits their postnatal differentiation, resulting in increased germ cell apoptosis and infertility.

The role of MAPK and FAS death receptor pathways in testicular germ cell apoptosis induced by lead

The aim of the present study is to investigate gene expression involved in the signal pathway of MAPK and death signal receptor pathway of FAS in lead-induced apoptosis of testicular germ cells. First, cell viabilities were determined by MTT assay. Second, using single cell gel-electrophoresis test (comet assay) and TUNEL staining technique, apoptotic rate and cell apoptosis localization of testicular germ cells were measured in mice treated with 0.15%, 0.3%, and 0.6% lead, respectively. Third, the immunolocalization of K-ras, c-fos, Fas, and active caspase-3 proteins was determined by immunohistochemistry. Finally, changes in the translational levels of K-ras, c-fos, Fas, and active caspase-3 were further detected by western blot analysis. Our results showed that lead could significantly induce testicular germ cell apoptosis in a dose-dependent manner (P<0.01). The mechanisms were closely related to the increased expressions of K-ras, c-fos, Fas, and active caspase-3 in apoptotic germ cells. In conclusion, K-ras/c-fos and Fas/caspase-3 death signaling receptor pathways were involved in the lead-induced apoptosis of the testicular germ cells in mice.

EXPRESSION OF BCL-2 AND BAX IN RHESUS MONKEY TESTIS DURING GERM CELL APOPTOSIS INDUCED BY TESTOSTERONE UNDECANOATE

Apoptosis occurs spontaneously during spermatogenesis and can be induced by androgen withdrawal. However, the molecular events governing apoptosis have not been characterized. To study the molecular mechanism of apoptosis induced by a high dose of testosterone undecanoate (TU), the authors examined the temporal changes in proapoptotic Bax and antiapoptotic Bcl-2 in TU-treated monkey testes. Apoptotic cells were identified in tissue sections by in situ end labeling of fragmented DNA. The results showed that a great deal of the apoptotic cells occurred in the testes on day 30 after TU injection and that the dominant apoptotic germ cells are spermatocytes and spermatids. The expression of Bcl-2 and Bax was assessed by immunohistochemical method and Western blot. As compared with that of normal testes, the levels of Bcl-2 protein increased significantly from 7 to day 14 while that of Bax protein was almost unchanged in the testes from day 7 up to day 60 after TU treatment. Bcl-2 was localized to the spermatids in the normal testes and temporarily distributed in both the cytoplasm and nucleus of those cell types susceptible to TU-induced apoptosis on day 14 after TU injection. Therefore, it is suggested that Bax may not play a role in initiating germ cell apoptosis induced by TU injection and that the evaluation in Bcl-2 expression may represent a survival mechanism for the remaining germ cell.

The presence of abnormal spermatozoa in the ejaculate: Did apoptosis fail?

With the successful use of Assisted Reproduction, in particular intracytoplasmic sperm injection (ICSI), to treat infertile couples we have become less discriminating with the quality of spermatozoa we use to treat our patients. Numerous studies have shown the presence of nuclear DNA strand breaks in human ejaculated spermatozoa. The reason why human spermatozoa, in particular from men with abnormal semen parameters, possess these abnormalities in their nuclear DNA is still not clear. Two processes that have been linked to the presence of nuclear DNA strand breaks in spermatozoa are anomalies in apoptosis during spermatogenesis or problems in the packaging of the chromatin during spermiogenesis. Understanding the mechanisms responsible for producing abnormal spermatozoa in the human will improve our knowledge about certain causes of male infertility. More importantly, the impact of such sperm, if selected to perform ICSI, needs to be better understood so that any detrimental paternal effects can be avoided.