Arrest Of Spermatogenesis Research Articles

Localisation cellulaire de la sécrétion de l’inhibine B testiculaire

Inhibin B is a testicular peptide hormone that regulates FSH secretion in a negative feedback loop. Inhibin B is a dimer of an α and βB subunit. In adult testis, the cellular site of production of these subunits is still controversial: Leydig cells, Sertoli cells and/or germ cells. The immunohistological localization (monoclonal antibodies anti α and anti βB) of both sub-units and the expression patterns of their mRNA (in situ hybridization with RNA probes) were examined in adult testicular biopsies with normal spermatogenesis or spermatogenetic arrest. In all testes, Sertoli cells and Leydig cells showed positive immunostaining for inhibin α subunit and expressed inhibin α subunit mRNA. Conversely, germ cells expressed the βB peptide (located from pachytene spermatocytes to round spermatids) and the βB subunit mRNA (located from spermatogonia to round spermatids). These results agree with the recent opinion that inhibin B is possibly a joint product of Sertoli cells and germ cells in adult men and it may be used as a serum marker of spermatogenesis.

Gossypol: a contraceptive for men

Gossypol is a polyphenol isolated from the seed, roots, and stem of the cotton plant ( Gossypium sp.). The substance, a yellow pigment similar to flavonoids, is present in cottonseed oil. In the plant, it acts as a natural defensive agent against predators, provoking infertility in insects. In most animals, gossypol provokes infertility, and in man it causes spermatogenesis arrest at relatively low doses. Studies carried out in China, Africa, and Brazil have shown that the substance is well tolerated, causing no side effects that lead to discontinuation. The reported hypokalemia of early studies has not been confirmed in the latest trials. The only concern at present appears to be lack of reversibility in over 20% of subjects. Gossypol should be prescribed preferably to men who have completed their families or for those who would accept permanent infertility after a few years of use.

Expression of P16 INK4a in testis of rhesus monkey during heat stress and testosterone undecanoate induced azoospermia or oligozoospermia☆

Previous studies on azoospermia or oligozoospermia induced by heat stress or high doses of testosterone mainly focused on germ cell apoptosis; no data regarding their possible effect on spermatogonia mitosis are available. We have established unilateral cryptorchid and testosterone undecanoate (TU)-treated monkey models and examined expression of P16 INK4a in the testis to look at its possible role in azoospermia or oligozoospermia induced by the heat stress or the TU treatment. The results showed that both heat stress and TU were capable of inducing expression of P16 INK4a mainly in spermatogonia and other types of germ cells as well as Sertoli cells at the later stage of germ cell apoptosis, namely on Day 10 after operation or on Day 60 after TU injection. It is, therefore, suggested for the first time that P16 INK4a protein may inhibit the spermatogonia mitosis in the testis at the later stage of the germ cell apoptosis, resulting in arrest of spermatogenesis.

Fas expression correlates with human germ cell degeneration in meiotic and post-meiotic arrest of spermatogenesis.

Degeneration of human male germ cells was analysed by means of light (LM) and transmission electron (TEM) microscopy. The frequency of degenerating cells was correlated with that of Fas-expressing germ cells in human testes with normal spermatogenesis (n = 10), complete early maturation arrest (EMA) (n = 10) or incomplete late maturation arrest (LMA; n = 10) of spermatogenesis. LM analysis of testis sections with normal spermatogenesis indicated that degenerating germ cells were localized in the adluminal compartment of the seminiferous epithelium. TEM showed that apoptotic cells were mostly primary spermatocytes and, to a lesser extent, round or early elongating spermatids. Apoptotic germ cells appeared to be eliminated either in the seminiferous lumen or by Sertoli cell phagocytosis. An increased number of degenerating cells was observed in testes with LMA as compared with normal testes and testes with EMA of spermatogenesis (P < 0.001, Wilcoxon's rank sum test). Comparison of these results with those obtained from immunohistochemistry experiments demonstrated a tight correlation between the number of apoptotic cells and the number of Fas-expressing germ cells (P = 0.001, Spearman's rank = 0.69). These findings suggest that altered meiotic and post-meiotic germ cell maturation might be associated with an up-regulation of Fas gene expression capable of triggering apoptotic elimination of defective germ cells.

Transgene insertion induced dominant male sterility and rescue of male fertility using round spermatid injection.

Transgene insertions in the mouse often cause mutations at chromosomal loci. Analysis of insertion mutations that cause male sterility may lead to the identification of novel molecular mechanisms implicated in male fertility. Here we show a line of transgenic mice with dominant inheritance of male sterility (DMS) that was found amid several lines that were normally fertile. Transgene-positive males from this line invariably were sterile, whereas transgenic females and transgene-negative male littermates were fertile. Histologic analysis and TUNEL staining for apoptotic cells in DMS testis showed spermatogenesis arrest at metaphase of meiosis I (M-I), accompanied by massive apoptosis of spermatocytes. Meiosis I arrest was incomplete, however, as small numbers of spermatids and spermatozoa were found. Both round spermatids and spermatozoa were evaluated for their permissiveness in the assisted reproductive technologies intracytoplasmic sperm injection (ICSI) and round spermatid injection (ROSI). Surprisingly, ROSI but not ICSI gave live offspring, suggesting that mature sperm had deteriorated by the time of recovery from the epididymis. Mapping the transgene insertion by fluorescence in situ hybridization revealed a site on chromosome 14 D3-E1. Two candidate genes, GFR alpha 2 and GnRH, that were previously mapped to that region and the functions of which in spermatogenesis are well established were not altered in DMS. As a consequence, positional cloning of the DMS locus will be essential to identify new molecules potentially involved in arrest at M-I. Furthermore, mice carrying this genetic trait might be useful for studies of assisted reproductive technologies and male contraceptives.

NYD-SP6, a Novel Gene Potentially Involved in Regulating Testicular Development/Spermatogenesis

Using cDNA microarray hybridization from a human testicular cDNA library, a novel gene exhibiting 30-fold difference in expression level between adult and embryo human testes was cloned and named NYD-SP6, which was 1858 bp in length with 87% nucleotide identity with the mouse homologue sequence. The deduced protein structure of NYD-SP6 was found to contain two plant homeodomain (PHD) finger domains, believed to be involved in activating transcriptional regulation. Tissue distribution analysis using Northern blot indicated that the NYD-SP6 gene was expressed in a wide range of tissues, with a high expression level in the testis. Its expression in human and mouse testes by in situ hybridization was confined to Sertoli cells and the expression was developmentally regulated as demonstrated by cDNA microarray, in situ hybridization, and semiquantitative PCR in mouse testes. GFP/NYD-SP6 protein was predominantly localized in the nucleus of the transfected CHO cells, indicating its role in transcriptional regulation. In contrast, the N-terminal truncated NYD-SP6 (tNYD-SP6) localized in the nuclear envelope, indicating this region function as a nuclear localization signal. Further Northern blot analysis of gene expression in patients with spermatogenesis arrest revealed that NYD-SP6 was absent in one patient whose spermatogenesis was blocked at the stage of spermatocytes. Taken together, these results suggest that the putative protein of NYD-SP6 may play an important role in stimulating transcription involved in testicular development and/or spermatogenesis.

The effect of crude extract of the bark of Carica papaya on the seminiferous tubules of male Sprague-Dawley rats

The contraceptive potential of an aqueous crude extract of the bark of Carica papaya administered orally is reported at the dose regime of 5 and 10 ml/animal/day for 4 weeks. Although the body weight or the weights of reproductive organs, kidneys, adrenals remained unaltered during the course of treatment, there was significant alteration in the histology of the testis and semen analysis when compared to the intact control group. The seminiferous tubules of rats treated with low doses of Carica papaya for 4 weeks showed no significant histological changes compared with the control. At the high dose concentration of the extract there was disorganisation in some of the seminiferous tubules with arrest of spermatogenesis beyond the level of spermatocytes. There was also widening of the lumen of the tubules. Seminal analysis showed some of the motile spermatozoa with abnormal feature in all the experimental groups. There was a dose-dependent suppression of sperm progressive forward motility which coincided with a decrease in sperm count, viability and a dose-dependent increase in percentage abnormal spermatozoa during the 14-28 days experimental period. Taken together, the present experiment showed that complete loss of fertility is attributed to decline in sperm motility and alteration in their morphology and suggest that the aqueous extracts of Carica papaya bark is safe and could serve as an effective male contraceptive in animals.

Probability of sperm detection in nonobstructive azoospermic men undergoing testicular sperm extraction procedures unrelated to clinical parameters.

The study was conducted to evaluate the significance of preoperative clinical parameters for detection of mature testicular sperm cells in nonobstructive azoospermic men. Sixty-five consecutive men with nonobstructive azoospermia underwent testicular sperm extraction procedures. Testicular samples were analyzed histologically with patterns classified as mature spermatogenesis (normal or partial), arrest of spermatogenesis, and Sertoli cell only. Testicular sperm cells were isolated for use in an IVF/ICSI program. Histologic patterns and detection rate of sperm cells were correlated to clinical characteristics. Mature sperm cells were found in all levels of serum FSH. The men were divided into 3 groups based on their clinical characteristics (serum FSH level and testicular size). The distribution of the different testicular histologic patterns, as well as detection rate of sperm cells, was similar in all groups. No correlation was found between serum levels of FSH, LH, prolactin, or testosterone and sperm presence. None of these parameters, nor the testicular size and consistency, can serve as predictive variables of the histological pattern or the presence of mature sperm cells in the testicular biopsies in cases of nonobstructive azoospermia. Until an effective predictive tool is available, a trial of sperm retrieval is recommended for all azoospermic men independent of their clinical characteristics.

Cloning and characterization of temperature-related gene TRS1.

To investigate the mechanism of spermatogenesis arrest derived from heat treatment and to screen temperature-related genes involved in spermatogenesis, the authors analyzed the differences in gene expression between cryptorchid and scrotal testes in rats, and cloned a full-length cDNA named TRS1. In situ hybridization showed that TRS1 mRNA was mainly expressed in spermatocyte and round spermatids in testis. The expression level decreased in cryptorchid testis, suggesting that the lower scrotal temperature is a key factor in keeping the normal expression of TRS1. At the N-terminal of TRS1, there was a plecstrin homology (PH) domain signature. This PH domain has high similarity to that in PEPP2, a homosapien protein, which has a characteristic of binding phosphatidylinositol 3-phosphate via its PH domain in vitro. These findings suggest that TRS1 may be important in spermatogenesis and give clues for further research on the function of TRS1.

Touch Imprint Cytology in Biopsy of the Infertile Testis

To identify different cell types in the testis by using touch imprint cytology and to compare the cytologic findings to the histopathologic diagnosis in infertile men. This prospective study used touch imprint preparations and included 20 infertile men. The biopsy material obtained was stained with toluidine blue, May-Grünwald-Giemsa stain and Papanicolaou stain. The cytologic results for oligospermic, normospermic and azospermic men were compared to the specific histopathologic diagnosis. The proportion of spermatogenic versus Sertoli cells was calculated. The scores were compared between three groups based on the results of the histologic biopsy: normal spermatogenesis, hypospermatogenesis and incomplete spermatogenic arrest. The mean ratio of the spermatogenic cells versus Sertoli cells was statistically significantly different in the three groups (P < .01). The mean ratio of spermatogenic cells to Sertoli cells was higher in cases with normal spermatogenesis than in cases with hypospermatogenesis and incomplete spermatogenic arrest, revealing a statistical difference (P<.01). This ratio was not statistically significantly different between the hypospermatogenesis and incomplete spermatogenic arrest groups. A cytologic demonstration of germinal cells by using touch imprint preparations may be a guide for histologic diagnosis.

BCLW Mediates Survival of Postmitotic Sertoli Cells by Regulating BAX Activity

Male mice deficient in BCLW, a death-protecting member of the BCL2 family, are sterile due to an arrest in spermatogenesis that is associated with a gradual loss of germ cells and Sertoli cells from the testis. As Bclw is expressed in both Sertoli cells and diploid male germ cells, it has been unclear which of these cell types requires BCLW in a cell-autonomous manner for survival. To determine whether death of Sertoli cells in Bclw mutants is influenced by the protracted loss of germ cells, we examined testes from Bclw/c-kit double mutant mice, which lack germ cells from birth. Loss of BCLW-deficient Sertoli cells occurs in the absence of germ cells, indicating that germ cell death is not required to mediate loss of Sertoli cells in BCLW-deficient mice. This suggests that Sertoli cells require BCLW in a cell-intrinsic manner for long-term survival. The loss of Sertoli cells in Bclw mutants commences shortly after Sertoli cells have become postmitotic. In situ hybridization analysis indicates that Bclw is expressed in Sertoli cells both before and after exit from mitosis. Therefore, Bclw-independent pathways promote the survival of undifferentiated, mitotic Sertoli cells. We show that BAX and BAK, two closely related death-promoting members of the BCL2 family, are expressed in Sertoli cells. To determine whether either BAX or BAK activity is required for Sertoli cell death in Bclw mutant animals, we analyzed survival of Sertoli cells in Bclw/Bax and Bclw/Bak double homozygous mutant mice. While mutation of Bak had no effect, ablation of Bax suppressed the loss of Sertoli cells in Bclw mutants. Thus, BCLW mediates survival of postmitotic Sertoli cells in the mouse by suppressing death-promoting activity of BAX.

Expression patterns and transcript concentrations of the autosomal DAZL gene in testes of azoospermic men.

The DAZ (Deleted in AZoospermia) gene cluster on the Y chromosome is a strong candidate for the azoospermia factor. The DAZ gene was derived from an autosomal homologue, DAZL (DAZ-Like). This study was designed to assess the functional role of DAZL in human spermatogenesis. The expression patterns and mRNA transcript levels of DAZL in the testes of 17 azoospermic men were therefore examined by immunohistochemical staining and quantitative competitive reverse transcription-polymerase chain reaction. DAZL protein was expressed in the cytoplasm of primary spermatocytes and weakly in spermatogonia. It was detected in the testicular tissues of all subjects with germ cells present. The copy number of the DAZL transcript in normal spermatogenesis (n = 4), hypospermatogenesis or maturation arrest (n = 6), and Sertoli cell-only syndrome (n = 7) ranged from 1.22 x 10(6) to 1.63 x 10(6) per ng of RNA, 1.19 x 10(5) to 2.82 x 10(5) per ng of RNA and 2.83 x 10(4) to 1.23 x 10(5) per ng of RNA respectively. DAZL transcripts were lower in men with spermatogenic failure, and a significant difference was found between the three groups (P < 0.0001). This study suggests that DAZL may play an important role in the human spermatogenic processes of both mitosis and meiosis.

Influence of lead and zinc on rat male reproduction at 'biochemical and histopathological levels'.

Sequential lead accumulation and biochemical and histopathological changes were observed in rat testis and epididymis after oral administration at varied doses of lead (10, 50 and 200 mg kg(-1) body wt.) for 3 months and also following the concomitant administration of lead with zinc (1 mg kg(-1) body wt. +50 mg Pb kg(-1) body wt.). Accumulation of lead in both testis and epididymis increased with dose. The concomitant administration of zinc reduced the lead levels. Similarly, dose-related changes were seen in the activities of the enzymes alkaline phosphatase and Na(+)-K(+)-ATPase, which decreased with increased dose of lead. A significant improvement in the activities of these enzymes was seen in the groups given both lead and zinc. Histologically, discernible changes were noticed only at higher doses (50 and 200 mg kg(-1) body wt.), which included disorganization and disruption of spermatogenesis with accumulation of immature cells in lumen of tubule. At higher doses of lead, complete arrest of spermatogenesis was seen and a significant decrease in germ cell layer population was evident. Even in epididymis, the histoarchitecture was disrupted only at higher doses of lead both in the caput and corpus regions. The changes included damage of basement membrane, disorganization of epithelium and vacuolization of cells. The tubules were found almost empty, indicating arrest of spermatogenesis. However, with concomitant administration of lead and zinc both testis and epididymis presented a near-normal picture, indicating the protective role of zinc. Hence, the data indicate that the protective effect of zinc on lead toxicity was mediated largely by significant competition between lead and zinc or due to reduction of the available binding sites.

Antispermatogenic Effects of an Ethanol Extract of Citrullus colocynthis Root in Male Albino Rats

A crude 50% ethanol extract of Citrullus colocynthis Schrad roots was administered orally to male albino rats at dose levels of 50, 100 and 200 mg/kg b.wt./day for a period of 60 days for evaluation of antifertility effects. Significant decreases in cauda epididymal sperm motility, density, number of pups and fertility were observed in all treatment groups. A marked reduction in the weight of testes, epididymis and seminal vesicle was observed. The weight of the ventral prostate was nonsignificantly decreased. The histoarchitecture of testis revealed degenerative changes in the seminiferous epithelium, arrest of spermatogenesis at the stage of round spermatid, cytolysis and lumen filled with eosinophilic material. Seminiferous tubule diameter and Leydig cell nuclear diameter were decreased. A marked alteration in the Leydig cell differential counts was also noticed. The Sertoli cell nuclear diameter was unchanged. The concentration of cholesterol in testis, fructose in seminal vesicle and protein and sialic acid in all reproductive sex organs were depleted. Serum testosterone levels were markedly decreased in all treatment groups. In conclusion, a 50% ethanol extract of C. colocynthis roots produced antifertility activity in male albino rats.

The contribution of RNA-binding motif (RBM) antibody to the histopathologic evaluation of testicular biopsies from infertile men

Testicular biopsies of infertile men are often characterized by mixed histologic patterns, with different types of spermatogenic impairments being found in adjacent seminiferous tubules. RNA-binding motif (RBM) is a nuclear protein expressed exclusively in the male germ cell line. We reasoned that RBM might be a useful marker to identify germ cells in testicular sections, particularly in biopsies with mixed histologic phenotype and small focal concentrations of spermatogenesis. Testicular biopsies from azoospermic men were immunohistochemically evaluated for RBM expression. RBM expression was detectable in spermatogonia, spermatocytes, and round spermatids in biopsies of men with obstructive azoospermia and normal spermatogenesis. No specific cell staining was shown in cases of Sertoli-cell-only (SCO) syndrome. In biopsies of patients with spermatogenic disorders, all the germ cells were stained up to and including the stage level of the arrest in spermatogenesis. This approach enabled identification of small focal concentrations of spermatogenesis in a biopsy previously classified as being SCO by hematoxylin and eosin staining. Thus, RBM can be a useful immunohistochemical marker for the specific identification of germ cells and provide greater accuracy in the histopathologic evaluation of testicular biopsies. HUM PATHOL 32:36-41. Copyright © 2001 by W.B. Saunders Company

Novel cyclic adenosine 3',5'-monophosphate (cAMP) response element modulator theta isoforms expressed by two newly identified cAMP-responsive promoters active in the testis.

cAMP signaling contributes to the control of the developmental progression of germ cells during the spermatogenic cycle. Genes regulated by cAMP include those encoding transcription factors such as the cAMP-responsive element modulator (CREM). The disruption of CREM gene expression in crem null mice results in arrest of spermatogenesis and infertility. The transcriptional control of the CREM gene is attributed to two promoters, P1 and P2. The P1 promoter constitutively activates the synthesis of messenger RNAs encoding activator (tau) and repressor (alpha) forms of CREM, whereas the cAMP-responsive P2 promoter activates the formation of messenger RNAs encoding the inducible cAMP early repressor. Here we report the identification of two additional promoters in the CREM gene, P3 and P4, that in the rat testis encode two novel transcriptional activator CREM isoforms, termed CREM theta1 and CREM theta2, respectively. Notably, the P3 and P4 promoters are activated by cAMP-dependent protein kinase, thereby providing cAMP-regulated transcription of CREM activators in addition to the established cAMP-regulated inducible cAMP early repressor. Analysis ex vivo of CREM gene expression in temporally staged segments of the seminiferous tubule during the spermatogenic cycle shows that the activities of the P1, P3, and P4 promoters are independently regulated. Our identification of the cAMP-activated P3 and P4 promoters that direct expression of the novel theta1 and theta2 activator isoforms of CREM brings further insight into the complex expression of the CREM gene during germ cell development and may have implications in understanding the control of fertility.

Aspects of the male reproductive toxicity/male antifertility property of andrographolide in albino rats: effect on the testis and the cauda epididymidal spermatozoa

Previous work has shown that Andrographis paniculata leaf, when fed to male albino rats, causes the arrest of spermatogenesis. The present study was undertaken to investigate whether andrographolide, one of the major constituents of this plant, is responsible for such an effect. The compound was administered to 3-month-old male Wistar albino rats at two dose levels, for 48 days. Fertility tests, analysis of the counts, motility and abnormalities of the cauda epididymidal spermatozoa, and histopathological­evaluation of the testis were carried out. The results showed that sperm counts decreased, the spermatozoa were not motile, and several of them possessed abnormalities. The seminiferous epithelium was­thoroughly disrupted and in the seminiferous tubules, fully differentiated spermatozoa were far too limited; cells in the divisional stages were prevalent; multinucleate giant cells were abundant and Leydig cells appeared intact. It is inferred that andrographolide could affect spermatogenesis by preventing cytokinesis of the dividing spermatogenic cell lines. The multinucleate giant cells are comparable to the symplasts generated by cytochalasin-D and ursolic acid due to action at stages V–VII of the spermatogenic cycle. Sertoli cell damage and spermatotoxic effects are also apparent. Thus, the study points to a male reproductive toxic effect of this compound when used as a therapeutic; the study also confirms the possible prospective use of andrographolide in male contraception. Copyright © 2000 John Wiley & Sons, Ltd.

Oestrogens in male reproduction

The role of oestrogens in male reproductive physiology is rapidly being redefined. While cases of oestrogen deficiency or insensitivity are rare among humans, insights are being gained from the development of mouse models in which oestrogen action has been abolished. Four knockout mouse models are currently available. The three oestrogen receptor knockout models-the oestrogen receptor-alpha (alphaERKO), -beta (betaERKO) and -alphabeta (alphabetaERKO) double knockout mice-are providing valuable information on the loss of action of oestrogen receptors and the way in which either or both isoforms of the receptor are employed in any given action. On the other hand, the generation of the aromatase knockout (ArKO) mouse has produced animals unable to synthesize endogenous oestrogen. Fundamental perturbations that affect male fertility in these models include a disruption of testis morphology, an arrest of spermatogenesis at the stage of early spermiogenesis, a reduction in sperm concentration, motility and the ability to fertilize, severe dilatation of the efferent ductules and significant alterations to the normal hormone profile. The continuing accumulation of evidence from these animal models demonstrates that oestrogen plays an essential and direct role in the development and maintenance of male fertility.

Quantitative FISH Analysis of Testicular Cell in Azoospermic Patients: Diagnosis and Prognosis Value

Objectives: To evaluate in cases of spermatogenesis anomalies 1) the FISH reliability for the diagnosis of the stages of spermatogenesis arrest, 2) the functional character of the Sertoli cells 3) the rate of aneuploidy in post meiotic germ cells.

Maturation phenotype of Sertoli cells in testicular biopsies of azoospermic men.

The involvement of Sertoli cells in different spermatogenic impairments has been studied by an immunohistomorphometric technique using cytokeratin-18 (CK-18) as a marker for immature Sertoli cells. CK-18 is known to be expressed in Sertoli cells during prenatal and prepubertal differentiation and is normally lost at puberty. Forty-nine azoospermic men were included in the current study. Quantitative measurements on testicular biopsies revealed the highest CK-18 expression in the mixed atrophy biopsies (22 men), a lower expression in the Sertoli cell-only (SCO) biopsies (12 men), and minimal residual staining in the group considered as representing normal spermatogenesis (six obstructive azoospermia patients). The cytokeratin immunopositive-stained tubules were associated either with arrest in spermatogenesis or with SCO. Examination of sections from nine men with microdeletions in the AZF region of the Y chromosome revealed that these men were either negative for CK-18 expression or showed only weak residual staining. This may suggest that the spermatogenic defect in the AZF-deleted men originates in the germ cell and has no impact on Sertoli cell maturation. The cause that determined the spermatogenic defect in the other cases of male infertility with high CK-18 expression may have damaged both the Sertoli and the germ cells.