Expression of the apoptosis inhibitor survivin in testicular tissue of infertile patients

Seminal plasma biomarkers for predicting successful sperm retrieval in patients with nonobstructive azoospermia: a narrative review of human studies

BACKGROUND

Non-obstructive azoospermia (NOA) is considered to be the most severe form of male infertility. Before the emergence of surgical testicular sperm extraction and assisted reproductive technology, NOA patients could hardly become biological fathers of their children. However, failure of the surgery could cause physical and psychological harm to patients such as testicular damage, pain, hopeless of fertility and additional cost. Therefore, predicting the successful sperm retrieval (SSR) is so important for NOA patients to make their choice whether to do the surgery or not. Because seminal plasma is secreted by the testes and accessory gonads, it can reflect the spermatogenic environment, making it a preferential choice for SSR valuation. The purpose of this paper is to summarize the available evidence and provide the reader with a broad overview of biomarkers in seminal plasma for SSR prediction.

RESULTS

A total of 15,390 studies were searched from PUBMED, EMBASE, CENTRAL and Web of Science, but only 6615 studies were evaluated after duplications were removed. The abstracts of 6513 articles were excluded because they were irrelevant to the topic. The full texts of 102 articles were obtained, with 21 of them being included in this review. The included studies range in quality from medium to high. In the included articles, surgical sperm extraction methods included conventional testicular sperm extraction (TESE) and microdissection testicular sperm extraction (micro-TESE). Currently, the biomarkers in seminal plasma used to predict SSR are primarily RNAs, metabolites, AMH, inhibin B, leptin, survivin, clusterin, LGALS3BP, ESX1, TEX101, TNP1, DAZ, PRM1 and PRM2.

CONCLUSION

The evidence does not conclusively indicate that AMH and INHB in seminal plasma are valuable to predict the SSR. It is worth noting that RNAs, metabolites and other biomarkers in seminal plasma have shown great potential in predicting SSR. However, existing evidence is insufficient to provide clinicians with adequate decision support, and more prospective, large sample size, and multicenter trials are urgently needed.

Moringa oleifera ethanolic extract ameliorates the testicular dysfunction resulted from HFD-induced obesity rat model

In this study, we estimated the protective role of Moringa oleifera leaf ethanolic extract (MOLE) against obesity-associated testicular dysfunction. Fifty male albino rats were randomly assigned to five groups (n = 10): Group I (basal diet), group II (basal diet plus MOLE orally), group III (high-fat diet-HFD), group IV (HFD plus oral MOLE) and group V (HFD for 8 weeks followed by a basal diet plus oral MOLE for 6 weeks). The study duration extended for 14 weeks. Serum collected to investigate testosterone, FSH and LH levels. Testicular tissues were used to determine levels of SOD, glutathione, catalase and malondialdehyde. Semen was collected to estimate its quality (morphology, motility and concentration). Morphological changes in the testis were investigated by histopathological and immunohistochemical techniques. Compared with both control treatment and MOLE treatment, serum testosterone, FSH, LH, testicular enzymatic catalase, SOD, GSH, survivin immunoreactivity, sperm quality and testicular weight were all significantly decreased in rats treated with HFD, while there were significant increases in testicular malondialdehyde and caspase-3 immunoreactivity. MOLE improved all harmful effects of HFD. Improvements were more pronounced in the protected (G 4) than the treated (G 5) group. MOLE could be a potential solution for obesity-associated fertility problem.

Inhibition of NADPH oxidase alleviates germ cell apoptosis and ER stress during testicular ischemia reperfusion injury

Testicular torsion and detorsion (TTD) is a serious urological condition affecting young males that is underlined by an ischemia reperfusion injury (tIRI) to the testis as the pathophysiological mechanism. During tIRI, uncontrolled production of oxygen reactive species (ROS) causes DNA damage leading to germ cell apoptosis (GCA). The aim of the study is to explore whether inhibition of NADPH oxidase (NOX), a major source of intracellular ROS, will prevent tIRI-induced GCA and its association with endoplasmic reticulum (ER) stress. Sprague-Dawley rats (n = 36) were divided into three groups: sham, tIRI only and tIRI treated with apocynin (a NOX inhibitor). Rats undergoing tIRI endured an ischemic injury for 1 h followed by 4 h of reperfusion. Spermatogenic damage was evaluated histologically, while cellular damages were assessed using real time PCR, immunofluorescence staining, Western blot and biochemical assays. Disrupted spermatogenesis was associated with increased lipid and protein peroxidation and decreased antioxidant activity of the enzyme superoxide dismutase (SOD) as a result of tIRI. In addition, increased DNA double strand breaks and formation of 8-OHdG adducts associated with increased phosphorylation of the DNA damage response (DDR) protein H2AX. The ASK1/JNK apoptosis signaling pathway was also activated in response to tIRI. Finally, increased immuno-expression of the unfolded protein response (UPR) downstream targets: GRP78, eIF2-α1, CHOP and caspase 12 supported the presence of ER stress. Inhibition of NOX by apocynin protected against tIRI-induced GCA and ER stress. In conclusion, NOX inhibition minimized tIRI-induced intracellular oxidative damages leading to GCA and ER stress.

A mechanism of male germ cell apoptosis induced by bisphenol-A and nonylphenol involving ADAM17 and p38 MAPK activation

Germ cell apoptosis regulation is pivotal in order to maintain proper daily sperm production. Several reports have shown that endocrine disruptors such as Bisphenol-A (BPA) and Nonylphenol (NP) induce germ cell apoptosis along with a decrease in sperm production. Given their ubiquitous distribution in plastic products used by humans it is important to clarify their mechanism of action. TACE/ADAM17 is a widely distributed extracellular metalloprotease and participates in the physiological apoptosis of germ cells during spermatogenesis. The aims of this work were: 1) to determine whether BPA and NP induce ADAM17 activation; and 2) to study whether ADAM17 and/or ADAM10 are involved in germ cell apoptosis induced by BPA and NP in the pubertal rat testis. A single dose of BPA or NP (50 mg/kg) induces germ cell apoptosis in 21-day-old male rats, which was prevented by a pharmacological inhibitor of ADAM17, but not by an inhibitor of ADAM10. In vitro, we showed that BPA and NP, at similar concentrations to those found in human samples, induce the shedding of exogenous and endogenous (TNF-α) ADAM17 substrates in primary rat Sertoli cell cultures and TM4 cell line. In addition, pharmacological inhibitors of metalloproteases and genetic silencing of ADAM17 prevent the shedding induced in vitro by BPA and NP. Finally, we showed that in vivo BPA and NP induced early activation (phosphorylation) of p38 MAPK and translocation of ADAM17 to the cell surface. Interestingly, the inhibition of p38 MAPK prevents germ cell apoptosis and translocation of ADAM17 to the cell surface. These results show for the first time that xenoestrogens can induce activation of ADAM17 at concentrations similar to those found in human samples, suggesting a mechanism by which they could imbalance para/juxtacrine cell-to-cell-communication and induce germ cell apoptosis.

Involvement of TACE/ADAM17 and ADAM10 in etoposide-induced apoptosis of germ cells in rat spermatogenesis

Germ cell apoptosis is important to regulate sperm production in the mammalian testis, but the molecular mechanisms underlying apoptosis are still poorly understood. We have recently shown that in vitro, etoposide induces upregulation of TACE/ADAM17 and ADAM10, two membrane-bound extracellular metalloproteases. Here we show that in vivo these enzymes are involved in etoposide-, but not in heat shock-, induced apoptosis in rat spermatogenesis. Germ cell apoptosis induced by DNA damage was associated with an increase in protein levels and cell surface localization of TACE/ADAM17 and ADAM10. On the contrary, apoptosis of germ cells induced by heat stress, another cell death stimulus, did not change levels or localization of these proteins. Pharmacological in vivo inhibition of TACE/ADAM17 and ADAM10 prevents etoposide-induced germ cell apoptosis. Finally, Gleevec (STI571) a pharmacological inhibitor of p73, a master gene controlling apoptosis induced by etoposide, prevented the increase of TACE/ADAM17 levels. Our results strongly suggest that TACE/ADAM17 participates in in vivo apoptosis of male germ cells induced by DNA damage.

The emerging role of matrix metalloproteases of the ADAM family in male germ cell apoptosis

Constitutive germ cell apoptosis during mammalian spermatogenesis is a key process for controlling sperm output and to eliminate damaged or unwanted cells. An increase or decrease in the apoptosis rate has deleterious consequences and leads to low sperm production. Apoptosis in spermatogenesis has been widely studied, but the mechanism by which it is induced under physiological or pathological conditions has not been clarified. We have recently identified the metalloprotease ADAM17 (TACE) as a putative physiological inducer of germ cell apoptosis. The mechanisms involved in regulating the shedding of the ADAM17 extracellular domain are still far from being understood, although they are important in order to understand cell-cell communications. Here, we review the available data regarding apoptosis during mammalian spermatogenesis and the localization of ADAM proteins in the male reproductive tract. We propose an integrative working model where ADAM17, p38 MAPK, protein kinase C (PKC) and the tyrosine kinase c-Abl participate in the physiological signalling cascade inducing apoptosis in germ cells. In our model, we also propose a role for the Sertoli cell in regulating the Fas/FasL system in order to induce the extrinsic pathway of apoptosis in germ cells. This working model could be applied to further understand constitutive apoptosis in spermatogenesis and in pathological conditions (e.g., varicocele) or following environmental toxicants exposure (e.g., genotoxicity or xenoestrogens).

Survivin downregulation is associated with vasectomy-induced spermatogenic damage and apoptosis

OBJECTIVE

To evaluate the expression of the apoptotic genes survivin, Bax and Bcl-2 in vasectomized rabbits and to determine their relation with vasectomy-induced spermatogenic impairment and germ cell apoptosis.

MATERIALS AND METHODS

Twelve adult rabbits (6-12 months old) were divided into three groups: sham control, unilateral vasectomy or bilateral vasectomy. Six months after vasectomy, testicular tissue was analyzed for germ cell apoptosis and DNA fragmentation by the TUNEL assay and gel electrophoresis, respectively. Spermatogenesis was assessed using the Johnsen score. The relative gene expression of survivin, Bax and Bcl-2 was measured using reverse transcription followed by real-time PCR.

RESULTS

Compared to sham animals, a significant decrease in testicular survivin mRNA levels was measured in the two vasectomy animal groups (p < 0.05). This was accompanied by a significant increase in the Bax:Bcl-2 ratio in the vasectomized animals (p < 0.05). In addition, these data showed positive correlation with enhanced apoptotic index, damage to spermatogenesis and DNA fragmentation after vasectomy.

CONCLUSION

These findings demonstrate that vasectomy-induced damage to spermatogenesis due to testicular apoptosis may be associated with survivin downregulation and Bax overexpression.

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.

Deregulation of EZH2 expression in human spermatogenic disorders and testicular germ cell tumors

INTRODUCTION

Enhancer of Zeste 2 (EZH2) is an epigenetic transcriptional repressor involved in cell cycle control and cell fate decisions. Since these processes play key roles during intact spermatogenesis, deregulation of EZH2 expression may contribute to the development and progression of benign and malignant testicular diseases. The objective of this study was to investigate the expression profile of EZH2 in testicular germ cell tumors (TGCT) and spermatogenic defects.

MATERIAL AND METHODS

Real-time RT-PCR was applied to quantify the m-RNA expression of EZH2 in 64 seminomas 36 non-seminomas, 4 carcinomas in situ (CIS), 40 samples harboring impaired spermatogenesis and 24 normal testicular reference biopsies.

RESULTS

EZH2 was expressed in 99% of TGCT samples and in all biopsies with intact spermatogenesis. Its expression levels were highest in normal testicular tissue, and continuously decreased with malignant transformation to CIS and further progression to invasive TGCT (P < 0.001). EZH2 tumor levels were not related to the histological TGCT subtype or clinical tumor stage. Comparison of distinct stages of spermatogenic failure revealed an inverse association of EZH2 levels to the severity of the spermatogenic defect (P < 0.001).

CONCLUSION

Our data strongly suggest that in TGCT EZH2 does not exert its often assumed oncogenic properties during malignant transformation and progression. High EZH2 levels in normal testicular tissue and the inverse association of its expression levels with the severity of spermatogenic failure point to its potential value as a molecular marker for spermatogenic defects and may indicate an important physiological role of EZH2 during intact spermatogenesis.

Seminal plasma survivin in fertile and infertile males

PURPOSE

We assessed survivin (an inhibitor of apoptosis) protein in the seminal plasma of infertile and fertile males.

MATERIALS AND METHODS

Seminal plasma survivin was estimated by enzyme-linked immunosorbent assay in 23 healthy fertile volunteers, 22 men with oligo-asthenozoospermia, 37 with nonobstructive azoospermia and 12 with obstructive azoospermia. Histopathology and testicular sperm extraction were done in testicular tissue biopsies from obstructive azoospermia and nonobstructive azoospermia cases.

RESULTS

Mean seminal survivin was highest in fertile controls, less in oligo-asthenozoospermic cases and low in nonobstructive azoospermia cases with significant differences. In obstructive azoospermia cases seminal plasma survivin was absent. Seminal survivin positively correlated with sperm concentration and total sperm motility, and negatively correlated with the percent of sperm abnormal forms. Seminal survivin was detectable in nonobstructive azoospermia cases in which testicular sperm extraction was successful but absent in such cases when testicular sperm extraction was unsuccessful.

CONCLUSIONS

Seminal survivin is testicular in origin. It is related to spermatogenesis and sperm motility processes. Seminal survivin was related to successful testicular sperm extraction in nonobstructive azoospermia cases.

Role of the Survivin gene in pathophysiology

Although the roles of survivin in control of cancer cell division and apoptosis as well as targeting survivin for cancer therapeutics have been extensively explored and reviewed, the pathophysiological role of survivin in normal human cells/organs has not been deeply investigated or sufficiently reviewed. Studies in the latter area, however, appear to be important for the identification of different mechanisms of regulation and function of survivin in normal versus abnormal cells and tissues (including cancer), which might ultimately provide the basis for novel approaches for disease treatment with low toxicity. This Review is intended to summarize current observations in the literature related to the physiological and/or pathological roles for survivin in various normal human cells or organs. Our view of potential future research directions for survivin pertinent to potential therapeutic applications will also be discussed.

Testicular expression of survivin and human telomerase reverse transcriptase (hTERT) associated with spermatogenic function in infertile patients

AIM

To characterize the coexpression of survivin, an inhibitor of apoptosis (IAF), and human telomerase reverse transcriptase (hTERT) in human testes with varying spermatogenic function.

METHODS

Transcript levels of survivin mRNA and hTERT mRNA were determined in normal testes (n=11) and testes with defective spermatogenesis (n=28) using real-time reverse-transcription polymerase chain reaction (RT-PCR). The histological work-up was performed according to a modified Johnsen score.

RESULTS

Expressions of both survivin and hTERT were highest at median levels of 96.8 and 709 in normal spermatogenesis and dropped to 53.3 and 534 in testes with postmeiotic spermatogenic arrest (n=10). In severe spermatogenic failure (n=18), survivin expression was lacking in most specimens (n=16), whereas at least low levels of testicular hTERT expression were largely detectable with a normalized expression of 73 in premeiotic spermatogenic arrest (n=7) and 45 in patients with Sertoli cell-only syndrome (SCOS) (n=3). Both survivin and hTERT expressions increased with a progressing Johnsen score (P for trend=0.001).

CONCLUSION

Although both survivin and hTERT are correlated with spermatogenic function, they show different expression patterns in testes of infertile patients. These findings substantiate results from studies in the rodent testis suggesting a predominant expression of survivin in meiotically dividing germ cells.

The regulated expression of c-IAP1 and c-IAP2 during the rat seminiferous epithelial cycle plays a role in the protection of germ cells from Fas-mediated apoptosis

The inhibitor of apoptosis proteins, c-IAP1 and c-IAP2, are highly expressed in rat testis and potentially play a regulatory role in testicular apoptosis. To better understand their functions during spermatogenesis, we have analyzed their spatio-temporal distribution in rat testis, how their expression is controlled by the paracrine stem-cell factor (SCF) and how they affect Fas-mediated apoptosis. Both c-IAP1 and c-IAP2 showed cycles of transcriptional expression, throughout the seminiferous epithelial cycle. c-IAP1 protein showed a diffuse nuclear distribution in type B spermatogonia, preleptotene, leptotene, and zygotene spermatocytes. In pachytene spermatocytes, c-IAP1 colocalized with SUMO-1 in the XY-body. c-IAP2 protein was cytoplasmic in spermatocytes, from stage VI pachytene onwards, round spermatids, elongated spermatids and Leydig cells. Its expression was upregulated by SCF. Inhibition of IAP activity resulted in a greater sensitivity of germ cells to Fas-mediated apoptosis. These results suggest an important role for IAPs in the regulation of spermatogenic apoptosis.

The inhibitor of apoptosis (IAP) survivin is expressed in human testicular germ cell tumors and normal testes

Deregulated apoptosis of germ cells may contribute to malignant transformation as well as male infertility. We analyzed expression of the inhibitor of apoptosis survivin by polymerase chain reaction (PCR) in testicular germ cell tumors (TGCTs, n=28), normal testes (n=19) and testes with defective spermatogenesis (n=22). In a subset of samples (n=35), survivin transcript levels were quantified using real-time PCR. While survivin mRNA was expressed at high levels in undifferentiated TGCTs and normal testes, it was lost in mature teratomas and germ cell aplasia. Survivin expression in both normal and transformed germ cells is in contrast to its sharp differential expression in other tissues. Survivin expression correlates with the differentiation state of TGCTs and may be relevant for their tumorigenesis and malignant potential.

Quantification of survivin mRNA in testes of infertile patients and in testicular germ cell tumours: high levels of expression associated with normal spermatogenesis

Deregulated apoptosis of germ cells may contribute to male infertility as well as malignant transformation. Survivin, an inhibitor of apoptosis (IAP), is overexpressed in all the most common human malignancies, but barely detectable in normal tissues. We used real-time polymerase chain reaction (PCR) to quantify survivin mRNA expression in normal testes (n = 22), testes with defective spermatogenesis (n = 26) and testicular germ cell tumours (TGCTs; n = 16). Survivin was expressed at high levels in normal testes. Testicular survivin levels in infertile patients were related inversely to the severity of spermatogenic failure (p < 0.001), with a lack of expression in most specimens with pre-meiotic spermatogenic arrest and in all those with germ cell aplasia. Lower levels of expression were observed in TGCTs than in normal testes. While survivin expression was detected in most TGCTs with undifferentiated components (12 of 13), it was absent in all mature teratomas (n = 3). These data show that survivin is expressed in normal and transformed germ cells. Its downregulation in spermatogenic disorders indicates that survivin may contribute to the normal balance between germ cell proliferation and apoptosis. In TGCTs, survivin expression appears to be lost with somatic differentiation.