Apoptosis: its importance in spermatogenic dysfunction

The role of p53 in male infertility

The tumor suppressor p53 is a transcription factor involved in a variety of crucial cellular functions, including cell cycle arrest, DNA repair and apoptosis. Still, a growing number of studies indicate that p53 plays multiple roles in spermatogenesis, as well as in the occurrence and development of male infertility. The representative functions of p53 in spermatogenesis include the proliferation of spermatogonial stem cells (SSCs), spermatogonial differentiation, spontaneous apoptosis, and DNA damage repair. p53 is involved in various male infertility-related diseases. Innovative therapeutic strategies targeting p53 have emerged in recent years. This review focuses on the role of p53 in spermatogenesis and male infertility and analyses the possible underlying mechanism involved. All these conclusions may provide a new perspective on drug intervention targeting p53 for male infertility treatment.

Identification of a novel pyroptosis-related gene signature in human spermatogenic dysfunction

PURPOSE

To reveal the underlying roles that pyroptosis-related genes (PRGs) played in human spermatogenic dysfunction.

METHODS

One discovery set and three validation sets were employed to inspect the previously reported 33 PRGs in the human testis with different status of spermatogenesis. PRGs that differentially expressed in all sets were considered as key differentially expressed pyroptosis-related genes (PR-DEGs). The relationships between key PR-DEGs and samples' clinicopathological, therapeutic, and immune patterns were respectively studied. Single-cell RNA sequencing (scRNS-seq) analyses were conducted to show the expression changes and related mechanisms of key PR-DEGs at a single-cell resolution.

RESULTS

CASP4 and GPX4 were identified as two key PR-DEGs. These two genes were significantly dysregulated in spermatogenic dysfunctional samples, but with opposite tendency. CASP4 was negatively correlated with Johnsen scores but positively correlated with follicle-stimulating hormone (FSH) levels (all p < 0.05), while GPX4 exhibited significant positive correlations with Johnsen scores and negative relevance with FSH. For treatments, both molecules showed a prospective value of being predictors for sperm retrieval surgeries. Moreover, CASP4 and GPX4 were potential immunoregulators in the testicular immune microenvironment and showed significant correlations to testicular macrophages and mast cell infiltration. In scRNA-seq analyses, GPX4 was highly expressed in germ cells, which therefore suffered a sharp reduction with the loss of germ cells in spermatogenic dysfunction. On the other hand, CASP4 were basically somatic cell-derived, and the proportion of CASP4-positive Leydig cells significantly increased in disease testes (p = 0.0001).

CONCLUSION

In all, we revealed two key PRGs of human testes that might be functional in spermatogenic dysfunction.

LDLR heterozygous deletion reduces hamster testicular cholesterol toxicity via AMPK/Sirt1/PGC-1α pathway

Cholesterol is an important part of the human diet. The relationship and molecular mechanisms between intracellular cholesterol and male infertility are unclear. The purpose of this study was to evaluate the role of low-density lipoprotein receptor (LDLR) in male infertility. Both wild-type (WT) and LDLR heterozygous deletion (LDLR+/-) male Golden Syrian hamsters were fed either a high-fat diet (HFD) or a normal diet (ND). Plasma biochemistry, serum hormone, testicular histopathology, mRNA and protein expression of AMPK/Sirt1/PGC-1α in both testicular tissue and isolated Leydig cells (LCs) were measured. Compared with the ND animals, the WT HFD hamsters developed dyslipidemia at three weeks with lipid droplets deposited in LCs, testosterone decreased at four weeks (0.440 ± 0.264 ng/ml vs. 2.367 ± 1.236 ng/ml), the number of the Sertoli cells decreased (21.578 ± 2.934/one tubule vs. 25.733 ± 3.424/one tubule), the seminiferous epithelium became thinner (0.0813 ± 0.01729 mm vs. 0.0944 ± 0.0138 mm), testicular atrophy and AMPK/Sirt1/PGC-1α pathway downregulated at five weeks. All these changes persisted until the end of the study. LDLR+/- alleviated all of the above changes by downregulating the cellular influx of cholesterol induced by HFD except for higher hyperlipidemia. In summary, excessive intracellular cholesterol inactivates AMPK/Sirt1/PGC-1α pathway firstly in LCs and then in both Sertoli and spermatids. Cholesterol toxicity was LDLR dependent.

Grape seed extract improved the fertility-enhancing effect of atorvastatin in high-fat diet-induced testicular injury in rats: involvement of antioxidant and anti-apoptotic effects

Objectives

Reduced male fertility is highly prevalent with hypercholesterolaemia. Though statins are drugs of choice for hypercholesterolaemia, their effect on male fertility is still controversial and dose-dependent. Grape seed extract (GSE) possess hypocholesterolemic and testicular protective effects. Thus, this study aimed to investigate the effects of low-dose atorvastatin (ATV) on male infertility in hypercholesterolaemic rats and assess the additional value of combining ATV with GSE.

Methods

Male rats were randomized into four groups. The normal group was fed a standard diet. The remaining groups were fed a high-fat diet (HFD) for 1 month to induce hypercholesterolaemia. Two HFD groups were administered either ATV (1 mg/kg) alone or combined with GSE (200 mg/kg) orally for 65 days, while the third group served as HFD control.

Key findings

Treatment with ATV or ATV/GSE attenuated dyslipidemia-induced alteration in serum HDL-cholesterol, LDL-cholesterol, and total cholesterol. ATV enhanced serum testosterone, sperm count and motility and fertility index. The effect on testosterone and sperm count was more pronounced by ATV/GSE. Moreover, ATV reduced testicular malondialdehyde, nitric oxide, caspase-9 and caspase-3 while elevated reduced glutathione and superoxide dismutase along with catalase activity. Noteworthy, GSE/ATV induced more powerful antioxidant and anti-apoptotic effects.

Conclusion

GSE enhanced ATV’s protective effect against hypercholesterolaemia-induced infertility via antioxidant and anti-apoptotic mechanisms.

Wuzi Yanzong Pill-Based on Network Pharmacology and In Vivo Evidence-Protects Against Spermatogenesis Disorder via the Regulation of the Apoptosis Pathway

The crisis of male infertility is an issue of human reproductive health worldwide. The Wuzi Yanzong pill (WZYZP) is a traditional Chinese medicine prescription that shows efficacy in kidney reinforcement and essence benefit to ameliorate male reproductive dysfunctions. However, the pharmacological mechanisms of the WZYZP on male infertility have not been investigated and clarified clearly. This study was designed to investigate the effects of the WZYZP on spermatogenesis disorder and explore its underlying pharmacological mechanisms. First, based on a network pharmacology study, 39 bioactive compounds and 40 targets of the WZYZP associated with spermatogenesis disorder were obtained, forming a tight compound-target network. Molecular docking tests showed tight docking of these compounds with predicted targeted proteins. The protein-protein interaction (PPI) network identified TP53, TNF, AKT1, Bcl-XL, Bcl-2, and IκBA as hub targets. The Kyoto Encyclopedia of Genes and Genomes pathway network and pathway-target-compound network revealed that the apoptosis pathway was enriched by multiple signaling pathways and multiple targets, including the hub targets. Subsequently, the chemical characterization of WZYZP was analyzed using liquid chromatography to quadrupole/time-of-flight mass spectrometry, and 40 compounds in positive ion mode and 41 compounds in negative ion mode in the WZYZP were identified. Furthermore, based on the prediction of a network pharmacology study, a rat model of spermatogenesis disorder was established to evaluate the curative role and underlying mechanisms of the WZYZP. The results showed that WZYZP treatment improved rat sperm quality and attenuated serum hormone levels, reversed histopathological damage of the testis, reduced cell apoptosis in testis tissues, and ameliorated the expression of the predicted hub targets (TP53, TNF-α, AKT1, NFκB, and IκBA) and the apoptosis related proteins (Bcl-XL, Bcl-2, Bax, Caspase 3, and Caspase 9). These results indicated that the WZYZP has a protective effect on spermatogenesis disorder, suggesting that it could be an alternative choice for male infertility therapy.

Advances in surgical treatment of male infertility

A male factor is the only cause of infertility in 30% to 40% of couples. Most causes of male infertility are treatable, and the goal of many treatments is to restore the ability to conceive naturally. Varicoceles are present in 15% of the normal male population and in approximately 40% of men with infertility. Varicocele is the most common cause of male infertility that can be corrected surgically. In males with azoospermia, the most common cause is post-vasectomy status. Approximately 6% of males who undergo vasectomy eventually seek reversal surgery. Success of vasectomy reversal decreases with the number of years between vasectomy and vasovasostomy. Other causes of obstructive azoospermia include epididymal, vasal or ejaculatory duct abnormalities. Epididymal obstruction is the most common cause of obstructive azoospermia. Patients with epididymal obstruction without other anatomical abnormalities can be considered as candidates for vasoepididymostomy. With microsurgical techniques, success of patency restoration can reach 70~90%. In case of surgically uncorrectable obstructive azoospermia, sperm extraction or aspiration for in vitro fertilization is needed. Nonobstructive azoospermia is the most challenging type of male infertility. However, microsurgical testicular sperm extraction may be an effective method for nonobstructive azoospermia patients.

Fas ligand in bull ejaculated spermatozoa:A quantitative immunocytochemical study

Apoptosis, or programmed cell death, provides a way to remove redundant cells at the end of their lifespan and thus acts as a homeostatic mechanism, maintaining the correct number of cells in the body by balancing their production and death. In the testis, this process seemed to play a pivotal role in spermatogenesis. It is generally accepted that Sertoli cells control the germ cell population through one of the best-known apoptotic pathways, the Fas/Fas L paracrine signal transduction system, in which a Fas ligand (Fas L) expressed by Sertoli cells induces apoptosis when it binds with its receptor, Fas, expressed by the germ cells. Recently, we demonstrated the presence of Fas antigen in normal ejaculated spermatozoa from fertile bulls and suggested that this molecule might have a non-apoptotic, defensive role against injuries, especially oxidative stress. We have now investigated whether bull mature, fertile spermatozoa express not only the Fas receptor but also its natural ligand Fas L. Our results indicate that the whole sperm population expresses Fas L. We suggest that Fas L in bull spermatozoa, like in murine spermatozoa, might be able to kill activated lymphocytes and protect the male gamete from damage by the self-immune system or the cytotoxic activity of leukocytes in the female genital tract.

A possible role of Fas antigen in ejaculated spermatozoa of fertile bulls: an immunocytochemical quantitative approach

The Fas/Fas L system is a widely recognized apoptosis signal transduction pathway in which transmembrane receptor protein (Fas) triggers a programmed cell death when bound by the Fas ligand (Fas L). This system in the testis is believed to be a paracrine signaling system by which Sertoli cells expressing Fas L can initiate killing of Fas-expressing germ cells during spermatogenesis. So far, the presence of Fas antigen in ejaculated spermatozoa was related only to subfertility or infertility conditions. We demonstrated for the first time that normal ejaculated spermatozoa also express Fas antigen. Our data showed that a large percentage of normal ejaculated spermatozoa of fertile bulls are immunocytochemically positive for Fas. Our observations provide further evidence of the "regionalization" of sperm membrane antigens. Furthermore, we suggest that in mature fertile ejaculated spermatozoa the Fas antigen may also provide resistance to programmed cell death, like in some other cells expressing molecules that inhibit the signals induced by Fas or the death program itself. In addition, we suggest that Fas antigen can partly protect the spermatozoa against apoptosis induced by lipoperoxidative damage that can occur spontaneously in the male gamete at various stages in its lifetime.

Apoptosis and proliferation in human undescended testes

OBJECTIVE

To study apoptosis and proliferation in the testes of children with undescended testes; the degree to which undescended testes contributes to a patient's ultimate fertility is debatable, but undescended testes have fewer germ cells, and some have proposed that apoptosis is an important cause.

PATIENTS AND METHODS

Testis biopsies were taken at the time of orchidopexy in a consecutive series of children undergoing surgical repair for undescended testes. Immunohistological techniques were used to detect apoptosis and proliferation, and the numbers of cells undergoing apoptosis or proliferation per 50 seminiferous tubules were recorded.

RESULTS

Inguinal testes had less apoptosis than abdominal testes, with a mean (sd) of 0.71 (1.31) vs 1.63 (1.95) apoptotic cells per 50 seminiferous tubules (P < 0.02). Similarly, there was less apoptosis in children aged > 1 years than in children aged < 1 years (0.68 (1.40) vs 1.35 (1.56); P < 0.03). Proliferation was very limited in all cryptorchid testes. In contrast to cryptorchid testes, five autopsy controls had many more apoptotic cells, (10.60 (1.34) per 50 seminiferous tubules), and many more proliferating cells, (8.40 (6.43) per 50 seminiferous tubules).

CONCLUSION

In contrast to animal studies, neither apoptosis nor proliferation was common in undescended testes from 6 months of age onward. However, apoptosis was more common in abdominal testes and in children aged < 1 year. It is likely that, if substantial apoptosis occurs in human undescended testes, it occurs before 6 months of age.

Cloning and characterization of testis-specific spermatogenesis associated gene homologous to human SPATA4 in rat

Rat SPATA4 gene, homologue to the human and mouse SPATA4 gene, expressed specifically in the rat testis was cloned by informatics analysis. The cDNA mapped to chromosome 16 in the rat genome is made up of 6 exons and the exon-intron boundaries obey to the AG/GT rule. The gene contains a 972 bp open reading frame encoding 323 amino acid sequences with theoretical molecular weight of 36.64 KD and isoelectric point of 9.65. One CpG island is located in the gene from site -200 to +198. A typical promoter is also predicted from site -630 to +101. According to the computer-aided analysis of the putative protein encoded by the rat SPATA4, no transmembrane region and no signal peptides are found in the protein. Multi-tissue RT-PCR results show that the SPATA4 gene is expressed specifically in the testis only. Moreover, the expression of SPATA4 occurs in a development stage-dependent pattern. According to the RT-PCR results, no expression of SPATA4 is detected until the rat is 30 d old after birth. The amount of SPATA4 mRNA increases from 30-d to 65-d-old rat and then keeps stable after that. In conclusion, this study proves the conservation of SPATA4 in mammalian animals and predicts its important role in spermatogenesis.

Paraspermatogenesis of Cerithioidean snails: Retention of an acrosome and nuclear remnant

Paraspermatozoa of Cerithioidea are oligopyrenic with a central nuclear remnant surrounded by glycoprotein bodies and an anterior acrosome complex. Posteriorly, the parasperm have one long and several small flagella. Biosynthesis of proteins begins in the rough endoplasmic reticulum (RER), early in paraspermatogenesis, prior to the degradation of the nucleus. The breakdown of the nucleus has features characteristic of apoptosis but a nuclear remnant remains that is composed of intact DNA. The acrosome complex of parasperm is Golgi-derived, forming posteriorly and migrating anteriorly along the plasma membrane to the apex of the nuclear remnant as the paraspermatid matures. This mechanism of acrosome formation is similar to that in euspermiogenesis in neomenioid aplacophorans and neritid snails and is plesiomorphic to mollusks. However, eusperm acrosomes of Cerithioidea form differently. In the paraspermatid, small, dense granules secreted by the Golgi body fuse to form larger granular vesicles, many of which are released by exocytosis into the seminal fluid. These granular vesicles stain red with acridine orange at pH 7 under 489-nm light, indicating that they are lysosomes. The retention of a nuclear remnant and development of an acrosome complex in the parasperm of cerithioideans, as well as the secretion of lysosomes into the seminal fluid, suggests novel functions for these unusual germ cells.