New insights about the early diagnosis of fertility impairment in varicoceles: the DNA repair gene example

Genetics and epigenetics of varicocele pathophysiology: an overview

Varicocele is found in approximately 20% of adults and adolescents and in 19-41% of men seeking treatment for infertility. It is associated with a decrease in sperm count as well as sperm motility and morphology. The currently accepted description of the pathophysiology of varicocele does not explain all its clinical manifestations; therefore, other factors such as genetic and epigenetic changes, associated with the environment, might be involved in causing infertility and decrease in sperm quality. It has been reported that the varicocele-induced deterioration of testicular function is progressive and interferes with fertility; hence, early and efficient assessment of the genetic manifestations in patients would be important for developing future medical interventions. Chromosomal disorders, mutations, polymorphisms, changes in gene expression, and epigenetic changes have all been reported to be associated with varicocele. Several studies are underway to unravel the genetic basis of this disease, as it is important to understand the origin and the aggravating factors to ensure appropriate guidance and intervention. Here, we review the available literature regarding the genetic and epigenetic changes associated with varicocele, and how these alterations are related to the different clinical manifestations of the disease.

Abnormal Accumulation of Collagen Type I Due to the Loss of Discoidin Domain Receptor 2 (Ddr2) Promotes Testicular Interstitial Dysfunction

Background

Loss of functional allele for discoidin domain receptor 2 (Ddr2) results in impaired Leydig cell response to luteinizing hormone (LH), low testosterone production and arrested spermatogenesis in older male Ddr2^slie/slie mice. However, the underlying mechanism responsible for this phenotype remains unknown. Herein, we reported for the first time that the deregulated expression of Ddr2 cognate ligand, namely collagen type I (COL1), may account for the disruption of the testicular steroidogenesis in Ddr2^slie/slie mutant testes.

Methodology/Principal Findings

Expression of Ddr2 increased gradually along postnatal development, whereas COL1 expression became negligible from adulthood onwards. In Ddr2^slie/slie mutant testis, however, in contrast to the undetectable staining of Ddr2, COL1 expression was constantly detected, with the highest values detected during adulthood. In the experimental vasectomy model, Ddr2^slie/slie mutant mice exhibited an early androgen deficiency than wild-type mice, along with the accumulation of fibrotic tissue in the interstitium. Functionally, ablation of endogenous Ddr2 resulted in a significant decrease of testosterone (T) level in TM3 cells in the presence of higher concentration of COL1 treatment. Conversely, overexpression of Ddr2 could help TM3 cells to maintain a normal testicular steroidogenesis even in the presence of high concentration of COL1. Additionally, attenuated expression of Ddr2 correlates to the deregulated level of serum T levels in human pathological testes.

Conclusions

Abnormal accumulation of interstitial COL1 may be responsible for the steroidogenic dysfunction in Ddr2^slie/slie mutant testes.

YES1 activation elicited by heat stress is anti-apoptotic in mouse pachytene spermatocytes

Deregulated expression of protein tyrosine phosphorylation has been implicated in testicular response to different stimuli. Herein, YES1, a nonreceptor protein tyrosine kinase, was found to be significantly up-regulated in pachytene spermatocytes (PS) during early recovery from a transient testicular heat stress. Coculture of PS with Sertoli cells (SCs) could enhance the hyperthermia-induced YES1 activation, indicative of a positive regulation of the paracrine signaling. Moreover, SU6656, a selective YES1 inhibitor, was shown to effectively block YES1 activity, thereafter resulting in a dramatic increase of heat stress-induced apoptosis in primary cultured PS. Mechanistically, the antiapoptotic effect of YES1 activation in response to testicular heat insult may mediate via the regulation of extracellular signal-regulated kinase (ERK)/metastasis-associated 1 (MTA1) cascade. From a clinical standpoint, a notably higher level of YES1 expression was observed in the pathological testis from varicocele patients as compared to a negligible staining in the control group. Taken together, our present results provide the first evidence that the YES1/ERK/MTA1/p53 cascade may serve as a naturally occurring, indispensable self-defensive mechanism maintaining apoptotic balance during meiotic heat stress. Our study may have also partially answered the question of how activation of signal pathways at the cell membrane surface interacts with the key regulatory events occurring in the nucleus during testicular heat shock.

Male fertility and varicocoele: role of immune factors

The role of antisperm antibodies (ASA) in the aetiopathogenesis of varicocoele-related male infertility remains unclear. The objective of this study was to determine whether varicocoele is associated with antisperm immune response and whether this factor provides additional affect on male fertility. We performed a multicentral, prospective study that included the clinical examination of 1639 male subjects from infertile couples and 90 fertile men, the evaluation of the absolute and relative risks of immune infertility associated with varicocoele and the impact of the autoimmune response on the semen quality. The methods used were as follows: standard examination of seminal fluid according to WHO criteria; ASA detection in seminal fluid using mixed antiglobulin reaction (MAR) and direct flow cytometry; measurement of spontaneous and ionophore-induced acrosome reactions; oxidative stress evaluation with luminal-dependent chemiluminescence method and evaluation of DNA fragmentation by sperm chromatin dispersion. The prevalence of varicocoele-related immune infertility is about 15% and does not depend on the grade of vein dilatation both in primary and secondary fertility disorders. Varicocoele is not an immediate cause of autoimmune reactions against spermatozoa, but is a cofactor increasing ASA risk; the OR of immune infertility after a testicular trauma in varicocoele patients increases twofold. In varicocoele patients, the autoimmune antisperm reaction is accompanied by a more significant decrease in the semen quality (concentration and number of progressively motile and morphologically normal spermatozoa in the ejaculate), acrosome reaction disorders (presence of pre-term spontaneous and lack of induced reactions) and an increase in the proportion of spermatozoa with DNA fragmentation. These disorders correlate with the level of sperm oxidative stress; reactive oxygen species (ROS) production in ASA-positive varicocoele patients is 2.8 and 3.5 times higher than in ASA-negative varicocoele patients and fertile men respectively. We did not find correlation between the grade of spermatic cord vein dilatation and ROS production.

Apurinic/apyrimidinic endonuclease immunoreactivity in germ cells of experimental varicocele-induced rat testes

Increased germ cell apoptosis is related to oxidative DNA damage; therefore, we investigated whether there was a significant change in apurinic/apyrimidinic endonuclease (APE) in varicoceles. Experimental varicoceles were created by partial ligation of the left renal vein of adult male Sprague-Dawley rats, which were sacrificed at 1, 3 and 6 weeks after varicocele creation. Testicular tissues were sampled for TUNEL, Western blotting and immunohistochemistry. There was a significant increase in apoptotic germ cells in the ipsilateral testes 6 weeks after varicocele creation. Increased activation of p53, Bax and cleaved caspase-3 in the left testes was also noted. APE increased activation until 3 weeks after varicocele creation, and then decreased at 6 weeks after varicocele surgery. The spermatocytes were immunostained for both 8-hydroxy-2'-deoxyguanosine and APE, but the spermatogonia revealed only APE immunopositivity in the defective tubules. These results suggest that repression of APE is an underlying mechanism of augmented p53-dependent apoptosis in varicocele-induced rat testes and that remaining APE in the spermatogonia plays a decisive role in regaining testicular spermatogenic function after varicocelectomy.

Repression of NR4A1 by a chromatin modifier promotes docetaxel resistance in PC-3 human prostate cancer cells

Epigenetic silencing mechanisms play an important role in chemoresistance of human cancer. Here we report the upregulated expression of metastasis-associated protein 1 (MTA1), a component of the nucleosome remodeling deacetylation (NuRD) complex, in chemoresistant prostate cancer (PCa). MTA1 knockdown in PC-3 cells inhibited cell proliferation and enhanced docetaxel (DTX)-induced cell death. Conversely, overexpression of MTA1 promotes DTX chemoresistance in PC-3 cells. MTA1 acted as a potent corepressor of the nuclear receptor NR4A1 transcription by interacting with histone deacetylase 2 (HDAC2). These findings suggest that MTA1 may serve as a novel DTX-resistance promoter in PC-3 cells.