Interactions among motility, fertilizing ability, and testosterone binding on spermatozoa of bonnet monkey (Macaca radiata)

Comparative analysis of the detrimental in vitro effects of three fusariotoxins on the selected structural and functional characteristics of rabbit spermatozoa

In this study, we evaluated the in vitro effects of 1-50 μM zearalenone (ZEA), deoxynivalenol (DON) and T-2 toxin (T-2) on rabbit spermatozoa for as much as 8 h of in vitro exposure. Our results indicate that all sperm quality parameters were negatively affected by these fusariotoxins in a time- and dose-dependent manner. The most prominent structure affected by ZEA was the plasma membrane, exhibiting alterations consistent with the onset of apoptosis and reactive oxygen species (ROS) overproduction. This correlated with the most prominent decline of the sperm motility among all selected fusariotoxins. Significant necrotic changes and mitochondrial dysfunction were primarily responsible for the sperm damage in the presence of T-2. Finally, exposure of spermatozoa to DON led to a significant decrease in the DNA integrity. This study may provide new information on the specific mechanisms of action involved in the in vitro toxic behavior of fusariotoxins on male gametes.

Influence of testosterone administration at the end of the breeding season on sperm cryoresistance in rams (Ovis aries) and bucks (Capra hircus)

This study examines the influence of administering testosterone at the end of the mating season, on the responses (morphometric and functional) of ram and buck sperm to freezing-thawing. Five rams were administered 25 mg testosterone propionate (TP) subcutaneously in 2 mL of olive oil twice per week (Monday and Thursday) from October 1 to 31; 5 bucks received exactly the same treatment but from November 1 to 30. Control groups were administered 2 mL of olive oil without TP twice per week over the same period. In the rams, no significant differences were seen in plasma testosterone between the treated and control groups during treatment (0.8 ± 0.2 ng/mL vs 1.5 ± 0.5 ng/mL; P > 0.05). Significant differences were seen in this respect, however, in the bucks (4.3 ± 0.8 ng/mL and 6.9 ± 0.9 ng/mL; P < 0.05). In the rams, TP treatment increased (P < 0.05) the straight-line velocity (VSL), linearity (LIN), straightness (STR) and wobble (WOB) values in fresh sperm samples. Similarly, in the frozen-thawed samples, TP treatment increased the VSL, average path velocity (VAP), LIN and WOB values (P < 0.05) compared with controls. In the bucks, treatment with TP had no effect on any measured variable in fresh sperm; frozen-thawed sperm, however, returned greater VSL, LIN, STR, and WOB values (P < 0.05) than did controls. In the rams, treatment with TP led to a reduction in all fresh sperm head morphometric variables (P < 0.05). Freezing-thawing further reduced (P < 0.05) all morphometric variables in both the control and treated groups. In the bucks, treatment with TP increased (P < 0.05) the length, area, and perimeter of fresh sperm cells, unlike that seen in ram sperm. Compared with fresh sperm, freezing-thawing led to reduced (P < 0.05) morphometric variables in both the control and treated bucks, except for the sperm head width, which in the controls remained unchanged. In conclusion, TP treatment at the end of the mating season affected fresh sperm quality, in both Spanish Merino rams and Murciano-Granadina bucks, in a species-specific manner, but improved the sperm kinetic variables after freezing-thawing in both species, apparently improving sperm cryoresistance. Treatment with TP affects the dimensions of the sperm head in a species-specific manner.

Steroid receptors and their ligands: effects on male gamete functions

In recent years a new picture of human sperm biology is emerging. It is now widely recognized that sperm contain nuclear encoded mRNA, mitochondrial encoded RNA and different transcription factors including steroid receptors, while in the past sperm were considered incapable of transcription and translation. One of the main targets of steroid hormones and their receptors is reproductive function. Expression studies on Progesterone Receptor, estrogen receptor, androgen receptor and their specific ligands, demonstrate the presence of these systems in mature spermatozoa as surface but also as nuclear conventional receptors, suggesting that both systemic and local steroid hormones, through sperm receptors, may influence male reproduction. However, the relationship between the signaling events modulated by steroid hormones and sperm fertilization potential as well as the possible involvement of the specific receptors are still controversial issues. The main line of this review highlights the current research in human sperm biology examining new molecular systems of response to the hormones as well as specific regulatory pathways controlling sperm cell fate and biological functions. Most significant studies regarding the identification of steroid receptors are reported and the mechanistic insights relative to signaling pathways, together with the change in sperm metabolism energy influenced by steroid hormones are discussed.The reviewed evidences suggest important effects of Progesterone, Estrogen and Testosterone and their receptors on spermatozoa and implicate the involvement of both systemic and local steroid action in the regulation of male fertility potential.

Status of the down-regulated canine testis using two different GNRH agonist implants in comparison with the juvenile testis

Testicular function in the dog was down-regulated using two different GNRH agonist implants, with adult and juvenile testes serving as controls. Treatment resulted in an increased percentage of the interstitial area and decreased area of Leydig cell nuclei. Expression of StAR and the steroidogenic enzymes cytochrome P450 side-chain cleavage enzyme (P450scc, CYP11A1) and cytochrome P450 17α-hydroxylase-17,20-lyase (P450c17, CYP17A1) in Leydig cells was blocked at the mRNA and protein level, showing no differences between the two agonists. Staining for androgen receptor (AR) by immunohistochemistry was positive in Sertoli, Leydig and peritubular cells and some spermatogonia, with in situ hybridization confirming expression in Sertoli cells. At the mRNA level, expression of AR was not affected; however, translation was blocked (reduced percentage of AR-positive Sertoli cells), with the number of nuclei in basal position being decreased. In the juvenile testes, mRNA expression of StAR, CYP11A1 and CYP17A1 was higher compared with the other groups but distinctly lower for the AR. At the protein level, the expression was at the limit of detection for StAR; AR-positive Sertoli cells were not detected. Our observations show that the down-regulated testis is different from the juvenile one rather resembling the testicular status in seasonal breeders out of season.

Detection of aromatase, androgen, and estrogen receptors in bank vole spermatozoa

Spermatozoa are highly specialized cells which transport a single-copy haploid genome to the site of fertilization. Before this, spermatozoa undergo a series of biochemical and functional modifications. In recent years, the crucial role of androgens and estrogens in proper germ cell differentiation during spermatogenesis has been demonstrated. However, their implication in the biology of mature male gametes is still to be defined. Our study provides evidence for the first time that aromatase, the androgen receptor (AR), as well as the estrogen receptors α and β (ERα and ERβ), are present in bank vole spermatozoa. We demonstrated the region-specific localization of these proteins in bank vole spermatozoa using confocal microscopy. Immunoreactive aromatase was observed in the proximal head region and in both the proximal and distal tail regions, whereas steroid hormone receptors were found only in the proximal region of the sperm head. Protein expression in sperm lysates was detected by Western blot analysis. Immunohistochemical results were analyzed quantitatively. Our results show that bank vole spermatozoa are both a source of estrogens and a target for steroid hormone action. Moreover, the presence of aromatase and steroid hormone receptors in the bank vole spermatozoa indicates a potential function of these proteins during capacitation and/or the acrosome reaction.

Immunolocalization of estrogen receptor alpha, estrogen receptor beta and androgen receptor in the pre-, peri- and post-pubertal stallion testis

In various species, androgens and estrogens regulate the function of testicular Leydig, Sertoli, peritubular myoid, and germ cells by binding to their respective receptors and eliciting a cellular response. Androgen receptor (AR) is expressed in Sertoli cells, peritubular myoid cells, Leydig cells and perivascular smooth muscle cells in the testis depending on the species, but its presence in germ cells remains controversial. Two different estrogen receptors have been identified, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), and their localization and function in testicular cells varies depending on the species, developmental stage of the cell and type of receptor. The localization of AR in an immature and mature stallion has been reported but estrogen receptors have only been reported for the mature stallion. In the present study, the localizations of AR and ERα/ERβ were investigated in pre-pubertal, peri-pubertal and post-pubertal stallions. Testes were collected by routine castration from 21 horses, of light horse breeds (3 months-27 years). Animals were divided into the following age groups: pre-pubertal (3-11 months; n=7), peri-pubertal (12-23 months; n=7) and post-pubertal (2-27 years; n=7). Testicular tissue samples were fixed and embedded, and the presence of AR, ERα and ERβ was investigated by immunohistochemistry (IHC) using procedures previously validated for the horse. Primary antibodies used were rabbit anti-human AR, mouse anti-human ERβ and rabbit anti-mouse ERα. Sections of each region were incubated with normal rabbit serum (NRS; AR and ERα) or mouse IgG (ERβ) instead of primary antibody to generate negative controls. Androgen receptors were localized in Leydig, Sertoli and peritubular myoid cells of all ages. Estrogen receptor alpha was localized in Leydig and germ cells of all ages but only in pre- and peri-pubertal Sertoli cells and post-pubertal peritubular myoid cells. Estrogen receptor beta was localized in Leydig and Sertoli cells of all ages but in only pre-pubertal germ cells and absent in peritubular myoid cells of all ages. Taken together, the data suggest that estrogen regulates steroidogenesis by acting through ERα and ERβ in the Leydig cells and promotes gametogenesis by acting through ERβ in the Sertoli cells and ERα in the germ cells. In contrast androgen receptors are not found in germ cells throughout development and thus are likely to support spermatogenesis by way of a paracrine/autocrine pathway via its receptors in Leydig, Sertoli and peritubular myoid cells.

Androgen receptor roles in spermatogenesis and fertility: lessons from testicular cell-specific androgen receptor knockout mice

Androgens are critical steroid hormones that determine the expression of the male phenotype, including the outward development of secondary sex characteristics as well as the initiation and maintenance of spermatogenesis. Their actions are mediated by the androgen receptor (AR), a member of the nuclear receptor superfamily. AR functions as a ligand-dependent transcription factor, regulating expression of an array of androgen-responsive genes. Androgen and the AR play important roles in male spermatogenesis and fertility. The recent generation and characterization of male total and conditional AR knockout mice from different laboratories demonstrated the necessity of AR signaling for both external and internal male phenotype development. As expected, the male total AR knockout mice exhibited female-typical external appearance (including a vagina with a blind end and a clitoris-like phallus), the testis was located abdominally, and germ cell development was severely disrupted, which was similar to a human complete androgen insensitivity syndrome or testicular feminization mouse. However, the process of spermatogenesis is highly dependent on autocrine and paracrine communication among testicular cell types, and the disruption of AR throughout an experimental animal cannot answer the question about how AR in each type of testicular cell can play roles in the process of spermatogenesis. In this review, we provide new insights by comparing the results of cell-specific AR knockout in germ cells, peritubular myoid cells, Leydig cells, and Sertoli cells mouse models that were generated by different laboratories to see the consequent defects in spermatogenesis due to AR loss in different testicular cell types in spermatogenesis. Briefly, this review summarizes these results as follows: 1) the impact of lacking AR in Sertoli cells mainly affects Sertoli cell functions to support and nurture germ cells, leading to spermatogenesis arrest at the diplotene primary spermatocyte stage prior to the accomplishment of first meiotic division; 2) the impact of lacking AR in Leydig cells mainly affects steroidogenic functions leading to arrest of spermatogenesis at the round spermatid stage; 3) the impact of lacking AR in the smooth muscle cells and peritubular myoid cells in mice results in similar fertility despite decreased sperm output as compared to wild-type controls; and 4) the deletion of AR gene in mouse germ cells does not affect spermatogenesis and male fertility. This review tries to clarify the useful information regarding how androgen/AR functions in individual cells of the testis. The future studies of detailed molecular mechanisms in these in vivo animals with cell-specific AR knockout could possibly lead to useful insights for improvements in the treatment of male infertility, hypogonadism, and testicular dysgenesis syndrome, and in attempts to create safe as well as effective male contraceptive methods.

The maturation of sperm motility in the epididymis and vas deferens of the vervet monkey, Cercopithecus aethiops

Among the diverse facets of sperm maturation, changes in motility are conspicuous and hence studies of sperm kinematics might provide good indices for sperm maturation. Accordingly, the maturation of sperm motility in the epididymis and vas deferens of the vervet monkey, Cercopithecus aethiops, was assessed using a computer-aided sperm motility analysis system. The results revealed clear trends in the development of both sperm motility per se and in the movement characteristics of motile spermatozoa from different regions of the epididymis, the vas deferens and the ejaculate, reflecting maturational changes associated with the attainment of functional motility and fertility. Motion of spermatozoa from the caput epididymis was sluggish and irregular. As the spermatozoa moved through the corpus epididymis, motility increased sharply, and continued to improve through the cauda epididymis and vas deferens. Despite the high proportion of motile cells, full maturation of motion capabilities was not completed in spermatozoa from the corpus epididymis. Only once spermatozoa had reached the cauda epididymis and vas deferens did they attain their full vigour, and swam rapidly (greater VCL, VSL and VAP) with straightline trajectories (greater LIN, WOB and STR; lower ALH, MAD and CURV). After acquiring their maximal percentage motility and progressive velocity in the cauda epididymis and vas deferens, a slight decline in motility and vigour occurred in ejaculated spermatozoa, and was possibly associated with the ageing of stored spermatozoa. The results from this investigation have revealed clear trends in the maturation of the motility of vervet monkey spermatozoa during their transit through the epididymis and vas deferens and final emergence in the ejaculate, and have provided crucial baseline information on the reproductive physiology of this potentially valuable biomedical model to serve as a reference for future studies in reproductive toxicology.