Endocrine, paracrine and autocrine regulation of testicular steroidogenesis

α-Linolenic acid promotes testosterone synthesis by improving mitochondrial function in primary rooster Leydig cells

The present study aimed to investigate the direct effects of α-Linolenic acid (ALA) on the in vitro production of testosterone and the expression of key enzymes and proteins related to steroidogenesis in Leydig cells of roosters.

METHODS

Purified primary Leydig cells isolated from 65-week-old roosters were purified and treated with different concentrations of ALA treatments: (0 μm/L [control], solvent control group (DMSO), 20 μM/L, 40 μM/L, and 80 μM/L) and cell counting-8 (CCK-8) for cell viability assay, Enzyme-linked immunosorbent assay (ELISA) kit for the determination of testosterone in cell supernatants, quantitative (real-time) PCR, and analysis of activities of antioxidants catalase (CAT), superoxide dismutase (SOD) and malondialdehyde (MDA), evaluation of mitochondrial membrane potential, pro- and anti-apoptotic proteins/genes Bcl-2, Bcl-2-associated X protein (Bax), apoptosis-inducing factor (AIF) were done respectively.

RESULTS

Our results showed that ALA significantly increased testosterone secretion in primary rooster Leydig cells (P < 0.05), and 40 μM/L is the optimal dose. Leydig cells supplemented with ALA (20, 40, 80 μM) increased the expression of key enzymes and proteins 3β-hydroxysteroid dehydrogenase (3β-HSD), steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (P450scc) concerning steroidogenesis, enhanced antioxidant capability, improved mitochondrial biogenesis, and markedly improved the mitochondrial membrane potential (P < 0.05). Furthermore, the expression of the apoptosis-suppressive gene Bcl-2 was significantly increased, but Bax and AIF expression was decreased in the ALA group compared to that in the control group (P < 0.05).

CONCLUSION

ALA promoted testosterone production, enhanced steroidogenic enzyme expression, improved mitochondrial function, and antioxidant capacity, and reduced apoptosis in primary rooster Leydig cells, with 40 μM/L identified as the optimal concentration.

In Vitro Generation of Haploid Germ Cells from Human XY and XXY Immature Testes in a 3D Organoid System

Increasing survival rates of children following cancer treatment have resulted in a significant population of adult survivors with the common side effect of infertility. Additionally, the availability of genetic testing has identified Klinefelter syndrome (classic 47,XXY) as the cause of future male infertility for a significant number of prepubertal patients. This study explores new spermatogonia stem cell (SSC)-based fertility therapies to meet the needs of these patients. Testicular cells were isolated from cryopreserved human testes tissue stored from XY and XXY prepubertal patients and propagated in a two-dimensional culture. Cells were then incorporated into a 3D human testicular organoid (HTO) system. During a 3-week culture period, HTOs maintained their structure, viability, and metabolic activity. Cell-specific PCR and flow cytometry markers identified undifferentiated spermatogonia, Sertoli, Leydig, and peritubular cells within the HTOs. Testosterone was produced by the HTOs both with and without hCG stimulation. Upregulation of postmeiotic germ cell markers was detected after 23 days in culture. Fluorescence in situ hybridization (FISH) of chromosomes X, Y, and 18 identified haploid cells in the in vitro differentiated HTOs. Thus, 3D HTOs were successfully generated from isolated immature human testicular cells from both euploid (XY) and Klinefelter (XXY) patients, supporting androgen production and germ cell differentiation in vitro.

Temporal Changes in the Local Expression of Central Hormone-Regulating Factors in Rat Testis

Present study aimed to investigate the temporal changes in expression of some reproductive hormones in testis, originally found in hypothalamus and pituitary. Rats were sacrificed on postnatal day 23 (PND23; immature), pubertal (PND53) and PND 81 (young adult). The testicular RNAs were extracted, and semi-quantitative PCRs for gonadotropin-releasing hormone (GnRH), kisspeptin 1 (KiSS1), pituitary adenylate cyclase-activating polypeptide (PACAP), LH subunits and LH receptor were performed. Transcript levels of GnRH and KiSS1 at PND23 were significantly higher than levels of PND53 and PND81 (p <0.001). PACAP mRNA level at PND23 was significantly lower than those of PND53 and PND81 (p <0.001). The mRNA levels of both testis type and pituitary type luteinizing hormone β subunit (tLHβ and pLHβ, respectively) at PND23 were significantly lower than levels of PND53 and PND81 (p <0.001). The mRNA level of glycoprotein hormone common alpha subunit (Cgα) at PND23 was significantly lower than those of PND53 and PND81 (p <0.001). Present study revealed the intratesticular expression of KiSS1 and GnRH showed a very similar trend while the expression of PACAP in the testis showed reversed pattern. The expressions of LHβ subunits (tLHβ and pLHβ) were very low during immature stage then increased significantly during puberty and early adulthood. Our attempt to study the local role(s) of intratesticular factors will be helpful to achieve precise understanding on the testis physiology and pathology.

Effect of Temperature on the Development of Stages of Spermatogenesis and the Functionality of Sertoli Cells In Vitro

Spermatogenesis is the process of proliferation and differentiation of spermatogonial cells to meiotic and post-meiotic stages and sperm generation. Normal spermatogenesis occurs in vivo at 34 °C to 35 °C, and high temperatures are known to cause male infertility. The aim of the present study was to examine the effect of temperature (35 °C compared to 37 °C) on the viability/apoptosis of developed cells, on the development of different stages of spermatogenesis in 3D in vitro culture conditions, and the functionality of Sertoli cells under these conditions. We used isolated cells from seminiferous tubules of sexually immature mice. The cells were cultured in methylcellulose (as a three-dimensional (3D) in vitro culture system) and incubated in a CO2 incubator at 35 °C or 37 °C. After two to six weeks, the developed cells and organoids were collected and examined for cell viability and apoptosis markers. The development of different stages of spermatogenesis was evaluated by immunofluorescence staining or qPCR analysis using specific antibodies or primers, respectively, for cells at each stage. Factors that indicate the functionality of Sertoli cells were assessed by qPCR analysis. The developed organoids were examined by a confocal microscope. Our results show that the percentages and/or the expression levels of the developed pre-meiotic, meiotic, and post-meiotic cells were significantly higher at 35 °C compared to those at 37 °C, including the expression levels of the androgen receptor, the FSH receptor, transferrin, the androgen-binding protein (ABP), and the glial-derived nerve growth factor (GDNF) which were similarly significantly higher at 35 °C than at 37 °C. The percentages of apoptotic cells (according to acridine orange staining) and the expression levels of BAX, FAS, and CASPAS 3 were significantly higher in cultures incubated at 37 °C compared to those incubated at 35 °C. These findings support the in vivo results regarding the negative effect of high temperatures on the process of spermatogenesis and suggest a possible effect of high temperatures on the viability/apoptosis of spermatogenic cells. In addition, increasing the temperature in vitro also impaired the functionality of Sertoli cells. These findings may deepen our understanding of the mechanisms behind optimal conditions for normal spermatogenesis in vivo and in vitro.

Steroid hormone signaling: multifaceted support of testicular function

Embryonic development and adult physiology are dependent on the action of steroid hormones. In particular, the reproductive system is reliant on hormonal signaling to promote gonadal function and to ensure fertility. Here we will describe hormone receptor functions and their impacts on testicular function, focusing on a specific group of essential hormones: androgens, estrogens, progesterone, cortisol, and aldosterone. In addition to focusing on hormone receptor function and localization within the testis, we will highlight the effects of altered receptor signaling, including the consequences of reduced and excess signaling activity. These hormones act through various cellular pathways and receptor types, emphasizing the need for a multifaceted research approach to understand their critical roles in testicular function. Hormones exhibit intricate interactions with each other, as evidenced, for example, by the antagonistic effects of progesterone on mineralocorticoid receptors and cortisol's impact on androgens. In light of research findings in the field demonstrating an intricate interplay between hormones, a systems biology approach is crucial for a nuanced understanding of this complex hormonal network. This review can serve as a resource for further investigation into hormonal support of male reproductive health.

Relaxin (a regulatory-peptide) enhances cryotolerance, fertility potential and plasma reproductive hormones of Nili Ravi buffalo (Bubalus bubalis) during low breeding season

This study investigated the beneficial effects of relaxin on cryotolerance of buffalo spermatozoa and reproductive hormones during low breeding season. Collected semen was diluted in five aliquots with relaxin addition (0.25 mg/mL, 0.50 mg/mL, 0.75 mg/mL, 1 mg/mL, and control). After gentle dilution (37°C), cooling (4°C, 2 h), equilibration (4°C, 4 h), and packaging (straws, polyvinyl French, 0.5 mL), frozen (cell freezer), and thawed (37°C, 30 s) for analysis. Blood samples were collected at different time intervals i.e., -60, -30 and 0 min (pre-dose) and 30, 60, 90, 120 and 150 min (post-dose) from a jugular vein. This study manifest that adding relaxin (1 mg/ mL) in freezing medium ameliorates sperm motility, functionality (%), and seminal plasma total antioxidant capacity (TAC, μM/L) than control during low breeding season. Furthermore, we found that relaxin supplementation at 1 mg/mL significantly improves seminal plasma ATP concentrations (nmol/million) than control, 0.25 mg/mL, and 0.50 mg/mL, and fertility (control, and 0.75 mg/mL). Further, relaxin injection significantly improves plasma T, LH and IGF-1 levels (150 and 120 min vs. -60, and - 30), and FSH, KP, and GnRH concentrations (150 min vs. -60), during low breeding season. Taken together, this study revealed that relaxin ameliorates motility, functionality, and fertility of buffalo spermatozoa. Moreover, relaxin injection (1 mg/mL) improves essential reproductive hormones levels in buffalo signifying its importance in the field of reproductive physiology. Further studies are required to determine the exact mechanism of action of relaxin in enhancing semen quality, fertility and reproductive hormones.

Organotypic Rat Testicular Organoids for the Study of Testicular Maturation and Toxicology

An in vitro system to study testicular maturation in rats, an important model organism for reproductive toxicity, could serve as a platform for high-throughput drug and toxicity screening in a tissue specific context. In vitro maturation of somatic cells and spermatogonia in organ culture systems has been reported. However, this has been a challenge for organoids derived from dissociated testicular cells. Here, we report generation and maintenance of rat testicular organoids in microwell culture for 28 days. We find that rat organoids can be maintained in vitro only at lower than ambient O₂ tension of 15% and organoids cultured at 34°C have higher somatic cell maturation and spermatogonial differentiation potential compared to cultures in 37°C. Upon exposure to known toxicants, phthalic acid mono-2-ethylhexyl ester and cadmium chloride, the organoids displayed loss of tight-junction protein Claudin 11 and altered transcription levels of somatic cell markers that are consistent with previous reports in animal models. Therefore, the microwell-derived rat testicular organoids described here can serve as a novel platform for the study of testicular cell maturation and reproductive toxicity in vitro.

Carnosine Remedial Effect on Fertility of Male Rats Receiving Cyclophosphamide, Hydroxydaunomycin, Oncovin and Prednisone (CHOP)

Chemotherapeutic agents can impair gonadal function triggering infertility. Here, we probed the properties of carnosine as an antioxidant in reproductive disorders caused by the combination of cyclophosphamide, hydroxydaunomycin (doxorubicin), oncovin (vincristine) and prednisone (CHOP); this combination is mostly used in treating non-Hodgkin lymphoma. Animals were distributed into four groups: Group I was the control. Group II received carnosine (250mg kg day^-1 , i.p.); Group III received CHOP: cyclophosphamide (27 mg/kg/cycle), doxorubicin (1.8 mg/kg/cycle) and vincristine (0.05 mg/kg /cycle) by i.p. plus oral prednisone (1.47 mg kg^-1  day^-1 /cycle) for five days. Group IV received carnosine plus CHOP. The study involved 4 cycles each of 3 weeks. Also, we explored the effect of combining carnosine with CHOP on the development of solid Ehrlich carcinoma in mice. CHOP lowered genitals weight, sperm count and motility, testicular function marker enzymes, serum testosterone level and gene expression of 3β-hydroxysteroid dehydrogenase, 17β-hydroxysteroid dehydrogenase and steroidogenic acute regulatory protein. Furthermore, CHOP elevated testicular oxidative stress, serum follicle-stimulating hormone, luteinising hormone and triggered DNA damage. Morphometric and histopathological examinations of testicular tissues buttressed the biochemical results. Importantly, administration of carnosine ameliorated CHOP-induced alterations without diminishing CHOP's antineoplastic action. These results indicated that carnosine may ameliorate reproductive disorders induced by CHOP.

The Distribution Profile of Glycoconjugates in the Testis of Brown-Banded Bamboo Shark (Chiloscyllium punctatum) by Using Lectin Histochemistry

The testis of bamboo shark is characterized by diametric development leading to zonation architecture. Here, we investigated the staining pattern of 12 lectins in 6 groups of differential binding specificities within the germ, somatic, and interstitial cells of each zone. The neutral mucopolysaccharides appeared in the interstitial tissue in all the zones and became more significant in the spermatozoal–Sertoli cell junction. The cellular localization of the lectins varies in testicular zones and cell types. There was a gradual increase in glycosylation toward the degenerative zone. The increased intensity of most lectins in the interstitial cells indicates the association of glycoconjugates in their androgen-secreting activity. Statistical analyses showed a significant correlation between the groups of lectins and each lectin used, stronger response to lectins in the interstitial cells (ICs) than other cell types. Moreover, the response to glucosamine (GlcNAc), galactosamine (GalNAc), and fucose tended to be higher than glucose and galactose. Furthermore, the intensity of response was increased toward the degenerative zone. In addition, we can use peanut agglutinin (PNA) as an acrosomal marker in combination with other marker proteins for studying shark spermatogenesis. These findings refer to the crucial role of glycoconjugates in spermatogenesis in the bamboo shark testis.

Chemotherapeutic Potential of Epimedium brevicornum Extract: The cGMP-Specific PDE5 Inhibitor as Anti-Infertility Agent Following Long-Term Administration of Tramadol in Male Rats

Epimedium brevicornum Maxim (EbM) is a well-known Chinese herb that has been widely used for the treatment of several diseases. The main purpose of this study is to examine the role of Epimedium brevicornum extract in certain andrological parameters in rats as a natural modulator for adverse viewpoints associated with chronic administration of tramadol (TAM). Fifty rats were categorized into five groups. Untreated rats were known as Group I, whereas rats in Groups II and III were administered 2.43 g/kg/day of E. brevicornum extract and 50 mg/kg/day of TAM for 130 consecutive days, respectively. Both of Groups IV and V were administered TAM for 65 successive days, followed by concomitant use of both drugs for another 65 days, with the E. brevicornum extract at doses of 0.81 and 2.43 g/kg/day, respectively. TAM showed an injurious effect on sperm attributes, serum hormones, tissue malondialdehyde, superoxide dismutase, and nitric oxide. Elevation of the apoptotic marker Bax and a reduction of Bcl2 were recorded. Histopathological abnormalities have been reported in rat testicles. Rats treated with E. brevicornum extract with TAM showed an improvement in all the parameters tested. It could be presumed that E. brevicornum extract plus TAM exhibits a promising effect on the enhancement of male anti-infertility effects.

Defective spermatogenesis and testosterone levels in kinase suppressor of Ras1 (KSR1)-deficient mice

The aim of this study was to clarify the role of the protein kinase suppressor of Ras1 (KSR1) in spermatogenesis. Spermatogenesis in ksr1 -/- mice was studied in testicular tissue and epididymal spermatozoa by light and transmission electron microscopy and by immunofluorescence using antibodies to ghrelin and 3β-hydroxysteroid dehydrogenase (3β-HSD). Blood testosterone levels were also assessed. ksr1 -/- mice showed reduced epididymal sperm concentration and motility as compared with wild- type (wt) mice. Testis tissue from ksr1 -/- mice revealed a prevalent spermatogenetic arrest at the spermatocyte stage; the interstitial tissue was hypertrophic and the cytoplasm of the Leydig cells was full of lipid droplets. Ghrelin signal was present in the seminiferous tubules and, particularly, in the interstitial tissue of wt mice; however, in ksr1 -/- mice ghrelin expression was very weak in both the interstitial tissue and tubules. On the contrary, the signal of 3β-HSD was weak in the interstitial tissue of wt and strong in ksr1 -/- mice. Testosterone levels were significantly increased in the blood of ksr1 -/- mice (P <0.05) as compared with wt. The results obtained reveal the importance of the KSR scaffold proteins in the spermatogenetic process. The study of the molecular mechanisms associated with spermatogenetic defects in a mouse model is essential to understand the factors involved in human spermatogenesis.

Effects of Treatment with Nauclea latifolia Root Decoction on Sexual Behavior and Reproductive Functions in Male Rabbits

Nauclea latifolia is used in traditional medicine for the treatment of male reproductive diseases. Despite its vast uses, its effects on the male reproductive system have not been scientifically proven. This study aimed to investigate the effects of Nauclea latifolia root decoction on sexual behavior and functions in male rabbits. Twenty-four male rabbits were divided into four groups: The first group received daily distilled water orally. The second, third, and fourth groups were orally treated with 100, 200, and 400 mg/kg body weight of Nuclea latifolia root, respectively. Sexual behavior parameters were carried out on weeks 1, 2, and 3 of the study. Testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were measured from the serum, while the testes tissue samples were used for antioxidant and histopathological examinations. Treatment with 200 and 400 mg/kg body weight resulted in significantly (p < .05) increased frequencies of mounting and intromission. In addition, the ejaculation latency was significantly prolonged (p < .05). The latencies of mounting and intromission were significantly decreased (p < .05), whereas ejaculation frequency increased. Serum testosterone, FSH, and LH increased significantly (p < .05) after treatment with Nuclea latifolia. There was an increase in epididymal sperm counts at 200 and 400 mg/kg body weight doses compared to the control. The extract also increased sperm motility and viability and improved testicular oxidative status. Histological examination revealed an increase in germinal layer thickness. The present study suggests that treatment with N. latifolia improves male sexual function and fertility and protects the testes from oxidative damage.

Vascular endothelial growth factor (VEGF-A) and fibroblast growth factor (FGF-2) as potential regulators of seasonal reproductive processes in male European bison (Bison bonasus, Linnaeus 1758)

Growth factors: vascular endothelial growth factor A (VEGF-A) and fibroblast growth factor (FGF-2) were reported to affect normal physiological reproductive processes in human, domestic and free living animals. Moreover, some reports suggest that VEGF-A and FGF-2 may be directly involved in the control of the annual reproductive cycle of seasonally breeding animals but detailed knowledge is still missing. Our study aimed to demonstrate the expression of mRNA and protein for both factors in the tissues of testis and epididymis (caput, corpus, cauda) at different periods of the year (March, June, November, December) in European bison as a model of seasonally breeding animal. Results suggest, that VEGF-A expression was more pronounced in testis than in epididymis and the highest expression was noted in December and June. Surprisingly, the highest protein accumulation was observed in June at the same level in all tissues analyzed. On the other hand, the highest FGF-2 mRNA expression was noted in testis in June and in epididymis in March. However, no differences in protein expression of FGF-2 were found between analyzed groups. The results indicate that both factors are necessary for proper functioning of the reproductive system and their levels differ seasonally. Perhaps, it is linked to increased need of these factors in the testis as well as epididymis during preparation for the reproductive functions. Moreover, VEGF-A and FGF-2 not only may regulate reproductive functions by affecting vascularization and cell nutrition, but it also may be possible that they possess protective functions by stabilizing the reproductive cells. Therefore, obtained results provide new insight into mechanisms underlying seasonal breeding of the male European bison.

Testosterone-Dependent miR-26a-5p and let-7g-5p Act as Signaling Mediators to Regulate Sperm Apoptosis via Targeting PTEN and PMAIP1

Recent evidence suggests that testosterone deficiency can dramatically decrease the quality of sperm. MicroRNAs (miRNAs) are conserved mediators of post-transcriptional gene regulation in eukaryotes. However, the systemic regulation and function of miRNAs in sperm quality decline induced by testosterone deficiency has not been investigated. Here, we found that the sperm apoptosis was significantly enhanced and the sperm motility was dramatically decreased in hemicastrated pigs. We then used small RNA sequencing to detect miRNA profiles of sperm from pigs with prepubertal hemicastration (HC) and compared them with control libraries. We identified 16 differentially expressed (DE) miRNAs between the sperm of prepubertal HC and control (CT) pigs. Functional enrichment analysis indicated that the target genes of these DE miRNAs were mainly enriched in apoptosis-related pathways including the p53, mitogen-activated protein kinase (MAPK), and mammalian target of rapamycin (mTOR) pathways. Furthermore, gain- and loss-of-function analyses demonstrated potential anti-apoptotic effects of the DE miRNAs miR-26a-5p and let-7g-5p on sperm cells. The luciferase reporter assay confirmed that PTEN and PMAIP1 are targets of miR-26a-5p and let-7g-5p, respectively. Spearman’s correlation analysis revealed significantly positive correlations between the sperm and its corresponding seminal plasma exosomes regarding the miRNA expression levels. In conclusion, testosterone deficiency-induced changes in the miRNA components of seminal plasma exosomes secreted by the genital tract may partially elucidate sperm miRNAome alterations, which are further responsible for the decline of sperm motility.

Effect of gasoline fumes on reproductive function in male albino rats

The increase in the frequency of exposure to gasoline fumes and the growing incidence of infertility among humans has been a major concern and subject of discussion over the years in Nigeria. We therefore present the reproductive effect of gasoline fumes on inhalation exposure in 40 male albino rats. The rats were randomized into five experimental treatments (T) with eight rats per treatment. T1 (control) was exposed to distilled water while T2, T3, T4, and T5 were exposed to gasoline fumes in exposure chambers for 1, 3, 5, and 9 h daily respectively for 12 weeks. Serum level of testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, oxidative stress markers in the testicular tissue, epididymal sperm health assessment, and testicular histopathology of the rats were used as a diagnostic marker of reproductive dysfunction. Significant (p < 0.05) alterations in the levels of all the reproductive hormones and oxidative stress markers assayed were observed in rats exposed to gasoline fume. Significant reductions (p < 0.05) in sperm count and percentage motility in the exposed rats were observed. Significant (p < 0.05) increased in abnormal sperm cells characterized by damaged head, bent tail, damaged tail, and without head were also observed in the exposed rats. Histopathologically, severe degenerative testicular architectural lesions characterized by alterations in all the generations of sperm cells and reduction of interstitial cells were seen in the exposed rats. Gasoline fume is thus said to interfere with spermatogenesis and impair fertility in male gonad.

Three-dimensional testicular organoid: a novel tool for the study of human spermatogenesis and gonadotoxicity in vitro

Existing methods for evaluating the potential gonadotoxicity of environmental agents and pharmaceutical compounds rely heavily on animal studies. The current gold standard in vivo functional assays in animals are limited in their human predictive capacity. In addition, existing human two-dimensional in vitro models of testicular toxicity do not accurately reflect the in vivo situation. A more reliable testicular in vitro model system is needed to better assess the gonadotoxic potential of drugs prior to progression into clinical trials. The overall goal of this study was to develop a three-dimensional (3D) in vitro human testis organoid culture system for use as both a predictive first tier drug-screening tool and as a model of human testicular function. Multicellular human testicular organoids composed of Spermatogonial Stem Cells, Sertoli, Leydig and peritubular cells were created and evaluated over time for morphology, viability, androgen production and ability to support germ cell differentiation. Enzyme-linked immunosorbent assay measurements confirmed that the organoids produced testosterone continuously with and without hCG stimulation. Upregulation of postmeiotic genes including PRM1 and Acrosin, detected by quantitative-PCR, digital PCR and Immunofluorescence, indicated the transition of a small percentage of diploid to haploid germ cells. As a novel screening tool for reproductive toxicity, 3D organoids were exposed to four chemotherapeutic drugs, and they responded in a dose-dependent manner and maintained IC50 values significantly higher than 2D cultures. This 3D human testis organoid system has the potential to be used as a novel testicular toxicity-screening tool and in vitro model for human spermatogenesis.

Differential expression of microRNAs in luteinising hormone-treated mouse TM3 Leydig cells

Testosterone is primarily produced by Leydig cells of the mammalian male gonads. The cellular functions of Leydig cells are regulated by the hypothalamus-pituitary-gonad axis, whereas the microRNA (miRNA) changes of LH-treated Leydig cells are unknown. Mouse TM3 Leydig cells were treated with LH, and deep sequencing showed that 29 miRNAs were significantly different between two groups (fold change of >1.5 or <0.5, p < .05), of which 27 were upregulated and two were downregulated. The differential expression of miR-29b-3p, miR-378b, miR-193b and miR-3695 was confirmed by quantitative real-time polymerase chain reaction. Bioinformatic analysis revealed that miRNAs regulated a large number of genes with different functions. Pathway analysis indicated that miRNAs were involved in the Wingless and INT-1, adenosine 5'-monophosphate-activated protein kinase, NF-kappa B and Toll-like receptor signalling pathways. Results showed that miRNAs might be involved in the regulation of LH to Leydig cells.

Steroidogenic fate of the Leydig cells that repopulate the testes of young and aged Brown Norway rats after elimination of the preexisting Leydig cells

The capacity of Brown Norway rat Leydig cells to produce testosterone (T) decreases with aging. In a previous study, we reported that a new generation of Leydig cells can be restored in both young and old rat testes after a single injection of ethane dimethanesulfonate (EDS), and that the abilities of the new Leydig cells in young and old rats to produce T were equivalent. Our objective herein was to compare the steroidogenic fate of the new Leydig cells over time. Young (3 month-old) and old (18 month-old) rats were injected with EDS to eliminate the existing Leydig cells. Ten weeks after EDS, Leydig cells had been restored and T production by the new Leydig cells isolated from young and old rat testes was equivalent. Thirty weeks after EDS treatment of young rats, the ability of the new Leydig cells to produce T had not diminished from 10 weeks post-EDS. In contrast, at 30 weeks post-EDS, T production by new cells in old rat testes was reduced significantly from the 10-week level. Serum T levels at 10 and 30 weeks were consistent with Leydig cell T production. Serum LH levels did not differ in any group. Thus, although the Leydig cells restored to both young and old rats after EDS initially produced T at high, equivalent levels, the cells in the old testes did not maintain this ability. These results suggest that: 1) the cells from which new populations of Leydig cells are derived may differ depending upon the age of the rat; and/or 2) factors extrinsic to the new Leydig cells in young and old testes differ, and it is these differences that are responsible for reductions in T by the newly formed Leydig cells in the testes of old rats.

Vitamin D and male reproduction

Vitamin D is a versatile signalling molecule with a well-established role in the regulation of calcium homeostasis and bone health. The spectrum of vitamin D target organs has expanded and the reproductive role of vitamin D is highlighted by expression of the vitamin D receptor (VDR) and enzymes that metabolize vitamin D in testis, male reproductive tract and human spermatozoa. The expression levels of VDR and CYP24A1 in human spermatozoa serve as positive predictive markers of semen quality, and VDR mediates a nongenomic increase in intracellular calcium concentration that induces sperm motility. Interestingly, functional animal models show that vitamin D is important for estrogen signalling and sperm motility, while cross-sectional studies support the positive association between serum 25-hydroxyvitamin D level and sperm motility in both fertile and infertile men. Expression of VDR and enzymes that metabolize vitamin D in fetal testis indicates a yet unknown role during development, which may be extrapolated from invasive testicular germ cell tumours where 1α,25-dihydroxyvitamin D induces a mesodermal differentiation of the pluripotent testicular cancer cells. Taken together, vitamin D signalling has a positive effect on semen quality, increases estrogen responsiveness and differentiates germ cell tumours. Future studies are needed to determine when 1α,25-dihydroxyvitamin D acts in a paracrine manner and whether systemic changes, which are subject to pharmacological modulation, could influence male reproductive function.

Nicotine alters male reproductive hormones in male albino rats: The role of cessation

OBJECTIVES

The use of nicotine through smoking remains a serious health problem. It has been associated with reduced fertility, although the mechanism responsible is still unclear. The present study was designed to investigate whether nicotine-induced infertility is associated with altered male reproductive hormones in male albino rats.

MATERIALS AND METHODS

Forty male rats were divided equally into five groups and treated orally for thirty days. Group I, which served as the control received 0.2 ml/kg normal saline, Group II and III received 0.5 mg/kg (low dose) and 1.0 mg/kg (high dose) body weight of nicotine, respectively. The fourth and fifth groups were gavaged with 0.5 mg/kg and 1.0 mg/kg body weight of nicotine but were left untreated for another 30 days. These groups served as the recovery groups. Serum was analyzed for testosterone, luteinizing hormone (LH), follicle stimulating hormones (FSH), and prolactin using radioimmunoassay.

RESULTS

Results showed that nicotine administration significantly decreased (P < 0.05) testosterone in the low and high treated groups and FSH in the high dose treated group when compared with the control group. There was a significant increase (P < 0.05) in mean LH and prolactin level in the high dose treated group when compared with the control. However, the values of the recovery groups were comparable with the control.

CONCLUSION

The findings in this study suggest that nicotine administration is associated with distorted reproductive hormones in male rats although ameliorated by nicotine cessation. It is plausible that the decreased testosterone level is associated with testicular dysfunction rather than a pituitary disorder.

Androgen receptor signalling in peritubular myoid cells is essential for normal differentiation and function of adult Leydig cells

Testosterone synthesis depends on normal Leydig cell (LC) development, but the mechanisms controlling this development remain unclear. We recently demonstrated that androgen receptor (AR) ablation from a proportion of testicular peritubular myoid cells (PTM-ARKO) did not affect LC number, but resulted in compensated LC failure. The current study extends these investigations, demonstrating that PTM AR signalling is important for normal development, ultrastructure and function of adult LCs. Notably, mRNAs for LC markers [e.g. steroidogenic factor 1 (Nr5a1), insulin-like growth factor (Igf-1) and insulin-like factor 3 (Insl3)] were significantly reduced in adult PTM-ARKOs, but not all LCs were similarly affected. Two LC sub-populations were identified, one apparently 'normal' sub-population that expressed adult LC markers and steroidogenic enzymes as in controls, and another 'abnormal' sub-population that had arrested development and only weakly expressed INSL3, luteinizing hormone receptor, and several steroidogenic enzymes. Furthermore, unlike 'normal' LCs in PTM-ARKOs, the 'abnormal' LCs did not involute as expected in response to exogenous testosterone. Differential function of these LC sub-populations is likely to mean that the 'normal' LCs work harder to compensate for the 'abnormal' LCs to maintain normal serum testosterone. These findings reveal new paracrine mechanisms underlying adult LC development, which can be further investigated using PTM-ARKOs.

Effects of short-term hyper- and hypoprolactinaemia on hormones of the pituitary, gonad and -thyroid axis and on semen quality in male Beagles

Effects of a short-term hyper- and hypoprolactinaemia on serum concentrations of LH, testosterone and semen quality in six male Beagles were investigated. Blood samples were collected at 3-day intervals for 12 weeks. The time span was divided into five 3-week periods: pre-treatment, metoclopramide (MCP) treatment (0.2 mg/kg orally three times daily), cabergoline (CAB) treatment (5 microg/kg orally once daily), post-treatment 1 and post-treatment 2. In the latter, only semen characteristics were evaluated. Semen parameters were analyzed once per week during the whole 15-week investigation time. At the end of each period, the effects of a single intravenous injection of thyrotropin-releasing hormone (TRH; 10 microg/kg) on the secretion of prolactin (PRL), LH, testosterone, thyroid-stimulating hormone and thyroxine (T4) were investigated. Pre-treatment serum PRL concentration increased under MCP (p < 0.05), followed by a decrease under CAB administration (p < 0.05). Luteinizing hormone and testosterone concentrations were not affected. Except for straight-line sperm velocity, semen quality did not differ between collection periods. A single iv TRH injection induced a significant PRL increase at 20 min in all experimental periods except during CAB treatment. Luteinizing hormone and testosterone did not show clear TRH-related changes. Basic T4 levels were significantly reduced after CAB treatment (p < 0.05). The results of the present study demonstrate that MCP-induced short-term hyperprolactinaemia in male beagles does not seriously affect the hypothalamo-pituitary axis and semen quality.

Deprival of testicular innervation induces apoptosis of Leydig cells via caspase-8-dependent signaling: a novel survival pathway revealed

Leydig cells are the primary source of testosterone in adult males. Recently, a growing body of evidence has shown that testicular innervation functions as a major regulator in Leydig cell steroidogenesis. The question then arises whether this novel regulatory pathway also plays an important role in other biological behaviors of this cell type. In the present study, we selectively resected the superior spermatic nerves (SSNs) or the inferior spermatic nerves (ISNs) to investigate the effects of testicular denervation on survival of Leydig cells. After testicular denervation, Leydig cells displayed morphological characteristics of apoptosis, such as chromatin condensation, cell shrinkage and apoptotic body formation. Flow cytometry combined with TUNEL labeling demonstrated dramatic and persistent apoptosis of Leydig cells in the denervated testes 14 and 21 days after operation. Meanwhile, serum T concentrations in the SSN- or ISN-denervated rats dramatically decreased on day 14 and declined further on day 21. Plasma LH levels underwent a remarkable rise, while serum FSH levels remained unchanged. Immunofluorescent staining and flow cytometry further demonstrated that testicular denervation activated caspase-3 and caspase-8, but not caspase-9 in Leydig cells. Our data indicate that testicular innervation functions as an important survival factor for Leydig cells in vivo.

Opposing effects of D-aspartic acid and nitric oxide on tuning of testosterone production in mallard testis during the reproductive cycle

D-Aspartic acid (D-Asp) and nitric oxide (NO) play an important role in tuning testosterone production in the gonads of male vertebrates. In particular, D-Asp promotes either the synthesis or the release of testosterone, whereas NO inhibits it. In this study, we have investigated for the first time in birds the putative effects of D-Asp and NO on testicular testosterone production in relation to two phases of the reproductive cycle of the adult captive wild-strain mallard (Anas platyrhynchos) drake. It is a typical seasonal breeder and its cycle consists of a short reproductive period (RP) in the spring (April-May) and a non reproductive period (NRP) in the summer (July), a time when the gonads are quiescent. The presence and the localization of D-Asp and NO in the testis and the trends of D-Asp, NO and testosterone levels were assessed during the main phases of the bird's reproductive cycle. Furthermore, in vitro experiments revealed the direct effect of exogenously administered D-Asp and NO on testosterone steroidogenesis.

METHODS

By using immunohistochemical (IHC) techniques, we studied the presence and the distributional pattern of D-Asp and NO in the testes of RP and NRP drakes. D-Asp levels were evaluated by an enzymatic method, whereas NO content, via nitrite, was assessed using biochemical measurements. Finally, immunoenzymatic techniques determined testicular testosterone levels.

RESULTS

IHC analyses revealed the presence of D-Asp and NO in Leydig cells. The distributional pattern of both molecules was in some way correlated to the steroidogenic pathway, which is involved in autocrine testosterone production. Indeed, whereas NO was present only during the NRP, D-Asp was almost exclusively present during the RP. Consistently, the high testosterone testicular content occurring during RP was coupled to a high D-Asp level and a low NO content in the gonad. By contrast, in sexually inactive drakes (NRP), the low testosterone content in the gonad was coupled to a low D-Asp content and to a relatively high NO level. Consequently, to determine the exogenous effects of the two amino acids on testosterone synthesis, we carried out in vitro experiments using testis sections deriving from both the RP and NRP. When testis slices were incubated for 60 or 120 min with D-Asp, testosterone was enhanced, whereas in the presence of L-Arg, a precursor of NO, it was inhibited.

CONCLUSION

Our results provide new insights into the involvement of D-Asp and NO in testicular testosterone production in the adult captive wild-strain mallard drake. The localization of these two molecules in the Leydig cells in different periods of the reproductive cycle demonstrates that they play a potential role in regulating local testosterone production.

Relative roles of inhibin B and sex steroids in the negative feedback regulation of follicle-stimulating hormone in men across the full spectrum of seminiferous epithelium function

CONTEXT AND OBJECTIVE

Our aim was to explore the relative roles of gonadal sex steroids and inhibin B in the regulation of FSH across a spectrum of seminiferous epithelium function.

SUBJECTS

The study included three groups: group I, healthy men (n = 31); group II, men with idiopathic hypogonadotropic hypogonadism receiving pulsatile GnRH (n = 12) selected to represent a spectrum of seminiferous tubular development, testicular size, and baseline inhibin B levels; and group III, men with functional anorchia (n = 3) receiving testosterone replacement.

DESIGN

Subjects were studied before and after 3 d of acute sex steroid withdrawal.

SETTING

The study was conducted at the Mallinckrodt General Clinical Research Center of Massachusetts General Hospital.

INTERVENTIONS

Acute biochemical castration was achieved using high-dose ketoconazole (groups I and II) or withdrawal of androgen therapy (group III).

MAIN OUTCOME MEASURES

The relationship between FSH and inhibin B in both normal and castrate sex steroid milieu was measured.

RESULTS

In both normal and castrate sex steroid milieus, there was a negative relationship between inhibin B and FSH, best described by a logarithmic model. Acute biochemical castration resulted in the most dramatic increases in FSH in men with the lowest baseline inhibin B levels.

CONCLUSIONS

We came to the following conclusions: 1) in the human male, inhibin B is the principal gonadal feedback regulator of FSH secretion unless seminiferous tubular function is severely compromised, and a logarithmic model best describes this relationship; and 2) sex steroid inhibition of FSH secretion is most apparent when serum inhibin B levels fall well below the normal range.

Effects of monobutyl and di(n-butyl) phthalate in vitro on steroidogenesis and Leydig cell aggregation in fetal testis explants from the rat: comparison with effects in vivo in the fetal rat and neonatal marmoset and in vitro in the human

BACKGROUND

Certain phthalates can impair Leydig cell distribution and steroidogenesis in the fetal rat in utero, but it is unknown whether similar effects might occur in the human.

OBJECTIVES

Our aim in this study was to investigate the effects of di(n-butyl) phthalate (DBP), or its metabolite monobutyl phthalate (MBP), on testosterone production and Leydig cell aggregation (LCA) in fetal testis explants from the rat and human, and to compare the results with in vivo findings for DBP-exposed rats. We also wanted to determine if DBP/MBP affects testosterone production in vivo in the neonatal male marmoset.

METHODS

Fetal testis explants obtained from the rat [gestation day (GD)19.5] and from the human (15-19 weeks of gestation) were cultured for 24-48 hr with or without human chorionic gonadotropin (hCG) or 22R-hydroxycholesterol (22R-OH), and with or without DBP/MBP. Pregnant rats and neonatal male marmosets were dosed with 500 mg/kg/day DBP or MBP.

RESULTS

Exposure of rats in utero to DBP (500 mg/kg/day) for 48 hr before GD21.5 induced major suppression of intratesticular testosterone levels and cytochrome P450 side chain cleavage enzyme (P450scc) expression; this short-term treatment induced LCA, but was less marked than longer term (GD13.5-20.5) DBP treatment. In vitro, MBP (10(-3) M) did not affect basal or 22R-OH-stimulated testosterone production by fetal rat testis explants but slightly attenuated hCG-stimulated steroidogenesis; MBP induced minor LCA in vitro. None of these parameters were affected in human fetal testis explants cultured with 10(-3) M MBP for up to 48 hr. Because the in vivo effects of DBP/MBP were not reproduced in vitro in the rat, the absence of MBP effects in vitro on fetal human testes is inconclusive. In newborn (Day 2-7) marmosets, administration of a single dose of 500 mg/kg MBP significantly (p = 0.019) suppressed blood testosterone levels 5 hr later. Similar treatment of newborn co-twin male marmosets for 14 days resulted in increased Leydig cell volume per testis (p = 0.011), compared with co-twin controls; this is consistent with MBP-induced inhibition of steroidogenesis followed by compensatory Leydig cell hyperplasia/hypertrophy.

CONCLUSIONS

These findings suggest that MBP/DBP suppresses steroidogenesis by fetal-type Leydig cells in primates as in rodents, but this cannot be studied in vitro.

Spontaneous hormonal variations in male cats following gonadectomy

The increased prevalence of obesity after neutering in cats is problematic in veterinary practice. Although many factors seem to be involved, the role of prolactin (PRL) and insulin-like growth factor-I (IGF-I), both implicated in adipose tissue development and glucose intolerance, should be considered. Seven male cats were castrated when 11 months old. Body weight was then recorded for 56 weeks and PRL, IGF-I and leptin assayed for 44 weeks. Body weight increased steadily but only significantly after 36 weeks. It stabilised after 44 weeks, and the cats then gained about 20% of their initial body weight. IGF-I increased rapidly and was significantly higher by week 3. PRL and leptin increased with initial peaks during the eighth and eleventh weeks, respectively. This study confirms that castration rapidly modifies the hormonal balance, partly explaining the body weight increase, and that hormonal changes precede this body weight increase. Hyperleptinaemia is apparently a consequence of excess weight.

The intraovarian actions of estrogen receptor-alpha are necessary to repress the formation of morphological and functional Leydig-like cells in the female gonad

The predisposition of the testis and ovary to primarily synthesize testosterone (T) and estradiol (E2), respectively, is due to gonadal-specific cell types that differentially express the various hydroxysteroid (17beta) dehydrogenase (HSD17B) isoforms. In testes, Leydig cells rely on LH stimulation to maintain expression of the type 3 (HSD17B3) isoform, which specifically converts androstenedione to T. In ovaries, thecal interstitial (TI) cells also rely on LH to induce androgen synthesis but lack HSD17B3 and therefore secrete androgens of low biological activity. Therefore, thecal cells may possess a mechanism to repress the Leydig cell phenotype and HSD17B3 expression. E2 is known to inhibit experimentally Leydig cell function and proliferation. In the current study, we provide evidence that E2 prevents the development of functional Leydig-like cells in the murine ovary and that this action is mediated by estrogen receptor (ER) alpha. ERalpha-null (alphaERKO) female mice exhibit testis-like levels of Hsd17b3 expression in the ovaries and male-like levels of plasma T. Herein, we demonstrate that: 1) Hsd17b3 expression in alphaERKO ovaries is a primary effect of the loss of intraovarian ERalpha actions; 2) alphaERKO ovarian cells produce substantial levels of T in vitro, and this is blocked by a HSD17B3-specific inhibitor; 3) Hsd17b3 expression in alphaERKO ovaries is LH regulated and localized to the secondary interstitial (SI)/TI cells; and 4) alphaERKO SI/TI cells possess Leydig-like ultrastructural features. These data indicate that intraovarian ERalpha actions are required to repress Hsd17b3 expression in the ovary and may be important to maintaining a female phenotype in SI/TI cells.

Testicular phenotype in luteinizing hormone receptor knockout animals and the effect of testosterone replacement therapy

The LH receptor knockout model, developed in our laboratory, was used in determining what FSH alone can do in the absence of LH signaling and whether any of the testicular LH actions are not mediated by androgens. The results revealed that null animals contained smaller seminiferous tubules, which contained the same number of Sertoli cells, spermatogonia, and early spermatocytes as wild-type siblings. The number of late spermatocytes, on the other hand, was moderately decreased, the number of round spermatids was dramatically decreased, and elongated spermatids were completely absent. These changes appear to be due to an increase in apoptosis in spermatocytes. While the number of Leydig cells progressively increased from birth to 60 days of age in wild-type animals, they remained unchanged in null animals. Consequently, 60-day-old null animals contained only a few Leydig cells of fetal type. The age-dependent increase in testicular macrophages lagged behind in null animals compared with wild-type siblings. Orchidopexy indicated that -/- testicular phenotype was not due to abdominal location. Rather, it was mostly due to androgen deficiency, as 21-day testosterone replacement therapy stimulated the growth of seminiferous tubules, decreased apoptosis, and increased the number of late spermatocytes and round spermatids and their subsequent differentiation into mature sperm. The therapy, however, failed to restore adult-type Leydig cells and testicular macrophage numbers to the wild-type levels. In summary, our data support the concept that FSH signaling alone can maintain the proliferation and development of Sertoli cells, spermatogonia, and early spermatocytes. LH actions mediated by testosterone are required for completion of spermatogenesis, and finally, androgen-independent actions of LH are required for the formation of adult-type Leydig cells and recruitment of macrophages into the testes.

Regulation of vascular endothelial growth factor production by Leydig cells in vitro: the role of protein kinase A and mitogen-activated protein kinase cascade

We previously reported the presence of vascular endothelial growth factor (VEGF) in testicular cells, and high concentrations of VEGF have been measured in semen, although its role in male reproduction remains obscure. In the present study we focus on understanding the mechanism of VEGF production by mouse Leydig cells cultured in vitro. Production of VEGF protein in medium by testicular cells was markedly increased by the addition of hCG in a time- and dose-dependent manner. Gonadotropin-stimulated VEGF production was mediated by cAMP-dependent protein kinase A (PKA), as evidenced by the effect of hCG being mimicked by 8Br-cAMP and being abolished in the presence of a PKA-specific inhibitor, H-89. Protein kinase C was not involved, as evidenced by phorbol 12-myristate 13-acetate having no influence on VEGF production by Leydig cells. In addition to hCG, atrial natriuretic peptide was also able to stimulate VEGF production, suggesting that cGMP is able to cross-activate PKA. A specific Src kinase inhibitor, PP2, could completely block the stimulatory effects of both gonadotropin and 8Br-cAMP on VEGF production by Leydig cells, implying an involvement of the Src kinase pathway. Furthermore, addition of U0126, an inhibitor of MEK 1/2, abolished the increase in VEGF production stimulated by both hCG and 8Br-cAMP. A similar inhibitory effect was observed by the addition of SB203580, a p38 mitogen-activated protein kinase inhibitor. Thus, in conclusion, Leydig cells are able to produce VEGF by a process under gonadotropic control, and PKA plays a key role in this process. Downstream of PKA, it appears that both MEK 1/2 and Src kinase-dependent pathways are involved, although further research will be necessary to determine the precise link between PKA and other kinases involved.

Men with nonobstructive azoospermia have Leydig cell hypertrophy but not hyperplasia

PURPOSE

We determined whether testicular histology in men with spermatogenic failure due to nonobstructive azoospermia shows true Leydig cell hyperplasia.

MATERIALS AND METHODS

Testicular biopsy specimens from 17 patients evaluated for infertility were retrospectively analyzed. Interstitial, tubular and Leydig cell volume were quantitatively evaluated. The total volume and number of Leydig cells per testicle were then calculated.

RESULTS

In 10 patients with obstructive azoospermia testicular histology showed normal spermatogenic function, while 7 had nonobstructive azoospermia. Average testicular volume plus or minus standard deviation was significantly larger in those with obstructive versus nonobstructive azoospermia (18.0 +/- 7.0 versus 9.3 +/- 8.7 cc, p = 0.025). Interstitial versus tubular volume was 32% of the total testis in the obstructive and 63% in the nonobstructive groups (p = 0.003). Although Leydig cell volume was proportionally greater in men with nonobstructive versus obstructive azoospermia (13.3% versus 0.05%, p = 0.045), there was no significant difference in the average number of Leydig cells per testicle (3.96 x 10 and 6.17 x 10, respectively, p = 0.16). The average volume of individual Leydig cells was significantly greater in men with the nonobstructive condition (253.0 +/- 98.7 versus 174.0 +/- 57.7 microm., p = 0.045).

CONCLUSIONS

These results suggest that men with nonobstructive azoospermia and those with normal spermatogenesis have an equivalent number of Leydig cells. However, the Leydig cells are hypertrophic and occupy a larger proportion of total testis volume in men with nonobstructive azoospermia. Therefore, patients with spermatogenic failure show Leydig cell hypertrophy but not hyperplasia.

Annexin 1 (lipocortin 1) mimics inhibitory effects of glucocorticoids on testosterone secretion and enhances effects of interleukin-1beta

Annexin 1 is an important mediator of glucocorticoid action in the hypothalamo-pituitary axis; however, little is known of its role in mediating glucocorticoid actions in the peripheral endocrine organs. Accordingly, we have carried out a preliminary study to investigate the effects of annexin 1 in vitro on the testicular secretion of testosterone, a process inhibited by both glucocorticoids and interleukin-1beta (IL-1beta). Luteinizing hormone (LH) and forskolin stimulated the release of testosterone from dispersed murine testicular cells in vitro. Their effects were reduced in cells from mice pretreated with dexamethasone (DEX). Similarly, preincubation of testicular cells from untreated mice with DEX, corticosterone, or 11-dehydrocorticosterone reduced LH-stimulated testosterone release, as did the 11beta-hydroxysteroid dehydrogenase inhibitors, glycyrrhetinic acid and carbenoxolone. The inhibitory actions of the steroids were mimicked by annexin 1(1-188) (ANXA1(1-188)) (a stable annexin 1 analog). IL-1beta produced a marked decrease in the response to LH, which was blocked by indomethacin, a nonselective cyclooxygenase inhibitor and an additive effect with DEX and ANXA1(1-188). These results confirm reports that glucocorticoids and IL-1beta inhibit LH-stimulated testosterone release from mouse testicular cells. They also show, for the first time, that the effects of the steroids are mimicked by annexin 1 and that, in contrast to their mutually antagonistic effects in the neuroendocrine system, IL-1beta and annexin 1 exert additive actions in the testis.

Endocrine and paracrine control of sperm production in stallions

The specific nature and relative contribution of the major hormones involved in regulation of reproductive function of the stallion are not well defined nor have paracrine or autocrine factors been identified. Over the last 12 years, our laboratory has been engaged in characterizing the hypothalamic-pituitary-testicular axis (HPT) in stallions. A number of endocrine factors and mechanisms important for normal reproductive function have been investigated. Studies investigating poor fertility in stallions suggest that a closer look at the testicular level is warranted. For a complete understanding of intratesticular control mechanisms including cell-to-cell interactions in the stallion, studies on the actions of paracrine/autocrine factors such as growth factors, inhibin, activin, and oxytocin are needed. In other species, paracrine/autocrine systems appear to be important in modulating endocrine control of testicular function and spermatogenesis.

Identification, localization, and function in steroidogenesis of PAP7: a peripheral-type benzodiazepine receptor- and PKA (RIalpha)-associated protein

Peptide hormones and cAMP acutely stimulate steroid biosynthesis by accelerating the transport of cholesterol into the mitochondria. The peripheral-type benzodiazepine receptor (PBR) has been shown to be an indispensable element of the cholesterol transport machinery. Using the yeast two-hybrid system and PBR as bait, we identified a protein that interacts with PBR, the PBR-associated protein PAP7. Using the regulatory subunit RIalpha of PKA as bait, we also isolated PAP7. Glutathione-S-transferase -PAP7 interacted with both the mitochondrial PBR and cytosolic PKA-RIalpha in MA-10 Leydig cells. PAP7 is a novel 52-kDa protein present in mouse, rat, and human tissues, and it has a major 3-kb mRNA transcript in all tissues examined. Immunohistochemical and in situ hybridization studies indicated that PAP7 is highly expressed in the gonads, adrenal, hippocampus, and distinct brain neuronal and glial populations. Overexpression of the full length PAP7 increased the hCG-induced steroid production. However, overexpression of a partial PAP7, which includes the PBR- and PKA-RIalpha-binding domains, inhibited the hormone-stimulated cholesterol transport and steroid synthesis. Treatment of MA-10 cells with oligonucleotides antisense to PAP7 also inhibited the hCG-stimulated steroid formation, suggesting that PAP7 is a functional element of the hormone-induced signal transduction cascade leading to steroidogenesis. PAP7 may function by targeting the PKA isoenzyme to organelles rich in PBR, i.e. mitochondria, where phosphorylation of specific protein substrates may induce the reorganization of PBR topography and function.

Insulin modifies the proliferation and function of chicken testis cells

We investigated whether insulin plays a role in the proliferation and androgen production of chick testis cells. Testes from 18-d-old chick embryos or newly hatched chickens were dissociated and precultured in the presence of fetal bovine serum (FBS) for 24 h. After this period, testis cells from 18-d-old chick embryos were cultured in serum-free medium for 1 h with 0, 10, 50, or 100 microg/mL of insulin and were then exposed to human chorionic gonadotropin (hCG) for 3 h. In addition, some cells were incubated for 18 h with only insulin or insulin plus hCG. Androgens were measured by radioimmunoassay in the spent media. To study the influence of insulin on testis cell proliferation, cells were exposed to insulin for 18 h. A pulse of 3H-thymidine was added thereafter. We found that 18-d-old embryonic testis cells responded to hCG, increasing androgen production. Incubation with insulin for 1 h did not affect basal androgen production but modified the subsequent response to hCG. The addition of insulin plus hCG for 18 h resulted in important downregulation of the hCG effect. In addition, insulin significantly increased the proliferation of embryonic testis cells. The cells from testes of newly hatched chickens were precultured as described for embryonic cells and then exposed to insulin for 1 h in a serum-free medium. This treatment significantly increased the basal androgen production. Insulin also significantly enhanced the response to hCG of the testis cells from newly hatched chickens. These results strongly suggest that insulin has a role in the activity and in the proliferation of cultured testis cells throughout the perinatal period.

Carbohydrate moieties of the interstitial and glandular tissues of the amphibian Pleurodeles waltl testis shown by lectin histochemistry

The amphibian testis is a useful model because of its zonal organisation in lobules, distributed along the cephalocaudal axis, each containing a unique germ cell type. Sperm empty lobules form the so-called glandular tissue at the posterior region of the gonad. Androgen production is limited to the cells of the interstitial tissue surrounding lobules with spermatozoa bundles and to the cells of the glandular tissue. In this work, we have studied the distribution of terminal carbohydrate moieties of N- and O-linked oligosaccharides in the interstitial and glandular tissue of the Pleurodeles waltl testis, by means of 14 lectins combined with chemical and enzymatic deglycosylation pretreatment. Some differences in glycan composition between the interstitial and the glandular tissue have been detected. Thus in both tissues, N-linked oligosaccharides contained mannose, Gal(beta1,4)GlcNAc, and Neu5Ac(alpha2,3)Gal(beta1,4)GlcNAc, while O-linked oligosaccharides contained Con A-positive mannose, Gal(beta1,3)GalNAc, Gal(beta1,4)GlcNAc, Neu5Ac(alpha2,3)Gal(beta1,4)GlcNAc, and WGA-positive GlcNAc. Fucose was also detected in both tissues. However, GlcNAc on N-linked oligosaccharides and GalNAc and Neu5Ac(alpha2,6)Gal/GalNAc on both N- and O-linked oligosaccharides were found only in the interstitial tissue. As glandular tissue cells arise from the innermost cells of interstitial tissue that surround lobules, the differences in the glycan composition of interstitial and glandular tissue shown in this work may be related to the start of androgen synthesis when steroid hormone (SH)-secreting cells develop.

The impact of mild Leydig cell dysfunction following cytotoxic chemotherapy on bone mineral density (BMD) and body composition

BACKGROUND

Overt testosterone deficiency is associated with a reduction in BMD and alteration in body composition. However, there are few data concerning the impact of mild hypogonadism on these parameters.

PATIENTS AND METHOD

We have identified a cohort of 36 men aged < 55 years with mild Leydig cell impairment, defined by a raised LH level (LH >/= 8 IU/l) in the presence of a testosterone level in the lower half of the normal range or frankly subnormal (< 20 nmol/l), following treatment with procarbazine-containing chemotherapy regimens or high-dose chemotherapy for haematological malignancy. These men underwent measurements of BMD (measured by dual-energy X-ray absorptiometry (DXA), single energy X-ray absorptiometry (SXA) and quantitative CT (QCT)), body composition (DXA), markers of bone turnover, serum lipids and serum IGF-1. To allow for changes that may be directly attributable to the underlying disease or its treatment, results were compared with those obtained in 14 men who had received the same chemotherapy for the same diseases but had normal LH and testosterone levels (controls).

RESULTS

When data from all 50 men were considered together there were significant reductions in BMD of the lumbar spine both by DXA (Z = - 0.34, P = 0.01) and QCT (Z = - 1.5, P < 0. 0001), at the femoral neck (Z = - 0.52, P < 0.0001) and distal forearm (Z = - 0.21, P = 0.05). Mean femoral neck BMD was significantly lower in patients compared with controls (Z = - 0.68 vs. Z = - 0.11, P = 0.05) and there was a nonsignificant trend towards lower lumbar spine BMD measured by QCT (Z = - 1.64 vs. Z = - 1.10; P = 0.09). In addition, serum testosterone level and testosterone:LH ratio significantly correlated with femoral neck BMD (r = 0.28, P = 0.05 and r = 0.37, P = 0.008, respectively). There were no significant differences in lean body mass, fat mass and percentage fat between the patients and controls. There was, however, a difference in the distribution of body fat with a propensity for the patients to accrue truncal fat, and the serum testosterone level significantly inversely correlated with percentage of truncal fat (r = - 0.29, P = 0.04). There were no significant differences in lipid levels, IGF-1 levels or markers of bone turnover between the patients and controls.

CONCLUSIONS

These data suggest that mild Leydig cell impairment may have significant effects on bone mineral density and may result in subtle body composition changes, although in men who have received cytotoxic chemotherapy, other factors also contribute to the observed osteopenia. Testosterone replacement may be beneficial in some of these men and this requires further evaluation.

Osteoporosis due to cancer treatment: pathogenesis and management

Many therapeutic regimens in cancer treatment carry the risk of causing or favoring the development of osteoporosis. Therapies in which hypogonadism may occur are most relevant in this respect. Prompt hormone replacement therapy is indicated in these patients. In patients in whom this is undesirable because of a hormone-dependent tumor, the risk of osteoporosis should be assessed by means of osteodensitometry, and prophylactic or therapeutic measures should be instituted if necessary. Early intervention improves outcome because osteoporosis therapy is most effective in preventing deterioration of bone mass. There remains much uncertainty in assessing the risk of combination chemotherapy with regard to the development of osteoporosis. Negative effects on the skeleton have, however, been demonstrated for individual drugs, such as methotrexate and ifosfamide. Negative effects of the tumor itself on bone metabolism may aggravate the degree of osteoporosis. Detailed data and long-term experience to assess the risk are urgently needed in this area and constitute an important research topic for the coming years and decades. This review discusses the most prevalent mechanisms of osteoporosis caused by cancer treatment and outlines therapeutic strategies for the prevention and treatment of therapy-induced bone loss.

Testicular function after cytotoxic chemotherapy: evidence of Leydig cell insufficiency

PURPOSE

To evaluate testicular function in men after treatment with cytotoxic chemotherapy.

PATIENTS AND METHODS

We measured testosterone, sex hormone-binding globulin (SHBG), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels in 209 men after treatment with mechlorethamine, vinblastine, procarbazine, and prednisone, hybrid chemotherapy, or high-dose chemotherapy and in 54 healthy age-matched controls.

RESULTS

The mean age of the patients was 38 years (range, 19 to 68 years), and all patients had received chemotherapy between 1 and 22 years previously. Patients had significantly higher mean LH (7.9 v 4.1 IU/L; P < .0001) and FSH levels (18.8 v 3.1 IU/L; P < .0001) than controls. There was no significant difference in mean total testosterone level between the patients and controls, but there was a trend toward a lower mean testosterone/SHBG ratio in the patients (0.63 v 0.7; P = .08). Analysis of the hormonal parameters using a model that allowed for the effects of increasing age on testicular function showed evidence of significant recovery of gonadal function in the first 10 years after treatment. Fifty-two percent of patients had LH levels at or above the upper limit of normal, and 32% of patients had increased LH with testosterone levels in the lower half of the normal range, suggesting a degree of Leydig cell impairment.

CONCLUSION

In a significant proportion of men, there is good evidence of Leydig cell dysfunction after cytotoxic chemotherapy. The clinical significance of this Leydig cell dysfunction is not clear, but some of these men may benefit from testosterone replacement. Further studies are warranted.

Impact of aging and diabetes mellitus on the expression of the proliferating cell nuclear antigen in rat testicular tissue

This study evaluated the expression of proliferating cell nuclear antigen (PCNA), which is one of the important markers of cell proliferation, in testicular tissue with aging and progress of diabetes mellitus (DM). OLETF rats were used as animal models for non-insulin-dependent DM. They were 12, 30, 50, and 70 weeks old. The controls were age-matched nondiabetic LEIO rats. Testes were taken from all the rats and paraffin-embedded sections were cut and stained with PC 10 monoclonal AB (x50). Labeled cells were assessed in randomly selected fields. Labeling index (LI) for each stage of spermatogenesis was estimated and total LI for each specimen was calculated. In control rats, the 12-week-old animals showed the highest PCNA-LI. The indexes started to decrease in other older animals, with an increase in the number of suppressed stages as the animals aged, leading to significant differences among groups except between the 12- and 30-week-old groups. The same features were also seen in DM animals as the disease progressed. The total LI of controls were significantly higher and the number of suppressed stages was lower than those of DM animals, except among the 12-week-old group. Both aging and DM have depressing effects on the expression of PCNA in testicular tissue. The decline in PCNA expression is parallel with advancement of age and progress of DM. However, DM has a more suppressing effect than aging on that expression. This suppression could explain the decrease in male fertility potential that may be associated with both conditions.

Vascular endothelial growth factor and its receptors in normal human testicular tissue

Expression of vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), and its receptors Flt-1 and KDR (Flk-1 in mouse) and their localization in the human testis were analyzed by means of reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry. VEGF mRNA was detected in the human testicular tissue and in fragments of seminiferous tubules by means of RT-PCR, while fragments of blood vessels isolated from testes were negative. Western blotting procedure using a specific VEGF antibody, revealed two protein bands corresponding to 24 and 49 kDa in the extracts prepared from the whole testis and in the seminiferous tubules while no such bands were found in isolated fragments of human testicular blood vessels. Also immunohistochemically, human testicular blood vessels show no VEGF immunoreactivity, while Leydig cells and Sertoli cells were positive. The mRNA of the VEGF receptor Flt-1 was found to be expressed in human testicular tissue, in isolated fragments of testicular blood vessels and in seminiferous tubules as determined by RT-PCR procedure. In accordance with these results, the Flt-1 protein was immunohistochemically localized in Leydig, Sertoli and perivascular cells. Endothelial cells of certain segments of human testicular microvasculature also stained positive for Flt-1. Expression of VEGF receptor, KDR, could be demonstrated in human testicular tissue, in isolated seminiferous tubules and in isolated fragments of human testicular blood vessels by means of RT-PCR. Immunohistochemically, the KDR protein was localized in endothelial cells and perivascular cells of capillaries within the lamina propria of seminiferous tubules. Leydig cells and Sertoli cells show KDR immunoreactivity, too. Thus we demonstrate the presence of both types of VEGF receptors Flt-1 and KDR on Leydig as well as on Sertoli cells which are normal non-endothelial cells, suggesting hitherto unrecognized and novel functions for such receptors. The results obtained permit us to suggest VEGF as a paracrine mitogenic and angiogenic factor, responsible for modulating the capillarization of the human testicular tissue and maintaining the functions of testicular microvasculature. VEGF may also influence the permeability of capillaries passing through the groups of Leydig cells and those localized within the lamina propria of human seminiferous tubules. The differences in the expression pattern of the VEGF receptors in the human testicular tissue probably reflect different VEGF effects in different compartments of human testis.