Follistatin is essential for normal postnatal development and function of mouse oviduct and uterus.

Female mice lacking the follistatin gene but expressing a human follistatin-315 transgene (tghFST315) have reproductive abnormalities (reduced follicles, no corpora lutea and ovarian-uterine inflammation). We hypothesised that the absence of follistatin-288 causes the abnormal reproductive tract via both developmental abnormalities and abnormal ovarian activity. We characterised the morphology of oviducts and uteri in wild type (WT), tghFST315 and follistatin-knockout mice expressing human follistatin-288 (tghFST288). The oviducts and uteri were examined in postnatal Day-0 and adult mice (WT and tghFST315 only) using histology and immunohistochemistry. Adult WT and tghFST315 mice were ovariectomised and treated with vehicle, oestradiol-17ß (100ng injection, dissection 24h later) or progesterone (1mg×three daily injections, dissection 24h later). No differences were observed in the oviducts or uteri at birth, but abnormalities developed by adulthood. Oviducts of tghFST315 mice failed to coil, the myometrium was disorganised, endometrial gland number was reduced and oviducts and uteri contained abundant leukocytes. After ovariectomy, tghFST315 mice had altered uterine cell proliferation, and inflammation was maintained and exacerbated by oestrogen. These studies show that follistatin is crucial to postnatal oviductal-uterine development and function. Further studies differentiating the role of ovarian versus oviductal-uterine follistatin in reproductive tract function at different developmental stages are warranted.

Progesterone stimulates expression of follistatin splice variants Fst288 and Fst315 in the mouse uterus.

Follistatin, an inhibitor of activin A, has key regulatory roles in the female reproductive tract. Follistatin has two splice variants: FST288, largely associated with cell surfaces, and FST315, the predominant circulating form. The mechanism regulating uterine expression of these variants is unknown. Quantitative RT-PCR was used to measure expression of follistatin splice variants (Fst288, Fst315), the activin bA subunit (Inhba) and the inhibin a subunit (Inha) in uterine tissues during early pregnancy (days 1­4, preimplantation) and in response to exogenous 17b-oestradiol (single s.c. injection) and progesterone (three daily s.c. injections) in ovariectomized mice. Uterine Fst288, Fst315 and Inhba expression increased during early pregnancy, with greater increases in Fst315 relative to Fst288 suggesting differential regulation of these variants. Fst288, Fst315, Inhba and Inha all increased in response to progesterone treatment. Fst288, but not Fst315, mRNA decreased in response to 17b-oestradiol treatment, whereas Inhba increased. A comparison of the absolute concentrations of uterine follistatin mRNA using crossing thresholds indicated that both variants were more highly expressed in early pregnancy in contrast to the hormone treatment models. It is concluded that progesterone regulates uterine expression of both follistatin variants, as well as activin A, during early pregnancy in the mouse uterus

Testicular immune cell populations and macrophage polarisation in adult male mice and the influence of altered activin A levels.

Detailed morphological characterization of testicular leukocytes in the adult CX3CR1 gfp/+ transgenic mouse identified two distinct CX3CR1 + mononuclear phagocyte (macrophage and dendritic cell) populations: stellate/dendriform cells opposed to the seminiferous tubules (peritubular), and polygonal cells associated with Leydig cells (interstitial). Using confocal microscopy combined with stereological enumeration of CX3CR1gfp/+ cells established that there were twice as many interstitial cells (68%) as peritubular cells (32%). Flow cytometric analyses of interstitial cells from mechanically-dissociated testes identified multiple mononuclear phagocyte subsets based on surface marker expression (CX3CR1, F4/80, CD11c). These cells comprised 80% of total intratesticular leukocytes, as identified by CD45 expression. The remaining leukocytes were CD3+ (T lymphocytes) and NK1.1+ (natural killer cells). Functional phenotype assessment using CD206 (an anti-inflammatory/M2 marker) and MHC class II (an activation marker) identified a potentially tolerogenic CD206+MHCII+ sub-population (12% of total CD45+ cells). Rare testicular subsets of CX3CR1 +CD11c+F4/80+ (4.3%) mononuclear phagocytes and CD3+NK1.1+ (3.1%) lymphocytes were also identified for the first time. In order to examine the potential for the immunoregulatory cytokine, activin A to modulate testicular immune cell populations, testes from adult mice with reduced activin A (Inhba+/-) or elevated activin A (Inha+/-) were assessed using flow cytometry. Although the proportion of F4/80+CD11b+ leukocytes (macrophages) was not affected, the frequency of CD206+MHCII+cells was significantly lower and CD206+MHCII- correspondingly higher in Inha+/- testes. This shift in expression of MHCII in CD206+ macrophages indicates that changes in circulating and/or local activin A influence resident macrophage activation and phenotype and, therefore, the immunological environment of the testis.

An RNA spiking method demonstrates that 18S rRNA is regulated by progesterone in the mouse uterus.

Identifying suitable housekeeping genes for quantitative RT-PCR in the uterus is problematic, as this tissue undergoes significant structural and functional alterations during the oestrous cycle and pregnancy in response to circulating hormones. The suitability of 18S rRNA as a housekeeping gene in mouse uterus was investigated by introducing an 'RNA spike' standard into the reverse transcription reaction. 18S rRNA levels increased by Day 4 of pregnancy and after progesterone administration in ovariectomized mice. We conclude that 18S rRNA is not a suitable housekeeping gene for quantitative RT-PCR analysis in progesterone-responsive tissues, and the RNA spiking method provides a suitable alternative.

Activins, follistatin and immunoregulation in the epididymis.

BACKGROUND: The interface between the epididymis and the immune system is implicated in many male reproductive pathologies. The resident immune cell populations and immune-environment within the epididymis are significantly different from the testis, which is an immune-privileged site. Moreover, the immune cell subsets and immunological responses between different regions of the epididymis vary considerably. The cauda epididymis is more susceptible to autoimmune responses than the caput in rodent models of active immunization or suppressed immune tolerance, and in men with congenital or physical damage to the reproductive tract. Activins are members of the transforming growth factor-ß family of cytokines that are crucial for testis and epididymal development; however, they also have complex immunoregulatory properties and may play an essential role in the regulation of immunity in the reproductive tract. MATERIALS AND METHODS: Our recent research and relevant publications by other researchers identified following a PubMed search are reviewed. RESULTS: The caput epididymis displays elevated endogenous expression of activins A and B and the immunoregulatory gene, indoleamine-2,3-dioxygenase, co-existing with an extensive population of intra-epithelial and interstitial macrophages and dendritic cells, which appear to be involved in regulating tolerance against sperm antigens. The caput is also relatively resistant to inflammatory damage caused by autoimmunity or bacterial infection, but the cauda, which exhibits low activin expression and high levels of the activin-binding protein, follistatin, is highly susceptible to inflammatory damage. Paradoxically, inflammation in the cauda induces increased activin production, and inhibition of activin activity reduces inflammatory responses. Studies using mouse models with altered levels of activins and follistatin indicate a relationship between the activins and genes involved in inflammation and immunoregulation. CONCLUSION: The existing data indicate that activins play a complex role in controlling inflammation and immunity in the epididymis and vas deferens.

Activin A target genes are differentially expressed between normal and neoplastic adult human testes: clues to gonocyte fate choice.

BACKGROUND: Human testicular germ cell tumours (TGCT) arise from germ cell neoplasia in situ (GCNIS) cells that originate from foetal germ cell precursors. Activin A is central to normal foetal testis development, and its dysregulation may contribute to TGCT aetiology. OBJECTIVE: (i) To test whether the expression profiles of activin A targets in normal and neoplastic human testes indicates functional links with TGCT progression. (ii) To investigate whether activin A levels influence MMP activity in a neoplastic germ cell line. MATERIALS AND METHODS: (1) Bouin's fixed, paraffin-embedded human testes were utilized for PCR-based transcript analysis and immunohistochemistry. Samples (n = 5 per group) contained the following: (i) normal spermatogenesis, (ii) GCNIS or (iii) seminoma. CXCL12, CCL17, MMP2 and MMP9 were investigated. (2) The human seminoma-derived TCam-2 cell line was exposed to activin A (24 h), and target transcripts were measured by qRT-PCR (n = 4). ELISA (n = 4) and gelatin zymography (n = 3) showed changes in protein level and enzyme activity, respectively. RESULTS: (i) Cytoplasmic CXCL12 was detected in Sertoli and other somatic cells, including those surrounding seminoma cells. Anti-CCL17 labelled only the cytoplasm of Sertoli cells surrounding GCNIS, while anti-MMP2 and anti-MMP9 labelled germline and epithelial-like cells in normal and neoplastic testes. (ii) Exposing TCam-2 cells to activin A (50 ng/mL) elevated MMP2 and MMP9 transcripts (fourfold and 30-fold), while only MMP2 protein levels were significantly higher after activin A (5 ng/mL and 50 ng/mL) exposure. Importantly, gelatin zymography revealed activin A increased production of activated MMP2. DISCUSSION: Detection of CCL17 only in GCNIS tumours may reflect a change in Sertoli cell phenotype to a less mature state. Stimulation of MMP2 activity by activin A in TCam-2 cells suggests activin influences TGCT by modulating the tumour niche. CONCLUSION: This knowledge provides a basis for understanding how physiological changes that influence activin/TGF-ß superfamily signalling may alter germ cell fate.

An in vitro model demonstrates the potential of neoplastic human germ cells to influence the tumour microenvironment.

Testicular germ cell tumours (TGCT) typically contain high numbers of infiltrating immune cells, yet the functional nature and consequences of interactions between GCNIS (germ cell neoplasia in situ) or seminoma cells and immune cells remain unknown. A co-culture model using the seminoma-derived TCam-2 cell line and peripheral blood mononuclear cells (PBMC, n = 7 healthy donors) was established to investigate how tumour and immune cells each contribute to the cytokine microenvironment associated with TGCT. Three different co-culture approaches were employed: direct contact during culture to simulate in situ cellular interactions occurring within seminomas (n = 9); indirect contact using well inserts to mimic GCNIS, in which a basement membrane separates the neoplastic germ cells and immune cells (n = 3); and PBMC stimulation prior to direct contact during culture to overcome the potential lack of immune cell activation (n = 3). Transcript levels for key cytokines in PBMC and TCam-2 cell fractions were determined using RT-qPCR. TCam-2 cell fractions showed an immediate increase (within 24 h) in several cytokine mRNAs after direct contact with PBMC, whereas immune cell fractions did not. The high levels of interleukin-6 (IL6) mRNA and protein associated with TCam-2 cells implicate this cytokine as important to seminoma physiology. Use of PBMCs from different donors revealed a robust, repeatable pattern of changes in TCam-2 and PBMC cytokine mRNAs, independent of potential inter-donor variation in immune cell responsiveness. This in vitro model recapitulated previous data from clinical TGCT biopsies, revealing similar cytokine expression profiles and indicating its suitability for exploring the in vivo circumstances of TGCT. Despite the limitations of using a cell line to mimic in vivo events, these results indicate how neoplastic germ cells can directly shape the surrounding tumour microenvironment, including by influencing local immune responses. IL6 production by seminoma cells may be a practical target for early diagnosis and/or treatment of TGCT.

Activin and follistatin interactions in the male reproductive tract: activin expression and morphological abnormalities in mice lacking follistatin 288.

Activin A is an important regulator of testicular and epididymal development and function, as well as inflammation and immunity. In the adult murine reproductive tract, activin A mRNA (Inhba) expression levels are highest in the caput epididymis and decrease progressively towards the distal vas deferens. The activin-binding protein, follistatin (FST), shows the opposite expression pattern, with exceptionally high levels of the Fst288 mRNA variant in the vas deferens. This unique pattern of expression suggests that activin A and follistatin, in particular FST288, play region-specific roles in regulating the epididymis and vas deferens. The cellular distribution of activin and follistatin and structural organization of the male reproductive tract was examined in wild-type and transgenic (TghFST315) mice lacking FST288. Compared to wild-type littermates, TghFST315 mice showed a 50% reduction in serum follistatin and a significant elevation of both activin A and B. Testicular, epididymal and seminal vesicle weights were reduced, but intra-testicular testosterone was normal. A decrease in the epididymal duct diameter in the corpus and thickening of the peritubular smooth muscle in the cauda, together with increased coiling of the proximal vas deferens, were observed in TghFST315 mice. No immune cell infiltrates were detected. Immunohistochemistry indicated that epithelial cells are the main source of activins and follistatin in the epididymis and vas deferens. Activin A, but not activin B, was also localized to sperm heads in the lumen of the epididymis and vas deferens. Expression of Inhba and another immunoregulatory gene, indoleamine-2,3-dioxygenase (Ido-1), was increased approximately twofold in the TghFST315 caput epididymis, but several other genes associated with immunoregulation, inflammation or fibrosis were unaffected. Our novel data indicate that disruption of follistatin expression has significant effects on the testis and epididymis, and suggest an association between activin A and indoleamine-2,3-dioxygenase in the caput epididymis, with implications for the epididymal immunoenvironment.

Regulated production of activin A and inhibin B throughout the cycle of the seminiferous epithelium in the rat.

Production and regulation of activin A and inhibin B during the cycle of the seminiferous epithelium were investigated in adult rats. Immunohistochemistry localised the activin beta(A)-subunit to the Sertoli cell cytoplasm, with much weaker expression in spermatocytes and spermatids. Both activin A and inhibin B, measured by ELISA were secreted by, seminiferous tubule fragments over 72 h in culture. Activin A was secreted in a cyclic manner with peak secretion from tubules isolated at stage VIII. Tubules collected during stage VI produced the least activin A. Inhibin B secretion was highest from stage IX-I tubules and lowest from stage VII tubules. Addition of interleukin-1beta (IL-1beta) had relatively little effect on activin A or inhibin B secretion in culture. In contrast, the peak secretion of activin A by stage VIII tubules was blocked by co-incubation with an excess of human recombinant IL-1 receptor antagonist, whereas inhibin B secretion increased slightly. Dibutyryl cAMP stimulated activin A secretion by late stage VII and VIII tubules and stimulated inhibin B across all stages. These data indicate that activin A and inhibin B are cyclically regulated within the seminiferous epithelium, with endogenous IL-1 (presumably IL-1alpha produced by the Sertoli cells), responsible for a peak of activin A production subsequent to sperm release at stage VIII. These data provide direct evidence that production of activin A and inhibin B by the Sertoli cell is locally modulated by IL-1alpha , in addition to FSH/cAMP, under the influence of the developing spermatogenic cells.

Regulation of activin A and inhibin B secretion by inflammatory mediators in adult rat Sertoli cell cultures.

The regulation of Sertoli cell activin A and inhibin B secretion during inflammation was investigated in vitro. Adult rat Sertoli cells were incubated with the inflammatory mediators, lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), IL-6 and the IL-1 receptor antagonist (IL-1ra) over 48 h in culture. Activin A, inhibin B and IL-1alpha were measured in the culture medium by specific two-site ELISAs. Both IL-1beta- and LPS-stimulated activin A and inhibited inhibin B secretion. LPS also stimulated the production of IL-1alpha in the cultures. In contrast to IL-1beta, IL-6 had no effect on activin A, although it did have a significant inhibitory effect on inhibin B secretion. Ovine follicle-stimulating hormone (FSH) and the cAMP analogue dibutyryl cAMP opposed the actions of IL-1 and LPS by suppressing activin A and IL-1alpha secretion and by stimulating inhibin B. Blocking IL-1 activity in the cultures by addition of an excess of IL-1ra completely prevented the response of activin A to exogenous IL-1beta, and reduced the response to LPS by 50%. In the presence of IL-1ra, basal secretion of inhibin B was increased, but IL-1ra was unable to reverse the suppression of inhibin B by LPS. These data indicate the importance of both IL-1 isoforms in regulating secretion of activin A and inhibin B by mature Sertoli cells during inflammation. The data also establish that inflammation exerts its effects on activin A and inhibin B secretion via other pathways in addition to those mediated by IL-1, and that hormonal stimulation by FSH and cAMP moderates the Sertoli cell response to inflammation. Interference with the complex interactions between these cytokines and hormones may contribute to the disruption of reproductive function that can accompany infection and illness in men.

Reciprocal regulation of activin A and inhibin B by interleukin-1 (IL-1) and follicle-stimulating hormone (FSH) in rat Sertoli cells in vitro.

In several biological systems, the inhibin beta(A) homodimer activin A is stimulated by, and in turn, inhibits the action of interleukin (IL)-1 (both IL-1alpha and IL-1beta) and IL-6. The possibility that a similar regulatory relationship operates within the testis was investigated. Sertoli cells from immature (20-day-old) rats were cultured with human IL-1alpha or IL-1beta, human IL-6 and/or ovine FSH or dibutyryl cAMP. Activin A and the inhibin dimers, inhibin A and inhibin B, were measured by specific ELISA. Immunoreactive inhibin (ir-inhibin) was measured by RIA. Activin/inhibin subunit mRNA expression was measured by quantitative real-time PCR. Both IL-1 isoforms, but not IL-6, stimulated activin A secretion through increased synthesis of beta(A)-subunit mRNA. IL-1 also stimulated activin A secretion by testicular peritubular cells. In contrast to the effect on activin A, IL-1 suppressed inhibin beta(B)-subunit and, to a lesser extent, alpha-subunit mRNA expression, thereby reducing basal and FSH-stimulated inhibin B secretion by the Sertoli cells. Conversely, FSH inhibited basal activin A secretion and antagonised the stimulatory effects of IL-1. Dibutyryl cAMP partially inhibited the action of IL-1 on activin A secretion, but had no significant effect on basal activin A secretion. Secretion of inhibin A was low in all treatment groups. These data demonstrate that IL-1 and FSH/cAMP exert a reciprocal regulation of activin A and inhibin B synthesis and release by the Sertoli cell, and suggest a role for activin A as a potential feedback regulator of IL-1 and IL-6 activity in the testis during normal spermatogenesis and in inflammation.

The heterogeneity of isolated adult rat Leydig cells separated on Percoll density gradients: an immunological, cytochemical, and functional analysis.

Intertubular cells, isolated from adult rat testes by collagenase dispersal under conditions designed to minimize cell damage, were fractionated on Percoll density gradients. In the gradient fractions, there was a close cellular correlation between the presence of 3 beta-hydroxysteroid dehydrogenase (3 beta HSD), determined by cytochemistry, and other Leydig cell markers (nonspecific esterase, autofluorescence, and an antigen defined by monoclonal antibody LC-1C6). As the reagents for 3 beta HSD cytochemistry are excluded by intact membranes, Leydig cells with damaged plasma membranes were identified by 3 beta HSD reactivity in suspended cell preparations, and the total number of 3 beta HSD-positive (3 beta HSD+) cells in the same preparations was determined after lysis of the cell membrane. Whole cells were differentiated from cytoplasmic fragments by counterstaining with the nuclear dye propidium iodide, and the number of intact Leydig cells in each preparation was determined subsequently by subtracting the number of damaged nucleated 3 beta HSD+ cells from the total number of nucleated 3 beta HSD+ cells. The majority of intact isolated Leydig cells were found in gradient fractions of 1.054-1.096 g/ml density. Acute (3-H) basal and hCG-stimulated testosterone production per intact Leydig cell were dependent upon the concentration of Leydig cells per assay well, indicating that there is cooperativity among Leydig cells in vitro. There was no difference in steroidogenic function among intact Leydig cells from different fractions of the above density gradient range at assay concentrations greater than 10,000 Leydig cells/well. At lower cell concentrations, Leydig cells from gradient fractions of lower density (1.054-1.064 g/ml) produced slightly less testosterone in response to hCG stimulation than Leydig cells from more dense fractions (1.070-1.096 g/ml). Prolonging the exposure of isolated cells to the dispersal conditions caused declines in the apparent buoyant density and basal testosterone and hCG-stimulated cAMP and testosterone production of all Leydig cells, without detectable changes in cell integrity. The data indicate that both the absolute steroidogenic function and the functional heterogeneity of isolated intact Leydig cells are, at least in part, dependent upon the procedures used for their isolation.

Inhibin/activin beta-subunit monomer: isolation and characterization.

Using an activin RIA that showed limited cross-reaction with inhibin, activin immunoactivity was monitored throughout the isolation of activin from bovine follicular fluid and side-fractions during the isolation of human recombinant inhibin. Two peaks of activin immunoactivity were identified in both materials and isolated to homogeneity by dye affinity chromatography, hydrophobic interaction and gel permeation chromatography, and reverse phase HPLC. The purified proteins in all four peaks had terminal amino acid sequences identical to those of the inhibin/activin beta-subunit. The molecular masses determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing (and reducing) conditions were 25 and 15 and 15 and 15 kilodaltons (kDa) for each pair of proteins from both sources. Based on these criteria, the bovine and human recombinant 25-kDa proteins correspond to the inhibin/activin beta A-subunit dimer (activin-A), while the 15-kDa proteins correspond to the inhibin/activin beta A-subunit monomer. The activity of the monomer was 17% of the activity of the dimer in the activin RIA. Based on this level of cross-reaction and the proportion of monomer to dimer immunoactivity found after reverse phase HPLC of bovine follicular fluid, it is estimated that the levels of monomer in bovine follicular fluid are 25-60% those of the dimer. The biological activities of the human recombinant activin monomer and dimer were investigated in two different cell culture systems. In a rat pituitary cell system the activity of the activin monomer was 19% of the activity of the dimer in stimulating FSH release, while in rat thymocyte cultures the activity of the monomer was 45% the activity of the dimer in suppressing lectin-stimulated [3H]thymidine uptake. It is concluded that the beta A-subunit monomer is found in bovine follicular fluid at a level 25-60% that of the beta A-subunit dimer (activin-A). The monomer displays in vitro responses similar to those of the dimer, although the monomer is less active (18-45%) than the dimer. It is unclear if dimerization of the monomer is a necessary prerequisite for biological activity.

The effect of testicular macrophages and interleukin-1 on testosterone production by purified adult rat Leydig cells cultured under in vitro maintenance conditions.

A functional interaction between testicular macrophages and Leydig cells has been suggested. The present study attempts to clarify the interaction between purified Leydig cells and macrophages from adult male rats in coculture, employing culture conditions that maintain Leydig cell steroidogenic responsiveness in vitro. Basal Leydig cell testosterone production over 24 h was not significantly affected by coculture with macrophages, but an inhibitory effect of testicular macrophages on testosterone production by Leydig cells over 24 h was observed in the presence of increasing doses of LH from 0.125 ng/ml up to a maximally stimulating dose of 8 ng/ml. A consistent inhibitory effect was observed over a range of Leydig cell-testicular macrophage coculture ratios from 0.5:1 to 4:1 in the presence of LH (8 ng/ml). A similar inhibitory effect on maximal LH-stimulated Leydig cell testosterone production over 24 h was observed when Leydig cells were cocultured with peritoneal macrophages. Conditioned medium collected from testicular or peritoneal macrophage cultured for 24 h also inhibited LH-stimulated Leydig cell testosterone production, indicating that the effect of the macrophages was mediated by a secreted product. Inhibition of LH-stimulated testosterone production was observed also when Leydig cells were cultured in the presence of testicular macrophages for 24 h before maximal LH stimulation (8 ng/ml) for a further 24 h. Human recombinant interleukin-1 alpha and interleukin-1 beta (0.5-10 U/ml) did not significantly alter basal or LH-stimulated Leydig cell testosterone production at 24, 48, or 72 h of culture. The specific binding of 125I-human CG to Leydig cells was not affected by testicular macrophage-conditioned medium. These data demonstrate that testicular and peritoneal macrophages inhibit LH-stimulated Leydig cell testosterone production in coculture through secreted factors, acting distal to the LH receptor, and provide further support for paracrine interactions between these cell types.

Bacterial lipopolysaccharide-induced inflammation compromises testicular function at multiple levels in vivo.

While it is well known that serious illness and inflammation reduce male fertility, the mechanisms involved are poorly understood. In adult male rats, a single injection of lipopolysaccharide at doses that induced either mild or severe inflammation, caused a biphasic decline in Leydig cell testosterone production and gonadotropin responsiveness. In the high dose group only, serum LH levels also were reduced; however, intratesticular testosterone concentrations remained at a level adequate to support qualitatively normal spermatogenesis in both treatment groups. Testicular interstitial fluid formation also declined in a dose-dependent fashion after lipopolysaccharide treatment. In the high dose group only, these hormonal and vascular changes were accompanied by an increase in endothelial permeability, microhemorrhage, and inflammatory cells in the testis, followed by vacuolization of round spermatid nuclei, disruption of Sertoli-germ cell contacts at stages I-IV of the cycle of the seminiferous epithelium, and subsequently apoptosis of spermatocytes at stages II-V. These data indicate that mild inflammation causes local inhibition of Leydig cell function with relatively little spermatogenic damage. The pathological changes in spermatogenic function during severe inflammation are most likely due to direct effects of inflammatory mediators on the seminiferous epithelium or testicular vasculature, rather than inhibition of the brain-pituitary-Leydig cell axis.

The quantification of steroidogenesis-stimulating activity in testicular interstitial fluid by an in vitro bioassay employing adult rat Leydig cells.

An in vitro bioassay for steroidogenesis-stimulating activity (SSA) in charcoal-extracted rat testicular interstitial fluid (IF) was developed. The bioassay was based upon stimulation of testosterone production by Percoll gradient-purified adult rat Leydig cells during a 20 h incubation in the presence of a maximally stimulating dose of human CG (hCG). The hCG-stimulated conditions were employed to avoid assay interference by endogenous LH in the sample preparations. The standard preparation (a pool of IF from normal adult rats) stimulated testosterone production 3- to 4-fold above that obtained with a maximal dose of either hCG or LH alone, and a linear log dose-testosterone response was observed over the range from 150% to 300% of hCG-stimulated testosterone production. The bioassay had a mean index of precision (lambda) of 0.13 (n = 10 assays), a between assay variation of 10.7-11.7%, and a useful working range from 4.9-28 microliters IF including at least three serial half-dilutions. Parallelism with the IF standard was obtained with IF collected from aged (greater than 15 months old) rats, adult rats made bilaterally cryptorchid for either 4 weeks or 12 months, or injected 6 h previously with 100 IU hCG, and with ovine testicular lymph. Testicular SSA was not affected by coincubation with rat LH antiserum and was not attributable to prevention of oxygen-mediated enzyme damage during the incubation period. Although charcoal-extracted rat serum log dose-response relationships were nonparallel with the standard, serum displayed an apparent relative bioactivity of approximately 20% that of normal IF based on ED50 comparisons. The activity of testicular IF was not affected by coincubation with serum. Untreated and charcoal-extracted rat albumin, at an assay concentration equivalent to that present in normal rat serum or IF, caused only a minor stimulation of testosterone production. Charcoal-extracted bovine albumin, ovalbumin, epidermal growth factor, insulin-like growth factor-1, bovine 31 kDa inhibin, and transforming growth factor-beta were inactive. Activity was nondetectable in rat thoracic duct lymph or high speed supernatants of adult rat testicular extracts. Testicular SSA and serum from normal rats displayed slightly different time-courses of action, with SSA active during both acute (1.0 h) and longer term (2.0-20 h) incubations, while serum stimulated testosterone production only in the longer term incubations.(ABSTRACT TRUNCATED AT 400 WORDS)

Macrophage migration inhibitory factor production by Leydig cells: evidence for a role in the regulation of testicular function.

Macrophage migration inhibitory factor (MIF), described originally as a product of activated T lymphocytes, recently has been found to be released by monocytes/macrophages and the anterior pituitary gland. Immunohistochemical studies of the adult rat testis using an affinity-purified polyclonal antimurine MIF antibody demonstrated strong staining for MIF in Leydig cells and their putative precursors. Peritubular myoid cells and the seminiferous epithelium were negative for MIF staining; however, a weak reaction around the heads of elongated spermatids also was observed. The expression of MIF messenger RNA and protein in whole rat testis was demonstrated by Northern blot and Western blot analyses, respectively. Both MIF messenger RNA and protein immunoreactivity in Leydig cells was observed in testes obtained from long term hypophysectomized rats. Significant concentrations of intracellular MIF were detected in lysates of the TM3 Leydig cell line (7.23 +/- 2.6 pg/microgram protein), and testicular interstitial fluid contained 14.7 +/- 1.6 ng/ml MIF protein, as measured by MIF-specific enzyme-linked immunosorbent assay. To gain insight into the possible biological role of MIF in the testis, cultures of adult rat seminiferous tubules and purified Leydig cells were incubated together with recombinant murine MIF (rMIF). Neither rMIF (50 ng/ml) nor a neutralizing anti-MIF antiserum was found to affect basal or LH-stimulated Leydig cell steroidogenesis in vitro. However, a dose-dependent decrease in the secretion of inhibin by the seminiferous tubules was observed at rMIF concentrations ranging from 10-100 ng/ml. Taken together, these data indicate that Leydig cells produce MIF in vivo and suggest an important regulatory role for this newly discovered mediator of testicular function.

Cloning and regulation of the rat activin betaE subunit.

Using a combination of polymerase chain reaction (PCR) procedures, we have cloned and sequenced the rat activin beta(E) subunit cDNA. The putative protein corresponding to the prepro-activin beta(E) subunit was predicted to comprise 350 amino acids which, when cleaved between amino acid residues 236 and 237, would yield a mature polypeptide of approximately M(r) 12 500 with a predicted pI of 5.1. Two cDNA transcripts for activin beta(E) were identified; these differed by 738 bp in the 3'-untranslated region. Activin beta(E) mRNA transcripts were expressed only in rat liver and lung tissue as assessed by Northern blotting and PCR analysis. Relatively higher levels of both transcripts were found in the liver, whereas the lung contained lower levels that were detectable by PCR only. In situ hybridisation data showed that, within the liver, activin beta(E) mRNA was localised to hepatocytes. In vivo treatment with lipopolysaccharide as a means of activating the immune system and the hepatic acute-phase response resulted in stimulated activin beta(E) mRNA levels, compared with untreated, control rats. This increased expression was accompanied by a preferential increase in the amount of the long activin beta(E) transcript over the shorter transcript. These findings suggested that the two activin beta(E) mRNA transcripts may be products of alternative splicing events or use alternative polyadenylation sites which are differentially regulated during inflammation. These data provide evidence of a role for activin beta(E) in liver function and inflammation in the rat.

A sensitive and specific in vitro bioassay for activin using a mouse plasmacytoma cell line, MPC-11.

A new in vitro bioassay for activin was developed using the mouse plasmacytoma cell line, MPC-11. Human recombinant (hr) activin A dose-dependently inhibited the proliferation of these cells, whereas a range of other factors, including inhibin, follistatin and transforming growth factor-beta1, -beta2 and -beta3 had no effect. Conditioned medium containing activin B induced an inhibition similar to hr-activin A. The inhibitory influence of activin A could be blocked by follistatin, but not by hr-inhibin A. This bioassay had a sensitivity for activin A of around 0.4 ng/ml, an ED50 response of 3.5 ng/ml, and an intra-assay coefficient of variation of <11%. It offers substantial advantages over existing in vitro activin bioassays in terms of ease of use, specificity and throughput. The utility of the MPC-11 bioassay was demonstrated in the purification of activin from amniotic fluid, where an almost identical profile of bioactive activin A was detected compared with the pituitary cell bioassay of activin. Bioactive activin could also be detected in unpurified ovine allantoic and amniotic fluids and bovine follicular fluid. Measuring activin in untreated and heat-treated human sera or seminal plasma was hampered by a non-specific inhibitory effect, so that several serum samples did not run parallel with the hr-activin A standard. This inhibitory effect by serum could not be overcome by addition of follistatin, suggesting it is not activin-like bioactivity. This new bioassay for activin demonstrates widespread applicability for monitoring of purified or partially purified samples during purification procedures, bioactivity measurements, receptor-binding studies and assays of cell culture medium.

Differential effects of dexamethasone treatment on lipopolysaccharide-induced testicular inflammation and reproductive hormone inhibition in adult rats.

A single intraperitoneal injection of lipopolysaccharide (LPS) causes a biphasic suppression of testicular steroidogenesis in adult rats, with inhibition at 6 h and 18-24 h after injection. The inhibition of steroidogenesis is independent of the reduction in circulating LH that also occurs after LPS treatment, indicating a direct effect of inflammation at the Leydig cell level. The relative contributions to this inhibition by intratesticular versus systemic responses to inflammation, including the adrenal glucocorticoids, was investigated in this study. Adult male Wistar rats (eight/group) received injections of LPS (0.1 mg/kg i.p.), dexamethasone (DEX; 50 microg/kg i.p.), LPS and DEX, or saline only (controls), and were killed 6 h, 18 h and 72 h later. Treatment with LPS stimulated body temperature and serum corticosterone levels measured 6 h later. Administration of DEX had no effect on body temperature, but suppressed serum corticosterone levels. At the dose used in this study, DEX alone had no effect on serum LH or testosterone at any time-point. Expression of mRNA for interleukin-1beta (IL-1beta), the principal inflammatory cytokine, was increased in both testis and liver of LPS-treated rats. Serum LH and testosterone levels were considerably reduced at 6 h and 18 h after LPS treatment, and had not completely recovered by 72 h. At 6 h after injection, DEX inhibited basal IL-1beta expression and the LPS-induced increase of IL-1beta mRNA levels in the liver, but had no effect on IL-1beta in the testis. The effects of DEX on IL-1beta levels in the liver were no longer evident by 18 h. In LPS-treated rats, DEX caused a significant reversal of the inhibition of serum LH and testosterone at 18 h, although not at 6 h or 72 h. Accordingly, DEX inhibited the systemic inflammatory response, but had no direct effect on either testicular steroidogenesis or intra-testicular inflammation, at the dose employed. These data suggest that the inhibition of Leydig cell steroidogenesis at 6 h after LPS injection, which was not prevented by co-administration of DEX, is most likely due to direct actions of LPS at the testicular level. In contrast, the later Leydig cell inhibition (at 18 h) may be attributable to extra-testicular effects of LPS, such as increased circulating inflammatory mediators or the release of endogenous glucocorticoids, that were inhibited by DEX treatment. These data indicate that the early and late phases of Leydig cell inhibition following LPS administration are due to separate mechanisms.