Fibroblast growth factor receptor type 1 expression during rat testicular development and its regulation in cultured Sertoli cells

Clinical Characteristics and Spermatogenesis in Patients with Congenital Hypogonadotropic Hypogonadism Caused by FGFR1 Mutations

OBJECTIVE

The aim of this study was to investigate the clinical characteristics of patients diagnosed with congenital hypogonadotropic hypogonadism (CHH) caused by FGFR1 (fibroblast growth factor receptor 1) gene mutations and to evaluate the effect of gonadotropin or pulsatile gonadotropin-releasing hormone (GnRH) therapy on spermatogenesis.

METHODS

A retrospective study was conducted on CHH patients admitted to Peking Union Medical College Hospital from January 2012 to March 2020. Clinical features and laboratory results were recorded. Testicular volume and sperm count responding to gonadotropin and pulsatile GnRH therapy were compared between the FGFR1 mutation group and the mutation-negative group.

RESULTS

(1) FGFR1 mutation group included 14 patients who received sperm-induction therapy, and the mutation-negative group enrolled 25 CHH patients. (2) The incidence of cryptorchidism was 50.0% (7/14) and 12.0% (3/25) in the FGFR1 group and the mutation-negative group, respectively (p=0.019). The baseline testicular volume of the FGFR1 mutation group was smaller than that of the mutation-negative group, 1.6 (0.5-2.0) mL vs. 2 (1.75-4) mL (p=0.033). The baseline luteinizing hormone (LH), Follicle-stimulating hormone (FSH), and testosterone levels were similar between the two groups. (3) Using the Kaplan-Meier and log-rank tests for the analysis of spermatogenesis, it was found that there was no significant difference in the first sperm appearance between the FGFR1 mutation group and the mutation-negative group (χ ² = 1.974, p=0.160). The median time of spermatogenesis in the FGFR1 mutation group was longer than that in the mutation-negative group, 16 months vs. 10 months, respectively. The cumulative spermatogenesis success rate at 12 months in the FGFR1 mutation group (35.71%) was lower than that in the mutation-negative group (68.75%) (p=0.047). The sperm concentration in the mutation-negative group was more easily achieved for different thresholds compared with that in the FGFR1 mutation group, but no significant difference was observed (p > 0.05) between the two groups. The last follow-up examination showed that the testicular volume was 7.00 (4.75-12.00) mL and 10.56 ± 4.82 mL (p=0.098), the ejaculate volume of sperm was 2.20 (1.40-2.26) mL and 3.06 ± 1.42 mL (p=0.175), and the sperm concentration was 7.19 (1.00-9.91) million/mL and 18.80 (4.58-53.62) million/mL (p=0.038) in the FGFR1 mutation and mutation-negative groups, respectively, while the sperm motility (A%, A + B%, and A + B + C%) was similar for the two groups (p=0.839, 0.909, and 0.759, respectively). The testosterone level during treatment was 366.02 ± 167.03 ng/dL and 362.27 ± 212.86 ng/dL in the FGFR1 mutation and mutation-negative groups, respectively (p=0.956).

CONCLUSION

Patients with FGFR1 mutations have a higher prevalence of cryptorchidism and smaller testicular volume. Although patients with FGFR1 mutations have a similar rate of success for spermatogenesis compared to that of the mutation-negative patients, a longer treatment period was required and a lower sperm concentration was achieved.

The effects of an in utero exposure to 2,3,7,8-tetrachloro-dibenzo-p-dioxin on male reproductive function: identification of Ccl5 as a potential marker

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dioxin-like compounds are widely encountered toxic substances suspected of interfering with the endocrine systems of humans and wildlife, and of contributing to the loss of fertility. In this study, we determined the changes in testicular gene expression caused by in utero exposure to TCDD along with the intra-testicular testosterone levels, epididymal sperm reserves, daily sperm production (DSP) and testis histology. To this purpose, female pregnant Sprague-Dawley rats orally received TCDD (10, 100 or 200 ng/kg body weight) or vehicle at embryonic day 15, and the offspring was killed throughout development. Hepatic Cyp1a1 gene expression was measured in the offspring to confirm the exposure to TCDD. The gross histology of the testes and intra-testicular testosterone levels were normal among the studied groups. Sperm reserves were altered in 67-day-old rats of the TCDD-200 group, but not in 145-day-old animals or in the other TCDD-exposed groups. Nonetheless, fertility was not altered in males of the TCDD-200 group, and the F2 males generated had normal sperm reserves and DSP. Microarray analysis permitted the identification of eight differentially expressed genes in the 4-week-old testes of the TCDD-200 compared with that of the control group (cut-off value +/- 1.40), including the down-regulated chemokine Ccl5/Rantes. Inhibition of Ccl5/Rantes gene expression was observed throughout development in the TCDD-200 group, and at 67 and 145 days in the TCDD-100 group (animals of younger ages were not examined). Ccl5/Rantes gene expression was mostly confined in Leydig cells. F2 males generated from males of the TCDD-200 group had normal levels of Ccl5/Rantes in testis and Cyp1a1 in liver, which might indicate that Ccl5/Rantes is a marker of TCDD exposure in testis such as Cyp1a1 in liver. In conclusion, we demonstrated a decrease in Ccl5/Rantes RNA levels and a transitory decline in sperm reserves in the testes of rats of TCDD-dosed dams.

Propagation of bovine spermatogonial stem cells in vitro

The access to sufficient numbers of spermatogonial stem cells (SSCs) is a prerequisite for the study of their regulation and further biomanipulation. A specialized medium and several growth factors were tested to study the in vitro behavior of bovine type A spermatogonia, a cell population that includes the SSCs and can be specifically stained for the lectin Dolichos biflorus agglutinin. During short-term culture (2 weeks), colonies appeared, the morphology of which varied with the specific growth factor(s) added. Whenever the stem cell medium was used, round structures reminiscent of sectioned seminiferous tubules appeared in the core of the colonies. Remarkably, these round structures always contained type A spermatogonia. When leukemia inhibitory factor (LIF), epidermal growth factor (EGF), or fibroblast growth factor 2 (FGF2) were added, specific effects on the numbers and arrangement of somatic cells were observed. However, the number of type A spermatogonia was significantly higher in cultures to which glial cell line-derived neurotrophic factor (GDNF) was added and highest when GDNF, LIF, EGF, and FGF2 were all present. The latter suggests that a proper stimulation of the somatic cells is necessary for optimal stimulation of the germ cells in culture. Somatic cells present in the colonies included Sertoli cells, peritubular myoid cells, and a few Leydig cells. A transplantation experiment, using nude mice, showed the presence of SSCs among the cultured cells and in addition strongly suggested a more than 10 000-fold increase in the number of SSCs after 30 days of culture. These results demonstrate that bovine SSC self-renew in our specialized bovine culture system and that this system can be used for the propagation of these cells.

Role and regulation of the fibroblast growth factor axis in human thyroid follicular cells

Thyroidal levels of fibroblast growth factor-2 (FGF-2) and fibroblast growth factor receptor 1 (FGFR1) are elevated in human thyroid hyperplasia. To understand the significance of this, effects of FGFR1 activation on normal human thyrocyte growth and function in vitro and the regulation of FGF-2 and FGFR1 expression have been examined. FGF-2 stimulated cell growth, as measured by cell counting, and inhibited thyroid function as measured by 125I uptake. Sensitivity to FGF-2 disappeared after 7 days, although FGFR1 expression was maintained. Thyroid-stimulating hormone (TSH, 300 mU/l) increased FGFR1 mRNA expression within 4 h and protein expression by 8 h. Exogenous FGF-2 decreased FGFR1 protein. Endogenous FGF-2 levels were low (approximately 1-2 pg/microg protein), and TSH treatment decreased these by 50%. Protein kinase C (PKC) activation increased FGF-2 mRNA and FGF-2 secretion within 2 h. This effect was enhanced (4.4-fold) when cells were cultured in TSH. We conclude that TSH stimulates FGFR1 but not FGF-2 expression. PKC activation stimulates FGF-2 synthesis and secretion, and TSH synergizes with PKC activators. Increases in FGFR1 or FGF-2 or in both may contribute to goitrogenesis.

HST-1/FGF-4 gene activation induces spermatogenesis and prevents adriamycin-induced testicular toxicity

We previously demonstrated expression of the HST-1/FGF-4 gene in the testis of normal adult animals, which suggests its possible role in spermatogenesis. For an understanding of its functional significance in the testis, conditional transgene expression was used. Precise genetic switches can be efficiently generated in a straightforward manner using adenovirus-carrying Cre recombinase, which means our new strategies promise to contribute substantially to a better and prompt understanding of the functions of genes in vivo by controlling the expression of any gene to any organ at any desired time. Our new method demonstrated for the first time that the specific gain of function of the HST-1/FGF-4 gene in the testis resulted in markedly enhanced spermatogenesis. To further investigate the function and therapeutic potency of HST-1/FGF-4, transgenic mice with enhanced HST-1/FGF-4 expression in the testis were exposed to adriamycin (ADR), an anticancer drug causing severe testicular toxicity. Degree of damage to spermatogenesis was assessed by sperm count, testicular weight, histology, and DNA ploidy. Induced expression of HST-1/FGF-4 markedly enhanced the recovery of ADR-induced testicular damage. Furthermore, adenoviruses carrying the HST-1/FGF-4 gene ameliorated testicular toxicity of ADR. These results with new adenovirus-mediated Cre/lox conditional mice indicated that HST-1/FGF-4 could be an important factor for spermatogenesis, presenting a new paradigm to treat impaired fertility.

Cell surface heparan sulfate proteoglycans: target and partners of the basic fibroblast growth factor in rat Sertoli cells

Basic fibroblast growth factor (bFGF) regulates diversified biological functions in rat Sertoli cells. This report demonstrates that bFGF inhibits steroidogenesis in developing rat Sertoli cells. Follicle stimulating hormone (FSH)-stimulated estradiol production was reduced by bFGF. Moreover, the amount of cytochrome P450 aromatase, responsible for the irreversible transformation of androgens into estrogens, is decreased by bFGF at the transcriptional level. The bFGF inhibitory effect was also observed in the presence of dibutyryl-cAMP, cholera toxin or RO-20-1724, all inducing high levels of cAMP, the second messenger of FSH. Heparan sulfate proteoglycans (HSPGs) were shown to be required as cofactors for bFGF signaling. Indeed, sodium chlorate, described to drastically decrease proteoglycan sulfation, abolishes the bFGF downregulation of FSH-stimulated estradiol synthesis previously observed. Glypican-1, syndecan-1 and -4, potential bFGF coreceptors, are mainly regulated at the transcriptional level. This report shows that the bFGF regulation of their expression specifically depends on the nature of HSPG and of the Sertoli cell developmental stage. In conclusion, HSPG are partners and the target of bFGF in rat Sertoli cells.

MT1-MMP in rat testicular development and the control of Sertoli cell proMMP-2 activation

Metalloproteases (MMPs) are likely to be involved in the restructuring events occurring in the testis throughout development. We here demonstrate that membrane-type 1 (MT1)-MMP, a physiological activator of proMMP-2 under TIMP-2 control, is present within the testis together with MMP-2 and TIMP-2. In the prepubertal testis MT1-MMP immunoreactivity was uniformly distributed, whereas in the adult it was confined to the apical compartment of the tubules, where meiosis and spermiogenesis occur. We further showed that the two cell lineages (somatic and germinal) expressed MT1-MMP and TIMP-2, whereas MMP-2 was of somatic origin. To get a better picture into proMMP-2 activation, use was made of a model of cultured Sertoli cells treated with FSH or co-cultured with germ cells to mimic an immature or a mature developmental period, respectively. We found that follicle-stimulating hormone enhanced the expression of MMP-2 and TIMP-2 but not of MT1-MMP, and promoted the activation of proMMP-2. In co-cultures, a tremendous elevation and activation of MMP-2 was observed, which might relate to the processed MT1-MMP form solely detected in germ cells. That MMP-2 synthesis and activation are under local (germ cells) and hormonal (follicle-stimulating hormone) regulation emphasizes the importance of MMPs in testicular physiology.

NF-kappa B is developmentally regulated during spermatogenesis in mice

To analyze NF-kappa B activity in the testis, we used murine transgenic lines carrying a LacZ reporter gene under the control of a NF-kappa B-responsive promoter (Schmidt-Ullrich et al. [1996] Dev 122:2117-2128). We constructed three independent lines containing the promoter of the gene encoding p105, the precursor of the p50 subunit. This promoter contains three NF-kappa B-binding sites in its proximal part. Our results show that in adult mice, the beta-galactosidase activity which reflects nuclear NF-kappa B activity, is first detected in spermatocytes at the pachytene stage and remains activated in the following steps of germ cell differentiation and maturation. Using transgenic mice carrying a p105nlslacZ construct with the 3 NF-kappa B sites mutated in the p105 promoter, we found a significant reduction in the transgene activity, confirming the important role of NF-kappa B in the activation of the transgene. To confirm the stage of induction during spermatogenesis, we analysed the beta-galactosidase activity in the testes from prepuberal mice in which cells synchrouneously enter meiosis. We detected the transgene activity at 18 days after birth, corresponding to the pachytene stage in spermatocytes. In nuclear extracts prepared from prepuberal mice, we found a peak of NF-kappa B DNA-binding activity made of p50 and p65 subunits at day 18 after birth, which remains high in the later stages. Further analysis showed that I kappa B alpha and beta, but not epsilon are expressed in the testes. Altogether, these data suggest that NF-kappa B factors are stage specifically controlled and may play a role during the development of sperm cells.

Detection of spatial localization of Hst-1/Fgf-4 gene expression in brain and testis from adult mice

HST-1, a member of the fibroblast growth factor (FGF) family (FGF-4), has been shown to be a signaling molecule whose expression is essential for embryonic development. However, HST-1/FGF-4 expression has not been detected or reported in adult tissues so far analysed. To investigate whether there is a possible role of HST-1/FGF-4 in adult stage, we have carried out a highly sensitive RT-PCR analysis of Hst-1/Fgf-4 gene expression in adult mice tissues. Results show Hst-1/Fgf-4 gene expression in the nervous system, intestines, and testis of normal adult mice. In situ hybridization technique was used to localize Hst-1/Fgf-4 gene expression in the cerebellum and testis from 10-week-old mice. Cell type-specific gene expression was detected: Purkinje cells in the cerebellum and Sertoli cells in testis. These findings suggest that the Hst-1/Fgf-4 gene also plays an important role in adult tissues, and may offer insights into the biological significance of HST-1/FGF-4 in cerebellar and testicular functions.

45T-1, an established cell line with characteristics of Sertoli cells, forms organized aggregates in vitro after exposure to tumor necrosis factor alpha

In the testis TNF is produced by germinal cells. The putative role of tumor necrosis factor alpha (TNF) in development and differentiation was investigated in 45T-1 mouse cell cultures, a cell line with characteristic markers of Sertoli cells, established from transgenic mouse families expressing the polyoma large T antigen in their testes. Exposure to TNF elicited a gradual assembly of the cells of the monolayer into highly organized spheroids. The first morphological sign of the changes was detected one week after TNF treatment by anti-desmin immunostaining which showed the formation of foci in the culture consisting of several hundred cells connected by an increasing number of cell contacts. Between days 10-20 the cells formed large ovoid or vermiform aggregates covered by several layers of flat, elongated cells. These cells extended septae into the inner mass of the spheroids consisting of loosely arranged, large polygonal or palisadic cells. The spheroids were surrounded by radially arranged elongated cells covered by small blebs. TNF treatment upregulated laminin expression in 45T-1 cell cultures, which is known to induce formation of cord-like structures by Sertoli cells in vitro. Coculturing 45T-1 cells with immortalized germinal cells or TNF-producing HeLa cells also lead to the formation of spheroids. These observations suggest that TNF production of germinal cells might contribute to the organization/differentiation of Sertoli cells.

mRNAs encoding a von Ebner's-like protein and the Huntington disease protein are induced in rat male germ cells by Sertoli cells

The success of spermatogenesis is dependent upon closely coordinated interactions between Sertoli cells and germ cells. To identify specific molecules that mediate interactions between somatic cells and germ cells in the rat testis, Sertoli cell-germ cell co-cultures and mRNA differential display were used. Two cDNAs, clone 1 (660 nucleotides) and clone 2 (390 nucleotides) were up-regulated when Sertoli cells were co-cultured with pachytene spermatocytes or round spermatids. Northern blot analyses confirmed the differential display expression patterns. Sequence analyses indicated that clone 1 was similar to a von Ebner's gland protein (87% at the nucleotide level and 80% at the amino acid level) and clone 2 was identical to a region of the Huntington disease protein. The von Ebner's-like protein mRNA was induced after 4 h of co-culture, while the Huntington disease protein required 18 h of co-culture for expression. The von Ebner's-like protein was induced in germ cells by a secreted Sertoli cell factor(s) smaller than 10 kDa that is sensitive to freezing and thawing or boiling. The Huntington disease protein was induced in germ cells by a Sertoli cell secreted factor(s) larger than 10 kDa which survives freezing and thawing, but is inactivated by boiling.

Rodent Leydig cell tumorigenesis: a review of the physiology, pathology, mechanisms, and relevance to humans

Leydig cells (LCs) are the cells of the testis that have as their primary function the production of testosterone. LCs are a common target of compounds tested in rodent carcinogenicity bioassays. The number of reviews on Leydig cell tumors (LCTs) has increased in recent years because of its common occurrence in rodent bioassays and the importance in assessing the relevance of this tumor type to humans. To date, there have been no comprehensive reviews to identify all the compounds that have been shown to induce LCTs in rodents or has any review systematically evaluated the epidemiology data to determine whether humans were at increased risk for developing LCTs from exposure to these agents. This review attempts to fill these deficiencies in the literature by comparing the cytology and ontogeny of the LC, as well as the endocrine and paracrine regulation of both normal and tumorigenic LCs. In addition, the pathology of LCTs in rodents and humans is compared, compounds that induce LC hyperplasia or tumors are enumerated, and the human relevance of chemical-induced LCTs is discussed. There are plausible mechanisms for the chemical induction of LCTs, as typified by agonists of estrogen, gonadotropin releasing hormone (GnRH), and dopamine receptors, androgen receptor antagonists, and inhibitors of 5alpha-reductase, testosterone biosynthesis, and aromatase. Most of these ultimately involve elevation in serum luteinizing hormone (LH) and/or LC responsiveness to LH as proximate mediators. It is expected that further work will uncover additional mechanisms by which LCTs may arise, especially the role of growth factors in modulating LC tumorigenesis. Regarding human relevance, the pathways for regulation of the hypothalamo-pituitary-testis (HPT) axis of rats and humans are similar, such that compounds that either decrease testosterone or estradiol levels or their recognition will increase LH levels. Hence, compounds that induce LCTs in rats by disruption of the HPT axis pose a risk to human health, except for possibly two classes of compounds (GnRH and dopamine agonists). Because GnRH and prolactin receptors are either not expressed or are expressed at very low levels in the testes in humans, the induction of LCTs in rats by GnRH and dopamine agonists would appear not to be relevant to humans; however, the potential relevance to humans of the remaining five pathways of LCT induction cannot be ruled out. Therefore, the central issue becomes what is the relative sensitivity between rat and human LCs in their response to increased LH levels; specifically, is the proliferative stimulus initiated by increased levels of LH attenuated, similar, or enhanced in human vs. rat LCs? There are several lines of evidence that suggest that human LCs are quantitatively less sensitive than rats in their proliferative response to LH, and hence in their sensitivity to chemically induced LCTs. This evidence includes the following: (1) the human incidence of LCTs is much lower than in rodents even when corrected for detection bias; (2) several comparative differences exist between rat and human LCs that may contribute, at least in part, to the greater susceptibility of the rat to both spontaneous and xenobiotic-induced LCTs; (3) endocrine disease states in man (such as androgen-insensitivity syndrome and familial male precocious puberty) underscore the marked comparative differences that exist between rats and man in the responsiveness of their LC's to proliferative stimuli; and (4) several human epidemiology studies are available on a number of compounds that induce LCTs in rats (1,3-butadiene, cadmium, ethanol, lactose, lead, nicotine) that demonstrate no association between human exposure to these compounds and induction of LC hyperplasia or adenomas. (ABSTRACT TRUNCATED)

Plasminogen activator inhibitor-1 is expressed in cultured rat Sertoli cells

Sertoli cells secrete plasminogen activators (PAs) on both sides of the blood-testis barrier, i.e., in the basal and apical compartments of the seminiferous tubules, whereas peritubular cells secrete plasminogen activator inhibitor-1 (PAI-1), a fast-acting and specific PA inhibitor. While it is likely that PAI-1 produced by peritubular cells counteracts the basal secretion of PA, the nature of the PA inhibitor acting in the apical compartment remains to be demonstrated. In the present study, we showed that Sertoli cells recovered from 20-day-old rats and cultured contained a transcript of 3-3.2 kilobases, which hybridized specifically to a PAI-1 cDNA probe (Northern blot). We verified that the observed PAI-1 transcript could not result solely from the peritubular cells (weakly contaminating the Sertoli cell cultures), by comparing PAI-1 mRNA levels of Sertoli and peritubular cells recovered from 20-day-old rats and cultured. We also demonstrated that cultured Sertoli cells secreted a protein that complexed with tissue-type PA (zymography), indicating that it was biologically active. This protein comigrated with purified PAI-1 as a doublet of 46 and 49 kDa (Western blot). The trophic hormone FSH decreased PAI-1 messenger RNA as well as immunoreactive PAI-1 protein (probably via the cAMP protein kinase A pathway), whereas transforming growth factor ss1 and basic fibroblast growth factor (in a nanomolar concentration) increased both of these. These observations support the hypothesis that PAI-1 is expressed by Sertoli cells and is under a complex hormonal (FSH) and paracrine and/or autocrine control exerted at least by basic fibroblast growth factor and transforming growth factor ss1.

Up-regulation and down-regulation of genes expressed in cocultures of rat Sertoli cells and germ cells

To better understand the molecular interactions between somatic and germ cells in the mammalian testis, we have begun to analyze with mRNA differential display changes in gene expression induced by coculturing rat Sertoli cells and germ cells. We have identified 10 cDNAs that are either down-regulated or up-regulated in cocultures of germ cells and Sertoli cells. Three genes expressed in Sertoli cells and three genes expressed in germ cells were down-regulated in Sertoli cell-germ cell cocultures, whereas four genes were up-regulated in the cocultures. Northern blot analysis was used to establish the expression pattern of the mRNAs encoded by the cDNAs and to define the sizes of the differentially expressed mRNAs. Sequence analysis of the cDNAs and computer searches against the GenBank and EMBL DNA databases were used to relate the ten cDNAs to known genes. Of the three Sertoli cell cDNAs, one appeared identical to transferin, while the other two shared regions of similarity to an endoplasmic reticulum stress protein and to a pro-alpha 2 XI collagen, respectively. The three germ cell cDNAs shared sequences with fibronectin, with a basic fibroblast growth factor receptor and with an IgG gamma 2b, respectively. The four cDNAs that were up-regulated in the Sertoli-germ cell cocultures showed similarity to an isoform of casein kinase 1 delta, to an epidermal growth factor, to a statin-related protein, and to an integral membrane glycoprotein. These data demonstrate that a number of specific genes are up- and down-regulated when germ cells and Sertoli cells are cocultured, and suggest these genes are important in cell to cell communication during spermatogenesis.

Regulation of rat testis gonocyte proliferation by platelet-derived growth factor and estradiol: identification of signaling mechanisms involved

To determine what factors regulate gonocyte proliferation in newborn rats, we first examined the expression of several signal transduction molecules by immunocytochemistry in 3-day-old rat testis sections. We found that gonocytes specifically expressed the iota and zeta isoforms of protein kinase (PK) C (PKC) and the phosphatidylinositol 3-kinase (PI3-K). Because both the zeta PKC and PI 3-K have been shown to play a role in platelet-derived growth factor (PDGF)-induced cell proliferation, we examined the effects of PDGF on gonocytes. For this, we developed a method to obtain highly purified and viable gonocytes in culture. After enzymatic digestion, differential adhesion, and two successive gradient fractionations, the gonocyte suspension obtained was over 90% pure, as assessed by light microscopy. The viability of cultured gonocytes exceeded 90% after 48 h in the presence of 2.5% FBS used as a survival factor. Immunodetection studies showed that isolated gonocytes expressed zeta PKC, PI 3-K, and the PDGF receptor. Treatment with 10 ng/ml PDGF induced a 4-fold increase of bromodeoxyuridine incorporation into gonocytes (from 5% proliferative gonocytes under basal conditions to 20% in the presence of PDGF). Because neonatal Sertoli cells secrete high levels of the growth promoting steroid, 17 beta-estradiol, we also tested its effect and found that it induced gonocyte proliferation at a level comparable with that of PDGF and that this effect was blocked by the estrogen receptor antagonist, ICI 164384. The combination of PDGF and estradiol, however, was not additive, suggesting that their effects were mediated by common molecular target(s). These results demonstrate that PDGF and estradiol activate gonocyte proliferation in vitro, suggesting that they may act as the physiological regulators of gonocyte development in vivo.

Tumor necrosis factor-alpha regulates plasminogen activator inhibitor-1 in rat testicular peritubular cells

We examined the regulation by tumor necrosis factor-alpha (TNF alpha) of plasminogen activator inhibitor-1 (PAI-1) in cultured peritubular cells recovered from 20-day-old rat testes. We demonstrated that TNF alpha in a nanomolar dose range stimulated PAI-1 messenger RNA (mRNA; Northern blots) as well as immunoreactive (Western blots) and bioactive (Stachrom) PAI-1 protein. Induction of PAI-1 mRNA started 4 h after the addition of TNF alpha (2.5-fold increase) and peaked (7-fold increase) after 24 h of treatment. Actinomycin D and cycloheximide inhibited the effects of TNF alpha on PAI-1 mRNA, suggesting that ongoing RNA and protein syntheses were required. The combined actions of transforming growth factor-alpha (TGF alpha), a potent inducer of PAI-1, and TNF alpha on PAI-1 were less than additive, suggesting the activation of some common pathway. TNF alpha action on PAI-1, like that of TGF alpha demonstrated previously, was masked by a preexposure to phorbol myristate acetate (a stimulator of protein kinase C) and strongly reduced by staurosporine (an inhibitor of the protein kinase C). Furthermore, using genistein to inhibit tyrosine kinase activity, we not only blocked the action of TGF alpha on PAI-1 [initiated upon binding to the tyrosine kinase epidermal growth factor/TGF alpha receptor (EGFR)], but also markedly reduced that of TNF alpha. Finally, TNF alpha, at a dose range that stimulated PAI-1, enhanced EGFR mRNA levels and EGF binding. Together, the present findings suggest that some of the biological effects of TNF alpha on PAI-1 might be secondary to de novo synthesis of EGFR. Because TNF alpha probably originates from testicular macrophages, such a regulation of PAI-1 by TNF alpha may occur in the context of physiological interactions between the testis and the immune system.