Stimulation of rat Sertoli cell secretory activity in vitro by germ cells and residual bodies

The direct influence of germ cells and residual bodies on Sertoli cell basal and FSH-stimulated secretion of androgen-binding protein (ABP) was studied using Sertoli cells, recovered from 20-day-old rats, cultured alone or cocultured with a crude germ cell preparation from adult rats or with pachytene spermatocytes, round spermatids or populations of residual bodies enriched by centrifugal elutriation. The effect of a rat liver epithelial cell line (LEC) on Sertoli cell function was also tested. Addition of a crude germ cell preparation increased basal and FSH-stimulated ABP secretion. Pachytene spermatocytes and residual bodies adhered to the Sertoli cell monolayer to a much greater extent than did round spermatids. Addition of pachytene spermatocytes markedly enhanced basal and FSH-stimulated ABP secretion over 12 days of culture. Round spermatids and residual bodies stimulated ABP secretion although to a lesser extent than did spermatocytes. Furthermore, the increase of FSH-stimulated ABP levels was not maintained after 4 or 8 days of culture. LEC also enhanced basal and FSH-induced ABP levels but the increase of FSH-induced ABP production was only observed until Day 8 of culture. The influence of LEC on Sertoli cell secretion could be mediated through the production of an extracellular matrix. It is concluded that germ cells, particularly pachytene spermatocytes, can directly stimulate Sertoli cell secretory activity in vitro.     

Regulation of tissue inhibitor of metalloproteinases-1 in rat Sertoli cells: induction by germ cell residual bodies, interleukin-1alpha, and second messengers

In the testis, FSH has been shown to induce the expression and secretion of tissue inhibitor of metalloproteinases-1 (TIMP-1) from Sertoli cells in vitro. This study was performed to elucidate further the cellular origin of testicular TIMP-1 and its expression by hormonal and paracrine factors. This is the first report on the expression of testicular TIMP-1 in vivo. TIMP-1 mRNA in whole testis was decreased after hypophysectomy and strongly increased by the injection of FSH-S17 to hypophysectomized rats. Primary cultures of both peritubular and Sertoli cells showed basal expression of TIMP-1 mRNA. In contrast, we were unable to detect TIMP-1 mRNA in Leydig cells, freshly isolated immature germ cells (primary spermatocytes and spermatids), or residual bodies. We further show that treatment of Sertoli cells with 8-(4-chlorophenyl)thio-cAMP (8-CPTcAMP) in combination with 12-O-tetradecanoylphorbol 13-acetate (TPA) or Ca(2+) inducers (calcium ionophore A23187 or thapsigargin) had additive (TPA) and synergistic effects (Ca(2+)) on the level of TIMP-1 mRNA and secreted protein. We also show that both the level of TIMP-1 mRNA and secreted protein from Sertoli cells were strongly increased by residual bodies, as well as by the cytokine interleukin-1alpha. TIMP-1 was not up-regulated by either 8-CPTcAMP or interleukin-1alpha in peritubular cells. In contrast to the regulated secretory fraction of TIMP-1, we also detected constitutively expressed immunoreactive TIMP-1 in the nucleus of Sertoli cells, suggesting a role of nuclear TIMP-1 in these cells. In conclusion, our data show that secretion of TIMP-1 from Sertoli cells is highly regulated by hormonal and local processes in the testis, indicating that TIMP-1 is of physiological importance during both testicular development and spermatogenesis.     

Induction of interleukin-1alpha production in murine Sertoli cells by interleukin-1

In the present study we examined the involvement of interleukin (IL)-1alpha, -1beta, FSH, and lipopolysaccharide (LPS) in the regulation of IL-1alpha and -1beta production by Sertoli cells under in vitro conditions. Sertoli cell cultures from immature mice produced constitutively basal levels of intracellular IL-1alpha. Stimulation of Sertoli cell cultures with LPS (5 microgram/ml) resulted in a maximal production of intracellular IL-1alpha 2 h after the stimulation. Thereafter, these levels decreased but remained significantly higher within 24 h after stimulation than those in control cultures. The effect of LPS on IL-1alpha production was dose dependent. FSH did not show any effect on intracellular IL-1alpha production by Sertoli cells. IL-1alpha could not be detected in supernatants of unstimulated or stimulated Sertoli cell cultures. Sertoli cell cultures stimulated with recombinant IL-1alpha induced optimal intracellular levels of IL-1alpha within 2 h of stimulation. These levels remained high 24 h after stimulation. However, stimulation of Sertoli cell cultures with IL-1beta induced a peak of IL-1alpha production 8 h after stimulation. These levels decreased 24 h after the stimulation but were still found to be significantly higher than those in control cultures. The addition of IL-1 receptor antagonist (IL-1ra) to Sertoli cell cultures did not significantly alter their capacity to produce IL-1alpha. However, the stimulatory effects of recombinant IL-1alpha on IL-1alpha production by Sertoli cell cultures were reversed by the concomitant addition of recombinant IL-1ra. No immunoreactive IL-1beta could be detected in lysates or conditioned media of immature murine Sertoli cells under any of the stimulatory conditions outlined. Our results may suggest the involvement of physiological (IL-1) and pathophysiological factors (LPS) in the regulation of spermatogenesis and spermiogenesis processes and male fertility.     

Cytological and expression studies and quantitative analysis of the temporal and stage-specific effects of follicle-stimulating hormone and testosterone during cocultures of the normal human seminiferous epithelium

In vitro culturing of normal human seminiferous epithelium remains largely unexplored. To study normal human spermatogenesis in vitro, we used a micromethod for the purification and culture of Sertoli cells, spermatogonia A, spermatocytes, and early round spermatids. Cytological quantitative data for Sertoli and premeiotic germ cell cocultures isolated from normal testicular biopsies demonstrated that cells were able to proliferate (4%), complete meiosis (6.7%), and differentiate into late round (54%), elongating (49%), and elongated (17%) spermatids at similar in vivo time delays (up to 16 days) in response to FSH + testosterone stimulation. Cells maintained normal meiotic segregation, chromosome complements, and specific gene expression profiles. Follicle-stimulating hormone + testosterone stimulated spermatogonia proliferation and Sertoli cell survival. Follicle-stimulating hormone and especially FSH + testosterone increased diploid germ cell survival during the first week, whereas only FSH + testosterone was able to inhibit cell death during the second week of culture. Follicle-stimulating hormone and especially FSH + testosterone also stimulated meiosis resumption, although this was restricted to late pachytene and secondary spermatocytes. In contrast, spermiogenesis was only stimulated by FSH + testosterone. Expression studies showed that apoptosis was induced in the nucleus of diploid cells, and in nuclear and cytoplasmic compartments of spermatids, mainly triggered by the Fas pathway. Although junctional complexes between Sertoli and premeiotic germ cells were partially reacquired, the same did not apply to spermatids, suggesting that FSH potentiated by testosterone was unable to render Sertoli cells competent to bind round spermatids.     

Apoptosis is physiologically restricted to a specialized cytoplasmic compartment in rat spermatids

Cytoplasmic caudal tags of maturing spermatids condense and are detached from the spermatidal cells just before the spermatids are released as spermatozoa. The detached cytoplasmic masses are termed "residual bodies." Features of residual bodies seem to be compatible with those of apoptosis and, just as occurs with apoptotic bodies, residual bodies are phagocytosed by Sertoli cells. Since in vitro studies have demonstrated that nucleus and cytoplasm apoptosis events can be independent phenomena, we reasoned that apoptosis pathways might be restricted to the caudal tag of the maturing spermatids in order to originate residual bodies. Consistent with this idea, here we showed that annexin V specifically bound the membranes of isolated residual bodies and that expression levels of caspase-1, c-jun, p53, and p21 were specifically increased in these cytoplasmic compartments. Electron microscopy of cytoplasmic lobes and residual bodies confirmed that their ultrastructural features were those of apoptosis. These data indicate that the mechanism responsible for the formation of residual bodies is similar to that for apoptotic bodies; and the study presents evidence, for the first time, that apoptotic signaling molecules can be restricted to a cytoplasmic compartment and proceed in the presence of a healthy nucleus.     

The role of tumor necrosis factor-alpha and interleukin-1 in the mammalian testis and their involvement in testicular torsion and autoimmune orchitis

This review will focus the roles of TNF-alpha, IL-1 alpha, and IL-1 beta in the mammalian testis and in two testicular pathologies, testicular torsion and orchitis. TNF alpha in the testis is produced by round spermatids, pachytene spermatocytes, and testicular macrophages. The type 1 TNF receptor has been found on Sertoli and Leydig cells and numerous studies suggest a paracrine mode of action for TNF alpha in the normal testis. IL-1 alpha has been reported to be produced by Sertoli cells, testicular macrophages, and possibly postmeiotic germ cells. IL-1 receptors have been reported on Sertoli cells, Leydig cells, testicular macrophages, and germ cells suggesting both autocrine and paracrine functions. While these proinflammatory cytokines have important roles in normal testicular homeostasis, an elevation of their expression can lead to testicular dysfunctions. Testicular torsion is a clinical pathology with results in testicular ischemia and surgical intervention is often required for reperfusion. A pivotal role for IL-1beta in the pathology of testicular torsion has been recently described whereby an increase in IL-1beta production after reperfusion of the testis is correlated with the activation of the stress-related kinase, c-jun N-terminal kinase, and ultimately resulting in neutrophil recruitment to the testis and germ cell apoptosis. In autoimmune orchitis, on the other hand, TNF alpha produced by T-lymphocytes and macrophages of the testis has been implicated in the development and progression of the disease. Thus, both proinflammatory cytokines, TNF alpha and IL-1, have significant roles in normal testicular functions as well as in certain testicular pathologies.     

Aspects of germinal cyst and sperm development in Poecilia latipinna (Teleostei: Poeciliidae).

The structure of the testis of Poecilia latipinna is described with particular reference to Sertoli cell-germ cell relationships during development and maturation of the germinal cyst. The cyst develops when primary spermatocytes become surrounded by a single layer of Sertoli cells at the testis periphery. As spermatogenesis and then spermiogenesis proceed, the cyst moves centrally in the testis toward the ducts comprising the vasa efferentia. In addition to being a structural part of the germinal cyst, the Sertoli cells phagocytize residual bodies cast off by developing spermatids and form an association with mature bodies cast off by developing spermatids and form an association with mature sperm, which resembles that observed in mammals, before the sperm are released into the vasa efferentia as a spermatozeugmata. The results of this investigation are discussed in view of what is known concerning testis structure in other teleosts and similarities between cell functions in teleosts and mammals. It is concluded that teleost Sertoli cells, teleost lobule boundary cells and mammalian Sertoli cells are homologous.     

Role of sulfated glycoprotein-1 (SGP-1) in the disposal of residual bodies by sertoli cells of the rat

Sulfated glycoprotein-1 (SGP-1) is a polypeptide secreted by Sertoli cells in the rat. Sequence analysis revealed a 76% sequence similarity with human prosaposin produced by various cell types. Human prosaposin is a 70 kDa protein which is cleaved in the lysosomes into four 10–15 kDa polypeptides termed saposins A, B, C, and D. The function of lysosomal saposins is to either solubilize certain membrane glycolipids or to form complexes with lysosomal enzymes and/or their glycolipid substrate to facilitate their hydrolysis. The present investigation dealt with the delivery of SGP-1 into the phagosomes of Sertoli cells; these phagosomes contain the residual bodies which detach from the late spermatids at the time of spermiation. Immunogold labeling with anti-SGP-1 antibody was found over Sertoli cell lysosomes, but was absent from phagosomes formed after phagocytosis of spermatid residual bodies in the apical Sertoli cell cytoplasm in stages VIII and early IX of the cycle of the seminiferous epithelium. The phagosomes found later in the basal Sertoli cell cytoplasm in stages IX and X of the cycle became labeled with the antibody as the components of the residual bodies rapidly underwent lysis and disappeared from the Sertoli cells. Sertoli cell lysosomes isolated by cell fractionation (estimated purity of 80%) were found to contain a 65 kDa form of SGP-1 or prosaposin, as well as the 15 kDa polypeptides or saposins. Thus, it appears that this unique lysosomal form of SGP-1 reached the Sertoli cell phagosomes and that their derived polypeptides, the saposins, must play a role in the hydrolysis of membrane glycolipids found in phagocytosed residual bodies. © 1995 Wiley-Liss, Inc.     

Opposite regulation of connexin33 and connexin43 by LPS and IL-1alpha in spermatogenesis

The gap junction proteins, connexins (Cxs), are present in the testis, and among them, Cx43 play an essential role in spermatogenesis. In the present study, we investigated the testicular expression and regulation of another Cx, Cx33, previously described as a negative regulator of gap junction communication. Cx33 mRNA was present in testis and undetectable in heart, liver, ovary, and uterus. In the mature testis, Cx33 was specifically immunolocalized in the basal compartment of the seminiferous tubules, whereas Cx43 was present in both seminiferous tubule and interstitial compartments. During stages IX and X of spermatogenesis, characterized by Sertoli cell phagocytosis of residual bodies, Cx43 was poorly expressed within seminiferous tubules, while Cx33 signal was strong. To evaluate the role of phagocytosis in the control of Cx33 and Cx43 expression, the effect of LPS was analyzed in the Sertoli cell line 42GPA9. We show herein that phagocytosis activation by LPS concomitantly stimulated Cx33 and inhibited Cx43 mRNA levels. These effects appear to have been mediated through IL-1, because the exposure of Sertoli cells to the IL-1 receptor antagonist partly reversed these effects. IL-1 enhanced and reduced, respectively, the levels of Cx33 and Cx43 mRNA in a time- and dose-dependent manner. These data reveal that Cx33 and Cx43 genes are controlled differently within the testis and suggest that these two Cxs may exert opposite and complementary effects on spermatogenesis. Sertoli cell; germ cell proliferation     

Immunolocalization of inhibin and activin alpha and betaB subunits and expression of corresponding messenger RNAs in the human adult testis

Inhibin B is a testicular peptide hormone that regulates FSH secretion in a negative feedback loop. Inhibin B is a dimer of an alpha and a beta(B) subunit. In adult testes, the cellular site of production is still controversial, and it was hypothesized that germ cells contribute to inhibin B production. To determine which cell types in the testes may produce inhibin B, the immunohistochemical localization of the two subunits of inhibin B were examined in adult testicular biopsies with normal spermatogenesis, spermatogenic arrest, or Sertoli cell only (SCO) tubules. Moreover, using in situ hybridization with mRNA probes, the mRNA expression patterns of inhibin alpha and inhibin/activin beta(B) subunits have been investigated. In all testes, Sertoli cells and Leydig cells showed positive immunostaining for inhibin alpha subunit and expressed inhibin alpha subunit mRNA. Using inhibin beta(B) subunit immunoserum on testes with normal spermatogenesis and with spermatogenic arrest, intense labeling was located in germ cells from pachytene spermatocytes to round spermatids but not in Sertoli cells. Inhibin beta(B) subunit mRNA expression was intense in germ cells from spermatogonia to round spermatids and in Sertoli cells in these testes. In testes with SCO, high inhibin beta(B) subunit mRNA labeling density was observed in both Sertoli cells and Leydig cells, whereas beta(B) subunit immunostaining was negative for Sertoli cells and faintly positive for Leydig cells. These results agree with the recent opinion that inhibin B in adult men is possibly a joint product of Sertoli cells and germ cells.     

A quantitative study of Sertoli cell and germ cell populations as related to sexual development and aging in the stallion

Testes from 47 stallions, 1-20 yr of age, were used to examine the influence of age on Sertoli and germ cell populations as well as on functional activity of Sertoli cells. For these stallions, the number of Sertoli cells per paired testes declined linearly with age, and was only 41.7% as great at age 20 as at age 2. However, development of reproductive organs proceeded until age 12-13, as evident from increases in paired testes weight and quantitative rates of spermatozoal production. Although the absolute number of Sertoli cells declined during this period of development, individual Sertoli cells displayed a remarkable capacity to accommodate greater numbers of developing germ cells. Between age 2 and age 12, the mean numbers of developing spermatogonia, young primary spermatocytes, old primary spermatocytes, and round spermatids supported by each Sertoli cell at Stage I of spermatogenesis increased by 49, 176, 153, and 161%, respectively.     

The p38 MAPK pathway mediates interleukin-1-induced Sertoli cell proliferation

We have reported earlier that interleukin-1 (IL-1) is a potent growth factor for immature Sertoli cells (somatic cells in the testis required for testicular development and later spermatogenesis) and that this effect is synergistic with the mitogenic effect of follicle-stimulating hormone (FSH). The aim of the present study was to determine whether MAPK pathways are involved in mediating the mitogenic effect of IL-1 on Sertoli cells. Western blotting revealed that IL-1alpha activated p38 MAPK and JNK/SAPK, but not ERK, in Sertoli cells from 8- or 9-day-old rat. The inhibitor of p38 MAPK SB203580 attenuated the IL-1alpha-induced proliferation of Sertoli cells, as assessed by (3)H-thymidine incorporation and supravital staining as well as by direct cell counting. We conclude that the p38 MAPK pathway mediates the proliferative effect of IL-1alpha on immature Sertoli cells in vitro. Since the mitogenic effect of FSH is mediated via ERK, the synergistic action of IL-1alpha and FSH may be explained by their different intracellular signalling pathways. Induction of IL-1 by inflammation, infection or other tissue injuries may result in testicular damage by interfering with normal Sertoli cell development and thus future spermatogenesis.     

Developmental regulation of Sertoli cell aromatase activity and plasminogen activator production by hormones, retinoids and the testicular paracrine factor, PModS.

Testicular peritubular cells produce a paracrine factor termed PModS that has dramatic effects on Sertoli cell function in vitro. The current study was designed to examine the actions of PModS and hormones on Sertoli cell aromatase activity and plasminogen activator production at various stages of pubertal development. Sertoli cells were isolated from 10-, 20-, and 35-day-old rats (ages correspond to prepubertal, midpubertal, and late-pubertal stages of development). Aromatase activity was found to be high and hormone-responsive in prepubertal Sertoli cells and to decline and be nonresponsive to hormones in late-pubertal Sertoli cells. FSH was the only hormone found to influence aromatase activity and estrogen production. PModS alone was not found to affect aromatase activity at any of the developmental stages examined. Interestingly, PModS was found to suppress the ability of FSH to stimulate aromatase activity and estrogen production in midpubertal Sertoli cells. Results imply that PModS may promote Sertoli cell differentiation to a more adult stage of development that is less responsive to FSH in stimulating aromatase activity. In contrast to aromatase activity, plasminogen activator production was found to increase during pubertal development. Production of Sertoli cell tissue-type plasminogen activator (tPa) was stimulated by FSH at each of the developmental stages examined, whereas production of urokinase-type plasminogen activator (uPa) was influenced by FSH only in prepubertal Sertoli cells. Insulin also stimulated uPa and tPa production by prepubertal Sertoli cells, and retinol significantly suppressed uPa production and the ability of FSH to stimulate tPa production by midpubertal Sertoli cells.     

Season but not age affects Sertoli cell number in adult stallions.

To evaluate the effect of age and season on Sertoli cell number per paired testes, ratio of germ cells per Sertoli cell, and daily sperm production, testes were obtained from 184 adult (4-20 yr) stallions at slaughter throughout one year. Numbers of Sertoli cells or germ cells were derived from nuclear volume density, volume of individual nuclei, and parenchymal volume. Germ cell to Sertoli cell ratios were calculated from cell numbers. Regression analysis was used to detect age-related differences in the breeding season (May-Jul) or throughout the year. A two-way analysis of variance was used to evaluate time periods (Nov-Jan, Feb-Apr, May-Jul, and Aug-Oct) and age groups (4-5.5, 6-12.5, or 13-20 yr). Paired parenchymal weight and daily sperm production per horse increased significantly with age. Neither regression nor analysis of variance revealed an effect of age on Sertoli cell number. While season contributed (p less than 0.01) to variation in Sertoli cell number per horse, there was no (p greater than 0.05) age x season interaction or age effect on Sertoli cell number. In testes obtained from adult stallions, age had no effect on the number of Sertoli cells per horse, the ratio of maturation-phase spermatids to Sertoli cells, or the ratio of all stage VIII germ cells to Sertoli cells. Given no age effect within a given season on Sertoli cell number per horse, the number of Sertoli cells in the recrudesced testis of the breeding season probably is not significantly different for a given stallion between 4 and 20 yr of age.     

Proceedings: The role of the Sertoli cell in phagocytosis of the residual bodies of spermatids

The fate of residual bodies which form as spermatids are released from the seminiferous epithelium has been studied as part of a cytological investigation of the Sertoli cells during the stages of rat spermatogenesis. Testes from normal adult rats were fixed by whole body perfusion. All 14 stages of rat spermatogenesis were identified and studied by light and electron microscopy. Residual bodies are released at Stage 8 and are found in the luminal spaces of the seminiferous epithelium. During Stage 9 they appear to migrate peripherally in channels of the Seroli cell cytoplasm. During this migration, lysosomal-like bodies surround the residual bodies and appear to be involved in the degradative process. A considerable proportion of the lipid material persists and forms basal collections in the Sertoli cells. The lipid inclusions reach a peak at Stages 13 and 14 of the cycle and persist until Stage 2 and 3. Some lipid inclusions persist until Stage 4 to 7 when noticeable decrease occurs corresponding to the peripheral migration of maturing spermatids.     

Study in vitro of the phagocytic function of Sertoli cells in the rat

Summary Aspects of the interaction between residual bodies/cytoplasts from elongated spermatids (RB/CES) and Sertoli cells were studied in vitro. Highly enriched Sertoli cells (91%; experiment A), very highly enriched Sertoli cells (>96%; experiment B), as well as peritubular cells were isolated from testes of 20-day-old rats by means of hypotonic treatment. Isolated Sertoli cells and peritubular cells were also prepared from 45-day-old rats (experiment C). RB/CES were isolated by centrifugal elutriation from testes of rats aged 90–120 days. The kinetics of adhesion of RB/CES to Sertoli cells were similar in all experiments. FSH accelerated binding of RB/CES but markedly reduced the number of RB/CES phagocytosed. Co-culture of the highly enriched Sertoli cells from experiments A and C with isolated peritubular cells did not change the kinetics of adhesion of RB/CES. However, when the contamination of Sertoli cells by peritubular cells was at a minimum (experiment B), addition of peritubular cells induced a slight but significant stimulation of the binding of RB/CES. Transmission electron microscopy revealed the following events within 24 h of co-culture: adhesion of the RB/CES to microvilli of Sertoli cells; internalization of RB/CES; lysis of the membrane of RB/CES; total digestion. Therefore, FSH and peritubular cells modulate the interaction in vitro between Sertoli cells and RB/CES, and the different steps of residual body disposal can be reproduced in co-culture. The co-culture model described in this study provides a useful system for the study of phagocytic activity by Sertoli cells.     

Immunofluorescent localization of PGK-1 and PGK-2 isozymes within specific cells of the mouse testis

The ubiquitous isozyme of phosphoglycerate kinase, PGK-1, and the testis-specific isozyme, PGK-2, have been localized to specific cells of the testis by indirect immunofluorescence on Bouin's fixed testis sections. The earliest cell of the spermatogenic series in which PGK-2 is detectable by immunofluorescence is the Stage 12 spermatid. The intensity of fluorescence increases as the spermatids progress to later stages and is strong in both released spermatids and their residual bodies. PGK-2 is not detectable in premeiotic germinal cells or somatic cells of the testis. Specific fluorescence for PGK-1 is localized to the somatic cells of the testis: the interstitial and Sertoli cells.     

Inhibition of hepatocyte growth factor induction in human dermal fibroblasts by interleukin-1 and its prevention by interferon-gamma

Hepatocyte growth factor (HGF) is one of the vital factors for liver regeneration. HGF production is induced by the activation of protein kinase A and protein kinase C-mediated pathways, interleukin (IL)-1, tumor necrosis factor (TNF)-alpha, and epidermal growth factor (EGF) in mesenchymal cells. We here report that IL-1 and TNF-alpha, hitherto regarded as HGF inducers, potently inhibited HGF production stimulated by other HGF inducers. IL-1alpha, IL-1beta, and TNF-alpha alone had minimal stimulating effects on HGF production in human dermal fibroblasts, but they strongly inhibited production of HGF induced by cholera toxin, 8-bromo-cAMP, EGF, and phorbol 12-myristate 13-acetate (PMA). Moreover, although the high level of HGF production in MRC-5 cells was enhanced by PMA and less markedly by IL-1beta, HGF production in MRC-5 cells treated with PMA plus IL-1beta was less than that in the cells treated with PMA alone. In the presence of interferon (IFN)-gamma, however, cholera toxin- and 8-bromo-cAMP-induced HGF production was not inhibited by IL-1beta. Pretreatment of cells with IL-1beta suppressed the phosphorylation of cAMP-responsive element-binding protein induced by cholera toxin but not that induced by 8-bromo-cAMP. Taken together, our results indicate that IL-1 inhibited HGF production stimulated by various inducers, including protein kinase A-activating agents, and that IFN-gamma overcame this inhibition of induction of HGF production.     

Production of intracellular IL-1alpha, IL-1beta, and IL-1Ra isoforms by activated human dermal and synovial fibroblasts: phenotypic differences between human dermal and synovial fibroblasts

We compared the production of IL-1alpha, IL-1beta, and of IL-1Ra isoforms by cultured human dermal (HDF) and synovial fibroblasts (HSF) in response to IL-1alpha, TNF-alpha, or direct T cell membrane contact. IL-1Ra was constitutively present in the cell lysates of cultured HDF and its synthesis increased in stimulated cells, whereas IL-1Ra was present in low amounts in the supernatants. Secreted IL-1Ra (sIL-1Ra) and intracellular IL-1Ra type 1 (icIL-1Ra1) mRNA levels followed the same pattern. In stimulated HDF, IL-1alpha and IL-1beta were increased intracellularly but remained undetectable in the supernatants. In HSF, IL-1Ra levels increased in both cell lysates and supernatants upon stimulation. IL-1beta was only present in HSF cell lysates after stimulation, whereas IL-1alpha was undetectable. Both sIL-1Ra and icIL-1Ra1 mRNAs were detected in stimulated HSF. icIL-1Ra1 was the predominant intracellular isoform in both cell types. In conclusion, stimulated HDF produce high amounts of intracellular IL-1Ra, IL-1alpha, and IL-1beta. In contrast, HSF synthesized both intracellular and secreted IL-1Ra, whereas IL-1beta was present only in cell lysates. The presence of high amounts of icIL-1Ra1 and intracellular IL-1alpha in HDF suggests that these cytokines may carry out important function inside cells.