Hepatocyte growth factor (HGF) regulates blood-testis barrier (BTB) in adult rats

We have studied the effects of HGF on BTB dynamics in adult rats. We demonstrate that, at stages VII-VIII of the epithelium wave when germ cells traverse the BTB, HGF reduces the levels of occludin and influences its distribution pattern and assembling. Moreover, we report that, at stages VII-VIII, HGF significantly increases the amount of active TGF-β and the amount of uPA present in the tubules. For the first time we report that, in the same stages, HGF reduces the amount of actin present in the BTB region, in which occludin levels are highest, and modifies the morphology of the actin cytoskeleton network. At the level of maximal intensity of occludin fluorescence, we report that HGF also modifies the colocalization of occludin and actin. Lastly, we demonstrate that HGF is maximally expressed at stages VII-VIII, whereas its levels fall in the subsequent stages.

The effect of hepatocyte growth factor on the initial stages of mouse follicle development

Interactions between theca and granulosa cells of the follicle are critical for the coordination of ovarian follicle development. The cell-cell interactions are mediated through the local production and actions of a variety of factors. The current study is designed to investigate the expression of Hgf and its receptor, c-Met, in the mouse ovary during in vivo folliculogenesis. We found that Hgf and c-Met mRNAs were already expressed in 2-day-old ovaries, and that, while c-Met levels remained constant until 22-day-old, Hgf levels slightly but not significantly increased with age. The expression of Hgf mRNA in theca/interstitial cells was higher than in granulosa cells in 22-day-old ovaries. Immunohistochemistry analysis confirmed the expression pattern demonstrated by RT-PCR. We investigated the role of hepatocyte growth factor (HGF) at the beginning of mouse folliculogenesis and its possible interaction with kit ligand (KL). Interestingly, both KL and HGF were able to increase the expression of each other, creating a positive feedback loop. In the presence of HGF, we observed an increase of granulosa cell proliferation and an increase in the number of pre-antral and early antral follicles in ovary organ cultures. We also observed a significant increase in the diameters of follicles in individual follicle cultures. Moreover, HGF stimulated the expression of the FSH receptors, both in the whole ovary and in isolated pre-antral follicle cultures. Based on the data presented, we concluded that HGF exerts multiple levels of control over follicular cell functions, which collectively enable the progression of follicular development.

Diabetic rat testes: morphological and functional alterations

Reproductive dysfunction is a consequence of diabetes, but the underlying mechanisms are poorly understood. This study investigated the histological and molecular alterations in the testes of rats injected with streptozotocin at prepuperal (SPI rats) and adult age (SAI rats) to understand whether diabetes affects testicular tissue with different severity depending on the age in which this pathological condition starts. The testes of diabetic animals showed frequent abnormal histology, and seminiferous epithelium cytoarchitecture appeared altered as well as the occludin distribution pattern. The early occurrence of diabetes increased the percentage of animals with high number of damaged tubules. The interstitial compartment of the testes was clearly hypertrophic in several portions of the organs both in SPI and SAI rats. Interestingly, fully developed Leydig cells were present in all the treated animals although abnormally distributed. Besides the above-described damages, we found a similar decrease in plasma testosterone levels both in SPI and SAI rats. Oxidative stress (OS) is involved in the pathogenesis of various diabetic complications, and in our experimental models we found that manganese superoxide dismutase was reduced in diabetic animals. We conclude that in STZ-induced diabetes, the altered spermatogenesis, more severe in SPI animals, is possibly due to the effect of OS on Leydig cell function which could cause the testosterone decrease responsible for the alterations found in the seminiferous epithelium of diabetic animals.

Hepatocyte growth factor (HGF) modulates Leydig cell extracellular matrix components

Hepatocyte growth factor (HGF) is a pleiotropic factor that plays multiple roles during mammalian development. We previously demonstrated that in the postnatal testes, the HGF receptor, c-met, is expressed by Leydig cells and HGF increases the steroidogenetic activity of the cells. In the present article, we report that HGF modifies the composition of the extracellular matrix of cultured Leydig cells. We show that HGF increases the metabolic activity of isolated Leydig cells; in particular, the factor increases urokinase plasminogen activator and matrix metalloproteinase 2 secretion. We have also shown that the levels of active transforming growth factor beta are increased by HGF. On the contrary, using the Western blotting technique, a strong reduction in the amount of fibronectin present in the culture medium of cells cultured in the presence of HGF has been detected. The presented data demonstrate that HGF modulates several functional activities of Leydig cells, further supporting the hypothesis that this factor has a relevant role in the regulation of mammalian spermatogenesis.

Hepatocyte growth factor modulates Sertoli-Sertoli tight junction dynamics

In mammalian testes Sertoli cells form tight junctions whose function is fundamental for the maintenance of a normal spermatogenesis. Hepatocyte growth factor (HGF) is a cytokine influencing the cellular tight junctions either in normal or in tumor cells. We have previously demonstrated that HGF is expressed in the rat testis and influences many functional activities of somatic and germ cells. We now report that HGF decreases the levels of testicular occludin and influences the position of the molecule in the tight junctions as demonstrated by confocal microscopy analysis. In fact in the presence of the factor occludin was mainly localized in the suprabasal region of the tubules whereas in its absence occludin was prevalently localized in the basal region. Occludin production is known to be regulated by different cytokines including TGFbeta. We have investigated the role of HGF in the regulation of the levels of TGFbeta and we report that HGF significantly increases the amount of the active fraction of the factor without affecting the amount of the total TGFbeta. Urokinase type plasminogen activator (uPA) is closely related with the tight junctions and is one of the molecules able to activate the inactive TGF-beta. We found that HGF significantly increases the amount of uPA present in the testis suggesting that HGF regulates the amount of active TGFbeta via uPA levels. In conclusion we report that in the testis HGF regulates Sertoli-Sertoli tight junctions inducing a reduction and redistribution of occludin possibly modulating the levels of uPA and active TGFbeta.

Direct effects of microgravity on testicular function: analysis of hystological, molecular and physiologic parameters

Spaceflight experiments carried out in microgravity environments have revealed that exposure to altered gravity condition results in alteration of several cellular functions and, consequently, of several apparatuses. There is some evidence in the literature indicating that spaceflight affects the physiology of the testis. The data on effects of spaceflight or simulated microgravity on testicular function, however, sometimes appear contradictory. In the present study we used an in vitro experimental model in order to investigate the direct effects of microgravity on testicular tissue. We generated a microgravity environment using the Rotating Wall Vessel and performed experiments on testicular fragments isolated from pre-pubertal rats. In this model we then analyzed several parameters such as histological integrity, cell proliferation, cell apoptosis, occludin distribution pattern, and hormonal secretions. The emerging picture shows some alterations of testicular tissue physiology. Interestingly, we also demonstrate for the first time that, in organ culture, Leydig cell survival is severely affected by simulated microgravity.

Expression and functional role of hepatocyte growth factor and its receptor (c-met) during fetal mouse testis development

The hepatocyte growth factor (HGF) is a pleiotropic cytokine able to regulate different cellular functions. HGF action is mediated by its receptor, c-met, a glycoprotein with tyrosine kinase activity. We previously demonstrated that c-met is expressed in the newly formed seminiferous cords of the mice embryonic testes and that HGF acts as a morphogenetic factor. In this paper, we report that at 15.5 days post-coitum (dpc) c-met is expressed in the testicular cords, whereas at 18.5 dpc c-met expression is almost exclusively localized in the interstitial tissue of the testis in particular in the fetal Leydig cells. In addition, we demonstrate that HGF gene is expressed during the fetal period of testis development, heavily detectable in the interstitial compartment of 18.5 dpc testes. Interestingly, HGF is not expressed in the Leydig cells that, as above reported, express the HGF receptor. Looking for the functional role of HGF on Leydig cells, we evaluated the amount of testosterone secreted by testes isolated from 18.5 dpc embryos and cultured in the presence of HGF. The results of the in vitro organ culture show that, at this age, HGF increases the amount of testosterone secreted in the culture medium. On the contrary, HGF does not modulate the amount of testosterone secreted by testes isolated from 15.5 dpc embryos. In conclusion, we report that HGF is produced in the interstitial compartment of the developing testis but not by the Leydig cells. Conversely, the HGF receptor c-met is expressed in the Leydig cells and HGF modulates Leydig cell function during the late period of prenatal development.

Hepatocyte growth factor modulates in vitro survival and proliferation of germ cells during postnatal testis development

The hepatocyte growth factor (HGF) is a pleiotropic cytokine that influences mitogenesis, motility and differentiation of many different cell types by its tyrosine kinase receptor c-Met. We previously demonstrated that the c-Met/HGF system is present and functionally active during postnatal testis development. We found also that spermatozoa express c-Met and that HGF has a positive effect on the maintenance of sperm motility. In the present paper, we extend our study on the germ cells at different stages of differentiation during the postnatal development of the testis. We demonstrate that c-met is present in rat spermatogonia, pachytene spermatocytes and round spermatids and that HGF significantly increases spermatogonial proliferation in 8- to 10-day-old pre-pubertal rats. At this age HGF does not affect Sertoli cells and peritubular myoid cells proliferation. In addition, we studied the effect of the factor on germ cell apoptosis and we show that HGF prevents the germ cell apoptotic process. We also studied the effect of HGF on 18- to 20-day-old and 28- to 30-day-old rat testes. At these ages also the factor significantly increases germ cell duplication and decreases the number of apoptotic cells. However, the effect on programmed cell death is higher in the 8- to 10-day-old rats and declines in the older animals. In conclusion, we report that rat germ cells (spermatogonia, pachytene spermatocytes and round spermatids) express c-met and that HGF modulates germ cell proliferating activity and apoptosis in vitro. These data indicate that the c-Met/HGF system is involved in male germ cell homeostasis and, consequently, has a role in male fertility.

HGF and postnatal testis development

Hepatocyte growth factor regulates many cellular functions acting through c-met, its specific receptor with tyrosine kinase activity. We have previously reported that in prepubertal rats HGF is secreted in the seminiferous tubules by purified peritubular myoid cells whereas Sertoli cells do not express HGF mRNA. In the present paper we report that HGF is expressed by the myoid cells during the entire postnatal testicular development studied and secreted in the culture medium. On the contrary, in Sertoli cells HGF starts to be clearly detectable by northern blot at 25 days of age. HGF is expressed and secreted by Sertoli cells isolated from 35-day-old rats and is able to increase the levels of c-met expression of the Sertoli cells. Although the role of HGF during the development of the postnatal testis need further research to be clarified, the data here presented indicate that HGF is one of the growth factors regulating mammalian testicular function.

Embryonic mouse testis development: role of platelet derived growth factor (PDGF-BB)

Platelet-derived growth factors (PDGFs) are paracrine growth factors mediating epithelial-mesenchymal interactions and exerting multiple biological activities which include cell proliferation, motility, and differentiation. As previously demonstrated, PDGFs act during embryonic development and recently, by culturing male genital ridges, we have demonstrated that PDGF-BB is able to support in vitro testicular cord formation. In the present paper, we report that PDGF-BB is present during embryonic testis development and, in organ culture, induces cord formation although with reduced diameters compared with the cords formed in the genital ridges cultured in the presence of HGF. Moreover we have analyzed the roles exerted by this growth factor during the morphogenesis of the testis. We demonstrate by immunohistochemical experiments that PDGF-BB and its receptors are synthesized by the male UGRs isolated from 11.5 and 13.5 dpc embryos and by Western blot that the factor is secreted in a biologically active form by testicular cells isolated from 13.5 dpc embryos. The biological roles of the factor have also been studied and we demonstrate that PDGF-BB acts as a migratory factor for male mesonephric cells whose migration is a male specific event necessary for a normal testicular morphogenesis. In addition we demonstrate that during testicular development, PDGF-BB induces testicular cell proliferation being in this way responsible for the increase in size of the testis. Finally we demonstrate that PDGF-BB is able to reorganize dissociated testicular cells inducing the formation of large cellular aggregates. However the structures formed in vitro under PDGF-BB stimulation never had a cord-like morphology similar to the cord-like structures formed in the presence of HGF (Ricci et al., 2002, Mech Dev 118:19-28), suggesting that this factor does not act as a morphogenetic factor during testicular development. All together the data presented in this paper demonstrate that PDGF-BB and its receptors (alpha- and beta-subunits) are present during the crucial ages of embryonic mouse testis morphogenesis and indicate the multiple roles exerted by this factor during the development of the male gonad.

Microgravity effect on testicular functions

In mammals spaceflight influences spermatogenesis since spermatogonial germ cell proliferation, compared to synchronous controls, is lightly decreased in irradiated or flown rats. Moreover, changes of the plasmatic testosterone production was described either in flight rats, or in rats maintained in simulated microgravity conditions. The hormonal levels of the astronauts change as it has been previously described, including hormones involved in the regulation of spermatogenesis such as testosterone and luteinizing hormone (LH). In microgravity conditions, human testosterone levels decreased whereas circulating LH levels increased. To study the effect of simulated microgravity on mammalian spermatogenesis we have utilized the Rotary Cell Culture System (RCCS) and we have cultured testicular fragments isolated from prepuberal rats in a chemically defined medium for three days under microgravity conditions. As control we have cultured the same amount of fragments at unit gravity. The morphology of the samples has been studied and the number of proliferating cells has been counted in control samples and in samples maintained in RCCS. The results indicate that the number of duplicating cells in the tubules was significantly increased in the microgravity-cultured fragments. The amount of testosterone secreted in the culture medium has been also evaluated and in RCCS samples the amount of the hormone was higher respect to the control samples.

Functional role of hepatocyte growth factor receptor during sperm maturation

Mammalian spermatozoa acquire motility and fertilizing capacity during their transit through the epididymis. Hepatocyte growth factor (HGF) is a pleiotropic cytokine with potent motogenic capacities that has been identified in different organs, including the mammalian male genital tract. In mice, HGF is present in the testis and, in large amounts, in the distal part of the epididymis. In prepuberal rats, we have demonstrated that HGF is synthesized by the peritubular myoid cells and in men, HGF is present in significant quantities in seminal plasma. It has been suggested that in mice, HGF has a role in initiating sperm motility, whereas in men, no significant correlations between HGF concentration and sperm motility have been found. In the present paper we report that in rats, HGF receptor, c-met, is expressed in testicular and epididymal spermatozoa. Through immunocytochemistry, we have found that c-met is exclusively localized on the head in testicular sperm. A different localization of c-met has been found in sperm isolated from caput and cauda epididymidis. Cells isolated from epididymal caput show a c-met localization exclusively restricted to the head in most cells. In a minority of caput epididymis spermatozoa the receptor is localized both in the cell head and along the flagellum. Spermatozoa isolated from the epididymal cauda were quite homogeneous, showing the receptor localized along the entire cell surface. We also report that HGF is synthesized and secreted by the rat epididymis as indicated by the scatter effect of epididymal cell homogenate and culture medium on MDCK cells. To clarify whether HGF is involved in the acquisition of sperm motility in the epididymis, its maintenance, or both, spermatozoa isolated from caput epididymidis have been cultured in medium alone or supplemented with HGF. The results obtained indicated that HGF has a positive effect on the maintenance of sperm motility which, in the absence of HGF, significantly decreases during the first hour of culture, whereas it is maintained for at least 3 hours when HGF is present in the culture medium. We also report that HGF does not influence spermatozoa viability as indicated by the cytometrical analysis of propidium iodide-labeled sperm; an equal number of dead cells appeared in control and in HGF-treated preparations. In conclusion, our data strongly support the hypothesis that HGF positively influences sperm motility maintenance during sperm transit through the epididymis, indicating that c-met receptor and its ligand, HGF, have a role in male fertility.

Pleiotropic activity of hepatocyte growth factor during embryonic mouse testis development

The hepatocyte growth factor (HGF) is a pleiotropic cytokine whose action is mediated by c-met, a glycoproteic receptor with tyrosine kinase activity which transduces its multiple biological activities including cell proliferation, motility and differentiation. During embryonic development HGF acts as a morphogenetic factor as previously demonstrated for metanephric and lung development. Recently, culturing male genital ridges, we demonstrated that HGF is able to support in vitro testicular cord formation. In the present paper we report the expression pattern of the HGF gene during embryonic testis development and the multiple roles exerted by this factor during the morphogenesis of this organ. Northern blot analysis reveals a positive signal in urogenital ridges isolated from 11.5 days post coitum (dpc) embryos and in testes isolated from 13.5 and 15.5 dpc male embryos. On the contrary HGF mRNA is undetectable in ovaries isolated from 13.5 and 15.5 dpc embryos. Moreover, we demonstrate that HGF is synthesized and secreted by the male gonad and is biologically active. These data indicate a male specific biological function of HGF during embryonic gonadal development. This hypothesis is supported by the in vitro demonstration that HGF acts as a migratory factor for male mesonephric cells which is a male specific event. In addition we demonstrate that during testicular development, HGF acts as a morphogenetic factor able to reorganize dissociated testicular cells which, under HGF stimulation, form a tridimensional network of cord-like structures. Finally, we demonstrate that HGF induces testicular cell proliferation in this way being responsible for the size increase of the testis. All together the data presented in this paper demonstrate that HGF is expressed during the embryonic development of the testis and clarify the multiple roles exerted by this factor during the morphogenesis of the male gonad.

Expression and functional role of hepatocyte growth factor receptor (C-MET) during postnatal rat testis development

The met protooncogene encodes the hepatocyte growth factor receptor (HGFR, c-met). C-met, a tyrosine kinase receptor protein, is widely expressed in different cell types including the male reproductive tract. As we recently demonstrated, both c-met messenger RNA and protein are expressed in prebuberal rat testis. The aim of this work was to detect the expression of c-met during postnatal testis development and to study its functional role. Our findings show that in total rat testis c-met is expressed during postnatal life until the sexual maturation of the animals. To evaluate the receptor expression in the different cell types in the testis, homogeneous cell populations of Sertoli and peritubular myoid cells were isolated from the seminiferous tubules of 10- and 35-day-old animals. c-met gene is expressed in myoid cells at the ages considered and its expression decreases with increasing age. By contrast, in Sertoli cells c-met expression is first detectable at 25 days of life and its expression increases with the increasing age being well evident at 35 days of age. C-met protein was detected by immunocytochemistry and its expression correlates with gene expression. The receptor is functionally active because HGF administration induces morphological changes in myoid cells and in c-met-expressing Sertoli cells. As a consequence of HGF addition, Sertoli cells cultured on reconstituted basement membrane reorganize into cord-like structures that resemble testicular seminiferous cords. The data here reported demonstrate for the first time that in Sertoli cells c-met expression is developmentally regulated being present and functionally active in postpuberal Sertoli cells. Given that c-met expression persists in myoid cells during postnatal testis development and that in Sertoli cells its expression correlates over time with germ cell differentiation and lumen formation, we conclude that the c-met/HGF system is involved in testis development and function.

Retinoid modulation of plasminogen activator production in rat Sertoli cells

Tissue type (t) and urokinase type (u) plasminogen activators (PAs) have been shown to be secreted by Sertoli cells in the seminiferous tubules in a cyclic fashion and to be dependent upon FSH stimulation or upon the presence of adjacent spermatogenic cells. In the present study we have analyzed the production of PAs by retinoid-treated rat Sertoli cells. In addition, because retinoids modulate the response of Sertoli cells to FSH either potentiating or antagonizing its action, we have investigated a possible modulation of FSH-stimulated PA production. Under basal conditions, Sertoli cells, isolated from prepubertal rats, secrete predominantly uPA. A significant dose-dependent inhibition of uPA activity was observed after treatment with retinol, while no significant effect was detected upon tPA secretion. When Sertoli cells were cultured in the presence of 0.25 microM retinol, a significant inhibition of uPA activity was evident after 16 h of treatment and reached approximately 80% after 48 h of treatment. The analysis of the mRNA levels revealed that retinol induces an inhibition of the steady-state levels of uPA mRNA without affecting those of tPA. Moreover, retinol affected uPA mRNA levels by increasing mRNA turnover. The effect of retinoids on Sertoli cells isolated from older animals was less evident, possibly due to the reduced production of uPA with the increase of age of the donor animals. Our results on the effect of retinoids upon Sertoli cell uPA production reinforce the importance of retinoids in the control of postnatal testis development.

Prevention of spontaneous autoimmune diabetes in NOD mice by transferring in vitro antigen-pulsed syngeneic dendritic cells

To evaluate the effect of antigen-pulsed dendritic cell (DC) transfer on the development of diabetes, 5-week-old female NOD mice received a single iv injection of splenic syngeneic DC from euglycemic NOD mice pulsed in vitro with human y globulin (HGG). Eleven of 12 mice were protected from the development of diabetes up to the age of 25 weeks, and the insulitis score was significantly reduced. In contrast, NOD mice receiving unpulsed splenic DCs showed histological signs of insulitis and course of type 1 diabetes similar to untreated NOD mice. Treatment with HGG-pulsed DC was associated with profound modifications of cytokine secretory capacities within the islets. Thus, supernatants of islets from these mice contained increased levels of interleukin (IL)-4, IL-10, and, to a lesser extent, interferon-gamma and diminished levels of tumor necrosis factor-a compared with controls. Because exogenous IL-4 and IL-10 exert antidiabetogenic effect in NOD mice and early blockade of endogenous tumor necrosis factor-alpha prevents NOD mouse diabetes, these phenomena may be causally related to the antidiabetogenic effect of HGG-pulsed DC treatment.

Multiple low-dose and single high-dose treatments with streptozotocin do not generate nitric oxide

Streptozotocin (STZ) is a widely used diabetogenic agent that damages pancreatic islet beta cells by activating immune mechanisms, when given in multiple low doses, and by alkylating DNA, when given at a single high dose. Actually, STZ contains a nitroso moiety. Incubation of rat islets with this compound has been found to generate nitrite; moreover, photoinduced NO production from STZ has been demonstrated. These reports have suggested that direct NO generation may be a mechanism for STZ toxicity in diabetogenesis. Several other studies have denied such a mechanism of action. This study has shown that (1) the multiple low-dose (MLDS) treatment does not stimulate NO production at the islet level; in fact, nitrite + nitrate levels and aconitase activity (also in the presence of an NO-synthase inhibitor, namely NAME) remain unmodified; RT-PCR analysis demonstrates that this treatment does not stimulate iNOS activity; (2) the high-dose (HDS) treatment does not stimulate NO production; in fact nitrite + nitrate levels remain unmodified and iNOS mRNA levels are not altered, although aconitase activity is significantly decreased. Moreover, we have confirmed that the MLDS treatment is able to decrease SOD activity by day 11 and that STZ, given in a single high dose, transiently increases superoxide dismutase (SOD) values (24 h from the administration), then dramatically lowers SOD levels. On the basis of our results, we conclude that STZ, "in vivo" is unable to generate NO, both as a MLDS or HDS treatment, thus excluding that NO exerts a role in streptozotocin-dependent diabetes mellitus.

Hepatocyte growth factor (HGF) receptor expression and role of HGF during embryonic mouse testis development

The hepatocyte growth factor (HGF) receptor, c-met, transduces the HGF multiple biological activities. During embryonic development the system HGF/c-met regulates the morphogenesis of different organs and tissues. In this study we examined c-met gene expression during mouse testis development and, by means of Northern blot and in situ hybridization, we report the receptor expression pattern. C-met expression is not detectable in male genital ridges isolated from embryos at 11.5 days postcoitum (dpc). In testes isolated from 12.5 and 13.5 dpc, c-met expression is detectable and essentially localized in the developing cords. Male genital ducts do not express c-met at the reported ages, whereas female ducts appear c-met positive. Moreover, we report that HGF is able to induce testicular morphogenesis in vitro. Male genital ridges isolated from embryos at 11.5 dpc are morphologically nonorganized. Culturing 11.5 dpc urogenital ridges in the presence of HGF we obtained testis organization and testicular cord formation. Our data demonstrate that c-met is expressed during the beginning period of testis differentiation and that HGF is able to support testicular differentiation in vitro. All these data indicate that this growth factor, besides its role as mitogenic factor, plays a fundamental role during testicular cord formation probably inducing cell migration and/or cell differentiation.

Hepatocyte growth factor and c-MET are expressed in rat prepuberal testis

The hepatocyte growth factor (HGF) receptor (c-MET) is present in different mammalian tissues and transduces multiple biological effects. The HGF is known to regulate many fundamental cellular functions, such as cell growth, movement and differentiation, and is involved in embryonal morphogenesis. We have studied HGF and c-MET expression in prepuberal rat testis. c-MET gene expression was found in total testis and in homogeneous cell populations, as demonstrated by Northern blotting. In the seminiferous tubules, c-MET gene was only expressed in the myoid cells. In these cells, c-MET was detectable and constantly expressed for at least six days of culture. The interstitial tissue was also c-MET positive. The protein encoded by the MET proto-oncogene was detected in myoid cells, and HGF administration to these cells induced morphological changes in the cells. HGF expression was not detected by Northern blotting using RNA extracted from total testis. By contrast, when homogenous cell populations were used, HGF expression was detectable and exclusively localized in myoid cells. Myoid cell-conditioned medium was able to induce scattering of canine kidney epithelial (MDCK) cells, and the scatter effect of a 3-days conditioned medium was evident even after 7-fold dilution of the medium. Our findings demonstrate that HGF and its receptor are present in rat prepuberal testis. The coexpression of factor and receptor in the myoid cells suggests a new role for HGF as autocrine regulator of myoid cell function and, possibly, as regulator of mammalian testicular function.

Vitamin A modulation of basement membrane production by purified testicular myoid cells

Purified myoid cells, isolated from prepubertal rat testes, cultured in a chemically defined medium for up to 1 week do not change their metabolic activities, evaluated as protein synthesis and secretion, during the culture time. We report that fibronectin, collagen IV, and laminin are synthesized and secreted by myoid cells as demonstrated by immunocytochemical and biochemical methods. The deposition of all three proteins was spotty, with different regional localizations. The effect of vitamin A on the synthesis and the secretion of the basement membrane components was also evaluated. Retinol supplementation induces a higher synthesis of fibronectin and laminin, whereas it does not change collagen IV synthesis and secretion. The secretion of the other two molecules is differentially regulated by retinol; in fact fibronectin secretion is increased, whereas laminin secretion is reduced. Similar results were obtained utilizing retinoic acid. The data we report in this paper show, for the first time, that purified testicular myoid cells synthesize and secrete fibronectin, collagen IV, and laminin and that synthesis and secretion of these components of the basement membrane are regulated by retinol. These findings reveal a new effect of vitamin A in the regulation of mammalian spermatogenesis.

Characterization of different cell populations isolated from rat testis peritubular cells

Peritubular cells, a mixed population of myoid and non-myoid cells obtained by enzymatic treatments of rat seminiferous tubules, are currently utilized as a myoid cell population. We have morphologically and biochemically compared peritubular cells and purified myoid cells isolated from prepubertal rats. The two cell populations appear morphologically similar when cultured in the presence of serum: both appear to be composed of elongated cells when observed by phase-contrast microscopy. However, the two populations differ in the percentage of alkaline phosphatase positive cell since only a minority of the cells present in the peritubular cell population are positive for alkaline phosphatase expression. Secretory activity of myoid cells is higher when compared to the peritubular cell secretion. To the contrary, fibronectin is highly synthesized and secreted by the peritubular cells, suggesting that the non-myoid cells synthesize fibronectin at a high level. Myoid cells have also been cultured in a chemically defined medium without any serum addition. In this experimental condition the cells show a polygonal shape, which remains constant during culture time. Secretory activity and fibronectin synthesis and secretion of the cells cultured without serum are lower when compared to the values obtained in the presence of serum at the beginning of the culture. Moreover, the distribution of the cell-associated fibronectin is modified by the culture conditions: spotted on cells cultured in the absence of serum and fibrillar on cells cultured with serum. We therefore conclude that peritubular cells and myoid cells are significantly different cell populations and that serum addition to the culture medium dramatically influences the morphology and the metabolic activities of the myoid cells.

Rat peritubular cell secretory activity: modulation by vitamin A

Protein synthesis and secretion by rat peritubular cells cultured in the presence or in the absence of vitamin A were analyzed after labelling the cells with different amino acids. Vitamin A reduces the amount of proline incorporated into the newly-synthesized proteins secreted by the peritubular cells. By mono- and two-dimensional gel electrophoresis analysis, qualitative differences induced by retinol addition were detected in the proteins secreted by the proline-labelled cells. In particular we demonstrate that the amount of fibronectin secreted by the cells is reduced after retinol addition. Northern blot analysis indicates that fibronectin messenger RNA transcription is also reduced as a consequence of the vitamin addition.

Retinoic acid synthesis in the somatic cells of rat seminiferous tubules

At physiological plasma concentrations, retinoic acid (RA) cannot cross the blood-testis barrier formed by Sertoli and peritubular cells, and it is thought to be mainly synthesized in situ through the oxidation of retinol. We have thus examined the in vitro RA biosynthetic capacity of cultured Sertoli and peritubular cells isolated from the seminiferous tubules of prepubertal rats, using holo-cellular retinol binding protein (CRBP) as a substrate. Although both somatic cell types contain CRBP and retinoic acid nuclear receptors, RA synthesis was only detected with Sertoli cell subcellular fractions. Most of the RA synthesizing activity of these cells is contributed by a microsomal-cytosolic system that shares many functional similarities with a RA biosynthetic pathway originally identified in rat liver. RA synthesis is maximal at a time of postnatal life (20 days) preceding meiotic cell accumulation and remains nearly constant thereafter. The unique ability of Sertoli cell subcellular fractions to support RA formation from holoCRBP, along with the observed age-dependent modulation of this activity, indicate that Sertoli cells represent the main site of intratubular RA production and that they may play a key role in controlling RA-dependent processes within the seminiferous tubule.

Retinoids regulate gonadotropin action in cultured rat Sertoli cells

The effect of retinoids on cultured rat Sertoli cells was studied by evaluation of cAMP and estradiol production after gonadotropin stimulation in the presence or absence of the retinoid. Sertoli cells cultured in the presence of FSH produce a high amount of cAMP and increase their aromatase activity. The addition of retinol alone has no effect on cAMP and estradiol production; however, the presence of retinol in the culture medium exerts an inhibitory effect on Sertoli cell response to FSH stimulation. In particular, FSH-induced cAMP production of rat Sertoli cells was significantly reduced (50-60% decrease) both by retinol and by retinoic acid. This effect was observable during the first ten days of culture and was also evident when Sertoli cells were cultured in the presence of retinol and methylisobutylxanthine, an inhibitor of phosphodiesterase activity. Cholera toxin-stimulated cAMP levels were reduced by retinol, whereas forskolin-induced elevation of cAMP levels was not affected by vitamin treatment. The inhibitory effect of retinoids on FSH-stimulated aromatase activity of Sertoli cells, which is cAMP mediated, was also evident. In conclusion, the present study demonstrates that retinoids modulate FSH action on cultured rat Sertoli cells and decrease cAMP production.

Cellular retinoic-acid-binding-protein and retinol-binding-protein mRNA expression in the cells of the rat seminiferous tubules and their regulation by retinoids

The levels of the mRNA corresponding to the intracellular binding proteins for retinoic acid and retinol (CRABP1 and CRBP1, respectively) were studied in primary cultures of somatic and germ cells of the rat seminiferous tubules. We show that the CRABP1 mRNA is expressed in Sertoli and germ cells and a single molecular species of mRNA is detected. CRBP1 mRNA is detected in Sertoli and peritubular cells. The regulation of the expression of both genes by retinoids was studied in Sertoli cells. CRABP1 mRNA levels are not affected by either retinoic acid or retinol, whereas both compounds positively regulate CRBP1 mRNA synthesis in a dose-dependent manner. A fivefold increase in CRBP1 mRNA levels was observed 32-48 h after addition of either agent. These results demonstrate that in Sertoli cells the expression of CRABP1 is not affected by retinoids, similar to the situation observed in vivo and in other in-vitro cultures. CRBP1-gene expression is, instead, induced and the variations in CRBP1-mRNA levels may regulate the intracellular concentrations of retinoids, as a response to changes in the vitamin-A nutritional status.

Levels of binding proteins for retinoids in cultured Sertoli cells: effect of medium composition

The levels of cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein (CRABP) have been measured in Sertoli cells maintained under different cultural conditions. Sertoli cells were isolated from prepubertal rats and cultured in a chemically defined medium without or with follicle-stimulating hormone (FSH), insulin, retinol or testosterone added individually or in combinations. The additions were made at the beginning of the culture or 24 h before the cells were subjected to determinations of CRBP and CRABP by radioimmunoassay. No differences were observed either after 1 or 4 days of treatment. The results obtained indicated that the levels of the two retinoid-binding proteins were unchanged in Sertoli cells in response to hormone and/or retinol administration. To rule out the possibility that the Sertoli cells used in our study were unresponsive to the hormones, lactate production by the cells cultured in the presence of FSH or insulin was measured. The amount of lactate produced under hormonal stimulation was significantly higher than the amount produced in absence of the hormones, thus indicating the ability of our Sertoli cells to respond to the hormonal stimulation.

Detection of cellular retinol-binding protein messenger RNA in the somatic cells of the rat seminiferous tubules

A cDNA clone coding for Cellular Retinol-Binding Protein (CRBP) was used as a probe to study the expression of the gene in the somatic cells of the seminiferous tubules (Sertoli and peritubular cells). In this paper we demonstrate that these cells are actively involved in the synthesis of the specific mRNA. In Sertoli cells the gene is modulated by the hormones effective in spermatogenesis, such as FSH and testosterone. Moreover, peritubular cells revealed an approximately two times higher concentration of CRBP steady-state mRNA levels when compared with Sertoli cells.

Distribution and levels of cellular retinol- and cellular retinoic acid-binding protein in various types of rat testis cells

The distribution and levels of cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein (CRABP) were measured in rat testicular peritubular and Sertoli cells and in isolated rat pachytene spermatocytes and spermatids. Two Sertoli cell preparations, one containing some germ cells and another that had been osmotically shocked to destroy germ cells, were examined. CRBP and CRABP levels were measured by specific and sensitive radioimmunoassays. Testicular peritubular cell cytosol preparations were found to contain high levels of CRBP (1.48 +/- 0.87 microgram CRBP/mg protein) but CRABP could not be detected. The mean CRBP level in Sertoli cell preparations that contained some germ cells was 0.93 +/- 0.24 microgram CRBP/mg protein; this value was similar to the level of 1.11 +/- 0.20 microgram CRBP/mg protein measured for Sertoli cells free of germ cells. The level of CRABP found in Sertoli cell preparations containing germ cells (0.81 +/- 0.32 microgram CRABP/mg protein) was approximately five times greater than was observed in Sertoli cells free of germ cells (0.16 +/- 0.03 microgram CRABP/mg protein). CRBP and CRABP levels in cultured Sertoli cells were not affected by time in culture for up to five days of culture. Pachytene spermatocytes and spermatids were very enriched in CRABP (0.72 +/- 0.26 microgram CRABP/mg protein for spermatocytes and 0.65 +/- 0.21 microgram CRABP/ml protein for spermatids). A search for a high molecular weight retinol-binding protein did not demonstrate the existence of such a protein in Sertoli cell-conditioned medium. In summary, these studies provide quantitative information about the distribution of the cellular retinoid-binding proteins in the cell types that compose the rat testis.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-, phospholipid-dependent protein kinase activity of cultured rat Sertoli cells and its modifications by vitamin A

The activity of the calcium-, phospholipid-dependent protein kinase (PKc) was partially characterized in Sertoli cell cultures prepared from 20-day-old rats. The calcium dependency, the requirements for phosphatidylserine and diolein, as well as the Km for ATP and for the tumor promoter TPA, were determined in total cell extracts. The specific activity of PKc was almost 3-fold higher in the soluble than in the particulate fraction of Sertoli cells. Treatment of cultured Sertoli cells with retinol inhibited, within 1 h of treatment, both the soluble and the particulate fraction-associated PKc activity, with an IC50 of 0.1 microM. Partial inhibition of PKc activity was obtained treating Sertoli cell cultures with FSH, while testosterone was ineffective. However, both FSH and testosterone potentiated the inhibitory effect of retinol. Less differentiated Sertoli cells, obtained from 8-day-old rats, displayed higher PKc activity and a pattern of subcellular distribution of the enzyme opposite to that of Sertoli cells obtained from 20-day-old rats. These data suggest that the actual PKc activity of rat Sertoli cells be negatively regulated by retinol and, spontaneously, during the progression of Sertoli cell differentiation.

Vitamin A modifies the glycopeptide composition of cultured Sertoli cells

Sertoli cells obtained from prepubertal rat testes were cultured in the presence or absence of retinol. Incorporation of monosaccharides and glycopeptide composition of the cells were studied under two experimental conditions. The results indicate that retinol increases the amount of mannose and glucosamine incorporated into cellular glycoconjugates. The labeled glycopeptides obtained from control and retinol-treated cells were separated by size and lectin affinity. Gel filtration analysis showed no size differences between the glycopeptides obtained from control and vitamin A-treated cells. Affinity chromatography on Concanavalin A and Wheat Germ Agglutinin of 3H-mannose-labeled glycopeptides showed that Sertoli cells cultured in the presence of retinol contain a higher percentage of high mannose-type glycopeptides compared with control cells. The effect of retinol on Sertoli cell glycopeptide composition is partially reversed by the administration of FSH.

Sertoli cell membrane polypeptide composition is modulated by germ cells

The polypeptide composition of Sertoli cell enriched cultures (SCEC) and Sertoli cell only cultures (SCOC) obtained after germ cell removal was investigated. Cells were labelled with [35S]methionine and analyzed by one and/or two-dimensional gel electrophoresis. The one-dimensional electrophoretic analysis of SCEC and SCOC particulate fraction did not show any appreciable difference between the two profiles. The more detailed two-dimensional electrophoretic analysis showed the appearance in SCOC of three polypeptides undetectable in SCEC. The molecular weight of these molecules ranged between 44 and 48 kDa. The effect of FSH on the Sertoli cell membrane composition was also investigated. No qualitative differences were detected, although the hormone increased many molecular species including the polypeptides appearing in SCOC. On the basis of these results, the hypothesis that germ cells influence Sertoli cell metabolic parameters is discussed.

Secretion of androgen binding protein by Sertoli cells is influenced by contact with germ cells

Sertoli cells were cultured alone or with germ cells to evaluate the effect of the association with germ cells on the secretory activity of Sertoli cells. Secretion of androgen-binding protein, which is specifically secreted by Sertoli cells, was measured under several experimental conditions. The following experimental models were utilized: 1) cultures of explants of seminiferous epithelium from prepubertal animals in which germ cells adherent to Sertoli cells are present (Sertoli cell enriched cultures); 2) monolayers formed only by Sertoli cells, obtained by removing germ cells from Sertoli cell enriched cultures, and 3) cocultures of Sertoli cell only cultures and germ cell populations at defined stages of differentiation. The results obtained indicated that FSH-induced ABP secretion was greatly reduced in Sertoli cell only cultures as compared to enriched Sertoli cell cultures, and that this difference was stable throughout the first eight days of culture. In addition, cocultures of Sertoli cell only cultures with germ cells induced an increase of ABP when cocultured germ cells were at differentiation stages, such as pachytene spermatocytes, which are able to recognize and firmly adhere to the Sertoli cell monolayers. Cocultures with round spermatids, which do not adhere to Sertoli cells, did not increase the amount of FSH-induced ABP production. The addition of nongerminal cells such as lymphocytes and fibroblasts were also not effective in stimulating ABP secretion. Surface interaction between Sertoli cells and cocultured germ cells seemed to be necessary for this FSH-induced ABP production.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological and biochemical effects of lonidamine on cultured Sertoli cells

Lonidamine, an antispermatogenic compound derivative of indazole-3-carboxylic acid, administered to rat Sertoli cells induced morphological changes of the cells which rapidly shrinked forming cytoplasmic projections. Some biochemical parameters of Sertoli cells measured after drug administration were their aromatizing ability, protein synthesis, and ribonucleic acid synthesis. The amount of estradiol produced by treated cells was significantly lower than the amount produced by control cells, whereas protein and ribonucleic acid synthesis were not affected by the drug. Our results demonstrate the change of a specific metabolic parameter of Sertoli cells induced by this antispermatogenic compound.

Evidence of protein secretion by cultured pachytene spermatocytes

Pachytene spermatocytes isolated from immature rat testis were cultured for 6 h in the presence of [35S]methionine and the macromolecules present in the culture medium were analyzed by one-dimensional and two-dimensional gel electrophoresis. The electrophoretic profiles obtained showed a limited number of polypeptides, some of them consisting of families of spots with the same molecular weight but a different isoelectric point. The reproducibility of the results and the unaltered metabolic activity of the cells during culture time, indicate that the macromolecules present in the medium do not represent degradative products of the cells. Part of the detected macromolecules are considered secreted proteins since the addition of monensin to the cells induces their disappearance from the culture medium.

Changes of Sertoli cell glycoproteins induced by removal of the associated germ cells

Sertoli cell glycoproteins were studied in culture where these cells were in contact with germ cells (Sertoli cell enriched cultures, SCEC) and in pure Sertoli cell cultures. Sertoli cell only cultures (SCOC) were prepared by a short treatment of SCEC with hypotonic solution or by culturing seminiferous epithelium fragments from prenatally irradiated rats. After metabolic labeling with [3H]fucose. [14C]N-acetylglucosamine or [3H]leucine, SCEC and SCOC particulate fractions (105 000 g pellet) were analyzed by one-dimensional slab gel electrophoresis and fluorography. The comparison of the electrophoretic patterns obtained, demonstrated that a glycoprotein of MW 48 000, undetectable in SCEC, was present in SCOC after labelling with both sugar precursors. The MW 48 000 glycoprotein was also present in the electrophoretic profile of particulate fraction from [3H]fucos-labelled Sertoli cell cultures from prenatally irradiated rat. Such difference was not observed after labelling with [3H]leucine; in this experimental condition a MW 48 000 band was present in the electrophoretic profile of polypeptides from SCEC as well from SCOC. The synthesis of this glycoprotein represented a specific and stable cell response, since it occurred only a few hours after germ cell removal, and it was still detectable 3 days later. FSH stimulation did not influence the synthesis of the MW 48 000 glycoprotein, whereas it increased the synthesis of high MW glycoproteins. The hypothesis is discussed that the appearance of a new glycoprotein when Sertoli cells have lost their contact with germ cells could represent a product of glycosylation of preexisting molecules and their possible location in the Sertoli cell membrane. The results presented here provide additional evidence that Sertoli cell functions may be dependent on the association with the germ cell.

Retinol increases synthesis and secretion of Sertoli cell mannose-containing glycoproteins

Sertoli cell isolated from prepuberal rats were cultured in a chemically defined medium in the presence or in the absence or retinol. In the two experimental conditions the incorporation of 3H-mannose into cellular glycoproteins was measured. The results obtained demonstrated a 3 fold increase of mannose incorporation into cellular glycoproteins after retinol addition without any qualitative variation of their electrophoretic profile. Sertoli cell secretory activity increased of approximately 50% after retinol administration; the electrophoretic analysis showed that two of the secretory products were selectively enhanced by the vitamin addition.

Sertoli cells of adult rats in vitro. III. Purification of androgen-binding protein from the culture medium

A method giving a high yield for the isolation and purification of the androgen-binding protein (ABP) from the nutritional medium of cultured cells from adult rats is described.

Characterization and Partial Purification of Heterodisperse Polysomal RNAs in Normal and Neoplastic Cells

The size distribution of cytoplasmic messenger RNAs (m-RNA) has been studied in rat liver and in monodifferentiated cells (mouse reticulocytes and myelomas). It has been found that the RNA which exhibits a « rapid turnover » and a polydisperse profile of radioactivity is refractory to phenol extraction. This property has been exploited to selectively isolate m–RNA from the phenol residue by means of an extraction at an alkaline pH. The sucrose density gradient profiles of m–RNA isolated from monodifferentiated cells show monodisperse peaks having the sedimentation coefficients expected on the basis of the molecular weights of monocistronic messages for α and β chains of hemoglobin (reticulocytes) and L and H chains of immunoglobulin (myelomas). The sedimentation profile of cytoplasmic m–RNA associated with rat liver polysomes shows a much broader distribution, with sedimentation coefficients ranging from 8 S to 28 S.