Zebrafish embryo extracts enhance 5-FU anti-cancer effects upon breast cancer cells.

OBJECTIVE: The inhibition of the metastatic capability of cancer cells is a pivotal aim of current anticancer strategies. We investigated herein the anti-migrating and anti-invasive properties of Zebrafish embryo extracts (SL) - an integrative formula comprising morphogenetic factors extracted from zebrafish embryos - alone or in association with 5-Fluoro-Uracil (5-FU), when added to metastatic breast cancer cells (MDA-MB-231) and in normal epithelial breast cells (MCF10A) committed toward an inflammatory phenotype upon TGF-ß1 stimulation. MATERIALS AND METHODS: Invasiveness, migrating capability, cytoskeleton architecture and related molecular factors involved in the epithelial-mesenchymal transition were studied after treatment with 5-FU, with and without SL. RESULTS: Remarkably, in both circumstances, embryo extracts amplify the migratory inhibition triggered by the anticancer drug 5-Fu. The fact that such an effect is noticed in normal as well as in cancerous cells suggests that the critical target of embryo extracts is specifically represented by the migrating/invasive phenotype. However, while 5-FU was unable in antagonizing the invasiveness of cancerous cells, the association with SL can significantly impair the invasive capability of tumor cells. These findings are noticeably associated with the reversion of the EMT phenotype in SL-treated cells, as documented by the contemporary downregulation of TCTP and some EMT-related molecular effectors, like α-SMA and Vimentin. CONCLUSIONS: Embryo fish extracts significantly counteract the migrating and invasive phenotype of cancerous and inflammatory breast cells treated with the chemotherapeutic drug 5-FU. The availability of a compound able to amplify 5-Fu activity while significantly hampering the invasive phenotype of breast cancer should provide invaluable benefits, namely if we consider that this compound is substantially deprived of side-effects.

Transient increases in intracellular calcium and reactive oxygen species levels in TCam-2 cells exposed to microgravity.

The effects of microgravity on functions of the human body are well described, including alterations in the male and female reproductive systems. In the present study, TCam-2 cells, which are considered a good model of mitotically active male germ cells, were used to investigate intracellular signalling and cell metabolism during exposure to simulated microgravity, a condition that affects cell shape and cytoskeletal architecture. After a 24 hour exposure to simulated microgravity, TCam-2 cells showed 1) a decreased proliferation rate and a delay in cell cycle progression, 2) increased anaerobic metabolism accompanied by increased levels of intracellular Ca2+, reactive oxygen species and superoxide anion and modifications in mitochondrial morphology. Interestingly, all these events were transient and were no longer evident after 48 hours of exposure. The presence of antioxidants prevented not only the effects described above but also the modifications in cytoskeletal architecture and the activation of the autophagy process induced by simulated microgravity. In conclusion, in the TCam-2 cell model, simulated microgravity activated the oxidative machinery, triggering transient macroscopic cell events, such as a reduction in the proliferation rate, changes in cytoskeleton-driven shape and autophagy activation.

Stearoyl-CoA-desaturase 1 regulates lung cancer stemness via stabilization and nuclear localization of YAP/TAZ.

This corrects the article DOI: 10.1038/onc.2017.75.

Stearoyl-CoA-desaturase 1 regulates lung cancer stemness via stabilization and nuclear localization of YAP/TAZ.

Recent evidences suggest that stearoyl-CoA-desaturase 1 (SCD1), the enzyme involved in monounsaturated fatty acids synthesis, has a role in several cancers. We previously demonstrated that SCD1 is important in lung cancer stem cells survival and propagation. In this article, we first show, using primary cell cultures from human lung adenocarcinoma, that the effectors of the Hippo pathway, Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), are required for the generation of lung cancer three-dimensional cultures and that SCD1 knock down and pharmacological inhibition both decrease expression, nuclear localization and transcriptional activity of YAP and TAZ. Regulation of YAP/TAZ by SCD1 is at least in part dependent upon ß-catenin pathway activity, as YAP/TAZ downregulation induced by SCD1 blockade can be rescued by the addition of exogenous wnt3a ligand. In addition, SCD1 activation of nuclear YAP/TAZ requires inactivation of the ß-catenin destruction complex. In line with the in vitro findings, immunohistochemistry analysis of lung adenocarcinoma samples showed that expression levels of SCD1 co-vary with those of ß-catenin and YAP/TAZ. Mining available gene expression data sets allowed to observe that high co-expression levels of SCD1, ß-catenin, YAP/TAZ and downstream targets have a strong negative prognostic value in lung adenocarcinoma. Finally, bioinformatics analyses directed to identify which gene combinations had synergistic effects on clinical outcome in lung cancer showed that poor survival is associated with high co-expression of SCD1, ß-catenin and the YAP/TAZ downstream target birc5. In summary, our data demonstrate for the first time the involvement of SCD1 in the regulation of the Hippo pathway in lung cancer, and point to fatty acids metabolism as a key regulator of lung cancer stem cells.

Responses of peripheral blood mononuclear cells to moderate exercise and hypoxia.

The purpose of this study was to analyze the physiological features of peripheral blood mononuclear cells (PBMCs) isolated from healthy female trekkers before and after physical activity carried out under both normoxia (low altitude, < 2000 m a.s.l.) and hypobaric hypoxia (high altitude, > 3700 m a.s.l.). The experimental design was to differentiate effects induced by exercise and those related to external environmental conditions. PBMCs were isolated from seven female subjects before and after each training period. The PBMCs were phenotypically and functionally characterized using fluorimetric and densitometric analyses, to determine cellular activation, and their intracellular Ca(2+) levels and oxidative status. After a period of normoxic physical exercise, the PBMCs showed an increase in fully activated T lymphocytes (CD3(+) CD69(+) ) and a reduction in intracellular Ca(2+) levels. On the other hand, with physical exercise performed under hypobaric hypoxia, there was a reduction in T lymphocytes and an increase in nonactivated B lymphocytes, accompanied by a reduction in O2 (-) levels in the mitochondria. These outcomes reveal that in women, low- to moderate-intensity aerobic trekking induces CD69 T cell activation and promotes anti-stress effects on the high-altitude-induced impairment of the immune responses and the oxidative balance.

Dystrophic tendon functionality is recovered by muscle-specific expression of insulin-like growth factor in mdx mice.

Duchenne muscular dystrophy (DMD) is a severe genetic disorder of skeletal muscle, characterized by a steady muscle weakness. By using the animal model for DMD, the mdx mice, we have previously demonstrated that biomechanical properties of tendinous tissue are also significantly affected in this muscle pathology. Muscle specific over-expression of insulin like growth factor-1 (mIgf-1) is known to induce a partial recovery in muscle functionality, in particular increasing the muscle absolute force, but not the specific force. To test whether Igf-1 muscle specific over-expression helps the recovery also in tendinous tissue, mechanical and cellular evaluation of mdx and mdx:MLC/mIgf-1 mice tendons has been performed. Mechanical properties were investigated by measuring the viscoelastic response of the tissue, while cell viability was evaluated by molecular assays. An absolute recovery in the mechanical properties of EDL and TA tendons was observed through the measurement of tissue viscoelasticity for several different frequencies of interest. Moreover, when compared with tendons from dystrophic mdx animals, mdx:MLC/mIgf-1 specimens showed an almost complete recovery in the number of viable cells for both extensor digitorum longus (EDL) and tibialis anterior (TA) tendons. Of note, the partial recovery in muscle functionality and the full recovery in tendons response, suggests that mIgf-1 muscle specific over-expression exerts its effect on tendons either indirectly, improving the tendon viability and its functional properties as a consequence of the reduction of the hostile muscle dystrophic environment, or acting directly on the tendon tissue, as a paracrine trophic factor.

Glial cell line-derived neurotrophic factor promotes invasive behaviour in testicular seminoma cells.

The glial cell line-derived neurotrophic factor (GDNF) has multiple functions that promote cell survival, proliferation and migration in different cell types. The experimental over-expression of GDNF in mouse testis leads to infertility and promotes seminomatous germ cell tumours in older animals, which suggests that deregulation of the GDNF pathway may be implicated in germ cell carcinogenesis. GDNF activates downstream pathways upon binding to its specific co-receptor GDNF family receptor-a 1 (GFRA1). This complex then interacts with Ret and other co-receptors to activate several intracellular signalling cascades. To explore the involvement of the GDNF pathway in the onset and progression of testicular germ cell tumours, we analysed GFRA1 and Ret expression patterns in seminoma samples. We demonstrated, via immunohistochemistry, that GFRA1, but not Ret, is over-expressed in in situ carcinoma (CIS) and in intratubular and invasive seminoma cells compared with normal human germ cells. Functional analysis of the GDNF biological activity was performed on TCam-2 seminoma cell line. Reverse transcription-PCR (RT-PCR) and immunohistochemical analyses demonstrate that TCam-2 cells express both GFRA1 and Ret mRNA, but only GFRA1 was detected at the protein level. In TCam-2 cells, although GDNF is not mitogenic, it is able to induce migration, as demonstrated by a Boyden chamber assay, possibly through the Src and MEK pathways. Moreover, GDNF promotes invasive behaviour, an effect dependent on pericellular protease activity, possibly through the activity of matrix metalloproteinases. GFRA1 over-expression in CIS and seminoma cells, along with the functional analyses in TCam-2 cells, suggests an involvement of the GDNF pathway in the progression of testicular germ cell cancer.

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-ß 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.

Lactoferrin decreases inflammatory response by cystic fibrosis bronchial cells invaded with Burkholderia cenocepacia iron-modulated biofilm.

In cystic fibrosis (CF) high iron concentration in airway secretion plays a pivotal role in bacterial multiplication and biofilm formation as well as in inflammatory response. Burkholderia cenocepacia, an opportunistic facultative pathogen responsible for chronic lung infections and cepacia syndrome, recurrently infects CF patients. Lactoferrin (Lf), an iron binding multifunctional glycoprotein synthesized by exocrine glands and neutrophils, has been found at higher concentration in the airway secretions of infected CF patients than in healthy subjects. Here the influence of milk derivative bovine lactoferrin (bLf), an emerging important regulator of iron and inflammatory homeostasis, on invasiveness of B. cenocepacia iron-modulated biofilm, as well as on inflammatory response by infected CF bronchial (IB3-1) cells, is reported. bLf did not significantly affect invasion efficacy by biofilmforming B. cenocepacia clinical strains. Conversely, the addition of bLf to cell monolayers during infection significantly decreased the pro-inflammatory Interleukin (IL)-1beta and increased the anti-inflammatory IL-11 expression compared to that observed in cells infected in the absence of bLf. The bLf ability to modulate genes expressed following B. cenocepacia infection seems related to its localization to the nucleus of infected IB3-1 cells. These results provide evidence for a role of bLf in the protection of infected CF cells from inflammation-related damage, thus extending the therapeutic potential of this multifunctional natural protein.

Improved procedure for the measurement of telomere length in whole cells by PNA probe and flow cytometry.

OBJECTIVES: Peptide nucleic acid (PNA) probes hybridize to denatured telomeric sequences in cells permeabilized in hot formamide. In reported protocols, the hybridization was conducted in solutions with high formamide concentrations to avoid the DNA renaturation that can hamper binding of the oligo-PNA probe to specific sequences. We postulated that telomeric DNA, confined in the nuclear microvolume, is not able to properly renature after hot formamide denaturation. Therefore, to improve hybridization conditions between the probe and the target sequences, it might be possible to add probe to sample after the complete removal of formamide. MATERIALS AND METHODS: After telomeric DNA denaturation in hot formamide solution and several washes to remove the ionic solvent, cells were hybridized overnight at room temperature with human telomere-specific PNA probe conjugated with Cy5 fluorochrome, Cy5-OO-(CCCTAA)(3) . After stringency washes and staining with ethidium bromide, the cells were analysed by flow cytometry and by using a confocal microscope. RESULTS: Using three continuous cell lines, different in DNA content and telomere length, and resting human peripheral blood T and B lymphocytes, we demonstrated that the oligo-PNA probe hybridized to telomeric sequences after complete removal of formamide and that in the preserved nucleus, telomeric sequence denaturation is irreversible. CONCLUSION: According to our experience, oligo-PNA binding results is efficient, specific and proportional to telomere length. These, our original findings, can form the technological basis of actual in situ hybridization on preserved whole cells.

Streptococcus mutans and Streptococcus sobrinus are able to adhere and invade human gingival fibroblast cell line.

Streptococcus mutans and Streptococcus sobrinus, the principal etiologic agents of caries decay of teeth, are generally acquired in oral cavity at the moment of tooth eruption. However, as S. mutans has been detected in oral cavity of predentate children, the eruption of teeth seems not to be a necessary prerequisite, suggesting that this species may be not confined to dental plaque. Here, we evaluate the ability of S. mutans and S. sobrinus in planktonic and biofilm lifestyle to adhere, invade and survive within human gingival fibroblast (HGF-1) cells. Planktonic and biofilm streptococci adhered and invaded host cells to different extents, showing higher efficiencies of biofilm than planktonic counterparts. Moreover, planktonic and biofilm streptococci showed the same percentage of survival within host cells. Transmission electron and confocal microscopy observations confirmed intracellular localization of planktonic and biofilm bacteria. The adhesion, invasion and survival abilities within human oral cells may be considered S. mutans and S. sobrinus virulence mechanisms to colonize and persist in the oral cavity in the absence of tooth surface.

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.

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.

Measuring tendon properties in mdx mice: cell viability and viscoelastic characteristics.

Muscular dystrophy is a genetic disorder of skeletal muscle characterized by progressive muscle weakness. Here we assessed whether muscle wasting affects cell viability and mechanical properties of extensor digitorum longus (EDL) and of tibialis anterior (TA) tendons from mdx dystrophic mice compared to wild type (WT) mice. mdx mice represent the classical animal model for human Duchenne muscular dystrophy, and show several signs of the pathology, including a decrease in specific force and an increase of fibrotic index. Cell viability of tendons was evaluated by histological analysis, and viscoelastic properties have been assessed by a rapid measurement protocol that allowed us to compute, at the same time, tissue complex compliance for all the frequencies of interest. Confocal microscopy and mechanical properties measurements revealed that mdx tendons, compared to WT ones, have an increase in the number of dead cells and a significant reduction in tissue elasticity for all the frequencies that were tested. These findings indicate a reduced quality of the tissue. Moreover, mdx tendons have an increase in the viscous response, indicating that during dynamic loading, they dissipate more energy compared to WT. Our results demonstrate that muscular dystrophy involves not only muscle wasting, but also alteration in the viscoelastic properties of tendons, suggesting a paracrine effect of altered skeletal muscle on tendinous tissue.

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.

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.

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.