Gelatinase A secretion and its control in peritubular and Sertoli cell cultures: effects of hormones, second messengers and inducers of cytokine production

Matrix metalloproteinase (MMP)-2, MMP-9, semen quality and sperm longevity in fractionated stallion semen

Matrix metalloproteinase (MMP)-2 and MMP-9 are gelatinases that take part in several reproductive processes. The aim of this study was to measure levels of MMP-2 and MMP-9 in fractionated stallion ejaculates, and to evaluate the association between these components and semen quality, and sperm longevity during cooled storage. Semen quality were assessed separately for sperm-rich fractions (HIGH), sperm-poor fractions (LOW), and whole ejaculate samples (WE) from 33 stallions. After cooled storage with SP either present or removed, sperm motility and DFI were determined. The relative activity of the pro-form of MMP-2, active MMP-2 and total MMP-9 were evaluated using gelatin zymography, and all were present in all fractions of the stallion's ejaculate, with higher relative activity of the latent than active forms and the highest relative activity in the HIGH fraction. The relative activities of MMP-2 and MMP-9 were positively correlated to sperm concentration and total sperm count, but only in the HIGH fraction and not in LOW or WE. The relative activities of MMPs were not related to differences in sperm longevity during cooled storage, measured as sperm motility and DFI. There was a harmful effect of SP on DFI during storage, but this effect was not associated with differences in the relative activities of MMPs. In conclusion, the relative activities of MMPs are not useful as markers for semen quality (other than sperm concentration), or sperm survival during storage in horses.

Hormonal control of Sertoli cell metabolism regulates spermatogenesis

Hormonal regulation is essential to spermatogenesis. Sertoli cells (SCs) have functions that reach far beyond the physical support of germ cells, as they are responsible for creating the adequate ionic and metabolic environment for germ cell development. Thus, much attention has been given to the metabolic functioning of SCs. During spermatogenesis, germ cells are provided with suitable metabolic substrates, in a set of events mediated by SCs. Multiple signaling cascades regulate SC function and several of these signaling pathways are hormone-dependent and cell-specific. Within the seminiferous tubules, only SCs possess receptors for some hormones rendering them major targets for the hormonal signaling that regulates spermatogenesis. Although the mechanisms by which SCs fulfill their own and germ cells metabolic needs are mostly studied in vitro, SC metabolism is unquestionably a regulation point for germ cell development and the hormonal control of these processes is required for a normal spermatogenesis.

Detection of matrix metalloproteinase (MMP)-2 and MMP-9 in canine seminal plasma

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that play a central role in degradation of protein components of the extracellular matrix and basement membrane. Previous studies have shown that MMP-2 and MMP-9 are present in human seminal plasma, but there is little information available on the presence of MMPs in canine seminal plasma. This study aims to investigate the presence of MMPs in canine seminal plasma and their clinical manifestation at the level of various semen parameters in canine species. Latent and active forms of MMP-2 and MMP-9 were evaluated using gelatin zymography and their association with semen parameters was examined. Results demonstrate that both latent and active forms of MMP-2 and MMP-9 are present in canine seminal plasma and the latent forms are predominant. The latent and active MMP-9 activities were elevated in the semen with unsatisfactory quality traits and proMMP-2 was inversely correlated with semen quality whereas, MMP-2 was positively correlated with semen quality traits. These findings suggest that proMMP-9 and MMP-9 activation contributes to the variation in semen, while the activation of MMP-2 improves the sperm functionality.

CD147 is required for matrix metalloproteinases-2 production and germ cell migration during spermatogenesis

Spermatogenesis is a highly programmed process that requires the degradation of the extracellular matrix and the remodeling of tight junctions (TJ) to facilitate differentiating germ cell migration. Matrix metalloproteinases (MMPs) are essential in regulating Sertoli cell TJ in the testis. CD147 is known to stimulate the production of MMPs in tumor metastasis and its knockout mice are infertile. However, the functional relationship between CD147 and MMPs in spermatogenesis has not been investigated. In the present study, we examined the expression profile of CD147 and MMPs during mouse testicular development by RT-PCR, western blot and immunofluorescence staining. We also examined CD147 involvement in the production of MMP-2 and the migration of germ cells (GC-1 and GC-2 cells) using CD147 antibody or synthetic microRNA mimics-mediated knockdown. The results showed that CD147 was present at all stages of testicular development from 7 to 56 days post-partum (dpp). CD147 expression was found to increase after 21 days from moderate levels in 7 and 14 days. Of the eight MMPs studied, MMP-2, MMP-7, MMP-9 and MMP-23 were detected to have changes in expression during testicular development, with MMP-2 showing the largest change. CD147 and MMP-2 were co-localized in spermatogonia, spermatocytes and round spermatids in mouse testis, while in human testis, they were co-localized in spermatocytes and round spermatids. MMP-2 expression and migration of GC-1 and GC-2 cells were reduced by interfering with CD147 expression and function in vitro. These data suggest that CD147 regulates migration of spermatogonia and spermatocytes via induction of MMP-2 production during spermatogenesis.

Participation of phosphatidyl inositol 3-kinase/protein kinase B and ERK1/2 pathways in interleukin-1β stimulation of lactate production in Sertoli cells

Interleukin-1β (IL1β ) belongs to a set of intratesticular regulators that provide the fine-tuning of cellular processes implicated in the maintenance of spermatogenesis. The aim of the present study was to analyze the signaling pathways that may participate in IL1β regulation of Sertoli cell function. Sertoli cell cultures from 20-day-old rat were used. Stimulation of the cultures with IL1β showed increments in phosphorylated protein kinase B (PKB), P70S6K, and ERK1/2 levels. A phosphatidyl inositol 3-kinase (PI3K) inhibitor (wortmannin (W)), a mammalian target of rapamycin inhibitor (rapamycin (R)), and a MEK inhibitor (PD98059 (PD)) were utilized to evaluate the participation of PI3K/PKB, P70S6K, and ERK1/2 pathways in the regulation of lactate production by IL1β . PD and W, but not R, decreased IL1β-stimulated lactate production. The participation of these pathways in the regulation of glucose uptake and lactate dehydrogenase (LDH) A mRNA levels by IL1β was also analyzed. It was observed that W decreased IL1β-stimulated glucose uptake, whereas PD and R did not modify it. On the other hand, PD decreased the stimulation of LDH A mRNA levels by IL1β , whereas W and R did not modify it. In summary, results presented herein demonstrate that IL1β stimulates PI3K/PKB-, P70S6K-, and ERK1/2-dependent pathways in rat Sertoli cells. Moreover, these results show that while IL1β utilizes the PI3K/PKB pathway to regulate glucose transport, it utilizes the ERK1/2 pathway to regulate LDH A mRNA levels. This study reveals that IL1β utilizes different signal transduction pathways to modify the biochemical steps that are important to regulate lactate production in rat Sertoli cells.

Microarray analysis of androgen-regulated gene expression in testis: the use of the androgen-binding protein (ABP)-transgenic mouse as a model

BACKGROUND

Spermatogenesis is an androgen-dependent process, yet the molecular mechanisms of androgens' actions in testis are poorly understood. Transgenic mice overexpressing rat androgen-binding protein (ABP) in their testes have reduced levels of intratesticular androgens and, as a result, show a progressive impairment of spermatogenesis. We used this model to characterize changes in global gene expression in testis in response to reduced bioavailability of androgens.

METHODS

Total RNA was extracted from testes of 30-day old transgenic and wild-type control mice, converted to cRNA, labeled with biotin, and hybridized to oligonucleotide microarrays. Microarray results were confirmed by real-time reverse transcription polymerase chain reaction.

RESULTS

Three-hundred-eighty-one genes (3.05% of all transcripts represented on the chips) were up-regulated and 198 genes (1.59%) were down-regulated by at least a factor of 2 in the androgen-deficient animals compared to controls. Genes encoding membrane proteins, intracellular signaling molecules, enzymes, proteins participating in the immune response, and those involved in cytoskeleton organization were significantly overrepresented in the up-regulated group. Among the down-regulated transcripts, those coding for extracellular proteins were overrepresented most dramatically, followed by those related to proteolysis, cell adhesion, immune response, and growth factor, cytokine, and ion channel activities. Transcripts with the greatest potential impact on cellular activities included several transcription factors, intracellular signal transducers, secreted signaling molecules and enzymes, and various cell surface molecules. Major nodes in the up-regulated network were IL-6, AGT, MYC, and A2M, those in the down-regulated network were IL-2, -4, and -10, MAPK8, SOCS1, and CREB1.

CONCLUSION

Microarray analysis followed by gene ontology profiling and connectivity analysis identified several functional groups of genes and individual genes responding to sustained reduction of androgen levels in the mouse testis. These include genes whose products function as transcription factors, cell surface molecules including ion channels, extra- and intracellular signaling molecules, and secreted enzymes with the potential of regulating cell-to-cell attachment. The transcription factors CREB1 (down-regulated) and MYC (up-regulated) may mediate the most important initial phases of the testicular response to reduced levels of androgens. These results suggest specific avenues for further research that will lead to a better understanding of how androgens regulate spermatogenesis.

Sertoli cell expression of steroidogenic acute regulatory protein-related lipid transfer 1 and 5 domain-containing proteins and sterol regulatory element binding protein-1 are interleukin-1beta regulated by activation of c-Jun N-terminal kinase and cyclooxygenase-2 and cytokine induction

In testicular Sertoli cells, IL-1beta regulates steroid, lactate, and transferrin secretion; although each influences germ cell development and spermatogenesis, little is known about the signaling mechanisms involved. In other cell types, IL-1beta potently induces reactive oxygen species and/or cyclooxygenase-2 (COX-2). In contrast, in Sertoli cells, IL-1beta does not generate reactive oxygen species, but rapidly phosphorylates c-Jun-NH(2)-terminal kinase (JNK), but not p44/42 or p38 MAPK. Phosphorylated JNK stimulates COX-2 activity, mediating the expression of ILs and steroidogenic acute regulatory (StAR)-related (StAR-related lipid transfer protein domain containing) proteins D1 and D5, but not D4. In a time- and dose-dependent manner, IL-1beta rapidly increases levels of COX-2 mRNA (2-fold); induction of COX-2 protein (50-fold) requires de novo protein synthesis. Concomitantly, increases in IL-1alpha, IL-6, and IL-1beta mRNAs (1-3 h) are observed. As StAR-related lipid transfer protein domain containing protein 1 (StARD1) mRNA decreases, StARD5 mRNA increases; substantial recovery phase induction of StARD1 mRNA above control is noted (24 h). Inhibition of JNK or COX-2 activities prevents IL-1beta induction of IL and StARD5 mRNAs and subsequent increases in StARD1 mRNA (24 h), indicating that these effects depend on the activation of both enzymes. StARD1 and D5 protein levels are significantly altered, consistent with posttranscriptional and posttranslational regulation. IL-1beta rapidly decreases levels of precursor and mature sterol regulatory element-binding protein-1, changes not altered by cycloheximide, suggesting coordinate regulation of StARD1 and -D5, but not StARD4, expression. These data demonstrate that JNK and COX-2 activities regulate Sertoli cytokines and particularly START domain-containing proteins, suggesting protective stress responses, including transcription and protein and lipid regulation, within this specialized epithelium.

BSP A1/A2-like proteins in ram seminal plasma

The objective of this study was to assess the protein profile of ovine seminal plasma using 2D-PAGE and verify if BSP A1/A2 are present in ovine seminal plasma. Seminal plasma was collected from three mature rams and pooled to eliminate individual differences. Seminal plasma samples were submitted to 2D-PAGE using 12% acrylamide gels. The image analysis software identified 21 protein spots on the air-dried gel, with molecular weight ranging from 15 to 115 kDa and pI 3.2 to 8.7. The most prominent spots were those <30 kDa. The most intensely stained spots were: 3 (18-19 kDa, pI 4.8-5.0), 5 (17-18 kDa, pI 5.0-5.2), 7 (15-16 kDa, pI 6.2-6.4), and 23 (105-108 kDa, pI 6.8-7.0). Three of these spots (spots 3, 5 and 7, respectively) accounted for 41.1% of the relative intensity of the spots of the gels, based on the intensity of the Comassie blue staining. Western blot analysis indicated that spots 3 and 5 were similar to BSP A1/A2 (16.5, pI 4.7-5.0 and 16 kDa, pI 4.9-5.2) identified in Manjunath's studies [Manjunath P, Sairam MR. Purification and biochimical characterization of three major acid proteins (BSP A1, BSP A2 and BSP A3) from bovine seminal plasma. Biochem J 7 (1987) 685-92.], based on the specific reaction of the polyclonal antibody to those spots.

The Blood‐Testis Barrier: Its Biology, Regulation, and Physiological Role in Spermatogenesis

The blood-testis barrier (BTB) in mammals, such as rats, is composed of the tight junction (TJ), the basal ectoplasmic specialization (basal ES), the basal tubulobulbar complex (basal TBC) (both are testis-specific actin-based adherens junction [AJ] types), and the desmosome-like junction that are present side-by-side in the seminiferous epithelium. The BTB physically divides the seminiferous epithelium into basal and apical (or adluminal) compartments, and is pivotal to spermatogenesis. Besides its function as an immunological barrier to segregate the postmeiotic germ-cell antigens from the systemic circulation, it creates a unique microenvironment for germ-cell development and confers cell polarity. During spermatogenesis, the BTB in rodents must physically disassemble to permit the passage of preleptotene and leptotene spermatocytes. This occurs at late stage VII through early stage VIII of the epithelial cycle. Studies have shown that this dynamic BTB restructuring to facilitate germ-cell migration is regulated by two cytokines, namely transforming growth factor-beta3 (TGF-beta3) and tumor necrosis factor-alpha (TNFalpha), via downstream mitogen-activated protein kinases. These cytokines determine the homeostasis of TJ- and basal ES-structural proteins, proteases, protease inhibitors, and other extracellular matrix (ECM) proteins (e.g., collagen) in the seminiferous epithelium. Some of these molecules are known regulators of focal contacts between the ECM and other actively migrating cells, such as macrophages, fibroblasts, or malignant cells. These findings also illustrate that cell-cell junction restructuring at the BTB is regulated by mechanisms involved in the junction turnover at the cell-matrix interface. This review critically discusses these latest findings in the field in light of their significance in the biology and regulation of the BTB pertinent to spermatogenesis.

Sertoli-Sertoli and Sertoli-germ cell interactions and their significance in germ cell movement in the seminiferous epithelium during spermatogenesis

Spermatogenesis is the process by which a single spermatogonium develops into 256 spermatozoa, one of which will fertilize the ovum. Since the 1950s when the stages of the epithelial cycle were first described, reproductive biologists have been in pursuit of one question: How can a spermatogonium traverse the epithelium, while at the same time differentiating into elongate spermatids that remain attached to the Sertoli cell throughout their development? Although it was generally agreed upon that junction restructuring was involved, at that time the types of junctions present in the testis were not even discerned. Today, it is known that tight, anchoring, and gap junctions are found in the testis. The testis also has two unique anchoring junction types, the ectoplasmic specialization and tubulobulbar complex. However, attention has recently shifted on identifying the regulatory molecules that "open" and "close" junctions, because this information will be useful in elucidating the mechanism of germ cell movement. For instance, cytokines have been shown to induce Sertoli cell tight junction disassembly by shutting down the production of tight junction proteins. Other factors such as proteases, protease inhibitors, GTPases, kinases, and phosphatases also come into play. In this review, we focus on this cellular phenomenon, recapping recent developments in the field.

Extracellular matrix: recent advances on its role in junction dynamics in the seminiferous epithelium during spermatogenesis

Spermatogenesis takes place in the seminiferous epithelium of the mammalian testis in which one type A1 spermatogonium (diploid, 2n) gives rise to 256 spermatids (haploid, 1n). To accomplish this, developing germ cells, such as preleptotene and leptotene spermatocytes, residing in the basal compartment of the seminiferous epithelium must traverse the blood-testis barrier (BTB) entering into the adluminal compartment for further development into round, elongating, and elongate spermatids. Recent studies have shown that the basement membrane in the testis (a modified form of extracellular matrix, ECM) is important to the event of germ cell movement across the BTB because proteins in the ECM were shown to regulate BTB dynamics via the interactions between collagens, proteases, and protease inhibitors, possibly under the regulation of cytokines. While these findings are intriguing, they are not entirely unexpected. For one, the basement membrane in the testis is intimately associated with the BTB, which represents the basolateral region of Sertoli cells. Also, Sertoli cell tight junctions (TJs) that constitute the BTB are present side-by-side with cell-cell actin-based adherens junctions (AJ, such as basal ectoplasmic specialization [ES]) and intermediate filament-based desmosome-like junctions. As such, the relative morphological layout between TJs, AJs, and desmosome-like junctions in the seminiferous epithelium is in sharp contrast to other epithelia where TJs are located at the apical portion of an epithelium or endothelium, furthest away from ECM, to be followed by AJs and desmosomes, which in turn constitute the junctional complex. For another, anchoring junctions between a cell epithelium and ECM found in multiple tissues, also known as focal contacts (or focal adhesion complex, FAC, an actin-based cell-matrix anchoring junction type), are the most efficient junction type that permits rapid junction restructuring to accommodate cell movement. It is therefore physiologically plausible, and perhaps essential, that the testis is using some components of the focal contacts to regulate rapid restructuring of AJs between Sertoli and germ cells when germ cells traverse the seminiferous epithelium. Indeed, recent findings have shown that the apical ES, a testis-specific AJ type in the seminiferous epithelium, is equipped with proteins of FAC to regulate its restructuring. In this review, we provide a timely update on this exciting yet rapidly developing field regarding how the homeostasis of basement membrane in the tunica propria regulates BTB dynamics and spermatogenesis in the testis, as well as a critical review on the molecular architecture and the regulation of ES in the seminiferous epithelium.

Interactions of proteases, protease inhibitors, and the beta1 integrin/laminin gamma3 protein complex in the regulation of ectoplasmic specialization dynamics in the rat testis

During spermatogenesis, developing germ cells migrate progressively across the seminiferous epithelium. This event requires extensive restructuring of cell-cell actin-based adherens junctions (AJs), such as the ectoplasmic specialization (ES, a testis-specific AJ type), between Sertoli cells and elongating/elongate spermatids. It was postulated that proteases and protease inhibitors worked in a yin-yang relationship to regulate these events. If this is true, then it is anticipated that both proteases and protease inhibitors are found at the ES. Indeed, matrix metalloprotease (MMP)-2, membrane-type 1 (MT1)-MMP and their inhibitor, tissue-inhibitor of metalloproteases (TIMP)-2, were shown to localize at the apical ES. In order to identify the putative MMP substrate as well as the unknown binding ligand for alpha6beta1 integrin in the ES, immunofluorescent microscopy coupled with immunoprecipitation techniques were used to demonstrate that laminin gamma3, largely a germ cell product, was present at the apical ES and could form a bona fide complex with beta1-integrin. Furthermore, the structural interactions of MMP-2 and MT1-MMP with laminin gamma3 and beta1-integrin, but not with N-cadherin or nectin-3, have implicated the crucial role of MMP-2/MT1-MMP in the regulation of integrin/laminin-based ES dynamics. Using an in vivo model to study AJ dynamics where adult rats were treated with 1-(2,4-dichlorobenzyl)-indazole-3-carbohydrazide (AF-2364) to disrupt Sertoli-germ cell adhesive function, an induction of active MMP-2, active MT1-MMP and TIMP-2 but not active MMP-9 was detected between 0.5 and 8 h after AF-2364 treatment. This time frame coincided with the depletion of elongating/elongate spermatids from the epithelium, illustrating the synergistic relationships between MMP-2, MT1-MMP, and TIMP-2 in AJ disassembly. Perhaps the most important of all, the use of a specific MMP-2 and MMP-9 inhibitor, (2R)-2-[(4-biphenylylsulfonyl)amino]-3-phenylpropionic acid, could effectively delay the AF-2364-induced elongating/elongate spermatid loss from the epithelium, demonstrating the pivotal role of MMP-2 activation in ES disassembly. Collectively, these studies illustrate that the beta1-integrin/laminin gamma3 complex is a putative ES-structural protein complex, which is regulated, at least in part, by the activation of MMP-2 involving MT1-MMP and TIMP-2 at the apical ES. The net result of this interaction likely regulates germ cell movement in the seminiferous epithelium.

Comparison, characterization, and identification of proteases and protease inhibitors in epididymal fluids of domestic mammals. Matrix metalloproteinases are major fluid gelatinases

The testicular and epididymal fluids of ram, boar, and stallion were analyzed by means of one-dimensional and two-dimensional gelatin gel zymography. Five main gelatinolytic bands were revealed in the ram and at least seven were observed in the boar and stallion. These proteolytic bands showed regionalized distribution throughout the organs. The two main proteolytic activities at around 54-66 kDa retrieved in all three species were inhibited by EDTA and phenanthroline, indicating that they were metallo-dependent enzymes. The activity of some of the low-molecular-weight gelatinases was also decreased by EDTA, whereas others were inhibited by serine protease inhibitors. One of the main proteases at 60-62 kDa from the caput fluid of the stallion and the ram was N-terminal sequenced; in both cases, high sequence homology was found with the N-terminal of the matrix-metalloproteinase-2 pro-form (pro-MMP-2). Antibodies against MMP-2, MMP-3, and MMP-9 gelatinases confirmed the regional distribution in the fluids of pre -, pro-, active, or degraded forms of these metalloproteases in all three species. We also observed the presence of acrosin in epididymal fluids, which was probably released by dead spermatozoa, but this enzyme did not explain all the serine protease activity. Moreover, the majority of this enzyme is bound to the protease inhibitor alpha(2)-macroglobulin, which is present in the fluids of all three species. TIMP-2, a potent inhibitor of MMPs, was present in the fluid of the caput regions in the ram and boar, and in the caput and caudal fluids of the stallion. This study demonstrated that similar types of proteases and inhibitors are regionally distributed in the epididymal fluids of three domestic species, suggesting an identical role in the sperm maturation process, the plasticity of this organ, or both.

Evidence that MMP-2 and TIMP-2 are at play in the FSH-induced changes in Sertoli cells

FSH has been shown to elicit in vitro changes in the Sertoli cell cytoskeleton through involving proteases, and cytochalasin-D mimics FSH. Testis extracts were screened (RT-PCR) for various metalloproteinases (MMPs), 20-day-old rat Sertoli cells were purified, cultured and treated with FSH, cytochalasin D and TNFalpha (to antagonize FSH action). Cell shape (phase-contrast microscopy) and levels for MMP-2 (gelatin zymography) and its inhibitor TIMP-2 (Northern and Western blot) were monitored. TNFalpha-treated cells spread readily and grew larger than FSH-treated cells. Cytochalasin-D mimicked FSH, and MMP-2 production and TIMP-2 gene expression were augmented. Interestingly, TNFalpha reversed FSH- and cytochalasin D-induced effects both on cell shape and on MMP-2 and TIMP-2. These effects occurred during the first 48 h of culture, when Sertoli cells migrated from the freshly dispersed aggregates, but not once cells were organized in monolayers. MMP-2 and TIMP-2 are likely involved in the FSH-induced changes in Sertoli cells.

Expression of matrix metalloproteases (MMP-2, MT1 -MMP) and their tissue inhibitor (TIMP-2) by rat sertoli cells in culture: implications for spermatogenesis

During testicular development and maturation, extracellular matrix (ECM) remodelling is a fundamental process which requires the presence of several proteases and protease inhibitors. Among the proteases, a pivotal role has been proposed for matrix metalloproteases (MMPs) and their tissue inhibitors (TIMPs). Here we report an analysis of MMP-2, MT1-MMP and TIMP-2 expression by rat Sertoli cells in culture using RT-PCR and zymographic techniques. Stimulating Sertoli cells with follicle-stimulating hormone (FSH) in vitro induced evident changes in the level of their mRNA in a time-dependent manner. In the case of TIMP-2 and MT1-MMP, the respective transcripts were augmented up to three-fold after 24 h of treatment, and MMP-2 transcripts increased by four times in the same period. MMP-2 activity determined by gelatin zymography showed an increase in enzyme secretion after FSH stimulation. The results of this study suggest that: (i) at the surface of Sertoli cells pro-MMP-2 activation mediated by MT1-MMP may occur, involving TIMP-2 as a receptor; and (ii) the expression of these molecules is not constitutive in this cell type, but may be modulated by FSH and is therefore implicated in spermatogenesis.

Secretion of gelatinases and activation of gelatinase A (MMP-2) by human rheumatoid synovial fibroblasts

In monolayer cultures human rheumatoid synovial fibroblasts (HRSF) secrete gelatinase A (MMP-2) and, unlike other human fibroblasts, to a minor extent also gelatinase B (MMP-9) as inactive proenzymes. In this regard HRSF resemble the fibrosarcoma cell line HT-1080. Unlike HT-1080, however, HRSF do not increase the secretion of MMP-9 in response to phorbol-12-myristate-13-acetate. This indicates that in HRSF the protein kinase C pathway for an enhanced MMP-9 secretion is inactive. None of the substances used in our study increased MMP-9 secretion, but some of them inhibited MMP-9 secretion. The secretion of MMP-2 could not be enhanced either, not even by dbcAMP, which has been reported to be effective in Sertoli and peritubular cells. Activation of MMP-2 in HRSF could be induced by treatment with concanavalin A (ConA) or cytochalasin D, as was shown for other cell types. This activation was not accompanied by a significant change in the amount of secreted TIMP-1 and TIMP-2. In contrast to reports on human skin fibroblasts, however, the activation of MMP-2 could not be induced in HRSF by treatment of the cells with monensin or sodium orthovanadate. Moreover, monensin was shown to act as an inhibitor of ConA- or cytochalasin D-mediated activation. Additionally, and in contrast to a report on a rat fibroblast cell line, MMP-2 activation is not mediated via the MAP kinase pathway in HRSF: PD 98059, a specific inhibitor of MAP kinase kinase, did not inhibit the activation of MMP-2. Similarly ineffective were PD 169316, an inhibitor for p38 MAP kinase, other inhibitors for protein kinases as lavendustin A, Gö 6983, wortmannin, rapamycin, as well as the protein tyrosine kinase inhibitors herbimycin A and genistein. Only staurosporin, a broad spectrum inhibitor of protein kinases, and the ionophores monensin and A 23187 effectively inhibited MMP-2 activation in HRSF. Our results demonstrate that MMP-2 can be activated by quite different pathways, and that different cells, even when belonging to the fibroblast family, do not necessarily use the same activating pathways.

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

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

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.

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

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

Regulation of proteoglycan and hyaluronan synthesis by elevated level of intracellular cyclic adenosine monophosphate in peritubular cells from immature rat testis

The effects of an increase in intracellular cAMP concentration on proteoglycan (PG) synthesis by peritubular (PT) cells from immature rat testis were investigated. In the presence of dBcAMP for 72 h, the [3H]-hexosamine incorporation in secreted PG and in cell-associated PG was reduced, whereas [35S]-sulfate radioactivity was enhanced in secreted PG and not affected in cell-associated PG. Cholera toxin and IBMX, known to generate high intracellular cAMP levels, induced similar changes. Cyclic AMP did not alter PG protein moiety synthesis but enhanced PG turnover. Cholera toxin and dBcAMP profoundly modified PG characteristics: (1) Apparent molecular weight of PG was increased. (2) This was due to an increase in glycosaminoglycans (heparan sulfate (HS) and chondroitin sulfate (CS)) length. (3) The number of glycosaminoglycan chains was presumably reduced. (4) Heparan sulfate and chondroitin sulfate chains of medium and cell layer-associated PG appeared oversulfated. (5) The pattern of cell layer associated PG was modified with a decrease in HSPG and a correlative increase in CSPG. Cholera toxin and dBcAMP also dramatically stimulated hyaluronan synthesis by possible phosphorylation induced activation of hyaluronan synthase(s).

Possible involvement of proteases in the regulation of spermatogenesis

Proteolytic enzymes, which are synthesized and secreted by cells of the seminiferous tubule of the testis, have important functions in spermatogenesis. We performed metabolic studies using small peptide hormones as a substrate to investigate the activity of proteases in cultured Sertoli cells of the rat. High-performance liquid chromatographic analysis of the cell culture supernatants showed cleavage of met- and leu-enkephalin, substance P, and bradykinin. No peptidolysis was observed for the cyclic peptide oxytocin. The hormone cleavage pattern and the use of specific protease inhibitors in peptide degradation experiments demonstrated activities of several proteases in Sertoli cells. These are mainly metalloproteinases including neutral metalloendopeptidases, angiotensin-converting enzyme and aminopeptidases. In addition, activities of serine and aspartic proteases were detected. Only marginal proteolytic activities were observed in Sertoli cell conditioned supernatants, indicating that the investigated proteases are mainly located on Sertoli cell membranes. The peptide hormones used in this study have been found to play a potential role in the endocrine, paracrine or autocrine regulation of testicular cells. The membrane-associated proteases reported here may therefore be involved in the metabolism and inactivation of these peptides.

Regulation of gelatinase B (MMP-9) in leukocytes by plant lectins

The stimulatory or inhibitory effects of plant lectins on the production of gelatinase A (MMP-2) and gelatinase B (MMP-9) by mononuclear white blood cells was investigated by substrate zymography. Leukocyte cultures from 24-h old buffy coats were spontaneously activated and produced high levels of gelatinase B. Using such cultures the suppressing activity of the Datura stramonium, Viscum album, Bauhinia purpurea, Triticum aestivum and Maackia amurensis lectins on gelatinase B induction were demonstrated. When fresh leukocyte preparations from single blood donors were used, low levels of gelatinase B were produced. The induction of gelatinase B was confirmed for concanavalin A and phytohaemagglutinin (PHA-L4). In addition, the Urtica dioica, Calystegia sepium, Convolvulus arvensis and Colchicum autumnale lectins were documented as novel and potent inducers of gelatinase B. Since high circulating gelatinase B levels are associated with specific pathologies, including shock syndromes, the acute toxicity of many lectins might be partially mediated or influenced by gelatinase induction.

Protease-protease inhibitor interactions in Sertoli cell-germ cell crosstalk

Peritubular cells, Sertoli cells, and germ cells of the seminiferous tubule synthesize and secrete several proteases and protease inhibitors. Experimental evidence suggests that the complex network of proteolytic enzyme activity and their regulation by protease inhibitors play an important role in male reproduction. Interaction between protease and protease inhibitors seems to play an important role in remodeling and restructuring of the seminiferous tubule during spermatogenesis. Controlled proteolytic activity is also involved in the migration of germ cells from the basal compartment to the lumen of the seminiferous epithelium, and in the release of spermatids during spermiation. The recently reported occurrence of Sertoli cell membrane-associated proteases indicate the possible involvement of regulatory peptide systems within the testis. This view is supported by the detection of all components of one of these paracrine systems, the kallikrein-kinin system, in cells of the seminiferous tubule.