Sertolin is a novel gene marker of cell-cell interactions in the rat testis

Sertolin mediates blood-testis barrier restructuring

Two important events that occur during mammalian spermatogenesis are the release of elongated spermatids at late stage VIII of the seminiferous epithelial cycle and the restructuring of the blood-testis barrier (BTB) during stages VIII-XI. Still, it is not completely understood how these cellular events are accomplished within the seminiferous epithelium. In the present study, we investigate how sertolin, a protein that was initially identified, cloned, and partially characterized by our laboratory, functions in these critical events. Sertolin was found at the BTB, as well as at the apical ectoplasmic specialization and apical tubulobulbar complex, where it colocalized with epidermal growth factor receptor kinase substrate 8 and actin-related protein 3, two actin-regulatory proteins. Knockdown of sertolin by RNA interference showed Sertoli cell barrier function to be enhanced when assessed by transepithelial electrical resistance measurements and immunolocalization experiments. By contrast, the integrity of the BTB was disrupted when sertolin was overexpressed in vitro and in vivo. Sertolin overexpression also prompted germ cell loss from the seminiferous epithelium. Taken collectively, these results suggest that sertolin may be involved in coordinating spermatid release and BTB restructuring during spermatogenesis in the rat.

Defective CFTR-dependent CREB activation results in impaired spermatogenesis and azoospermia

Cystic fibrosis (CF) is the most common life-limiting recessive genetic disease among Caucasians caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) with over 95% male patients infertile. However, whether CFTR mutations could affect spermatogenesis and result in azoospermia remains an open question. Here we report compromised spermatogenesis, with significantly reduced testicular weight and sperm count, and decreased cAMP-responsive element binding protein (CREB) expression in the testes of CFTR knockout mice. The involvement of CFTR in HCO₃⁻ transport and the expression of the HCO₃⁻ sensor, soluble adenylyl cyclase (sAC), are demonstrated for the first time in the primary culture of rat Sertoli cells. Inhibition of CFTR or depletion of HCO₃⁻ could reduce FSH-stimulated, sAC-dependent cAMP production and phosphorylation of CREB, the key transcription factor in spermatogenesis. Decreased CFTR and CREB expression are also observed in human testes with azoospermia. The present study reveals a previously undefined role of CFTR and sAC in regulating the cAMP-CREB signaling pathway in Sertoli cells, defect of which may result in impaired spermatogenesis and azoospermia. Altered CFTR-sAC-cAMP-CREB functional loop may also underline the pathogenesis of various CF-related diseases.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced cytotoxicity accompanied by oxidative stress in rat Sertoli cells: Possible role of mitochondrial fractions of Sertoli cells

TCDD, as an endocrine disruptor, is known to impair testicular functions and fertility. To elucidate the mechanism(s) underlying the testicular effects of TCDD, the potential toxicity of TCDD on Sertoli cells was investigated. Furthermore, the study aims to delineate whether mitochondrial fractions of Sertoli cells are involved in mediating the testicular effects of TCDD. Adult rat Sertoli cells were incubated with (5, 10 or 15nM) of TCDD for 6, 12 or 24h. Cell viability, lactate and LDH leakage into media along with lipid peroxidation, ROS generation, SOD, CAT, GPx, GR, γ-GT and β-glucuronidase activities, GSH content and Δψ(m) were measured. Superoxide anion production, COX and cardiolipin content were measured in mitochondrial fractions. Cell viability was significantly decreased while lactate and LDH leakage into media were increased. ROS generation along with lipid peroxidation was also increased. SOD, CAT, GPx, GR activities and GSH content were significantly decreased. γ-GT and β-glucuronidase activities were also decreased. Superoxide anion production was increased while COX activity and cardiolipin content were decreased in mitochondrial fractions. Moreover, the Δψ(m) was significantly decreased as measured in Sertoli cells. In conclusion, TCDD impairs Sertoli cell functions and this effect is, at least in part, attributed to oxidative stress. We have also found that TCDD increases mitochondrial superoxide anion production and decreases Δψ(m), COX activity and mitochondrial cardiolipin content. Our findings suggest that mitochondria may play an important role in ROS production, leading to the TCDD-induced oxidative stress response and resulting toxicological consequences in rat Sertoli cells.

Distinct expression of interleukin-1α, interleukin-1β, and interleukin-1 receptor antagonist in testicular tissues and cells from human biopsies with normal and abnormal histology

Cytokines are paracrine/autocrine growth factors known to affect testicular cell functions. The cellular origin and expression levels of interleukin-1 (IL-1) in human normal and pathological testicular biopsies are not yet clear. In the present study, we have investigated the levels and cellular origin of IL-1 family members [IL-1α, IL-β, and IL-1 receptor antagonist (IL-1ra)] in human testicular normal and abnormal biopsies with incomplete maturation arrest (IMA) or Sertoli only syndrome (SOS), using real-time polymerase chain reaction and immunohistochemical staining analysis. Our results show that the levels of IL-1α were higher in Leydig/interstitial cells of biopsies with IMA and SOS compared with normal. The levels of IL-1α in Sertoli cells of normal biopsies were higher than IMA and SOS. The mRNA levels of IL-1α were similar in all biopsies. IL-1β levels were higher in Leydig/interstitial cells of normal biopsies compared with Sertoli and germ cells. The levels of IL-1β were similar in testicular cells of all biopsies. However, the mRNA levels of IL-1β were significantly lower in SOS and IMA biopsies compared with normal. IL-1ra was expressed only in Leydig/interstitial cells, and their expression in normal biopsies was higher than in biopsies with IMA and SOS. The mRNA levels of IL-1ra were similar in all biopsies. Thus, it is possible to suggest the involvement of IL-1 system in the regulation of spermatogenesis and male infertility.

RAB13 participates in ectoplasmic specialization dynamics in the rat testis

During spermatogenesis, leptotene spermatocytes residing in the basal compartment of the seminiferous epithelium must traverse the blood-testis barrier (BTB) to gain entry into the adluminal compartment for further development. At the same time, these as well as other germ cell types in the epithelium must retain their close association with Sertoli cells via specialized cell junctions. In this study, we demonstrate that RAB13-a guanosine triphosphatase (GTPase) known to participate in tight junction function in other epithelia-also participates in the dynamics of the ectoplasmic specialization, a testis-specific type of anchoring junction. By immunohistochemistry microscopy, RAB13 localized to the ectoplasmic specialization. Moreover, RAB13 was found to associate with vinculin (VCL) and espin (ESPN), two putative ectoplasmic specialization actin (ACT)-binding proteins, by coimmunoprecipitation and immunofluorescence microscopy experiments. To address the role of RAB13 in ectoplasmic specialization dynamics, an in vivo model was used in which administration of Adjudin induced the disassembly of Sertoli-germ cell anchoring junctions. Following administration of this drug, the RAB13 level decreased steadily when the loss in testicular weight was taken into account. Similarly, the association of RAB13 with VCL decreased but was not completely lost during Adjudin-mediated ectoplasmic specialization restructuring. Taken collectively, these results suggest that RAB13 functions in ectoplasmic specialization dynamics in the testis.

TGF-beta3 and TNFalpha perturb blood-testis barrier (BTB) dynamics by accelerating the clathrin-mediated endocytosis of integral membrane proteins: a new concept of BTB regulation during spermatogenesis

In adult mammals such as rats, the blood-testis barrier (BTB) conferred by adjacent Sertoli cells in the seminiferous epithelium segregates post-meiotic germ cell development from the systemic circulation and is one of the tightest blood-tissue barriers. Yet it must "open" transiently at stages VIII to IX of the epithelial cycle to accommodate the migration of preleptotene/leptotene spermatocytes. While this is a vital event of spermatogenesis, the mechanism(s) that regulates BTB dynamics is virtually unknown. Recent studies have suggested that transforming growth factor-beta3 (TGF-beta3) and tumor necrosis factor alpha (TNFalpha) secreted by Sertoli and germ cells into the microenvironment of the BTB are capable of inducing reversible BTB disruption in vivo, apparently by reducing the steady-state levels of occludin and zonula occludens-1 (ZO-1) at the BTB via the p38 mitogen activated protein (MAP) kinase signaling pathway. In this study, local administration of TGF-beta3 (200 ng/testis) to the testis was shown to reversibly perturb the BTB integrity in vivo. We next sought to delineate the mechanism by which these cytokines maintain the steady-state level of integral membrane proteins: occludin, junctional adhesion molecule-A (JAM-A) and N-cadherin at the BTB. Primary Sertoli cells cultured in vitro were shown to establish intact tight junctions and functional BTB within two days when assessed by transepithelial electrical resistance (TER) measurement across the cell epithelium. Sertoli cell integral membrane protein internalization at the BTB was assessed by biotinylation of cell surface proteins, to be followed by tracking the endocytosed/biotinylated proteins by using specific antibodies. Both TGF-beta3 (3 ng/ml) and TNFalpha (10 ng/ml) were shown to significantly accelerate the kinetics of internalization of JAM-A, N-cadherin, and occludin versus controls. Treatment of cells with phenylarsine oxide (PAO) at 10 microM that blocks clathrin-mediated endocytosis was shown to inhibit the TGF-beta3-induced protein internalization. This inhibition of TGF-beta3-mediated protein endocytosis was further validated by silencing of clathrin. The specific effect of TGF-beta3 on protein internalization was further confirmed by RNAi using specific TGF-beta receptor I (TbetaR1) siRNA duplexes. When TbetaR1 was knocked down, the TGF-beta3-induced increase in the kinetics of JAM-A and occludin endocytosis was abolished, making them indistinguishable from controls, illustrating the specificity of the TGF-beta3 effects on protein endocytosis. In summary, this report demonstrates for the first time that BTB dynamics are regulated by TGF-beta3 and TNFalpha via an enhancement of protein endocytosis at the BTB.

Potential regulatory relationship between the nested gene DDC8 and its host gene tissue inhibitor of metalloproteinase-2

Nested genes are fairly common within the mammalian nervous system, yet few studies have examined whether the guest and host genes might be coordinately regulated. Tissue inhibitors of metalloproteinase (TIMPs) inhibit extracellular matrix proteolysis mediated by metzincin proteases. TIMP-2 is the only TIMP not nested within a synapsin gene. It does, however, serve as a host for differential display clone 8 (DDC8), a testis-specific gene whose expression is upregulated during spermatogenesis. Here, we demonstrate that DDC8 is not testis specific. Furthermore, DDC8 expression in nonneural and neural tissues mimics that of TIMP-2, including its upregulation in response to traumatic brain injury, suggesting a potential regulatory relationship. The most striking observation is that the TIMP-2 knockout mouse brain contains TIMP-2 mRNA encoding exons 2-5, which are downstream of DDC8, but not exon 1, which contains the signal sequence and cysteine residue required for MMP inhibition, indicating a functional knockout. That TIMP-2 transcripts in wild-type brain contain DDC8 sequence suggests alternative splicing between the two genes.

Estradiol affects androgen-binding protein expression and fertilizing ability of spermatozoa in adult male rats

The estrogenicity of certain environmental pollutants is being increasingly correlated to decline in sperm counts and fertility of the males. Qualitative effects, if any, of estrogen(s) on terminal differentiation of spermatids have been less reported. The present study suggests that exposure to estrogen(s) can also alter the status of condensed chromatin in testicular spermatozoa and reduce their fertilizing potential. A significant reduction was evident in the serum gonadotropins, testosterone, weights of reproductive organs, sperm counts and litters sired by male rats after 10 days of estradiol exposure to a dose of 0.1mg/kg/day. Estradiol treatment led to retardation of in vitro decondensation rates of sperm chromatin, reduction in the uptake of acridine orange dye by chromatin, reduction in susceptibility of chromatin to acid denaturation in vitro, reduced uptake of thiol reactive monobromobimane dye and reduced levels of immunoreactive protamine 1 in caput epididymal sperms. Concomitantly, testicular levels of immunoreactive protamine 1, transition proteins 1/2 and cyclic adenosyl response element modulator-tau (CREMtau) were significantly reduced whilst their mRNA levels were unaffected after estradiol treatment. A significant increase was observed in the testicular mRNA levels of androgen-binding protein (ABP) in estradiol treated sires. An inverse correlation was observed between ABP mRNA levels and uptake of acridine orange by estradiol treated caput sperm chromatin. The results suggest that estradiol-induced increase in ABP mRNA underlies the mechanism(s) involved in the reduction in levels of certain proteins involved in nuclear chromatin condensation during spermiogenesis.

Laminin alpha 3 forms a complex with beta3 and gamma3 chains that serves as the ligand for alpha 6beta1-integrin at the apical ectoplasmic specialization in adult rat testes

Apical ectoplasmic specialization (ES) is a testis-specific hybrid cell/cell actin-based adherens junction and cell/matrix focal contact anchoring junction type restricted to the interface between Sertoli cells and developing spermatids. Recent studies have shown that laminin gamma3, restricted to elongating spermatids, is a putative binding partner of alpha 6beta 1-integrin localized in Sertoli cells at the apical ES. However, the identity of the alpha and beta chains, which constitute a functional laminin ligand with the gamma3 chain at the apical ES, is not known. Using reverse transcription-PCR and immunoblotting to survey all laminin chains in cells of the seminiferous epithelium, it was noted that alpha 2, alpha 3, beta1, beta2, beta3, and gamma3 chains were found in germ cells, whereas alpha 1, alpha 2, alpha 4, alpha 5, beta1, beta2, gamma1, gamma2, and gamma3 chains were found in Sertoli cells, implying that alpha 3 and beta3 are the plausible laminin chains restricted to germ cells that may be the bona fide partners of gamma3. To verify this postulate, recombinant proteins based on domain G of alpha 3 and domain I of beta3 and gamma3 chains were produced and used to obtain the corresponding specific polyclonal antibodies. Additional studies have demonstrated that the laminin alpha 3, beta3, and gamma3 chains indeed are restricted to germ cells at the apical ES, co-localizing with each other and with beta1-integrin. Furthermore, co-immunoprecipitation studies have confirmed the interactions among laminin alpha 3, beta3, and gamma3, as well as beta1-integrin. When the functional laminin ligand at the apical ES was disrupted via blocking antibodies, such as using anti-laminin alpha 3 or gamma3 IgG, this treatment perturbed adhesion between Sertoli and germ cells (mostly spermatids), leading to germ cell loss from the epithelium. More important, a transient disruption of the blood-testis barrier was also detected.

Induction of IL-1, in the Testes of Adult Mice, Following Subcutaneous Administration of Turpentine

PROBLEM

Interleukin-1 family is present in the testicular homogenates and its cellular compartments. It has been suggested that IL-1 is involved in physiological and pathological functions of the testicular tissues. In the present study we examined the effect of acute mostly localized inflammation, using turpentine, on the expression levels of testicular IL-1 system.

METHODS OF STUDY

Mice were subcutaneously injected with steam-distilled turpentine or saline (control). Three hours to 10 days following the injection, mice were killed and testis and spleen were homogenized and examined for interleukin (IL)-1alpha, IL-1beta, and IL-1 receptor antagonist (IL-1ra) levels by enzyme-linked immunosorbent assay and polymerase chain reaction.

RESULTS

Subcutaneous injection of turpentine induced mice systemic inflammation, as indicated by significant increase in serum IL-1beta levels, and IL-1alpha, IL-1beta and IL-1ra in spleen homogenates. The levels of IL-1alpha, IL-1beta and IL-1ra were significantly induced in testicular homogenates of adult mice following subcutaneous injection of turpentine. The significant induction of testicular IL-1alpha was detected after 3-24 hr of turpentine injection and decreased later (after 3-10 days) to levels similar to the control. However, significant induction of testicular IL-1beta was detected only after 3-10 days of turpentine injection, and for testicular IL-1ra levels was detected after 3 hr to 6 days of turpentine injection, and after 10 days the levels were similar to the control. These results were also confirmed by mRNA expression of these factors.

CONCLUSION

Our results demonstrate for the first time the distant effect of acute localized inflammation on testicular IL-1 levels. Thus, transient inflammatory response to infectious/inflammatory agents at non-testicular sites that elicit systemic IL-1 response should be considered during clinical treatment as a possible factor of male infertility.

Sertoli-germ cell anchoring junction dynamics in the testis are regulated by an interplay of lipid and protein kinases

When Sertoli and germ cells were co-cultured in vitro in serum-free chemically defined medium, functional anchoring junctions such as cell-cell intermediate filament-based desmosome-like junctions and cell-cell actin-based adherens junctions (e.g. ectoplasmic specialization (ES)) were formed within 1-2 days. This event was marked by the induction of several protein kinases such as phosphatidylinositol 3-kinase (PI3K), phosphorylated protein kinase B (PKB; also known as Akt), p21-activated kinase-2 (PAK-2), and their downstream effector (ERK) as well as an increase in PKB intrinsic activity. PI3K, phospho (p)-PKB, and PAK were co-localized to the site of apical ES in the seminiferous epithelium of the rat testis in immunohistochemistry studies. Furthermore, PI3K also co-localized with p-PKB to the same site in the epithelium as determined by fluorescence microscopy, consistent with their localization at the ES. These kinases were shown to associate with ES-associated proteins such as beta1-integrin, phosphorylated focal adhesion kinase, and c-Src by co-immunoprecipitation, suggesting that the integrin.laminin protein complex at the apical ES likely utilizes these protein kinases as regulatory proteins to modulate Sertoli-germ cell adherens junction dynamics via the ERK signaling pathway. To validate this hypothesis further, an in vivo model using AF-2364 (1-(2,4-dichlorobenzyl)-1H-indazole-3-carbohydrazide) to perturb Sertoli-germ cell anchoring junction function, inducing germ cell loss from the epithelium in adult rats, was used in conjunction with specific inhibitors. Interestingly, the event of germ cell loss induced by AF-2364 in vivo was also associated with induction of PI3K, p-PKB, PAK-2, and p-ERK as well as a surge in intrinsic PKB activity. Perhaps the most important of all, pretreatment of rats with wortmannin (a PI3K inhibitor) or anti-beta1-integrin antibody via intratesticular injection indeed delayed AF-2364-induced spermatid loss from the epithelium. In summary, these results illustrate that Sertoli-germ cell anchoring junction dynamics in the testis are regulated, at least in part, via the beta1-integrin/PI3K/PKB/ERK signaling pathway.

Effects of TCDD in modulating the expression of Sertoli cell secretory products and markers for cell–cell interaction

Among different mammalian tissues, testis is found to be one of the most sensitive organs to TCDD exposure. In this study, primary Sertoli cell culture was established. The purity of the cultured cells was verified using 3beta-hydroxysteroid dehydrogenase, alkaline phosphatase as well as testosterone induction assays. Effects of TCDD in modulating the expression of CYP1A1, aromatase, secretory products (i.e. Mullerian inhibiting substance (MIS), 17beta-estradiol (E(2)) and lactate) and markers for cell-cell interaction (i.e. sertolin and testin) were then examined. Our data demonstrated that Sertoli cells exposed to 0.2-2000 pg/ml of TCDD showed a dose dependent induction of CYP1A1 mRNA. The minimal dose of activation was 2 pg/ml, which indicated that the cell was very sensitive to TCDD exposure. However, there was little or no detectable level CYP1A1 protein and EROD activities found. Dose-dependent inductions of aromatase transcript (200%) and E(2) (20%) secretion were measured. In addition there was a significant reduction (40%) of MIS mRNA. No detectable change in the level of secreted lactate was observed. Sertolin and testin, the gene makers for cell-cell interactions were differentially modulated upon TCDD treatment. Taken together, the results implicated that TCDD exposure might interfere with the normal Sertoli cell functions.

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.

Interactions among IQGAP1, Cdc42, and the cadherin/catenin protein complex regulate Sertoli-germ cell adherens junction dynamics in the testis

The movement of developing germ cells across the seminiferous epithelium during spermatogenesis involves extensive adherens junction (AJ) restructuring between Sertoli cells, as well as between Sertoli and germ cells. In this report, we show that the intricate interactions between Cdc42 (a Rho family protein of Mr approximately 23 kDa originally identified in membranes of human platelets and placenta, and is the homolog of CDC42Sc, which is known to regulate of bud-site assembly in Saccharomyces cerevisiae) and its effector, IQ motif containing GTPase activating protein (IQGAP1, Mr approximately 189 kDa, it is also an actin-binding protein known to interact with Cdc42 and Rac1 GTPases), regulate Sertoli-germ cell, but not Sertoli-Sertoli cell, AJ dynamics. Using testis lysates for immunoprecipitation (IP), IQGAP1 was shown to associate with E-cadherin, N-cadherin, and beta-catenin (but not beta1-integrin and nectin-2), as well as with actin and vimentin (but not alpha-tubulin). Moreover, IQGAP1 was found to localize to the periphery of both Sertoli and germ cells in the seminiferous epithelium, at sites of cell-cell contacts. Using fluorescent microscopy with dual fluorescent probes, IQGAP1 was found to co-localize, at least in part, with N-cadherin in the seminiferous epithelium consistent with their localization at the basal and apical ES. Using Sertoli-germ cell cocultures, it was demonstrated that AJ assembly associated with a transient induction of Cdc42 and IQGAP1, which was not found when Sertoli cells were cultured alone. Lastly, a shift in the interactions of Cdc42, IQGAP1, beta-catenin, and N-cadherin was detected in Sertoli-germ cell cocultures using an Ca2+-induced AJ disruption model, which was used to examine AJ disassembly and its reassembly. In the presence of Ca2+, IQGAP1 bound preferentially to Cdc42 rather than to beta-catenin. However, when Ca2+ was depleted from cocultures using EGTA, a Ca2+ chelating agent, IQGAP1 lost its affinity for Cdc42 and became tightly associated with beta-catenin, destabilizing cadherin-mediated AJs between Sertoli and germ cells. Yet this shift of protein-protein interaction was not detected in Sertoli cells cultured alone. These results illustrate that the interactions among IQGAP1, Cdc42, and beta-catenin are crucial to the regulation of Sertoli-germ cell, but not Sertoli-Sertoli cell, AJ dynamics 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.

Fer kinase/FerT and adherens junction dynamics in the testis: an in vitro and in vivo study

Fer kinase is a 94-kDa cytoplasmic cell-cell actin-based adherens junction (AJ)-associated nonreceptor protein tyrosine kinase (PTK) found in multiple epithelia including the testis, whereas FerT kinase (51 kDa) is the truncated testis-specific form of Fer kinase, lacking the Fps/Fes/Fer/CIP4 (products of oncogenes identified in avian and feline sarcoma, encoding tyrosine protein kinases) and the three coiled-coil domains versus Fer kinase. Yet the role(s) of Fer kinase in AJ dynamics in the testis remains largely unexplored. We have used an in vitro model of AJ assembly with Sertoli-germ cell cocultures and an in vivo model of AJ disassembly in which adult rats were treated with 1-(2,4-dichlorobenzyl)-indazole-3-carbohydrazide (AF-2364) to study changes in the expression and/or localization of Fer kinase during AJ restructuring. Fer kinase/FerT was expressed by Sertoli and germ cells when cultured in vitro. Using an antibody prepared against a synthetic peptide, NH2-SAPQNCPEEIFTIMMKCWDYK-COOH, corresponding to residues 779-799 of Fer kinase in the rat, which failed to cross-react with FerT kinase, for immunohistochemistry, Fer kinase was detected in the seminiferous epithelium in virtually all stages of the epithelial cycle. At stages XIII-VI, Fer kinase was associated largely with round and elongating spermatids. At stages VII-VIII, Fer kinase associated almost exclusively with round spermatids with very weak staining associated with elongated spermatids. This stage-specific localization of Fer kinase in the epithelium was confirmed by using staged tubules for semiquantitative reverse transcription-polymerase chain reaction. Studies by immunoprecipitation revealed that Fer kinase associated with N-cadherin, gamma-catenin, p120ctn, c-Src (a putative PTK and the product of the transforming, sarcoma-inducing gene of Rous sarcoma virus), Rab 8 (a GTPase), actin, vimentin, but not E-cadherin, afadin, nectin-3, and integrin beta1, suggesting Fer kinase associates not only with the actin-based cell-cell AJ structures, such as the N-cadherin/catenin complex (but not the alpha6beta1 integrin/laminin and the afadin/nectin complex), but also with intermediate filament-based cell-cell desmosomes. An induction in Fer kinase expression was detected during Sertoli-germ cell AJ assembly in vitro but not during AF-2364-induced AJ disruption in vivo. Yet this AF-2364-induced Fer kinase plummeting associated with an induction in N-cadherin, beta-catenin, and p120ctn, particularly at the base of the seminiferous epithelium. In summary, Fer kinase structurally associates with the N-cadherin/catenin protein complex in the testis and can possibly be used to mediate signaling function via the cadherin/catenin protein complex.

Sertoli-germ cell adherens junction dynamics in the testis are regulated by RhoB GTPase via the ROCK/LIMK signaling pathway

During spermatogenesis, cell-cell actin-based adherens junctions (AJs), such as ectoplasmic specializations (ESs), between Sertoli and germ cells undergo extensive restructuring in the seminiferous epithelium to facilitate germ cell movement across the epithelium. Although the mechanism(s) that regulates AJ dynamics in the testis is virtually unknown, Rho GTPases have been implicated in the regulation of these events in other epithelia. Studies have shown that the in vitro assembly of the Sertoli-germ cell AJs but not of the Sertoli cell tight junctions (TJs) is associated with a transient but significant induction of RhoB. Immunohistochemistry has shown that the localization of RhoB in the seminiferous epithelium is stage specific, being lowest in stages VII-VIII prior to spermiation, and displays cell-specific association during the epithelial cycle. Throughout the cycle, RhoB was localized near the site of basal and apical ESs but was restricted to the periphery of the nuclei in elongating (but not elongated) spermatids, spermatocytes, and Sertoli cells. However, RhoB was not detected near the site of apical ESs at stages VII-VIII. Furthermore, disruption of AJs in Sertoli-germ cell cocultures either by hypotonic treatment or by treatment with 1-(2,4-dichlorobenzyl)-indazole-3-carbohydrazide (AF-2364) also induced RhoB expression. When adult rats were treated with AF-2364 to perturb Sertoli-germ cell AJs in vivo, a approximately 4-fold induction in RhoB in the testis, but not in kidney and brain, was detected within 1 h, at least approximately 1-4 days before germ cell loss from the epithelium could be detected by histological analysis. The signaling pathway(s) by which AF-2364 perturbed the Sertoli-germ cell AJs apparently began with an initial activation of integrin, which in turn activated RhoB, ROCK1, (Rho-associated protein kinase 1, also called ROKbeta), LIMK1 (LIM kinase 1, also called lin-11 isl-1 mec3 kinase 1), and cofilin but not p140mDia and profilin via phosphorylation. Immunoprecipitation and immunoblots revealed that the induction of LIMK1 was mediated via an increase in its phospho-Ser but not phospho-Tyr content. Furthermore, Y-27632 ([(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexane-carboxamide, 2HCl]), a specific ROCK inhibitor, could effectively delay the AF-2364-induced germ cell loss from the seminiferous epithelium in vivo, illustrating that the integrin/RhoB/ROCK/LIMK pathway indeed plays a crucial role in the regulation of Sertoli-germ cell AJ dynamics. The fact that the RhoB pathway in the kidney and brain was not activated suggests that AF-2364 exerts its effects primarily at the testis-specific ES multiprotein complex structures between Sertoli cells and spermatids. In summary, this report illustrates that Sertoli germ cell AJ dynamics are regulated, at least in part, via the integrin/ROCK/LIMK/cofilin signaling pathway.

Transforming growth factor beta3 regulates the dynamics of Sertoli cell tight junctions via the p38 mitogen-activated protein kinase pathway

Earlier studies have implicated the significance of transforming growth factor-beta3 (TGFbeta3) in the regulation of Sertoli cell tight junction (TJ) dynamics, possibly via its inhibitory effects on the expression of occludin, claudin-11, and zonula occludens-1 (ZO-1). Yet the mechanism by which TGFbeta3 regulates the Sertoli cell TJ-permeability barrier is not known. Using techniques of semiquantitative reverse transcription-PCR (RT-PCR), immunoblotting, immunohistochemistry, and inhibitors against different kinases coupled with physiological techniques to assess the Sertoli cell TJ barrier function, it was shown that this TGFbeta3-induced effect on Sertoli cell TJ dynamics is mediated via the p38 mitogen-activated protein (MAP) kinase pathway. First, the assembly of the Sertoli cell-TJ barrier was shown to be associated with a transient but significant decline in both the TGFbeta3 production and expression by Sertoli cells. Furthermore, addition of TGFbeta3 to Sertoli cell cultures during TJ assembly indeed perturbed the TJ barrier with an IC50 at approximately 9 pM. Second, the TGFbeta3-induced disruption of the TJ barrier was associated with a transient induction in MEKK2 but not the other upstream signaling molecules that mediate TGFbeta3 action, such as Smad2, Cdc42, Rac2, and N-Ras, suggesting this effect might be mediated via the p38 MAP kinase pathway. This postulate was confirmed by the observation that TGFbeta3 also induced the protein level of the activated and phosphorylated form of p38 MAP kinase at the time the TJ barrier was perturbed. Third, and perhaps the most important of all, this TGFbeta3-mediated inhibitory effect on the TJ barrier and the TGFbeta3-induced p-p38 MAP kinase production could be blocked by SB202190, a specific p38 MAP kinase inhibitor, but not U0126, a specific MEK1/2 kinase inhibitor. These results thus unequivocally demonstrate that TGFbeta3 utilizes the p38 MAP kinase pathway to regulate Sertoli cell TJ dynamics.

The interplay of collagen IV, tumor necrosis factor-alpha, gelatinase B (matrix metalloprotease-9), and tissue inhibitor of metalloproteases-1 in the basal lamina regulates Sertoli cell-tight junction dynamics in the rat testis

During spermatogenesis, preleptotene and leptotene spermatocytes must translocate across the blood-testis barrier formed by inter-Sertoli cell-tight junctions (TJs) from the basal compartment of the seminiferous epithelium adjacent to the basement membrane to the adluminal compartment at stages VIII-IX for further development. Because of the close proximity between extracellular matrix (ECM) that constitutes the basement membrane and the blood-testis barrier, we sought to investigate the role of ECM in Sertoli cell TJ dynamics. When Sertoli cells were cultured in vitro to initiate the assembly of the Sertoli cell TJ-permeability barrier, the presence of an anticollagen IV antibody indeed perturbed the barrier. Because ECM is known to maintain a pool of cytokines and TNFalpha has been shown to regulate TJ dynamics in other epithelia, we investigated whether TNFalpha can regulate Sertoli cell TJ function via its effects on collagen alpha3(IV) and other proteins that maintain the homeostasis of ECM. As expected, recombinant TNFalpha perturbed the Sertoli cell TJ-barrier assembly in vitro dose dependently. TNFalpha also inhibited the timely induction of occludin, which is known to associate with the Sertoli cell TJ-barrier assembly. Furthermore, TNFalpha induced the expression of Sertoli cell collagen alpha3(IV), gelatinase B (matrix metalloprotease-9, MMP-9) and tissue inhibitor of metalloproteases-1 but not gelatinase A (matrix metalloprotease-2), and promoted the activation of pro-MMP-9. These results thus suggest that the activated MMP-9 induced by TNFalpha is used to cleave the existing collagen network in the ECM, thereby perturbing the TJ-barrier. This in turn creates a negative feedback that causes TNFalpha to induce collagen alpha3(IV) and tissue inhibitor of metalloproteases-1 expression so as to replenish the collagen network in the disrupted TJ-barrier and limit the activity of MMP-9. Taken collectively, these observations strengthen the notion that ECM is involved in the regulation of junction dynamics in addition to its structural role in the testis.

Activating signal cointegrator 1 is highly expressed in murine testicular Leydig cells and enhances the ligand-dependent transactivation of androgen receptor

Activating signal cointegrator 1 (ASC-1) has been recently reported as a coactivator of some nuclear receptors. In the present study, we have analyzed the expression of ASC-1 in the mouse testis and investigated its capacity to modulate the transcriptional activity of androgen receptor (AR). We found that although ASC-1 mRNA was ubiquitously expressed at a low level in mouse tissues, a couple of testis-specific mRNAs were expressed in the adult testis. Cloning of one testis-specific variant revealed that the ubiquitous and testis-specific transcripts of ASC-1 share at least the same open reading frame. The expression of the testis-specific ASC-1 mRNAs was developmentally regulated, and the onset of their expression coincided with the initiation of spermatogenesis. In situ hybridization of mouse testis with ASC-1 antisense probe demonstrated predominant expression of ASC-1 in the interstitial Leydig cells that express AR. Moreover, yeast two-hybrid tests and glutathione S-transferase pull-down assays revealed that ASC-1 associates directly with AR and that the hinge domain of AR and a putative zinc-finger motif of ASC-1 are major determinants for their interaction. Transient transfection assays performed by expressing ASC-1 in combination with AR and an androgen-responsive reporter gene showed that ASC-1 moderately alters the induction of the reporter gene. Taken together, these results suggest that ASC-1 may function as an AR coregulator and have a role in testicular functions.

Gonadotropins, via cAMP, negatively regulate GATA-1 gene expression in testicular cells

We and others demonstrated that the mRNAs encoding GATA-binding proteins, GATA-1 and GATA-4, were detected in mouse and rat testis, and in isolated rat Sertoli cells and testicular tumor cell lines derived from Leydig and Sertoli cells. In this study, we investigated the possible effects of gonadotropins and cAMP on the expression of GATA-binding protein genes in testicular cells. Unexpectedly, FSH negatively regulated GATA-1 (but not GATA-4) mRNA in a dose-dependent manner in primary cultures of rat Sertoli cells isolated from 21-d-old animals. GATA-1 mRNA was also negatively regulated by cAMP in a dose- and time-dependent manner in MA-10, a mouse Leydig tumor cell line. When 0.3 mM cAMP was administered to MA-10 cell cultures for 4 h, more than 95% of the GATA-1 mRNA and protein was abolished. The reduction of GATA-1 mRNA by cAMP can be mimicked by treatment with forskolin, which elevates intracellular cAMP levels. The inhibitory effect of cAMP was specific to the GATA-1 gene, given that GATA-4 and alpha-tubulin mRNA levels were not changed by any of the cAMP treatments. Inhibin alpha-subunit mRNA, on the other hand, was evidently increased by cAMP treatment in both MA-10 and Sertoli cells. However, inhibin alpha-subunit mRNA levels were elevated at 60-90 min before the suppression of GATA-1 mRNA detected. The inhibitory effect of cAMP on GATA-1 mRNA and protein was shown to be specific to testicular cells. The GATA-1 mRNA expressed in MEL, a mouse erythroid leukemia cell line, was not affected by cAMP. The reduction of GATA-1 mRNA by cAMP can be prevented when a translational inhibitor, cycloheximide, is added. In summary, we demonstrated that gonadotropins via cAMP negatively regulate the mRNA and protein levels of GATA-1, but not GATA-4, in testicular cells. The inhibitory effect on GATA-1 gene expression was specific to testicular cells and was not observed in erythroid cells.

Cell Junction Dynamics in the Testis: Sertoli-Germ Cell Interactions and Male Contraceptive Development

Spermatogenesis is an intriguing but complicated biological process. However, many studies since the 1960s have focused either on the hormonal events of the hypothalamus-pituitary-testicular axis or morphological events that take place in the seminiferous epithelium. Recent advances in biochemistry, cell biology, and molecular biology have shifted attention to understanding some of the key events that regulate spermatogenesis, such as germ cell apoptosis, cell cycle regulation, Sertoli-germ cell communication, and junction dynamics. In this review, we discuss the physiology and biology of junction dynamics in the testis, in particular how these events affect interactions of Sertoli and germ cells in the seminiferous epithelium behind the blood-testis barrier. We also discuss how these events regulate the opening and closing of the blood-testis barrier to permit the timely passage of preleptotene and leptotene spermatocytes across the blood-testis barrier. This is physiologically important since developing germ cells must translocate across the blood-testis barrier as well as traverse the seminiferous epithelium during their development. We also discuss several available in vitro and in vivo models that can be used to study Sertoli-germ cell anchoring junctions and Sertoli-Sertoli tight junctions. An in-depth survey in this subject has also identified several potential targets to be tackled to perturb spermatogenesis, which will likely lead to the development of novel male contraceptives.

A 22-amino acid synthetic peptide corresponding to the second extracellular loop of rat occludin perturbs the blood-testis barrier and disrupts spermatogenesis reversibly in vivo

When Sertoli cells were cultured in vitro on Matrigel-coated bicameral units, the assembly of the inter-Sertoli tight junction (TJ) permeability barrier correlated with an induction of occludin expression. Inclusion of a 22-amino acid peptide, NH(2)-GSQIYTICSQFYTPGGTGLYVD-COOH, corresponding to residues 209-230 in the second extracellular loop of rat occludin, at 0.2-4 microM into Sertoli cell cultures could perturb the assembly of Sertoli TJs dose-dependently and reversibly. This peptide apparently exerts its effects by interfering with the homotypic interactions of two occludin molecules between adjacent Sertoli cells at the sites of TJs, thereby disrupting TJs, which, in turn, causes a decline in transepithelial electrical resistance across the Sertoli cell epithelium. When similar experiments were performed using a 22-amino acid myotubularin peptide, NH(2)-TKVNERYELCDTYPALLAVPAN-COOH (residues 156-177), no effects on the assembly of inter-Sertoli TJs in vitro were noted. When a single dose of this synthetic occludin peptide was administered to adult rats intratesticularly at 1.5-10 mg/testis, germ cells began to deplete from the seminiferous epithelium within 8-16 days. By 27 days, virtually all tubules were devoid of germ cells. This antispermatogenic effect was reversible, because germ cells progressively repopulated the epithelium thereafter. Treated testes were indistinguishable from normal or control testes by 68 days post-occludin peptide treatment when assessed using histological analysis. In contrast, control rats receiving either no treatment, vehicle alone, or a 22-amino acid synthetic peptide of myotubularin displayed no changes in the testicular morphology at all time points. The occludin peptide-induced germ cell depletion was also accompanied by a disruption of the blood-testis barrier (BTB) when assessed by micropuncture techniques quantifying [(125)I]-BSA in rete testis fluid and seminiferous tubular fluid following i.v. administration of [(125)I]-BSA through the jugular vein. These results illustrate that the occludin peptide-induced disruption of the BTB may possibly affect the underlying adherens junctions, which causes premature release of germ cells from the epithelium and reversible infertility.

Partial amino acid sequencing of 80-kDa human sperm antigen (80-kDa HSA)

An 80-kDa human sperm antigen (80-kDa HSA) has been identified as a sperm protein responsible for inducing immunoinfertility. Immunization with the purified protein induced infertility in male and female rats. Immunohistochemical and immunofluorescent studies have demonstrated that the antigen is specific to spermatozoa. The present study describes the partial amino acid sequencing of 80-kDa HSA. The homogeneous protein was electrophoretically transferred onto a PVDF membrane and the excised band of 80-kDa HSA was used to determine the partial N-terminal amino acid sequence. The protein was then subjected to enzymatic digestion with endoproteinase Lys-C and endoproteinase Glu-C. The partial amino acid sequence of the major peptides thus obtained was determined. The digestion with endoproteinase Lys-C generated 4 major peptides, two of which showed partial sequence homology with lactoferrin. Endoproteinase Glu-C digestion produced 3 major peptides. The sequences of the 2 peptides were determined for which no matches were found in the databank. These results confirmed earlier observations that 80-kDa HSA is a sperm-specific protein that is chemically distinct from any other protein involved in normal physiological process. Earlier studies have demonstrated that it is antigenic, efficacious, conserved, and could be a promising candidate for the development of an antifertility vaccine.

Two new male contraceptives exert their effects by depleting germ cells prematurely from the testis

The three currently available male contraceptive approaches are 1) the barrier method such as the condom, 2) hormonal methods by disrupting the pituitary-testicular axis so as to impair spermatogenesis, and 3) immunological methods by preparing vaccines against male-specific antigens. We hereby describe an alternative approach in which attachments of developing germ cells onto the seminiferous epithelium are disrupted, thereby inducing their premature release into the tubular lumen. This in turn leads to infertility. A panel of analogues based on the core structure of 1-(2,4-dichlorobenzyl)-indazole-3-carboxylic acid was synthesized. These compounds were subjected to an in vivo screening assay assessing their effects in inducing the expression of testin, a testicular marker whose expression correlates with the integrity of Sertoli-germ cell junctions. An induction of testin expression in the testis signifies a disruption of Sertoli-germ cell junctions that is followed by depletion of germ cells from the seminiferous epithelium. Two compounds, namely 1-(2,4-dichlorobenzyl)-indazole-3-carbohydrazide (AF-2364) and 1-(2,4-dichlorobenzyl)-indazole-3-acrylic acid (AF-2785), were identified that caused detachment of germ cells, in particular round and elongated spermatids, from the epithelium inducing their premature release into the tubular lumen as confirmed by histological analysis. Adult rats receiving several oral doses of either one of these compounds became infertile within 3-7 wk after the epididymal sperm reserve was exhausted. Depending on the dosing of the administered compound, rats became infertile for 4-14 wk before their fertility gradually bounced back, illustrating the reversibility and efficacy of these new compounds. Also, these compounds did not appear to impair the hypothalamus-pituitary-testicular axis because the serum levels of LH, FSH, and testosterone of the treated animals did not change significantly when compared to control rats. In addition, results of serum microchemistry illustrate that liver and kidney function was not affected in animals treated with both compounds.

Is cadmium chloride-induced inter-sertoli tight junction permeability barrier disruption a suitable in vitro model to study the events of junction disassembly during spermatogenesis in the rat testis?

The events of germ cell movement during spermatogenesis are composed of intermittent phases of junction disassembly and reassembly. Although primary Sertoli cells cultured in vitro can be used to study junction reassembly, an in vitro model to study the events of junction disassembly is still lacking. We have assessed whether the CdCl(2)-induced inter-Sertoli tight junction (TJ) permeability barrier disruption in vitro can fill this gap. When Sertoli cells (1.2 x 10(6) cells/cm(2)) were cultured on Matrigel-coated bicameral units to allow the assembly of inter-Sertoli TJs, it was manifested by a steady rise in transepithelial electrical resistance across the Sertoli cell epithelia. Exposure of these cells on day 1 (i.e. 24 h after their isolation) to CdCl(2) at 5-10 microM for 8 h could perturb the inter-Sertoli TJ assembly dose dependently without any apparent cytotoxicity. Likewise, when cells were exposed to CdCl(2) (0.1-5 microM) on day 4 for 8 h after inter-Sertoli TJs were already assembled, CdCl(2) also perturbed the maintenance of inter-Sertoli TJ permeability barrier dose dependently without signs of cell cytotoxicity. Although the perturbed inter-Sertoli TJs were not capable of resealing even after the removal of CdCl(2), the presence of testosterone (T) at 1 x 10(-9) M allowed resealing of the inter-Sertoli TJ barrier after CdCl(2) was removed, whereas the presence of 2 x 10(-7) M testosterone even protected Sertoli cells from CdCl(2)-induced damage. More important, the reassembly of inter-Sertoli TJs after CdCl(2)-induced TJ disruption was accompanied by changes in cellular gene expression of occludin and urokinase plasminogen activator, which mimicked their patterns during inter- Sertoli TJ assembly in vitro without CdCl(2) treatment. Based on these results, it is apparent that CdCl(2)-induced inter-Sertoli TJ disassembly is a potential in vitro model to study the events of junction disassembly.

Rat testicular myotubularin, a protein tyrosine phosphatase expressed by Sertoli and germ cells, is a potential marker for studying cell-cell interactions in the rat testis

The full-length cDNA encoding the entire open reading frame (ORF) of rat myotubularin (rMTM) was isolated from a rat testis expression library by PCR. Among the three approximately 2.9-kb cDNAs that were sequenced, one clone was different from the other two clones. It contained seven extra amino acids of FVVLNLQ; this short stretch of extra sequence was found between Gln(421) and Phe(422) within the SET (Suvar3-9, Enhancer-of-zeste, Trithorax) interacting domain (SID) of rMTM. The rMTM ORF had 1,713 bp encoding for a 571 amino acid polypeptide and a calculated molecular weight of 65.8 kDa. A comparison between its deduced amino acid sequence and the GenBank database using BLAST revealed a 53.1% identity with human myotubularin protein (hMTM1), which is a member of the protein tyrosine phosphatase (PTP) family associated with X-linked myotubular myopathy. A 22 amino acid peptide NH(2)-TKVNERYELCDTYPALLAVPAN was synthesized based on the deduced amino acid sequence of rMTM and used for antibody production. By using immunoblot analysis, a 66-kDa protein was indeed detected in both Sertoli and germ-cell cytosols. rMTM mRNA was found in various tissues but was predominantly expressed in the testis, ovary, and skeletal muscle. Sertoli cell rMTM expression was stimulated by germ cells and enhanced when inter-Sertoli junctions were being assembled in vitro. A drastic reduction in testicular rMTM steady-state mRNA level correlated with the depletion of germ cells from the testis in vivo following either glycerol or lonidamine treatment. These results indicate that rMTM is a rat homologue of hMTM1 that may be a useful marker in monitoring the events of cell-cell interactions in the testis.

Spermiogenesis in commercial poultry species: anatomy and control

Spermatogenesis is a complicated process dependent upon several factors. Formation of a testis requires the interaction of gene-products and hormones (androgens) on pluripotent tissue. In birds, the female is the heterogametic (ZW) sex, but W chromosomal genes do not influence gonadal development in a way similar to the SRY gene on the mammalian Y chromosome. However, autosomal genes such as SRY-like HMG box gene 9 (SOX9) may influence gonadal development. Hormones affect development; male gonads subjected to estrogen form an ovotestis, whereas ovaries exposed to aromatase inhibitors form an atypical testis. Sertoli cell numbers are set early in spermiogenesis, possibly under the influence of follicle-stimulating hormone and thyroid hormone, and this may determine the number of gonial cells that can be supported. Sertoli cells make a number of substances that affect testicular development and function, particularly anti-Müllerian hormone, which inhibits female oviduct formation from the Müllerian anlage, inhibits aromatase activity to stop estrogen production, and possibly stimulates androgen production by Leydig cells. Undifferentiated primordial germ cells (PGC) migrate to the testis and are converted to spermatogonia by factors from gonadal ridge tissue and androgens. The PGC of males in the ovary form oocytes of Z genotype, whereas the female PGC in males form mostly Z sperm (with a few of W genotype). Transmission electron microscopy micrographs of turkey testis are presented, and control of spermatogenesis by hormones and cytokines is discussed. This discussion includes follicle-stimulating hormone, luteinizing hormone, inhibin, activin, follistatin, tumor necrosis factor-alpha, growth factors such as transforming growth factor-beta, interleukins, and interferon. Although information concerning paracrine and autocrine regulation of the avian testis by these substances is sparse, much can be learned from mammalian studies, in which putative roles of each of these substances have been established. How Sertoli cells cause directed apoptosis of spermatogonia using the Fas-ligand, Fas-receptor pathway is reviewed, as well as ways to circumvent this process. A possible role for ubiquitin concerning prevention of heat-induced damage to the testis is presented.

Effects of lonidamine on testicular and epididymal proteins in the rat

The mechanism responsible for the antispermatogenic activity of lonidamine (LND) [1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxylic acid], a drug with low systemic toxicity and lack of significant hormonal effects, is still unclear but may be related to alterations of Sertoli cell proteins. Here, we confirmed that a single oral dose of LND (100 mg/kg b.w.) to sexually mature Sprague-Dawley rats causes shrinkage and weight reduction of the testes after 48 h. These macroscopic changes correlated with histologic alterations revealed by light microscopy, consistent with partially reversible inhibition of spermatogenesis. When the testes and the epididymides of animals treated with or without LND were homogenized and analyzed by the Bradford assay, a significant increase of total protein content was observed after 24 and 48 h. When these homogenates were analyzed by concanavalin blotting, specific changes of the major rat macroglobulins, i.e. alpha(1)-inhibitor-3, alpha(2)-macroglobulin, and alpha(1)-macroglobulin, were noted. In particular, LND caused a decrease of testicular alpha(1)-inhibitor-3, but not an increase of testicular alpha(2)-macroglobulin, indicating a mild local inflammatory response to the drug.