Specific surface antigens on rat pachytene spermatocytes and successive classes of germinal cells

Neonatal Pig Sertoli Cells Survive Xenotransplantation by Creating an Immune Modulatory Environment Involving CD4 and CD8 Regulatory T Cells

The acute cell-mediated immune response presents a significant barrier to xenotransplantation. Immune-privileged Sertoli cells (SC) can prolong the survival of co-transplanted cells including xenogeneic islets, hepatocytes, and neurons by protecting them from immune rejection. Additionally, SC survive as allo- and xenografts without the use of any immunosuppressive drugs suggesting elucidating the survival mechanism(s) of SC could be used to improve survival of xenografts. In this study, the survival and immune response generated toward neonatal pig SC (NPSC) or neonatal pig islets (NPI), nonimmune-privileged controls, was compared after xenotransplantation into naïve Lewis rats without immune suppression. The NPSC survived throughout the study, while NPI were rejected within 9 days. Analysis of the grafts revealed that macrophages and T cells were the main immune cells infiltrating the NPSC and NPI grafts. Further characterization of the T cells within the grafts indicated that the NPSC grafts contained significantly more cluster of differentiation 4 (CD4) and cluster of differentiation 8 (CD8) regulatory T cells (Tregs) at early time points than the NPI grafts. Additionally, the presence of increased amounts of interleukin 10 (IL-10) and transforming growth factor (TGF) β and decreased levels of tumor necrosis factor (TNF) α and apoptosis in the NPSC grafts compared to NPI grafts suggests the presence of regulatory immune cells in the NPSC grafts. The NPSC expressed several immunoregulatory factors such as TGFβ, thrombospondin-1 (THBS1), indoleamine-pyrrole 2,3-dioxygenase, and galectin-1, which could promote the recruitment of these regulatory immune cells to the NPSC grafts. In contrast, NPI grafts had fewer Tregs and increased apoptosis and inflammation (increased TNFα, decreased IL-10 and TGFβ) suggestive of cytotoxic immune cells that contribute to their early rejection. Collectively, our data suggest that a regulatory graft environment with regulatory immune cells including CD4 and CD8 Tregs in NPSC grafts could be attributed to the prolonged survival of the NPSC xenografts.

The Good, the Bad and the Ugly of Testicular Immune Regulation: A Delicate Balance Between Immune Function and Immune Privilege

The testis is one of several immune privilege sites. These sites are necessary to decrease inflammation and immune responses that could be damaging to the host. For example, inflammation in the brain, eye or placenta could result in loss of cognitive function, vision or rejection of the semi-allogeneic fetus, respectively. In the testis, immune privilege is "good" as it is necessary for protection of the developing auto-immunogenic germ cells. However, there is also a downside or "bad" part of immune privilege, where pathogens and cancers can take advantage of this privilege and persist in the testis as a sanctuary site. Even worse, the "ugly" of privilege is how re-emerging viruses, such as Ebola and Zika viruses, can establish persistence in the testes and be sexually transmitted even months after they have been cleared from the bloodstream. In this review, we will discuss the delicate balance within the testis that provides immune privilege to protect the germ cells while still allowing for immune function to fight off pathogens and tumors.

The Sertoli cell: what can we learn from different vertebrate models?

Besides having medical applications, comparative studies on reproductive biology are very useful, providing, for instance, essential knowledge for basic, conservation and biotechnological research. In order to maintain the reproductive potential and the survival of all vertebrate species, both sperm and steroid production need to occur inside the testis. From the approximately fifty thousand vertebrate species still alive, very few species are already investigated; however, our knowledge regarding Sertoli cell biology is quite good. In this regard, it is already known that since testis differentiation the Sertoli cells are the somatic cells in charge of supporting and orchestrating germ cells during development and full spermatogenesis in adult animals. In the present review, we highlight key aspects related to Sertoli cell biology in vertebrates and show that this key testis somatic cell presents huge and intrinsic plasticity, particularly when cystic (fish and amphibians) and non-cystic (reptiles, birds and mammals) spermatogenesis is compared. In particular, we briefly discuss the main aspects related to Sertoli cells functions, interactions with germ cells, Sertoli cells proliferation and efficiency, as well as those regarding spermatogonial stem cell niche regulation, which are crucial aspects responsible for the magnitude of sperm production. Most importantly, we show that we could greatly benefit from investigations using different vertebrate experimental models, mainly now that there is a big concern regarding the decline in human sperm counts caused by a multitude of factors.

Characterization of inter-Sertoli cell tight and gap junctions in the testis of turtle: Protect the developing germ cells from an immune response

It is conceivable that early developing germ cells must across the basal to the luminal region of seminiferous tubules (STs) during spermatogenesis is associated with extensive restructuring of junctional complex. However, very limited information is documented about these junctional complexes in reptiles. In the present study we have determined the localization of inter-Sertoli cell tight junctions (TJ's), protein CLDN11 and gap junction protein Cx43 during spermatogenesis in the testis. In early spermatogenesis, weak immunoreactivity of CLDN11and focal localization of Cx43 was observed around the Sertoli cell in the luminal region, but completely delaminated from the basal compartment of STs. In late spermatogenesis, strong focal to linear localization of CLDN11and Cx43 was detected at the points of contact between two Sertoli cells and around the early stages of primary spermatocytes in the basal compartment of STs. In late spermatogenesis, localization of CLDN11and Cx43 was drastically reduced and seen only around Sertoli cells and spermatogonia near the basal lamina. However, transmission electron microscopy revealed that inter-Sertoli cell tight junctions were present within the basal compartment of STs, leaving the spermatogonia and early primary spermatocytes in the basal region during mid spermatogenesis. Gap junctions were observed between Sertoli cells, and Sertoli cells with spermatogonia and primary spermatocytes throughout spermatogenesis. Moreover, adherens and hemidesmosomes junctions were observed during spermatogenesis. The above findings collectively suggest that the intensity and localization of TJ's and gap junctions vary according to the spermatogenetic stages that might be protected the developing germ cells from own immune response.

An overview of a Sertoli cell transplantation model to study testis morphogenesis and the role of the Sertoli cells in immune privilege

Advanced testicular germ cells, expressing novel cell surface and intracellular proteins, appear after the establishment of central tolerance and thus are auto-immunogenic. However, due to testis immune privilege these germ cells normally do not evoke a detrimental immune response. The Sertoli cell (SC) barrier (also known as the blood-testis barrier) creates a unique microenvironment required for the completion of spermatogenesis and sequesters the majority of the advanced germ cells from the immune system. Given that an intact SC barrier is necessary for spermatogenesis and that disruption of the SC barrier results in loss of advanced germ cells independent of an immune response, this dual role of the SC barrier makes it difficult to directly test the importance of the SC barrier in immune privilege. The ability of SCs to survive and protect co-grafted cells when transplanted ectopically (outside the testis) across immunological barriers is well-documented. Here, we will discuss the use of a SC transplantation model to investigate the role of SC and the SC barrier in immune privilege. Additionally, the formation of cord/tubule like structures in this model, containing both SCs and myoid cells, further extends its application to study testis morphogenesis. We will also discuss the potential use of this model to study the effects of drugs/environmental toxins on testis morphogenesis, tight junction formation and SC-myoid cell interactions.

Transgenic Sertoli Cells as a Vehicle for Gene Therapy

Gene therapy involves the manipulation of genetic material to replace defective or deficient proteins to restore function in disease states. These genes are introduced into cells by mechanical, chemical, and biological approaches. To date, cell-based gene therapy has been hampered by the lack of an abundant, safe, and immunologically acceptable source of tissue. As an alternative, transgenic animals designed to produce therapeutic proteins could overcome some of the issues facing gene therapy but the problem of immune rejection of the tissue remains. This article reports on recently published work indicating the potential to use transgenic Sertoli cells surviving in an allogeneic host by virtue of their ability to create a locally immunoprivileged environment, thereby providing for the continued delivery of a therapeutic protein to the systemic circulation.

The Sertoli cell: one hundred fifty years of beauty and plasticity

It has been one and a half centuries since Enrico Sertoli published the seminal discovery of the testicular 'nurse cell', not only a key cell in the testis, but indeed one of the most amazing cells in the vertebrate body. In this review, we begin by examining the three phases of morphological research that have occurred in the study of Sertoli cells, because microscopic anatomy was essentially the only scientific discipline available for about the first 75 years after the discovery. Biochemistry and molecular biology then changed all of biological sciences, including our understanding of the functions of Sertoli cells. Immunology and stem cell biology were not even topics of science in 1865, but they have now become major issues in our appreciation of Sertoli cell's role in spermatogenesis. We end with the universal importance and plasticity of function by comparing Sertoli cells in fish, amphibians, and mammals. In these various classes of vertebrates, Sertoli cells have quite different modes of proliferation and epithelial maintenance, cystic vs. tubular formation, yet accomplish essentially the same function but in strikingly different ways.

Genetically engineered immune privileged Sertoli cells: A new road to cell based gene therapy

Sertoli cells are immune privileged cells, important for controlling the immune response to male germ cells as well as maintaining the tolerogenic environment in the testis. Additionally, ectopic Sertoli cells have been shown to survive and protect co-grafted cells when transplanted across immunological barriers. The survival of ectopic Sertoli cells has led to the idea that they could be used in cell based gene therapy. In this review, we provide a brief overview of testis immune privilege and Sertoli cell transplantation, factors contributing to Sertoli cell immune privilege, the challenges faced by viral vector gene therapy, the use of immune privileged cells in cell based gene therapy and describe several recent studies on the use of genetically engineered Sertoli cells to provide continuous delivery of therapeutic proteins.

Sertoli cells--immunological sentinels of spermatogenesis

Testicular germ cells, which appear after the establishment of central tolerance, express novel cell surface and intracellular proteins that can be recognized as 'foreign antigens' by the host's immune system. However, normally these germ cells do not evoke an auto-reactive immune response. The focus of this manuscript is to review the evidence that the blood-testis-barrier (BTB)/Sertoli cell (SC) barrier along with the SCs ability to modulate the immune response is vital for protecting auto-antigenic germ cells. In normal testis, the BTB/SC barrier protects the majority of the auto-antigenic germ cells by limiting access by the immune system and sequestering these 'new antigens'. SCs also modulate testis immune cells (induce regulatory immune cells) by expressing several immunoregulatory factors, thereby creating a local tolerogenic environment optimal for survival of nonsequesetred auto-antigenic germ cells. Collectively, the fortress created by the BTB/SC barrier along with modulation of the immune response is pivotal for completion of spermatogenesis and species survival.

Differential permeability of the blood-testis barrier during reinitiation of spermatogenesis in adult male rats

The blood-testis barrier (BTB) sequesters meiotic spermatocytes and differentiating spermatids away from the vascular environment. We aimed to assess whether meiosis and postmeiotic differentiation could occur when the BTB is permeable. Using a model of meiotic suppression and reinitiation, BTB function was assessed using permeability tracers of small, medium, and large (0.6-, 70-, and 150-kDa) sizes to emulate blood- and lymphatic-borne factors that could cross the BTB. Adult rats (n = 9/group) received the GnRH antagonist acyline (10 wk) to suppress gonadotropins, followed by testosterone (24cm Silastic implant), for 2, 4, 7, 10, 15, and 35 days. In acyline-suppressed testes, all tracers permeated the seminiferous epithelium. As spermatocytes up to diplotene stage XIII reappeared, both the 0.6- and 70-kDa tracers, but not 150 kDa, permeated around these cells. Intriguingly, the 0.6- and 70-kDa tracers were excluded from pachytene spermatocytes at stages VII and VIII but not in subsequent stages. The BTB became progressively impermeable to the 0.6- and 70-kDa tracers as stages IV-VII round spermatids reappeared in the epithelium. This coincided with the appearance of the tight junction protein, claudin-12, in Sertoli cells and at the BTB. We conclude that meiosis can occur when the BTB is permeable to factors up to 70 kDa during the reinitiation of spermatogenesis. Moreover, BTB closure corresponds with the presence of particular pachytene spermatocytes and round spermatids. This research has implications for understanding the effects of BTB dynamics in normal spermatogenesis and also potentially in states where spermatogenesis is suppressed, such as male hormonal contraception or infertility.

The immune privilege of testis and gravid uterus: same difference?

The fetus in the gravid uterus and the developing spermatogenic cells in the adult testis both comprise special challenges for the host immune system. Protection of the neoantigens of the fetus and male germ cells from immune attack, defined as immune privilege, is fundamental for the propagation of species. Immune privilege is not simply the absence of leukocytes, but involves immune and non-immune cells acting synergistically together at multiple levels to create a unique tolerogenic environment. A number of the pathways are shared by the testis and gravid uterus. Amongst them steroid hormones, namely testosterone in the male and progesterone in the female, seem to function as key molecules that govern the local production of immunoregulatory factors which finally control the overall immune environment.

Stromal cell-based immunotherapy in transplantation

Organs are composed of parenchymal cells that characterize organ function and nonparenchymal cells that are composed of cells in transit, as well as tissue connective tissue, also referred to as tissue stromal cells. It was originally thought that these tissue stromal cells provided only structural and functional support for parenchymal cells and were relatively inert. However, we have come to realize that tissue stromal cells, not restricted to in the thymus and lymphoid organs, also play an active role in modulating the immune system and its response to antigens. The recognition of these elements and the elucidation of their mechanisms of action have provided valuable insight into peripheral immune regulation. Extrapolation of these principles may allow us to utilize their potential for clinical application. In this article, we will summarize a number of tissue stromal elements/cell types that have been shown to induce hyporesponsiveness to transplants. We will also discuss the mechanisms by which these stromal cells create a tolerogenic environment, which in turn results in long-term allograft survival.

Immunoprotective Sertoli cells: making allogeneic and xenogeneic transplantation feasible

The testis as an immune-privileged site allows long-term survival of allogeneic and xenogeneic transplants. Testicular Sertoli cells (SCs) play a major role in this immunoprotection and have been used to create an ectopic immune-privileged environment that prolongs survival of co-transplanted allogeneic and xenogeneic cells, including pancreatic islets and neurons. Extended survival of such grafts testifies to the immunoprotective properties of SCs. However, there is still variability in the survival rates of the co-grafted cells and rarely are 100% of the grafts protected. This emphasizes the need to learn more about what is involved in creating the optimal immunoprotective milieu. Several parameters including organization of the SCs into tubule-like structures and the production of immunomodulatory factors by SCs, specifically complement inhibitors, cytokines, and cytotoxic lymphocyte inhibitors, are likely important. In addition, an intricate interplay between several of these factors may be responsible for providing the most ideal environment for protection of the co-transplants by SCs. In this review, we will also briefly describe a novel use for the immune-privileged abilities of SCs; engineering them to deliver therapeutic proteins for the treatment of diseases like diabetes and Parkinson's disease. In conclusion, further studies and more detailed analysis of the mechanisms involved in creating the immune-protective environment by SCs may make their application in co-transplantation and as engineered cells clinically feasible.

Polyamines in spermatocytes and residual bodies of rat testis

Immunocytochemistry for polyamines in the rat testis revealed intense staining of small bodies close to the lumen of seminiferous tubules of spermatogenic stage VII and VIII as well as of spermatocytes. Methyl green-pyronin and propidium iodide staining combined with DNase or RNase predigestion showed that the small bodies contained RNA, but not DNA and double fluorescence staining showed that polyamines (PAs) colocalized with RNA in the bodies. Electron microscopy confirmed the absence of nuclei in the bodies and revealed that PA immunoreactivity was associated with ribosomes. These results strongly suggest that the small bodies correspond to the residual bodies, and agree with previous results showing localization of PAs to ribosomes in neurons and gastrointestinal epithelial cells. The accumulation of PAs in residual bodies may reflect a termination of their role in spermiogenesis with respect to protein synthesis.

Neonatal Porcine Sertoli Cells Inhibit Human Natural Antibody-Mediated Lysis1

Sertoli cells protect cotransplanted cells from allogeneic and xenogeneic rejection. Additionally, neonatal porcine Sertoli cells (NPSCs) survive long-term as xenografts in nonimmunosuppressed rodents. This has led to the hypothesis that NPSCs could be used to prevent cellular rejection in clinical transplantation, thereby eliminating the need for chronic immunosuppression. Prior to transplantation of NPSCs in humans it is necessary to determine whether they are also protected from humoral-mediated xenograft rejection. The presence of Gal alpha(1,3)Gal beta(1,4)GlcNAc-R (alphaGal epitope) as well as binding of human immunoglobulin G (IgG) and IgM to NPSCs was examined by immunocytochemical and fluorescence-activated cell sorter analysis. alphaGal was detected on 88.5% +/- 3.0% of NPSCs. Consistent with this, 71.7% +/- 1.0% and 65.4% +/- 5.2% of NPSCs were bound by IgG and IgM, respectively. When cultured NPSCs underwent an in vitro cytotoxicity assay by incubation with human AB serum plus complement, no increase in cellular lysis was observed, while controls--porcine aorta endothelial cells--were shown to contain > 60% dead cells. Finally, activation of the complement cascade was examined by immunohistochemistry. C3 and C4 were deposited on the surface of the NPSC membrane, indicating activation of complement. Although the complement cascade was activated, the membrane attack complex (MAC) was not formed. These data demonstrate that despite expression of alphaGal, binding of xenoreactive antibodies, and the activation of complement, NPSCs survive human antibody and complement-mediated lysis by preventing MAC formation. This suggests that NPSCs may be able to survive humoral-mediated rejection in a clinical situation.

SPAG11/isoform HE2C, an atypical anionic beta-defensin-like peptide

A human caput epididymidal cDNA, HE2C, was cloned based on its homology to the known chimpanzee counterpart, suggesting that the encoded beta-defensin-like peptide represented a conserved component of the innate epididymidal epithelial defense system in primates. An approximately 6kDa HE2- related peptide was co-purified together with other HE2 isoforms from human seminal plasma by affinity chromatography. By its antibody reactivity as shown by Western blot analysis, this peptide was distinct from the more abundant HE2 isoforms and was concluded to correspond to HE2C. Similar to other HE2-encoded isoforms, the endogenous HE2C was proteolytically processed from a larger precursor by a furin-like prohormone convertase. This was confirmed by N-terminal sequencing. In order to study the structural and functional properties of HE2C it was recombinantly expressed in insect cells. Post-translational processing also occurred within these cells, yielding the mature processed HE2C peptide. Correct disulfide bonding of the recHE2C peptide was shown by p-aminophenylarsineoxide(PAPAO)-agarose binding assay. Purified recHE2C strongly bound to Escherichia coli DH5alpha and Bacillus subtilis; however, it did not exhibit microbicidal activity when tested in a radial diffusion assay against these bacteria. Different from the previously described beta-defensins, the mature HE2C peptide has an anionic pI and an algebraic net charge of -1. Also, it lacks the amphipathic transitions, which, according to the Shai-Matzusaki-Huang model, are prerequisite for the membranolytic activity of antimicrobial peptides.

Trypanosomiasis-induced infertility in dromedary (Camelus dromedarius) bulls: changes in plasma steroids concentration and semen characteristics

The effect of Trypanosomiasis on concentrations of plasma steroids and semen characteristics was studied in 24 dromedary bulls. Based upon the parasitological and serological diagnosis, 18 bulls were found infected with Trypanosoma evansi (Group 2) and six were found to be free from infection and served as controls (Group 1). The infected animals exhibited signs of anaemia indicated by the decrease of packed cell volume (PCV) and haemoglobin concentration (Hb), pale mucus membranes, weight loss, lethargy, weakness and dullness. However, five animals (27.8%) of the infected group revealed elevated rectal temperatures and three animals (16.7%) revealed testicular degeneration upon palpation of their scrotal contents. Concentrations of plasma oestradiol-17beta (86.5 +/- 8.6 pg/ml versus 232.5 +/- 74.4 pg/ml) and testosterone (4.8 +/- 0.7 ng/ml versus 2.7 +/- 1.5 ng/ml) were significantly different (P < 0.05) between the control and infected bulls. Evaluation of the semen collected by electroejaculation and evaluated by a computerized cell motion analyzer revealed normal semen characteristics in the control animals compared to deteriorated ones in the infected bulls. There were highly significant (P < 0.01) decreases in sperm count (12.2 +/- 1.3/ml versus 6.5 +/- 4.9 x 10(6)/ml), motility percentage (68.2 +/- 6.7% versus 27.4 +/-15.6%), percentage of live spermatozoa (73.2 +/- 8.3% versus 35.8 +/- 8.2%) and increases in percentage of morphological abnormalities (3.3 +/- 0.6% versus 15.9 +/- 1.0%) in the infected group. An examination of the plasma hormonal profiles and semen characteristics in the infected bulls indicated that altered Sertoli cell function due to formation of immune complexes in four bulls (Group 2A), pituitary dysfunction in six bulls (Group 2B), testicular degeneration in three bulls (Group 2C) and finally trypanotolerancy in five bulls (Group 2D) are possible factors responsible for poor semen characteristics and infertility induced by T. evansi infection in dromedary bulls.

Long-term survival of neonatal porcine Sertoli cells in non-immunosuppressed rats

Sertoli cells from the testis contain immunoprotective properties which allow them to survive as allografts and also to protect islets and adrenal chromafin cells from immune rejection without the use of immunosuppressive drugs. Experiments were designed to determine whether xenogeneic neonatal porcine Sertoli cells (NPSCs) survive transplantation in rats without the use of immunosuppression. NPSCs (92.2 +/- 5.1%) were isolated, cultured and then transplanted under the kidney capsule of non-immunosuppressed Lewis rats. To assess survival, grafts were removed after 4, 20, 30, 40, 60, and 90 days post-transplant and immunostained for the Sertoli cell marker vimentin. Survival was confirmed by polymerase chain reaction (PCR) for the porcine mitochondrial cytochrome oxidase II (COII) subunit gene, a marker for porcine tissue. In both methods, NPSCs were detected in the grafts for at least 90 days. Histologically, NPSCs were clustered in small aggregates or organized in tubule-like structures. When stained for the presence of proliferating cell nuclear antigen (PCNA), many Sertoli cells stained positive at 20 days post-transplant, indicating not only cell survival but also Sertoli cell proliferation. The number of PCNA positive cells decreased somewhat by 40 days with almost no positive Sertoli cells at 60 and 90 days. These data demonstrate that NPSCs survive long-term following xenotransplantation in rats, which to our knowledge is the first report of a discordant xenograft surviving without immunosuppression in a non-immunoprivileged site. Further study of the mechanism of NPSC xenograft survival may provide clues for promoting a local tolerogenic environment.

Harnessing the Immunomodulatory Properties of Sertoli Cells to Enable Xenotransplantation in Type I Diabetes

Islet transplantation has emerged as a viable long-term means of treating type I diabetes. This is largely due to the success of the "Edmonton protocol" which has produced insulin independence in 85% of patients 1 year after transplantation of allogeneic islets together with a non-steroid immunosuppressive regimen. While these data provide a clear and unequivocal demonstration that islet transplantation is a viable treatment strategy, the shortage of suitable donor tissue together with the debilitating consequences of life-long immunosuppression necessitate the development of novel means to enable transplantation of all type 1 diabetics including the young juvenile diabetics. One potential means of enabling islet transplantation takes advantage of the ability of Sertoli cells to provide local immunoprotection to co-grafted islets, including those from xenogeneic sources. Sertoli cells are normally found in the testes where one of their functions is to provide local immunologic protection to developing germ cells. In animal models, allogeneic and xenogeneic islets survive and function for extended periods of time when grafted into the testes. Moreover, isolated Sertoli cells protect co-grafted allogeneic and xenogeneic islets from immune destruction and reverse diabetes in immunocompetent and autoimmune animals. These benefits are discussed in the context of several potential underlying biological mechanisms.

Intratesticular morphometric, cellular and endocrine changes around the pubertal period in dromedary camels

We obtained the paired testes from 66 clinically healthy camels during two consecutive breeding seasons. Testicular tissues were examined for peripubertal changes in histological structure as well as spermatogenic and steroidogenic activities. Cellular sizes (length microm x width microm) increased linearly (P< 0.05) throughout the first three years of the animal's life for Leydig cells and between two and a half and five years of age for Sertoli cells. A clear increase in the percentage of tubules demonstrating primary and secondary spermatocytes occurred between less than one and five years and a cohort of elongated spermatids was produced in 3.5 +/- 0.2% tubules in males of two and a half years old; the appearance of spermatozoa in 3.1 +/- 0.3% tubules was evident six months later. The basal values for intratesticular and plasma concentrations of oestradiol-17 beta and testosterone respectively, were measured in all animals up to one and a half years for oestradiol-17 beta and three years for testosterone. Thereafter, both steroids increased markedly (P< 0.01) peaking to 269.5 +/-27.1 pg/g and 83.4 +/- 8.3 pg/mL at three years for oestradiol-17 beta and to 164.7 +/- 16.8 ng/g and 6.8 +/- 0.7 ng/mL at five years for testosterone. The results suggested that a steroid hormonal shift around four and a half to five years of age could demarcate the beginning of pubertal period which culminates with the production of the first ejaculum containing higher concentrations of spermatozoa by dromedary camels of six years old.

Distribution of immune cells in the epididymis of the aging Brown Norway rat is segment-specific and related to the luminal content

Remarkable changes occur during aging in the testis and epididymis of the Brown Norway rat. A dramatic increase in the number of halo cells, which are present in the epididymal epithelium and originate from the immune system, is found in animals of increasing age. Halo cells have been postulated to be either lymphocytes or monocytes. We hypothesized that halo cells are a mixture of different immune cells and that their relative composition changes with age. To verify this hypothesis, markers for helper T lymphocytes, cytotoxic T lymphocytes, B lymphocytes, and monocytes-macrophages were used to identify the major categories of immune cells in the epididymides of Brown Norway rats ranging in age from 3 to 24 mo. The numbers of immunocompetent cells in the epididymis were determined in relation to age, epididymal segment, and luminal content. We found that monocytes, helper T lymphocytes, and cytotoxic T lymphocytes belong to the population of halo cells. In addition, a segment-specific increase with age in the number of these immune cells was noted. Finally, we report a segment-specific recruitment of cytotoxic T lymphocytes and monocytes-macrophages in the epididymal epithelium of aged rats whose epididymal lumen contained few spermatozoa. We postulate that accumulation of damaged epithelial cells and antigens of germ cell origin, leaking through a dysfunctional blood-epididymis barrier, may contribute to the active recruitment of immune cells with age.

A novel stage-specific antigen is expressed only in early stages of spermatogonia in Japanese eel, Anguilla japonica testis

We produced an antibody that recognized only early stages of spermatogonia in Japanese eel testis. This antibody (anti-spermatogonia-specific antigen-1, anti-SGSA-1) recognized a band of about 38 kDa in Western blot analysis of extracts from eel testis. This antigen was observed by immunohistochemistry only in type-A and early type-B spermatogonia and could not be seen in the late type-B spermatogonia, which appeared after the initiation of spermatogenesis by a single injection of human chorionic gonadotropin. Immunoreactive SGSA-1 was absent in spermatocytes, spermatids, spermatozoa, Sertoli cells, and interstitial Leydig cells. Similarly, this antigen was also detected only in type-A/primary spermatogonia in the testes of two species of teleosts, medaka (Oryzias latipes) and tilapia (Oreochromis niloticus), as well as a toad (Xenopus laevis). These results imply that the disappearance of SGSA-1 in late type-B/secondary spermatogonia is a critical step in the progression of spermatogenesis, and indicate that anti-SGSA-1 is a useful marker for analysis of the molecular mechanism controlling the differentiation of spermatogonia in lower vertebrates.

Targeting of the domain-specific integral membrane protein PM52 to the periacrosomal plasma membrane during guinea pig spermiogenesis

The sperm plasma membrane is segregated into functionally, biochemically, and structurally distinct domains yet the protein sorting pathways and assembly mechanisms that assemble these domains during spermiogenesis are incompletely understood. We previously characterized two structurally related size-variant, integral membrane proteins of 52 kDa (PM52) and 35 kDa localized to the periacrosomal plasma membrane of guinea pig cauda epididymal spermatozoa (Westbrook-Case et al., 1994). In this study we used light and electron microscopic immunocytochemistry to define the expression pattern and sorting pathway that establishes the domain-specific distribution of PM52 during spermiogenesis. The PM52 is first expressed in acrosome-phase spermatids and it localizes exclusively to the cytoplasmic lobe. Immunoelectron microscopy revealed that both cytoplasmic vesicles and the plasma membrane of the cytoplasmic lobe labeled with anti-PM52. During early stages of expression, PM52 appeared to be absent from the head region, but significant PM52 accumulation over the spermatid head was noted in late acrosomal phase spermatids. Throughout spermiogenesis PM52 extended posteriorly to the annulus, which represents a barrier preventing PM52 diffusion into the posterior tail. Following the migration of the annulus to the midpiece-principal piece junction, PM52 began to disappear from the flagellar region and at the completion of spermiogenesis most of the PM52 was restricted to the acrosomal segment. Spermatids and epididymal sperm PM52 exhibited identical sizes by SDS-PAGE and immunoblotting, indicating that they are not proteolytically modified during epididymal maturation. The PM52 antibodies were also used to screen a guinea pig testis cDNA library, and sequence determination of full-length PM52 clones demonstrated identity of a sperm membrane protein recently termed "sperad" (Quill and Garbers, 1996). Membrane barriers and potential mechanisms establishing the domain-specific residence of PM52 are discussed.

Autoantigenicity of the basal compartment of seminiferous tubules in the rat

The expression of testicular autoantigens has been thought to be restricted to the luminal compartment of the seminiferous tubules. In the present study it was observed that germ cells in the basal compartment of seminiferous tubules and lamina propria of the seminiferous tubule bound antibodies in anti-testis immunosera in vivo after passive transfer of the sera by intra-peritoneal injection. The anti-testis immunosera were prepared in orchiectomised rats to avoid pre-collection adsorption of antibodies in the basal compartment of the seminiferous tubules. When testis-immune sera collected from non-orchiectomised rats or normal sera were transferred no such binding of antibodies to the basal germ cell surface or the lamina propria occurred. In Western blot analysis the anti-testis immune sera prepared in orchiectomised rats defined polypeptides from the adult rat testis with relative MWs of 19-23, 26-28, 30, 34, 38, 40-43, 45-47, 51-52, 56-57, 68, 78 and 97 kDa. The 40-43 kDa band was not detected by sera prepared in non-orchiectomised rats, suggesting that this autoantigen was expressed in the basal compartment of the seminiferous tubules. These observations suggest that the segregation of testicular autoantigens in the luminal compartment of seminiferous tubules is not complete for all of them in the rat and emphasize the role of more dynamic mechanisms in prevention of anti-germ cell autoimmune disease.

Role of laminin in the morphogenetic cascade during coculture of Sertoli cells with peritubular cells

Observations summarized in this article demonstrate an essential role of laminin during the restructuring processes that occur during coculture of Sertoli cells with testicular peritubular cells. The data presented indicate that laminin becomes detectable on the free surfaces of Sertoli cells only after reaggregation of Sertoli cells begins, coincident with the initiation of repolarization at a specific stage of the morphogenetic cascade. We infer that laminin deposited at this time serves as a cohesion molecule that permits peritubular cells to come into close contact with Sertoli cells and subsequently to spread along the free surfaces of Sertoli cells. These conclusions and inferences are based on the following experiments. Cycloheximide-treated peritubular cells in culture in MEM containing cycloheximide readily attach to laminin-coated polystyrene surfaces. By contrast, added peritubular cells do not attach onto monolayers of Sertoli cells in monoculture or onto Sertoli cells plated on top of peritubular cells and maintained in coculture for periods of up to 48 h. In cocultures maintained for 6 days, however, labeled peritubular cells readily adhere to the free surfaces of reaggregated Sertoli cells. Laminin, but not fibronectin, appears on the free surfaces of the reaggregated Sertoli cells at this time, coinciding with the period of initial mound formation. The addition of antilaminin IgG, but not antifibronectin IgG, blocks the attachment of cycloheximide-treated peritubular cells to laminin-coated plates and also blocks the subsequent migration of peritubular cells required to form a monolayer. Similarly, anti-laminin IgG inhibits the attachment and spreading of labeled peritubular cells seeded on the free surfaces of reaggregated Sertoli cells in mounds generated during the morphogenetic cascade. We interpret the combined data to indicate that the appearance of laminin on the free surfaces of Sertoli cells is required to permit peritubular cells to adhere and subsequently to migrate on Sertoli cell surfaces, resulting in the formation of a tubule-like structure.

Interactions of Sertoli cells with laminin are essential to maintain integrity of the cytoskeleton and barrier functions of cells in culture in the two-chambered assembly

The addition of anti-laminin IgG to the basal surfaces of rat Sertoli cells in culture in a two-chambered assembly results in a perturbation of F-actin arrangements, including disruption of the pericellular circumferal rings, impairments of the Sertoli cell permeability barrier, and subsequently focal defoliation, followed by cell reaggregation. The pentapeptide YIGSR, which competes with the laminin receptor for laminin (Kleinman and Weeks: Curr. Oph. Cell Biol., 1:964-967, 1989; Graf et al.: Biochemistry, 26:6896-6900, 1987) also elicited focal defoliation of Sertoli cells from the extracellular matrix-coated filter in the two-chambered assembly. Addition of YIGSR to Sertoli cell cultures resulted in cell detachment within 2 to 3 h. In contrast, the irrelevant peptide YIGSE had no detectable effects. The anti-laminin IgG was effective only when added to the chamber in which access was readily available to the basal surfaces of Sertoli cells, but YIGSR was effective when added either to the outer chamber or to the inner chamber. These data were interpreted to indicate that the Sertoli cell barrier generated in the two-chambered assembly allowed a relatively rapid diffusion of YIGSR between chambers, but prevented the rapid equilibration of anti-laminin IgG between compartments. Addition of anti-laminin IgG to the basal, but not to the apical surfaces of Sertoli cells, resulted in more rapid rates of equilibration of [3H]-methoxyinulin and [86Rb]Cl across the Sertoli cell monolayer. This evidence of impairment to the integrity of the barrier was detected prior to the disruption of stress fibers and focal defoliation, but after evidence of dissolution of the circumferal F-actin ring, which occurred within 1 h after addition of anti-laminin IgG. We consider the possibility that a transmembrane link exists between extracellular laminin and cytoskeletal elements which modulates the circumferal F-actin ring. We further postulate that this linkage can influence the nature of tight junctional complexes, and thereby the integrity of the Sertoli cell barrier.

A monoclonal antibody recognizing a differentiation marker on rat gonocytes

Monoclonal antibodies (MAb) were raised against a testicular membrane fraction from 18-day post coitum (p.c.) rat testes. One antibody, designated 4B6.3E10 (mu, kappa), was obtained which specifically reacted with gonocytes in the fetal testis. No significant cross-reactivity with other tissues from the 18-day p.c. embryo was found. MAb 4B6.3E10 was reactive with rat gonocytes from 17-day p.c. until the day of birth. Germ cells at later stages of testis development did not show any labelling. The epitope recognized by 4B6.3E10 is a carbohydrate as periodate treatment leads to a loss of reactivity of the antibody. By SDS-PAGE and Western blotting of proteins extracted from a testicular membrane fraction from 18-day p.c. testes, MAb 4B6.3E10 was found to recognize at least 3 protein moieties with apparent molecular weights in the ranges of 80-100, 120, 160-180 kDa (either under reducing- or non-reducing conditions). The results suggest that MAb 4B6.3E10 recognizes a specific differentiation marker for fetal rat gonocytes.

Immunosuppressive molecules produced by Sertoli cells cultured in vitro: biological effects on lymphocytes

In the present study we have analyzed the proteins secreted in vitro by murine Sertoli cells to identify immunosuppressive factors. Our data show that Sertoli cells secrete molecules capable to inhibit proliferation of lymphocytes activated in vitro. Cytophluorimetric analysis indicates that treated cells are arrested in the G1 phase of cell cycle. The inhibitory activity is specific for both B or T lymphocytes but not for other non-lymphoid cells and is associated to proteins, heat and freeze stable, with Mr of more than 30 kDa. Lymphocytes treated with Sertoli immunosuppressive proteins drastically reduce the secretion of interleukin-2.

Competition between cell-substratum interactions and cell-cell interactions

Clusterin, a glycoprotein which elicits the aggregation of a wide variety of cells (Fritz, I. B., and Burdy, K.:J. Cell Physiol., 140:18-28, 1989), has been utilized to investigate some of the factors modulating the competition between cell-substratum interactions and cell-cell interactions. We compared the responses to clusterin by anchorage-independent cells (erythrocytes) with those by anchorage-dependent TM4 cells (a cell line derived from neonatal mouse testis cells). Cells were maintained in culture in the presence of various substrata chosen to enhance cell-substratum interactions (laminin-coated wells), or to diminish cell-substratum interactions (agarose-coated wells). Results obtained showed that the aggregation of erythrocytes elicited by clusterin was independent of the nature of the substratum. In contrast, clusterin addition resulted in aggregation of anchorage-dependent TM4 cells only when TM4 cell-substratum interactions were weak. Thus, clusterin did not aggregate TM4 cells plated upon a laminin substratum, but readily aggregated TM4 cells plated upon an agarose-coated substratum, independent of the sequence of addition of cells and clusterin to the culture dish. We utilized YIGSR, a peptide which competes with laminin for laminin receptors, to determine the possible role of laminin receptors on TM4 cells in the competition between cell-substratum interactions and cell-cell interactions. The presence of YIGSR did not alter responses of erythrocytes to clusterin under all conditions examined. In contrast, the responses of TM4 cells to clusterin were greatly changed. YIGSR addition resulted in the inhibition of aggregation of TM4 cells otherwise elicited by clusterin. YIGSR also prevented attachment of TM4 cells to a laminin-coated surface, but this was reversed by the presence of clusterin. We discuss the possible roles of clusterin and laminin in altering the balance in the competition between cell to cell interactions and cell to substratum interactions.

The blood-testis barrier and Sertoli cell junctions: structural considerations

In this review, a few well-established axioms have been challenged while others were viewed from a new perspective. The extensive literature on the blood-testis barrier has been scrutinized to help probe its mechanics and hopefully to promote understanding of the constant adaptation of the barrier function to germ cell development. Our principal conclusions are as follows: (1) Although the barrier zonule is topographically located at the base of the seminiferous epithelium it actually encircles the apex of the Sertoli cell. Consequently the long irregular processes specialized in holding and shaping the developing germ cells should be considered as apical appendages analogous to microvilli. (2) The development of the barrier zonule does not coincide with the appearance of a particular class of germ cells. (3) The barrier compartmentalizes the epithelium into only two cellular compartments: basal and lumenal. (4) Although the blood-testis barrier does sequester germ cells usually considered antigenic, immunoregulator factors other than the physical barrier seem to be involved in preventing autoimmune orchitis. (5) Structurally, a Sertoli cell junctional complex is composed of occluding, gap, close, and adhering junctions. The Sertoli cell membrane segments facing germ cells are presumably included in the continuum of the Sertoli cell junctional complex that extends all over the lateral and apical Sertoli cell membranes. (6) The modulation (i.e., formation and dismantling) of the junctions in a baso-apical direction is characteristic of the seminiferous epithelium and may be dictated by germ cell differentiation. The formation of tubulobulbar complexes and the following internalization of junction vesicles conceivably represent sequential steps of a single intricate junction elimination process that involves junction membrane segments from different cell types as part of a continual cell membrane recycling system. (7) The preferential association of junctional particles with one or the other fracture-face reflect a response to various stimuli including seasonal breeding. Changes in the affinity of the particles are generally coincidental with cytoskeletal changes. However, changes in the cytoskeleton are not necessarily accompanied by permeability changes. The number of strands seems to reflect neither the junctional permeability nor the transepithelial resistance. The diverse orientation of the strands seems to be related to the plasticity of the Sertoli cell occluding zonule. (8) Cooperation between all constituents (Sertoli cells, myoid cells, cell substratum, and germ cells) of the epithelium seems essential for the barrier zonule to function in synchrony with the germ cell differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Stage- and cell-specific expression of the ornithine decarboxylase gene during rat and mouse spermatogenesis

Ornithine decarboxylase (ODC) is an enzyme that has been shown to be induced in the growth, differentiation and proliferation of cells. We have used a cDNA probe to determine ODC mRNA levels in different stages of the cycle of rat and mouse seminiferous epithelium. For Northern and slot-blot hybridizations, RNA was isolated from microdissected staged seminiferous tubules. Cell-specific localization of ODC mRNA was studied by in situ hybridization. In the rat, in situ hybridization showed increasing mRNA levels during prophase of meiosis with the highest mRNA levels seen in late pachytene spermatocytes and step 3-5 spermatids. In the mouse, the mRNA levels increased in a similar fashion and the highest mRNA levels were found in step 1-8 spermatids. In the rat, Northern blot hybridizations revealed three molecular sizes of ODC mRNA: 2.2, 2.7 and 1.6 kb. The levels of all molecular sizes were highest in stages VII-VIII, and the lowest mRNA levels were seen in stage I of the seminiferous epithelial cycle. The level of the 2.2 kb transcript was low during stages XIII-I. In the mouse, the Northern blot hybridizations also showed three molecular sizes of ODC mRNA: 2.2 and 2.7 kb and very low levels of 1.6 kb transcript. The levels of the transcripts were steady throughout the cycle. In the mouse, the 2.2 kb transcript was more abundant than the 2.7 kb transcript indicating a species difference between rat and mouse in the usage of the two polyadenylation signals within the ODC gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies to sperm surface fertilization antigen (FA-1): their specificities and site of interaction with sperm in male genital tract

The fertilization antigen (FA-1) isolated from murine testes demonstrated its dimeric form of 49,000 +/- 2,000 molecular weight (M.W.) or a monomer of 23,000 M.W. on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The FA-1 was immunogenic in all three female rabbits tested and raised a high-titer antisera [enzyme-linked immunosorbent assay (ELISA) titers; 1:1,024 to 1:4,096]. The rabbit anti-FA-1 antisera predominantly recognized the dimeric form of 49,000 +/- 2,000 M.W. on the Western blot of lithium diiodosalicylate (LIS)-solubilized murine testes. None of the antisera reacted with any somatic tissue, indicating germ-cell specificity of FA-1. To determine the cellular localization of the immunoreactive FA-1, a novel ultrasensitive immunogold-silver staining (IGSS) procedure was developed. The anti-FA-1-IgG showed intense staining in the luminal region of the seminiferous tubules containing spermatids and spermatozoa. No reaction was observed in the peripheral area of the tubules containing Sertoli cells, spermatogonia, leptotene, and zygotene spermatocytes. The biodistribution studies of 125I-labeled anti-FA-1 IgG in mice revealed that the antibodies do not bind to somatic tissues such as blood cell, liver, heart, kidney, muscle, and gastrointestinal tissue and do not transudate into testes and seminal vesicle. However, the antibodies preferentially transudate into epididymis (especially corpus or cauda regions) and vas deferens to bind to sperm cells. In conclusion, our data indicate that FA-1 can induce an immune response that is germ cell-specific, directed against later stages of spermatogenesis. The antibodies to FA-1 interact with sperm after penetration through epididymis (especially corpus and cauda regions) and vas deferens rather than through testes and seminal vesicles.

Identification of rat testis galactosyl receptor using antibodies to liver asialoglycoprotein receptor: purification and localization on surfaces of spermatogenic cells and sperm

We have found that the rat testis contains a cell surface galactosyl receptor that is antigenically related to the minor species of rat liver asialoglycoprotein receptor (ASGP-r) and has binding affinity for galactose coupled to agarose. In immunoblotting experiments, rat testis galactosyl receptor (RTG-r) is recognized by antiserum raised against the minor ASGP-r species of rat liver (designated rat hepatic lectin-2/3, RHL-2/3). Antiserum raised against the major species RHL-1 does not recognize an antigenic protein equivalent to RTG-r. Triton X-100-extracted rat liver and testes preparations fractionated by affinity chromatography on galactose-agarose and resolved by SDS-PAGE under reducing conditions, show that rat liver contains both the major (RHL-1) and minor (RHL-2/3) ASGP-r species whereas rat testis displays only a receptor species comigrating with RHL-2/3. RTG-r was present throughout testicular development. The receptor was found in seminiferous tubules, cultured Sertoli and spermatogenic cells, and epididymal sperm. Indirect immunofluorescent studies show RHL-2/3-like immunoreactivity on the surface of Sertoli cell, meiotic prophase spermatocytes, spermatids, and epididymal sperm. In spermatids and sperm, the immunoreactivity is restricted to the plasma membrane overlying the dorsal portion of the head. Because of RTG-r has galactose binding affinity, is present on surfaces of Sertoli and developing meiotic and postmeiotic spermatogenic cells, and overlies a region of the intact acrosome on epididymal sperm, RTG-r may have a role in spermatogenesis and in events leading to sperm-egg recognition.

Restricted lesions after testicular biopsies in young and adult rats

In order to evaluate the possible harmful effects of surgical removal of a testicular biopsy, adult and immature rats were subjected to unilateral testicular biopsy and were studied 2-4 months later. One group of adult rats were sham-operated. Perfusion-fixed, plastic-embedded specimens of the testes were examined by light microscopy. No morphological differences were found between rats that were immature and those that were adult at the time of biopsy. The lesions observed were focal and occurred only in the vicinity of the site of biopsy. Only about 0.5% (range 0.01-4.5) of the testis was affected. No morphological signs of any immune reaction were observed. It is suggested that the lesions are caused mainly by interference with local blood flow, and to a minor extent by disruption of the flow of seminiferous tubule fluid.

Evidence for active immunological regulation in prevention of testicular autoimmune disease independent of the blood-testis barrier

It has long been considered that autoimmune disease of the testis is prevented by sequestration of testis-specific autoantigens on germ cells behind the blood-testis (BT) barrier. However, we now have evidence that not all such antigens are sequestered. Some appear to reside on germ cells in the basal compartment of the seminiferous tubule where they are accessible to antibodies and to circulating activated T cells. Mice immunized with syngeneic testis homogenate are found to have immunoglobulin G (IgG) bound to cells in the basal compartment before onset of orchitis. This IgG is absorbed from circulation by the testis and, therefore, found only in the serum of mice orchiectomized before immunization. When the IgG is eluted from the testis, it is found to react preferentially with testicular cells enriched in preleptotene spermatocytes. T cells from mice immunized with testis can be transferred to naive syngeneic mice where they infiltrate the testis to cause orchitis. This implies that the BT barrier does not need to be breached directly for specific T cells to have access to testicular autoantigens on antigen presenting cells. Thus, active systemic and/or local immunoregulatory mechanisms must operate to prevent testicular autoimmune disease. These mechanisms may operate at the level of suppressor T cells, nonspecific suppression in the local environment of the testis, antigen presentation in the testis, or lymphocyte trafficking in the testis. These mechanisms probably operate only on the afferent limb of the immune response since they are overridden and orchitis occurs once testis-specific activated T cells are generated.

Topography and behavior of Sertoli cells in sparse culture during the transitional remodeling phase

We report observations on the behavior of Sertoli cells in sparse culture during the period from the time of plating to the time of initial confluence (the transitional remodeling phase). Changes in shape, structure, and polarity of cells, as well as changes in migration patterns and cell-cell association patterns, have been followed during the transitional remodeling phase with the aid of topographical markers. These markers are based upon differences between ultrastructural features of the basolateral and apicolateral surfaces. The basolateral surface is characterized by plasmalemmal blebs, whereas the apicolateral surface is characterized by filopodial extensions. Structural differences observed in situ remain evident in Sertoli cells isolated by sequential enzymatic treatments that are described. Another marker is provided by laminin-binding sites, which are detected exclusively on the blebbed, basolateral surfaces of freshly prepared Sertoli cell aggregates. The orientation described is sustained during the initial radial migration of Sertoli cells explanted on uncoated glass coverslips. Under these conditions, blebs are detected only on the dorsal surfaces, and filopodial extensions are evident only on the ventral surfaces. In contrast, Sertoli cells sparsely plated on a reconstituted basement membrane (air-dried Matrigel) migrate rapidly, display an extraordinary capacity to form elaborate cytoplasmic extensions for cell-cell and cell-substratum contacts, and readily retract blebs and filopodial extensions. These cells do not form mosaic borders, whereas cells plated on uncoated glass do form a monolayer with mosaic-like borders. Cells sparsely seeded on gelated Matrigel migrate preferentially at gaps between adjacent cell explants, and develop a compact cell-cell association pattern. These cells display few, if any, cytoplasmic extensions. We compare the behavior of Sertoli cells sparsely plated on Matrigel with the behavior of Sertoli cells in situ during different stages of development.

Fucosylation events during mammalian spermatogenesis

It will be necessary to conduct further studies to establish more precisely the localization of FT on mouse male germ cells. Antibodies to FTs are not yet available, so an immunocytochemical approach is not currently feasible. Additional cell fractionation protocols can be designed to compare plasma membrane fractions with enriched fractions of Golgi apparatus and to compare directly the activities of multiple glycosyltransferase enzymes and Golgi-specific markers in these preparations. Schachter et al. and Nyquist and colleagues have already provided experimental techniques for the isolation of Golgi fractions of good purity from rodent pachytene spermatocytes and spermatids. Ample opportunity exists, then, for a detailed analysis of the number, specificity, and localization of FT enzymes during mammalian spermatogenesis. All available data imply that these enzymes will prove to be vital components in the differentiation of cells within the seminiferous epithelium.

Spatial and temporal expression of cell surface galactosyltransferase during mouse spermatogenesis and epididymal maturation

We have previously shown that sperm-egg recognition in the mouse is mediated by the binding of galactosyltransferase (GalTase) on the sperm surface to its appropriate glycoside substrate in the egg zona pellucida [L. C. Lopez, E. M. Bayna, D. Litoff, N. L. Shaper, J. H. Shaper, and B. D. Shur (1985) J. Cell Biol. 101, 1501-1510]. In the present study, we have defined the spatial and temporal expression of surface GalTase during spermatogenesis and epididymal maturation. Purified populations of spermatogenic cells were isolated by unit gravity sedimentation, and surface GalTase expression was determined by indirect immunofluorescence and by direct enzymatic assay. GalTase is present on the surface of all spermatogenic cells assayed. During differentiation, there is a progressive redistribution of GalTase from an initially diffuse and uniform localization on the surface of primary spermatocytes to a restricted plasma membrane domain overlying the dorsal aspect of the mature acrosome. This apparent redistribution of surface GalTase was confirmed by direct enzymatic assays, which show that surface GalTase activity, normalized per cell, remains relatively constant throughout spermatogenesis, despite a drastic reduction in cell surface area. When normalized to the relevant cell surface area, the GalTase concentration per square micrometer increases 77-fold from pachytene spermatocytes to cauda epididymal sperm. Cell surface GalTase is thought to be a cytoskeletally associated transmembrane protein [N. L. Shaper, P. L. Mann, and J. H. Shaper (1985) J. Cell Biochem. 28, 229-239]; consequently we examined whether cytoskeletal components may be involved in the redistribution of GalTase during spermatogenesis. beta-Tubulin, monomeric actin, and filamentous actin were found to be present during spermatogenesis, as assayed by indirect immunofluorescence and by Western immunoblotting. alpha-Actinin and vinculin were not detectable under these conditions and served as negative controls. During spermatogenesis, the distribution of tubulin coincides with the appearance of the mitotic spindle, flagellum, and manchette. On the other hand, the distribution of filamentous actin coincides with surface GalTase, suggesting that actin-containing microfilaments may participate in the redistribution of surface GalTase during spermatogenesis.

Molecular dissection of human testicular germ cell differentiation with monoclonal antibodies

Monoclonal antibodies (MoAbs) were raised by immunising mice with nucleated cells other than sperm (NCOS) obtained from semen of an oligospermic donor. These MoAbs recognised different germ cell differentiation antigens (GDA) which appear at various stages of spermatogenesis and/or spermiogenesis. The GDA were found to be differentially expressed on spermatocytes, spermatids and on the various sub-regions of human spermatozoe. Some of the MoAbs also recognised changes in the antigenic structure of the sperm during their post-testicular maturation. Using solubilised sperm products, MoAb GDA-J/F1 reacted with a 92 kDa band in Western immunoblotting. The importance of these antibodies in the study of germ cell differentiation together with their potential clinical uses in the investigation of infertility, autoimmunity and immunological contraception are discussed.

Ontogeny and cellular origin of a rat seminiferous tubule factor(s) that inhibits LH-dependent testosterone production by interstitial cells in vitro

Previous studies have shown the presence of a peptide in spent media from incubated seminiferous tubules (SMST), which inhibits LH stimulation of testosterone production by rat Leydig cells in vitro. The present study has investigated whether the secretion of this inhibitor changes during development in the rat. Seminiferous tubules obtained from rats aged 10, 20, 25, 30, 35, 40, 42, 50 or 60 days were incubated at 32 degrees C for 24 h. Spent media from these incubations were then added to interstitial cells isolated from the testes of rats aged 60 days. Spent media from rats aged 10-30 days had no effect on basal or oLH-stimulated testosterone production by interstitial cells during 3-h incubation. Significant inhibition of LH-stimulated testosterone production was, however, observed with SMST from rats aged 35-60 days. Spent media prepared using tubules from normal, prenatally irradiated (Sertoli cell-enriched) or seminiferous tubules, depleted of peritubular cells, had no effect on basal, but inhibited LH-stimulated, testosterone production. Spent media from peritubular cell cultures had no effect on basal or LH-stimulated testosterone production by interstitial cells. The inhibitory effect of SMST was also dependent on the age of the rats providing the target cells. Interstitial cells from rats aged 10, 20, 50 or 60 days were responsive to the inhibitor while cells from rats aged 30 and 40 days were not. The results of the present study demonstrate that the seminiferous tubule factor(s), which inhibits LH action on interstitial cells, is first secreted at 35 days, a time when the most mature germ cells present are in the early maturation phase. Moreover, interstitial cells are responsive to this factor in both immature (10-20 day-old) and mature (50-60 day-old) rats, but not at ages in between these times. It is suggested that the adult Sertoli cell is the major source of the interstitial cell inhibitor.