CD106 (VCAM-1) in testicular immunoregulation

Actl7b deficiency leads to mislocalization of LC8 type dynein light chains and disruption of murine spermatogenesis

Actin-related proteins (Arps) are classified according to their similarity to actin and are involved in diverse cellular processes. ACTL7B is a testis-specific Arp, and is highly conserved in rodents and primates. ACTL7B is specifically expressed in round and elongating spermatids during spermiogenesis. Here, we have generated an Actl7b-null allele in mice to unravel the role of ACTL7B in sperm formation. Male mice homozygous for the Actl7b-null allele (Actl7b-/-) were infertile, whereas heterozygous males (Actl7b+/-) were fertile. Severe spermatid defects, such as detached acrosomes, disrupted membranes and flagella malformations start to appear after spermiogenesis step 9 in Actl7b-/- mice, finally resulting in spermatogenic arrest. Abnormal spermatids were degraded and levels of autophagy markers were increased. Co-immunoprecipitation with mass spectrometry experiments identified an interaction between ACTL7B and the LC8 dynein light chains DYNLL1 and DYNLL2, which are first detected in step 9 spermatids and mislocalized when ACTL7B is absent. Our data unequivocally establish that mutations in ACTL7B are directly related to male infertility, pressing for additional research in humans.

Transcriptomic differences between fibrotic and non-fibrotic testicular tissue reveal possible key players in Klinefelter syndrome-related testicular fibrosis

Klinefelter syndrome (KS; 47,XXY) affects 1-2 in 1000 males. Most men with KS suffer from an early germ cell loss and testicular fibrosis from puberty onwards. Mechanisms responsible for these processes remain unknown. Previous genomics studies on testis tissue from men with KS focused on germ cell loss, while a transcriptomic analysis focused on testicular fibrosis has not yet been performed. This study aimed to identify factors involved in the fibrotic remodelling of KS testes by analysing the transcriptome of fibrotic and non-fibrotic testicular tissue. RNA sequencing was performed to compare the genes expressed in testicular samples with (KS and testis atrophy) and without (Sertoli cell-only syndrome and fertile controls) fibrosis (n = 5, each). Additionally, differentially expressed genes (DEGs) between KS and testis atrophy samples were studied to reveal KS-specific fibrotic genes. DEGs were considered significant when p < 0.01 and log2FC > 2. Next, downstream analyses (GO and KEGG) were performed. Lastly, RNA in situ hybridization was performed to validate the results. The first analysis (fibrotic vs non-fibrotic) resulted in 734 significant DEGs (167 up- and 567 down-regulated). Genes involved in the extracellular structure organization (e.g. VCAM1) were found up-regulated. KEGG analysis showed an up-regulation of genes involved in the TGF-β pathway. The KS vs testis atrophy analysis resulted in 539 significant DEGs (59 up- and 480 down-regulated). Chronic inflammatory response genes were found up-regulated. The overlap of X-linked DEGs from the two analyses revealed three genes: matrix-remodelling associated 5 (MXRA5), doublecortin (DCX) and variable charge X-Linked 3B (VCX3B). RNA in situ hybridization showed an overexpression of VCAM1, MXRA5 and DCX within the fibrotic group compared with the non-fibrotic group. To summarize, this study revealed DEGs between fibrotic and non-fibrotic testis tissue, including VCAM1. In addition, X-linked fibrotic genes were revealed, e.g. MXRA5, DCX and VCX3B. Their potential role in KS-related testicular fibrosis needs further study.

Testicular Immunity and Its Connection with the Microbiota. Physiological and Clinical Implications in the Light of Personalized Medicine

Reproduction is a complex process, which is based on the cooperation between the endocrine-immune system and the microbiota. Testicular immunity is characterized by the so-called immune privilege, a mechanism that avoids autoimmune attacks against proteins expressed by spermatozoa. Testicular microbiota is connected with the gut microbiota, the most prevalent site of commensals inthe body. Both microbiotas take part inthe development of the immune system and protection againstpathogen invasion. Dysbiosis is caused by concurrent pathologies, such as obesity, diabetes, infections and trauma. The substitution of beneficial bacteria with pathogens may lead to destruction of spermatozoa directly or indirectly and, ultimately, to male infertility. Novel therapeutic interventions, i.e., nutritional interventions and supplementation of natural products, such as, probiotics, prebiotics, antioxidants and polyphenols, may lead to the restoration of the otherwise-impaired male reproductive potential, even if experimental and clinical results are not always concordant. In this review, the structure and immune function of the testis will be described with special reference to the blood-testisbarrier. The regulatory role of both the gut and testicular microbiota will be illustrated in health and disease, also emphasizing therapeutic attempts with natural products for the correction of male infertility, in the era of personalized medicine.

VCAM1-α4β1 integrin interaction mediates interstitial tissue reconstruction in 3-D re-aggregate culture of dissociated prepubertal mouse testicular cells

Roles of interstitial tissue in morphogenesis of testicular structures remain less well understood. To analyze the roles of CD34⁺ cells in the reconstruction of interstitial tissue containing Leydig cells (LCs), and testicular structures, we used 3D-reaggregate culture of dissociated testicular cells from prepubertal mouse. After a week of culture, adult Leydig cells (ALCs) were preferentially incorporated within CD34⁺ cell-aggregates, but fetal LCs (FLCs) were not. Immunofluorescence studies showed that integrins α4, α9 and β1, and VCAM1, one of the ligands for integrins α4β1 and α9β1, are expressed mainly in CD34⁺ cells and ALCs, but not in FLCs. Addition of function-blocking antibodies against each integrin and VCAM1 to the culture disturbed the reconstruction of testicular structures. Antibodies against α4 and β1 integrins and VCAM1 robustly inhibited cell-to-cell adhesion between testicular cells and between CD34⁺ cells. Cell-adhesion assays indicated that CD34⁺ cells adhere to VCAM1 through the interaction with α4β1 integrin. Live cell imaging showed that CD34⁺ cells adhered around ALC-aggregates. CD34⁺ cells on the dish moved toward the aggregates, extending filopodia, and entered into them, which was disturbed by VCAM1 antibody. These results indicate that VCAM1-α4β1 integrin interaction plays pivotal roles in formation of testicular interstitial tissues in vitro and also in vivo.

T Lymphocytes and Testicular Immunity: A New Insight into Immune Regulation in Testes

The immune privilege of the testes is necessary to prevent immune attacks to gamete-specific antigens and paternal major histocompatibility complex (MHC) antigens, allowing for normal spermatogenesis. However, infection and inflammation of the male genital tract can break the immune tolerance and represent a significant cause of male infertility. Different T cell subsets have been identified in mammalian testes, which may be involved in the maintenance of immune tolerance and pathogenic immune responses in testicular infection and inflammation. We reviewed the evidence in the published literature on different T subtypes (regulatory T cells, helper T cells, cytotoxic T cells, γδ T cells, and natural killer T cells) in human and animal testes that support their regulatory roles in infertility and the orchitis pathology. While many in vitro studies have indicated the regulation potential of functional T cell subsets and their possible interaction with Sertoli cells, Leydig cells, and spermatogenesis, both under physiological and pathological processes, there have been no in situ studies to date. Nevertheless, the normal distribution and function of T cell subsets are essential for the immune privilege of the testes and intact spermatogenesis, and T cell-mediated immune response drives testicular inflammation. The distinct function of different T cell subsets in testicular homeostasis and the orchitis pathology suggests a considerable potential of targeting specific T cell subsets for therapies targeting chronic orchitis and immune infertility.

Expression of cell adhesion molecules, chemokines and chemokine receptors involved in leukocyte traffic in rats undergoing autoimmune orchitis

The testis is considered an immunologically privileged site where germ cell antigens are protected from autoimmune attack. Yet in response to infections, inflammatory diseases, or trauma, there is an influx of leukocytes to testicular interstitium. Interactions between endothelial cells (EC) and circulating leukocytes are implicated in the initiation and evolution of inflammatory processes. Chemokines are a family of chemoattractant cytokines characterized by their ability to both recruit and activate cells. Thus, we investigated the expression of CCL3, its receptors, and adhesion molecules CD31 and CD106 in an in vivo model of experimental autoimmune orchitis (EAO). In EAO, the highest content of CCL3 in testicular fluid coincides with onset of the disease. However, CCL3 released in vitro by testicular macrophages is higher during the immunization period. The specific chemokine receptors, CCR1 and CCR5, were expressed by testicular monocytes/macrophages and an increased number of CCR5+ cells was associated with the degree of testicular lesion. EC also play an essential role by facilitating leukocyte recruitment via their ability to express cell surface adhesion molecules that mediate interactions with leukocytes in the bloodstream. Rats with EAO showed a significant increase in the percentage of CD31+ EC that upregulate the expression of CD106. The percentage of leukocytes isolated from peripheral blood and lymph nodes expressing CD49d (CD106 ligand) also increases during orchitis. These data suggest that cell adhesion molecules, in conjunction with chemokines, contribute to the formation of a chemotactic gradient within the testis, causing the leukocyte infiltration characteristic of EAO histopathology.

Immunoprivileged sites: the testis

The testis is an immunological privileged tissue as evidenced by its ability to support grafts with minimal rejection. Immune privilege is essential for the tolerance of neo-antigens from developing germ cells that appear after the constitution of self-tolerance, but imposes the paradoxical task of also providing efficient protection against pathogens and tumor cells. It is becoming increasingly clear that immune privilege cannot be attributed to a single factor such as the sequestration of neo-antigens from the immune system behind the blood-testis barrier, but is based on a complex multifaceted interplay between cells and factors that are essential for the reproductive function of the testis and the testicular immune system. This review summarizes the evidence that has accumulated regarding the role of Sertoli cells, androgens, and selected population of leukocytes in the maintenance of immune privilege and its perturbation in testicular inflammatory sub- and infertility.

Expression and putative function of lymphocyte endothelial epithelial-cell adhesion molecule in human testis

The testis is an immunologically privileged site where germ cell antigens are protected from autoimmune attack and foreign tissue grafts may survive for extended periods. However, the testicular environment does not preclude inflammatory reactions and tissue-specific recruitment of T lymphocytes appears to be a crucial component of the inflammation cascade. Here, we demonstrate expression of lymphocyte endothelial epithelial-cell adhesion molecule (LEEP-CAM), a putative receptor mediating lymphocyte adhesion to endothelia and some epithelia, in human testis. In all specimens examined, expression of LEEP-CAM could be observed on endothelial cells of testicular blood vessels, including those within the lamina propria of seminiferous tubules. Sections of histologically normal testis showed strong LEEP-CAM expression within the seminiferous epithelium localised to Sertoli cells, whereas immunoreactivity was almost absent in tubules with severely impaired spermatogenesis. In a modified Stamper-Woodruff adhesion assay, binding of activated lymphocytes to normal testicular tissue was reduced by 61% after incubation with anti-LEEP-CAM mAb as compared with controls (P < 0.00001). In conclusion, intratubular LEEP-CAM expression is correlated with normal spermatogenesis and Sertoli cell function. In this context, it may contribute to adhesive cell-cell interactions. Moreover, the constitutive expression in human testis could play a role for localisation of T cells during testicular inflammation.

Testikuläre Ischämie

BACKGROUND

Ischemia and reperfusion (I/R) lead to cellular damage. A disturbance of testicular perfusion occurs during the therapy of cryptorchidism and in cases of testicular torsion. This results in the activation of mediator cells with an increasing synthesis of mediators of infection like TNF-alpha and the expression of cell adhesion molecules like ICAM (intercellular adhesion molecule) and VCAM (vascular cell adhesion molecule) at the cellular surface.

METHODS

The expression of the cytokines IL-10 and TNF-alpha and the adhesion molecules ICAM and VCAM after defined testicular I/R injury in nine male transsexuals was evaluated with rt-PCR. Furthermore we examined lactate and the diameter of the testicular tubulus under ischemic conditions.

RESULTS

During ischemia ICAM, IL-10, and VCAM do not show significant changes on the side of testicular ischemia and the contralateral side; the same was seen for the tubulus diameter. TNF-alpha and the testicular lactate values showed a significant change of the expression pattern.

DISCUSSION

The statistical changes of TNF-alpha and testicular lactate are the expression of leukocyte migration, infectious reaction, and immune response. To what extent the TNF-alpha expression represents a severe immunological reaction remains undefined. This human study shows primary results for the immunological understanding of and cellular response to testicular ischemia.

The murine testicular transcriptome: characterizing gene expression in the testis during the progression of spermatogenesis

One of the most promising applications of microarrays is the study of changes in gene expression associated with the growth and development of mammalian tissues. The testis provides an excellent model to determine the ability of microarrays to effectively characterize the changes in gene expression as an organ develops from birth to adulthood. To this end, a developmental testis gene expression time course profiling the expression patterns of approximately 36 000 transcripts on the Affymetrix MGU74v2 GeneChip platform at 11 distinct time points was created to gain a greater understanding of the molecular changes necessary for and elicited by the development of the testis. Additionally, gene expression profiles of isolated testicular cell types were created that can aid in the further characterization of the specific functional actions of each cell type in the testis. Statistical analysis of the data revealed 11 252 transcripts (9846 unique) expressed differentially in a significant manner. Subsequent cluster analysis produced five distinct expressional patterns within the time course. These patterns of expression are present at distinct chronological periods during testis development and often share similarities with cell-specific expression profiles. Analysis of cell-specific expression patterns produced unique and characteristic groups of transcripts that provide greater insight into the activities, biological and chronological, of testicular cell types during the progression of spermatogenesis. Further analysis of this time course can provide a distinct and more definitive view into the genes implicated, known and unknown, in the maturation, maintenance, and function of the testis and the integrated process of spermatogenesis.

Changes in Leydig cell gene expression during development in the mouse

Developmental changes in the expression of 18 Leydig cell-specific mRNA species were measured by real-time polymerase chain reaction to partially characterize the developmental phenotype of the cells in the mouse and to identify markers of adult Leydig cell differentiation. Testicular interstitial webs were isolated from mice between birth and adulthood. Five developmental patterns of gene expression were observed. Group 1 contained mRNA species encoding P450 side chain cleavage (P450(scc)), P450(c17), relaxin-like factor (RLF), glutathione S-transferase 5-5 (GST5-5), StAR protein, LH receptor, and epoxide hydrolase (EH); group 2 contained 3beta-hydroxysteroid dehydrogenase (3beta-HSD) VI, 17beta-hydroxysteroid dehydrogenase (17beta-HSD) III, vascular cell adhesion molecule 1, estrogen sulfotransferase, and prostaglandin D (PGD)-synthetase; group 3 contained patched and thrombospondin 2 (TSP2); group 4 contained 5alpha-reductase 1 and 3alpha-hydroxysteroid dehydrogenase; group 5 contained sulfonylurea receptor 2 and 3beta-HSD I. Group 1 contained genes that were expressed in fetal and adult Leydig cells and which increased in expression around puberty toward a maximum in the adult. Group 2 contained genes expressed only in the adult Leydig cell population. Group 3 contained genes with predominant fetal/neonatal expression in the interstitial tissue. Group 4 contained genes with a peak of expression around puberty, whereas genes in group 5 show little developmental change in expression. Highest mRNA levels in descending order were RLF, P450(c17), EH, 17beta-HSD III, PGD-synthetase, GST5-5, and P450(scc). Results identify five genes expressed in the mouse adult Leydig cell population, but not in the fetal population, and one gene (TSP2) that may be expressed only in the fetal Leydig cell population. The developmental pattern of gene expression suggests that three distinct phases of adult Leydig cell differentiation occur.

Local regulation of T cell numbers and lymphocyte-inhibiting activity in the interstitial tissue of the adult rat testis

The testis is an immunologically privileged site, and transplantation data suggest that this privilege may be enhanced in cryptorchidism. Although alphabetaT cells, which mediate and promote the immune response, have access to the normal testis, relatively little is known about these cells in the abdominally located testis. An increase in testicular lymphocyte-inhibiting cytokines has also been implicated in enhanced graft survival following the experimental induction of cryptorchidism. Consequently, T cell traffic and lymphocyte-inhibiting activity in testes of cryptorchid adult rats were examined in the following study. Numbers of alphabetaT cells and the cytotoxic CD8(+) T cell subset in the testis were unaffected following 1 month of cryptorchidism. In contrast, subcutaneous testosterone implants, which inhibit Leydig cell function through suppression of gonadotrophin secretion, reduced these parameters in both scrotal and abdominal testes. Testicular T cell numbers were positively correlated with the number of testicular resident macrophages, which also were reduced by subcutaneous testosterone implants. The concentration of lymphocyte-inhibiting activity in the testicular interstitial fluid was reduced by 80% in short-term (1 month) and longer-term (3 months) cryptorchidism. These data indicate that the T cell population, and in particular the CD8(+) T cell subset, in the rat testis is functionally related to the resident macrophages or Leydig cells. On the other hand, testicular lymphocyte-inhibiting activity does not appear to be a determinant of the number of testicular T cells, and may not be a major factor in the prolonged survival of certain grafts in the abdominal testis.

Expression of antigens involved in the presentation of lipid antigens and induction of clonal anergy in the female reproductive tract

The molecular backgrounds of the anti-phospholipid syndrome and immunisation against the Rhesus proteolipid antigens are still largely unknown. In the present study, expression of (1) CD1, a major histocompatibility complex class l-like lipid antigen presenting molecule, (2) IL-10, a cytokine promoting induction of clonal anergy, and (3) CD80 and CD86, two T-cell costimulators preventing induction of clonal anergy when present, was investigated in frozen sections of cervix, corpus and the fallopian tube (FT) of 25-day-old BALB/c mice injected with FSH, progesterone or medium and of pregnant mice from each trimester (days 7, 14 and 19). CD1 was expressed by all endometrial epithelial cells. Enhanced immunostaining of the endometrial epithelial cells was observed after FSH treatment, and cervix and FT expressed generally more than the corpus of the uterus. After treatment with medroxy progesterone acetate (MPA), expression of CD1 by the endometrial epithelia was weak. During pregnancy CD1 was absent from the endometrium adjacent to the foetus, but was unaltered in the cervix and FT. IL-10 was expressed by the endometrial glands and also by the endometrial surface epithelium. MPA treatment increased the intensity of the IL-10 immunofluorescence. There were also chains of positive cells between the muscle bundles within the pregnant myometrium. CD80 and CD86 were usually absent from the female reproductive tract, but were occasionally found in the cervix during pregnancy. The present study demonstrates definite differences in the expression of both CD1 and IL-10 between the FSH and MPA treated mice, suggesting differences during the oestrous cycle. As IL-10 is expressed more in the secretory phase, it is probably involved in making the endometrium more acceptable for implantation by inducing clonal anergy. This is supported by the absence of CD80 and CD86. These results also suggest that abnormal expression of CD1d during pregnancy may predispose the mother for immunisation against lipid antigens such as membrane phospholipids and Rhesus-antigens.

Experimental testicular teratoma promotes formation of humoral immune responses in the host testis

The testis is an immunologically privileged site. Very little is known about the factors regulating formation of immune responses elicited by a neoplasm in the testis. We have studied the immune response of the host testis against experimental testicular teratoma in mouse by localizing adhesion molecules (CD106, CD54, CD49d/CD29, CD44, CD18, CD8 and CD4), cytokines (IL-2, IL-4, IL-6, IL-10 and IL-12), T-cell costimulators (CD80, CD86) and the lipid antigen presenting molecule CD1d in the testis of 129/SvJ mice with and without experimental testicular teratoma. The testicular teratomas were induced by grafting male gonadal ridges from 12-day-old 129/SvJ mouse fetuses into testes of adult mice from the same strain. The tumors cultured intratesticularly for 2, 3, 4 and 8 weeks (three animals per time point) were used for immunocytochemistry. CD1d was detected in Sertoli cells and in some degenerated tubules of the host testis surrounding the graft. In the tumor, CD1d was detected in glandular epithelia, smooth muscle and in thin fibers of neural origin. IL-2 was observed in some blood vessels of the host testis and of the tumor and in occasional cell infiltrates around these vessels. Some tubular structures of the tumor were also positive for IL-2. IL-6 was detected in Sertoli cells of the normal testis and in Sertoli cells and in solitaryinterstitial cells as well as in the walls of some blood vessels of the host testis. The reaction for IL-6 was more prominent in the tubules apparently damaged by the growing tumor. In the tumor IL-6 was detected in epithelial structures, muscle cells, in thin fibers of neural origin and in some blood vessels. IL-10 was detected in individual cells in the interstitium and in degenerating tubules of the host testis. In the tumor the epithelial structures were positive for IL-10. The interstitium of the host testis was positive for CD106 and the embryonic testicular cords in the graft were also positive, but the tumor was negative. CD44 and CD18 were observed in some blood vessels and in degenerated tubules of the host testis. In the tumor CD44 and CD18 were occasionally observed in cartilage and in epithelial structures. The results of the present study suggest that cytokine microenvironment in the testis containing neoplastic tissue promotes activation of humoral immune responses. In addition, as the damaged seminiferous tubules expressed increased amounts of two cytokines promoting humoral immune responses, IL-6 and IL-10, it is possible that also in other conditions with damage to the tubules, humoral immune responses predominate.