Testicular Contractile Cells and Sperm Transport**Supported by Grant CA 09110-03 from the National Cancer Institute, Department of Health, Education and Welfare (to J. L. H.); Grant X044 from the Department of Medicine, University of Iowa (to J. H. M.); and Research Project Grant U-300 from Utah State University (to L. C. E.)

Toward understanding the role of the interstitial tissue architects: Possible functions of telocytes in the male gonad

Telocytes represent a relatively recently discovered population of interstitial cells with a unique morphological structure that distinguishes them from other neighboring cells. Through their long protrusions extending from the cell body, telocytes create microenvironments via tissue compartmentalization and create homo- and hetero-cellular junctions. These establish a three-dimensional network enabling the maintenance of interstitial compartment homeostasis through regulation of extracellular matrix organization and activity, structural support, paracrine and juxtracrine communication, immunomodulation, immune surveillance, cell survival, and apoptosis. The presence of telocytes has also been confirmed in testicular interstitial tissue of many species of animals. The objective of this review is to summarize recent findings on telocytes in the male gonad, on which conclusions have been deduced that indicate the involvement of telocytes in maintaining the cytoarchitecture of the testicular interstitial tissue, in the processes of spermatogenesis and steroidogenesis, and photoperiod-mediated changes in the testes in seasonally reproductive animals.

Purinergic Signaling in Spermatogenesis

Adenosine triphosphate (ATP) serves as the essential source of cellular energy. Over the last two decades, however, ATP has also attracted increasing interest as an extracellular signal that activates purinergic plasma membrane receptors of the P2 family. P2 receptors are divided into two types: ATP-gated nonselective cation channels (P2X) and G protein-coupled receptors (P2Y), the latter being activated by a broad range of purine and pyrimidine nucleotides (ATP, ADP, UTP, and UDP, among others). Purinergic signaling mechanisms are involved in numerous physiological events and pathophysiological conditions. Here, we address the growing body of evidence implicating purinergic signaling in male reproductive system functions. The life-long generation of fertile male germ cells is a highly complex, yet mechanistically poorly understood process. Given the relatively sparse innervation of the testis, spermatogenesis relies on both endocrine control and multi-directional paracrine communication. Therefore, a detailed understanding of such paracrine messengers, including ATP, is crucial to gain mechanistic insight into male reproduction.⁠.

Testicular adenosine acts as a pro-inflammatory molecule: role of testicular peritubular cells

Extracellular ATP has been described to be involved in inflammatory cytokine production by human testicular peritubular cells (HTPCs). The ectonucleotidases ENTPD1 and NT5E degrade ATP and have been reported in rodent testicular peritubular cells. We hypothesized that if a similar situation exists in human testis, ATP metabolites may contribute to cytokine production. Indeed, ENTPD1 and NT5E were found in situ and in vitro in HTPCs. Malachite green assays confirmed enzyme activities in HTPCs. Pharmacological inhibition of ENTPD1 (by POM-1) significantly reduced pro-inflammatory cytokines evoked by ATP treatment, suggesting that metabolites of ATP, including adenosine, are likely involved. We focused on adenosine and detected three of the four known adenosine receptors in HTPCs. One, A2B, was also found in situ in peritubular cells of human testicular sections. The A2B agonist BAY60-6583 significantly elevated levels of IL6 and CXCL8, a result also obtained with adenosine and its analogue NECA. Results of siRNA-mediated A2B down-regulation support a role of this receptor. In mouse peritubular cells, in contrast to HTPCs, all four of the known adenosine receptors were detected; when challenged with adenosine, cytokine expression levels significantly increased. Organotypic short-term testis cultures yielded comparable results and indicate an overall pro-inflammatory action of adenosine in the mouse testis. If transferable to the in vivo situation, our results may implicate that interference with the generation of ATP metabolites or interference with adenosine receptors could reduce inflammatory events in the testis. These novel insights may provide new avenues for treatment of sterile inflammation in male subfertility and infertility.

Testicular organoid formation is a property of immature somatic cells, which self-assemble and exhibit long-term hormone-responsive endocrine function

Testicular organoid models are tools to study testicular physiology, development, and spermatogenesis in vitro. However, few side-by-side comparisons of organoid generation method have been evaluated. Here, we directly tested whether the culture microenvironment is the prime determinant promoting testicular organoid self-assembly. Using Matrigel as a representative extracellular matrix (ECM), we compared multiple culture environments, 2D and 3D, ECM-free and ECM, for organoid self-assembly with immature murine testicular cells. De novo tissues were observed to self-assemble in all four culture environments tested within 72 h, however, these tissues only met requirements to be named organoids in 2D ECM and 3D ECM-free (3DF) culture methods. Based on these results, 3DF was selected for further study, and used to examine animal age as an independent variable. Organoid assembly was significantly delayed when using pubertal murine cells and entirely absent from adult murine and adult human cells. Organoid-conditioned medium and medium supplemented with 1% Matrigel did not improve organoid assembly in pubertal murine cells, but immature murine cells rescued the assembly of adult murine cells when cultured together as age-chimeric cell mixtures. In murine organoids cultured for 14 d, tubule-like structures exhibiting a highly biomimetic architecture were characterized, including some rare germ and spermatogonial stem cells. These structural organoids secreted high levels of testosterone and inhibin B over 12 weeks with preserved responsivity to gonadotropins. Collectively these studies, in which cellular self-assembly and organoid formation was achieved independent of the culture microenvironment, suggest that self-assembly is an innate property of immature testicular cells independent from, but capable of being promoted by, the culture environment. This study provides a template for studying testicular organoid self-assembly and endocrine function, and a platform for improving the engineering of functional testicular tissues.

Morphometric Evaluation of Spermatogenic Cells and Seminiferous Tubules and Exploration of Luteinizing Hormone Beta Polypeptide in Testis of Datong Yak

Simple Summary

Previous studies revealed that luteinizing hormone βeta polypeptide (LHB) plays an essential role in fertilization. Therefore, we aimed to confirm the importance of LHB in the testis of yak and to determine their association with male yak fertility. Histomorphological analysis of the testes is essential for predicting the fertilizing ability of the bull. To the best our knowledge, this is the first study to evaluate the micro anatomical changes and histometric alternation in testes of Datong yak. These findings could help to predict the sperm production capacity and to understand the specific molecular mechanisms of LHB during spermatogenesis.

Abstract

Histological examination of testes is essential for understanding infertility, sex development, and growth. Therefore, to understand the histomorphology of testes at different developmental stages, we performed hematoxylin and eosin staining of Yak testis. Our results revealed that the diameters of spermatogenic cells and their nuclei were significantly larger (p < 0.05) in the testis at six years compared to at six and 18 months. No significant difference was noted between 30 months and six years. The study was designed to compare the expression profile of LHB in Datong yak. The expression pattern of LHB was explored using quantitative PCR, semi-quantitative PCR, molecular bioinformatic, and Western blot analysis. Our observations indicated that expression of LHB was significantly higher (p < 0.05) in the testis of Datong yak. Western blotting indicated that the molecular mass of LHB protein was 16 kDa in yak. The protein encoded by yak LHB included conserved cysteine-knot domain regions. The high expression of LHB in testis indicated that LHB may be vital for the development of male gonads and the fertility of Datong yak.

Reproduction disrupts stem cell homeostasis in testes of aged male Drosophila via an induced microenvironment

Stem cells rely on instructive cues from their environment. Alterations in microenvironments might contribute to tissue dysfunction and disease pathogenesis. Germline stem cells (GSCs) and cyst stem cells (CySC) in Drosophila testes are normally maintained in the apical area by the testicular hub. In this study, we found that reproduction leads to accumulation of early differentiating daughters of CySCs and GSCs in the testes of aged male flies, due to hyperactivation of Jun-N-terminal kinase (JNK) signaling to maintain self-renewal gene expression in the differentiating cyst cells. JNK activity is normally required to maintain CySCs in the apical niche. A muscle sheath surrounds the Drosophila testis to maintain its long coiled structure. Importantly, reproduction triggers accumulation of the tumor necrosis factor (TNF) Eiger in the testis muscle to activate JNK signaling via the TNF receptor Grindelwald in the cyst cells. Reducing Eiger activity in the testis muscle sheath suppressed reproduction-induced differentiation defects, but had little effect on testis homeostasis of unmated males. Our results reveal that reproduction in males provokes a dramatic shift in the testicular microenvironment, which impairs tissue homeostasis and spermatogenesis in the testes.

Proper differentiation of stem cell progeny is necessary for preservation of tissue homeostasis. In Drosophila testes, somatic cyst cells derived from the cyst stem cells (CySCs) control the differentiation of the neighboring germ cells. Disruption of CySC daughter cyst cell differentiation leads to failure in sperm production. Interestingly, we found that reproduction triggers hyperactivation of Jun-N-terminal kinase (JNK) signaling to sustain CySC self-renewal gene expression in differentiating cyst cells, leading to accumulation of immature cyst cell and germ cells at the expense of mature cells in the testes of aged males. Endogenous JNK signaling is also required for CySC maintenance. Moreover, we found that the JNK signaling is hyperactivated via reproduction-induced accumulation of tumor necrosis factor (TNF) in testicular smooth muscle that surrounds the testis to support its long coiled structure. The reproduction-induced phenotypes were only observed in the testes of aged and mated males, but not in testes form young mated males or aged unmated males, indicating that it is a combined effect of reproduction and aging. Our results reveal that reproduction impedes sperm production in aged males, and identify testicular muscle as an inducible signaling center for spermatogenesis in Drosophila.

Microenvironmental signals govern the cellular identity of testicular macrophages

Testicular macrophages (TM) comprise the largest immune cell population in the mammalian testis. They are characterized by a subdued proinflammatory response upon adequate stimulation, and a polarization toward the immunoregulatory and immunotolerant M2 phenotype. This enables them to play a relevant role in supporting the archetypical functions of the testis, namely spermatogenesis and steroidogenesis. During infection, the characteristic blunted immune response of TM reflects the need for a delicate balance between a sufficiently strong reaction to counteract invading pathogens, and the prevention of excessive proinflammatory cytokine levels with the potential to disturb or destroy spermatogenesis. Local microenvironmental factors that determine the special phenotype of TM have just begun to be unraveled, and are discussed in this review.

The cell-cell junctions of mammalian testes: II. The lamellar smooth muscle monolayer cells of the peritubular wall are laterally connected by vertical adherens junctions-a novel architectonic cell-cell junction system

The testes of sexually mature males of six mammalian species (men, bulls, boars, rats, mice, guinea pigs) have been studied using biochemical as well as light and electron microscopical techniques, in particular immunolocalizations. In these tissues, the peritubular walls represent lamellar encasement structures wrapped around the seminiferous tubules as a bandage system of extracellular matrix layers, alternating with monolayers of very flat polyhedral "lamellar smooth muscle cells" (LSMCs), the number of which varies in different species from 1 to 5 or 6. These LSMCs are complete SMCs containing smooth muscle α-actin (SMA), myosin light and heavy chains, α-actinin, tropomyosin, smoothelin, intermediate-sized filament proteins desmin and/or vimentin, filamin, talin, dystrophin, caldesmon, calponin, and protein SM22α, often also cytokeratins 8 and 18. In the monolayers, the LSMCs are connected by adherens junctions (AJs) based on cadherin-11, in some species also with P-cadherin and/or E-cadherin, which are anchored in cytoplasmic plaques containing β-catenin and other armadillo proteins, in some species also striatin family proteins, protein myozap and/or LUMA. The LSMC cytoplasm is rich in myofilament bundles, which in many regions are packed in paracrystalline arrays, as well as in "dense bodies," "focal adhesions," and caveolae. In addition to some AJ-like end-on-end contacts, the LSMCs are laterally connected by numerous vertical AJ-like junctions located in variously sized and variously shaped, overlapping (alter super alterum) lamelliform cell protrusions. Consequently, the LSMCs of the peritubular wall monolayers are SMCs sensu stricto which are laterally connected by a novel architectonic system of arrays of vertical AJs located in overlapping cell protrusions.

ATP-mediated Events in Peritubular Cells Contribute to Sterile Testicular Inflammation

Peritubular myoid cells, which form the walls of seminiferous tubules in the testis, are functionally unexplored. While they transport sperm and contribute to the spermatogonial stem cell niche, specifically their emerging role in the immune surveillance of the testis and in male infertility remains to be studied. Recently, cytokine production and activation of Toll-like receptors (TLRs) were uncovered in cultured peritubular cells. We now show that human peritubular cells express purinergic receptors P2RX4 and P2RX7, which are functionally linked to TLRs, with P2RX4 being the prevalent ATP-gated ion channel. Subsequent ATP treatment of cultured peritubular cells resulted in up-regulated (pro-)inflammatory cytokine expression and secretion, while characteristic peritubular proteins, that is smooth muscle cell markers and extracellular matrix molecules, decreased. These findings indicate that extracellular ATP may act as danger molecule on peritubular cells, able to promote inflammatory responses in the testicular environment.

The development and functions of multiciliated epithelia

Multiciliated cells are epithelial cells that are in contact with bodily fluids and are required for the proper function of major organs including the brain, the respiratory system and the reproductive tracts. Their multiple motile cilia beat unidirectionally to remove particles of external origin from their surface and/or drive cells or fluids into the lumen of the organs. Multiciliated cells in the brain are produced once, almost exclusively during embryonic development, whereas in respiratory tracts and oviducts they regenerate throughout life. In this Review, we provide a cell-to-organ overview of multiciliated cells and highlight recent studies that have greatly increased our understanding of the mechanisms driving the development and function of these cells in vertebrates. We discuss cell fate determination and differentiation of multiciliated cells, and provide a comprehensive account of their locations and functions in mammals.

Seasonal Changes in the Immunolocalization of Cytoskeletal Proteins and Laminin in the Testis of the Black-Backed Jackal (Canis mesomelas)

Manipulation of the reproductive activity of jackals is dependent on a thorough understanding of the reproductive biology of this species. This study describes seasonal morphological changes in the adult testis of the black-backed jackal in relation to the immunoexpression of the basement membrane marker, laminin and the cytoskeletal proteins, cytokeratin, smooth muscle actin and vimentin. Laminin was immunolocalized in basement membranes surrounding seminiferous tubules, as well as in basement membranes associated with Leydig, peritubular myoid and vascular smooth muscle cells. Scalloped basement membranes enclosed seminiferous tubules in regressing testes. The seminiferous epithelium and interstitial tissue in all animals studied were cytokeratin immunonegative. Smooth muscle actin was demonstrated in vascular smooth muscle cells, as well as in peritubular myoid cells encircling seminiferous tubules. Vimentin immunoreactivity was exhibited in the cytoplasm of Sertoli cells, Leydig cells, vascular endothelial cells, vascular smooth muscle cells and fibrocytes. Vimentin immunostaining in Sertoli, Leydig and peritubular myoid cells varied depending on the functional state of the testis. The results of the study have shown that dramatic seasonal histological changes occur in the testes of the jackal. In addition, the use of immunohistochemistry accentuates these morphological changes.

Angiotensin II regulates testicular peritubular cell function via AT1 receptor: a specific situation in male infertility

We observed that peritubular myoid cells in the human testis are immunoreactive for angiotensin II (AngII) receptors (AT1R) and explored AngII actions in cultured human testicular peritubular cells (HTPCs). In response to AngII they contracted within minutes. The AT1R-blocker losartan blocked contraction, implying involvement of AngII and AT1R in intratesticular sperm transport. AngII also significantly increased IL-6 mRNA levels and IL-6 secretion within hours and losartan again prevented this action. This suggests involvement in inflammatory processes, which may play a role in male infertility. AngII can be generated locally by mast cell (MC)-derived chymase (CHY), which cleaves AngI. In testicular biopsies from infertile men we found abundant MCs, which express CHY, within the wall of seminiferous tubules. In contrast, CHY-positive MCs are hardly found in normal human testis. Testicular inflammatory events may fuel processes resulting in impaired spermatogenesis. Therefore therapeutic interference with MCs, CHY or AT1R might be novel options in male infertility.

Human testicular peritubular cells: more than meets the eye

In healthy men, several layers of inconspicuously flat cells and extracellular matrix (ECM) proteins build the wall of the seminiferous tubules. The cells of this wall, peritubular cells, are not well characterized. They are smooth-muscle-like and contractile and transport immotile sperm, a function important for male fertility. However, their full functional importance, especially their potential contribution to the paracrine regulation of the male gonad, is unknown. In men with impaired spermatogenesis, the architecture of the tubular wall is frequently altered. Deposits of ECM and morphological changes of peritubular cells imply that functions of peritubular cells may be fundamentally altered. To be able to study human peritubular cells and their functions, a culture method was established. It is based on small biopsies of patients with obstructive azoospermia but normal spermatogenesis (human testicular peritubular cells, HTPCs) and non-obstructive azoospermia, impaired spermatogenesis, and testicular fibrosis (HTPCFs). Results obtained from cellular studies and parallel examinations of biopsies provide insights into the repertoire of the secretion products, contractile properties, and plasticity of human peritubular cells. They produce ECM components, including the proteoglycan decorin, which may influence paracrine signaling between testicular cells. They may contribute to the spermatogonial stem cell niche via secreted factors. They are regulated by mast cell and macrophage products, and in response produce factors that can fuel inflammatory changes. They possess a high degree of plasticity, which results in hypertrophy and loss of contractile abilities. The data collectively indicate important roles of inconspicuous testicular peritubular cells in human male fertility and infertility.

Partial loss of contractile marker proteins in human testicular peritubular cells in infertility patients

Fibrotic remodelling of the testicular tubular wall is common in human male infertility caused by impaired spermatogenesis. We hypothesized that this morphological change bears witness of an underlying fundamentally altered state of the cells building this wall, that is, peritubular smooth muscle-like cells. This could include a loss of the contractile abilities of these cells and thus be a factor in male infertility. Immune cells are increased in the tubular wall in these cases, hence local immune cell-related factors, including a prostaglandin (PG) metabolite may be involved. To explore these points in the human, we used testicular biopsies, in which tubules with normal spermatogenesis and impaired spermatogenesis are next to each other [mixed atrophy (MA)], normal biopsies and cultured human testicular peritubular cells. Proteins essential for contraction, myosin heavy chain (MYH11), calponin (Cal) and relaxation, cGMP-dependent protein kinase 1 (cGKI), were readily detected by immunohistochemistry and were equally distributed in all peritubular cells of biopsies with normal spermatogenesis. In all biopsies, vascular smooth muscle cells also stained and served as important intrinsic controls, which showed that in MA samples when spermatogenesis was impaired, staining was restricted to only few peritubular cells or was absent. When spermatogenesis was normal, regular peritubular staining became obvious. This pattern suggests complex regulatory influences, which in face of the identical systemic hormonal situation in MA patients, are likely caused by the local testicular micromilieu. The PG metabolite 15dPGJ2 may represent such a factor and it reduced Cal protein levels in peritubular cells from patients with/without impaired spermatogenesis. The documented phenotypic switch of peritubular, smooth muscle-like cells in MA patients may impair the abilities of the afflicted seminiferous tubules to contract and relax and must now be considered as a part of the complex events in male infertility.

Post-hatch changes in the immunoexpression of desmin, smooth muscle actin and vimentin in the testicular capsule and interstitial tissue of the Japanese quail (Coturnix coturnix japonica)

The post-hatch development of immunoreactivity to desmin, smooth muscle actin (SMA) and vimentin in the testicular capsule and interstitial tissue of day-old to adult quails was described in this study. The tunica albuginea of the testicular capsule was composed mainly of myoid cells. A zonal arrangement of desmin and SMA immunostaining was observed in myoid cells of the tunica albuginea in 1- to 24-day-old quails. Immunostaining for SMA and desmin was uniform in the tunica albuginea of adult birds. Vimentin immunostaining in the testicular capsule was demonstrated in mesothelial cells, endothelial cells and fibroblasts. The interstitial tissue contained mesenchymal cells, peritubular myoid cells, Leydig cells and fibroblasts. Desmin-immunopositive mesenchymal cells were present in the interstitial tissue of 1- to 17-day-old quails. Peritubular myoid cells expressed strong desmin immunostaining in all developmental stages, while the intensity of SMA immunostaining increased with testicular maturation. Vimentin was demonstrated in Leydig cells and fibroblasts, while the peritubular myoid cells displayed strong vimentin immunostaining only in adult birds. Strong vimentin immunostaining was demonstrated in the endothelial cells of capsular and interstitial blood vessels. The tunica media of these blood vessels displayed desmin and SMA immunostaining. The results of the study have established that variability exists in the distribution and intensity of desmin, SMA and vimentin immunostaining in the testicular capsule and interstitial tissue of the post-hatch Japanese quail.

Estrogen regulation of the male reproductive tract in the frog, Rana esculenta: a role in Fra-1 activation in peritubular myoid cells and in sperm release

Endogenous and environmental estrogens have been proved to affect male reproduction in vertebrates. Both positive and negative effects in the regulation of the reproductive tract have been described. Since it is well known that amphibians represent a useful model to study several aspects concerning reproductive activity, we have taken advantage of the frog, Rana esculenta, to study the involvement of estrogens in sperm release. We show here that pituitary hormones increased the number of peritubular myoid cells (PMCs) expressing Fra-1 and induced testicular morphological changes related to sperm release. The estrogen antagonist ICI182-780 counteracted the hypophysis driven effects. In vivo and in vitro experiments demonstrated that 17beta-Estradiol acted directly on the testis to switch-on Fra-1 in PMCs. Furthermore, impairment of estrogen activity significantly reduced sperm release mainly affecting the detachment of spermatozoa from Sertoli cells (spermiation). Therefore, estrogens can be considered a new entry in the list of substances involved in spermiation.

Morphological and immunohistochemical study of testicular capsule and peritubular tissue of emu (Dromaius novaehollandiae) and ostrich (Struthio camelus)

The testicular capsule and peritubular boundary tissue of the emu and ostrich, as typical representatives of ratite birds, were studied in sexually mature and active birds. The testicular capsule was much thicker (578.1+/-73.4 microm for the free surface of the ostrich testis, and 176.2+/-57.5 microm for the emu) than those of members of the Galloanserae. The cellular composition of both testicular capsule and peritubular tissue was similar generally to that of members of the previously studied Galloanserae and of mammals. The tunica albuginea of the testicular capsule mainly comprised smooth-muscle-like or myoid cells mostly running in one direction and occurring in one main mass. Unlike the Galloanserae, the tunica albuginea contained more collagen fibres than smooth muscle cells, especially in the ostrich. Peritubular tissue was similarly composed of smooth-muscle-like cells distributed in several layers. Actin microfilaments and desmin and vimentin intermediate filaments were variably immunoexpressed in these two tissue types in both birds, with a clear dichotomy in the peritubular tissue. Thus, taken together with studies of some members of the Galloanserae, avian testes clearly contain a morphological mechanism that is represented partly by the smooth muscle cells of the testicular capsule and peritubular tissue for transporting the testicular fluid, which is usually copious in birds, and its cellular content from the testis into the excurrent duct system; this mechanism is similar to that found in mammals.

The testicular capsule and peritubular tissue of birds: morphometry, histology, ultrastructure and immunohistochemistry

The testicular capsule was studied histologically, morphometrically, ultrastructurally and immunohistochemically in the Japanese quail, domestic fowl, turkey and duck (all members of the Galloanserae). The testicular capsule was, relative to mammals, thin, being 81.5 +/- 13.7 microm in the quail, 91.7 +/- 6.2 microm in the domestic fowl, 104.5 +/- 29.8 microm in the turkey and 91.8 +/- 18.9 microm in the duck. The orchido-epididymal border (hilus) of the capsule was much thicker than elsewhere in all birds (from 233.7 +/- 50.7 microm in the duck to 550.0 +/- 147.3 microm thick in the turkey). The testicular capsule, other than the tunica serosa and tunica vasculosa, comprised, in the main, smooth muscle-like or myoid cells running mainly in one direction, and disposed in one main mass. Peritubular tissue was similarly composed of smooth muscle-like cells disposed in several layers. Actin and desmin intermediate filaments were immunolocalized in the inner cellular layers of the capsule in the quail, domestic fowl and duck, but uniformly in the turkey. Vimentin intermediate filament immunoreaction in the capsule was moderately and uniformly positive in the testicular capsule of only the quail. Actin and desmin, but not vimentin (except very faintly in the turkey) or cytokeratin, were immunolocalized in the peritubular tissue of all birds. The results therefore establish, or complement, some previous observations that these birds have contractile cells in their testicular capsule and peritubular tissue, whose function probably includes the transport of testicular fluid into the excurrent duct system.

Oxytocin and the human prostate in health and disease

Oxytocin is a peptide hormone produced by the neurohypophysis. The discovery that the peptide is produced locally within the male and female reproductive tracts has raised the possibility that oxytocin may have paracrine and autocrine actions outside of the nervous system. Oxytocin and its receptor have been identified in the human prostate. The prostate is an androgen-dependent organ whose function is to secrete components of the seminal fluid. Oxytocin has been shown to modulate contractility of prostate tissue and also to regulate local concentrations of the biologically active androgens. Oxytocin has also been shown to regulate cell growth. Prostate disease is common and results from abnormal growth of the gland. Oxytocin concentrations are altered in both benign and malignant prostate diseases and in vitro studies suggest that the peptide may be involved in the pathophysiology of these diseases.

Documented and anecdotal effects of certain pharmaceutical agents used to enhance semen quality in the dog

Prostaglandin F(2alpha), gonadotropin releasing hormone, cabergoline and various nutriceuticals have all been recommended by reproductive practitioners to improve sperm motility and morphology and to increase sperm numbers in the ejaculate of the dog. Increasing sperm quantity and quality in the canine ejaculate would benefit all assisted reproductive techniques used in this species. The purpose of this manuscript is to review the documented and anecdotal effects of certain pharmaceuticals used to enhance semen quality in the dog.

Oxytocin--its role in male reproduction and new potential therapeutic uses

Oxytocin (OT) is traditionally thought of as a "female" neurohypophysis hormone due to its role in parturition and milk ejection. However, OT is recognized as having endocrine and paracrine roles in male reproduction. At ejaculation, a burst of OT is released from the neurohypophysis into the systemic circulation and stimulates contractions of the reproductive tract aiding sperm release. There is conclusive evidence that OT is synthesized within the mammalian testis, epididymis and prostate and the presence of OT receptors (OTRs) through the reproductive tract supports a local action for this peptide. OT has a paracrine role in stimulating contractility of the seminiferous tubules, epididymis and the prostate gland. Interestingly, OT has also been shown to modulate androgen levels in these tissues via stimulation of the conversion of testosterone to dihydrotestostone (DHT) by 5alpha-reductase. The elucidation of OT's role in male reproduction has suggested a number of potential therapeutic uses for this hormone. Exogenous administration of OT has, in some cases, been shown to increase the numbers of ejaculated sperm, possibly by stimulating contractions of the reproductive tract and thus aiding sperm passage. Within the prostate, OT has been shown to affect gland growth both directly and via its interaction with androgen metabolism. Prostate pathologies due to unregulated cell proliferation/growth, such as benign prostatic hyperplasia and cancer, are unfortunately very common and few effective treatments are available. Greater understanding of paracrine growth mediators, such as OT, is likely to provide new mechanisms for treating such pathologies.

Platelet-derived growth factor-BB stimulates hypertrophy of peritubular smooth muscle cells from rat testis in primary cultures

The tunica propria of seminiferous tubules contains a particular type of smooth muscle cell (myoid cells) arranged in a contractile epithelioid layer that is responsible for sperm and tubular fluid flow. Unlike other types of smooth muscle (SM) cells, highly purified populations of peritubular smooth muscle cells (PSMC) survive and maintain their contractile phenotype in primary cultures in controlled conditions. We used this culture model to investigate the response of the SM contractile phenotype to prolonged exposure to platelet-derived growth factor (PDGF), one of the main factors involved in vascular SM pathologies. We observed that 4-day continuous exposure of PSMC to PDGF-BB at nanomolar concentrations in plain medium enhances contractile phenotype traits and induces cell hypertrophy without inducing proliferation. In Northern and Western blotting experiments, SM-alpha-actin transcript and protein were found to be markedly increased in the PDGF-BB-treated samples, which is in line with the formation of conspicuous SM-alpha-actin-containing stress fibers. Moreover, binding sites for endothelin-1 were increased, and the calcium response to the contractile agonist, determined in single fura-2-loaded cells, was enhanced. In response to PDGF-BB, the cells underwent immediate, transient contraction, as seen in a scanning electron microscope, followed by a gradual increase in size, as evaluated by cytofluorometry, and enhancement of protein synthesis. The observed pattern of response to PDGF-BB was not accompanied by cell proliferation, as assessed by [3H]thymidine incorporation and direct cell counts. Unlike other SM cell types, in which proliferation and loss of contractile traits are induced by PDGF, chronic treatment of PSMC with this growth factor results in hypertrophy rather than hyperplasia.

Cyclic expression of endothelin-converting enzyme-1 mediates the functional regulation of seminiferous tubule contraction

The potent smooth muscle agonist endothelin-1 (ET-1) is involved in the local control of seminiferous tubule contractility, which results in the forward propulsion of tubular fluid and spermatozoa, through its action on peritubular myoid cells. ET-1, known to be produced in the seminiferous epithelium by Sertoli cells, is derived from the inactive intermediate big endothelin-1 (big ET-1) through a specific cleavage operated by the endothelin-converting enzyme (ECE), a membrane-bound metalloprotease with ectoenzymatic activity. The data presented suggest that the timing of seminiferous tubule contractility is controlled locally by the cyclic interplay between different cell types. We have studied the expression of ECE by Sertoli cells and used myoid cell cultures and seminiferous tubule explants to monitor the biological activity of the enzymatic reaction product. Northern blot analysis showed that ECE-1 (and not ECE-2) is specifically expressed in Sertoli cells; competitive enzyme immunoassay of ET production showed that Sertoli cell monolayers are capable of cleaving big ET-1, an activity inhibited by the ECE inhibitor phosphoramidon. Microfluorimetric analysis of intracellular calcium mobilization in single cells showed that myoid cells do not respond to big endothelin, nor to Sertoli cell plain medium, but to the medium conditioned by Sertoli cells in the presence of big ET-1, resulting in cell contraction and desensitization to further ET-1 stimulation; in situ hybridization analysis shows regional differences in ECE expression, suggesting that pulsatile production of endothelin by Sertoli cells (at specific "stages" of the seminiferous epithelium) may regulate the cyclicity of tubular contraction; when viewed in a scanning electron microscope, segments of seminiferous tubules containing the specific stages characterized by high expression of ECE were observed to contract in response to big ET-1, whereas stages with low ECE expression remained virtually unaffected. These data indicate that endothelin-mediated spatiotemporal control of rhythmic tubular contractility might be operated by Sertoli cells through the cyclic expression of ECE-1, which is, in turn, dependent upon the timing of spermatogenesis.

Effect of experimental cryptorchidism on alpha 1-adrenergic receptors of rat testis

Alpha 1-adrenergic receptors play an important role in the transport of spermatozoa through seminiferous tubules to the efferent ducts leading to the epididymis. The density of alpha 1-adrenergic receptors in adult Sprague-Dawley rat testis before and during 14 days of experimental cryptorchidism was determined by binding assays with [3H]prazosin in membrane preparations. The number of maximal binding sites (Bmax) per milligram protein began to increase at 7 days after surgery (p < .05). The testicular weight and diameter of seminiferous tubules began to decrease at 5 days after surgery (p < .01). However, Bmax per testis did not differ before and during cryptorchidism. This study demonstrates that the density of alpha 1-adrenergic receptors in rat testis is not affected by cryptorchidism.

Effects of vanadate, ouabain and amiloride on the contraction of the rat testicular capsule to oxytocin

1. The modification of the contraction of the rat testicular capsule to oxytocin (OT) by vanadate (0.7, 7 and 70 microM), ouabain (0.1 mM), and amiloride (10 microM to 1 mM) have been studied. 2. OT (1 nM-6 microM) and vanadate (10 microM-3 mM) induced contraction of the rat testicular capsule in a dose-dependent way (ED50: 188 +/- 66 nM and 82.8 +/- 7.4 microM, respectively). 3. Vanadate (0.7, 7 and 70 microM) and ouabain (0.1 mM) increases the contractile effect of OT (50 and 200 nM). 4. Amiloride (10 microM-1 mM) inhibit, in a dose-dependent way, the OT-contraction. 5. Amiloride (10 microM or 50 microM) block the ouabain but not the vanadate potentiation to OT.

Interactions between oxytocin- and calcium-modifying agents in the rat testicular capsule in vitro

We have studied the effect of drugs which affect the movement of calcium on the contractions induced by 50 and 200 nM oxytocin in the isolated testicular capsule of the rat. The ED50 for oxytocin in this preparation was 188 (+/- 66 S.E.) nM and the maximal contraction induced by oxytocin was smaller than that obtained with 10 microM of the calcium ionophore, A23187. Lanthanum (10 mM), cobalt (2 mM), EGTA (3.5 and 5 nM, 30 s exposure) and a decrease in the calcium concentration of the medium reduced the oxytocin response. The response was completely abolished after prolonged incubation with EGTA (2 mM) in a calcium-free medium. The calcium blocking agents, nifedipine and flunarizine, and the agonist, Bay K 8644, did not modify the responses to oxytocin. Verapamil, at possibly non-specific doses (10 microM), reduced the contractions while diltiazem (0.1 mM), in a prazosin (10 microM)-resistant way, and nickel (0.1 mM) increased them. Both modifiers of intracellular calcium that were used namely TMB-8 (10 microM), in a calcium-free medium, and dantrolene sodium (10 and 30 microM), with and without calcium in the medium, decreased the oxytocin response. On the whole, it seems as if both intra- and extracellular calcium were involved in the contractile effect of oxytocin, although extracellular calcium does not seem to gain access to the cell through voltage-dependent calcium channels sensitive to selective calcium entry blockers.

Peritubular myoid cells of human and rat testis are smooth muscle cells that contain desmin-type intermediate filaments

We studied the cytoskeletal composition of human and rat testicular myoid cells by using immunofluorescence microscopy with polyclonal and monoclonal antibodies. In adult human and rat testis, the peritubular myoid cell layer was brightly positive for desmin, the muscle type of intermediate filament protein, and a faint reaction was also seen with antibodies to vimentin, the intermediate filament protein of fibroblasts and diverse other mesenchymal cells. The desmin-positive myoid cell layer could already be identified in newborn rat testis but was more compact in appearance 23 days after birth. Both squash preparations and cultured cells from adult rat seminiferous tubules revealed distinct cell populations positive for desmin. The adult myoid cells of both species also showed a strong reaction with antibodies to myosin and p230, a nonerythroid avian alpha-spectrin analogue. The immunostaining results could be confirmed by the western blotting technique: Experiments with isolated seminiferous tubules showed a specific reaction with a 55,000-dalton and a 58,000-dalton polypeptide when desmin and vimentin antibodies were used, respectively. The present results show that the peritubular myoid cells are genuine smooth muscle cells with desmin-type intermediate filament cytoskeleton and suggest that these cells can be identified by this feature before their ultrastructural maturation.

Prostaglandin dehydrogenase activity of rat and rabbit testicular tissues and accessory glands before and after castration

Rat reproductive tissues contained both 15-hydroxy-prostaglandin dehydrogenase (PGDH) and delta 13-reductase activities, while rabbit tissues exhibited only PGDH activity. In the rat, delta 13-reductase activity was absent in those tissues that had a high specific activity of PGDH and was present in those tissues with a low specific activity. Total specific activity of PGDH was greatest in the testicular capsule, whereas total activity was greatest in the testicular parenchyma of both species. Total PGDH activity was highest in rat seminal vesicles, where it was second only to the testicular parenchyma. Castration significantly increased PGDH activity of the epididymis, prostate, and seminal vesicles of rats, while delta 13-reductase activity disappeared from those tissues. The specific activity of PGDH was greater in the rat than in the rabbit, except for the testicular parenchyma of the rabbit. The greater PGDH activity in rat testicular capsules, compared to those of the rabbit, correlated well with diminished contractility of the rat capsule. PGDH activity of the interstitial cells correlated well with the role of prostaglandins in androgen synthesis.

Regulation of rat caput epididymidis contractility by prostaglandins

Mechanical activity of the rat caput epididymidis in vitro was recorded using a videomicrography system. The effects of prostaglandin (PG)F2 alpha, PGE2, and aspirin on caput epididymidis contractility were determined by measuring the frequency of contraction, luminal diameter, and amplitude of contraction at various concentrations of each test compound in vitro. PGF2 alpha stimulated contractility of the tubules at physiological concentrations, while PGE2 reduced contractility. Aspirin strongly inhibited contractility at concentrations of 10(-3) and 10(-2)M. Endogenous levels of PGF2 alpha and PGE were determined for rat testes, caput, corpus, and cauda epididymidis and vas deferens. While the concentrations of PGE were consistently higher than those of PGF2 alpha, both compounds were relatively low in the testes, high in the vas deferens, and intermediate throughout the epididymis. Results from these experiments strongly suggest that PGs are important regulators of proximal epididymidis contractions and thus may regulate sperm transport through that organ.

Temperature-induced alterations in rabbit testicular contractility in vitro

Rabbit testicular contractions and intratesticular pressure were recorded in vitro as temperature was increased from 33 to 38 degrees C. The response of the testicular capsule to several physiological agents was quantified at 35, 37 and 38 degrees C. A corresponding increase in intratesticular pressure was observed with each contraction. Uniform intratesticular pressures developed in normal spontaneous autorhythmic testicular preparations. The force of capsular contractions increased slightly from 33 to 35 degrees C, but decreased markedly with temperatures above 35 degrees C. Intratesticular pressure increased linearly with increased force of contractions to a maximum of 143 mg of tension. As intratesticular pressure increased, the amplitude of contractions decreased. Marked irregularities in force and frequency of contractions occurred with temperatures above 38 degrees C. Increasing testicular temperature from 35 to 37 degrees C and from 37 to 38 degrees C both markedly reduced the effectiveness of acetylcholine by 58 and 71%, serotonin by 52 and 71%, epinephrine by 41 and 45%, PGF2 alpha by 37 and 54%, histamine by 33 and 54% and bradykinin by 29 and 43%, respectively, in their ability to increase tone of the capsule.

Age changes in rat testicular capsular and parenchymal delta 13-reductase and 15-hydroxyprostaglandin dehydrogenase activities

Prostaglandin dehydrogenase (PGDH), delta 13-reductase, and total PGDH activities (the sum of the first two activities) were measured in rat testicular parenchymal and capsular preparations from 11 through 81 days of age. delta-13 Reductase activity closely paralleled PGDH activity and was substrate dependent except for the parenchymal activity at 61 and 81 days of age when something appeared to enhance its activity. All three activities, when expressed on a per milligram of tissue basis, were elevated at 11 days postpartum and then decreased to a low value at 21 days of age for the parenchyma and 21-32 days of age for the capsule. The elevated activity at 11 days of age suggested a possible elevation of enzyme activity by placental gonadotropins or possibly progesterone. Maximal, activity was observed at 51 days of age for the parenchyma and 61 days for the capsules with diminished activities observed with advancing age except for the parenchymal delta 13-reductase activity. On a per milligram of tissue basis, the capsule demonstrated more enzyme activity than did the parenchyma with maximal activities being observed at 51 days of age. Possible control mechanisms were the following: substrate induction, gonadotropins, testosterone, or those factors regulating testosterone secretion.

Contractility of seminiferous tubules as related to sperm transport in the male

The mammalian testes have several mechanisms to propel the nonmotile spermatozoa in the seminiferous tubules through the rete testis into the epididymis. These include (a) contractions of the testicular capsule and the seminiferous tubules and (b) fluid flow through the excurrent ducts resulting from active transport of fluids and electrolyte into the seminiferous tubules from the extracellular space. The efflux of fluids and sperm from the testis appears to closely parallel spermiation. An increased output of fluid may result from prostaglandins (PGF2 alpha) and possibly oxytocin (not all species respond to oxytocin) as a result of capsular contractions compressing and expelling the fluid from the tubules. Seminiferous tubular contractions do not result from nervous stimulation but are linked to PGs and cyclic nucleotide generation. They are regulated to some extent by androgens and the lesser response of the tubules to 5 alpha-dihydrotestosterone compared to testosterone can be explained by their interaction with androgen binding protein and their action on phospholipase A2 activity for PG synthesis.

Structural evidence for two different testicular types in teleost fishes

Testicular structure in Salmoniformes, Perciformes, Cypriniformes, and Atheriniformes has been examined and reinterpreted on the basis of two different tubular types, distinguished from each other by the intratubular distribution of spermatogonia. In the salmoniform, perciform, and cypriniform teleosts studied, spermatogonia are distributed along the entire length of the testicular tubules. However, in the atheriniform teleosts spermatogonia are restricted to the distal end of the tubule. Sperm development in teleosts is cystic, cysts being comprised of Sertoli-cell processes. In both testicular types described, Sertoli cells phagocytize spermatid residual bodies. Together with the germ cells, they comprise the only intratubular cell types within the teleostean testis. Boundary cells are located immediately outside of the tubule basement membrane. They do not form a complete layer over the tubule surface; therefore, interstitial Leydig cells and blood vessels may border directly upon the tubular basement membrane.

Seminiferous tubule hypercurvature: A newly recognised common syndrome of human male infertility

Testicular biopsy specimens from 42 of a series of 70 consecutive cases of primary male infertility and from 25 normal controls were morphometrically analysed. Although all the specimens from infertile males were normal by conventional histological standards, stereological measures of curvature in histological sections showed that cases of idiopathic male infertility had an abnormally increased curvature of seminiferous tubules.