Comparison of androgen receptor and oestrogen receptor beta immunoexpression in the testes of the common marmoset (Callithrix jacchus) from birth to adulthood: low androgen receptor immunoexpression in Sertoli cells during the neonatal increase in testosterone concentrations

Functional and molecular characterization of a non-human primate model of autism spectrum disorder shows similarity with the human disease

Autism spectrum disorder (ASD) is a multifactorial disorder with characteristic synaptic and gene expression changes. Early intervention during childhood is thought to benefit prognosis. Here, we examined the changes in cortical synaptogenesis, synaptic function, and gene expression from birth to the juvenile stage in a marmoset model of ASD induced by valproic acid (VPA) treatment. Early postnatally, synaptogenesis was reduced in this model, while juvenile-age VPA-treated marmosets showed increased synaptogenesis, similar to observations in human tissue. During infancy, synaptic plasticity transiently increased and was associated with altered vocalization. Synaptogenesis-related genes were downregulated early postnatally. At three months of age, the differentially expressed genes were associated with circuit remodeling, similar to the expression changes observed in humans. In summary, we provide a functional and molecular characterization of a non-human primate model of ASD, highlighting its similarity to features observed in human ASD.

The Role of Androgen Signaling in Male Sexual Development at Puberty

Puberty is characterized by major changes in the anatomy and function of reproductive organs. Androgen activity is low before puberty, but during pubertal development, the testes resume the production of androgens. Major physiological changes occur in the testicular cell compartments in response to the increase in intratesticular testosterone concentrations and androgen receptor expression. Androgen activity also impacts on the internal and external genitalia. In target cells, androgens signal through a classical and a nonclassical pathway. This review addresses the most recent advances in the knowledge of the role of androgen signaling in postnatal male sexual development, with a special emphasis on human puberty.

Testis Development

Production of sperm and androgens is the main function of the testis. This depends on normal development of both testicular somatic cells and germ cells. A genetic program initiated from the Y chromosome gene sex-determining region Y (SRY) directs somatic cell specification to Sertoli cells that orchestrate further development. They first guide fetal germ cell differentiation toward spermatogenic destiny and then take care of the full service to spermatogenic cells during spermatogenesis. The number of Sertoli cells sets the limits of sperm production. Leydig cells secrete androgens that determine masculine development. Testis development does not depend on germ cells; that is, testicular somatic cells also develop in the absence of germ cells, and the testis can produce testosterone normally to induce full masculinization in these men. In contrast, spermatogenic cell development is totally dependent on somatic cells. We herein review germ cell differentiation from primordial germ cells to spermatogonia and development of the supporting somatic cells. Testicular descent to scrota is necessary for normal spermatogenesis, and cryptorchidism is the most common male birth defect. This is a mild form of a disorder of sex differentiation. Multiple genetic reasons for more severe forms of disorders of sex differentiation have been revealed during the last decades, and these are described along with the description of molecular regulation of testis development.

Segmented Iba1-Positive Processes of Microglia in Autism Model Marmosets

Autism spectrum disorder (ASD) is one of the most widespread neurodevelopmental disorders, characterized by impairment in social interactions, and restricted stereotyped behaviors. Using immunohistochemistry and positron emission tomography (PET), several studies have provided evidence of the existence of activated microglia in ASD patients. Recently, we developed an animal model of ASD using the new world monkey common marmoset (Callithrix jacchus) and demonstrated ASD-like social impairment after the in utero administration of valproic acid (VPA). To characterize microglia in this marmoset model of ASD from early toddler to adult, morphological analyses of microglia in VPA marmosets and age-matched unexposed (UE) marmosets were performed using immunohistochemistry for microglia-specific markers, Iba1, and P2RY12. The most robust morphological difference between VPA marmosets and UE marmosets throughout the life span evaluated were the microglia processes in VPA marmosets being frequently segmented by thin and faintly Iba1-positive structures. The segmentation of microglial processes was only rarely observed in UE marmosets. This feature of segmentation of microglial processes in VPA marmosets can also be observed in images from previous studies on ASD conducted in humans and animal models. Apoptotic cells have been shown to have segmented processes. Therefore, our results might suggest that microglia in patients and animals with ASD symptoms could frequently be in the apoptotic phase with high turnover rates of microglia found in some pathological conditions.

Testosterone augments FSH signaling by upregulating the expression and activity of FSH-Receptor in Pubertal Primate Sertoli cells

The synergistic actions of Testosterone (T) and FSH via testicular Sertoli cells (Sc) regulate male fertility. We have previously reported that the actions of these hormones (T and FSH) in infant monkey testes are restricted only to the expansion of Sc and spermatogonial cells. The robust differentiation of male Germ cells (Gc) occurs after pubertal maturation of testis. The present study was aimed to investigate the molecular basis of the synergy between T and FSH action in pubertal primate (Macaca mulatta) Sc. Using primary Sc culture, we here have demonstrated that T (but not FSH) downregulated AMH and Inhibin-β-B (INHBB) mRNAs in pubertal Sc. We also found that, prolonged stimulation of T in pubertal Sc significantly elevated the expression of genes involved in FSH signaling pathway like FSH-Receptor (FSHR), GNAS and RIC8B, and this was associated with a rise in cAMP production. T also augmented FSH induced expression of genes like SCF, GDNF, ABP and Transferrin (TF) in pubertal Sc. We therefore conclude that T acts in synergy with FSH signaling in pubertal Sc. Such a coordinated network of hormonal signaling in Sc may facilitate the timely onset of the first spermatogenic wave in pubertal primates and is responsible for quantitatively and qualitatively normal spermatogenesis.

Cancer treatment in childhood and testicular function: the importance of the somatic environment

Testicular function and future fertility may be affected by cancer treatment during childhood. Whilst survival of the germ (stem) cells is critical for ensuring the potential for fertility in these patients, the somatic cell populations also play a crucial role in providing a suitable environment to support germ cell maintenance and subsequent development. Regulation of the spermatogonial germ-stem cell niche involves many signalling pathways with hormonal influence from the hypothalamo-pituitary-gonadal axis. In this review, we describe the somatic cell populations that comprise the testicular germ-stem cell niche in humans and how they may be affected by cancer treatment during childhood. We also discuss the experimental models that may be utilized to manipulate the somatic environment and report the results of studies that investigate the potential role of somatic cells in the protection of the germ cells in the testis from cancer treatment.

Male germline stem cells in non-human primates

Over the past few decades, several studies have attempted to decipher the biology of mammalian germline stem cells (GSCs). These studies provide evidence that regulatory mechanisms for germ cell specification and migration are evolutionarily conserved across species. The characteristics and functions of primate GSCs are highly distinct from rodent species; therefore the findings from rodent models cannot be extrapolated to primates. Due to limited availability of human embryonic and testicular samples for research purposes, two non-human primate models (marmoset and macaque monkeys) are extensively employed to understand human germline development and differentiation. This review provides a broader introduction to the in vivo and in vitro germline stem cell terminology from primordial to differentiating germ cells. Primordial germ cells (PGCs) are the most immature germ cells colonizing the gonad prior to sex differentiation into testes or ovaries. PGC specification and migratory patterns among different primate species are compared in the review. It also reports the distinctions and similarities in expression patterns of pluripotency markers (OCT4A, NANOG, SALL4 and LIN28) during embryonic developmental stages, among marmosets, macaques and humans. This review presents a comparative summary with immunohistochemical and molecular evidence of germ cell marker expression patterns during postnatal developmental stages, among humans and non-human primates. Furthermore, it reports findings from the recent literature investigating the plasticity behavior of germ cells and stem cells in other organs of humans and monkeys. The use of non-human primate models would enable bridging the knowledge gap in primate GSC research and understanding the mechanisms involved in germline development. Reported similarities in regulatory mechanisms and germ cell expression profile in primates demonstrate the preclinical significance of monkey models for development of human fertility preservation strategies.

Endocrine control of spermatogenesis: Role of FSH and LH/ testosterone

Evaluation of testicular functions (production of sperm and androgens) is an important aspect of preclinical safety assessment and testicular toxicity is comparatively far more common than ovarian toxicity. This chapter focuses (1) on the histological sequelae of disturbed reproductive endocrinology in rat, dog and nonhuman primates and (2) provides a review of our current understanding of the roles of gonadotropins and androgens. The response of the rodent testis to endocrine disturbances is clearly different from that of dog and primates with different germ cell types and spermatogenic stages being affected initially and also that the end-stage spermatogenic involution is more pronounced in dog and primates compared to rodents. Luteinizing hormone (LH)/testosterone and follicle-stimulating hormone (FSH) are the pivotal endocrine factors controlling testicular functions. The relative importance of either hormone is somewhat different between rodents and primates. Generally, however, both LH/testosterone and FSH are necessary for quantitatively normal spermatogenesis, at least in non-seasonal species.

Mini-puberty and true puberty: differences in testicular function

The ontogeny of the hypothalamic-pituitary-gonadal axis is particularly characterised by incomplete functional maturation in utero and during early postnatal life, followed by functional regression and partial quiescence during childhood, and subsequently by final complete maturation during puberty. This review addresses the distinctive features of testis developmental physiology--especially in the seminiferous tubule compartment--which explain the differences observed in testicular function and its disorders between the early postnatal activation period--which many authors call "mini-puberty"--and canonical puberty.

Receptors and signaling pathways involved in proliferation and differentiation of Sertoli cells

The identification of the hormones and other factors regulating Sertoli cell survival, proliferation, and maturation in neonatal, peripubertal, and pubertal life remains one of the most critical questions in testicular biology. The regulation of Sertoli cell proliferation and differentiation is thought to be controlled by cell-cell junctions and a set of circulating and local hormones and growth factors. In this review, we will focus on receptors and intracellular signaling pathways activated by androgen, follicle-stimulating hormone, thyroid hormone, activin, retinoids, insulin, insulin-like growth factor, relaxin, and estrogen, with special emphasis on estrogen receptors. Estrogen receptors activate intracellular signaling pathways that converge on cell cycle and transcription factors and play a role in the regulation of Sertoli cell proliferation and differentiation.

Status of the down-regulated canine testis using two different GNRH agonist implants in comparison with the juvenile testis

Testicular function in the dog was down-regulated using two different GNRH agonist implants, with adult and juvenile testes serving as controls. Treatment resulted in an increased percentage of the interstitial area and decreased area of Leydig cell nuclei. Expression of StAR and the steroidogenic enzymes cytochrome P450 side-chain cleavage enzyme (P450scc, CYP11A1) and cytochrome P450 17α-hydroxylase-17,20-lyase (P450c17, CYP17A1) in Leydig cells was blocked at the mRNA and protein level, showing no differences between the two agonists. Staining for androgen receptor (AR) by immunohistochemistry was positive in Sertoli, Leydig and peritubular cells and some spermatogonia, with in situ hybridization confirming expression in Sertoli cells. At the mRNA level, expression of AR was not affected; however, translation was blocked (reduced percentage of AR-positive Sertoli cells), with the number of nuclei in basal position being decreased. In the juvenile testes, mRNA expression of StAR, CYP11A1 and CYP17A1 was higher compared with the other groups but distinctly lower for the AR. At the protein level, the expression was at the limit of detection for StAR; AR-positive Sertoli cells were not detected. Our observations show that the down-regulated testis is different from the juvenile one rather resembling the testicular status in seasonal breeders out of season.

Sertoli cell androgen receptor expression regulates temporal fetal and adult Leydig cell differentiation, function, and population size

We recently created a mouse model displaying precocious Sertoli cell (SC) and spermatogenic development induced by SC-specific transgenic androgen receptor expression (TgSCAR). Here we reveal that TgSCAR regulates the development, function, and absolute number of Leydig cells (LCs). Total fetal and adult type LC numbers were reduced in postnatal and adult TgSCAR vs control testes, despite normal circulating LH levels. Normal LC to SC ratios found in TgSCAR testes indicate that SC androgen receptor (SCAR)-mediated activity confers a quorum-dependent relationship between total SC and LC numbers. TgSCAR enhanced LC differentiation, shown by elevated ratios of advanced to immature LC types, and reduced LC proliferation in postnatal TgSCAR vs control testes. Postnatal TgSCAR testes displayed up-regulated expression of coupled ligand-receptor transcripts (Amh-Amhr2, Dhh-Ptch1, Pdgfa-Pdgfra) for potential SCAR-stimulated paracrine pathways, which may coordinate LC differentiation. Neonatal TgSCAR testes displayed normal T and dihydrotestosterone levels despite differential changes to steroidogenic gene expression, with down-regulated Star, Cyp11a1, and Cyp17a1 expression contrasting with up-regulated Hsd3b1, Hsd17b3, and Srd5a1 expression. TgSCAR males also displayed elevated postnatal and normal adult serum testosterone levels, despite reduced LC numbers. Enhanced adult-type LC steroidogenic output was revealed by increased pubertal testicular T, dihydrotestosterone, 3α-diol and 3β-diol levels per LC and up-regulated steroidogenic gene (Nr5a1, Lhr, Cyp11a1, Cyp17a1, Hsd3b6, Srd5a1) expression in pubertal or adult TgSCAR vs control males, suggesting regulatory mechanisms maintain androgen levels independently of absolute LC numbers. Our unique gain-of-function TgSCAR model has revealed that SCAR activity controls temporal LC differentiation, steroidogenic function, and population size.

Postnatal development of layer III pyramidal cells in the primary visual, inferior temporal, and prefrontal cortices of the marmoset

Abnormalities in the processes of the generation and/or pruning of dendritic spines have been implicated in several mental disorders including autism and schizophrenia. We have chosen to examine the common marmoset (Callithrix jacchus) as a primate model to explore the processes. As a first step, we studied the postnatal development of basal dendritic trees and spines of layer-III pyramidal cells in the primary visual sensory cortex (V1), a visual association cortex (inferior temporal area, TE), and a prefrontal cortex (area 12, PFC). Basal dendrites in all three areas were longer in adulthood compared with those in the newborn. In particular, rapid dendritic growth occurred in both TE and PFC around the second postnatal month. This early growth spurt resulted in much larger dendritic arbors in TE and PFC than in V1. The density of the spines along the dendrites peaked at 3 months of age and declined afterwards in all three areas: the degree of spine pruning being greater in V1 than in TE and PFC. The estimates of the total numbers of spines in the basal dendrites of a single pyramidal cell were larger in TE and PFC than in V1 throughout development and peaked around 3 months after birth in all three areas. These developmental profiles of spines and dendrites will help in determining assay points for the screening of molecules involved in spinogenesis and pruning in the marmoset cortex.

Perinatal germ cell development and differentiation in the male marmoset (Callithrix jacchus): similarities with the human and differences from the rat

STUDY QUESTION

Is perinatal germ cell (GC) differentiation in the marmoset similar to that in the human?

SUMMARY ANSWER

In a process comparable with the human, marmoset GC differentiate rapidly after birth, losing OCT4 expression after 5–7 weeks of age during mini-puberty.

WHAT IS KNOWN ALREADY

Most of our understanding about perinatal GC development derives from rodents, in which all gonocytes (undifferentiated GC) co-ordinately lose expression of the pluripotency factor OCT4 and stop proliferating in late gestation. Then after birth these differentiated GC migrate to the basal lamina and resume proliferation prior to the onset of spermatogenesis. In humans, fetal GC differentiation occurs gradually and asynchronously and OCT4⁺ GC persist into perinatal life. Failure to switch off OCT4 in GC perinatally can lead to development of carcinoma in situ (CIS), the precursor of testicular germ cell cancer (TGCC), for which there is no animal model. Marmosets show similarities to the human, but systematic evaluation of perinatal GC development in this species is lacking. Similarity, especially for loss of OCT4 expression, would support use of the marmoset as a model for the human and for studying CIS origins.

STUDY DESIGN, SIZE AND DURATION

Testis tissues were obtained from marmosets (n = 4–10 per age) at 12–17 weeks' gestation and post-natal weeks 0.5, 2.5, 5–7, 14 and 22 weeks, humans at 15–18 weeks' gestation (n = 5) and 4–5 weeks of age (n = 4) and rats at embryonic day 21.5 (e21.5) (n = 3) and post-natal days 4, 6 and 8 (n = 4 each).

PARTICIPANTS/MATERIALS, SETTING AND METHODS

Testis sections from fetal and post-natal marmosets, humans and rats were collected and immunostained for OCT4 and VASA to identify undifferentiated and differentiated GC, respectively, and for Ki67, to identify proliferating GC. Stereological quantification of GC numbers, differentiation (% OCT4⁺ GC) and proliferation were performed in perinatal marmosets and humans. Quantification of GC position within seminiferous cords was performed in marmosets, humans and rats.

MAIN RESULTS AND ROLE OF CHANCE

The total GC number increased 17-fold from birth to 22 post-natal weeks in marmosets; OCT4⁺ and VASA⁺ GC proliferated equally in late gestation and early post-natal life. The percentage of OCT4⁺ GC fell from 54% in late fetal life to <0.5% at 2.5 weeks of age and none were detected after 5–7 weeks in marmosets. In humans, the percentage of OCT4⁺ GC also declined markedly during the equivalent period. In marmosets, GC had begun migrating to the base of seminiferous cords at ∼22 weeks of age, after the loss of GC OCT4 expression.

LIMITATIONS, REASONS FOR CAUTION

There is considerable individual variation between marmosets. Although GC development in marmosets and humans was similar, there are differences with respect to proliferation during fetal life. The number of human samples was limited.

WIDER IMPLICATIONS OF THE FINDINGS

The similarities in testicular GC differentiation between marmosets and humans during the perinatal period, and their differences from rodents, suggest that the marmoset may be a useful model for studying the origins of CIS, with relevance for the study of TGCC.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by Grant G33253 from the Medical Research Council, UK. No external funding was sought and there are no competing interests.

Temporal role of Sertoli cell androgen receptor expression in spermatogenic development

Sertoli cell (SC) androgen receptor (AR) activity is vital for spermatogenesis. We created a unique gain-of-function transgenic (Tg) mouse model to determine the temporal role of SCAR expression in testicular development. The SC-specific rat Abpa promoter directed human Tg AR [Tg SC-specific AR (TgSCAR)] expression, providing strong premature postnatal AR immunolocalized to SC nuclei. Independent Tg lines revealed that TgSCAR dose dependently reduced postnatal and mature testis size (to 60% normal), whereas androgen-dependent mature seminal vesicle weights and serum testosterone levels remained normal. Total SC numbers were reduced in developing and mature TgSCAR testes, despite normal or higher Fshr mRNA and circulating FSH levels. Postnatal TgSCAR testes exhibited elevated levels of AR-regulated Rhox5 and Spinlw1 transcripts, and precocious SC function was demonstrated by early seminiferous tubular lumen formation and up-regulated expression of crucial SC tight-junction (Cldn11 and Tjp1) and phagocytic (Elmo1) transcripts. Early postnatal Amh expression was elevated but declined to normal levels in peripubertal-pubertal TgSCAR vs. control testes, indicating differential age-related regulation featuring AR-independent Amh down-regulation. TgSCAR induced premature postnatal spermatogenic development, shown by increased levels of meiotic (Dmc1 and Spo11) and postmeiotic (Capza3 and Prm1) germ cell transcripts, elevated meiotic-postmeiotic germ:Sertoli cell ratios, and accelerated spermatid development. Meiotic germ:Sertoli cell ratios were further increased in adult TgSCAR mice, indicating predominant SCAR-mediated control of meiotic development. However, postmeiotic germ:Sertoli cell ratios declined below normal. Our unique TgSCAR paradigm reveals that atypical SC-specific temporal AR expression provides a direct molecular mechanism for induction of precocious testicular development, leading to reduced adult testis size and decreased postmeiotic development.

Insufficient androgen and FSH signaling may be responsible for the azoospermia of the infantile primate testes despite exposure to an adult-like hormonal milieu

BACKGROUND

In humans, as well as in other higher primates, the infantile testis is exposed to an adult-like hormonal milieu, but spermatogenesis is not initiated at this stage of primate development. In the present study, we examined the molecular basis of this intriguing infertile state of the primate testis.

METHODS

The integrity of androgen receptor (AR) and FSH receptor (FSHR) signaling pathways in primary cultures of Sertoli cells (Scs) harvested from azoospermic infant and spermatogenic pubertal monkey testes were investigated under identical in vitro hormonal conditions. In order to synchronously harvest Scs from early pubertal testis, the activation of testicular puberty was timed experimentally by prematurely initiating gonadotrophin secretion in juvenile animals with an intermittent infusion of gonadotrophin-releasing hormone.

RESULTS

While qRT-PCR demonstrated that AR and FSHR mRNA expression in Scs from infant and pubertal testes were comparable, androgen-binding and FSH-mediated cAMP production by infant Scs was extremely low. Compromised AR and FSHR signaling in infant Scs was further supported by the finding that testosterone (T) and FSH failed to augment the expression of the T responsive gene, claudin 11, and the FSH responsive genes, inhibin-βB, stem cell factor (SCF) and glial cell line-derived neurotrophic factor (GDNF) in Scs harvested at this stage of development.

CONCLUSION

These results indicate that compromised AR and FSHR signaling pathways in Scs underlie the inability of the infant primate testis to respond to an endogenous hormonal milieu that later in development, at the time puberty, stimulates the initiation of spermatogenesis. This finding may have relevance to some forms of idiopathic infertility in men.

Immunolocalization of estrogen receptor alpha, estrogen receptor beta and androgen receptor in the pre-, peri- and post-pubertal stallion testis

In various species, androgens and estrogens regulate the function of testicular Leydig, Sertoli, peritubular myoid, and germ cells by binding to their respective receptors and eliciting a cellular response. Androgen receptor (AR) is expressed in Sertoli cells, peritubular myoid cells, Leydig cells and perivascular smooth muscle cells in the testis depending on the species, but its presence in germ cells remains controversial. Two different estrogen receptors have been identified, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), and their localization and function in testicular cells varies depending on the species, developmental stage of the cell and type of receptor. The localization of AR in an immature and mature stallion has been reported but estrogen receptors have only been reported for the mature stallion. In the present study, the localizations of AR and ERα/ERβ were investigated in pre-pubertal, peri-pubertal and post-pubertal stallions. Testes were collected by routine castration from 21 horses, of light horse breeds (3 months-27 years). Animals were divided into the following age groups: pre-pubertal (3-11 months; n=7), peri-pubertal (12-23 months; n=7) and post-pubertal (2-27 years; n=7). Testicular tissue samples were fixed and embedded, and the presence of AR, ERα and ERβ was investigated by immunohistochemistry (IHC) using procedures previously validated for the horse. Primary antibodies used were rabbit anti-human AR, mouse anti-human ERβ and rabbit anti-mouse ERα. Sections of each region were incubated with normal rabbit serum (NRS; AR and ERα) or mouse IgG (ERβ) instead of primary antibody to generate negative controls. Androgen receptors were localized in Leydig, Sertoli and peritubular myoid cells of all ages. Estrogen receptor alpha was localized in Leydig and germ cells of all ages but only in pre- and peri-pubertal Sertoli cells and post-pubertal peritubular myoid cells. Estrogen receptor beta was localized in Leydig and Sertoli cells of all ages but in only pre-pubertal germ cells and absent in peritubular myoid cells of all ages. Taken together, the data suggest that estrogen regulates steroidogenesis by acting through ERα and ERβ in the Leydig cells and promotes gametogenesis by acting through ERβ in the Sertoli cells and ERα in the germ cells. In contrast androgen receptors are not found in germ cells throughout development and thus are likely to support spermatogenesis by way of a paracrine/autocrine pathway via its receptors in Leydig, Sertoli and peritubular myoid cells.

Oestrogens and spermatogenesis

The role of oestrogens in male reproductive tract physiology has for a long time been a subject of debate. The testis produces significant amounts of oestrogenic hormones, via aromatase, and oestrogen receptors (ERs)alpha (ESR1) and ERbeta (ESR2) are selectively expressed in cells of the testis as well as the epididymal epithelium, depending upon species. This review summarizes the current knowledge concerning the presence and activity of aromatase and ERs in testis and sperm and the potential roles that oestrogens may have in mammalian spermatogenesis. Data show that physiology of the male gonad is in part under the control of a balance of androgens and oestrogens, with aromatase serving as a modulator.

Co-localization of sorting nexin 2 and androgen receptor in the song system of juvenile zebra finches

Mechanisms regulating sexual differentiation of the zebra finch song system appear to include both genetic and hormonal factors. Sorting Nexin 2 (SNX2), which is involved in trafficking proteins between cellular membranes, and androgen receptor (AR) mRNA are both increased in song control nuclei of juvenile males compared to females. Here, in situ hybridization for SNX2 and immunohistochemistry for AR were used to evaluate these sexual dimorphisms in more detail. Estimates of the total number of HVC cells expressing SNX2 and AR, individually as well as together, were greater in 25-day-old males compared to females. The densities of these types of cells were generally also increased in males compared to females in HVC and Area X (or the equivalent portion of the medial striatum in females). On average, more than half of the AR+ cells co-expressed SNX2 in both brain regions. The potential, therefore, exists for both AR and SNX2 to be involved in masculinization of these two brain regions. One possibility is that they, either separately or in conjunction, enhance the action of trophic factors within the brain.

Changes in androgen receptor, estrogen receptor alpha, and sexual behavior with aging and testosterone in male rats

Reproductive aging in males is characterized by a diminution in sexual behavior beginning in middle age. We investigated the relationships among testosterone, androgen receptor (AR) and estrogen receptor alpha (ERalpha) cell numbers in the hypothalamus, and their relationship to sexual performance in male rats. Young (3months) and middle-aged (12months) rats were given sexual behavior tests, then castrated and implanted with vehicle or testosterone capsules. Rats were tested again for sexual behavior. Numbers of AR and ERalpha immunoreactive cells were counted in the anteroventral periventricular nucleus and the medial preoptic nucleus, and serum hormones were measured. Middle-aged intact rats had significant impairments of all sexual behavior measures compared to young males. After castration and testosterone implantation, sexual behaviors in middle-aged males were largely comparable to those in the young males. In the hypothalamus, AR cell density was significantly (5-fold) higher, and ERalpha cell density significantly (6-fold) lower, in testosterone- than vehicle-treated males, with no age differences. Thus, restoration of serum testosterone to comparable levels in young and middle-aged rats resulted in similar preoptic AR and ERalpha cell density concomitant with a reinstatement of most behaviors. These data suggest that age-related differences in sexual behavior cannot be due to absolute levels of testosterone, and further, the middle-aged brain retains the capacity to respond to exogenous testosterone with changes in hypothalamic AR and ERalpha expression. Our finding that testosterone replacement in aging males has profound effects on hypothalamic receptors and behavior has potential medical implications for the treatment of age-related hypogonadism in men.

Maternal gestational androgen levels in female marmosets (Callithrix geoffroyi) vary across trimesters but do not vary with the sex ratio of litters

Maternal hormones can dramatically modify offspring phenotypes via organizational actions on morphological and behavioral development. In placental mammals, there is the possibility that some portion of hormones in maternal circulation may be derived from fetal origin. We tested the possibility that maternal androgens in pregnant female marmosets reflected, in part, contributions from male fetuses by comparing levels of urinary androgens across pregnancy in females carrying varying numbers of male offspring. We monitored urinary androgen excretion in 18 pregnancies from five female white-faced marmosets (Callithrix geoffroyi). Androgen levels rose significantly in the first trimester of pregnancy, reached a peak in the middle of the second trimester, and then declined gradually until parturition. At no point in pregnancy were levels of urinary androgens higher in females carrying litters that had 50% or more males than in females carrying litters that were less than 50% male. Levels of maternal androgens were not associated with litter size, the number of males in the litter, or with the proportion of the litter that was male. The high levels of androgen in pregnant females are therefore likely of strictly maternal origin, and any modification of fetal growth and development can be considered a 'maternal effect'.

Sexual experience changes sex hormones but not hypothalamic steroid hormone receptor expression in young and middle-aged male rats

Testosterone is well known to regulate sexual behavior in males, but this is dependent upon prior sexual experience. Aging is associated with decreased libido and changes in testosterone, but the role of experience in these age-related processes has not been systematically studied. We examined effects of age and sexual experience on serum hormones (total testosterone, free testosterone, estradiol, LH) and on numbers of androgen receptor (AR) and estrogen receptor alpha (ERalpha) immunoreactive cells in the hypothalamus. Extensive sexual experience was given to male rats at 4 months of age. Rats were euthanized at either 4 months (young) or 12 months (middle-aged (MA)). Comparable sexually naïve male rats were handled and placed into the testing arena but did not receive any sexual experience. Thus, we had four groups: young-naïve, young-experienced, MA-naïve and MA-experienced. Serum hormone levels were assayed, and numbers of AR and ERalpha cells were quantified stereologically in the medial preoptic nucleus (MPN) and the anteroventral periventricular nucleus (AVPV). Sexually experienced males had significantly elevated serum testosterone and free testosterone in both age groups. Both total and free testosterone were higher, and estradiol lower, in middle-aged than young rats. Experience did not alter either AR or ERalpha expression in the preoptic brain regions studied. Aging was associated with increased expression of AR, but no change in ERalpha. These results show that sexual experience can induce short-term and long-term alterations in serum hormones but these effects are not manifested upon their receptors in the hypothalamus.

Effect of fetal or neonatal exposure to monobutyl phthalate (MBP) on testicular development and function in the marmoset

BACKGROUND

Fetal exposure of male rats to some phthalates induces reproductive abnormalities, raising concerns for similar effects in humans. In order to address this in a more appropriate animal model, the aim of the present studies was to investigate the effect of fetal/neonatal exposure to monobutyl phthalate (MBP) in a non-human primate, the marmoset. In particular, to determine if exposure resulted in effects at birth, or in adulthood, similar to those in male rats, and whether there was evidence for induction of carcinoma-in-situ (CIS) or testicular germ cell tumours (TGCT).

METHODS

Pregnant female marmosets were dosed from ∼7–15 weeks gestation with 500 mg/kg/day MBP and male offspring studied at birth (1–5 days; n = 6) or in adulthood (n = 5). In another study, newborn males (n = 5 co-twins) were dosed with 500 mg/kg/day MBP for 14 days, commencing at ∼4 days of age.

RESULTS

Fetal exposure of marmosets to MBP did not affect gross testicular morphology, reproductive tract development or testosterone levels at birth, nor were germ cell number and proliferation, Sertoli cell number or germ:Sertoli cell ratio affected. In two of six MBP-exposed animals, unusual clusters of undifferentiated germ cells were found, but their significance is unclear. Neonatal MBP treatment did not affect germ cell numbers or differentiation. Fetal exposure to MBP did not affect testis size/morphology, germ cell numbers or fertility in adulthood. There was no evidence for CIS or TGCT.

CONCLUSIONS

Fetal exposure of marmosets to MBP does not measurably affect testis development/function or cause testicular dysgenesis, and no effects emerge by adulthood. Some effects on germ cell development were found, but these were inconsistent and of uncertain significance.

Increased exposure to estrogens disturbs maturation, steroidogenesis, and cholesterol homeostasis via estrogen receptor alpha in adult mouse Leydig cells

Deteriorated male reproductive health has been connected to overexposure to estrogens or to imbalanced androgen-estrogen ratio. Transgenic male mice expressing human aromatase (AROM(+) mice) serve as an apt model for the study of the consequences of an altered androgen-estrogen ratio. Our previous studies with AROM(+) mice showed that low androgen levels together with high estrogen levels result in cryptorchidism and infertility. In the present study, the AROM(+) mice were shown to have severe abnormalities in the structure and function of Leydig cells before the appearance of spermatogenic failure. Decreased expression of adult-type Leydig cell markers (Ptgds, Vcam1, Insl3, Klk21, -24 and -27, Star, Cyp17a1, and Hsd17b3) indicated an immature developmental stage of the Leydig cells, which appears to be the first estrogen-dependent alteration. Genes involved in steroidogenesis (Star, Cyp17a1, and Hsd17b3) were suppressed despite normal LH levels. The low expression level of kallikreins 21, 24, and 27 potentially further inhibited Leydig cell function via remodeling extracellular matrix composition. In connection with disrupted steroidogenesis, Leydig cells showed enlarged mitochondria, a reduced amount of smooth endoplasmic reticulum, and an accumulation of cholesterol and precursors for cholesterol synthesis. The results of studies with AROM(+) mice crossed with estrogen receptor alpha or beta (ERalpha and ERbeta, respectively) knockout mice lead to the conclusion that the structural and functional disorders caused by estrogen exposure were mediated via ERalpha, whereas ERbeta was not involved.

Lack of androgen receptor expression in Sertoli cells accounts for the absence of anti-Mullerian hormone repression during early human testis development

CONTEXT

Puberty is associated with increased testicular testosterone (TT) synthesis, which is required to trigger spermatogenesis and to repress anti-Mullerian hormone (AMH) production. However, testicular gonadotropin stimulation during fetal and newborn life neither initiates spermatogenesis nor represses AMH.

OBJECTIVE

We postulated that a lack of androgen receptor (AR) expression in Sertoli cells (SC) might explain why these processes do not occur during early human development.

METHODS AND PATIENTS

Using immunohistochemistry and quantitative PCR, we examined the relationship between AR, AMH, and FSH receptor expression in fetal, newborn, and adult human testis. The ability of testosterone to repress AMH secretion was evaluated in male newborns, neonates, and two adults with androgen insensitivity syndrome and also in vitro using SMAT1 SC.

RESULTS

FSH receptor was present in SC at all developmental stages. In fetal and newborn testis, AR was expressed in peritubular and Leydig cells but not in SC. This coincided with the absence of spermatogenesis and with strong SC AMH expression. In adult testis, spermatogenesis was associated with AR expression and with a decrease in SC AMH content. Accordingly, AR mRNA expression was lower and AMH mRNA expression higher in fetal testes than in adult testes. In androgen insensitivity syndrome patients, combined gonadotropin stimulation induced an increase in circulating testosterone and AMH, a finding consistent with a failure of TT to repress AMH in the absence of AR signalling. Finally, direct androgen repression of AMH only occurred in AR-expressing SMAT1 cells.

CONCLUSION

Functional ARs are essential for TT-mediated AMH repression in SC.

Distribution of estrogen receptors (ERalpha and ERbeta) and androgen receptor in the testis of big fruit-eating bat Artibeus lituratus is cell- and stage-specific and increases during gonadal regression

The testis is a classical target for androgens, especially testosterone, acting via androgen receptor (AR). Alternatively, androgens can be aromatized to produce estrogens which act via specific receptors ERalpha and ERbeta. Although estrogen action is essential for maintenance of male fertility, studies regarding the expression of ERalpha and ERbeta in testis are restricted to a few species of rodent and domestic animals, but rarely in wild species. To our knowledge, there are no studies in Chiroptera species. Chiroptera represent one of the largest and most diversified orders of mammals, which possess several interesting reproductive features, including higher affinity of SHBG for estrogens than androgens. Therefore, we thought that bats would constitute a good model for investigation of the role of estrogens in the male. In this study, the distribution of ERalpha, ERbeta and AR were evaluated in the testis of the big fruit-eating bat Artibeus lituratus and their levels were compared during reproductive and regressive periods. The results showed that ERalpha and AR were restricted to the somatic cells of the testis, whereas ERbeta was widely distributed in both somatic and spermatogenic cells in a cellular and stage-specific fashion. We demonstrated for the first time by immunohistochemistry, and confirmed by Western blotting, that ERbeta and AR increased during regression. The localization of ERalpha, ERbeta and AR in a seasonal, cell and stage-specific fashion in the testis of A. lituratus suggests that these receptors may play important roles in testis function during reproductive and non-reproductive periods.

Androgen receptor roles in spermatogenesis and fertility: lessons from testicular cell-specific androgen receptor knockout mice

Androgens are critical steroid hormones that determine the expression of the male phenotype, including the outward development of secondary sex characteristics as well as the initiation and maintenance of spermatogenesis. Their actions are mediated by the androgen receptor (AR), a member of the nuclear receptor superfamily. AR functions as a ligand-dependent transcription factor, regulating expression of an array of androgen-responsive genes. Androgen and the AR play important roles in male spermatogenesis and fertility. The recent generation and characterization of male total and conditional AR knockout mice from different laboratories demonstrated the necessity of AR signaling for both external and internal male phenotype development. As expected, the male total AR knockout mice exhibited female-typical external appearance (including a vagina with a blind end and a clitoris-like phallus), the testis was located abdominally, and germ cell development was severely disrupted, which was similar to a human complete androgen insensitivity syndrome or testicular feminization mouse. However, the process of spermatogenesis is highly dependent on autocrine and paracrine communication among testicular cell types, and the disruption of AR throughout an experimental animal cannot answer the question about how AR in each type of testicular cell can play roles in the process of spermatogenesis. In this review, we provide new insights by comparing the results of cell-specific AR knockout in germ cells, peritubular myoid cells, Leydig cells, and Sertoli cells mouse models that were generated by different laboratories to see the consequent defects in spermatogenesis due to AR loss in different testicular cell types in spermatogenesis. Briefly, this review summarizes these results as follows: 1) the impact of lacking AR in Sertoli cells mainly affects Sertoli cell functions to support and nurture germ cells, leading to spermatogenesis arrest at the diplotene primary spermatocyte stage prior to the accomplishment of first meiotic division; 2) the impact of lacking AR in Leydig cells mainly affects steroidogenic functions leading to arrest of spermatogenesis at the round spermatid stage; 3) the impact of lacking AR in the smooth muscle cells and peritubular myoid cells in mice results in similar fertility despite decreased sperm output as compared to wild-type controls; and 4) the deletion of AR gene in mouse germ cells does not affect spermatogenesis and male fertility. This review tries to clarify the useful information regarding how androgen/AR functions in individual cells of the testis. The future studies of detailed molecular mechanisms in these in vivo animals with cell-specific AR knockout could possibly lead to useful insights for improvements in the treatment of male infertility, hypogonadism, and testicular dysgenesis syndrome, and in attempts to create safe as well as effective male contraceptive methods.

Ontogeny of androgen and estrogen receptor expression in porcine testis: Effect of reducing testicular estrogen synthesis

Reducing endogenous estrogen leads to increased proliferation of porcine Sertoli cells during the first 2 months of life. The resulting increase in porcine Sertoli cell numbers is maintained through puberty. The reduced estrogen appears to be the direct hormonal mediator because essentially no changes are observed in other hormones. However, the mechanism for this effect on Sertoli cell proliferation is unknown. The objective of these studies was to evaluate estrogen receptors alpha and beta (ESR1 and ESR2) in conjunction with androgen receptor (AR) on Sertoli cells and other testicular cell types, as an initial step toward understanding how reduced estrogen leads to increased Sertoli cell numbers. Testis sections from treated animals (aromatase inhibition to decrease endogenous estrogen beginning at 1 week of age) and from littermate controls treated with vehicle were subjected to immunocytochemical labeling for ESR1, ESR2, and AR. Three observers scored Sertoli cells, interstitial cells, peritubular myoid cells, and germ cells for intensity of labeling (0: absent; 1+: weak; 2+: moderate; or 3+: strong labeling). AR in Sertoli cells was readily detected at 1 week of age, was very faint in 2-month vehicle controls, and labeling appeared to increase in 3-month vehicle controls. AR in Sertoli cells, interstitial cells, and apparently germ cells was increased in treated animals at 2 months of age compared with the vehicle controls. This increase was confirmed in western blots. ESR1 and ESR 2 were clearly present in Sertoli cells from 1-week-old animals; ESR in Sertoli cells generally decreased with age with the decrease more apparent for ESR2. ESR1 in Sertoli cells and peritubular myoid cells exhibited some treatment-related effects but reduction of endogenous estrogen did not appear to affect ESR2 in the boar testis. The observed alterations in AR and ESR1 may mediate the increases in Sertoli cell proliferation following inhibition of endogenous estrogen production or may reflect the altered function of the Sertoli cells and peritubular myoid cells.

Oestrogen and progesterone receptors in the marmoset endometrium: changes during the ovulatory cycle, early pregnancy and after inhibition of vascular endothelial growth factor, GnRH or ovariectomy

Marmosets are widely used, but detailed studies on localisation of endometrial oestrogen receptors alpha and beta (ER alpha and ER beta ), and the progesterone receptor (PR) are lacking. These receptors were localised and semi-quantitatively analysed throughout the ovulatory cycle, weeks 2, 3 and 4 of pregnancy and after treatment with GnRH antagonist, vascular endothelial growth factor (VEGF) Trap or ovariectomy. The PR in epithelial cells increased markedly between the mid- and late proliferative phases before declining in the mid-secretory phase and pregnancy. PR in stromal cells was present throughout the cycle and levels were maintained in pregnancy. ER alpha was present at the mid-proliferative phase and increased in glands at the late proliferative and early secretory phases, before declining at the late secretory phase and week 4 of pregnancy. Stromal ER alpha showed a similar trend, but decreased earlier, by the mid-secretory phase. ER beta was highly expressed in epithelial cells throughout the cycle and in pregnancy. In stroma, increases in ER beta expression were observed at the late proliferative phase with the staining index decreasing by half as the secretory phase progressed and in pregnancy. GnRH antagonist, VEGF Trap or ovariectomy caused significant reductions in PR and ER beta expression, but not in ER alpha when compared with the late proliferative phase of the normal cycle. Endothelial cells expressed ER beta , but not ER alpha or PR. It is concluded that the steroid receptor profile in the marmoset endometrium is generally similar to the human and should provide a useful model for studies on hormonal manipulation of the endometrium.

Effects of monobutyl and di(n-butyl) phthalate in vitro on steroidogenesis and Leydig cell aggregation in fetal testis explants from the rat: comparison with effects in vivo in the fetal rat and neonatal marmoset and in vitro in the human

BACKGROUND

Certain phthalates can impair Leydig cell distribution and steroidogenesis in the fetal rat in utero, but it is unknown whether similar effects might occur in the human.

OBJECTIVES

Our aim in this study was to investigate the effects of di(n-butyl) phthalate (DBP), or its metabolite monobutyl phthalate (MBP), on testosterone production and Leydig cell aggregation (LCA) in fetal testis explants from the rat and human, and to compare the results with in vivo findings for DBP-exposed rats. We also wanted to determine if DBP/MBP affects testosterone production in vivo in the neonatal male marmoset.

METHODS

Fetal testis explants obtained from the rat [gestation day (GD)19.5] and from the human (15-19 weeks of gestation) were cultured for 24-48 hr with or without human chorionic gonadotropin (hCG) or 22R-hydroxycholesterol (22R-OH), and with or without DBP/MBP. Pregnant rats and neonatal male marmosets were dosed with 500 mg/kg/day DBP or MBP.

RESULTS

Exposure of rats in utero to DBP (500 mg/kg/day) for 48 hr before GD21.5 induced major suppression of intratesticular testosterone levels and cytochrome P450 side chain cleavage enzyme (P450scc) expression; this short-term treatment induced LCA, but was less marked than longer term (GD13.5-20.5) DBP treatment. In vitro, MBP (10(-3) M) did not affect basal or 22R-OH-stimulated testosterone production by fetal rat testis explants but slightly attenuated hCG-stimulated steroidogenesis; MBP induced minor LCA in vitro. None of these parameters were affected in human fetal testis explants cultured with 10(-3) M MBP for up to 48 hr. Because the in vivo effects of DBP/MBP were not reproduced in vitro in the rat, the absence of MBP effects in vitro on fetal human testes is inconclusive. In newborn (Day 2-7) marmosets, administration of a single dose of 500 mg/kg MBP significantly (p = 0.019) suppressed blood testosterone levels 5 hr later. Similar treatment of newborn co-twin male marmosets for 14 days resulted in increased Leydig cell volume per testis (p = 0.011), compared with co-twin controls; this is consistent with MBP-induced inhibition of steroidogenesis followed by compensatory Leydig cell hyperplasia/hypertrophy.

CONCLUSIONS

These findings suggest that MBP/DBP suppresses steroidogenesis by fetal-type Leydig cells in primates as in rodents, but this cannot be studied in vitro.

Expression of aromatase, estrogen receptor alpha and beta, androgen receptor, and cytochrome P-450scc in the human early prepubertal testis

The expression of aromatase, estrogen receptor alpha (ERalpha) and beta (ERbeta), androgen receptor (AR), and cytochrome P-450 side chain cleavage enzyme (cP450scc) was studied in prepubertal testis. Samples were divided in three age groups (GRs): GR1, newborns (1- to 21-d-old neonates, n = 5); GR2, postnatal activation stage (1- to 7-mo-old infants, n = 6); GR3, childhood (12- to 60-mo-old boys, n = 4). Absent or very poor detection of ERalpha by immunohistochemistry in all cells and by mRNA expression was observed. Leydig cells (LCs) of GR1 and GR2 showed strong immunostaining of aromatase and cP450scc but weak staining of ERbeta and AR. Interstitial cells (ICs) and Sertoli cells (SCs) expressed ERbeta, particularly in GR1 and GR2. Strong expression of AR was found in peritubular cells (PCs). For all markers, expression in GR3 was the weakest. In germ cells (GCs), i.e. gonocytes and spermatogonia, aromatase and ERbeta were immunoexpressed strongly whereas no expression of ERalpha, AR, or cP450scc was detected. It is proposed that in newborn and infantile testis, testosterone acting on PCs might modulate infant LC differentiation, whereas the absence of AR in SCs prevents development of spermatogenesis. The role of estrogen is less clear, but it could modulate the preservation of an adequate pool of precursor LCs and GCs.

Postnatal and pubertal development of the rhesus monkey (Macaca mulatta) testis

This review examines the neurobiology, endocrinology, and cell biology underlying the development of the testis from birth until puberty in the rhesus monkey, a representative higher primate.

Testosterone induces testicular development but reduces GnRH-I fiber density in the brain of the House Finch, Carpodacus mexicanus

Testosterone (T) in male birds generally inhibits the activity of the hypothalamo-pituitary-gonadal axis, but the androgen can also be gonadostimulatory. The mechanisms responsible for this stimulation are unknown. To address this question, adult male House Finches, Carpodacus mexicanus, held on short day length to inhibit reproductive function, received 20-mm long T-filled Silastic capsules either for 74 days (T+; n=5; Day 1-74) or for 66 days followed by eight days without capsules (T-; n=5), or empty capsules for 74 days (controls, C, n=10). At sacrifice on Day 74, plasma T concentrations were elevated in T+ males and low, and similar in T- and C males. Testes were enlarged in T+ males (136.5+/-57.2mg), small in T- males (16.2+/-9.5 mg), and undeveloped in C males (5.4+/-3.6 mg). The three groups had similar numbers and sizes of hypothalamic gonadotropin-releasing hormone-I immunoreactive (GnRH-I ir) perikarya, but perikaryon GnRH-I ir labelling was lighter in T+ than C males. T+ males also had lower density of GnRH-immunolabelled fibers in the preoptic area and lower intensity of GnRH immunolabelling in the median eminence than C males, suggesting an inhibition of GnRH-I neuronal activity. Plasma luteinizing hormone in the three experimental groups was uniformly low and did not differ. Thus, T administration-induced testicular development was associated with an inhibition of the reproductive neuroendocrine system, demonstrating a direct stimulatory effect of T on testes. Stimulation of testicular function by endogenous T in seasonal breeders may contribute to the rapid gonadal maturation that takes place in response to photostimulation.

Mitotic activity of Sertoli cells in adult human testis: an immunohistochemical study to characterize Sertoli cells in testicular cords from patients showing testicular dysgenesis syndrome

During puberty, normal somatic Sertoli cells undergo dramatic morphological changes due to the differentiation of immature pre-Sertoli cells in functionally active adult Sertoli cells. Sertoli cell maturation is accompanied with loss of their mitotic activity before onset of spermatogenesis and loss of pre-pubertal and occurrence of adult immunohistochemical Sertoli cell differentiation markers. Testes of infertile adult patients often exhibit numerous histological signs of testicular dysgenesis syndrome (TDS) such as microliths, Sertoli cell only (SCO) tubules, tubules containing carcinoma in situ and immature seminiferous tubules (Sertoli cell nodules). Sertoli cell tumours, however, are very rare neoplasms possibly due to the fact that the mechanism and temporal origin of neoplastic Sertoli cells underlying Sertoli cell tumourigenesis still remain unknown. To clarify the state of Sertoli cell differentiation in both immature seminiferous tubules of adult patients with TDS and Sertoli cell tumour, we compared the expression of the Sertoli cell differentiation markers vimentin, inhibin-alpha, anti-Muellerian-hormone, cytokeratin 18, M2A-antigen, androgen receptor and connexin43 with that of SCO tubules with hyperplasia. In addition, we demonstrated for the first time the existence of proliferating Sertoli cells by Ki67- and PCNA-immunostaining in Sertoli cell nodules of the adult human testis. Our data indicate that mitotically active Sertoli cells in Sertoli cell nodules will be arrested prior to puberty and, contrary to dogma, do not represent foetal or neonatal cells. Since all markers in Sertoli cell nodules revealed a staining pattern identical to that in neoplastic Sertoli cells, but different to that in Sertoli cells of SCO tubules with hyperplasia, it may be speculated that Sertoli cell tumours in adult men may originate from Sertoli cell nodules.

Cellular localization of estrogen receptor-alpha (ERalpha) and -beta (ERbeta) mRNA in the boar testis

Boar testes synthesize high amounts of estrogens which are known to stimulate several male sexual functions in a variety of extragonadal target tissues. Possible effects within the testis depend on the existence of the estrogen receptor subtypes alpha and beta (ERalpha, ERbeta). The precise cellular localization of these subtypes within the testis was, so far, based mainly on protein expression studies using different antibodies in several species including boars shows contradictory results. Therefore, we investigated the ERalpha and ERbeta gene expression using RT-PCR of testis homogenates and RT-PCR after UV-single cell microdissection combined with in-situ hybridization of four fertile boars with an average age of 32 weeks. Both ERalpha and ERbeta mRNA were found in testis homogenates. Using in-situ hybridization and UV-single cell microdissection ERalpha mRNA was present in type A and type B spermatogonia up to mid-pachytene primary spermatocytes in stage V-VIII and stage I of the seminiferous epithelial cycle, but not in other cells. ERbeta mRNA was found only in Sertoli cells. Interstitial Leydig cells revealed neither ERalpha nor ERbeta mRNA. The data suggest a direct impact of estrogen in the boar on Sertoli cell function via ERbeta and germ cell formation via ERalpha.

Prepubertal expansion of dark and pale type A spermatogonia in the rhesus monkey (Macaca mulatta) results from proliferation during infantile and juvenile development in a relatively gonadotropin independent manner

The purpose of the present study was to determine whether dark and pale type A spermatogonia (Ad and Ap, respectively) are mitotically active during prepubertal development and whether proliferation of these germ cells during this protracted phase of primate development occurs predominantly during infancy before gonadotropin secretion is arrested. Four neonate (1-2 days of age), four infant (4-5 mo of age), and four juvenile (14-17 mo of age) rhesus monkeys (Macaca mulatta) were castrated 2 h after receiving an i.v. bolus of 5-bromo2'-deoxy-uridine (BrdU, 33 mg/kg body weight). Tissue was fixed in Bouin solution, and 5-microm paraffin sections were cut. Using periodic acid-Schiff reagent/Gill hematoxylin staining, the number per testis of Ad and Ap spermatogonia were determined. BrdU S-phase-labeled nuclei were identified using immunofluorescence. Conservative criteria were employed for classifying cell types, and this resulted in a fraction of A spermatogonia remaining unclassified. Ad, Ap, and the unclassified A spermatogonia each showed an approximately 4-fold increase over the 5-mo period from birth to infancy, and a similar increase was observed over the 10-mo period between infancy and the juvenile stage of development. Both Ad and Ap (and unclassified A spermatogonia) exhibited robust and similar S-phase labeling at the three stages of development. We conclude that the prepubertal expansion of Ad and Ap spermatogonia is achieved by mitotic proliferation that is relatively gonadotropin independent. This conclusion raises the question of the nature of the signal that arrests the cell cycle of Ad in adult testis.

Review on testicular development, structure, function, and regulation in common marmoset

BACKGROUND

The common marmoset (Callithrix jacchus) is a New World primate that has been used increasingly in toxicological evaluations including testing for testicular toxicity of pharmaceutical and environmental chemicals. Information on structural and functional characteristics of the testis in common marmosets ("marmoset" in this review) is critical for designing experiments, interpreting data collected, and determining relevance to humans in risk assessment.

METHODS

This study provides a comprehensive review on testicular development, structure, function, and regulation in common marmosets.

RESULTS

There is little information regarding testicular formation and development during gestation. Based on the overall pattern of embryonic development in marmosets, it is postulated that gonadal formation and testicular differentiation most likely takes place during gestational Week 6-12. After birth, the neonatal period of the first 2-3 weeks and the pubertal period from Months 6-12 are critical for establishment of spermatogenesis in the adult. In the adult, a nine-stage model has been used to describe the organization of seminiferous epithelium and multiple stages per tubular cross-section have been observed. Seminiferous epithelium is organized in a wave or partial-wave manner. There are on average two stages per cross-section of seminiferous tubules in adult marmoset testis. Sertoli cells in the marmoset have a uniform morphology. Marmoset spermatogenesis has a high efficiency. The prime determinant of germ cell production is proliferation and survival of spermatogonia. Sertoli cell proliferation during the neonatal period is regulated by follicle-stimulating hormone (FSH), but chorionic gonadotropin (CG), instead of luteinizing hormone (LH), is the only gonadotropin with luteinizing function in marmoset. The receptor gene for CG in marmoset is unique in that it does not have exon 10. Marmosets have a "generalized steroid hormone resistance," i.e., relatively high levels of steroid hormones in circulation and relatively low response to exogenous steroids. Blockage of FSH, CG, and testosterone production during the first 3 months after birth does not cause permanent damage to the male reproductive system. Initiation of spermatogenesis in the marmoset requires unique factors that are probably not present in other mammals. Normal male marmosets respond to estradiol injection positively (increased LH or CG levels), a pattern seen in normal females or castrated males, but not usually in normal males of other mammalian species.

CONCLUSIONS

It seems that the endocrine system including the testis in marmosets has some unique features that have not been observed in rodents, Old World primates, and humans, but detailed comparison in these features among these species will be presented in another review. Based on the data available, marmoset seems to be an interesting model for comparative studies. However, interpretation of experimental findings on the testicular effects in marmosets should be made with serious caution. Depending on potential mode of testicular actions of the chemical under investigation, marmoset may have very limited value in predicting potential testicular or steroid hormone-related endocrine effects of test chemicals in humans.

Subcellular and molecular mechanisms regulating anti-Müllerian hormone gene expression in mammalian and nonmammalian species

Anti-Müllerian hormone (AMH) is best known for its role as an inhibitor of the development of female internal genitalia primordia during fetal life. In the testis, AMH is highly expressed by Sertoli cells of the testis from early fetal life to puberty, when it is downregulated by the action of testosterone, acting through the androgen receptor, and meiotic spermatocytes, probably acting through TNFalpha. Basal expression of AMH is induced by SOX9; GATA4, SF1, and WT1 enhance SOX9-activated expression. When the hypothalamic-pituitary axis is active and the negative effect of androgens and germ cells is absent, for example, in the fetal and neonatal periods or in disorders like androgen insensitivity, FSH upregulates AMH expression through a nonclassical cAMP-PKA pathway involving transcription factors AP2 and NFkappaB. The maintenance and hormonal regulation of AMH expression in late fetal and postnatal life requires distal AMH promoter sequences. In the ovary, granulosa cells express AMH from late fetal life at low levels; DAX1 and FOG2 seem to be responsible for negatively modulating AMH expression. Particular features are observed in AMH expression in nonmammalian species. In birds, AMH is expressed both in the male and female fetal gonads, and, like in reptiles, its expression is not preceded by that of SOX9.

Estrogen in the adult male reproductive tract: a review

Testosterone and estrogen are no longer considered male only and female only hormones. Both hormones are important in both sexes. It was known as early as the 1930's that developmental exposure to a high dose of estrogen causes malformation of the male reproductive tract, but the early formative years of reproductive biology as a discipline did not recognize the importance of estrogen in regulating the normal function of the adult male reproductive tract. In the adult testis, estrogen is synthesized by Leydig cells and the germ cells, producing a relatively high concentration in rete testis fluid. Estrogen receptors are present in the testis, efferent ductules and epididymis of most species. However, estrogen receptor-alpha is reported absent in the testis of a few species, including man. Estrogen receptors are abundant in the efferent ductule epithelium, where their primary function is to regulate the expression of proteins involved in fluid reabsorption. Disruption of the alpha-receptor, either in the knockout (alphaERKO) or by treatment with a pure antiestrogen, results in dilution of cauda epididymal sperm, disruption of sperm morphology, inhibition of sodium transport and subsequent water reabsorption, increased secretion of Cl-, and eventual decreased fertility. In addition to this primary regulation of luminal fluid and ion transport, estrogen is also responsible for maintaining a differentiated epithelial morphology. Thus, we conclude that estrogen or its alpha-receptor is an absolute necessity for fertility in the male.

Infant feeding with soy formula milk: effects on the testis and on blood testosterone levels in marmoset monkeys during the period of neonatal testicular activity

BACKGROUND

This study has addressed concerns about possible effects of feeding human infants soy formula milk (SFM).

METHODS

This is a feeding study in marmosets, using a mainly co-twin design. From 4-5 until 35-45 days of age, co-twin males were fed by hand with either standard (cow) formula milk (SMA = controls) or with SFM for approximately 8 h each day (2 h at weekends) and intake related to bodyweight. Blood samples were collected at 18-20 and at 35-45 days of age in 13 sets of co-twins plus two non-twin males per group and, at the later age, seven sets of co-twins were killed and the testes and pituitary gland fixed for cell counts.

RESULTS

Weight gain and formula intake were similar in both feeding groups. SMA-fed males had mean testosterone levels of 2.8-3.1 ng/ml, typical of the "neonatal testosterone rise", whereas SFM-fed males exhibited consistently lower mean levels (1.2-2.6 ng/ml); paired comparison in SMA-and SFM-fed co-twins at day 35-45 revealed 53-70% lower levels in 11 of 13 co-twins fed with SFM (P = 0.004). Further evidence for suppression of testosterone levels in SFM-fed males came from comparison of the frequency of low testosterone levels (<0.5 ng/ml). In historical controls aged 35-45 days, two out of 22 values were <0.5 ng/ml, a similar frequency as found in control SMA-fed males (one out of 15 values <0.5 ng/ml). In contrast, 12 out of 15 values for SFM-fed males were <0.5 ng/ml (P < 0.001). There was no consistent relationship between SFM intake/g and testosterone levels. Paradoxically, the mean number of Leydig cells per testis was increased by 74% (P < 0.001) in co-twins fed SFM, when compared with their SMA-fed brothers, whereas no significant changes were found in numbers of Sertoli and germ cells. Because of the lack of gonadotrophin assays, the number of immunopositive LHbeta and FSHbeta cells in the pituitary gland, and their ratio, were determined but no consistent difference was found between SMA- and SFM-fed twins.

CONCLUSIONS

Based on the average isoflavone content of the SFM brand used, intake of isoflavones was estimated at 1.6-3.5 mg/kg/day in the SFM-fed marmosets which is 40-87% of that reported in 4 month human infants fed on a 100% SFM diet. It is therefore considered likely that similar, or larger, effects to those shown here in marmosets may occur in human male infants fed with SFM. Whether the changes described result in longer-term effects is under investigation.