The role of follicle-stimulating hormone in spermatogenesis: lessons from knockout animal models

Circadian desynchrony disturbs the function of rat spermatozoa

Decreased male fertility is a growing health problem that requires a better understanding of molecular events regulating reproductive competence. Here the effects of circadian desynchrony on the rat spermatozoa functionality were studied. Circadian desynchrony was induced in rats that lived for 2 months under disturbed light conditions designed to mimic shiftwork in humans (two days of constant light, two days of continual dark, and three days of 14:10 h light:dark schedule). Such a condition abolished circadian oscillations in the rats' voluntary activity, followed by a flattened transcriptional pattern of the pituitary gene encoding follicle stimulating hormone subunit (Fshb), and genes important for germ cell maturation (Tnp1 and Prm2) as well as the clock in seminiferous tubules. However, the number of spermatozoa isolated from the epididymis of the rats suffering from circadian desynchrony did not deviate from the controls. Nevertheless, spermatozoa functionality, estimated by motility and progesterone-induced acrosome reaction, was reduced compared to the control. These changes were associated with the altered level of main markers of mitochondrial biogenesis (Pprgc1a/PGC1A, Nrf1/NRF1, Tfam, Cytc), decreased mitochondrial DNA copy number, ATP content, and clock genes (Bmal1/BMAL1, Clock, Cry1/2, and Reverba). The principal-component-analysis (PCA) points to a positive association of the clock and mitochondrial biogenesis-related genes in spermatozoa from rats suffering circadian desynchrony. Altogether, the results show the harmful effect of circadian desynchrony on spermatozoa functionality, targeting energetic homeostasis.

"Seminal testosterone", rising viewpoint of local spermatogenesis in nonobstructive azoospermia: One center long-term bidirectional cohort study

OBJECTIVE

Reproductive hormones are a traditional good method to evaluate spermatogenesis but might not accurately represent local spermatogenesis. To find a more accurate method, seminal reproductive hormones were studied.

METHODS

A bidirectional cohort study was performed. A total of 126 infertile men from 2018 to 2019 were retrospectively analyzed. They were divided into nonobstructive azoospermia (NOA), oligozoospermia (OLZ) and normal (NOR) groups. A prospective study was conducted on patients in the NOA and OLZ groups for 2 years. Microscopic testicular sperm extraction was performed for NOA patients, who were divided into a focal spermatogenesis group (FS) and an idiopathic azoospermia group (IA). Drug treatment was for OLZ patients, who were divided into a valid group (VA) and an invalid group (IN). The differences in sperm parameters and reproductive hormones were compared. ANOSIM analysis was used between and within groups. Pearson correlation analysis, CO inertia analysis and Proctor's analysis were for relationships. ROC curve for the specificity and sensitivity. Time series analysis was for the trends between hormones and time.

RESULTS

The b-FSH, b-LH, s-T and ΔT in the NOA group were significantly higher than those in the OLZ and NOR groups. However, the s-FSH, s-E₂, s-P, ΔFSH, ΔLH, ΔP and ΔE₂ were lower. Thirty-one NOA patients underwent MTSE, of whom 12 had sperm (FS) and 19 had no sperm (IA). The s-FSH and s-E₂ of the FS group were higher than those of the IA group. Twenty-six OLZ patients completed 30 days of treatment, of which 11 had an improved sperm count (VA) and 15 had no (IN). The ΔT of the VA group was higher than that of the IN group. After follow-up for 2 years, 18 patients' results showed that b-FSH, b-LH and s-T were different over time, with delays of 19, 3 and -19 days. SC is closely related to pH, s-FSH, s-LH, s-E₂, s-P, s-T, b-FSH, b-LH, ΔFSH, ΔLH, ΔP, ΔE₂ and ΔT. There were complex common trends and relationships between different kinds of hormones. s-FSH, s-LH, s-E₂, s-P, s-T, b-FSH and b-LH were useful to judge spermatogenesis, of which s-T, b-FSH and b-LH were more sensitive. If s-T, b-FSH and b-LH reached 64.4, 9.4 and 4.7, respectively, their prediction performance was the strongest.

CONCLUSION

Seminal testosterone is sensitive for judging local spermatogenesis in nonobstructive azoospermia patients, which may be the direction of local spermatogenesis in nonobstructive azoospermia.

CLINICAL TRIAL REGISTRATION

http://www.chictr.org.cn/index.aspx, identifier ChiCTR2200060463.

Diabetes mellitus and the impairment of male reproductive function: Possible signaling pathways

BACKGROUND AND AIMS

Today, it has been shown that diabetes mellitus (DM) can affect male fertility. Glucose metabolism is a vital process in spermatogenesis that is impacted by diabetes condition. But the mechanisms by which DM causes male infertility are not wholly clarified. The aim of this review is to provide brief information about the influence of hyperglycemia on male fertility and specific emphasis on the molecular signaling pathway that is involved.

METHODS

Broad literature search in the electronic database "Pubmed", "Google Scholar", the website of "World Health Organization" (WHO) and Control Disease and Prevention (CDC) took place. There was no time restriction. A key criterion for the selection of articles was English and language. Finally, one hundred thirty seven articles were included in the review.

RESULTS

Diabetes mellitus affects many signaling pathways that involved in the spermatogenesis. It seems that increased ROS and oxidative stress in the diabetes is the beginning of all fertility problems and affects all of involved signaling pathways in the spermatogenesis.

CONCLUSIONS

It seems that there was strong interconnected between oxidative stress and all of involved signaling pathways in the reproductive problems in diabetes. So, approaches that diminish oxidative stress in the testis can be effective in improving diabetes related infertility complications.

Disruption of Circadian Rhythms: A Crucial Factor in the Etiology of Infertility

Infertility represents a growing health problem in industrialized countries. Thus, a greater understanding of the molecular networks involved in this disease could be critical for the development of new therapies. A recent finding revealed that circadian rhythmicity disruption is one of the main causes of poor reproductive outcome. The circadian clock system beats circadian rhythms and modulates several physiological functions such as the sleep-wake cycle, body temperature, heart rate, and hormones secretion, all of which enable the body to function in response to a 24 h cycle. This intricated machinery is driven by specific genes, called “clock genes” that fine-tune body homeostasis. Stress of modern lifestyle can determine changes in hormone secretion, favoring the onset of infertility-related conditions that might reflect disfunctions within the hypothalamic–pituitary–gonadal axis. Consequently, the loss of rhythmicity in the suprachiasmatic nuclei might affect pulsatile sexual hormones release. Herein, we provide an overview of the recent findings, in both animal models and humans, about how fertility is influenced by circadian rhythm. In addition, we explore the complex interaction among hormones, fertility and the circadian clock. A deeper analysis of these interactions might lead to novel insights that could ameliorate the therapeutic management of infertility and related disorders.

Beer consumption negatively regulates hormonal reproductive status and reduces apoptosis in Leydig cells in peripubertal rats

Beer is one of the most popular alcoholic beverages consumed by young people. Ethanol intake is associated with harmful effects to the reproductive system. Bioactive compounds present in beer may diminish the toxics effect of ethanol. However, there is still little knowledge about the effect of beer consumption on hormonal regulation of male reproduction in organisms exposed to alcohol after the peripubertal age. Therefore, the aim of this study was to determine the influence of beer intake on plasma reproductive hormones, immunolocalization of cleaved caspase-3 (casp-3), and the level of the neuronal isoform of nitric oxide synthase (nNOS) in Leydig cells (LCs) in adolescent male Wistar rats. The animals, beginning at the age of 30 days, drank beer (10% ethanol; B2 group [2 weeks' exposure] and B4 group [4 weeks' exposure]), 10% ethanol solution (CE2 group [2 weeks' exposure] and CE4 group [4 weeks' exposure]), or water (C2 group [2 weeks' exposure] and C4 group [4 weeks' exposure]). Rats drinking beer for 4 weeks showed higher phenolic acid intake compared to rats drinking beer for 2 weeks. Rats exposed to beer for 4 weeks showed decreased plasma levels of follicle-stimulating hormone (FSH) and 17β-estradiol (E2) (3.173 ng/mL and 11.49 pg/mL, respectively), compared to the CE4 (5.293 ng/mL and 43.912 pg/mL, respectively) and the C4 groups (5.002 ng/mL and 41.121 pg mL, respectively). Expression of cleaved caspase-3 in LCs was lower in the B4 group rats, compared to the CE4 group rats (ID score: 1.676 vs. 2.190). No changes in nNOS expression were observed. Beer consumption revealed a similar negative effect on hormonal regulation of male reproductive function, but lower apoptosis in LCs may be beneficial for steroidogenic activity.

The gonadotropin system, lessons from animal models and clinical cases

This review article centers upon family of gonadotropin hormones which consists of two pituitary hormones - follicle-stimulating hormone (FSH) and luteinizing hormone (LH) as well as one non-pituitary hormone - human chorionic gonadotropin (hCG) secreted by placenta, and their receptors. Gonadotropins play an essential role in proper sexual development, puberty, gametogenesis, maintenance of pregnancy and male sexual differentiation during the fetal development. They belong to the family of glycoprotein hormones thus they constitute heterodimeric proteins built of common α subunit and hormone-specific β-subunit. Hitherto, several mutations in genes encoding both gonadotropins and their receptors have been identified in humans. Their occurrence resulted in a number of different phenotypes including delayed puberty, primary amenorrhea, hermaphroditism, infertility and hypogonadism. In order to understand the effects of mutations on the phenotype observed in affected patients, detailed molecular studies are required to map the relationship between the structure and function of gonadotropins and their receptors. Nonetheless, in vitro assays are often insufficient to understand physiology. Therefore, several animal models have been developed to unravel the physiological roles of gonadotropins and their receptors.

Conditional Deletion of FOXL2 and SMAD4 in Gonadotropes of Adult Mice Causes Isolated FSH Deficiency

The glycoprotein FSH, a product of pituitary gonadotrope cells, regulates ovarian follicle development in females and spermatogenesis in males. FSH is a heterodimer of the common α gonadotropin subunit and the hormone-specific FSHβ subunit (a product of the Fshb gene). Using a conditional knockout approach (Cre-lox), we previously demonstrated that Fshb expression in mice depends on the transcription factors forkhead box L2 (FOXL2) and SMAD4. Deletion of Foxl2 or Smad4 alone led to FSH deficiency, female subfertility, and oligozoospermia in males. Simultaneous deletion of the two genes yielded a greater suppression of FSH and female sterility. The Cre-driver used previously was first active during embryonic development. Therefore, it is unclear whether FOXL2 and SMAD4 play important roles in the development or adult function of gonadotropes, or both. To address this question, we developed a tamoxifen-inducible Cre-driver line, which enabled Foxl2 and Smad4 gene deletions in gonadotropes of adult mice. After tamoxifen treatment, females with previously demonstrated fertility exhibited profound reductions in FSH levels, arrested ovarian follicle development, and sterility. FSH levels were comparably reduced in males 1 or 2 months after treatment; however, spermatogenesis was unaffected. These data indicate that (1) FOXL2 and SMAD4 are necessary to maintain FSH synthesis in gonadotrope cells of adult mice, (2) FSH is essential for female reproduction but appears to be unnecessary for the maintenance of spermatogenesis in adult male mice, and (3) the inducible Cre-driver line developed here provides a powerful tool to interrogate gene function in gonadotrope cells of adult mice.

Molecular regulation of follicle-stimulating hormone synthesis, secretion and action

Follicle-stimulating hormone (FSH) plays fundamental roles in male and female fertility. FSH is a heterodimeric glycoprotein expressed by gonadotrophs in the anterior pituitary. The hormone-specific FSHβ-subunit is non-covalently associated with the common α-subunit that is also present in the luteinizing hormone (LH), another gonadotrophic hormone secreted by gonadotrophs and thyroid-stimulating hormone (TSH) secreted by thyrotrophs. Several decades of research led to the purification, structural characterization and physiological regulation of FSH in a variety of species including humans. With the advent of molecular tools, availability of immortalized gonadotroph cell lines and genetically modified mouse models, our knowledge on molecular mechanisms of FSH regulation has tremendously expanded. Several key players that regulate FSH synthesis, sorting, secretion and action in gonads and extragonadal tissues have been identified in a physiological setting. Novel post-transcriptional and post-translational regulatory mechanisms have also been identified that provide additional layers of regulation mediating FSH homeostasis. Recombinant human FSH analogs hold promise for a variety of clinical applications, whereas blocking antibodies against FSH may prove efficacious for preventing age-dependent bone loss and adiposity. It is anticipated that several exciting new discoveries uncovering all aspects of FSH biology will soon be forthcoming.

Interplay between p53 and Ink4c in spermatogenesis and fertility

The tumor suppressor p53, and the cyclin-dependent kinase inhibitor Ink4c, have been both implicated in spermatogenesis control. Both p53-/- and Ink4c-/- single knockout male mice are fertile, despite testicular hypertrophy, Leydig cell differentiation defect, and increased sperm count in Ink4c-/- males. To investigate their collaborative roles, we studied p53-/- Ink4c-/- dual knockout animals, and found that male p53-/- Ink4c-/- mice have profoundly reduced fertility. Dual knockout male mice show a marked decrease in sperm count, abnormal sperm morphology and motility, prolongation of spermatozoa proliferation and delay of meiosis entry, and accumulation of DNA damage. Genetic studies showed that the effects of p53 loss on fertility are independent of its downstream effector Cdkn1a. Absence of p53 also partially reverses the hyperplasia seen upon Ink4c loss, and normalizes the Leydig cell differentiation defect. These results implicate p53 in mitigating both the delayed entry into meiosis and the secondary apoptotic response that occur in the absence of Ink4c. We conclude that the cell cycle genes p53 and Ink4c collaborate in sperm cell development and differentiation, and may be important candidates to investigate in human male infertility conditions.

Expression of the gonadotropin receptors during follicular development

Background

Gonadotropins induce follicular development that leads to ovulation and luteinization. In women, the level of gonadotropins, along with the expression of their receptors, changes dynamically throughout the menstrual cycle. This study aimed to clarify the mechanisms underlying these phenomena.

Methods

The literature was reviewed, including that published by the authors.

Main findings (Results)

Follicle‐stimulating hormone receptor expression in the granulosa cells was induced by androgens that were derived from growth differentiation factor‐9‐stimulated theca cells. In the theca cells, luteinizing hormone receptor (LHR) expression was noted from their appearance. In the granulosa cells, follicle‐stimulating hormone (FSH) stimulation was essential for LHR expression. However, FSH alone was not sufficient to respond to the luteinizing hormone (LH) surge for oocyte maturation, ovulation, and subsequent luteinization. To achieve these stages, various local factors that were derived from the granulosa and theca cells in response to FSH and LH stimulation had to work synergistically in an autocrine/paracrine manner to strongly induce LHR expression. Following the LH surge, the LHR expression decreased markedly; miRNAs were involved in this transient LHR downregulation. Following ovulation, LHR expression drastically increased again toward luteinization.

Conclusion

The expression of gonadotropin receptors is controlled by sophisticated and complicated systems; a breakdown of this system could lead to ovulation disorders.

Relaxin affects cell organization and early and late stages of spermatogenesis in a coculture of rat testicular cells

Relaxin and its receptor RXFP1 are co-expressed in Sertoli cells, and relaxin can stimulate proliferation of Sertoli cells. In this study, we investigated a role of relaxin in spermatogenesis, using a short-term culture of testicular cells of the rat that allowed differentiation of spermatogonia to spermatids. Sertoli, germ, and peritubular myoid cells were the predominant cell types in the culture. Sertoli and germ cells expressed RXFP1. Cultures were incubated without (control) or with 0.5% fetal bovine serum (FBS) or 100 ng/mL H2 relaxin (RLN) for 2 days. Cell organization, number, and differentiation were analyzed after 2 (D2), 5 (D5) or 8 (D8) days of culturing. Although the proportion of germ cells decayed from D2 to D5, the relative contribution of HC, 1C, 2C, and 4C germ cell populations remained constant in the control group during the whole culture. RLN did not affect the proportion of germ cell populations compared with control, but increased gene and/or protein expression of the undifferentiated and differentiated spermatogonia markers PLZF and c-KIT, and of the post-meiotic marker Odf2 in D5. RLN favored organization of cells in tubule-like structures, the arrangement of myoid cells around the tubules, arrangement of c-KIT-positive spermatogonia at the basal region of the tubules, and expression of the cell junction protein β-catenin close to the plasma membrane region. Knockdown of relaxin with small interfering RNA (siRNA) reduced expression of β-catenin at the cell junctions, and shifted its expression to the nucleus. We propose that relaxin may affect spermatogenesis by modulating spermatogonial self renewal and favoring cell contact.

LIN28A marks the spermatogonial progenitor population and regulates its cyclic expansion

One of the hallmarks of highly proliferative adult tissues is the presence of a stem cell population that produces progenitor cells bound for differentiation. Progenitor cells undergo multiple transit amplifying (TA) divisions before initiating terminal differentiation. In the adult male germline, daughter cells arising from the spermatogonial stem cells undergo multiple rounds of TA divisions to produce undifferentiated clones of interconnected 2, 4, 8, and 16 cells, collectively termed A(undifferentiated) (A(undiff)) spermatogonia, before entering a stereotypic differentiation cascade. Although the number of TA divisions markedly affects the tissue output both at steady state and during regeneration, mechanisms regulating the expansion of the TA cell population are poorly understood in mammals. Here, we show that mice with a conditional deletion of Lin28a in the adult male germline, display impaired clonal expansion of the progenitor TA A(undiff) spermatogonia. The in vivo proliferative activity of Au(ndiff) spermatogonial cells as indicated by BrdU incorporation during S-phase was reduced in the absence of LIN28A. Thus, contrary to the role of LIN28A as a key determinant of cell fate signals in multiple stem cell lineages, in the adult male germline it functions as an intrinsic regulator of proliferation in the population of A(undiff) TA spermatogonia. In addition, neither precocious differentiation nor diminished capacity for self-renewal potential as assessed by transplantation was observed, suggesting that neither LIN28A itself nor the pool of Aal progenitor cells substantially contribute to the functional stem cell compartment.

Effects of icariin on reproductive functions in male rats

The present study investigated the effects and potential mechanism(s) of action of icariin on the reproductive functions of male rats. Adult rats were treated orally with icariin at doses of 0 (control), 50, 100, or 200 mg/kg body weight for 35 consecutive days. The results show that icariin had virtually no effect on the body weight or organ coefficients of the testes or epididymides. However, 100 mg/kg icariin significantly increased epididymal sperm counts. In addition, 50 and 100 mg/kg icariin significantly increased testosterone levels. Real-time PCR suggests icariin may be involved in testosterone production via mRNA expression regulation of genes such as peripheral type benzodiazepine receptor (PBR) and steroidogenic acute regulatory protein (StAR). Furthermore, 100 mg/kg icariin treatment also affected follicle stimulating hormone receptor (FSHR) and claudin-11 mRNA expression in Sertoli cells. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels were measured in the testes; 50 and 100 mg/kg icariin treatment improved antioxidative capacity, while 200 mg/kg icariin treatment upregulated oxidative stress. These results collectively suggest that icariin within a certain dose range is beneficial to male reproductive functions; meanwhile, higher doses of icariin may damage reproductive functions by increasing oxidative stress in the testes.

Unpredictable chronic stress-induced reproductive suppression associated with the decrease of kisspeptin immunoreactivity in male mice

Environmental stress affects various parts of mammals typically through the circulation of stress hormones. It has been identified as one of the possible reasons for male reproductive difficulties, but the complex mechanisms responsible for stress-induced reproductive suppression are poorly understood. Here, we examined the relationship between chronic environmental stress and hypothalamic kisspeptin, a recently discovered upstream regulator of the reproductive endocrine feedback system. We studied male mice under an unpredictable chronic stress procedure to replicate the situation of animals under chronic stress. Histological and immunohistochemical analyses were performed focusing on kisspeptin neurons in the arcuate hypothalamic nucleus (ARC) and DNA fragmented cells in seminiferous tubules. Although the ARC was not morphologically altered in either the stressed or non-stressed group, granular kisspeptin immunoreactivities decreased slightly in the stress group. In the testes of the stress group, several signs of testicular degeneration were observed, including increased numbers of ssDNA-positive cells per seminiferous tubule, thinning, vacuoled seminiferous epithelia and multinucleated giant cells. The decreases in kisspeptin in the stress group might be due to other hypothalamic peptides, such as corticotropin-releasing hormone and leptin, whose receptors are known to coexpress in the ARC. In addition, environmental stress directly and indirectly affects testicular function through stress hormones and gonadotropins. In summary, our findings enhance the understanding of stress-induced reproductive suppression possibly mediated by kisspeptin in the ARC.

The forkhead transcription factor, FOXP3: a critical role in male fertility in mice

Fertility is dependent on the hypothalamic-pituitary-gonadal axis. Each component of this axis is essential for normal reproductive function. Mice with a mutation in the forkhead transcription factor gene, Foxp3, exhibit autoimmunity and infertility. We have previously shown that Foxp3 mutant mice have significantly reduced expression of pituitary gonadotropins. To address the role of Foxp3 in gonadal function, we examined the gonadal phenotype of these mice. Foxp3 mutant mice have significantly reduced seminal vesicle and testis weights compared with Foxp3(+/Y) littermates. Spermatogenesis in Foxp3 mutant males is arrested prior to spermatid elongation. Activation of luteinizing hormone signaling in Foxp3 mutant mice by treatment with human chorionic gonadotropin significantly increases seminal vesicle and testis weights as well as testicular testosterone content and seminiferous tubule diameter. Interestingly, human chorionic gonadotropin treatments rescue spermatogenesis in Foxp3 mutant males, suggesting that their gonadal phenotype is due primarily to a loss of pituitary gonadotropin stimulation rather than an intrinsic gonadal defect.

Milestones in contraceptive vaccines development and hurdles in their application

Contraceptive vaccines have been proposed for controlling the growing human population and wildlife population management. Multiple targets such as gonadotropin releasing hormone (GnRH), luteinizing hormone, follicle stimulating hormone, gonadotropin receptors, sperm-specific proteins and zona pellucida glycoproteins have been exploited to develop contraceptive vaccine and their efficacy investigated and shown in various experimental animal models. Vaccines based on GnRH have found application in immuno-castration of male pigs for prevention of boar-taint. Vaccines based on zona pellucida glycoproteins have shown promising results for population management of wild horses and white-tailed deer. Phase II clinical trials in women with β-human chorionic gonadotropin (β-hCG)-based contraceptive vaccine established proof of principle that these can be developed for human application. Block in fertility by β-hCG contraceptive vaccine was reversible. Further research inputs are required to establish the safety of contraceptive vaccines, improve their immunogenicity and to develop novel vaccine delivery platforms for providing long lasting immunity.

Free fatty acids induce Lhb mRNA but suppress Fshb mRNA in pituitary LβT2 gonadotropes and diet-induced obesity reduces FSH levels in male mice and disrupts the proestrous LH/FSH surge in female mice

Female obesity is associated with insulin resistance, hyperandrogenemia, and reproductive dysfunction. We hypothesized that elevated free fatty acids (FFAs) might directly modulate pituitary gonadotropin production. FFAs caused a time- and dose-dependent increase in phosphorylation of the MAPKs p38MAPK, c-Jun N-terminal kinase (JNK)-1/2, and ERK1/2 in LβT2 gonadotrope cells. Furthermore, FFAs up-regulated Lhb mRNA expression acutely, an effect that was blocked by JNK inhibition, but suppressed Fshb mRNA expression, an effect that was independent of MAPK signaling. FFAs enhanced the activation of the MAPKs in the presence of GnRH, although the cotreatment did not alter Lhb induction but did eliminate the GnRH induction of Fshb. FFAs also suppressed activin-induced Fshb expression. Knockdown experiments showed that the FFA effect on the inflammatory kinases p38MAPK and JNK and on Lhb, but not Fshb, mRNA expression is mediated via toll-like receptor-2 and toll-like receptor-4 and was mimicked by lipopolysaccharide stimulation. In vivo, male C57BL/6 mice on a high-fat diet showed reduced FSH levels consistent with the suppression of Fshb seen in vitro. Histological analysis of the testes showed an increased number of abnormal seminiferous tubules. Female mice on a high-fat diet lacked the expected proestrus LH and FSH surge and exhibited an increase in the number of days at estrus and a reduced number of days at proestrus, and ovaries had significantly fewer corpora lutea. Taken together, our findings suggest that lipid excess can lead to reproductive defects in both male and female mice.

Assessment of circulating hormones in regulatory toxicity studies II. Male reproductive hormones

When test article-related testicular toxicity or Leydig cell tumors are identified in nonclinical studies, the measurement of circulating hormones such as luteinizing hormone, follicle-stimulating hormone, inhibin, testosterone, or prolactin is often considered in order to aid mechanistic investigations or to identify potential biomarkers in man. Although some hormone levels are relatively constant, others are subject to wide variability owing to pulsatility of secretion, diurnal rhythms, and stress. To avoid being misled, it is important that this variation is factored into any study design that includes hormone measurements. Since all these possibilities start from the pathologist's reading of the tissue sections, we begin with a review of the morphologic changes that are tied to underlying alterations in hormones. We then provide the reader with basic information and representative hormone data, including coefficients of variation, for the major male reproductive hormones in the three main nonclinical species (rats, dogs, and cynomolgus monkeys). Power and probability tables for rats and dogs allow estimates of the number of animals or samples needed to provide a given likelihood of detecting a hormonal change of a given size. More importantly, we highlight the variability of this process and the real value in readers developing this information at their own site.

The effects of type 1 diabetes on the hypothalamic, pituitary and testes axis

Type 1 diabetes is an autoimmune disorder characterized by a lack of insulin production by the beta cells of the pancreas. This lack of insulin causes a variety of systemic effects on whole-body metabolism. Poorly managed type 1 diabetes can lead to cardiovascular disease, diabetic neuropathy, and diabetic retinopathy. Increasingly, even well-managed type 1 diabetic patients show damage to peripheral organs related to complications from the disease. The central role of insulin in energy homeostasis also renders it an important signaling factor in the reproductive tract. type 1 diabetes has now been demonstrated to cause defects in sperm and testes. The aim of this review is to present the known effects of insulin's role in the function of the male reproductive tract. These effects might be mediated through hormonal alterations in the hypothalamic pituitary gonadal axis or through the direct interaction of insulin on the testes and sperm cells. Although fertility complications also occur in type 2 diabetic males, this review will focus on the defects specifically linked with the lack of insulin seen in type 1 diabetes.

An EF-hands protein, centrin-1, is an EGTA-sensitive SUMO-interacting protein in mouse testis

A multifunctional calcium-binding protein, centrin-1, is specifically expressed in male germ cells, certain neurons and ciliated cells. We identified centrin-1 as a protein interacting with SUMO-2/3 using yeast two-hybrid screening of a mouse testicular cDNA library. In bead halo assays, the interaction between centrin-1 and SUMO-2/3 was reduced in the presence of EGTA and facilitated by the addition of CaCl₂. immunostaining of seminiferous tubules in 35-day-old mouse testes revealed that cells in the layer containing spermatogonia showed colocalization of SUMO-2/3 with centrin-1 in cytoplasmic spots. Identification of centrin-1 as the EGTA-sensitive SUMO-2/3-interacting protein indicates the possible role of calcium in modulating the centrin-1-SUMO-2/3 interaction and suggests the importance of this interaction in mouse testis.

Testicular signaling is the potential target of perfluorooctanesulfonate-mediated subfertility in male mice

Perfluorooctanesulfonate (PFOS) was produced and used by various industries and in consumer products. Because of its persistence, it is ubiquitous in air, water, soil, wildlife, and humans. Although the adverse effects of PFOS on male fertility have been reported, the underlying mechanisms have not yet been elucidated. Here, for the first time, the effects of PFOS on testicular signaling, such as gonadotropin, growth hormone, insulin-like growth factor, and inhibins/activins were shown to be directly related to male subfertility. Sexually mature 8-wk-old CD1 male mice were administered by gavages in corn oil daily with 0, 1, 5, or 10 mg/kg PFOS for 7, 14, or 21 days. Serum concentrations of testosterone and epididymal sperm counts were significantly lower in the mice after 21 days of the exposure to the highest dose compared with the controls. The expression levels of testicular receptors for gonadotropin, growth hormone, and insulin-like growth factor 1 were considerably reduced on Day 21 in mice exposed daily to 10 or 5 mg/kg PFOS. The transcript levels of the subunits of the testicular factors (i.e., inhibins and activins), Inha, Inhba, and Inhbb, were significantly lower on Day 21 of daily exposure to 10, 5, or 1 mg/kg PFOS. The mRNA expression levels of steroidogenic enzymes (i.e., StAR, CYP11A1, CYP17A1, 3beta-HSD, and 17beta-HSD) were notably reduced. Therefore, PFOS-elicited subfertility in male mice is manifested as progressive deterioration of testicular signaling.

Puberty is delayed in male mice with dextran sodium sulfate colitis out of proportion to changes in food intake, body weight, and serum levels of leptin

In boys, inflammatory bowel disease often results in delayed puberty associated with decreased bone mineral density and decreased linear growth. Our goal was to investigate whether pubertal timing and levels of leptin differed between prepubertal male mice with colitis and food-restricted (FR) mice maintained at a similar weight. We induced colitis in 32-d-old male mice using dextran sodium sulfate (DSS), resulting in 10 d of worsening colitis. We followed up these mice for separation of the prepuce from the glans penis as a marker of pubertal progression. Compared with free-feeding control mice, DSS and FR mice had significantly lower weight on d 7-10 of treatment. DSS mice had later puberty than control and FR mice. DSS mice also had smaller testes, lower FSH levels, increased systemic cytokines, and increased colonic inflammation by histology. Leptin levels were similar between DSS and FR mice, whereas both had decreases in leptin compared with controls. We conclude that DSS colitis causes delayed puberty in sexually immature male mice beyond what is seen among FR mice of similar weight, food intake, and leptin levels. These experiments provide support for the hypothesis that pubertal delay in colitis is influenced by factors beyond poor weight gain alone.

Differential time course of FSH/FSH receptor complex endocytosis within sertoli and germ cells during rat testis development

Follicle-stimulating hormone (FSH) is required for initiation and maintenance of spermatogenesis, a dynamic process of cell proliferation and maturation. By using FSH-gold particles and pulse-chase experiments, we analyzed the kinetics of FSH endocytosis in Sertoli and germ cells during development. Ultrastructural time-dependent analysis demonstrates that FSH was first located on plasma membrane, before being accumulated within the endosomal compartment, in the early endosomes, identified by morphological criteria and Rab-5 colocalization. Thereafter, FSH-gold was routed to the degradation pathway. The FSH endocytosis kinetic was similar in Sertoli cells, spermatogonia and spermatocytes. However, quantitative analysis of gold particles revealed differences in the dynamic of FSH accumulation in the endosomes between immature and mature rats. This age-dependent kinetic of FSH endocytosis, mostly detectable by ultrastructural analysis associated with quantitative data, argues for a potential new regulatory mechanism of the FSH signalling pathway that could occur during maturation of testicular cells.

The immunoexpression of FSH-R in the ductuli efferentes and the epididymis of men and rat: effect of FSH on the morphology and steroidogenic activity of rat epididymal epithelial cells in vitro

The Sertoli cells were regarded as the only target for FSH in male reproductive system. The expression of FSH receptor (FSH-R) was detected also in epithelial cells of the caput epididymis of rat and monkey. We showed in the immunohistochemistry study the expression of FSH-R in rat and human ductuli efferentes and the caput, corpus, and cauda epididymis, moreover, by Western blot analysis in the caput and cauda epididymis of rat. Additionally, we presented that the morphology of rat epididymal epithelial cells in vitro was affected by FSH, and FSH stimulation resulted in the increase of 17β-estradiol synthesis by rat caput epididymal cells in dose-depended manner. In conclusion, the identification of FSH receptors in human and rat epididymides supports our results that the epididymis is a target organ not only for LH but additionally for FSH. On the basis of the results we showed for the first time that morphology of epididymal epithelial cells and epididymal steroidogenesis can be regulated by FSH.

Developmental regulation of p70 S6 kinase by a G protein-coupled receptor dynamically modelized in primary cells

The mechanisms whereby G protein-coupled receptors (GPCR) activate signalling pathways involved in mRNA translation are ill-defined, in contrast to tyrosine kinase receptors (TKR). We compared a GPCR and a TKR, both endogenously expressed, for their ability to mediate phosphorylation of 70-kDa ribosomal S6 kinase p70S6K in primary rat Sertoli cells at two developmental stages. In proliferating cells stimulated with follicle-stimulating hormone (FSH), active p70S6K was phosphorylated on T389 and T421/S424, through cAMP-dependent kinase (PKA) and phosphatidyl-inositide-3 kinase (PI3K) antagonizing actions. In FSH-stimulated differentiating cells, active p70S6K was phosphorylated solely on T389, PKA and PI3K independently enhancing its activity. At both developmental stages, insulin-induced p70S6K regulation was consistent with reported data. Therefore, TKR and GPCR trigger distinct p70S6K active conformations. p70S6K developmental regulation was formalized in a dynamic mathematical model fitting the data, which led to experimentally inaccessible predictions on p70S6K phosphorylation rate.

Transcriptional profiling of the hormone-responsive stages of spermatogenesis reveals cell-, stage-, and hormone-specific events

Spermatogenesis occurs within the highly complex seminiferous epithelium. This cyclic process is accompanied by dynamic stage-specific transcriptional changes and is driven by androgens and FSH by mechanisms that are unclear. Here we report the impact of acute androgen and FSH suppression on the transcriptional dynamics of the seminiferous epithelium. We used transcriptional profiling to compare the most hormone-sensitive seminiferous epithelial stages (VII and VIII) from control and hormone-suppressed adult rats, together with publicly available datasets to delineate stage- and cell-specific transcriptional changes. The analyses reveal that, in these stages, there was a hormone-responsive down-regulation of spermatogonial and Sertoli cell transcripts maximally expressed in the earlier spermatogenic stages (I-VI). Transcripts expressed in Sertoli cells from stage VII and beyond were both up- and down-regulated by hormone suppression, with lysosome function, immune system-related genes, and lipid metabolism predicted to be hormone responsive. Hormone-responsive genes with putative roles in integrin-mediated cell adhesion were also identified. In pachytene spermatocytes, there was an initiation of transcription likely important for the completion of meiosis. A transcriptional switch in round spermatids was observed, from a hormone-responsive down-regulation of transcripts expressed in steps 1-7 spermatids to a hormone-independent up-regulation of transcripts expressed in steps 8-11 and likely involved in spermatid differentiation and DNA compaction. This study points to the existence of hormone-responsive global transcriptional repressors in Sertoli cells, spermatogonia, and spermatids and reveals novel and diverse cell-specific responses of the seminiferous epithelium to hormone suppression.

SEX STEROIDS AND SPERMATOGENESIS IN THE AFRICAN CATFISH (CLARIAS GARIEPINUS)

Little is known about the physiological regulations of spermatogenesis of the African catfish (Clarias gariepinus), a species used as an experimental model for two decades. After a brief introduction to the cystic type of spermatogenesis in fish, the role of androgens and estrogens will be discussed, leading to a conclusion that androgens are required for spermatogenesis while their mode of action is poorly understood. In the cystic mode of spermatogenesis in fish, the Sertoli cells are formed cystic, in the somniferous lobules enclosing a single germ cell clone, providing suitable experimental models to address questions of relevance for vertebrate spermatogenesis in general.

Targeted ablation of the WW domain-containing oxidoreductase tumor suppressor leads to impaired steroidogenesis

The WW domain-containing oxidoreductase (WWOX) gene encodes a 46-kDa tumor suppressor. The Wwox protein contains two N-terminal WW domains that interact with several transcriptional activators containing proline-tyrosine motifs and a central short-chain dehydrogenase/reductase domain that has been suggested to play a role in steroid metabolism. Recently, we have shown that targeted deletion of the Wwox gene in mice leads to postnatal lethality and defects in bone growth. Here, we report that Wwox-deficient mice display impaired steroidogenesis. Mutant homozygous mice are born with gonadal abnormalities, including failure of Leydig cell development in testis and reduced theca cell proliferation in ovary. Furthermore, Wwox(-/-) mice displayed impaired gene expression of key steroidogenesis enzymes. Affymetrix microarray gene analysis revealed differentially expressed related genes in steroidogenesis in knockout mice testis and ovary as compared with control mice. These results demonstrate the essential requirement for the Wwox tumor suppressor in proper steroidogenesis.

Promotion of spermatogonial proliferation by neuregulin 1 in newt (Cynops pyrrhogaster) testis

We have previously shown that mammalian follicle-stimulating hormone (FSH) promotes the proliferation of spermatogonia and their differentiation into primary spermatocytes in organ culture of newt testis. In the current study, we performed microarray analysis to isolate local factors secreted from somatic cells upon FSH treatment and acting on the germ cells. We identified neuregulin 1 (NRG1) as a novel FSH-upregulated clone homologous to mouse NRG1 known to control cell proliferation, differentiation and survival in various tissues. We further isolated cDNAs encoding two different clones. Amino acid sequences of the two clones were 75% and 94% identical to Xenopus leavis immunoglobulin (Ig)-type and cysteine-rich domain (CRD)-type NRG1, respectively, which had distinct sequences in their N-terminal region but identical in their epidermal growth factor (EGF)-like domain. Semi-quantitative and quantitative PCR analyses indicated that both clones were highly expressed at spermatogonial stage than at spermatocyte stage. In vitro FSH treatment increased newt Ig-NRG1 (nIg-NRG1) mRNA expression markedly in somatic cells, whereas newt CRD-NRG1 (nCRD-NRG1) mRNA was only slightly increased by FSH. To elucidate the function of newt NRG1 (nNRG1) in spermatogenesis, recombinant EGF domain of nNRG1 (nNRG1-EGF) was added to organ and reaggregated cultures with or without somatic cells: it promoted spermatogonial proliferation in all cases. Treatment of the cultures with the antibody against nNRG1-EGF caused remarkable suppression of spermatogonial proliferation activated by FSH. These results indicated that nNRG1 plays a pivotal role in promoting spermatogonial proliferation by both direct effect on spermatogonia and indirect effect via somatic cells in newt testes.

Krüppel-like factor 4 is involved in functional differentiation of testicular Sertoli cells

Krüppel-like factor 4 (KLF4) is a pleiotropic zinc finger transcription factor that regulates genes being involved in differentiation and cell-cycle control. Knockout studies revealed a critical function for KLF4 in the terminal differentiation of many epithelial cells. In testicular Sertoli cells, Klf4 is strongly inducible by the glycoprotein follicle stimulating hormone (FSH). Because KLF4 is essential for postnatal survival in mice, we deleted Klf4 specifically in Sertoli cells using the Cre/loxP system. Importantly, around postnatal day 18, a critical period of terminal Sertoli cell differentiation, mutant seminiferous tubules exhibited a disorganized germinal epithelium and delayed lumen formation. The ultrastructural finding of highly vacuolized Sertoli cell cytoplasm and the identification of differentially expressed genes, which are known to play roles during vesicle transport and fusion or for maintenance of the differentiated cell state, suggest impaired apical secretion of the Sertoli cell. Interestingly, a high proportion of all identified genes was localized in a small subregion of chromosome 7, suggesting coordinated regulation. Intriguingly, adult mutant mice are fertile and show normal testicular morphology, although the testosterone levels are decreased. In summary, KLF4 plays a significant role for proper and timely Sertoli cell differentiation in pubertal mice.

Reduced urea flux across the blood-testis barrier and early maturation in the male reproductive system in UT-B-null mice

A urea-selective urine-concentrating defect was found in transgenic mice deficient in urea transporter (UT)-B. To determine the role of facilitated urea transport in extrarenal organs expressing UT-B, we studied the kinetics of [14C]urea distribution in UT-B-null mice versus wild-type mice. After renal blood flow was disrupted, [14C]urea distribution was selectively reduced in testis in UT-B-null mice. Under basal conditions, total testis urea content was 335.4 ± 43.8 μg in UT-B-null mice versus 196.3 ± 18.2 μg in wild-type mice ( P < 0.01). Testis weight in UT-B-null mice (6.6 ± 0.8 mg/g body wt) was significantly greater than in wild-type mice (4.2 ± 0.8 mg/g body wt). Elongated spermatids were observed earlier in UT-B-null mice compared with wild type mice on day 24 versus day 32, respectively. First breeding ages in UT-B knockout males (48 ± 3 days) were also significantly earlier than that in wild-type males (56 ± 2 days). In competing mating tests with wild-type males and UT-B-null males, all pups carried UT-B-targeted genes, which indicates that all pups were produced from breeding of UT-B-null males. Experiments of the expression of follicle-stimulating hormone receptor (FSHR) and androgen binding protein (ABP) indicated that the development of Sertoli cells was also earlier in UT-B-null mice than that in wild-type mice. These results suggest that UT-B plays an important role in eliminating urea produced by Sertoli cells and that UT-B deletion causes both urea accumulation in the testis and early maturation of the male reproductive system. The UT-B knockout mouse may be a useful experimental model to define the molecular mechanisms of early puberty.

Chronic Treatment of Male Tammar Wallabies with Deslorelin Implants During Pouch Life: Effects on Development, Puberty, and Reproduction in Adulthood1

The present study evaluated the effects of chronic GnRH agonist (deslorelin) treatment on sexual maturation in the male tammar wallaby. Slow-release deslorelin or placebo implants were administered to male pouch young (n = 10/group) when they were between 180 and 200 days old, to determine if disruption of the pituitary-testicular axis during development altered the timing of sexual maturation or had long-term effects on adult reproductive function. Deslorelin treatment caused retardation of testicular growth and reduced the serum FSH and testosterone concentrations between 12 and 24 mo of age. Maturation of the hypothalamic-pituitary-testicular axis was also delayed in treated animals at 13 and 19 mo of age. Despite these alterations in the pattern and timing of neuroendocrine development, sexual maturation was not permanently blocked in these animals and deslorelin-treated animals reached sexual maturity at the same age as treated animals, as evidenced by a fully functional pituitary-testicular axis and proven fertility at 25 mo of age. The ability of the treated animals to reach puberty at the same time as control animals, despite delayed maturation of the hypothalamic-pituitary-testicular axis, suggests that puberty in the male tammar wallaby is additionally regulated by other, gonadotropin-independent factors.

Heat treatment induces liver receptor homolog-1 expression in monkey and rat sertoli cells

We demonstrated in this study that liver receptor homolog-1 (LRH-1) was expressed in the round spermatids in normal monkey testis, and no LRH-1 signal was observed in the Sertoli cells. After local warming (43 C) the monkey testis, however, LRH-1 expression was induced in the Sertoli cells in coincidence with activation of cytokeratin 18 (CK-18), a Sertoli cell dedifferentiated marker. Furthermore, we isolated rat primary Sertoli cells from testes at various stages of development and treated with 43 C water in vitro. The changes in LRH-1 as well as CK-18 expression were analyzed by confocal immunohistochemistry and Western blot. The results showed that LRH-1 was stage-dependently expressed in the Sertoli cells; no LRH-1-positive signal was detected in the cells obtained from the testes of adult rat on d 60 after birth when mature spermatozoa in the testis was completed. However, the mature Sertoli cells were warmed at the 43 C water bath for 15 min, and the LRH-1 signal was remarkably induced in a time-dependent manner, just like the changes of CK-18 expression in the Sertoli cells, suggesting that the heat-induced dedifferentiation of the mature Sertoli cells might be related to LRH-1 regulation. LRH-1 expression induced by the heat treatment was completely inhibited by the addition of ERK inhibitor U0126 in the culture, indicating that the heat-induced LRH-1 expression in the Sertoli cells may be regulated via ERK1/2 activation pathway. Testosterone was found to have no such effect on LRH-1 expression in the monkey and rat Sertoli cells.

Targeted and reversible disruption of the blood-testis barrier by an FSH mutant-occludin peptide conjugate

The blood-testis barrier (BTB) is one of the tightest blood-tissue barriers in mammals. As such, it poses a challenge to deliver any drugs to the seminiferous epithelium of the testis, such as a nonhormonal male contraceptive. To circumvent this problem, a genetically engineered follicle-stimulating hormone (FSH) mutant protein was produced in Spodoptera furgiperda (Sf)-9 insect cells to serve as a testis-specific carrier. Subsequently, a 22-amino acid peptide corresponding to the second extracellular loop of occludin, which was known to disrupt BTB integrity in vivo, was inserted to the FSH mutant by polymerase chain reaction (PCR), as well as chemical cross-linking. This molecule was found to have negligible hormonal activity but was still capable of binding to FSH receptors, which are restricted to Sertoli cells in mammals. When this FSH mutant-occludin peptide conjugate was administered to adult rats at 40 microg/adult rat (approximately 300 gm b.w.) via intraperitoneally (i.p.) injection, it induced transient and reversible disruption of the BTB, while at 150 microg/rat, it induced partial germ cell loss from the testis, particularly elongating/elongate spermatids. Most importantly, this effect was limited to the BTB without compromising the TJ-barrier integrity or cell adhesion in epithelia of other organs, such as kidney, liver, and small intestine. In summary, the use of an FSH mutant-occludin peptide conjugate is a feasible nanodevice to transiently compromise the BTB.

Steroidogenic activities of follicle-stimulating hormone in the ovary of Japanese eel, Anguilla japonica

To clarify the physiological functions of follicle-stimulating hormone (FSH) during oogenesis in Japanese eel, Anguilla japonica, the steroidogenic activities of recombinant Japanese eel FSH (rjeFSH) were assessed in the eel ovary. Female eel were injected with salmon pituitary homogenate to enhance the ovarian development, and the ovaries at different developmental stages were subjected to steroidogenic bioassay. These ovaries could be classified into three types according to oocyte growth and development of ovarian follicular cells. The type-A ovary possessed poorly developed follicular cells around pre- or early vitellogenic oocytes, and rjeFSH did not induce sex steroid secretion. Testosterone (T) secretion was stimulated by rjeFSH in the type-B ovary with developed theca cells and undeveloped granulosa cells around early to mid-vitellogenic oocytes, whereas estradiol-17beta (E2) secretion was not enhanced. The rjeFSH stimulated both T and E2 secretion in a dose-dependent manner from the type-C ovary with fully developed theca and granulosa cells around mid-vitellogenic oocytes. Salmon GTH fraction (sGTH) and a membrane permeable cAMP analogue, 8-bromo-cAMP (8-Br-cAMP) also enhanced T and E2 secretion from the type-C ovary. Human chorionic gonadotropin (hCG) similarly enhanced T secretion, but failed to stimulate E2 secretion from the type-C ovary, suggesting different effects on steroidogenic activities between eel FSH and hCG in eel ovary. There was a positive correlation between the oocyte diameter and E2 secretion from eel ovaries stimulated by rjeFSH. These results suggest that aromatase activity is accelerated by eel FSH in the granulosa cells, which develop following theca cell development in this species.

What have we learned about gonadotropin function from gonadotropin subunit and receptor knockout mice?

A number of biochemical and physiological studies elucidated the roles of pituitary and placental glycoprotein hormones. Advances in the past two decades in manipulating the mouse genome by random or site-specific mutagenesis have heralded a new dimension to our understanding of the biology of gonadotropins. It is now possible to model many human reproductive disorders involving gonadotropins/gonadotropin-signaling in the mouse. Mutant mice selectively lacking either FSH or LH or their cognate receptors have been generated. The gonadotropin ligand and the corresponding receptor knockout mice mostly phenocopy each other. Analyses with these genetic models confirmed earlier physiological studies; in addition they also revealed novel roles for gonadotropins previously unrecognized. While FSH action seems dispensable for male but not female fertility, absence of LH causes infertility in both the sexes. While Sertoli cell number and germ cell carrying capacity of the Sertoli cells in compromised in FSH mutants, both somatic and germ cell lineages are affected in the LH mutants resulting in complete male infertility. FSH mutant females demonstrate a preantral stage block in folliculogenesis and FSH alone is not sufficient to promote full folliculogenesis in the absence of LH. Pre-ovulatory stage follicles do not form and most of the follicles undergo apoptosis in the absence of LH. Many extra-gonadal phenotypes have been described for the receptor knockout mice and whether these bear any resemblances to those in patients with similar inactivating mutations in the receptors for FSH and LH remains an open question. Thus the in vivo models will continue to have a significant impact in understanding gonadotropin physiology and pathophysiology and serve as novel genetic tools to study signaling mechanisms in the gonads.

Contraceptive vaccines

The world's population is growing at a tremendous rate, affecting growth and development. Apart from this population growth, unintended pregnancies resulting in elective abortions continue to be a major public health issue. In over half of these unintended pregnancies, the women have used some type of contraception. Thus, there is an urgent need for a better method of contraception that is acceptable, effective and available. The contraceptive choices available to women at this time include steroid contraceptives, intrauterine devices, barrier methods, spermicides, natural family planning, male and female sterilisation, and recently available emergency contraceptives. Contraceptive vaccines (CVs) may provide viable and valuable alternatives that can fulfill most, if not all, properties of an ideal contraceptive. Since both the developed and most of the developing nations have an infrastructure for mass immunisation, the development of vaccines for contraception is an exciting proposition. The molecules that are being explored for CV development either target gamete production (gonadotropin releasing hormone, follicle-stimulating hormone and luteinising hormone), gamete function (zona pellucida [ZP] proteins and sperm antigens) or gamete outcome (human chorionic gonadotropin [hCG]). Disadvantages of CVs targeting gamete production are that they affect sex steroids and/or show only a partial effect in reducing fertility. CVs targeting gamete function are better choices. Vaccines based on ZP proteins are quite efficacious in producing contraceptive effects. However, they invariably induce oophoritis affecting sex steroids. Sperm antigens constitute the most promising and exciting targets for CVs. Several sperm-specific antigens have been delineated in several laboratories and are being actively explored for CV development. Antisperm antibody-mediated immunoinfertility provides a naturally occurring model to indicate how an antisperm vaccine will work in humans. Vaccines targeting gamete outcome primarily focus on the hCG molecule. The hCG vaccine is the first vaccine to undergo phase I and II clinical trials in humans. Both the efficacy and the lack of immunotoxicity have been reasonably well demonstrated for this vaccine. The present studies focus on increasing the immunogenicity and efficacy of this birth control vaccine.

Control of spermatogenesis in primate and prospect of male contraception

The present review is a summary of mechanisms of spermatogenesis in primates with emphasis on anti-spermatogenesis of testosterone (T), gossypol, and "testicular heat stress" for development of male contraception, Both FSH and testosterone stimulate all phases of spermatogenesis. FSH is capable of amplifying the population of the differential spermatogonia (B1, B2, B3 and B4) and controls the spermatogonia production rate, and, in synergy with testosterone, regulating spermatogenesis in adult monkeys. Pituitary FSH beta gene expression is governed by a feedback of Beta inhibin, which is a major component of the testicular negative feedback signals. Beta inhibin secreted by Sertoli cells is in turn inhibited by testosterone from Leydig cells under the control of LH. Disturbance of the normal interaction of pituitary FSH with Sertoli cell Beta inhibin is responsible for azoospermia or oligozoospermia induced by exogenous T. Three possible regimens of T, gossypol and "heat stress" have been suggested for male contraception. They act on different sites and stages of spermatogenesis in testis or sperm activity in epididymis. Apoptosis induced by testosterone occurs mainly at staged VII-VIII of spermatogenesis while that by testicular "heat stress" mostly occurs at stages I-IV and X-XII. Low dose of gossypol mainly influences the sperm activity in the epididymis although it also acts on testicular spermatids.

Molecular pharmacology of gonadotropins

Gonadotropins have been studied in biological systems for decades and many of their properties are well defined. These include pharmacological properties such as affinity, stability, and pharmacokinetics also used to characterize drugs. Technologies applied to research on gonadotropins have led to the creation of hormone analogs with alterations to one or more of these proper-ties. Some of these analogs have potential therapeutic applications. A challenge to realizing this potential is the accurate prediction of how these compounds will perform in humans. This could be facilitated by advances in biological models and the understanding of specific effects of the hormones on their receptors.

Spermatogenesis and sperm transit through the epididymis in mammals with emphasis on pigs

Starting from the period of testis differentiation, the Sertoli cell plays a pivotal role in the development of a functional testis. FSH is the major mitotic factor for Sertoli cells. Because the supporting capacity of Sertoli cells is relatively fixed for each species, their total number per testis, established just before puberty (approximately 4 months in pigs), dictates the potential for sperm production. In contrast to Sertoli cells that are still undifferentiated, mature Leydig cells are already present at birth in pigs. Spermatogenesis lasts from 30 to 75 days in mammals, and this time period is under the control of the germ cell genotype. In boars, each spermatogenic cycle and the entire spermatogenic process lasts 8.6-9.0 and approximately 40 days, respectively. The sperm transit through the epididymis takes approximately 10 days in pigs and this is within the range cited for most mammals. Germ cell loss occurs normally during spermatogenesis, mainly during the spermatogonial and meiotic phases. In pigs, significant germ cell loss also takes place during spermiogenesis. In mammals in general, including pigs, only 2-3 out of a possible 10 spermatozoa are produced from each differentiated type A1 spermatogonium. The high supporting capacity of Sertoli cells and the short duration of the spermatogenic cycle are the main factors responsible for the comparatively high spermatogenic efficiency of pigs.

In vitro elucidation of substrate specificity and bioassay of proprotein convertase 4 using intramolecularly quenched fluorogenic peptides

The fourth member of Ca2+-dependent mammalian secretory subtilase, PC4 (proprotein convertase 4), is primarily expressed in testicular germ cell and ovarian macrophage. Its role in sperm fertilization and in early embryonic development has been demonstrated earlier through several studies, including those with PC4 null mice. A number of physiological substrates found in reproductive tissues have been postulated or identified for PC4 by various biochemical studies. These include growth factors IGF-1 (insulin-like growth factor-1) and IGF-2, hormonal polypeptide proPACAP (where PACAP stands for pituitary adenylate cyclase-activating polypeptide) and a number of surface proteins of ADAM (ADisintegrin And Metalloproteinase-like) family such as ADAM-1 (fertilin a), ADAM-2 (fertilin b), ADAM-3 (procyritestin) and ADAM-5. To provide further evidence in support of this notion and also to study the substrate specificity and bioassay of PC4, a series of intramolecularly quenched fluorogenic peptides containing the cleavage sites and several mutants were prepared. A comparative kinetic analysis and measurement of Vmax (app)/Km (app) ratio of these fluorogenic substrates against PC4 and PC7 revealed that the mutant variants of h (human) proPACAP and m (mouse) ADAM-5 derived peptides Q-PACAP141-151-mutant [Abz-141RVKNKGRRI150P151SY(NO2)-A-CONH2] (150A151Y replaced by PS) and Q-ADAM-5380-388-mutant [Abz-380E381PKPARRP388RY(NO2)A-CONH2] (381R replaced by P) are most efficiently and selectively cleaved by PC4. Using these two and Q-IGF-263-71 peptides, we showed that the sperm extract of normal adult mice is much higher when compared with that of PC4-null mice. This suggests that these fluorogenic peptides are useful for specific bioassay of PC4 activity. In addition, kinetic studies with various peptidyl-MCA indicate that the hexapeptide Ac-KTKQLR-MCA (where MCA stands for 4-methyl coumaryl-7-amide) is most efficiently and selectively cleaved by PC4 at RMCA, making it another effective agent for bioassay of PC4 activity. The study concludes that the most probable sequence motif for recognition by PC4 is KXKXXR or KXXR, where X is any amino acid other than cysteine and that it prefers proline at P3, P5 and/or P2' positions. It was also revealed that PC4 is a good candidate processing enzyme for growth factors IGF-1 and -2, neuropeptide proPACAP and several ADAM proteins such as ADAM-1, -2, -3 and -5.

Testicular phenotype in luteinizing hormone receptor knockout animals and the effect of testosterone replacement therapy

The LH receptor knockout model, developed in our laboratory, was used in determining what FSH alone can do in the absence of LH signaling and whether any of the testicular LH actions are not mediated by androgens. The results revealed that null animals contained smaller seminiferous tubules, which contained the same number of Sertoli cells, spermatogonia, and early spermatocytes as wild-type siblings. The number of late spermatocytes, on the other hand, was moderately decreased, the number of round spermatids was dramatically decreased, and elongated spermatids were completely absent. These changes appear to be due to an increase in apoptosis in spermatocytes. While the number of Leydig cells progressively increased from birth to 60 days of age in wild-type animals, they remained unchanged in null animals. Consequently, 60-day-old null animals contained only a few Leydig cells of fetal type. The age-dependent increase in testicular macrophages lagged behind in null animals compared with wild-type siblings. Orchidopexy indicated that -/- testicular phenotype was not due to abdominal location. Rather, it was mostly due to androgen deficiency, as 21-day testosterone replacement therapy stimulated the growth of seminiferous tubules, decreased apoptosis, and increased the number of late spermatocytes and round spermatids and their subsequent differentiation into mature sperm. The therapy, however, failed to restore adult-type Leydig cells and testicular macrophage numbers to the wild-type levels. In summary, our data support the concept that FSH signaling alone can maintain the proliferation and development of Sertoli cells, spermatogonia, and early spermatocytes. LH actions mediated by testosterone are required for completion of spermatogenesis, and finally, androgen-independent actions of LH are required for the formation of adult-type Leydig cells and recruitment of macrophages into the testes.

Structural and functional modifications of sertoli cells in the testis of adult follicle-stimulating hormone receptor knockout mice

Follicle stimulating hormone (FSH) plays important roles during testicular development and in the maintenance of spermatogenesis in the adult. However, the cellular events or pathways that FSH regulates to achieve these effects in Sertoli cells, where the FSH receptors (FSH-R) are located, is still not fully elucidated. The development of FSH-R knockout (FORKO) mice provides a model to examine alterations in testicular structure and function in its absence. To this end, light (LM) and electron microscopic (EM) analyses of perfusion-fixed testes of wild-type and FORKO mice of different ages were performed. Under the LM, a significant reduction was noted in the profile area of seminiferous tubules of FORKO mice compared with their wild-type counterparts at different ages. In addition, FORKO testes revealed large irregularly shaped spaces within the seminiferous epithelium, extending from the base to the lumen. Such spaces were often separated by anastomotic cords of spherical germ cells or completely surrounded elongating spermatids. This phenotype was restricted to half or less of the circumference of only some tubules, but was seen at all stages. EM analyses revealed that the spaces corresponded to an apparent accumulation of fluid in the Sertoli cell cytoplasm, coincident with an absence of the fine flocculent ground substance seen in wild-type mice. However, the Sertoli organelles, while less prominent, appeared intact and to be floating in the enlarged fluid-filled cytoplasm. Functionally, androgen-binding protein (ABP), a major secretory protein of Sertoli cells, was dramatically reduced in FORKO mice. These results suggest that FSH-R signaling normally maintains water balance in Sertoli cells in addition to regulating ABP production.