Regulation of germ cell death in mammalian gonads

Impacts of Acrylamide on testis and spermatozoa

Acrylamide (ACR) is an industrial chemical used to produce polyacrylamide, a synthetic polymer with a wide range of applications. Depending on the dosage, its presence in occupational and environmental sources poses potential health risks to humans and animals. ACR can be formed in starchy foods cooked at high temperatures. Its effects on human sperm are not well understood. Animal studies indicate that ACR induces toxicity in the male reproductive system through oxidative stress mechanisms. Exposure to ACR alters the normal structure of testicular tubules, leading to congestion, interstitial edema, degeneration of spermatogenic cells, formation of abnormal spermatid giant cells, and necrosis and apoptosis. It also disrupts the balance of important biomarkers such as malondialdehyde, nitric oxide, superoxide dismutase, catalase, and glutathione. ACR has a negative impact on mitochondrial function, antioxidant enzymes, ATP production, and sperm membrane integrity, resulting in decreased sperm quality. Furthermore, it interferes with the expression of steroidogenic genes associated with testosterone biosynthesis. This review explores the detrimental effects of ACR on sperm and testicular function and discusses the potential role of antioxidants in mitigating the adverse effects of ACR on male reproduction.

Stage-Dependent Expression of Protein Gene Product 9.5 in Donkey Testes

Simple Summary

Spermatogenesis and steroidogenesis are key functions of the testes. Molecular markers that identify each stage of germ cells and Leydig cells can identify and isolate specific germ or Leydig cells. Protein gene product (PGP)9.5 is observed in neuroendocrine cells and tumors; it is also used for the immunohistochemical detection of spermatogonial stem cells (SSCs) in various species of animals. It was found that the immunolabeling of PGP9.5 in testicular tissue was not observed in the seminiferous tubules in the pre-pubertal stage. However, in the post-pubertal stage, spermatogonia were immunolabeled with PGP9.5. Interestingly, some Leydig cells were immunolabeled with PGP9.5 in both pre- and post-pubertal stages. This study reflects that the PGP9.5 antibody can be used as a tool to identify and isolate spermatogonia from seminiferous tubules in the post-pubertal stage of donkey testes.

Abstract

Molecular markers can be used to identify and isolate specific developmental stages of germ cells and Leydig cells. Protein gene product (PGP)9.5 expression in spermatogonia and Leydig cells has been reported in several species. The stages of spermatogonia and Leydig cells expressing PGP9.5 vary depending on the species and reproductive stages. Thus, the objectives of this study were (1) to identify the localization of PGP9.5 in donkey testicular cells, and (2) to compare the expression patterns of PGP9.5 in donkey testicular cells between pre- and post-pubertal stages. Testes samples were collected following the routine field castration of six donkeys. Western blotting was performed to verify the cross-reactivity of the rabbit anti-human PGP9.5 antibody to donkey testes. Immunofluorescence was performed to investigate the expression pattern of PGP9.5 in testicular tissues at different reproductive stages. In Western blotting, the protein band of the PGP9.5 antibody appeared at approximately 27 kDa, whereas the band was not observed in the negative control treated with normal mouse IgG. In the pre-pubertal stage, the expression of deleted in azoospermia-like (DAZL) was found in some spermatogonia in pre-pubertal testicular tissues. However, the immunolabeling of PGP9.5 in testicular tissue was not observed in the seminiferous tubules. In stages 1 and 2, spermatogonia were immunolabeled with either PGP9.5 or DAZL. In contrast, PGP9.5 and DAZL were co-immunolabeled in some of the spermatogonia in stages 3 to 8. Interestingly, some Leydig cells were immunolabeled with PGP9.5 in both pre- and post-pubertal stages. In conclusion, the PGP9.5 antibody can be used as a tool to identify and isolate spermatogonia from seminiferous tubules.

Mouse Germ Cell Development in-vivo and in-vitro

In mammalian development, primordial germ cells (PGCs) represent the initial population of cells that are committed to the germ cell lineage. PGCs segregate early in development, triggered by signals from the extra-embryonic ectoderm. They are distinguished from surrounding cells by their unique gene expression patterns. Some of the more common genes used to identify them are Blimp1, Oct3/4, Fragilis, Stella, c-Kit, Mvh, Dazl and Gcna1. These genes are involved in regulating their migration and differentiation, and in maintaining the pluripotency of these cells.

Recent research has demonstrated the possibility of obtaining PGCs, and subsequently, mature germ cells from a starting population of embryonic stem cells (ESCs) in culture. This phenomenon has been investigated using a variety of methods, and ESC lines of both mouse and human origin. Embryonic stem cells can differentiate into germ cells of both the male and female phenotype and in one case has resulted in the birth of live pups from the fertilization of oocytes with ESC derived sperm. This finding leads to the prospect of using ESC derived germ cells as a treatment for sterility. This review outlines the evolvement of germ cells from ESCs in vitro in relation to in vivo events.

No association of TP53 codon 72 SNP with male infertility: a study in a Chinese population and a meta-analysis

Genetic polymorphisms may affect human male fertility. Even though TP53 plays a role in spermatogenesis we know little about the association of the functional polymorphism at codon 72 of TP53 with respect to susceptibility to male infertility. We conducted a case-control study to investigate this association in a Chinese population and performed a meta-analysis in different populations to clarify this association. The single nucleotide polymorphism (SNP) of TP53 codon 72 (rs1042522 G>C) was genotyped by PCR-RFLP in 83 Chinese male infertility patients and 401 healthy controls. Meta-analysis was performed using the data from four currently available studies. The data from our study were overlayed using the v.9.0 STATA software package. We observed no association between the TP53 codon 72 polymorphism and male infertility (p = 0.84, OR = 1.04, 95% CI, 0.74-1.45). Meta-analysis confirmed the case-control result that there was no significant association between the codon 72 polymorphism of TP53 and male infertility (Pro vs. Arg; p = 0.31, OR = 0.86, 95% CI, 0.65-1.15; Pro/Pro vs. Arg-carriers; p = 0.65, OR = 0.91, 95% CI, 0.61-1.36; Pro-carriers vs. Arg/Arg: p = 0.15, OR = 0.75, 95% CI, 0.51-1.11). The data presented in this communication supports the view that the codon 72 polymorphism of TP53 may not contribute to male infertility susceptibility in the Chinese population.

A novel Amh-Treck transgenic mouse line allows toxin-dependent loss of supporting cells in gonads

Cell ablation technology is useful for studying specific cell lineages in a developing organ in vivo. Herein, we established a novel anti-Müllerian hormone (AMH)-toxin receptor-mediated cell knockout (Treck) mouse line, in which the diphtheria toxin (DT) receptor was specifically activated in Sertoli and granulosa cells in postnatal testes and ovaries respectively. In the postnatal testes of Amh-Treck transgenic (Tg) male mice, DT injection induced a specific loss of the Sertoli cells in a dose-dependent manner, as well as the specific degeneration of granulosa cells in the primary and secondary follicles caused by DT injection in Tg females. In the testes with depletion of Sertoli cell, germ cells appeared to survive for only several days after DT treatment and rapidly underwent cell degeneration, which led to the accumulation of a large amount of cell debris within the seminiferous tubules by day 10 after DT treatment. Transplantation of exogenous healthy Sertoli cells following DT treatment rescued the germ cell loss in the transplantation sites of the seminiferous epithelia, leading to a partial recovery of the spermatogenesis. These results provide not only in vivo evidence of the crucial role of Sertoli cells in the maintenance of germ cells, but also show that the Amh-Treck Tg line is a useful in vivo model of the function of the supporting cell lineage in developing mammalian gonads.

Anchoring ethinylestradiol induced gene expression changes with testicular morphology and reproductive function in the medaka

Environmental estrogens are ubiquitous in the environment and can cause detrimental effects on male reproduction. In fish, a multitude of effects from environmental estrogens have been observed including altered courting behavior and fertility, sex reversal, and gonadal histopathology. However, few studies in fish assess the impacts of estrogenic exposure on a physiological endpoint, such as reproduction, as well as the associated morphologic response and underlying global gene expression changes. This study assessed the implications of a 14 day sub-chronic exposure of ethinylestradiol (EE2; 1.0 or 10.0 µg/L EE2) on male medaka fertility, testicular histology and testicular gene expression. The findings demonstrate that a 14 day exposure to EE2 induced impaired male reproductive capacity and time- and dose-dependent alterations in testicular morphology and gene expression. The average fertilization rate/day following the exposure for control, 1.0 and 10.0 µg/L EE2 was 91.3% (±4.4), 62.8% (±8.3) and 28.8% (±5.8), respectively. The testicular morphologic alterations included increased germ cell apoptosis, decreased germinal epithelium and thickening of the interstitium. These changes were highly associated with testicular gene expression changes using a medaka-specific microarray. A pathway analysis of the differentially expressed genes emphasized genes and pathways associated with apoptosis, cell cycle and proliferation, collagen production/extracellular matrix organization, hormone signaling, male reproduction and protein ubiquitination among others. These findings highlight the importance of anchoring global gonadal gene expression changes with morphology and ultimately with tissue/organ function.

Overexpression of human SPATA17 protein induces germ cell apoptosis in transgenic male mice

SPATA17 is a new testis-specific-expressed gene that is involved in Spermatogenesis process. Previous studies show that SPATA17 was involved in acceleration of cell apoptosis in GC-1 cell lines. To further investigate specific roles of SPATA17 in Spermatogenesis in vivo, we generated transgenic mice in which the human SPATA17 gene was expressed specifically in spermatocytes using the human phosphoglycerate kinase 2 (PGK2) promoter. The SPATA17 transgenic mice did not show any significant defect in gross testicular anatomy as well as in fertility. However, a significant increase was observed in defective spermatogenic cells, such as apoptotic cells in the SPATA17 transgenic mice. These results revealed that elevated production of the SPATA17 protein disturbed the normal development of male germ cells.

The apoptotic function analysis of p53, Apaf1, Caspase3 and Caspase7 during the spermatogenesis of the Chinese fire-bellied newt Cynops orientalis

BACKGROUND

Spontaneous and stress-induced germ cell apoptosis during spermatogenesis of multicellular organisms have been investigated broadly in mammals. Spermatogenetic process in urodele amphibians was essentially like that in mammals in spite of morphological differences; however, the mechanism of germ cell apoptosis in urodele amphibians remains unknown. The Chinese fire-belly newt, Cynops orientalis, was an excellent organism for studying germ cell apoptosis due to its sensitiveness to temperature, strong endurance of starvation, and sensitive skin to heavy metal exposure.

METHODOLOGY/PRINCIPAL FINDINGS

TUNEL result showed that spontaneous germ cell apoptosis took place in normal newt, and severe stress-induced apoptosis occurred to spermatids and sperm in response to heat shock (40°C 2 h), cold exposure (4°C 12 h), cadmium exposure (Cd 36 h), and starvation stress. Quantitative reverse transcription polymerase chain reactions (qRT-PCR) showed that gene expression of Caspase3 or Caspase7 was obviously elevated after stress treatment. Apaf1 was not altered at its gene expression level, and p53 was significantly decreased after various stress treatment. Caspase assay demonstrated that Caspase-3, -8, -9 enzyme activities in newt testis were significantly elevated after heat shock (40°C 2 h), cold exposure (4°C 12 h), and cadmium exposure (Cd 36 h), while Caspase3 and Caspase8 activities were increased with Caspase9 significantly decreased after starvation treatment.

CONCLUSIONS/SIGNIFICANCE

Severe germ cell apoptosis triggered by heat shock, cold exposure, and cadmium exposure was Caspase3 dependent, which probably involved both extrinsic and intrinsic pathways. Apaf1 may be involved in this process without elevating its gene expression. But starvation-induced germ cell apoptosis was likely mainly through extrinsic pathway. p53 was probably not responsible for stress-induced germ cell apoptosis in newt testis. The intriguing high occurrence of spermatid and sperm apoptosis probably resulted from the sperm morphology and unique reproduction policy of Chinese fire-belly newt, Cynops orientalis.

Why does cytotoxic chemotherapy cure only some cancers?

Despite frequent responses to chemotherapy, curative treatment remains elusive for the majority of patients with metastatic solid tumors. By contrast, in testicular cancer, gestational choriocarcinoma, Hodgkin disease and high-grade lymphomas, chemotherapy is routinely curative, even for patients who present with widely disseminated disease. In the common advanced cancers, however, over 40 years of cytotoxic drug development has brought no significant change in cure rates. One interpretation is that the intrinsic properties of the malignancies themselves, rather than the qualities of individual drugs or combination therapies, are primarily responsible for their curability with chemotherapy. We suggest that the curability of these malignancies results from an intrinsic 'locked-in' state of sensitivity to proapoptotic stresses in these cells. A common property of such curable malignancies is that they arise from cells that undergo major genetic rearrangements or recombination as part of their normal physiology. The absence of further genetic and epigenetic changes in genes that regulate apoptosis, DNA repair and senescence allows these cells to maintain their intrinsic sensitivity to chemotherapy. This process allows the cells, when challenged with chemotherapy, to undergo the natural apoptotic pathways that contribute to their intrinsic qualities of chemosensitivity and high curability.

The survival of differentiating embryonic stem cells is dependent on the SCF-KIT pathway

The stem cell factor (SCF)-KIT signal transduction pathway plays a role in the proliferation, differentiation and survival of a range of stem and progenitor cell types but little is known about its function in embryonic stem (ES) cells. We generated ES cells carrying a null allele of Kit as well as a knock-in allele that encodes an SCF-independent hybrid KIT receptor that can be activated by the FKBP binding drug, AP20187. KIT null ES cells die when induced to differentiate upon withdrawal of leukaemia inhibitory factor in monolayer culture. This phenotype is recapitulated in wild-type ES cells treated with a KIT-neutralising antibody and reversed in mutant cells by activation of the hybrid KIT receptor. Differentiating KIT null ES cells exhibit elevated levels of DNA laddering and reduced BCL2 expression, indicative of apoptosis. We conclude that mouse ES cell differentiation in vitro is dependent on the SCF-KIT pathway contrasting with the apparently normal differentiation of KIT null inner cell mass or epiblast cells in vivo. This discrepancy could be explained by the presence of compensatory signals in the embryo or it could lend support to the idea of a phenotypic relationship between ES cells and early germ cells.

Octylphenol induces apoptosis in cultured rat Sertoli cells

In this study, the effects of 4-tert-octylphenol (OP) were examined on the viability of rat cultured Sertoli cells using the MTT assay and OP-induced apoptosis was detected by transmission electron microscope (TEM), flow cytometric analysis and Hoechst staining. In addition, RT-PCR was used to analyze the levels of Bcl-2 and Bax mRNA. Bcl-2, Bax and caspase-3 protein expressions were determined by Western blot analysis. Sertoli cells were treated with OP from 30 to 60microM for 6-24h. Decreased viability of Sertoli cells and increased apoptosis occurred in a concentration- and a time-dependent manner. The expression of Bcl-2 was down-regulated, while the expression of Bax up-regulated. OP also down-regulated the expression of 32kDa procaspase-3, which was cleaved to generate active subunit (17kDa). These results suggest that OP may induce Sertoli cell apoptosis by regulation of Bcl-2/Bax and caspase-3 activation.

Impaired germ cell development due to compromised cell cycle progression in Skp2-deficient mice

BACKGROUND

The gonads are responsible for the production of germ cells through both mitosis and meiosis. Skp2 is the receptor subunit of an SCF-type ubiquitin ligase and is a major regulator of the progression of cells into S phase of the cell cycle, which it promotes by mediating the ubiquitin-dependent degradation of p27, an inhibitor of cell proliferation. However, the role of the Skp2-p27 pathway in germ cell development remains elusive.

RESULTS

We now show that disruption of Skp2 in mice results in a marked impairment in the fertility of males, with the phenotypes resembling Sertoli cell-only syndrome in men. Testes of Skp2-/- mice manifested pronounced germ cell hypoplasia accompanied by massive apoptosis in spermatogenic cells. Flow cytometry revealed an increased prevalence of polyploidy in spermatozoa, suggesting that the aneuploidy of these cells is responsible for the induction of apoptosis. Disruption of the p27 gene of Skp2-/- mice restored germ cell development, indicating that the testicular hypoplasia of Skp2-/- animals is attributable to the antiproliferative effect of p27 accumulation.

CONCLUSION

Our results thus suggest that compromised cell cycle progression caused by the accumulation of p27 results in aneuploidy and the induction of apoptosis in gonadal cells of Skp2-/- mice. The consequent reduction in the number of mature gametes accounts for the decreased fertility of these animals. These findings reinforce the importance of the Skp2-p27 pathway in cell cycle regulation and in germ cell development.

Loss of the tumor suppressor gene PTEN marks the transition from intratubular germ cell neoplasias (ITGCN) to invasive germ cell tumors

PTEN/MMAC1/TEP1: (hereafter PTEN) is a tumor suppressor gene (located at 10q23) that is frequently mutated or deleted in sporadic human tumors. PTEN encodes a multifunctional phosphatase, which negatively regulates cell growth, migration and survival via the phosphatidylinositol 3'-kinase/AKT signalling pathway. Accordingly, Pten+/- mice develop various types of tumors including teratocarcinomas and teratomas. We have investigated PTEN expression in 60 bioptic specimens of germ cell tumors (32 seminomas, 22 embryonal carcinomas and six teratomas) and 22 intratubular germ cell neoplasias (ITGCN) adjacent to the tumors for PTEN protein and mRNA expression. In total, 10 testicular biopsies were used as controls. In the testis, PTEN was abundantly expressed in germ cells whereas it was virtually absent from 56% of seminomas as well as from 86% of embryonal carcinomas and virtually all teratomas. On the contrary, ITGCN intensely expressed PTEN, indicating that loss of PTEN expression is not an early event in testicular tumor development. The loss of PTEN expression occurs mainly at the RNA level as determined by in situ hybridization of cellular mRNA (17/22) but also it may involve some kind of post-transcriptional mechanisms in the remaining 25% of cases. Analysis of microsatellites D10S551, D10S541 and D10S1765 in GCTs (n=22) showed LOH at the PTEN locus at 10q23 in at least 36% of GCTs (three embryonal carcinoma, three seminoma, two teratoma); one seminoma and one embryonal (9%) carcinoma presented an inactivating mutation in the PTEN gene (2/22). Finally, we demonstrated that the phosphatidylinositol 3'-kinase/AKT pathway, which is regulated by the PTEN phosphatase, is crucial in regulating the proliferation of the NT2/D1 embryonal carcinoma cells, and that the cyclin-dependent kinase inhibitor p27(kip1) is a key downstream target of this pathway.

Ubiquitin C-terminal hydrolase L-1 is essential for the early apoptotic wave of germinal cells and for sperm quality control during spermatogenesis

Ubiquitination is required throughout all developmental stages of mammalian spermatogenesis. Ubiquitin C-terminal hydrolase (UCH) L1 is thought to associate with monoubiquitin to control ubiquitin levels. Previously, we found that UCHL1-deficient testes of gad mice have reduced ubiquitin levels and are resistant to cryptorchid stress-related injury. Here, we analyzed the function of UCHL1 during the first round of spermatogenesis and during sperm maturation, both of which are known to require ubiquitin-mediated proteolysis. Testicular germ cells in the immature testes of gad mice were resistant to the early apoptotic wave that occurs during the first round of spermatogenesis. TUNEL staining and cell quantitation demonstrated decreased germ cell apoptosis and increased numbers of premeiotic germ cells in gad mice between Postnatal Days 7 and 14. Expression of the apoptotic proteins TRP53, Bax, and caspase-3 was also significantly lower in the immature testes of gad mice. In adult gad mice, cauda epididymidis weight, sperm number in the epididymis, and sperm motility were reduced. Moreover, the number of defective spermatozoa was significantly increased; however, complete infertility was not detected. These data indicate that UCHL1 is required for normal spermatogenesis and sperm quality control and demonstrate the importance of UCHL1-dependent apoptosis in spermatogonial cell and sperm maturation.

THE MOLECULAR PATHOLOGY OF EXPERIMENTAL TESTICULAR TORSION SUGGESTS ADJUNCT THERAPY TO SURGICAL REPAIR

PURPOSE

We review the work of our laboratory in discovering the pathophysiological mechanisms that underpin testicular response to testicular torsion. Evidence from animal models is used to discover pathways that might be amenable to manipulation by therapeutic regimens.

MATERIALS AND METHODS

Rats and mice were subjected to 1 and 2 hours of testicular torsion, respectively. Preliminary experiments determined that those are the times of torsion in those species that produce severe testicular atrophy and germ cell apoptosis. A variety of biochemical and molecular biological techniques were used to determine the mechanism(s) leading to spermatogenic disruption and germ cell apoptosis.

RESULTS

Testicular torsion can eliminate spermatogenesis despite return blood flow, continued Sertoli cell function and perhaps the continued production of testosterone by Leydig cells, although the latter point is not completely resolved. Torsion repair is followed by a period of germ cell apoptosis, accumulation of testicular neutrophils and increased testicular oxidative stress. Testicular vascular E-selectin expression is increased after torsion repair as are a number of cytokines important to the recruitment of neutrophils. Elements of the c-Jun-N-terminal kinase pathway are important in this process. The presence of neutrophils leads to intratesticular oxidative stress, and oxidative stress has been significantly reduced by intravenous infusion of oxygen radical scavengers at the time of torsion repair.

CONCLUSIONS

Testicular torsion causes loss of spermatogenesis and a significant increase in germ cell apoptosis due to an increase in testicular oxidative stress concomitant with reperfusion. Oxidative stress arises with recruitment of neutrophils, and the recruitment of neutrophils occurs due to E-selectin expression on the surface of the testicular venules after torsion repair. The cytokines, tumor necrosis factor-alpha and interleukin-1beta, activate the stress related kinase pathway to E-selectin expression after torsion repair. Oxidative stress is relieved by infusion of oxygen radical scavengers, which results in a significant salvage of testicular function.

Two closely related ubiquitin C-terminal hydrolase isozymes function as reciprocal modulators of germ cell apoptosis in cryptorchid testis

The experimentally induced cryptorchid mouse model is useful for elucidating the in vivo molecular mechanism of germ cell apoptosis. Apoptosis, in general, is thought to be partly regulated by the ubiquitin-proteasome system. Here, we analyzed the function of two closely related members of the ubiquitin C-terminal hydrolase (UCH) family in testicular germ cell apoptosis experimentally induced by cryptorchidism. The two enzymes, UCH-L1 and UCH-L3, deubiquitinate ubiquitin-protein conjugates and control the cellular balance of ubiquitin. The testes of gracile axonal dystrophy (gad) mice, which lack UCH-L1, were resistant to cryptorchid stress-related injury and had reduced ubiquitin levels. The level of both anti-apoptotic (Bcl-2 family and XIAP) and prosurvival (pCREB and BDNF) proteins was significantly higher in gad mice after cryptorchid stress. In contrast, Uchl3 knockout mice showed profound testicular atrophy and apoptotic germ cell loss after cryptorchid injury. Ubiquitin level was not significantly different between wild-type and Uchl3 knockout mice, whereas the levels of Nedd8 and the apoptotic proteins p53, Bax, and caspase3 were elevated in Uchl3 knockout mice. These results demonstrate that UCH-L1 and UCH-L3 function differentially to regulate the cellular levels of anti-apoptotic, prosurvival, and apoptotic proteins during testicular germ cell apoptosis.

HST-1/FGF-4 protects male germ cells from apoptosis under heat-stress condition

Apoptosis plays an important role in controlling the number of male germ cells and eliminating defective germ cells during testicular development and spermatogenesis. We show here that fibroblast growth factor-4 (HST-1/FGF-4) may play a critical role as a survival factor for germ cells, protecting them from apoptosis. Testes of adult male mice that received an adenovirus carrying human HST-1/FGF-4 (AxHST-1) or a control adenovirus (AxCAwt) were exposed to mild hyperthermia, which causes germ cell apoptosis. An in situ terminal-deoxynucleotidyl transferase-mediated deoxy-UTP nick end-labeling (TUNEL) assay characterized germ cell apoptosis. The results indicated that HST-1/FGF-4 significantly reduced the apoptotic death of germ cells and prevented testicular weight loss and sperm count reduction. We also found that Hst-1/Fgf-4 present in testes is up-regulated in vivo when the testes are exposed to mild hyperthermia, and that endogenous Hst-1/Fgf-4 mRNA expression in Sertoli cells are also induced when the cells are exposed to mild hyperthermia in vitro. In addition, the MAPK cascade, which could increase an FGF-dependent survival signal, is activated by HST-1/FGF-4 stimuli in germ cells. On the other hand, upon HST-1/FGF-4 stimulation, lactate production from Sertoli cells were induced, which is indispensable nutrient for germ cell survival. These results suggest that HST-1/FGF-4 can act as an important physiological anti-apoptotic factor for male germ cells in stimulating lactate production of Sertoli cells upon heat stress, thereby promoting germ cell survival.

Functional analysis of the p53 gene in apoptosis induced by heat stress or loss of stem cell factor signaling in mouse male germ cells

Apoptosis plays an important role in controlling germ cell numbers and restricting abnormal cell proliferation during spermatogenesis. The tumor suppressor protein, p53, is highly expressed in the testis, and is known to be involved in apoptosis, which suggests that it is one of the major causes of germ cell loss in the testis. Mice that are c-kit/SCF mutant (Sl/Sld) and cryptorchid show similar testicular phenotypes; they carry undifferentiated spermatogonia and Sertoli cells in their seminiferous tubules. To investigate the role of p53-dependent apoptosis in infertile testes, we transplanted p53-deficient spermatogonia that were labeled with enhanced green fluorescence protein into cryptorchid and Sl/Sld testes. In cryptorchid testes, transplanted p53-deficient spermatogonia differentiated into spermatocytes, but not into haploid spermatids. In contrast, no differentiated germ cells were observed in Sl/Sld mutant testes. These results indicate that the mechanism of germ cell loss in the c-kit/SCF mutant is not dependent on p53, whereas the apoptotic mechanism in the cryptorchid testis is quite different (i.e., although the early stage of differentiation of spermatogonia and the meiotic prophase is dependent on p53-mediated apoptosis, the later stage of spermatids is not).

Effects of VEGF and bFGF on proliferation and production of steroids and nitric oxide in porcine granulosa cells

Ovarian angiogenesis, which is currently considered to be of crucial importance in controlling the growth of developing follicles, is a physiological process driven by a variety of angiogenic factors. Among these, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have been recognized as key players in promoting cell growth and differentiation. Porcine granulosa cells from small (<3 mm), medium (3-5 mm) and large (>5 mm) follicles were seeded at different densities in DMEM:Ham's F12 (1:1) with or without different concentrations of VEGF or bFGF. After 48 h of culture, media were assayed for oestradiol (E2) 17beta, progesterone (P4), nitric oxide (NO) and VEGF levels; in addition, cell proliferation was evaluated by 3H-thymidine incorporation assay. Both bFGF and VEGF effects on E2 and P4 production by cultured granulosa cells resulted to be dependent on follicle size. The bFGF was always ineffective in modulating cell proliferation, while VEGF exerted an inhibitory effect on the proliferation in the small follicle group and a stimulatory one in the medium and large follicle groups. The bFGF consistently reduced NO levels in culture media. The VEGF appeared to be ineffective in modifying NO production in the small follicle group, while it was stimulatory in the medium follicle group and inhibitory in the large follicle group. Basal VEGF production was higher in cells from the large follicle as compared with the small and medium follicle groups, and it was unaffected by bFGF. These results suggest that VEGF plays a modulatory role in granulosa cell functional activity and it is possibly involved in the regulation of follicle growth; on the contrary, bFGF does not appear to represent a significant regulatory factor in our cellular model, except for an inhibitory action on the production of NO, whose anti-angiogenic properties need to be further substantiated.

Genetics and biology of male germ cell tumors

The application of cytogenetic and molecular genetic techniques to the study of germ cell tumors has yielded many clues to the etiology and chemosensitivity of these tumors. With the advent of expression profiling and genome-scanning technologies, it may be possible to identify molecular markers of germ cell tumor outcome and molecular networks important in human development and chemotherapeutic response.

Role of Sertoli cells in injury-associated testicular germ cell apoptosis

This review examines experimental models of Sertoli cell injury resulting in germ cell apoptosis. Since germ cells exist in an environment created by Sertoli cells, paracrine signaling between these intimately associated cells must regulate the process of germ cell death. Germ cell apoptosis may be signaled by a decrease in Sertoli cell pro-survival factors, an increase in Sertoli cell pro-apoptotic factors, or both. The different models of Sertoli cell injury indicate that spermatogenesis is susceptible to disruption, and that targeting critical Sertoli cell functions can lead to rapid and massive germ cell death.

Isolation and expression of PASK, a serine/threonine kinase, during rat embryonic development, with special emphasis on the pancreas

We report the isolation and characterization of a serine/threonine kinase expressed during rat pancreas development. This kinase was cloned as part of a general screen using degenerate oligonucleotides to map expression of kinases and receptors during the course of pancreatic development. Sequence analysis showed it to be a member of the ste20-like serine/threonine kinase family. Northern blotting analysis against both fetal and adult tissues showed two transcripts, one of 2 kb and the other of 4 kb. The ratio of transcript expression varied with the tissue. In situ hybridization analysis showed that this gene is expressed in the early gut and pancreatic epithelium. By embryonic Day 15, the transcript is localized to cells that will eventually become exocrine in nature. In situ hybridization analysis also demonstrated high levels of expression in the choroid plexus, the developing myocardium, kidney, CNS, dorsal root ganglia, and testes. In addition, a search of the EST database revealed a related human kinase not previously described.

Expression of Indian hedgehog, parathyroid hormone-related protein, and their receptors in the postnatal growth plate of the rat: evidence for a locally acting growth restraining feedback loop after birth

A locally acting growth restraining feedback loop has been identified in the murine embryonic growth plate in which the level of parathyroid hormone-related peptide (PTHrP) expression regulates the pace of chondrocyte differentiation. To date, it is largely unknown whether this feedback loop also regulates the pace of chondrocyte differentiation in the growth plate after birth. We therefore characterized the spatio-temporal expression of Indian hedgehog (IHH), PTHrP, and their receptors in the postnatal growth plate from female and male rats of 1, 4, 7, and 12 weeks of age. These stages are representative for early life and puberty in rats. Using semiquantitative reverse-transcription polymerase chain reaction (RT-PCR) on growth plate tissue, IHH and components of its receptor complex, patched (PTC) and smoothened (SMO), PTHrP and the type I PTH/PTHrP receptor messenger RNA (mRNA) were shown at all ages studied irrespective of gender. Using in situ hybridization, IHH, PTHrP, and PTH/PTHrP receptor mRNA were detected in prehypertrophic and hypertrophic chondrocytes in both sexes during development. In addition, especially in the younger age groups, faint expression of PTH/PTHrP receptor mRNA also was shown in stem cells and proliferative chondrocytes. Immunohistochemistry confirmed the observations made with in situ hybridization, by showing the presence of IHH, PTC, PTHrP, and PTH/PTHrP receptor protein in prehypertrophic and hypertrophic chondrocytes. In addition, staining for hedgehog, PTC, and PTHrP also was observed in growth plate stem cells. No differences in staining patterns were observed between the sexes. Furthermore, no mRNA or protein expression of the mentioned factors was detected in the perichondrium. Our data suggest that in contrast to the proposed feedback loop in the early embryonic growth plate, which requires the presence of the perichondrium, a feedback loop in the postnatal growth plate can be confined to the growth plate itself. In fact, two loops might exist: (1) a loop confined to the transition zone and early hypertrophic chondrocytes, which might in part be autocrine and (2) a loop involving the growth plate stem cells.

Stem cell factor protects germ cells from apoptosis in vitro

Stem cell factor (SCF) plays an important role in migration, adhesion, proliferation, and survival of primordial germ cells and spermatogonia during testicular development. However, the function of SCF in the adult testis is poorly described. We have previously shown that, in the presence of SCF, there were more type A spermatogonia incorporating thymidine at stage XII of rat seminiferous tubules cultured in vitro than in the absence of SCF, implying that the increased DNA synthesis might result from enhanced survival of spermatogonia. To explore the potential pro-survival function of SCF during spermatogenesis, the seminiferous tubules from stage XII were cultured in the presence or absence of SCF (100 ng/ml) for 8, 24, 48, and 72 hours, respectively, and apoptosis was analyzed by DNA laddering and in situ 3′-end labeling (ISEL) staining. Surprisingly, not only spermatogonia, but also spermatocytes and spermatids, were protected from apoptosis in the presence of SCF. Apoptosis took place much later and was less severe in the SCF-treated tubules than in the controls. Based on previous studies showing that FSH prevents germ cells from undergoing apoptosis in vitro, and that SCF level is increased dramatically in response to FSH stimulation, we also tested if the pro-survival effect of FSH is mediated through SCF by using a function-blocking monoclonal antibody, ACK-2, to block SCF/c-kit interaction. After 24 hours of blockade, the protective effect of FSH was partially abolished, as manifested by DNA laddering and ISEL analyses. The present study demonstrates that SCF acts as an important survival factor for germ cells in the adult rat testis and FSH pro-survival effect on germ cells is mediated partially through the SCF/c-kit pathway.

Influence of environmental cadmium on testicular proliferation in roe deer

The influence of cadmium on spermatogenesis in roe deer was studied, comparing animals from areas with high (n = 37) and low (n = 23) cadmium exposure. Testes were evaluated during pre-rut (May) and rut (July/August). During these periods the cadmium accumulation (mg/kg kidney) in polluted regions averaged 3.41 and 3.52 in comparison with 1.61 and 1.81 in controls. Cadmium accumulation was positively correlated with testis weight during both seasons. In May the proliferation (units of tissue polypeptid specific antigen/g parenchyma) was lower in animals with higher cadmium (24.02 compared with 78.20; P < 0.01). During the rut, testicular proliferation and spermatozoa/g testis as well as apoptosis showed no significant changes with increased cadmium contamination. The results suggest delayed proliferation during the pre-rutting period in animals with high cadmium exposure, but other indications of effects on the testis were not significant.

The origin and biology of CIS cells: general discussion

Participants at the 4th Copenhagen Workshop on Carcinoma in situ and Cancer of the Testis, representing cell biologists and tumour biologists, met together to discuss the similarities and differences between primordial germ cells (PGCs) of the embryo, and the carcinoma in situ (CIS) stem cell of human testicular germ cell tumours (GCTs). Much has been discovered about PGCs in the last 10 years and we still do not know the exact nature of CIS cells. Knowledge of PGCs comes mainly from mouse experiments and knowledge of CIS comes from the study of human tumours. A mouse model of human GCT would help to investigate the nature of CIS cells. Grafting mouse male genital ridges into mouse fetal testes results in the development of testicular tissue and the formation of teratomatous tumour components. Amplification of PGCs in culture is possible but this results in their transformation into embryonic germ (EG) cells. CIS cells die by apoptosis if they are isolated, and short-term culture is only possible if the CIS cells are cultured in their normal environment within seminiferous tubules. It may be possible for CIS cells to differentiate in culture although they cannot be maintained in culture as isolated cells. Human CIS cells are likely to be formed as a result of in utero factors rather than agents acting on normal adult testicular germ cells. EG cells stimulate feeder cells by paracrine factors but it is not known if these cells produce autocrine factors.