Rat Germ Cells Research Articles

Germ cell DNA quantification shortly after IR laser radiation

The immediate effect of IR laser radiation on rat germ cells was studied by cytophotometric quantification of the nuclear DNA content in testicular sections. Two different levels of radiation were studied: one according to clinical application (28.05 J/cm2) and another known to increase the germ cell number (46.80 J/cm2). The laser beam induced changes in the germ cell DNA content depending on the cell type, the cell cycle phase and the doses of radiation energy applied. Following irradiation at both doses the percentage of spermatogonia showing a 4c DNA content was increased, while the percentage of these with a 2c DNA content was decreased. Likewise, the percentages of primary spermatocytes with a DNA content equal to 4c (at 28.05 J/cm2), between 2c and 4c (at 46.80 J/cm2) and higher than 4c (at both doses) were increased. No change in the mean spermatid DNA content was observed. Nevertheless, at 46.80 J/cm2 the percentages of elongated spermatids with a c or 2c DNA content differed from the controls. Data show that, even at laser radiation doses used in therapy, the germ cell DNA content is increased shortly after IR laser radiation.

Role of FSH in regulating testicular germ cell transformations in the rat: a study using DNA flow cytometry.

The role of FSH in regulating testicular germ cell transformations during initiation and maintenance of spermatogenesis in the pubertal and adult rat has been studied using DNA flow cytometry (FCM). The cell types were quantified on the basis of their DNA content using DNA specific fluorochrome DAPI (4,6-diamidino phenylindole). Pubertal (30-d old) and adult (100-d old) rats were deprived of endogenous FSH support for 10 d by daily injection (200 microliters d-1) of a characterized FSH antiserum; the control group received an equivalent volume of normal rat serum. FSH deprivation did not lead to any change in serum testosterone levels. The relative proportion of testicular germ cells in the FSH deprived pubertal rat showed a 90% reduction in 1C (round spermatids) and 260% and 90% increase in 2C (spermatogonia) and 4C (spermatocytes) cells respectively. While the overall conversion of 2C to 1C (1C:2C ratio) was reduced by 98%, the transformation of 2C to 4C (4C:2C ratio) and 4C to 1C (meiotic division 1C:4C ratio) was inhibited by 43% and 93% respectively. In the FSH-deprived adult rat the overall conversion of 2C to 1C was reduced by 26% (P < 0.05) only. The 2C and 4C population of cells increased by 47% and 97% respectively (P < 0.025) and the 4C:2C ratio by 47% (P < 0.05). While the meiotic division (1C:4C ratio) was reduced by 54% (P < 0.001), the post-meiotic differentiation of round spermatids to elongate-spermatids (HC:1C) was inhibited by 68% (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of Glial Cell Line-Derived Neurotrophic Factor-Regulated Genes Important for Spermatogonial Stem Cell Self-Renewal in the Rat1

Spermatogonial stem cells (SSCs) provide the foundation for spermatogenesis throughout the life of a male. Because SSCs of many species can colonize the mouse testis, and glial cell line-derived neurotrophic factor (GDNF) is responsible for stimulating SSC self-renewal in rodents, we reasoned that molecular mechanisms of SSC self-renewal are similar across species. GDNF-regulated genes have been identified in mouse SSCs; however, downstream targets of GDNF are unknown in other species. The objective of this work was to identify GDNF-regulated genes in rat SSCs and to define the biological significance of these genes for rat SSC self-renewal. We conducted microarray analysis on cultured rat germ cells enriched for SSCs in the presence and absence of GDNF. Many GDNF-regulated genes were identified, most notably, Bcl6b and Etv5, which are important for mouse SSC self-renewal. Bcl6b was the most highly regulated gene in both the rat and mouse. Additionally, we identified three novel GDNF-regulated genes in rat SSCs: Bhlhe40, Hoxc4, and Tec. Small interfering RNA treatment for Bcl6b, Etv5, Bhlhe40, Hoxc4, and Tec resulted in a decrease in SSC number, as determined by transplantation, without a change in total cell number within the culture. These data indicate that, like in the mouse SSC, Bcl6b and Etv5 are important for rat SSC self-renewal, suggesting that these genes may be important for SSCs in all mammals. Furthermore, identification of three novel GDNF-regulated genes in the rat SSC extends our knowledge of SSC activity and broadens the foundation for understanding this process in higher species, including humans.

Involvement of Fas/FasL system in apoptotic signaling in testicular germ cells of male Wistar rats injected i.v. with microcystins

Previous studies have shown that gonads were the second target organ of microcystins (MCs), and that MCs exposure exerted obvious toxic effects on male reproductive system of mammals. However, relevant molecular evidences are still lacking. Fas-signaling pathway plays a key role in toxicant-induced germ cell apoptosis. This study was to evaluate the responses of Fas/FasL system related genes and proteins in testes of rats injected intravenously with MCs. Enhanced apoptosis of germ cells in the testes of MCs-treated rats was detected by the terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labeling (TUNEL) associated with up-regulation of the Fas/FasL system. Both Fas and FasL protein expression were induced evidently from 1 h post-injection, and this high expression level maintained throughout the experiment. In addition, the activation of caspase-8 and caspase-3 protein was also observed, which were indicators of apoptosis. These results suggested the likely involvement of Fas/FasL system in the MCs-induced germ cell apoptosis. It is also suggested that MCs can cause damage to Sertoli cells directly.

Changes in distribution of basic nuclear proteins and chromatin organization during spermiogenesis in the greater bandicoot rat, Bandicota indica

Male germ cells of the greater bandicoot rat, Bandicota indica, have recently been categorized into 12 spermiogenic steps based upon the morphological appearance of the acrosome and nucleus and the cell shape. In the present study, we have found that, in the Golgi and cap phases, round spermatid nuclei contain 10-nm to 30-nm chromatin fibers, and that the acrosomal granule forms a huge cap over the anterior pole of nucleus. In the acrosomal phase, many chromatin fibers are approximately 50 nm thick; these then thickened to 70-nm fibers and eventually became 90-nm chromatin cords that are tightly packed together into highly condensed chromatin, except where nuclear vacuoles occur. Immunocytochemistry and immunogold localization with anti-histones, anti-transition protein2, and anti-protamine antibodies suggest that histones remain throughout spermiogenesis, that transition proteins are present from step 7 spermatids and remain until the end of spermiogenesis, and that protamines appear at step 8. Spermatozoa from the cauda epididymidis have been analyzed by acid urea Triton X-100 polyacrylamide gel electrophoresis for basic nuclear proteins. The histones, H2A, H3, H2B, and H4, transitional protein2, and protamine are all present in sperm extracts. These findings suggest that, in these sperm of unusual morphology, both transition proteins and some histones are retained, a finding possibly related to the unusual nuclear form of sperm in this species.

Evaluation of Effects of Methamphetamine Repeated Dosing on Proliferation and Apoptosis of Rat Germ Cells

Methamphetamine (MAMP) is a central nervous system stimulant that is increasingly abused especially by teenagers and young adults, a group in its reproductive age. MAMP effects on the male reproductive system are not clear. In this experimental study, we evaluated the effects of MAMP administration on proliferation and apoptosis in seminiferous tubules of rat testis. Methamphetamine hydrochloride was synthesized by iodination of norephedrine hydrochloride and reduction to methamphetamine. Mature male rats were randomly divided into four groups (n=7) and were injected intraperitoneally with MAMP (1, 5 or 10 mg/kg) or saline at the same time, once daily for 14 consecutive days. Twenty four hs after the last injection, perfused testis were fixed, sectioned and stained by TUNEL labeling or proliferating cell nuclear antigen (PCNA) immunostaining. Apoptotis and proliferation indices were calculated and ratios of proliferation/apoptosis in the seminiferous tubules were obtained. Cell proliferation and the ratio of proliferation to apoptosis decreased significantly in all experimental groups compared to the control group. Conversely, apoptosis was increased in these groups. Such differences were observed in both spermatogonia and primary spermatocytes. In the control group, more than 95% of spermatogonia were PCNA-positive. However, 10 mg/kg of MAMP caused a reduction to approximately 75% PCNA staining in spermatogonia. In some tubules of the experimental groups, more than 10 TUNEL-positive germ cells were seen, although in the control group, the tubules with 3 TUNEL-positive germ cells were rarely observed and the majority of tubules were without such cells. There were significant differences in the indices between the 1 mg/kg group and the higher dose groups, but there was no such difference between the 5 mg/kg and 10 mg/kg groups. In some tubules of the experimental groups, significant gaps in the epithelium between the spermatogonia layer and other cell layers were observed. These results show that repeated administration of MAMP, especially at higher doses, may cause a decrease in cellular proliferation, induce apoptosis and change the proliferation/apoptosis ratio in testis. This might explain the MAMP effect on the spermatogenesis process. It is suggested that studies on the consequence of MAMP consumption on male fertility is warranted.

Three promoters PII, PI.f, and PI.tr direct the expression of aromatase (cyp19) gene in male rat germ cells

Aromatase is the key enzyme responsible for the irreversible transformation of androgens into estrogens. It is encoded by the cyp19 gene and is expressed in the mammalian testis under the control of the proximal promoter PII. Since both somatic and germ cells contain a biologically active aromatase, we looked for the existence of other promoters that may direct the expression of aromatase in adult rat germ cells. Besides the promoter II, we have shown the presence of transcripts derived from the brain promoter PI.f in spermatogonia-preleptotene spermatocytes (G-PL), pachytene spermatocytes (PS), and round spermatids (RS). A new aromatase cDNA has been isolated by 5'-rapid amplification of cDNA ends that we named I.tr (testis rat). The I.tr transcripts are found in all the testicular cell populations studied with a greater expression in PS. Because of the utilization of these three promoters in the adult rat testis, we studied their putative involvement according to the age. At 10 days, aromatase expression was very low and then strongly increased between 10 and 20 days, with a preferential activation of PII and PI.tr. Transcripts coming from PI.f were found starting from 20 days onwards. The new promoter PI.tr, localized between promoters PI.f and PII, is devoid of a TATA box but contains a transcriptional initiator (Inr) and putative regulatory sequences. Therefore, the identification of the specific trans-activating factors should bring some enlightenments to understand the regulation of these three promoters in germ cells especially according to their stage of development.

Acute Adverse Effects of the Indenopyridine CDB‐4022 on the Ultrastructure of Sertoli Cells, Spermatocytes, and Spermatids in Rat Testes: Comparison to the Known Sertoli Cell Toxicant Di‐n‐pentylphthalate (DPP)

Acute effects of CDB-4022 on testicular ultrastructure were determined. Rats were treated orally with vehicle or a maximally effective single dose of CDB-4022 or Di-n-pentylphthalate (DPP). Preserved testes were processed for transmission electron microscopy. Sertoli and germ cells of vehicle-treated rats demonstrated normal morphological characteristics. Disruption of Sertoli cell ultrastructure was apparent in CDB-4022-treated rats by 3 hours. A decrease in the presence of nucleoli, an increase in the amount and diameter of swollen smooth endoplasmic reticulum, and decreases in cytoplasmic ground substance were observed. The severity of these degenerative effects increased at 6 and 12 hours: Vacuoles were apparent; increased cellular debris, swollen mitochondria, and phagocytic structures were observed; and membranes became more disorganized. Similar ultrastructural changes were observed in the Sertoli cells of DPP-treated rats. By 3 hours, spermatocytes and spermatids were adversely affected by CDB-4022 treatment with swelling of the nuclear envelope. The Step 8 spermatids were especially noteworthy; chromatin was more diffuse and rarefied, the nuclear envelopes were incomplete or broken, and the position of the spermatid nucleus within the cell and relative to Sertoli cell cytoplasm was unusual. Fusion of spermatids to form giant cells was observed by 12 hours. CDB-4022 acts acutely on Sertoli cells to induce marked cellular rarefaction and degeneration, but not necrosis. A rapid and direct effect of CDB-4022 on spermatocytes and spermatids was observed. The antispermatogenic activity of CDB-4022 appears to be a consequence of direct effects on Sertoli and germ cells.

In vitro development of foetal male germ cells in rats, mice and humans

Le potentiel reproducteur de l’adulte depend, en partie, de la mise en place de la lignee germinale pendant la vie fœtale et neonatale. Une hypothese recente assez largement partagee suggere que l’augmentation des alterations de la reproduction masculine observee au cours des dernieres decennies, comme la diminution de la production spermatique et l’augmentation de l’incidence des cancers testiculaires, resulterait de modifications du developpement de la lignee germinale pendant la vie fœtale et neonatale en reponse a l’augmentation de la pollution environnementale. Cependant peu d’outils sont disponibles pour etudier le developpement de la lignee germinale fœtale et neonatale. Nous decrivons ici un systeme de culture organotypique dans lequel le testicule se developpe sur un filtre flottant a la surface d’un milieu synthetique ne contenant ni serum ni facteurs biologiques. Chez le rat et la souris, nous avons compare le developpement des cellules de Sertoli et des cellules germinates dans ce systeme avec leur developpement observein vivo. Ces cellules se developpent normalement chez le rat sur une periode de deux semaines. Moins de cellules sont produites qu’in vivo mais les fonctions de chaque cellule sont comparables. Des resultats similaires ont ete observes chez la souris, mais la duree de maintienin vitro est plus courte que chez le rat et ce sont les stades fœtaux les plus jeunes qui donnent les meilleurs resultats. En utilisant ce modele, nous avons pu etudier le developpement de la lignee germinale de testicules preleves immediatement avant la naissance sur des fœtus invalides pour p63, un gene requis pour la survie postnatale, et montrer que p63 est implique dans le controle de l’apoptose neonatale de la lignee germinale. Enfin, nous avons etendu ce modele de culture a l’espece humaine (6 a 12 semaines de grossesse) et montre que l’on peut maintenir l’architecture testiculaire et les cellules germinates pendant 4 jours avec une efficacite superieure pour les stades jeunes (moins de 8 semaines). En conclusion, ce modele est potentiellement tres interessant pour etudier l’effet de facteurs physiologiques ou toxiques sur la mise en place de la lignee germinale chez le mâle.

Coxsackie and adenovirus receptor (CAR) is a product of Sertoli and germ cells in rat testes which is localized at the Sertoli–Sertoli and Sertoli–germ cell interface

The coxsackie and adenovirus receptor (CAR), a putative cell–cell adhesion molecule, has attracted wide interest due to its importance in viral pathogenesis and in mediating adenoviral gene delivery. However, the distribution pattern and physiological function of CAR in the testis is still not clear. Here, we identified CAR in Sertoli cells and germ cells of rats. In vivo studies have shown that CAR resides at the blood–testis barrier as well as at the ectoplasmic specialization. The persistent expression of CAR in rat testes from neonatal period throughout adulthood implicates its role in spermatogenesis. Using primary Sertoli cell cultures, we observed a significant induction of CAR during the formation of Sertoli cell epithelium. Furthermore, CAR was seen to be concentrated at inter-Sertoli cell junctions, co-localizing with tight junction protein marker ZO-1 and adherens junction protein N-cadherin. CAR was also found to be associated with proteins of Src kinase family and its protein level declined after TNFα treatment in Sertoli cell cultures. Immunofluorescent staining of isolated germ cells has revealed the presence of CAR on spermatogonia, spermatocytes, round spermatids and elongate spermatids. Taken together, we propose that CAR functions as an adhesion molecule in maintaining the inter-Sertoli cell junctions at the basal compartment of the seminiferous epithelium. In addition, CAR may confer adhesion between Sertoli and germ cells at the Sertoli–germ cell interface. It is possible that the receptor utilized by viral pathogens to breakthrough the epithelial barrier was also employed by developing germ cells to migrate through the inter-Sertoli cell junctions.

Transcripts of Aromatase and Estrogen Receptors and Significance of Other RNAs in Human Spermatozoa

The existence of a complex population of mRNAs in human sperm is well documented but their role is not completely elucidated. Evidence for a latent transcriptional capacity and/or a potential translation de novo in mature spermatozoa from fertile men has been provided and is helpful in understanding the final steps of sperm maturation (capacitation and/or the acrosome reaction). Spermatogenesis is controlled by gonadotrophins and testosterone, their effects are modulated by locally-produced factors that include estrogens derived from the irreversible transformation of androgens by aromatase. The data demonstrating an additional source of estrogens in rat germ cells along with several studies showing a decreased sperm motility in men deficient in aromatase has led to the further explanation of the expression of aromatase in ejaculated spermatozoa from fertile men. A significant decrease in the amount of aromatase transcripts in the immotile sperm fraction was recorded. In addition, the levels of transcripts encoding for proteins involved in either nuclear condensation protamines 1 and 2 (Prm1 and Prm2) or in capacitation endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide sythase (nNOS) and c-myc were compared in low and high motile sperm prepared from the same sample. No significant change in the ratio of c-myc/Prm2 between the two populations of spermatozoa was observed. Conversely the amount of Prm1 mRNA was significantly higher in the low motile fraction than in the high motile fraction; in most of the high motile sperm samples analyzed, eNOS and nNOS transcripts were undetectable, whereas they were observed in low motile sperm. Moreover, a partial or complete disappearance of c-myc transcripts was observed after capacitation. Analysis of the mRNA profile in human ejaculated sperm could be helpful either as a diagnostic tool to evaluate the male gamete quality and/or as a prognostic value for fertilization and embryo development.

Two-Dimensional Fluorescence Difference Gel Electrophoresis Analysis of Spermatogenesis in the Rat

The molecular mechanisms underlying normal and pathological spermatogenesis remain poorly understood. We compared protein concentrations in different germ cell types to identify those proteins specifically or preferentially expressed at each stage of rat spermatogenesis. Crude cytosolic protein extracts and reversed-phase HPLC prefractionated cytosolic extracts from spermatogonia, pachytene spermatocytes, and early spermatids were subjected to two-dimensional difference gel electrophoresis (2-D DIGE). By comparing gels and carrying out statistical analyses, we were able to identify 1274 protein spots with relative abundances differing significantly between the three cell types. We found that 265 of these spots displaying highly differential expression (ratio > or = 2.5 between two cell types), identified by mass fingerprinting, corresponded to 123 nonredundant proteins. The proteins clustered into three clades, corresponding to mitotic, meiotic, and post-meiotic cell types. The differentially expressed proteins identified by 2-D DIGE were confirmed and validated by western blotting and immunohistochemistry, in the few cases in which antibodies were available. 2-D DIGE appears a relevant proteomics approach for studying rat germ cell differentiation, allowing the establishment of the precise expression profiles for a relatively large number of proteins during normal spermatogenesis.

Expression of galectin‐3 and its regulation in the testes

Although spermatogenesis is a complex process under hormonal control, which includes mainly follicle stimulating hormone (FSH) and androgens, little is known about the intra-testicular mediators of these hormones. In the present study, galectin-3 (Gal-3) expression has been identified in human, rat and porcine testes where it is under hormonal control. Gal-3 is present in Sertoli cells and appears to be absent in human and (probably) in rat germ cells. Gal-3 expression was evidenced in the testes, in terms of both mRNA and protein (31 kDa). Gal-3 expression in cultured porcine Sertoli cells was shown to be under the positive control of FSH as well as of two cytokines epidermal growth factor (EGF) and tumour necrosis factor-alpha (TNF-alpha). Gal-3 expression in Sertoli cells is also potentially under the control of mature germ cells as an increased expression was observed in adult rat testes depleted in spermatocytes or spermatids. Although the function of testicular Gal-3 remains to be investigated, a potential role of Gal-3 in germ cell survival/regeneration is suggested based on its increased expression 1 month after a transient germ cell death process triggered by 10 days of treatment with the antiandrogen flutamide. Finally, although in the normal human testes, Gal-3 is exclusively located in the Sertoli cell cytoplasm, a nuclear localization is observed in the infertile testes. Together, the present findings have shown that (i) Gal-3 is expressed in the porcine, rat and human Sertoli cells; (ii) Gal-3 is under the positive control of FSH as well as of EGF and TNF-alpha and possibly of adult germ cells. These observations are compatible with a potential pro-survival role of Gal-3 in the testes.

β‐nerve growth factor participates in an auto/paracrine pathway of regulation of the meiotic differentiation of rat spermatocytes

NGF appears to be involved in spermatogenesis. However, mice lacking NGF or TrkA genes do not survive more than a few days whereas p75(NTR) knockout mice are viable and fertile. Therefore, we addressed the effect of betaNGF on spermatogenesis by using the systems of rat germ cell culture we established previously. betaNGF did not modify the number of Sertoli cells, pachytene spermatocytes, secondary spermatocytes nor the half-life of round spermatids, but increased the number of secondary meiotic metaphases and decreased the number of round spermatids formed in vitro. These effects of betaNGF were reversible and maximal at about 4 x 10(-11) M. Conversely, K252a, a Trk-specific kinase inhibitor, enhanced the number of round spermatids above that of control cultures. The presence of betaNGF and its receptors TrkA and p75(NTR) was investigated in testis sections, in Sertoli cell and germ cell fractions, and in germ cell and Sertoli cell co-cultures. betaNGF was detected only in germ cells from pachytene spermatocytes of stages VII up to spermatids of stages IX-X. TrkA and p75(NTR) were detected in Sertoli cells and in these germ cells. Taken together, these results indicate that betaNGF should participate in an auto/paracrine pathway of regulation of the second meiotic division of rat spermatocytes in vivo.

Preliminary research on effects of subchronic exposure to hydroxylammonium nitrate on tests germ cells of male rats

目的 探讨硝酸羟胺(hydroxylammonium nitrate,HAN)亚慢性染毒对大鼠睾丸的生殖细胞毒性.方法 将雄性Wistar大鼠40只随机分为3个染毒组及1个对照组,分别以HAN 6.97、13.93、27.86 mg/kg剂量和生理盐水,隔日腹腔注射1次,连续染毒13周后采用流式细胞仪对大鼠睾丸生殖细胞倍体进行分析,观察大鼠精子和头部的畸形率.结果 3个染毒组大鼠精子总畸形率与头部畸形率均高于对照组,差异无统计学意义(P＞0.05);流式细胞仪分析结果中,6.97、13.93 mg/kg组单倍体细胞数及长形精子细胞数与对照组比较有增加趋势,并随染毒剂量增加而增加,差异无统计学意义(P＞0.05).27.86mg/kg组单倍体细胞数及长形精子细胞数较其他3组减少,且单倍体细胞数(52.01±14.16)与中剂量13.93 mg/kg组(69.43±6.88)比较,差异有统计学意义(P＜0.05).结论 HAN亚慢性染毒对大鼠睾丸生殖细胞可能有损害作用。

Effect of cocaine on germ cell apoptosis in rats at different ages

To investigate the effect of cocaine on apoptosis and caspase-3 activity in germ cells in male rats at different ages. Cocaine hydrochloride was given (15 mg/kg body weight s.c.) to male Sprague-Dawley rats of 3 weeks (n = 8), 6 weeks (n = 8) and 12 weeks (n = 8) of age, daily for 28 Days. The serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), testosterone (T) and estrogen (E2) were assayed, and the DNA fragmentation of germ cells was determined by gel eletronphoresis. The cell cycle, apoptosis and caspase-3 activity of germ cells were tested by flow cytometry. After the 28-day cocaine treatment, testes weight of the 3-week-old rats, the testes and body weights of the 6-week-old rats were decreased significantly compared to those of their corresponding controls (P < 0.05). The serum level of T was decreased significantly in the 3-week-old and 6-week-old rats, and the serum level of PRL was also decreased significantly in 12-week-old rats compared to the controls (P < 0.05). In all the three cocaine-treated groups, the isolated DNA displayed a clear ladder pattern, especially in the 6-week old rats. The number of apoptosic germ cells increased significantly in 3- and 6-week-old rats treated with cocaine (P < 0.05). The caspase-3 activity in all three groups increased significantly compared to the controls (P < 0.05), especially in the 6-week-old rats. Cocaine exposure for 28 Days leads to significant damage to male gonad and apoptosis elevation in testes of rats of different ages, especially in those of 6 weeks of age. The increase in caspase-3 activity might be a key pathway related to the early stage of apoptosis as the mechanism of cocaine-induced germ cell loss.

Irradiated Mouse Testes Efficiently Support Spermatogenesis Derived From Donor Germ Cells of Mice and Rats

Testicular cell transplantation has been widely used to investigate the biology of spermatogonial stem cells, production of transgenic animals, and restoration of fertility in rodent models. One critical step in successful transplantation is the preparation of the recipient testes. Busulfan has been widely used, but irradiation has been often suggested as an alternative. There have only been limited reports of the use of irradiated animals as transplant recipients for studying differentiation of transplanted cells, and there has been no direct comparison of irradiation and busulfan as preparation methods. Mouse testes treated with local fractionated irradiation (1.5 + 12 Gy) were compared with busulfan-treated testes as recipients using mouse-to-mouse and rat-to-mouse germ cell transplantation. The fractionated irradiation schedule resulted in depletion of endogenous spermatogenesis similar to that produced by busulfan doses of 50-55 mg/kg. When immature mouse or rat testicular germ cells were transplanted into the irradiated testes, donor cells derived from either rat or mouse spermatogonial stem cells were able to form colonies of differentiated spermatogenic cells 10-13 weeks after transplantation with similar efficiencies as in busulfan-treated testes. Locally irradiated testes could be considered as an alternative to busulfan treatment for animal recipients of germ cell transplants that cannot endure the systemic toxicity of busulfan.

Caspase activation throughout the first wave of spermatogenesis in the rat

Early in postnatal life, the first wave of spermatogenesis is accompanied by an initial wave of germ cell apoptosis. This may reflect an adjustment in the number of germ cells that can be adequately maintained by Sertoli cells. Two major pathways (intrinsic and extrinsic) are involved in the process of caspase activation and apoptosis in mammalian cells. The extrinsic pathway is characterized by the oligomerization of death receptors such as FAS or tumor necrosis factor, followed by the activation of caspase-8 and caspase-3. The intrinsic pathway involves the activation of procaspase-9, which in turn activates caspase-3. Extensive information is available concerning apoptotic inducers and their possible mechanisms in the adult rat. However, no data exist regarding the molecular and cellular mechanisms governing physiological cell death during puberty in the male rat. We have studied caspase activation throughout the first wave of spermatogenesis in the rat under physiological conditions, by combining the TUNEL procedure with the localization of active caspases in germ cells. We observed TUNEL-positive germ cells in rats of 5-40 days of age, the highest number being found in 25-day-old rats. TUNEL-positive and caspase-3-positive germ cells appeared as long chains of interconnected germ cells in 25-day-old rats. Caspase activation was assayed by either immunohistochemistry with antibodies against active caspase-3, -8, and -9, or by determining enzymatic activity in seminiferous tubules extracts. Both techniques showed activation of caspase-3, -8, and -9 in 25-day-old rats and low enzymatic activity at other ages. Confocal scanning laser microscopy indicated that active caspase-3, -8, and -9 co-localized with TUNEL-positive cells. Thus, caspase-3, -8, and -9 are active in apoptotic germ cells during the first wave of rat spermatogenesis. The extrinsic pathway of apoptosis may therefore play an important role in germ cell apoptosis during puberty in the rat.

Hepatocyte growth factor modulates in vitro survival and proliferation of germ cells during postnatal testis development

The hepatocyte growth factor (HGF) is a pleiotropic cytokine that influences mitogenesis, motility and differentiation of many different cell types by its tyrosine kinase receptor c-Met. We previously demonstrated that the c-Met/HGF system is present and functionally active during postnatal testis development. We found also that spermatozoa express c-Met and that HGF has a positive effect on the maintenance of sperm motility. In the present paper, we extend our study on the germ cells at different stages of differentiation during the postnatal development of the testis. We demonstrate that c-met is present in rat spermatogonia, pachytene spermatocytes and round spermatids and that HGF significantly increases spermatogonial proliferation in 8- to 10-day-old pre-pubertal rats. At this age HGF does not affect Sertoli cells and peritubular myoid cells proliferation. In addition, we studied the effect of the factor on germ cell apoptosis and we show that HGF prevents the germ cell apoptotic process. We also studied the effect of HGF on 18- to 20-day-old and 28- to 30-day-old rat testes. At these ages also the factor significantly increases germ cell duplication and decreases the number of apoptotic cells. However, the effect on programmed cell death is higher in the 8- to 10-day-old rats and declines in the older animals. In conclusion, we report that rat germ cells (spermatogonia, pachytene spermatocytes and round spermatids) express c-met and that HGF modulates germ cell proliferating activity and apoptosis in vitro. These data indicate that the c-Met/HGF system is involved in male germ cell homeostasis and, consequently, has a role in male fertility.

Interleukin-6 and IL-6 receptor cell expression in testis of rats with autoimmune orchitis

Experimental autoimmune orchitis (EAO) is an organ-specific model of autoimmunity characterized by an interstitial lymphomononuclear cell infiltrate as well as sloughing and apoptosis of germ cells. EAO was induced in adult male Sprague–Dawley rats by active immunization with testicular homogenate and adjuvants. Rats injected with saline solution and adjuvants were used as control group. The aim of this work was to study the expression of interleukin-6 (IL-6) and its receptor (IL-6R) in the testis of rats with EAO and analyze whether IL-6 could be involved in germ cell apoptosis. By immunohistochemistry, we detected IL-6 expression in testicular macrophages and Leydig cells of control and EAO rats. Sertoli cells showed IL-6 immunoreactivity in most of the seminiferous tubules of control rats, while a few IL-6 + Sertoli cells were found in the testis of rats with EAO. IL-6R immunoreactivity was observed in macrophages, Leydig and germ cells. A significant increase was noted in the number of IL-6R + germ cells in rats with EAO compared to control rats. The content of IL-6 (ELISA) in the conditioned media obtained from testicular macrophages of rats with orchitis was significantly higher than in the control group. By immunofluorescence performed on isolated testicular macrophages, IL-6 was shown to be expressed by monocytes recently arrived from circulation (ED1 + cells), while resident macrophages (ED2 + cells) were negative. In vitro experiments (trypan blue and MTS assays) showed that IL-6 (50 ng/ml) reduced germ cell viability. We demonstrated also using the TUNEL technique that IL-6 added to cultures of seminiferous tubule segments induced apoptosis of germ cells. Our results suggest that IL-6 and IL-6R may be involved in the pathogenesis of autoimmune orchitis by promoting testicular inflammation and germ cell apoptosis.