Influence of germ cells upon Sertoli cells during continuous low-dose rate gamma-irradiation of adult rats

Evaluating the radioprotective effect of green barley juice on male rats

PURPOSE

DNA damage accounts for most biological effects of ionizing radiation. Antioxidants are known for their protective effect by preventing DNA damage. This pilot study aimed to evaluate the potential radioprotective effect of Natural SOD®, a green barley juice rich in antioxidants, on DNA damage in the testes and lymphocytes of Wistar rats exposed to ionizing radiation.

MATERIALS AND METHODS

Male Wistar rats (n = 15) were selected and equally divided into three groups. Rats in one of the groups were pretreated orally with Natural SOD® for 14 days, while rats in another group were sham-pretreated with saline solution. Rats in both these groups were afterwards subjected to a single dose of 6 Gy X-ray whole-body irradiation. The control group did not receive any treatment and was not irradiated. Shortly after X-ray exposure, all rats were sacrificed and testes and blood were collected. Gamma-H2AX and histopathological assessment in the testes, along with comet assay of lymphocytes were performed.

RESULTS

Histopathological examination of the testes showed no significant architectural alterations. Immunofluorescent staining of γ-H2AX revealed more DNA double-strand break sites in testicular cells from sham animals compared to Natural SOD® pretreated rats. Alkaline comet assay results showed increased DNA damage in lymphocytes of irradiated rats compared to the control group with little differences between the pretreated groups. Animals pretreated with Natural SOD showed slightly reduced DNA damage compared to sham-pretreated rats. These findings suggest a potential protective effect of Natural SOD® against radiation-induced DNA damage.

CONCLUSIONS

Natural SOD® exhibited a potential prophylactic radioprotective effect in rats, particularly in testes. Further investigations to determine medium and long-term effects of X-ray in animals administered Natural SOD® are needed to better estimate the radioprotective effect.

The effectiveness of traditional Japanese medicine Goshajinkigan in irradiation-induced aspermatogenesis in mice

Background

Infertility and gonadal dysfunction are well known side-effects by cancer treatment in males. In particularly, chemotherapy and radiotherapy induced testicular damage, resulting in prolonged azoospermia. However, information regarding therapeutics to treat spermatogenesis disturbance after cancer treatment is scarce. Recently, we demonstrated that Goshajinkigan, a traditional Japanese medicine, can completely rescue severe busulfan-induced aspermatogenesis in mice. In this study, we aimed to detect the effects of Goshajinkigan on aspermatogenesis after irradiation.

Methods

This is animal research about the effects of traditional Japanese medicine on infertility after cancer treatment. C57BL/6 J male mice received total body irradiation (TBI: a single dose of 6Gy) at 4 weeks of age and after 60 days were reared a Goshajinkigan (TJ107)-containing or TJ107-free control diet from day 60 to day 120. Then, two untreated females were mated with a single male from each experimental group. On day 60, 120 and 150, respectively, the sets of testes and epididymis of the mice in each group after deep anesthetization were removed for histological and cytological examinations.

Results

Histological and histopathological data showed that 6Gy TBI treatment decreased the fertility rate (4/10) in the control diet group; in contrast, in the TJ107-diet group, the fertility rate was 10/10 (p < 0.05 vs. 6Gy group). Supplementation with TJ107 was found to rescue the disrupted inter-Sertoli tight junctions via the normalization of claudin11, occludin, and ZO-1 expression and reduce serum anti-germ cell autoantibodies.

Conclusions

These findings show the therapeutic effect on TBI-induced aspermatogenesis and the recovering disrupted gonadal functions by supplementation with TJ107.

Effects of Chemotherapy and Radiotherapy on Spermatogenesis: The Role of Testicular Immunology

Substantial improvements in cancer treatment have resulted in longer survival and increased quality of life in cancer survivors with minimized long-term toxicity. However, infertility and gonadal dysfunction continue to be recognized as adverse effects of anticancer therapy. In particular, alkylating agents and irradiation induce testicular damage that results in prolonged azoospermia. Although damage to and recovery of spermatogenesis after cancer treatment have been extensively studied, there is little information regarding the role of differences in testicular immunology in cancer treatment-induced male infertility. In this review, we briefly summarize available rodent and human data on immunological differences in chemotherapy or radiotherapy.

NORMAL TISSUE REACTIONS TO CHRONIC RADIATION EXPOSURE IN MAN

This paper presents an overview of radiobiological dependences governing the occurrence of tissue (organ) reactions that determine the outcomes of chronic exposure to low-LET ionizing radiation (IR) in humans. The mechanisms involved in the development of tissue reactions (TRs) to long-term exposures to IR and radioadaptation are considered. The overview describes the reactions of the haematopoietic, immune, nervous, reproductive and endocrine systems, lungs, skin and crystalline lens to chronic radiation exposure, which are of fundamental importance in view of radiation protection. It is shown that the individual's physiological tissue (organ) reserve, and also that induced by radiation exposure at low-dose rates are of great significance in the context of TR development.

Functional Analysis of the Cooled Rat Testis

Direct cooling of the testis results in the depletion of most germ cells in vivo. Germ cell-depleted testes are now commonly used to investigate spermatogenic regeneration and can serve as recipients for germ cell transplantation. The present study explored the effects of cooling rat testes on the depletion of endogenous germ cells, spermatogenic regeneration, and Sertoli cell function. Adult rat testes were cooled with iced Ringer's solution for 60 minutes, which results in the initiation of apoptotic germ cell loss within 8 hours. Pachytene spermatocytes at stages XII-I were the cells most sensitive to cooling. In 46%-67% of seminiferous tubule cross-sections, only Sertoli cells remained in the cooled testes 3-10 weeks after treatment. Germ cell loss was accompanied by a significant decrease in circulating inhibin B and an increase in follicle-stimulating hormone concentrations, which indicated a change in Sertoli cell function. Quantitative analysis of mRNA expression associated with apoptotic signals showed no significant uniform changes among the cooled testes, although some individuals had a distinct up-regulation of FAS mRNA at 24 hours. Attempts to use the cooled testes as recipient testes for mouse-to-rat germ cell transplantation were undertaken, but none of the mouse germ cells transplanted into the testes 15-34 days after cooling appeared to have undergone spermatogenesis 64-92 days after transplantation. These data suggest that modifications to Sertoli cell function resulting from testicular cooling create an environment that is unable to support spermatogenesis by donor germ cells.

Apoptotic Cell Death Induced by Low-Dose Radiation in Male Germ Cells: Hormesis and Adaptation

Biological effects of low-dose radiation (LDR) in somatic cells have captured the interest of radiobiologists for the last two decades. Apoptosis of germ cells is required for normal spermatogenesis and often occurs through highly conserved events, including the transfer of vital cellular materials to the growing gametes following death of neighboring cells. Apoptosis of germ cells also functions in diverse processes, including removal of abnormal or superfluous cells at specific checkpoints, establishment of caste differentiation, and individualization of gametes. Moreover, germ cells are very sensitive to radiation-induced genomic and cytological effects. Therefore, induction of germ-cell apoptosis has been observed in the testis of animals exposed to both high-dose radiation (HDR) and LDR. Exposure of male germ cells to LDR induces a stimulating effect, while exposure to HDR causes an inhibitory effect on the metabolism, antioxidant capacity, and proliferation and maturation of cells, a phenomenon termed hormesis. Preexposure to LDR also protects cells from subsequently HDR-induced genomic and cytological effects, a phenomenon termed adaptive response. This review describes the features of male germ-cell apoptosis. It reviews the evidence that LDR induces the hormesis and adaptive responses in the male germ cells in terms of apoptosis. This review also discusses the possible effects of LDR-induced apoptotic hormesis and adaptive response on the modulation of inheritable genomic damage caused by subsequent radiation exposure to male germ cells.

Sertoli cell morphological alterations in albino rats treated with etoposide during prepubertal phase

Sertoli cells are very important to spermatogenesis homeostasis because they control germ cell proliferation, differentiation, and death. Damages to Sertoli cells cause germ cell death and affect fertility. Etoposide is a potent chemotherapeutic drug largely used against a variety of cancers. However, this drug also kills normal cells, especially those undergoing rapid proliferation. In the testis, etoposide acts predominantly on intermediate and type B spermatogonia. Etoposide was shown to permanently alter Sertoli cell function when administered to prepubertal rats. Based on this, we decided to investigate whether etoposide can affect Sertoli cell morphology. For this, 25-day-old rats were treated with etoposide during 8 consecutive days and killed at 32, 45, 64, 127, and 180 days old. Testes were fixed in Bouin's liquid or in a mixture of 2.5% glutaraldehyde and 2% formaldehyde for analysis under light and electron microscopes, respectively. Sertoli cells showed morphological alterations such as the presence of chromatin clumps close to the nuclear membrane, nucleus displacement, and cytoplasmic vacuolization. Some Sertoli cells also showed nuclear and cytoplasmic degenerative characteristics, suggesting that etoposide causes severe damages to Sertoli cell.

Effects of ionising radiation exposure on plants, fish and mammals: relevant data for environmental radiation protection

In order to develop a framework for the assessment of the environmental impact of radiation, it is necessary to establish the relationship between exposure (dose rate, accumulated dose) and the effects that may be induced in plants and animals. With this purpose in mind, the data available on effects induced by ionising radiation in various wildlife groups have been reviewed as part of the FASSET project. This paper has highlighted that the available information on the effects of low dose rate, continuous irradiation (< 10(3) microGy h(-1)) is reasonable for plants, fish and mammals, but is scarce or non-existent for other wildlife groups. Thus, the effects induced in plants, fish and mammals after chronic exposure to radiation are presented in this paper. The fragmentary nature of the available, relevant information has made it very difficult to characterise the desired dose rate-response relationships in any detail. However, it can be broadly concluded that, although minor effects may be seen at lower dose rates in the most sensitive species and systems, the threshold for statistically significant effects in most studies is about 10(2) microGy h(-1). The responses then increase progressively with increasing dose rate and usually become very clear at dose rates > 10(3) microGy h(-1) sustained for a large fraction of the lifespan.

Differential expression of Prx I and II in mouse testis and their up-regulation by radiation

Testis is one of the most sensitive organs to ionizing radiation. The present study was designed to unravel the possible role of antioxidant proteins, peroxiredoxin I and II (Prx I and II) in the testis. Our results show that Prx I and II are constitutively expressed in the testis and their expression levels are decreased to some extent as the testis develops. Interestingly, immunohistochemical analysis revealed a preferential expression of Prx I and II in Leydig and Sertoli cells, respectively. Neither Prx I nor Prx II expression was obvious in the testicular germ cells including spermatogonia and spermatocytes. Ionizing radiation exerted oxidative stress on the testis and induced apoptosis primarily in the germ cells. When the irradiated testis was examined, the Prx system was found to be transiently up-regulated. Taken together, we suggest that the relative radiation-resistance of Leydig and Sertoli cells could be attributed in part to the antioxidant function of the Prx system in these cells.

Male infertility risk factors in a French military population

We investigated infertility risk factors by conducting a population-based case-control study in the military population of the French town of Brest. Sixty couples who had sought medical advice for infertility of more than 12 months duration (cases) were compared with 165 couples who had had a child (controls). All the men in these couples had been employed by the military. The infertility risk factors studied were male and female medical factors, occupational and environmental exposures. We obtained age-adjusted odds ratios of 7.4 [95% confidence interval (CI): 1.4--39.5] for testis surgery, and 13.0 for varicocele (95% CI: 1.4--120.3) in men. In logistic regression, the age-adjusted odds ratio for men who had worked in a nuclear submarine was found to be 2.0 (95% CI: 1.0--3.7), and that for heat exposure was 4.5 (95% CI: 1.9--10.6). One limitation of this study is the lack of exposure measurements, especially for potential exposure to nuclear radiation (type of reactor used in nuclear-powered submarines, inability to obtain personal dosimeters worn by military personnel working in nuclear submarines). In conclusion, this study suggests that in this military population, having worked as a submariner in a nuclear-powered submarine, and having worked in very hot conditions, should be considered as risk factors for infertility.

Regulatory influence of germ cells on sertoli cell function in the pre-pubertal rat after acute irradiation of the testis

While germ cell regulation of Sertoli cells has been extensively explored in adult rats in vivo, in contrast, very little is known about germ cell influence on Sertoli cell function at the time when spermatogenesis begins and develops. In the present study various Sertoli cell parameters (number, testicular androgen binding protein (ABP) and testin, serum inhibin-B and, indirectly, follicle-stimulating hormone (FSH)) were investigated after the exposure of 19-day-old rats to a low dose of 3 Grays of gamma-rays. Differentiated spermatogonia were the primary testicular targets of the gamma-rays, which resulted in progressive maturation depletion, sequentially and reversibly affecting all germ cell classes. Testicular weight declined to a nadir when pachytene spermatocytes and spermatids were depleted from the seminiferous epithelium and complete or near complete recovery of spermatogenesis and testicular weight was observed at the end of the experiment. Blood levels of FSH and ABP were normal during the first 11 days after irradiation, when spermatogonia and early spermatocytes were depleted. While the number of Sertoli cells was not significantly affected by the irradiation, from days 11-66 after gamma-irradiation, ABP production declined and FSH levels increased when pachytene spermatocytes and spermatids were depleted and the recovery of these parameters was only observed when spermatogenesis was fully restored. Comparison of the pattern of change in serum levels of inhibin-B and testicular levels of testin and of germ cell numbers strongly suggest a relationship between the disappearance of spermatocytes and spermatids from the seminiferous epithelium and the decrease in levels of inhibin-B and increase in levels of testin from 7 to 36 days post-irradiation. Levels of testin and inhibin-B were restored before spermatogenesis had totally returned to normal. In conclusion, this in vivo study shows that pre-pubertal Sertoli cell function is under the complex control of various germ cell classes. This control presents clear differences when compared with that previously observed in adult animals and depends on the Sertoli cell parameter of interest, as well as on the germ cell type.

A novel gene (PD1) with a potential role on rat spermatogenesis

PD1 is a novel protein particularly expressed at the testicular level. The relative cDNA sequences were cloned from human and rat testis libraries revealing an open reading frame for a protein of 520 and 511 amino acids respectively. The human PD1 amino acid sequence shows 85% identity with rat sequence suggesting that PD1 gene has been highly conserved during mammalian evolution. Immunohistochemical analysis showed that this protein is detected in the tubular compartment of the testis and, in particular, in the cytoplasm of the Sertoli cells. PD1 expression is not constitutive but seems to be under the influence of neighboring spermatogenic cells as demonstrated by its reduction in hypospermatogenesis with respect to normal spermatogenesis and a further reduction in Sertoli cell-only syndrome. During testicular development in the rat (from 2 to 45 days of age) the PD1 mRNA level became detectable at 14 days and then increased steadily with an advancement of age. These findings suggest that PD1 may play a role in the regulation of spermatogenesis and may be a potential candidate gene for defects of male fertility.

cDNA cloning and characterization of PD1: a novel human testicular protein with different expressions in various testiculopathies

A novel human cDNA sequence has been isolated from human testis cDNA library. This sequence, named PD1, reveals an open reading frame encoding a protein of 520 amino acids. A partial sequence similarity has been found with the RBM gene involved in the regulation of human spermatogenesis. Northern blot analysis for PD1 mRNA from several human tissues demonstrated two distinct transcripts of 2.7 (more abundant) and 4.0 kb and revealed that PD1 is expressed in testis and to a lesser extent also in spleen, thymus, and prostate. Immunohistochemical analysis of human testis showed that this protein is detected in the cytoplasm of Sertoli cells. Antibodies against a rhPD1 fragment were used for Western blot analysis, which confirmed the presence of a 60-kDa molecule in crude extract of human testicular cells obtained from fine-needle aspiration and showed different patterns in various testiculopathies, suggesting a role for such gene in human spermatogenesis.

mRNAs encoding a von Ebner's-like protein and the Huntington disease protein are induced in rat male germ cells by Sertoli cells

The success of spermatogenesis is dependent upon closely coordinated interactions between Sertoli cells and germ cells. To identify specific molecules that mediate interactions between somatic cells and germ cells in the rat testis, Sertoli cell-germ cell co-cultures and mRNA differential display were used. Two cDNAs, clone 1 (660 nucleotides) and clone 2 (390 nucleotides) were up-regulated when Sertoli cells were co-cultured with pachytene spermatocytes or round spermatids. Northern blot analyses confirmed the differential display expression patterns. Sequence analyses indicated that clone 1 was similar to a von Ebner's gland protein (87% at the nucleotide level and 80% at the amino acid level) and clone 2 was identical to a region of the Huntington disease protein. The von Ebner's-like protein mRNA was induced after 4 h of co-culture, while the Huntington disease protein required 18 h of co-culture for expression. The von Ebner's-like protein was induced in germ cells by a secreted Sertoli cell factor(s) smaller than 10 kDa that is sensitive to freezing and thawing or boiling. The Huntington disease protein was induced in germ cells by a Sertoli cell secreted factor(s) larger than 10 kDa which survives freezing and thawing, but is inactivated by boiling.

Sertoli cell barrier dysfunction and spermatogenetic cycle breakdown in the human testis: a lanthanum tracer investigation

The introduction of nitrate of lanthanum in fixative solutions for testicular biopsies improves ultrastructural observations of the blood-testis barrier. In complete (normal) spermatogenesis, junctional specializations impede the diffusion of lanthanum into the adluminal compartment. They clearly exhibit a three-storied disposition in orthogonal sections. In maturation arrest, lanthanum passes easily through the junctional specializations surrounding the germ cells and up to the lumen. In irregular hypospermatogenesis, the Sertoli cell barrier is permeable, but diffusion of the tracer is less significant and variable. Unexpectedly, in germ cell aplasia, the barrier remains efficient

Impairment of testicular endocrine function after lead intoxication in the adult rat

To clarify the mechanism of the action of lead on male reproductive function, adult male rats were injected intraperitoneally (i.p.) with lead acetate (8 mg/kg/day of lead), 5 days a week for 35 days. Despite this high dose, germ cells and Sertoli cells did not appear to be major targets of lead. However, lead determination in the reproductive organs showed that the accessory sex glands are such a target. Epididymal function was unchanged. In lead-exposed rats, plasma and testicular testosterone dropped by about 80%, but plasma luteinizing hormone (LH) only dropped by 32%. After luteinizing hormone releasing hormone (LHRH) stimulation of the pituitary, the plasma LH level reached the control one, but plasma testosterone remained significantly reduced by 37%. The sharp decrease in the testosterone:LH ratio in lead-exposed rats, combined with the significant reduction of intertubular tissue volume in the testes, indicate impaired Leydig cell function.

Effect of age on seminiferous tubule protein secretion and the adverse effects of testicular toxicants in the rat

This study has assessed the effect of age on protein secretion by seminiferous tubules (ST) isolated from rats and their response to Sertoli cell toxicants. ST were isolated from immature (aged 28 days), late pubertal (aged 45 days) and young adult (aged 70 days) rats and cultured in vitro for 24 h with 35S-methionine in the presence or absence of FSH (1 mg/ml), m-dinitrobenzene (m-DNB) or nitrobenzene (NB) (both at 10(-4)M). Incorporation of 35S-methionine into newly synthesized proteins in the culture medium (secreted proteins) was assessed and the pattern of protein secretion evaluated using two-dimensional sodium dodecylsulphate polyacrylamide gel electrophoresis (2-D SDS-PAGE). These data were compared with those obtained using cultures of immature rat Sertoli cells+germ cells (SC+GC). Addition of FSH, m-DNB or NB in vitro either had no effect (NB) or had a small stimulatory effect (FSH and m-DNB) on the incorporation of 35S-methionine into overall secreted proteins by ST isolated from immature rats. At the same doses, addition of either FSH, m-DNB or NB to SC+GC co-cultures resulted in increased incorporation of radiolabel into secreted proteins in all instances. In contrast, the same additions to ST isolated from adult rats resulted in a 20-34% decrease in the overall incorporation of 35S-methionine into secreted proteins. ST isolated from late pubertal rats showed a similar response to adult rats except that the decreases in incorporation induced by FSH, m-DNB and NB were smaller. Analysis by 2-D SDS-PAGE revealed considerable age-dependent differences in the proteins secreted by ST from immature and adult rats, of which 13 were identified as being of potential importance. Most of these proteins were prominent secretory products of ST from adult rats, but were minor or non-detectable products of cultures of ST or SC+GC from immature rats. Most of these proteins disappeared or decreased in abundance after culture of ST with m-DNB or NB. Two proteins showed the reverse pattern, being more prominent secretory products in immature than mature rats, and their secretion was unaffected or was increased by toxicant exposure. These results demonstrate that there are major age-dependent differences in the secretion of total and specific proteins by isolated ST and that these are probably related to changes in the germ cell complement with age.(ABSTRACT TRUNCATED AT 400 WORDS)

A 29,000 M(r) protein derived from round spermatids regulates Sertoli cell secretion

Within the last decade it has become accepted that germ cells can modulate Sertoli cell function in a paracrine interactive manner during the regulation of spermatogenesis. In this context, we undertook to identify a specific factor in round spermatid conditioned media that could stimulate Sertoli cell secretory function. Rat round spermatids isolated by centrifugal elutriation were cultured and the concentrated conditioned media were fractionated by Sephacryl S-200 gel filtration column chromatography. The biological activity of the fractionated round spermatid protein was assessed as stimulation of total protein and transferrin secretion from Sertoli cells that had been isolated from 18-day-old immature rat testes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the gel-filtration fractions showed two predominant proteins of 29,000 and 24,500 molecular weight which coexisted in the fractions containing the greatest biological activity. These two proteins were transferred to a nitrocellulose membrane and excised to raise polyclonal antibodies. Western blot analysis of the 29,000 M(r) protein demonstrated that it specifically occurred in round spermatid conditioned media, whereas no immunoreactive band was observed in either the conditioned media or cell lysates of other testicular cell types such as primary spermatocytes, Sertoli cells and peritubular myoid cells. Following subcellular fractionation of round spermatids by differential centrifugation, the 29,000 M(r) protein was detected by Western blots specifically in the cytosolic fraction of round spermatids, and was absent from the nuclear, mitochondrial, lysosomal and microsomal fractions. The antibody did recognize a few higher molecular bands in the cytosolic fraction which may represent precursor forms of the 29,000 M(r) protein.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of specific germ cell types in modulation of the secretion of androgen-regulated proteins (ARPs) by stage VI-VIII seminiferous tubules from the adult rat

This study has assessed the role of specific germ cell types in modulating the secretion of seven previously identified androgen-regulated proteins (ARPs) as well as the increase in overall level of protein secretion by seminiferous tubules (ST) at stages VI-VIII of the spermatogenic cycle in the rat. Methoxyacetic acid (MAA) was administered at 650 mg/kg to induce 80-100% depletion of pachytene and later spermatocytes; ST at stages VI-VIII were then isolated at 4, 18 and 30 days after MAA treatment when pachytene spermatocytes (PS), round spermatids (RS) or elongate spermatids (ES), respectively, were depleted selectively. By comparison with ST isolated from controls or from rats 4 days after ethanedimethane sulphonate (EDS)-induced testosterone withdrawal, the overall level of incorporation of 35S-methionine into ST-secreted proteins was assessed after culture for 22 h at 32 degrees C as well as the relative abundance of ARPs identified by two-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Depletion of PS caused a substantial decrease in abundance of ARP-6 (53-57 kDa; pI 5.7-5.8) and ARP-7 (56-59 kDa; pI 5.9-6.2) and minor and more variable decreases in ARP-3 (27-30 kDa; pI 7.4) and ARP-4 (38 kDa; pI 6.0-6.2); ARP-6 and ARP-7 are comparable in size to the A and B forms of P-Mod-S, a product of the peritubular cells. Depletion of RS resulted in the complete disappearance of ARP-2 (13-14.5 kDa; pI 7.3-7.6), a decrease in abundance of ARP-7 and variable decreases in ARP-1 (approximately 9.5 kDa; pI 6.9-7.4) and ARP-6; ARP-1 and -2 are thought to be Sertoli cell-secreted proteins. Depletion of ES had no effect on secretion of the ARPs. Depletion of PS, RS or ES resulted in significant (P less than 0.001) decreases of 26, 38 and 42% respectively in the overall level of incorporation of methionine into ST-secreted proteins, but this was significantly less than the decrease (55%) induced by EDS-induced testosterone withdrawal. These results show that the androgen-dependent changes in secretion of proteins, which occur specifically at stages VI-VIII of the normal spermatogenic cycle, are largely, if not completely, dependent on a normal germ cell complement, with each germ cell type regulating the secretion of proteins essential for its own development.(ABSTRACT TRUNCATED AT 400 WORDS)

Spermatids are regulators of Sertoli cell function

Spermatids are major regulators of Sertoli cell function. Specific anatomical structures exist between spermatids and Sertoli cells. Their nature evolves during spermiogenesis and they are essential mediators in the interaction between these two cell types. Spermatids play a crucial role in Sertoli cell gene expression and secretory function at different ages. Early spermatid effect is partly mediated through the secretion of soluble factor(s). The influence of late spermatids on Sertoli cell secretion in the adult testis is conserved throughout evolution and may be mediated via their implication in the conformational changes on Sertoli cells that occur during spermatogenesis and through phagocytosis of the residual bodies.

Testicular x-ray irradiation in adult mice as a model to study spermatogonial proliferation

Testicular irradiation (300 r) of sexually mature mice provides a good model to study spermatogonial proliferation. DNA specific activity can be used under these conditions as a suitable assay of the proliferation and differentiation of testicular cells.

Stage- and cell-specific gene expression and hormone regulation of the seminiferous epithelium

The regulation of spermatogenesis seems to involve complex cell interactions in the testis. Little is known about these cellular communication events. Advances in molecular technology and cell or cell group separation methods have made it possible to analyze function of defined spermatogenic and Sertoli cells, thereby giving some insights into the paracrine regulation of spermatogenesis. In this review we will describe how seminiferous tubule segments with distinct cell associations can be rapidly isolated and how the cell composition can be modified by high-energy X-irradiation. Results of the recent studies performed using these techniques will be briefly summarized. Spermatogenic cells at defined stages of their development can be isolated in living condition for morphological and biochemical studies by the transillumination technique. For accurate identification of the stages of the seminiferous epithelial cycle, phase contrast microscopy of live cell squashes has been used. The criteria described by Leblond and Clermont (Am. NY Acad. Sci., 55:548-573, 1952) can be used for accurate recognition of most of the stages of the cycle. However, stages I and II and substages of VII that are important in several studies are difficult to distinguish. Therefore, in addition to the morphology of early spermatids, development of the flagella at step 16 of spermiogenesis and the changing morphology of the cytoplasmic lobes (residual bodies) at stage VII of the cycle were used as criteria for rapid identification and isolation (preparative) of the seminiferous tubule segments. Expression of nucleoprotein and heat shock protein 70-related protein genes was analyzed with Northern blot, slot blot, and in situ hybridization techniques in accurately staged seminiferous tubules. Accurate stage-dependent timing of the onset of transcription, followed by storage and disappearance of the messages was demonstrated. The chromatoid body (cb) has been proposed to have a specific function in storage of the long-lived mRNAs in the spermatids. It is an actively moving cytoplasmic organelle that interacts with Golgi complex during formation of the acrosomic system. The chromatoid body is apparently also dependent on cytoplasmic microtubules, since its movements are inhibited and its structure becomes abnormal in the presence of vincristin, an inhibitor of tubulin polymerization. Follicle-stimulating hormone (FSH) is an important regulator of Sertoli cell function. Since both basal and FSH-dependent cyclic AMP (cAMP) production by seminiferous tubules showed marked stage dependency, Sertoli cells are apparently influenced by spermatogenic cells. Thus, Sertoli cell function varies cyclically depending on the stage of the seminiferous epithelial cycle to provide an optimal microenvironment for spermatogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of Sertoli cell inhibin production and of inhibin alpha-subunit mRNA levels by specific germ cell types

To elucidate the endocrine and paracrine regulation of testicular inhibin production, the effects of follicle-stimulating hormone (FSH), (Bu)2cAMP, germ cells (either crude or enriched preparations) and germ cell-conditioned media on inhibin production (immuno- and bio-activities) and the levels of alpha- and beta B-subunit mRNAs were assessed in cultured Sertoli cells isolated from 20-day-old rats. FSH and (Bu)2-cAMP stimulated both secreted and intracellular inhibin levels in a dose-dependent manner. Using cDNA probes corresponding to the alpha-subunit and the beta B-subunit of rat inhibin it was also shown that both FSH and (Bu)2cAMP markedly increased the level of alpha-subunit mRNA but had no effect on the beta B-subunit mRNA. Addition of a crude mixture of germ cells to Sertoli cell monolayers was found to enhance inhibin secretion. Of the different germ cell fractions tested in co-culture, early spermatids reproducibly stimulated both basal and (Bu)2cAMP-induced production of inhibin whereas pachytene spermatocytes only increased the latter; cytoplasts from elongated spermatids (CES) had no effect. Co-culture of Sertoli cells with liver epithelial cells (LEC) significantly enhanced (Bu)2cAMP-induced inhibin levels. Media conditioned by early spermatids consistently and dramatically stimulated the secretion of both bioactive and immunoactive inhibin by Sertoli cells while spent media from pachytene spermatocytes displayed less activity. CES-conditioned media had only minor stimulatory effects, which may have resulted from the contamination of this fraction by spermatids. Media conditioned by LEC had no effect on inhibin production, confirming that the activity of this cell line is not mediated via a diffusible factor. Early spermatids were found to increase levels of the alpha-subunit mRNA. The current study provides evidence for the involvement of germ cells, in particular of early spermatids, in the local testicular regulation of inhibin gene expression and production in the rat. This may be of crucial importance for the ontogeny of this parameter of Sertoli cell function, and has important implications with regard to the postulated endocrine and paracrine roles of inhibin.

Cellular regulation of basal and FSH-stimulated cyclic AMP production in irradiated rat testes

Basal and follicle-stimulating hormone (FSH)-stimulated cyclic AMP (cAMP) productions by seminiferous tubular segments from irradiated adult rats were investigated at defined stages of the epithelial cycle when specific spermatogenic cells were low in number. Seven days post-irradiation, depletion of spermatogonia did not influence the basal cAMP production, but FSH response increased in stages II-VIII. Seventeen days post-irradiation when spermatocytes were low in number, there was a small increase in basal cAMP level in stages VII-VIII and FSH-stimulated cAMP production increased in stages VII-XII and XIII-I. At 38 days when pachytene spermatocytes and round spermatids (steps 1-6) were low in number, a decreased basal cAMP production was measured in stages II-VI and IX-XII. FSH-stimulated cAMP output increased in stages VII-XII but decreased in stages II-VI. At 52 days when all spermatids were low in number, basal cAMP levels decreased in all stages of the cycle, whereas FSH response was elevated only in stages VII-XII. All spermatogenic cell types seem to have an effect on cAMP production by the seminiferous tubule in a stage-specific fashion. Germ cells appear to regulate Sertoli cell FSH response in a paracrine way, and a part of cAMP may originate from spermatids stimulated by an unknown FSH-dependent Sertoli cell factor. The FSH-dependent functions may control such phenomena as spermatogonial proliferation, final maturation of spermatids, and onset of meiosis.

Possible role of elongated spermatids in control of stage-dependent changes in the diameter of the lumen of the rat seminiferous tubule

Adult male rats were treated with a single dose of 650 mg/kg methoxy acetic acid to deplete the seminiferous tubules specifically of pachytene and later spermatocytes. The effect of this treatment and the subsequent maturation-depletion of later germ cell types on the diameter of the seminiferous tubule and its lumen and the area of the seminiferous epithelium were studied in relation to the stages of the spermatogenic cycle. At 21 days after methoxy acetic acid treatment, the diameter of the tubule and the area of the epithelium were reduced below control values at all stages, consistent with the reduced number of early (stage VIII) or late (all other stages) spermatids. Unexpectedly, diameter of the lumen was also reduced at all stages other than VIII, and especially at stage VII. In controls, lumen diameter at stages VII and VIII was increased by approximately 50% compared with earlier and later stages. In rats treated 21 days previously with methoxy acetic acid no change occurred at stage VII (lacking elongated spermatids) while a normal increase did occur at stage VIII (lacking round but not elongated spermatids). At earlier times after methoxy acetic acid treatment when stage VII tubules were depleted of pachytene spermatocytes alone (3 days) or together with early spermatids (7 days), the diameter of the lumen was not significantly different from the control value. These data suggest that lumen diameter may be regulated by elongated spermatids, especially at stages VII and VIII.