Interleukin-1 is a potent growth factor for immature rat sertoli cells

Testes from rats of different maturational ages were explored for presence of paracrine sertoli cell growth factors. Pubertal and adult testes contained a 17 kDa protein, with potent stimulatory effect on immature Sertoli cell multiplication in vitro. The bioactivity of this protein was mimicked by rat interleukin-1 (IL-1) and neutralized by IL-1 receptor antagonist. A receptor-mediated action was further supported by the demonstration of IL-1 receptor type I mRNA and protein expression in the cultured sertoli cells and in intact immature rat testes. IL-1alpha showed higher efficacy in stimulating proliferation than IL-1beta and follicle-stimulating hormone (FSH), and displayed synergistic action in combination with FSH. As IL-1alpha is constitutively produced by the rat testis and IL-1beta readily inducible by proinflammatory stimuli, our results suggest that IL-1 may serve as a growth factor for Sertoli cells under physiological and pathophysiological conditions.

Transforming growth factor-alpha stimulates proliferation of rat Sertoli cells

The number of Sertoli cells is positively correlated with the number of germ cells produced in the testis, but the regulation of Sertoli cell proliferation and final density is poorly understood. Using non-aggregated Sertoli cells from 8 to 9-day-old rat testes, highly enriched by lectin binding, we explored effects of Sertoli cell growth factor candidates in vitro. Proliferation was assessed by 3H-thymidine incorporation, bromodeoxyuridine labeling and supravital staining, and FSH was used as positive control. Transforming growth factor-alpha (TGF-alpha) was found to stimulate Sertoli cell proliferation in a dose-dependent manner. Epidermal growth factor (EGF) and betacellulin mimicked the effect, demonstrating specificity of the response as they share receptors with TGF-alpha. Insulin-like growth factor I and II, acidic and basic fibroblast growth factor and stem cell factor lacked significant stimulatory effects. We conclude that EGF/TGF-alpha is a growth factor for Sertoli cells in vitro, possibly contributing to paracrine regulation of Sertoli cell proliferation in vivo.

Production of interleukins 1beta, 6 and 8 and tumor necrosis factor alpha in separated and cultured endometrial and endometriotic stromal and epithelial cells

The production of IL-1beta, IL-6, IL-8 and TNF-alpha was studied in short-time culture of separated stromal and epithelial cells. The cytokine secretion into culture medium was analyzed using immunoassay to evaluate the cytokine protein levels and bioassay to assess the bioactivity of the cytokines. Tissue samples of endometrium and ovarian endometriomas were obtained from 4 patients operated on for clinical reasons. Only IL-8 was found in all samples. IL-1beta and TNF-alpha were detected in the culture medium from most stromal cell samples, but in fewer media from epithelial cell samples. IL-6 was measurable in a few medium samples. Few of the samples displayed a bioactivity. There was no obvious difference between endometrium and endometriotic cell samples besides the production of IL-8 that seems to be lower in endometriotic tissue.

Elevated expression of tumour necrosis factor alpha in cultured granulosa cells from women with endometriosis

Fertilization and oocyte cleavage rates have previously been demonstrated to be lower for women with endometriosis undergoing IVF compared with controls. This might be related to impaired oocyte function, possibly due to an inflammatory milieu in the pelvis of these women, where an elevated concentration of many cytokines is documented. The aim of this study was to examine whether granulosa cells from women with endometriosis deviated with respect to production of the inflammatory cytokines interleukin-1beta, interleukin-6, interleukin-8 and tumour necrosis factor alpha (TNFalpha) compared with granulosa cells from healthy women, undergoing IVF for male infertility. The effect of human chorionic gonadotrophin on cytokine production was also investigated. Granulosa cells in follicular fluid were obtained at oocyte retrieval for IVF. Incubated cell culture media were analysed by enzyme-linked immunosorbent assay. The basal production of all four cytokines was higher in cells from women with endometriosis when compared to controls, although the increase was only significant for TNFalpha. Chorionic gonadotrophin had no significant effect, although it had a tendency to suppress cytokine release in both patient categories. Whether aberrant cytokine production in granulosa cells from women with endometriosis may disturb fertilizing capacity of oocytes requires study.

A rapid method of Sertoli cell isolation by DSA lectin, allowing mitotic analyses

We have developed a rapid and convenient method of Sertoli cell preparation for studying the growth kinetics of these cells in in vitro culture. Datura Stramonium agglutinin (DSA)-coated dishes were used to rapidly purify single Sertoli cells from immature rat testis. We have monitored by immunohistochemical markers the degree of contamination of our Sertoli cell preparation by other cell types. The cell preparation is essentially free of germ cells and interstitial cells and contains a minimal percentage of myoid cells. Sertoli cells isolated with this method retain functional activities such as the FSH responsiveness in terms of cAMP production. In addition, we have studied the proliferative activity of Sertoli cells isolated by lectin binding from rats of different ages. Sertoli cells exhibited a characteristic pattern of proliferation which was a function of the donor animal age. The proliferative activity of isolated Sertoli cells decreased with age, being much higher in 3 day-old rats than in older animals. A similar pattern was observed when the mitotic activity of Sertoli cells in response to mitogens present in the testicular extracts from 5 day-old rats was evaluated. The method described here reduces or eliminates many of the drawbacks of the conventional procedures used to isolate Sertoli cells, thus providing a useful tool in studies of growth kinetics and regulation of cell proliferation in vitro.

Interleukin-1 bioactivity and DNA synthesis in X-irradiated rat testes

Stage-specific DNA synthesis and interleukin-1 (IL-1) bioactivity were measured in the rat testis at 2, 6, 12 and 25 days after local irradiation with 3 Gy to investigate whether there was any correlation between germ cell DNA synthesis during repopulation and IL-1-like bioactivity in the seminiferous epithelium. DNA synthesis by intermediate and type-B spermatogonia was reduced significantly at 2, 6 and 12 days after irradiation in seminiferous tubules at stages II-III and IV-V. IL-1 bioactivity was increased significantly at 6 and 25 days after irradiation at stages II-VI during repopulation of spermatogonia. At 2, 6 and 25 days after irradiation at stages VIIa-c a significant increase in IL-1 bioactivity was observed that correlated with repair synthesis of DNA. Increased IL-1 bioactivity was also observed at stages IX-XII at 6 days post-irradiation. These observations support the concept that IL-1 is a spermatogonial growth factor which might also stimulate repair synthesis of DNA.

Hormonal and photoperiod-induced changes in testicular interleukin-1-like factor in bank voles, Clethrionomys glareolus

Testicular interleukin-1-like factor (tIL-1) is a cytokine secreted presumably by Sertoli cells in several mammalian species. The function of this cytokine is unknown: tIL-1 may control meiosis, act as a mitogen for spermatogonia or have both of these functions. The present investigation was conducted to assess tIL-1 activity and its hormonal control in a seasonally breeding photoperiodic mammal during testicular maturation and photoperiod-induced regression. Testicular maturation in long photoperiod (20 h light:4 h dark) was accompanied by the appearance of tIL-1 activity at the age of 32-39 days which increased as full sexual maturity was reached. No significant tIL-1 activity was detected when pubertal development was inhibited or testicular regression induced by subjecting juvenile and adult bank voles to a short photoperiod (6 h light: 18 h dark) for 6 to 8 weeks. Administration of human chorionic gonadotrophin (hCG; 60 IU kg-1) increased tIL-1 activity in sexually mature as well as regressed testes. In the photoregressed voles FSH (1.2 U kg-1) administration, which induced a three-fold increase in testicular weight and stimulated spermatogenesis, did not induce detectable concentrations of tIL-1. Administration of FSH followed by hCG increased tIL-1 activity significantly in the atrophic testis, but this was probably due to hCG, since FSH treatment alone was without effect. In conclusion, in accordance with the proposed role of tIL-1 as a germ-cell mitogen and a meiosis-promoting factor, tIL-1 activity correlated positively with spermatogenic activity during testicular maturation and photoperiod-induced regression.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine responsiveness in germfree and conventional NMRI mice

We have investigated the proliferative response of thymocytes from different mouse strains to cytokines in vitro. Interleukin 2 (IL-2), IL-4 and IL-7 induced proliferation of thymocytes from NMRI/KI (a locally bred NMRI mouse strain), NMRI/H ('traditional' NMRI mice), C3H/HeJ and C3H/HeN mice. NMRI/KI thymocytes showed the most prominent proliferation in response to IL-1 alpha and IL-1 beta. IL-3, IL-5, IL-6, IL-8, IL-10, tumour necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma), inhibin and lipopolysaccharide (LPS) induced no thymocyte proliferation. Germfree NMRI/KI mouse thymocytes showed a significantly lower proliferation in response to IL-1 alpha and IL-1 beta than conventional mice. Rat tissues, previously shown to contain lymphocyte activating factors (LAFs), were also tested. Skin, tongue, esophagus, proventricular stomach, testis and placenta were all positive in the LAF assay utilizing NMRI/KI thymocytes, whereas none of the tissue extracts could induce proliferation in NMRI/H thymocytes. The higher cytokine responsiveness in conventional mice compared with germfree might suggest that exposure to microflora induces a higher state of activation of the immune system. The LAF assay, utilizing NMRI/KI thymocytes, is a highly sensitive IL-1 bioassay with a detection level of 1 pg/ml for IL-1 beta and 2 pg/ml for IL-1 alpha. The specificity of the assay is increased by utilizing NMRI/H mice to exclude the presence of IL-2, IL-4 and IL-7.

Ontogeny of lymphocyte activating factors in conventional and germfree rats

Immune regulatory cytokines have previously been demonstrated outside the immune system in, e.g., the skin, testis, and brain, and suggested to serve as barrier site defence mediators. We have recently demonstrated constitutive production of an interleukin-1 (IL-1)-like factor(s) in the proximal gastrointestinal tract, liver, and placenta of adult rats. In the present study we have investigated the developmental production of IL-1-like factors in these tissues in conventional rats and in rats raised under germfree conditions. Slight IL-1 bioactivity was detected at a gestational age of 18 days in the skin and esophagus, and on day 19 significant amounts were detected in the skin, tongue, esophagus, and stomach. The activity was maximal at gestational day 20-21, and stationary at all later time-points. The placenta and liver contained high amounts of IL-1 activity throughout fetal life. The brain showed a transient appearance of IL-1 bioactivity at a gestational age of 19-21 days, but no activity at later time-points. Germfree rats showed no significant difference in the ontogeny or amounts of IL-1 bioactivity compared to conventional rats. It can be concluded that the IL-1 bioactivity appears at a definite time point in all measured tissues in fetal life and that exposure to microbial antigens does not seem to influence its production. As the investigated tissues show a high proliferation rate, it is tempting to suggest that the detected IL-1 (-like factors) might have an alternate function in these tissues, e.g., to serve as growth factors.

In vitro stimulation of stage-specific deoxyribonucleic acid synthesis in rat seminiferous tubule segments by interleukin-1 alpha

Levels of rat testicular interleukin-1-like factor (tIL-1) have been shown to correlate with DNA synthetic activity during the cycle of the rat seminiferous epithelium, suggesting its role as a spermatogonial or meiotic growth factor. To explore this further, a new in vitro model system was developed. Rat seminiferous tubule segments from stages I, V, VIIa, and VIII-IX of the cycle were isolated by transillumination-assisted microdissection, cultured in chemically defined serum-free medium supplemented with human recombinant IL-1 alpha, and labeled with [3H]thymidine. During incubation, spontaneous progression of spermatogenesis was noted. Inactive stage VIIa tubule segments differentiated to stage VIII and initiated DNA synthesis, and concomitantly started to secrete IL-1-like factor. DNA synthesis of stages VIII-IX ceased through differentiation of spermatocytes to leptotene-zygotene (stages XII-XIII of the cycle). IL-1 alpha stimulated DNA synthesis significantly in spermatogonia of stage I. Meiotic DNA synthesis at stage VIIa was stimulated (48 h/34 C) and maintained at stages VIII-IX (48 h/34 C). IL-1 alpha seems to act as a regulator of spermatogenic DNA synthesis in both mitotic and meiotic phases. It has mainly stimulating and maintaining effects, but it may also be inhibitory under certain conditions.

Production and secretion of an interleukin-1-like factor is stage-dependent and correlates with spermatogonial DNA synthesis in the rat seminiferous epithelium

It has been shown previously that the intact adult rat testis produces large amounts of an interleukin-1 (IL-1)-like growth factor. The present study has investigated whether this testicular IL-1-like factor (tIL-1) is produced and secreted differentially by the fourteen stages of the seminiferous epithelial cycle in the rat testis. Seminiferous tubule segments representing defined stages were identified by transillumination-assisted microscopy and isolated by microdissection. Pooled segments were either homogenized and extracted with aqueous buffer or incubated for 24 h to produce conditioned media (CM). The recovered material was then analysed for IL-1 bioactivity in a sensitive murine thymocyte proliferation assay. When divided into four stage groups, extracts of stages II-VI, IX-XII and XIII-I showed equally high IL-1 activity whereas stage group VII-VIII showed much lower activity. More detailed analysis with 10 different stage groups showed that tIL-1 activity was undetectable in extracts of substages VIIab and VIIcd. The same pattern was seen when CM from cultured tubular segments were analysed. Labelling of seminiferous tubules with tritiated thymidine in vitro and analysis by autoradiography revealed that DNA-synthesizing spermatogonia were absent in substages VIIb and VIIc and sparse in substages VIIa and VIId. The results show that tIL-1 activity is produced in a stage-dependent manner and suggest that tIL-1 might be involved in the regulation of spermatogonial proliferation in vivo.

Peptides of postulated inhibin activity. Lack of in vitro inhibin activity of a 94-residue peptide isolated from human seminal plasma, and of a synthetic replicate of its C-terminal 28-residue segment

A 94-residue polypeptide isolated from human seminal plasma and its chemically synthesized C-terminal 28-residue segment were studied in an in vitro inhibin bioassay utilizing rat pituitary cell cultures. Both peptides have previously been claimed to have inhibin activities, and the effects on the secretion and cellular content of gonadotrophins (FSH and LH) were now assessed in the in vitro assay. No inhibition was found. After 72 h of culture, both the cellular content and the spontaneous as well as the LHRH-stimulated release of bioactive or immunoactive FSH and LH remained unaffected. Similarly, no effects were found on the storage and/or release of prolactin, growth hormone, or thyrotropin. We conclude that both the native 94-residue peptide and the synthetic replicate of its C-terminal 28-residue segment, do not influence the pituitary FSH secretion when assessed in this in vitro system.

Biological and immunological properties of different molecular species of human follicle-stimulating hormone: electrofocusing profiles of eight highly purified preparations

Eight highly purified human pituitary FSH preparations and purified preparations of the α-and β-subunits of FSH were fractionated by an electrofocusing technique in the pH range of 2·5–10·0 on a sucrose density gradient. The human (h) FSH activity in each of the eluted fractions was monitored by an in-vitro bioassay and a radioimmunoassay procedure.

After electrofocusing, the overall recovery of the biological activity of the eight preparations was between 80 and 94% (mean 88%). On the other hand, the recovery of immunoreactivity ranged between 30 and 84% (mean 71%). A loss of over 85% of hFSH immunoreactivity was observed when the α- and β-subunits of hFSH were fractionated by the same procedure.

The specific loss of varying amounts of immunoreactivity in all preparations during electrofocusing was also reflected by a proportional increase in the ratios of biological activity (B) to immunoreactivity (I); preparation A, which exhibited a loss of 70% of the immunoreactivity, had a threefold increase in its B/I ratio after electrofocusing.

Significant differences were observed in the electrofocusing profiles of the eight preparations both in terms of their pI values and of their spread.

The disparity in the relative distribution of hFSH activities in different pH regions suggested major differences in the carbohydrate moieties (sialic acid content) of the preparations studied, probably as a result of the chemical manipulations involved in the purification of the hormone. It is suggested that a combination of several (but certainly not all) of the preparations might serve as a provisional International Reference Preparation for hFSH radioimmunoassays.

Improved in vitro bioassay of follitropin

The FSH-dependent aromatase activity of Sertoli cell enriched cultures of testicular cells from immature rats was utilized as a sensitive and specific in vitro bioassay for FSH activity. The conversion of 19-hydroxyandrostenedione to estradiol was used as the end point of the assay. By the introduction of a phosphodiesterase inhibitor into the culture medium, the sensitivity was improved 5-10 times, so that 0.05 mIU of FSH showed a response significantly different from the blank. Other pituitary or placental hormones, such as hLH, hTSH and hCG exhibited less than 0.8% cross-reactivity, whereas hGH, hPRL, ACTH1-24, LH-RH, and prostaglandin E2 alpha did not show any cross-reaction at the doses tested.

A comparison of preparations of highly purified human pituitary follicle-stimulating hormone: differences in the follicle-stimulating hormone potencies as determined by in-vivo bioassay, in-vitro bioassay and immunoassay

The FSH potencies of 12 preparations of highly purified human pituitary FSH, originating from six different laboratories, were determined by in-vivo and in-vitro bioassays and by immunoassay in terms of the First International Reference Preparation of Human Pituitary Gonadotrophins (FSH and LH) for Bioassay (IRP; coded 69/104). The contamination of these FSH preparations with LH was also determined. Estimates of protein content were based on the absorbance at 280 nm of solutions of the preparations, assuming that A1%1 cm 280 = 10.

The FSH potencies varied between different preparations from 827 i.u./mg to 13 100 i.u./mg by in-vivo bioassay; from 2930 to 14 600 i.u./mg by in-vitro bioassay and from 1680 to 5690 i.u./mg by immunoassay. The ratios of in-vivo biological activity relative to in-vitro biological activity and to immunoreactivity respectively varied between preparations from 0·06 to 2·3 and from 0·15 to 4·1, and there was a significant positive correlation between each of these ratios and the in-vivo biological potency of the preparations; such differences could be due to varying degrees of sialylation between preparations. On the other hand the ratios of in-vitro biological activity to immunoreactivity between preparations were fairly constant (approx. 2). The excess biological activity relative to immunoreactivity observed, in terms of the IRP, in all these materials is consistent with recent findings of some immunoreactive FSH in the IRP unassociated with biological activity. These data did not demonstrate any significant advantage, in terms of FSH in-vivo biological potency, from the use of fresh-frozen rather than acetone-dried pituitary glands for the isolation of FSH.

Contamination of all these preparations with LH appeared to be less than 3% (w/w), as determined by in-vitro bioassay and by immunoassay.

The results of this study are discussed in relation to the selection of material for an international reference preparation for immunoassay and attention is drawn to the value of high in-vivo biological FSH potency as a criterion of the identity of a preparation as well as of its freedom from contaminants without FSH biological activity.

Effect of storage on the bioactivity of two international reference preparations of human pituitary luteinizing hormone in vitro

There was no loss of biological activity in vitro when the 1st International Reference Preparation (IRP) for human pituitary gonadotrophins [FSH and LH/interstitial cell stimulating hormone (ICSH) for bioassay] code no. 69/104 and the 1st IRP for human pituitary LH/ICSH [for immunoassay] code no. 68/40 were stored for 1 year at -70 degrees C in a buffered 0.8% saline solution containing 1% bovine plasma albumin (BPA). However, storage of the 69/104 preparation at -20 degrees C in either 0.1 or 1% BPA, or at -70 degrees C in the presence of 0.1% BPA showed a small but significant decrease (approximately 10%) in activity over the same period. It is, therefore, advantageous to store these reference preparations at -70 degrees C in the presence of 1% BPA.

Biological and immunological characterization of human luteinizing hormone: IV. Biological and immunological profile of two international reference preparations after electrofocusing

The first IRP of Human Pituitary Gonadotrophins (FSH/LH) for bioassay (69/104) and the 1st IRP of Human Pituitary Luteinizing Hormone (LH) for immunoassay (68/40) were fractionated by an electrofocusing technique in a sucrose density gradient and the profile of biological and immunological activities was determined. The partially purified LH preparation (69/104) gave a broad pattern of biolgical and immunological activities which extended from pH 4 to 10. The biological : immunological (B/I) ratio of the various fractions (using the 68/40 preparation as standard) ranged from 0.04 to 1.05. The low B/I ratios indicate the presence of high levels of immunologically active, biologically inactive material in this preparation. In contrast to the behaviour of the 69/104 preparation, the major proportion (88%) of the biological activity recovered after electrofocusing of the highly purified LH preparation (68/40) was found within the pH range 7--9, with B/I ratios (again using as standard the 68/40 preparation) ranging from 0.4 to 1.5. Multiple dose parallel line design radioimmunoassays revealed a lack of parallelism between the 69/104 and 68/40 International Reference Preparations. This was attributed to the presence of acidic material in the former preparation, which is practically absent from the latter. The biological LH profiles of both the 69/104 and 68/40 preparations differed from those previously reported for aqueous extracts of pituitaries. It is concluded that the dissimilarity in the electrofocusing profiles of the biological and immunological activities of the 69/104 preparation renders this preparation unsuitable as a reference preparation for the quantitation of biologically active LH by radioimmunoassay methods. Using the same criteria, the 68/40 preparation would appear to be a more suitable standard.