Effect of growth hormone and induced IGF-I release on germ cell population and apoptosis in the bovine testis

Congenital combined pituitary hormone deficiency patients have better responses to gonadotrophin-induced spermatogenesis than idiopathic hypogonadotropic hypogonadism patients

STUDY QUESTION

Do patients with congenital combined pituitary hormone deficiency (CCPHD) have different responses to gonadotrophin-induced spermatogenesis compared with those with idiopathic hypogonadotropic hypogonadism (IHH)?

SUMMARY ANSWER

CCPHD patients have a better response to gonadotrophin therapy than IHH patients.

WHAT IS KNOWN ALREADY

Gonadotrophins are effective in inducing spermatogenesis in patients with hypogonadotropic hypogonadism.

DESIGN, SIZE AND DURATION

This retrospective cohort study included 75 patients, 53 of whom had IHH and 22 CCPHD. They were diagnosed, treated and followed up between January 2008 and December 2013.

PARTICIPANTS/MATERIALS, SETTING AND METHODS

Combined gonadotrophin therapy, consisting of human chorionic gonadotrophin and human menopausal gonadotrophin, was administered for 24 months. The success rate of spermatogenesis (≥1 sperm in ejaculate), serum total testosterone level, testicle size and sperm concentration during the treatment, as well as the first time sperm were detected in the ejaculate, were compared between the two diagnostic groups. All patients were treated in Peking Union Medical College Hospital.

MAIN RESULTS AND THE ROLE OF CHANCE

Spermatogenesis was successfully induced in 85% of IHH patients and 100% of CCPHD patients after 24-month combined gonadotrophin treatment (P = 0.03). In comparison with IHH, CCPHD patients had larger mean testicle sizes during the gonadotrophin treatment at 6, 12, 18 and 24 months (all P < 0.05). The initial time for sperm appearance in IHH group (n = 45) and CCPHD group (n = 22) was 13.2 ± 5.9 versus 10.4 ± 3.8 months (P = 0.045). Generally, CCPHD patients had higher sperm counts [median (quartiles)] than IHH patients during the treatment, but the difference was only statistically significant at 12 months of treatment, 3.3 (1.8, 12.0) versus 1.0 (0.0, 4.6) million/ml, P = 0.001. There was a higher level of serum total testosterone [mean (SD)] in the CCPHD group than the IHH group (676 ± 245 versus 555 ± 209 ng/dl, P = 0.035).

LIMITATIONS, REASONS FOR CAUTION

First, the inherent nature of a retrospective designed study was a main shortcoming. Secondly, pathological gene mutations in IHH and CCPHD patients should be further investigated. Clarification of the underlying mechanisms between cryptorchidism and mutated genes may provide more information for the divergent therapeutic responses between two groups. Only a minority of patients were actively seeking to have children so information about fertility is limited.

WIDER IMPLICATIONS OF THE FINDINGS

CCPHD patients had a lower incidence of cryptorchidism and a better response to gonadotrophin therapy than IHH patients, reflecting multiple defects on the different levels of reproduction axis in IHH. Furthermore, growth hormone is not indispensable for spermatogenesis in CCPHD patients.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by Natural Science Foundation of China (No: 81100416). None of the authors has any conflicts of interest to declare.

Roles of small RNAs in the effects of nutrition on apoptosis and spermatogenesis in the adult testis

We tested whether reductions in spermatozoal quality induced by under-nutrition are associated with increased germ cell apoptosis and disrupted spermatogenesis, and whether these effects are mediated by small RNAs. Groups of 8 male sheep were fed for a 10% increase or 10% decrease in body mass over 65 days. Underfeeding increased the number of apoptotic germ cells (P < 0.05) and increased the expression of apoptosis-related genes (P < 0.05) in testicular tissue. We identified 44 miRNAs and 35 putative piRNAs that were differentially expressed in well-fed and underfed males (FDR < 0.05). Some were related to reproductive system development, apoptosis (miRNAs), and sperm production and quality (piRNAs). Novel-miR-144 (miR-98), was found to target three apoptotic genes (TP53, CASP3, FASL). The proportion of miRNAs as a total of small RNAs was greater in well-fed males than in underfed males (P < 0.05) and was correlated (r = 0.8, P < 0.05) with the proportion of piRNAs in well-fed and underfed males. In conclusion, the reductions in spermatozoal quality induced by under-nutrition are caused, at least partly, by disruptions to Sertoli cell function and increased germ cell apoptosis, mediated by changes in the expression of miRNAs and piRNAs.

Influência do Hormônio do Crescimento na concentração de testosterona plasmática e nas características seminais de touros jovens e adultos da raça Nelore

Estudou-se o efeito do Hormônio do Crescimento bovino (bGH) sobre os parâmetros seminais e a concentração sérica de testosterona de touros da raça Nelore. Dezesseis touros foram distribuídos em um delineamento fatorial 2 x 2 (duas idades e dois níveis de r-bST), com quatro animais em cada tratamento. As aplicações de r-bST foram realizadas a cada 14 dias, totalizando nove aplicações por animal, em um período experimental de 120 dias. As coletas de sêmen foram realizadas a cada 15 dias e, para determinar as concentrações de testosterona, foram realizadas coletas de sangue a cada quatro horas, num total de 24 horas, e a cada 30 dias a partir da primeira aplicação de r-bST. O sêmen dos touros adultos tratados com r-bST apresentaram maior motilidade e vigor (P<0,05) em relação aos animais controles (79,70±11,56% vs 64,06±23,65%) e (3,80±0,88 vs 2,92±1,25), respectivamente; entretanto, as demais características seminais não foram influenciadas (P>0,05) pelo tratamento com r-bST. Os aspectos físicos do sêmen dos touros jovens não foram afetados (P>0,05) pelo tratamento com r-bST. Entretanto o tratamento com r-bST diminuiu os defeitos morfológicos menores (delgado, gigante normal, pequeno normal, globoso, cabeça isolada normal, abaxial, cauda dobrada e enrolada levemente e gota distal) em relação aos jovens não tratados (P<0,05). As concentrações séricas de testosterona foram influenciadas (P<0,05) pelo tratamento, aos 120 dias após a primeira aplicação do r-bST, e apresentaram tendência de três picos no período de 24 horas.

Growth hormone and reproduction: a review of endocrine and autocrine/paracrine interactions

The somatotropic axis, consisting of growth hormone (GH), hepatic insulin-like growth factor I (IGF-I), and assorted releasing factors, regulates growth and body composition. Axiomatically, since optimal body composition enhances reproductive function, general somatic actions of GH modulate reproductive function. A growing body of evidence supports the hypothesis that GH also modulates reproduction directly, exerting both gonadotropin-dependent and gonadotropin-independent actions in both males and females. Moreover, recent studies indicate GH produced within reproductive tissues differs from pituitary GH in terms of secretion and action. Accordingly, GH is increasingly used as a fertility adjunct in males and females, both humans and nonhumans. This review reconsiders reproductive actions of GH in vertebrates in respect to these new conceptual developments.

Extrapituitary growth hormone in the chicken reproductive system

Increasing evidence shows that growth hormone (GH) expression is not limited to the pituitary, as it can be produced in many other tissues. It is known that growth hormone (GH) plays a role in the control of reproductive tract development. Acting as an endocrine, paracrine and/or autocrine regulator, GH influences proliferation, differentiation and function of reproductive tissues. In this review we substantiate the local expression of GH mRNA and GH protein, as well as the GH receptor (GHR) in both male and female reproductive tract, mainly in the chicken. Locally expressed GH was found to be heterogeneous, with a 17 kDa variant being predominant. GH secretagogues, such as GHRH and TRH co-localize with GH expression in the chicken testis and induce GH release. In the ovarian follicular granulosa cells, GH and GHR are co-expressed and stimulate progesterone production, which was neutralized by a specific GH antibody. Both testicular and follicular cells in primary cultures were able to synthesize and release GH to the culture medium. We also characterized GH and GH mRNA expression in the hen's oviduct and showed that it had 99.6% sequence identity with pituitary GH. Data suggest local reproductive GH may have important autocrine/paracrine effects.

Efficiency of the spermatogenesis in zebu bulls (Bos taurus indicus)

The objective of the research was to evaluate the efficiency of the spermatogenesis through the morphology of the testicular parenchyma in bulls of different zebu breeds. We used testicular fragments from bull of the breeds Nelore (n = 10), Polled Nelore (n = 6), Gyr (n = 5), Guzerat (n = 5) and Tabapuã (n = 5). The tissue was perfused with Karnovsky solution, included in glycol methacrylate and stained with toluidine blue-sodium borate 1%. Animals of the Nelore breed presented higher population of primary spermatocyte in pre-leptotene/leptotene (38.30) and in pachytene (38.14) and round spermatids (113.30), higher yield of spermatogonia mitosis (21.2) and higher daily spermatic production per gram of testicular parenchyma (32.8 × 10(6) ) than those from breeds Gyr, Guzerat and Tabapuã and higher general yield of spermatogenesis (62.4) than breeds Gyr and Tabapuã. There was no significant difference in any of the evaluated parameters between breeds Nelore and Polled Nelore. The rate of Sertoli cells did not vary between the studied breeds. Apparently, the genetic selection applied to the breeds has been improving the yield in the spermatogenic process by decreasing cellular loss, although it did not increase the support capacity of the Sertoli cells.

Modification of spermatozoa quality in mature small ruminants

This review is based largely, but not entirely, on the assumption that gamete quality is directly linked to sperm output and thus testicular mass, an approach made necessary by the absence of a large body of data on factors that affect gamete quality in ruminants. On the other hand, there is a change in the efficiency of sperm production per gram of testicular tissue when the testis is growing or shrinking, a clear indicator of changes in the rates of cell loss during the process of spermatogenesis, probably through apoptosis. We therefore postulate that the spermatozoa that do survive when the testis is shrinking are of a lower quality than those that are produced when the testis is growing and the rate of sperm survival is increasing. In adult small ruminants in particular, testicular mass and sperm production are highly labile and can be manipulated by management of photoperiod (melatonin), nutrition, genetics and behaviour (‘mating pressure’). Importantly, these factors do not act independently of each other – rather, the outcomes in terms of sperm production are dictated by interactions. It therefore seems likely that spermatozoa quality will be affected by these same factors, but definitive answers await detailed studies.

Modulation of the apoptotic pathway in skeletal muscle models: the role of growth hormone

Despite numerous studies on the role of growth hormone (GH), its function in skeletal muscle apoptosis secondary to various stimuli is poorly understood. In this study, we used rodent muscle cell lines to analyse cell growth and survival as well as the morphological and molecular markers of cell death in C2C12 and L6C5 myoblasts. These cells were treated either in the presence or absence of GH under serum starvation conditions or in the pro-apoptotic concentrations of hydrogen peroxide (H2O2). Although the cells were responsive to the presence of GH, we did not observe GH modulation of cell growth and survival. The presence of GH did not affect the cell death programme or the expression of apoptotic markers in basal conditions or under oxidative stress. In conclusion, this study indicated that GH "by itself" is not effective in modulating the intracellular pathways leading to cell survival or cell death induced by apoptotic stimuli.

Insulin-like growth factor-I (IGF-I) protects cultured equine Leydig cells from undergoing apoptosis

Leydig cells located in the interstitial space of the testicular parenchyma produce testosterone which plays a critical role in the maintenance and restoration of spermatogenesis in many species, including horses. For normal spermatogenesis, maintaining Leydig cells is critical to provide an optimal and constant level of testosterone. Recently, an anti-apoptotic effect of IGF-I in testicular cells in rats has been reported, but a similar effect of IGF-I on equine Leydig cells remains to be elucidated. If IGF-I also protects stallion testicular cells from undergoing apoptosis, then IGF-I may have potential as a treatment regime to prevent testicular degeneration. The present study was designed to evaluate the anti-apoptotic effect of IGF-I on cultured equine Leydig cells. Testes were collected from 5 post-pubertal stallions (2-4 years old) during routine castrations. A highly purified preparation of equine Leydig cells was obtained from a discontinuous Percoll gradient. Purity of equine Leydig cells was assessed using histochemical 3β-HSD staining. Equine Leydig cells and selected doses of recombinant human IGF-1 (rhIGF-I; Parlow A.F., National Hormone and Peptide Program, Harbor-UCLA Medical Center) were added to wells of 24 or 96 well culture plates in triplicate and cultured for 24 or 48 h under 95% air:5% CO(2) at 34°C. After 24 or 48 h incubation, apoptotic rate was assessed using a Cell Death Detection ELISA kit. Significantly lower apoptotic rates were observed in equine Leydig cells cultured with 5, 10, or 50ng/ml of rhIGF-I compared with control cells cultured without rhIGF-I for 24h. Exposure to 1, 5, 10 or 50 ng/ml of rhIGF-I significantly decreased apoptotic rate in equine Leydig cells cultured for 48 h. After 48 h incubation, cells were labeled with Annexin V and propodium iodine to determine the populations of healthy, apoptotic, and necrotic cells by counting stained cells using a Nikon Eclipse inverted fluorescence microscope. As a percentage of the total cells counted, significantly lower numbers of apoptotic cells were observed in cells treated with 10 (9%) or 50 ng/ml (10%) of rhIGF-I compared with cells cultured without rhIGF-I (control, 22%). In this study, the results from the two assays indicated that rhIGF-I protected equine Leydig cells from undergoing apoptosis during cell culture for 24h or 48 h. In conclusion, IGF-I may be an important paracrine/autocrine factor in protecting equine Leydig cells from undergoing apoptosis.

Effect of recombinant bovine somatotropin on plasma concentrations of insulin-like growth factor I, insulin and membrane integrity of bull spermatozoa

This study aimed to evaluate the effect of the exogenous recombinant bovine somatotropin (rbST) on plasma concentrations of insulin-like growth factor I (IGF-I), insulin and semen quality of bulls. Twenty bulls (Aberdeen Angus and Brangus) were divided by breed into two groups. Placebo group was injected with NaCl 0.9% (s.c.) and treatment group with rbST (s.c., 500 mg) at days 0 and 14 of the experiment. Immediately after semen collection, blood samples were taken on days 0, 14, 28, 42 and 56 of the experiment. Semen was also collected on day 70 of the experiment. Evaluation of sperm motility was performed at pre-freezing and post-thawing stage, whereas assessment of sperm membrane integrity was performed after freezing and thawing. Analysis of data revealed that the effect of treatment and treatment-by-collection day on plasma concentrations of IGF-I and insulin was not significant. However, mean plasma concentrations of IGF-I and insulin were affected (p < 0.0001) by days of blood sampling. Effect of treatment and treatment-by-collection day on motility of spermatozoa was similar (p > 0.05) at pre-freezing and post-thawing stage. Intactness of plasmalemma and tail membrane of spermatozoa at post-thawing stage was higher (p < 0.05) in rbST-treated group than in control. In conclusion, rbST did not affect plasma concentrations of IGF-I and insulin, however, it did improve post-thaw sperm membrane integrity.

Control of reproductive processes by growth hormone: extra- and intracellular mechanisms

Recent data on the association between growth hormone (GH) and male and female reproductive processes, as well as the effects of GH on these processes and on some reproductive and non-reproductive disorders, and possible extra- and intracellular mediators of its action are reviewed. The available data suggest that GH is an important endocrine and autocrine/paracrine regulator of reproduction. It controls proliferation, apoptosis, growth and differentiation and the secretory and generative activities of different reproductive organs. It also regulates their response to gonadotrophin-releasing hormone (GnRH) and gonadotropins. Despite the effects of GH on the IGF/IGFBP (insulin-like growth factor binding protein) system, oxytocin, steroids, activin, gonadotropin and gonadotropin receptors, the majority of GH's actions on the reproductive processes are probably mediated not by these substances but by specific GH receptors acting through cAMP/protein kinase A, protein kinase G, tyrosine kinase-, MAP kinase and CDC2 kinase-dependent intracellular mechanisms. Although GH treatments can increase the risk of some reproductive and non-reproductive disorders, they may be useful in improving gonadal function, inducing superovulation and in embryo production.

Transgene transmission to progeny by oMt1a-oGH transgenic mice

Most studies utilizing transgenic technology focus on the impact to traits of interest, rather than propagation of the transgene to offspring. In animals containing growth hormone constructs, transgene transmission to progeny follows a Mendelian pattern of inheritance in the first few generations following generation of a founder animal, but decreases in subsequent generations. In the present study, the ovine metallothionein 1a-ovine growth hormone (oMt1a-oGH) transgenic mouse was used to determine whether transgene transmission rate to progeny was affected by overexpression of ovine growth hormone in the transgenic parent. The oMt1a-oGH mouse is a useful model for assessing transgene transmission, as the construct is easily regulatable and transgene inactivation results in a return of plasma GH to basal levels. Male and female hemizygous oMt1a-oGH mice were assigned to 1 of 3 treatment groups: (1) mice never actively expressing the transgene, (2) mice actively expressing the transgene from 3 weeks of age, and (3) mice actively expressing the transgene from 3 to 11 (males) or 3 to 8 (females) weeks of age. Transgenic mice were mated to wild type animals and the resulting progeny were genotyped. Males never actively expressing the transgene passed on the transgene to progeny in a Mendelian fashion, while males actively expressing the transgene transmitted the transgene to a smaller than expected number of progeny. However, following inactivation of the oMt1a-oGH construct in transgenic males, subsequent offspring demonstrated Mendelian inheritance of the transgene. In contrast, females expressing the transgene from 3 to 8 weeks of age were able to pass on the oMt1a-oGH construct in a Mendelian fashion, but females from other treatment groups were not. In oMt1a-oGH males, reduced transgene transmission appears to be due to selection against transgenic gametes. In females, however, selection against the transgenic genotype likely occurs at the embryonic level.

Germ cell apoptosis in the testes of normal stallions

Apoptosis in testicular germ cells has been demonstrated in many mammalian species. However, little is known about the stallion (Equus caballus) and rates of apoptosis during spermatogenesis. Morphological and biochemical features of apoptosis reported in other species were used to confirm that the TdT-mediated dUTP Nick end labeling (TUNEL) assay is an acceptable method for identification and quantification of apoptotic germ cells in histological tissue sections from stallion testis. Seminiferous tubules from eight stallions with normal testis size and semen quality were evaluated according to stage of seminiferous epithelium to determine the germ cell types and stages where apoptosis most commonly occurs. Spermatogonia and spermatocytes were the most common germ cell types labeled by the TUNEL assay. A low rate of round and elongated spermatids were labeled by the TUNEL assay. Mean numbers of TUNEL-positive germ cells per 100 Sertoli cell nuclei were highest in stages IV (15.5 +/- 1.0) and V (13.5 +/- 1.1) of the seminiferous epithelial cycle (P < 0.001). An intermediate level of apoptosis was detected in stage VI (P < 0.02). These stages (IV-VI) correspond to meiotic divisions of primary spermatocytes and mitotic proliferation of B1 and B2 spermatogonia. Establishing basal levels of germ cell apoptosis is a critical step towards understanding fertility and the role of apoptosis in regulating germ cell numbers during spermatogenesis.