Pituitary network connectivity as a mechanism for the luteinising hormone surge

Clustering of multi-tissue transcriptomes in gilts with normal cyclicity or delayed puberty reveals genes related to pubertal development†

In gilts, puberty is marked by standing estrus in the presence of a boar. Delayed puberty (DP; failure to display pubertal estrus) is a major reason for gilt removal. To investigate the physiological determinants underlying DP in gilts, transcriptomic data from tissues relevant to estrus and puberty, such as mediobasal hypothalamus, anterior pituitary gland, ovarian cortex, olfactory bulb, amygdala, and hippocampus, were obtained from age-matched DP (n = 8) and cyclic control gilts at follicular phase (n = 8) and luteal phase (n = 8) of the estrous cycle. A gene expression module analysis via three-way gene × individual × tissue clustering using tensor decomposition identified pituitary and ovary gene modules contributing to regulation of pubertal development. Analysis of gene expression in the hypothalamic-pituitary-ovary axis identified reduced expression of hypothalamic genes critical for stimulating gonadotropin secretion (KISS1 and TAC3) and reduced expression of LHB in the anterior pituitary of DP gilts compared with their cyclic counterparts. Consequently, luteinizing hormone-induced genes in the ovary important for folliculogenesis (OXTR, RUNX2, and PTX3) were less expressed in DP gilts. Other intrafollicular genes (AHR, PTGS2, PTGFR, and IGFBP7) and genes in the steroidogenesis pathways (STAR and CYP11A1) necessary to complete the ovulatory cascade were also less expressed in DP gilts. This is the first clustering of multi-tissue expression data from DP and cyclic gilts to identify genes differentially expressed in gilts of similar ages but at different levels of sexual development. A critical lack of gonadotropin support and reduced ovarian responsiveness underlie DP in gilts.

Renewing an old interest: Pituitary folliculostellate cells

Anterior pituitary folliculostellate (FS) cells, first described almost 50 years ago, have a wide range of functions with respect to supporting and coordinating endocrine cell function, in particular through paracrine and gap junction-mediated signalling. Our previous studies identified the morphological organisation of FS cells, which mediates coordinated calcium activity throughout the homotypic FS network and allows signalling across the whole pituitary gland. It is also clear that FS cells can modify endocrine output and feedback on pituitary axes over a range of timescales. Recently, several studies have defined FS cells as a source of anterior pituitary endocrine cell renewal, which has resulted in a renaming of FS cells as "Sox2+ve stem cells". Here, we highlight the broader potential of the FS cell population in fine-tuning and coordinating pituitary axes function. In addition, we identify a need for: the definition of the possible subtypes of FS cell and their relationship with the stem cell population; the potential role of FS cells in pulsatile hormone secretion and coordination of heterotypic cell networks; and the roles that FS cells may play in both early-life programming of pituitary axes and in memory, or anticipation, of demand. Further studies of FS cells may demonstrate the fundamental importance of this cell type and its potential as a therapeutic target to correct pituitary gland dysfunction, one of which is stem cell therapy. Clearly, a thorough understanding of all of these interactions and relationships of FS and endocrine cells is required whatever therapeutic use is suggested by their various roles.

Variations in the adenohypophysis of the expression of proliferating cellular nuclear antigen, oestrogen and androgen receptors in relation to gonadal steroids during pregnancy of viscachas (Lagostomus maximus maximus)

Viscachas are native rodents of South America that present a long pregnancy of ~154 days. In this work, we analysed variations in the expression of proliferating cellular nuclear antigen, oestrogen and androgen receptors (ERα and AR) in pituitary pars distalis (PD) and pars tuberalis (PT) in relation to oestradiol and testosterone serum levels in non-pregnant and pregnant viscachas. In PD, cell proliferation increased with pregnancy and lactotrophs proliferated during mid-pregnancy (MP). ERα nuclear-immunoreactive cells (ERαn-ir) were maximal in late pregnancy and AR expression did not vary during pregnancy. In PT, cell proliferation and AR expression increased during pregnancy, but ERα expression was very scarce. The immunostaining pattern of receptors was different in PD and PT. The peak of serum oestradiol and testosterone occurred during MP. Our results suggest that cell proliferation and gonadal receptors might be differentially regulated in the pituitary by oestradiol and testosterone during viscacha pregnancy.

The anterior pituitary gap junctions: potential targets for toxicants

The anterior pituitary regulates endocrine organs and physiological activities in the body. Environmental pollutants and drugs deleterious to the endocrine system may affect anterior pituitary activity through direct action on anterior pituitary cells. Within the gland, endocrine and folliculostellate cells are organized into and function as individual tridimensional networks, each network regulating its activity by coordinating the connected cells' responses to physiological or pathological cues. The gap junctions connecting endocrine cells and/or folliculostellate cells allow transmission of information among cells that is necessary for adequate network function. Toxicants may affect gap junctions as well as the physiology of the anterior pituitary. However, whether toxicants effects on anterior pituitary hormone secretion involve gap junctions is unknown. The folliculostellate cell gap junctions are sensitive to hormones, cytokines and growth factors. These cells may be an interesting experimental model for evaluating whether toxicants target anterior pituitary gap junctions.

The induction of ovulation by pulsatile administration of GnRH: an appropriate method in hypothalamic amenorrhea

The induction of ovulation by the means of a pump which assures the pulsatile administration of GnRH is a well-known method that applies to women suffering from amenorrhea of hypothalamic origin. Although a simple and efficient method to establish fertility, it is underused. Twelve patients suffering from this condition, 1 Kallmann syndrome, 4 normosmic isolated hypogonadotropic hypogonadism, and 7 functional hypothalamic amenorrhea desiring pregnancy were treated. They underwent one or more cycles of pulsatile GnRH, at a frequency of 90 minutes, either by the intravenous or the subcutaneous route. An initial dose of 5 μg per pulse in the intravenous route was administered and of 15 μg per pulse in the subcutaneous route. The treatment was monitored by regular dosing of gonadotropins, estradiol and progesterone, and the development of follicles and ovulation was monitored by intra-vaginal ultrasonography. All the patients had documented ovulation, after a mean of 17 days on pump stimulation. Single ovulation occurred in 30 of 33 treatment cycles, irrespective of the route of administration. Ovulation resulted in 10 pregnancies over 7 patients (2 pregnancies in 3 of them), distributed in the 3 diagnostic categories. For comparison, a patient with PCOS treated similarly, disclosed premature LH surge without ovulation.

Distinctive actions of connexin 46 and connexin 50 in anterior pituitary folliculostellate cells

Folliculostellate cell gap junctions establish a network for the transmission of information within the anterior pituitary. Connexins make up gap junction channels. Changes in connexin (Cx) turnover modify gap junction-mediated intercellular communication. We have reported that cytokines and hormones influence Cx43 turnover and coupling in folliculostellate cells and in the folliculostellate cell line TtT/GF. In addition, the expression of different connexins alters intercellular communication and connexins may have functions besides cell coupling. Here we assessed the expression, turnover and subcellular localization of Cx46 and Cx50 in the anterior pituitary and TtT/GF cells. Then, we assessed the impact of various natural (lactation, annual reproductive cycle, bFGF) and pathological (autoimmune orchitis, diabetes/obesity) conditions associated with altered anterior pituitary hormone secretion on Cx46 and Cx50. Anterior pituitary Cx46 and Cx50 expression and subcellular distribution were cell-dependent. Cx46 was expressed by folliculostellate, TtT/GF and endocrine cells. In the cytoplasm, Cx46 was chiefly associated with lysosomes. Variously sized Cx46 molecules were recovered exclusively in the TtT/GF cell nuclear fraction. In the nucleus, Cx46 co-localized with Nopp-140, a nucleolar factor involved in rRNA processing. Neither cytoplasmic nor nuclear Cx46 and Cx43 co-localized. Cx50 localized to folliculostellate and TtT/GF cells, and to the walls of blood capillaries, not to endocrine cells. Cx50 was cytoplasmic and associated with the cell membrane, not nuclear. Cx50 did not co-localize with Cx46 but it co-localized in the cytoplasm and co-immunoprecipitated with Cx43. Cx46 and Cx50 responses to various physiological and pathological challenges were different, often opposite. Cx46 and Cx43 expression and phosphorylation profiles differed in the anterior pituitary, whereas Cx50 and Cx43 were similar. The data suggest that Cx46 participates to cellular growth and proliferation and that Cx50, together with Cx43, contributes to folliculostellate cell coupling.

Preconception care: preventing and treating infections

Introduction

Infections can impact the reproductive health of women and hence may influence pregnancy related outcomes for both the mother and the child. These infections range from sexually transmitted infections (STIs) to TORCHS infections to periodontal disease to systemic infections and may be transmitted to the fetus during pregnancy, labor, delivery or breastfeeding.

Methods

A systematic review and meta-analysis of the evidence was conducted to ascertain the possible impact of preconception care for adolescents, women and couples of reproductive age on MNCH outcomes. A comprehensive strategy was used to search electronic reference libraries, and both observational and clinical controlled trials were included. Cross-referencing and a separate search strategy for each preconception risk and intervention ensured wider study capture.

Results

Preconception behavioral interventions significantly declines re-infection or new STI rates by 35% (95% CI: 20-47%). Further, condom use has been shown to be the most effective way to prevent HIV infection (85% protection in prospective studies) through sexual intercourse. Intervention trials showed that preconception vaccination against tetanus averted a significant number of neonatal deaths (including those specifically due to tetanus) when compared to placebo in women receiving more than 1 dose of the vaccine (OR 0.28; 95% CI: 0.15-0.52); (OR 0.02; 95% CI: 0.00-0.28) respectively.

Conclusion

Preconception counseling should be offered to women of reproductive age as soon as they test HIV-positive, and conversely women of reproductive age should be screened with their partners before pregnancy. Risk assessment, screening, and treatment for specific infections should be a component of preconception care because there is convincing evidence that treatment of these infections before pregnancy prevents neonatal infections.

Preconception care: delivery strategies and packages for care

The notion of preconception care aims to target the existing risks before pregnancy, whereby resources may be used to improve reproductive health and optimize knowledge before conceiving. The preconception period provides an opportunity to intervene earlier to optimize the health of potential mothers (and fathers) and to prevent harmful exposures from affecting the developing fetus. These interventions include birth spacing and preventing teenage pregnancy, promotion of contraceptive use, optimization of weight and micronutrient status, prevention and management of infectious diseases, and screening for and managing chronic conditions. Given existing interventions and the need to organize services to optimize delivery of care in a logical and effective manner, interventions are frequently co-packaged or bundled together. This paper highlights packages of preconception interventions that can be combined and co-delivered to women through various delivery channels and provides a logical framework for development of such packages in varying contexts.

Intercellular communications within the rat anterior pituitary. XVI: postnatal changes of distribution of S-100 protein positive cells, connexin 43 and LH-RH positive sites in the pars tuberalis of the rat pituitary gland. An immunohistochemical and electron microscopic study

The architecture of luteinizing hormone-releasing hormone (LH-RH) nerve ends and the S-100 protein containing folliculo-stellate cells forming gap junctions in the pars tuberalis is basically important in understanding the regulation of the hormone producing mechanism of anterior pituitary glands. In this study, intact male rats 5-60 days old were prepared for immunohistochemistry and electron microscopy. From immunostained sections, the S-100 containing cells in pars tuberalis were first detected on day 30 and increased in number to day 60; this was parallel to the immunohistochemical staining of gap junction protein, connexin 43. LH-RH positive sites were clearly observed on just behind the optic chiasm and on the root of pituitary stalk on day 30. On day 60, the width of layer increased, while follicles and gap junctions were frequently observed between agranular cells in 10 or more layers of pars tuberalis. In the present study, we investigated the sexual maturation of the anterior pituitary glands through the postnatal development of S-100 positive cells, connexin 43 and LH-RH nerves. It is suggested that the folliculo-stellate cell system including the LH-RH neurons in the pars tuberalis participates in the control of LH secretion along with the portal vein system.

Anterior pituitary cell networks

Both endocrine and non-endocrine cells of the pituitary gland are organized into structural and functional networks which are formed during embryonic development but which may be modified throughout life. Structural mapping of the various endocrine cell types has highlighted the existence of distinct network motifs and relationships with the vasculature which may relate to temporal differences in their output. Functional characterization of the network activity of growth hormone and prolactin cells has revealed a role for cell organization in gene regulation, the plasticity of pituitary hormone output and remarkably the ability to memorize altered demand. As such, the description of these endocrine cell networks alters the concept of the pituitary from a gland which simply responds to external regulation to that of an oscillator which may memorize information and constantly adapt its coordinated networks' responses to the flow of hypothalamic inputs.

Identification of estradiol/ERα-regulated genes in the mouse pituitary

Estrogen acts to prime the pituitary prior to the GnRH-induced LH surge by undiscovered mechanisms. This study aimed to identify the key components that mediate estrogen action in priming the pituitary. RNA extracted from the pituitaries of metestrous (low estrogen) and proestrus (high estrogen) stage mice, as well as from ovariectomized wild-type and estrogen receptor α (ERα) knockout mice treated with 17β-estradiol (E(2)) or vehicle, was used for gene expression microarray. Microarray data were then aggregated, built into a functional electronic database, and used for further characterization of E(2)/ERα-regulated genes. These data were used to compile a list of genes representing diverse biological pathways that are regulated by E(2) via an ERα-mediated pathway in the pituitary. This approach substantiates ERα regulation of membrane potential regulators and intracellular vesicle transporters, among others, but not the basic components of secretory machinery. Subsequent characterization of six selected genes (Cacna1a, Cacna1g, Cited1, Abep1, Opn3, and Kcne2) confirmed not only ERα dependency for their pituitary expression but also the significance of their expression in regulating GnRH-induced LH secretion. In conclusion, findings from this study suggest that estrogen primes the pituitary via ERα by equipping pituitary cells with critical cellular components that potentiate LH release on subsequent GnRH stimulations.