Cells of the anterior pituitary

MRI atlas of the pituitary gland in young female adults

The probabilistic topography and inter-individual variability of the pituitary gland (PG) remain undetermined. The absence of a standardized reference atlas hinders research on PG volumetrics. In this study, we aimed at creating maximum probability maps for the anterior and posterior PG in young female adults. We manually delineated the anterior and posterior parts of the pituitary glands in 26 healthy subjects using high-resolution MRI T1 images. A three-step procedure and a cost function-masking approach were employed to optimize spatial normalization for the PG. We generated probabilistic atlases and maximum probability maps, which were subsequently coregistered back to the subjects' space and compared to manual delineations. Manual measurements led to a total pituitary volume of 705 ± 88 mm³, with the anterior and posterior volumes measuring 614 ± 82 mm³ and 91 ± 20 mm³, respectively. The mean relative volume difference between manual and atlas-based estimations was 1.3%. The global pituitary atlas exhibited an 80% (± 9%) overlap for the DICE index and 67% (± 11%) for the Jaccard index. Similarly, these values were 77% (± 13%) and 64% (± 14%) for the anterior pituitary atlas and 62% (± 21%) and 47% (± 17%) for the posterior PG atlas, respectively. We observed a substantial concordance and a significant correlation between the volume estimations of the manual and atlas-based methods for the global pituitary and anterior volumes. The maximum probability maps of the anterior and posterior PG lay the groundwork for automatic atlas-based segmentation methods and the standardized analysis of large PG datasets.

Gut bacteria induce IgA expression in pituitary hormone-secreting cells during aging

Pituitary hormone decline is a hallmark of aging. However, the precise gene regulation mechanism during pituitary aging is unclear. Here, we characterized the cell population alteration and global transcriptional change during pituitary aging through single-cell RNA sequencing (scRNA-seq). We found that mRNA-encoding components of protein translational machinery declined the most in the pituitary during aging. Remarkably, Immunoglobulin A (IgA) was found to be expressed in hormone-secreting cells, and the IgA expression level increased dramatically in aged pituitary. Moreover, the pituitary IgA expression was regulated by gut microbiota. The non-hematopoietic origin of the IgA+ cells in the pituitary was further confirmed through bone marrow transplantation. Somatotropes were identified as the most prominent IgA-producing cells through lineage tracing. Thus, pituitary hormone-secreting cells can generate IgA in an age-dependent manner, and such a process is influenced by gut bacteria.

MicroRNA-7a2 is required for the development of pituitary stem cells

The pituitary gland is inhabited by a subpopulation of SOX2+ stem cells. However, the regulatory mechanisms underlying pituitary stem cell development remain poorly understood. Here, we demonstrate that microRNA-7a (miR-7a) is enriched in the developing pituitary and is spatiotemporally expressed in the pituitary stem cells. Constitutive deletion of miR-7a2 in mice results in pituitary dysplasia emerging during birth, which is primarily manifested as malformed anterior lobes. Using immunofluorescence, immunohistochemistry or in situ hybridization, we observe that the specification of hormone-expressing cells is not impeded post miR-7a2 deletion at birth, although the terminal differentiation of gonadotropes is inhibited. Further investigation of neonatal and adult pituitaries in miR-7a2 knockout mice reveals an expansion of the SOX2+ pituitary stem cell compartment. The inhibition of epithelial-mesenchymal like transition seems to be responsible for this phenotype, rather than abnormal proliferation or apoptosis. Furthermore, our data suggest that Gli3 and Ckap4 are potential targets of miR-7a in pituitary stem cells. In summary, our results identify miR-7a2 as a crucial factor involved in pituitary stem cell development.

Role of heterozygous and homozygous alleles in cryptochrome-deficient mice

The circadian rhythms of physiology and behavior are based on molecular systems at the cellular level, which are regulated by clock genes, including cryptochrome genes, Cry1 and Cry2. In mammals, the circadian pacemaker in the suprachiasmatic nucleus (SCN) of the hypothalamus maintains the circadian rhythms throughout the body. Cry1 and Cry2 play distinct roles in regulating the circadian rhythm. However, the different effects of manipulating clock genes in heterozygous and homozygous alleles, Cry1 and Cry2, remain unclear. Therefore, this study aimed to understand the haplosufficiency of cryptochrome genes in regulating the circadian system. We examined wheel-running activity rhythms and PER2::LUC expression rhythms in SCN slices and pituitary explants in mice. Compared with wild-type mice, Cry1^-/- or Cry2^-/- mice had shortened or lengthened periods in free-running behavioral rhythms and PER2::LUC expression in the SCN and pituitary gland. Cry1^+/- mice had similar circadian rhythms as wild-type mice, although Cry2^+/- mice had lengthened periods. The amplitude of PER2::LUC expression exhibited faster damping in Cry1^-/- mice. Therefore, Cry1 deficiency affects the circadian period length and stability of the circadian system. A single allele of Cry2 deficiency affects the circadian rhythm, whereas that of Cry1 deficit is compensated.

3D Atlas of the Pituitary Gland of the Model Fish Medaka (Oryzias latipes)

In vertebrates, the anterior pituitary plays a crucial role in regulating several essential physiological processes via the secretion of at least seven peptide hormones by different endocrine cell types. Comparative and comprehensive knowledge of the spatial distribution of those endocrine cell types is required to better understand their physiological functions. Using medaka as a model and several combinations of multi-color fluorescence in situ hybridization, we present the first 3D atlas revealing the gland-wide distribution of seven endocrine cell populations: lactotropes, thyrotropes, Lh and Fsh gonadotropes, somatotropes, and pomca-expressing cells (corticotropes and melanotropes) in the anterior pituitary of a teleost fish. By combining in situ hybridization and immunofluorescence techniques, we deciphered the location of corticotropes and melanotropes within the pomca-expressing cell population. The 3D localization approach reveals sexual dimorphism of tshba-, pomca-, and lhb-expressing cells in the adult medaka pituitary. Finally, we show the existence of bi-hormonal cells co-expressing lhb-fshb, fshb-tshba and lhb-sl using single-cell transcriptomics analysis and in situ hybridization. This study offers a solid basis for future comparative studies of the teleost pituitary and its functional plasticity.

Control of Protein and Energy Metabolism in the Pituitary Gland in Response to Three-Week Running Training in Adult Male Mice

It is assumed that crosstalk of central and peripheral tissues plays a role in the adaptive response to physical activity and exercise. Here, we wanted to study the effects of training and genetic predisposition in a marathon mouse model on mRNA expression in the pituitary gland. Therefore, we used a mouse model developed by phenotype selection for superior running performance (DUhTP) and non-inbred control mice (DUC). Both mouse lines underwent treadmill training for three weeks or were kept in a sedentary condition. In all groups, total RNA was isolated from the pituitary gland and sequenced. Molecular pathway analysis was performed by ingenuity pathway analysis (IPA). Training induced differential expression of 637 genes (DEGs) in DUC but only 50 DEGs in DUhTP mice. Genetic selection for enhanced running performance strongly affected gene expression in the pituitary gland and identified 1732 DEGs in sedentary DUC versus DUhTP mice. Training appeared to have an even stronger effect on gene expression in both lines and comparatively revealed 3828 DEGs in the pituitary gland. From the list of DEGs in all experimental groups, candidate genes were extracted by comparison with published genomic regions with significant effects on training responses in mice. Bioinformatic modeling revealed induction and coordinated expression of the pathways for ribosome synthesis and oxidative phosphorylation in DUC mice. By contrast, DUhTP mice were resistant to the positive effects of three-week training on protein and energy metabolism in the pituitary gland.

Invasive and Noninvasive Nonfunctioning Gonadotroph Pituitary Tumors Differ in DNA Methylation Level of LINE-1 Repetitive Elements

PURPOSE

Epigenetic dysregulation plays a role in pituitary tumor pathogenesis. Some differences in DNA methylation were observed between invasive and noninvasive nonfunctioning gonadotroph tumors. This study sought to determine the role of DNA methylation changes in repetitive LINE-1 elements in nonfunctioning gonadotroph pituitary tumors.

METHODS

We investigated LINE-1 methylation levels in 80 tumors and normal pituitary glands with bisulfite-pyrosequencing. Expression of two LINE-1 open reading frames (L1-ORF1 and L1-ORF2) was analyzed with qRT-PCR in tumor samples and mouse gonadotroph pituitary cells treated with DNA methyltransferase inhibitor. Immunohistochemical staining against L1-ORF1p was also performed in normal pituitary glands and tumors.

RESULTS

Hypomethylation of LINE-1 was observed in pituitary tumors. Tumors characterized by invasive growth revealed lower LINE-1 methylation level than noninvasive ones. LINE-1 methylation correlated with overall DNA methylation assessed with HM450K arrays and negatively correlated with L1-ORF1 and L1-ORF2 expression. Treatment of αT3-1 gonadotroph cells with 5-Azacytidine clearly increased the level of L1-ORF1 and L1-ORF2 mRNA; however, its effect on LβT2 cells was less pronounced. Immunoreactivity against L1-ORF1p was higher in tumors than normal tissue. No difference in L1-ORF1p expression was observed in invasive and noninvasive tumors.

CONCLUSION

Hypomethylation of LINE-1 is related to invasive growth and influences transcriptional activity of transposable elements.

GPR101 drives growth hormone hypersecretion and gigantism in mice via constitutive activation of Gs and Gq/11

Growth hormone (GH) is a key modulator of growth and GH over-secretion can lead to gigantism. One form is X-linked acrogigantism (X-LAG), in which infants develop GH-secreting pituitary tumors over-expressing the orphan G-protein coupled receptor, GPR101. The role of GPR101 in GH secretion remains obscure. We studied GPR101 signaling pathways and their effects in HEK293 and rat pituitary GH3 cell lines, human tumors and in transgenic mice with elevated somatotrope Gpr101 expression driven by the rat Ghrhr promoter (Ghrhr^Gpr101). Here, we report that Gpr101 causes elevated GH/prolactin secretion in transgenic Ghrhr^Gpr101 mice but without hyperplasia/tumorigenesis. We show that GPR101 constitutively activates not only G_s, but also G_q/11 and G_12/13, which leads to GH secretion but not proliferation. These signatures of GPR101 signaling, notably PKC activation, are also present in human pituitary tumors with high GPR101 expression. These results underline a role for GPR101 in the regulation of somatotrope axis function.

Imaging of Endoplasmic Reticulum Ca2+ in the Intact Pituitary Gland of Transgenic Mice Expressing a Low Affinity Ca2+ Indicator

The adenohypophysis contains five secretory cell types (somatotrophs, lactotrophs, thyrotrophs, corticotrophs, and gonadotrophs), each secreting a different hormone, and controlled by different hypothalamic releasing hormones (HRHs). Exocytic secretion is regulated by cytosolic Ca²⁺ signals ([Ca²⁺]_C), which can be generated either by Ca²⁺ entry through the plasma membrane and/or by Ca²⁺ release from the endoplasmic reticulum (ER). In addition, Ca²⁺ entry signals can eventually be amplified by ER release via calcium-induced calcium release (CICR). We have investigated the contribution of ER Ca²⁺ release to the action of physiological agonists in pituitary gland. Changes of [Ca²⁺] in the ER ([Ca²⁺]_ER) were measured with the genetically encoded low-affinity Ca²⁺ sensor GAP3 targeted to the ER. We used a transgenic mouse strain that expressed erGAP3 driven by a ubiquitous promoter. Virtually all the pituitary cells were positive for the sensor. In order to mimick the physiological environment, intact pituitary glands or acute slices from the transgenic mouse were used to image [Ca²⁺]_ER. [Ca²⁺]_C was measured simultaneously with Rhod-2. Luteinizing hormone-releasing hormone (LHRH) or thyrotropin releasing hormone (TRH), two agonists known to elicit intracellular Ca²⁺ mobilization, provoked robust decreases of [Ca²⁺]_ER and concomitant rises of [Ca²⁺]_C. A smaller fraction of cells responded to thyrotropin releasing hormone (TRH). By contrast, depolarization with high K⁺ triggered a rise of [Ca²⁺]_C without a decrease of [Ca²⁺]_ER, indicating that the calcium-induced calcium-release (CICR) via ryanodine receptor amplification mechanism is not present in these cells. Our results show the potential of transgenic ER Ca²⁺ indicators as novel tools to explore intraorganellar Ca²⁺ dynamics in pituitary gland in situ.

A cell surface protein controls endocrine ring gland morphogenesis and steroid production

Identification of signals for systemic adaption of hormonal regulation would help to understand the crosstalk between cells and environmental cues contributing to growth, metabolic homeostasis and development. Physiological states are controlled by precise pulsatile hormonal release, including endocrine steroids in human and ecdysteroids in insects. We show in Drosophila that regulation of genes that control biosynthesis and signaling of the steroid hormone ecdysone, a central regulator of developmental progress, depends on the extracellular matrix protein Obstructor-A (Obst-A). Ecdysone is produced by the prothoracic gland (PG), where sensory neurons projecting axons from the brain integrate stimuli for endocrine control. By defining the extracellular surface, Obst-A promotes morphogenesis and axonal growth in the PG. This process requires Obst-A-matrix reorganization by Clathrin/Wurst-mediated endocytosis. Our data identifies the extracellular matrix as essential for endocrine ring gland function, which coordinates physiology, axon morphogenesis, and developmental programs. As Obst-A and Wurst homologs are found among all arthropods, we propose that this mechanism is evolutionary conserved.

Histone Citrullination Represses MicroRNA Expression, Resulting in Increased Oncogene mRNAs in Somatolactotrope Cells

Peptidylarginine deiminase (PAD) enzymes convert histone arginine residues into citrulline to modulate chromatin organization and gene expression. Although PADs are expressed in anterior pituitary gland cells, their functional role and expression in pituitary adenomas are unknown. To begin to address these issues, we first examined normal human pituitaries and pituitary adenomas and found that PAD2, PAD4, and citrullinated histones are highest in prolactinomas and somatoprolactinomas. In the somatoprolactinoma-derived GH3 cell line, PADs citrullinate histone H3, which is attenuated by a pan-PAD inhibitor. RNA sequencing and chromatin immunoprecipitation (ChIP) studies show that the expression of microRNAs (miRNAs) let-7c-2, 23b, and 29c is suppressed by histone citrullination. Our studies demonstrate that these miRNAs directly target the mRNA of the oncogenes encoding HMGA, insulin-like growth factor 1 (IGF-1), and N-MYC, which are highly implicated in human prolactinoma/somatoprolactinoma pathogenesis. Our results are the first to define a direct role for PAD-catalyzed histone citrullination in miRNA expression, which may underlie the etiology of prolactinoma and somatoprolactinoma tumors through regulation of oncogene expression.

Age-Related Changes in MicroRNA in the Rat Pituitary and Potential Role in GH Regulation

The growth hormone/insulin-like growth factor 1 (GH/IGF-1) axis has recently been recognized as an important factor related to the longevity of many organisms. MicroRNAs (miRNAs or miRs) could also participate in diverse biological processes. However, the role of miRNAs in the decline of pituitary GH during the growth process remains unclear. To better characterize the effects of miRNAs on the pituitary, we used a miRNA microarray to investigate the miRNA profile in the rat pituitary from postnatal development throughout the growth process. Then, in vitro experiments were conducted to analyze the miRNAs' potential roles related to GH regulation. Taken together, the microarray results indicated that there were 22 miRNAs differentially expressed during pituitary development. The bioinformatics analysis suggested that the most differentially expressed miRNAs may participate in multiple pathways associated with the pituitary function. Furthermore, the in vitro findings demonstrated that miR-141-3p was involved in GH regulation.

Conditional Deletion of FOXL2 and SMAD4 in Gonadotropes of Adult Mice Causes Isolated FSH Deficiency

The glycoprotein FSH, a product of pituitary gonadotrope cells, regulates ovarian follicle development in females and spermatogenesis in males. FSH is a heterodimer of the common α gonadotropin subunit and the hormone-specific FSHβ subunit (a product of the Fshb gene). Using a conditional knockout approach (Cre-lox), we previously demonstrated that Fshb expression in mice depends on the transcription factors forkhead box L2 (FOXL2) and SMAD4. Deletion of Foxl2 or Smad4 alone led to FSH deficiency, female subfertility, and oligozoospermia in males. Simultaneous deletion of the two genes yielded a greater suppression of FSH and female sterility. The Cre-driver used previously was first active during embryonic development. Therefore, it is unclear whether FOXL2 and SMAD4 play important roles in the development or adult function of gonadotropes, or both. To address this question, we developed a tamoxifen-inducible Cre-driver line, which enabled Foxl2 and Smad4 gene deletions in gonadotropes of adult mice. After tamoxifen treatment, females with previously demonstrated fertility exhibited profound reductions in FSH levels, arrested ovarian follicle development, and sterility. FSH levels were comparably reduced in males 1 or 2 months after treatment; however, spermatogenesis was unaffected. These data indicate that (1) FOXL2 and SMAD4 are necessary to maintain FSH synthesis in gonadotrope cells of adult mice, (2) FSH is essential for female reproduction but appears to be unnecessary for the maintenance of spermatogenesis in adult male mice, and (3) the inducible Cre-driver line developed here provides a powerful tool to interrogate gene function in gonadotrope cells of adult mice.

Neuropeptidome of the Hypothalamus and Pituitary Gland of Indicine × Taurine Heifers: Evidence of Differential Neuropeptide Processing in the Pituitary Gland before and after Puberty

Puberty in cattle is regulated by an endocrine axis, which includes a complex milieu of neuropeptides in the hypothalamus and pituitary gland. The neuropeptidome of hypothalamic-pituitary gland tissue of pre- (PRE) and postpubertal (POST) Bos indicus-influenced heifers was characterized, followed by quantitative analysis of 51 fertility-related neuropeptides in these tissues. Comparison of peptide abundances with gene expression levels allowed assessment of post-transcriptional peptide processing. On the basis of classical cleavage, 124 mature neuropeptides from 35 precursor proteins were detected in hypothalamus and pituitary gland tissues of three PRE and three POST Brangus heifers. An additional 19 peptides (cerebellins, PEN peptides) previously reported as neuropeptides that did not follow classical cleavage were also identified. In the pre-pubertal hypothalamus, a greater diversity of neuropeptides (25.8%) was identified relative to post-pubertal heifers, while in the pituitary gland, 38.6% more neuropeptides were detected in the post-pubertal heifers. Neuro-tissues of PRE and POST heifers revealed abundance differences ( p < 0.05) in peptides from protein precursors involved in packaging and processing (e.g., the granin family and ProSAAS) or neuron stimulation (PENK, CART, POMC, cerebellins). On their own, the transcriptome data of the precursor genes could not predict the neuropeptide profile in the exact same tissues in several cases. This provides further evidence of the importance of differential processing of the neuropeptide precursors in the pituitary before and after puberty.

Copper, zinc and calcium: imaging and quantification in anterior pituitary secretory granules

The anterior pituitary is specialized for the synthesis, storage and release of peptide hormones. The activation of inactive peptide hormone precursors requires a specific set of proteases and other post-translational processing enzymes. High levels of peptidylglycine α-amidating monooxygenase (PAM), an essential peptide processing enzyme, occur in the anterior pituitary. PAM, which converts glycine-extended peptides into amidated products, requires copper and zinc to support its two catalytic activities and calcium for structure. We used X-ray fluorescence microscopy on rat pituitary sections and inductively coupled plasma mass spectrometry on subcellular fractions prepared from rat anterior pituitary to localize and quantify copper, zinc and calcium. X-ray fluorescence microscopy indicated that the calcium concentration in pituitary tissue was about 2.5 mM, 10-times more than zinc and 50-times more than copper. Although no higher than cytosolic levels, secretory granule levels of copper exceeded PAM levels by a factor of 10. Atp7a, which transports copper into the lumen of the secretory pathway, was enriched in endosomes and Golgi, not in secretory granules. If Atp7a transfers copper directly to PAM, this pH-dependent process is likely to occur in Golgi and endosomes.

Effects of prolonged alcohol exposure on somatotrophs and corticotrophs in adult rats: Stereological and hormonal study

Exposure to alcohol alters many physiological processes, including endocrine status. The present study examined whether prolonged alcohol (A) exposure could modulate selected stereological and hormonal aspects of pituitary somatotrophs (growth hormone-GH cells) and corticotrophs (adrenocorticotropic hormone-ACTH cells) in adult rats. Changes in pituitary gland volume; the volume density, total number and volume of GH and ACTH cells following alcohol exposure were evaluated using a stereological system (newCAST), while peripheral GH and ACTH levels were determined biochemically. Our results demonstrated the reduction (p<0.05) of the volume density (37%) and volume of GH cells (29%) in the group A. Also, there was a tendency for the total number of GH cells to be smaller in the group A. Serum GH level was significantly decreased (p<0.05; 70%) in the group A when compared to control values. Moreover, prolonged alcohol exposure induced declines (p<0.05) in volume density (24%) and volume of ACTH cells (29%). The total number of ACTH cells and ACTH level were higher (p<0.05; 42%) in the group A than in control rats. Collectively, these results indicate that prolonged alcohol exposure leads not only to changes in GH and ACTH hormone levels, but also to alterations of the morphological aspects of GH and ACTH cells within the pituitary.

Short- and long-term exposure to alternating magnetic field (50 Hz, 0.5 mT) affects rat pituitary ACTH cells: Stereological study

The aim of the present study was to determine does extremely low frequency magnetic field (ELF-MF, 50 Hz, 0.5 mT) affect pituitary adrenocorticotroph (ACTH) cells in adult animals. We performed two series of experiments: (1) short-term exposure of 3-month-old rats to ELF-MF for 1 and 7 days, and (2) long-term exposure of rats to ELF-MF from their conception to 3 months of age. Stereological study was performed on immunolabeled pituitary ACTH cells. The total number and volume of ACTH cells, the volume of their nuclei and pituitary volume were measured. ELF-MF exposure for 1 day significantly decreased total number and volume of ACTH cells, the volume of their nuclei, as well as pituitary volume. ELF-MF exposure for 7 days significantly reduced only the volume of ACTH cells. Life-long exposure to ELF-MF induced decrease in the volume of ACTH cells and pituitary volume. We can conclude that the applied ELF-MF has a strong influence on morphometrical parameters of the pituitary ACTH cells and could be considered as a stressogenic factor.

Comparative Anterior Pituitary miRNA and mRNA Expression Profiles of Bama Minipigs and Landrace Pigs Reveal Potential Molecular Network Involved in Animal Postnatal Growth

The anterior pituitary is the most important endocrine organ modulating animal postnatal growth, mainly by controlling growth hormone (GH) gene transcription, synthesis, and secretion. As an ideal model for animal postnatal growth studies, the Bama minipig is characterized as having a lower growth performance and fewer individual differences compared with larger pig breeds. In this study, anterior pituitaries from Bama minipig and Landrace pig were used for miRNA and mRNA expression profile analysis using miRNA microarrays and mRNA-seq. Consequently, a total of 222 miRNAs and 12,909 transcripts were detected, and both miRNAs and mRNAs in the two breeds showed high correlation (r > 0.97). Additionally, 41 differentially expressed miRNAs and 2,254 transcripts were identified. Pathways analysis indicated that 32 pathways significantly differed in the two breeds. Importantly, two GH-regulation-signalling pathways, cAMP and inositol 1, 4, 5-triphosphate (IP3), and multiple GH-secretion-related transcripts were significantly down-regulated in Bama minipigs. Moreover, TargetScan and RNAHybrid algorithms were used for predicting differentially expressed miRNAs (DE miRNAs) and differentially expressed mRNAs (DE mRNAs) interaction. By examining their fold-changes, interestingly, most DE miRNA-DE mRNA target pairs (63.68-71.33%) presented negatively correlated expression pattern. A possible network among miRNAs, mRNAs, and GH-regulation pathways was also proposed. Among them, two miRNA-mRNA interactions (Y-47 targets FSHB; ssc-miR-133a-3p targets GNAI3) were validated by dual-luciferase assay. These data will be helpful in understanding the possible molecular mechanisms involved in animal postnatal growth.

Classification of Large Cellular Populations and Discovery of Rare Cells Using Single Cell Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Cell-to-cell variability and functional heterogeneity are integral features of multicellular organisms. Chemical classification of cells into cell type is important for understanding cellular specialization as well as organismal function and organization. Assays to elucidate these chemical variations are best performed with single cell samples because tissue homogenates average the biochemical composition of many different cells and oftentimes include extracellular components. Several single cell microanalysis techniques have been developed but tend to be low throughput or require preselection of molecular probes that limit the information obtained. Mass spectrometry (MS) is an untargeted, multiplexed, and sensitive analytical method that is well-suited for studying chemically complex individual cells that have low analyte content. In this work, populations of cells from the rat pituitary, the rat pancreatic islets of Langerhans, and from the Aplysia californica nervous system, are classified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI) MS by their peptide content. Cells were dispersed onto a microscope slide to generate a sample where hundreds to thousands of cells were separately located. Optical imaging was used to determine the cell coordinates on the slide, and these locations were used to automate the MS measurements to targeted cells. Principal component analysis was used to classify cellular subpopulations. The method was modified to focus on the signals described by the lower principal components to explore rare cells having a unique peptide content. This approach efficiently uncovers and classifies cellular subtypes as well as discovers rare cells from large cellular populations.

Ubiquitin C-terminal hydrolase l1 is expressed in mouse pituitary gonadotropes in vivo and gonadotrope cell lines in vitro

The ubiquitin-proteasome system (UPS) plays a fundamental role in regulating various biological activities. Ubiquitin C-terminal hydrolase L1 (UCH-L1) is a deubiquitinating enzyme, belonging to the UPS. To date, it has been reported that UCH-L1 is highly and restrictedly expressed in neural and reproductive tissues and plays significant roles in these organs. Although the expression of UCH-L1 in the anterior pituitary gland has been reported, the detailed localization and the role of UCH-L1 remain obscure. In the present study, we detected UCH-L1 protein exclusively in hormone-producing cells, but not non-hormone producing folliculostellate cells in the anterior pituitary lobe. In addition, the cytoplasmic expression of UCH-L1 varied and was limited to gonadotropes and mammotropes. To investigate the role of UCH-L1 in anterior pituitary cells, we performed a comparative analysis using genetically UCH-L1-deficient gad mice. Significant decreases in the numbers of gonadotropes and mammotropes were observed in gad mice, suggesting a close involvement of UCH-L1 in these cells. Moreover, we also determined the expression of UCH-L1 in cultured gonadotropes. Taken together, this is the first report to definitely demonstrate the presence of UCH-L1 in mouse anterior pituitary gland, and our results might provide a novel insight for better understanding the role of UCH-L1 in the hypothalamic-pituitary-gonadal axis and in the reproduction.

Conditional knockout of the androgen receptor in gonadotropes reveals crucial roles for androgen in gonadotropin synthesis and surge in female mice

Polycystic ovary syndrome is the major cause of infertility in reproductive aged women. Polycystic ovary syndrome is associated with high circulating levels of androgens and impaired metabolic function. The goal of this study was to understand how androgen signaling via the androgen receptor (AR) affects reproductive function. We knocked out the AR gene specifically in pituitary gonadotropes (PitARKO) to explore the role of androgen on the development of reproductive function in female mice. There was no difference in the age of puberty between control and PitARKO littermates, which was assessed by the ages of vaginal opening and first estrus. Cyclicity and fertility were also studied, and there was no significant difference between control and PitARKO mice. We observed a significant decrease in basal FSH serum and mRNA levels with no corresponding change in LH serum and mRNA levels. Although the numbers of litters born to control and PitARKO females were the same, the litter size was significantly smaller for PitARKO mice. The LH and FSH responses to ovariectomy was altered with reduced LH/FSH hormone and mRNA levels in PitARKO females. This reduction may be due to reduced expression of activin A/B and gnrhr. The preovulatory surge levels of LH and FSH were dramatically lower in PitARKO mice. The number of corpora lutea was decreased whereas the number of antral follicles was similar between control and PitARKO mice. Overall the pituitary AR contributes to the elaboration of the LH surge and normal reproductive function by regulating LH/FSH expression and secretion.

FoxO1 is a negative regulator of FSHβ gene expression in basal and GnRH-stimulated conditions in female

The importance of forkhead box class O (FoxO) proteins in reproductive endocrinology has been confirmed by age-dependent infertility in females in a FoxO3a-knockout mouse model. In this study, FoxO1 was detected in gonadotropes in the anterior pituitary. Overexpression of FoxO1 in primary pituitary cells decreased FSHβ gene expression in both basal and GnRH-stimulated conditions, and this result was replicated by the human FSHβ promoter activity. Although direct binding of FoxO1 to FoxO-binding element (FBE) (at -124 to -119 bp of the human FSHβ promoter) was not detected in an electrophoretic mobility shift assay, a DNA pull-down assay and transfection study using the mutant FBE reporter vector revealed that FBE is necessary in FSHβ suppression by FoxO1, suggestive of other cofactor requirements. GnRH stimulated the phosphoinositide 3-kinase pathway, which induced posttranslational modification of FoxO1 and retained it in the cytoplasm. We also confirmed this result in primary cell cultures; most of the FoxO1 was detected in the cytoplasm when treated with GnRH but in the nucleus when the phosphoinositide 3-kinase pathway was inhibited. These findings suggest that FoxO1 is regulated by the GnRH signaling pathway and functions as a negative regulator of FSHβ gene expression.

Stem cells in the canine pituitary gland and in pituitary adenomas

Cushing's disease (CD) or pituitary-dependent hypercortisolism is a common endocrinopathy in dogs, with an estimated prevalence of 1 or 2 in 1000 dogs per year. It is caused by an adrenocorticotropic hormone secreting adenoma in the pars distalis or pars intermedia of the pituitary gland. The pituitary gland is a small endocrine gland located in the pituitary fossa. In the postnatal individual, the hypothalamus-pituitary axis plays a central role in maintaining homeostatic functions, like control of metabolism, reproduction, and growth. Stem cells are suggested to play a role in the homeostatic adaptations of the adult pituitary gland, such as the rapid specific cell-type expansion in response to pregnancy or lactation. Several cell populations have been suggested as pituitary stem cells, such as Side Population cells and cells expressing Sox2 or Nestin. These cell populations are discussed in this review. Also, stem and progenitor cells are thought to play a role in pituitary tumorigenesis, such as the development of pituitary adenomas in dogs. There are limited reports on the role of stem cells in pituitary adenomas, especially in dogs. Further studies are needed to identify and characterize this cell population and to develop specific cell targeting therapeutic strategies as a new way of treating canine CD.

Mechanisms underlying the increased plasma ACTH levels in chronic psychosocially stressed male mice

Mice exposed to chronic subordinate colony housing (CSC, 19 days), an established paradigm for chronic psychosocial stress, show unaffected basal morning plasma corticosterone (CORT) concentrations, despite enlarged adrenal glands and an increased CORT response to an acute heterotypic stressor. In the present study we investigate the mechanisms underlying these phenomena at the level of the pituitary. We show that both basal and acute stressor-induced (forced swim (FS), 6 min) plasma adrenocorticotropic hormone (ACTH) concentrations, the number of total and corticotroph pituitary cells, and relative protein expression of pituitary mineralocorticoid receptor and FK506-binding protein 51 was increased in CSC compared with single-housed control (SHC) mice, while relative corticotropin releasing hormone (CRH) receptor 1 (CRH-R1) and glucocorticoid receptor protein expression was down-regulated. Relative pituitary pro-opiomelanocortin and arginine vasopressin (AVP) receptor 1b (AVPR-1b) protein expression, FS (6 min)-induced ACTH secretion in dexamethasone-blocked mice, and the number of AVP positive magnocellular and parvocellular neurons in the paraventricular hypothalamic nucleus (PVN) was unaffected following CSC. Taken together, the data of the present study indicate that 19 days of CSC result in pituitary hyperactivity, under both basal and acute heterotypic stress conditions. Although further studies have to assess this in detail, an increased number of pituitary corticotrophs together with unaffected relative pituitary AVPR-1b and decreased CRH-R1 protein expression following CSC suggests that pituitary hyperdrive is mediated by newly formed corticotrophs that are more sensitive to AVP than CRH. Moreover, our data indicate that changes in PVN AVP and negative feedback inhibition seem not to play a major role in pituitary hyperactivity following CSC.

Expression stability of reference genes for quantitative RT-PCR of healthy and diseased pituitary tissue samples varies between humans, mice, and dogs

Pituitary surgery generates pituitary tissue for histology, immunohistochemistry, and molecular biological research. In the last decade, the pathogenesis of pituitary adenomas has been extensively studied in humans, and to a lesser degree in dogs, and tumor oncogenesis has been studied in knock-out mice, often by means of quantitative reversed-transcriptase PCR (RT-qPCR). A precondition of such analyses is that so-called reference genes are stably expressed regardless of changes in disease status or treatment. In this study, the expression of six frequently used reference genes, namely, tata box binding protein (tbp), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta polypeptide (ywhaz), hydroxymethylbilane synthase (hmbs), beta-2-microglobulin (b2m), succinate dehydrogenase complex subunit A (sdha), and glyceraldehyde 3 phosphate dehydrogenase 1 (gapdh), was studied in pituitary tissue (normal and adenoma) from three species (humans, mice, and dogs). The stability of expression of these reference genes differed between species and between healthy and diseased tissue within one species. Quantitative analysis based on a single reference gene that is assumed to be stably expressed might lead to wrong conclusions. This cross-species analysis clearly emphasizes the need to evaluate the expression stability of reference genes as a standard and integral aspect of study design and data analysis, in order to improve the validity of the conclusions drawn on the basis of quantitative molecular analyses.

Characterization of recombinant human and bovine thyroid-stimulating hormone preparations by mass spectrometry and determination of their endotoxin content

Background

The TSH stimulation test to confirm canine hypothyroidism is commonly performed using a recombinant human TSH (rhTSH), as up to date, canine TSH is not yet commercially available. Limiting factors for the use of rhTSH are its high costs and occasional difficulties in product availability. Less expensive bovine TSH preparations (bTSH) purified from bovine pituitary glands are readily commercially available. The aim of this study was to evaluate two different bTSH products as alternative to rhTSH using mass spectrometry.

Results

More than 50 proteins, including other pituitary hormones, bovine albumin, hemoglobin, and tissue proteins were identified in the bTSH preparations. In contrast, rhTSH proved to be a highly pure product. Significantly higher endotoxin levels could be detected in all bTSH products compared to the rhTSH.

Conclusions

Both bTSH products are crude mixtures and therefore not an acceptable alternative to rhTSH. Their use should be discouraged to prevent unintended side effects.

Neuroendocrine signalling: natural variations on a Ca2+ theme

This special issue on Ca(2+) signalling in neuroendocrine cells is an opportunity to assess, through a range of first-class review articles, the complex world of endocrine signalling, a complexity that is probably best captured by calling it "diversity in unity". The unity comes from the fact that all the endocrine cells are excitable cells, able to generate action potentials and are using Ca(2+) as an essential informational molecule, coupling cell stimulation with the activation of secretion, through the exocytotic process. The 'diversity' element, illustrated by almost all the reviews, stems from the modalities employed to achieve the increase in cytosolic Ca(2+) signal, the balance between the participation of Ca(2+) entry through the plasma membrane voltage-operated Ca(2+) channels and the release of Ca(2+) from intracellular Ca(2+) stores, and the cross-talk between the Ca(2+) and cyclic AMP signalling pathways.

Distinct receptor subtypes mediate arginine vasopressin-dependent ACTH release and intracellular calcium mobilization in rat pituitary cells

In the present study, adrenocorticotropic hormone (ACTH) release and intracellular calcium ([Ca(2+)](i)) increase induced by arginine vasopressin (AVP) were characterized in collagenase-dispersed and 3-day cultured rat anterior pituitary cells. AVP and the selective vasopressin V(1b) receptor agonist, [1-deamino-4-cyclohexylalanine]AVP (d[Cha(4)]AVP) induced ACTH release with nanomolar potencies in both cell preparations, and produced a maximal stimulation that was about 1.5 fold greater in the 3-day cultured cells, indicating that the vasopressin V(1b) receptor-ACTH release pathway is enhanced over time in culture. In dispersed cells, AVP, oxytocin and d[Cha(4)]AVP induced [Ca(2+)](i) increases with nanomolar potencies. The selective vasopressin V(1a) receptors antagonist, SR49059 (100 nM), together with the selective oxytocin receptors antagonist (d(CH(2))(5)(1)Tyr(Me)(2),Thr(4),Orn(8),Tyr-NH(2)(9)-vasotocin (100 nM), inhibited the maximal AVP response by ~70%, without affecting the response to d[Cha(4)]AVP, suggesting that the V(1b) receptor was only partially responsible for the AVP-induced [Ca(2+)](i) increase. In contrast, in 3-day cultures, AVP induced an increase in [Ca(2+)](i), while oxytocin and d[Cha(4)]AVP did not. The response to AVP was completely antagonized by SR49059, whereas the vasopressin V(1b) receptor antagonists, SSR149415 and (d(CH(2))(5)(1)Tyr(Me)(2),Thr(4),Orn(8),Tyr-NH(2)(9))-vasotocin had no effect, indicating that the [Ca(2+)](i) increase was mediated exclusively by vasopressin V(1a) receptors. In conclusion, the enhancement of vasopressin V(1b) receptor-mediated ACTH release and the lack of a detectable vasopressin V(1b) receptor coupling to [Ca(2+)](i) increase in cultured cells suggests the activation of a different/additional signaling pathway in the molecular mechanism of ACTH release.

Identification and characterisation of side population cells in the canine pituitary gland

To date, stem/progenitor cells have not been identified in the canine pituitary gland. Cells that efficiently exclude the vital dye Hoechst 33342 can be visualised and identified using fluorescence activated cell sorting (FACS) as a 'side population' (SP), distinct from the main population (MP). Such SPs have been identified in several tissues and display stem/progenitor cell characteristics. In this study, a small SP (1.3%, n=6) was detected in the anterior pituitary glands of healthy dogs. Quantitative PCR indicated significantly higher expression of CD34 and Thy1 in this SP, but no differences in the expression of CD133, Bmi-1, Axin2 or Shh. Pro-opiomelanocortin (POMC) and Lhx3 expression were significantly higher in the MP than in the SP, but no differences in the expression of Tpit, GH or PRL were found. The study demonstrated the existence of an SP of cells in the normal canine pituitary gland, encompassing cells with stem cell characteristics and without POMC expression.

Time-dependent effects of starvation on serum, pituitary and hypothalamic leptin levels in rats

Leptin is produced by white adipose tissue and other cell types and is involved in both short- and long-term appetite control. Here we studied effects of starvation on serum, pituitary and hypothalamic levels of leptin during 72 h period. Each of the starved groups was sacrificed simultaneously with the group of ad libitum fed animals. The progression of the discrete starvation response phases was monitored by testing the blood glucose, free fatty acid, urea and corticosterone levels. Starvation caused biphasic increase in corticosterone and free fatty acid levels, and significant but transient decrease in urea and glucose levels. Starvation also abolished diurnal rhythm of changes in leptin concentrations in serum and hypothalamic and pituitary tissues. Only 6 h starving period was sufficient to lock serum leptin at low levels, whereas 12 h were needed to silence leptin production/secretion in hypothalamus for the whole examined period. In contrast, leptin production by pituitary tissues of starved animals required 24 h to reach minimum, followed by full recovery by the end of starvation period. These results indicate the tissue specific pattern of leptin release and suggest that the locally produced leptin could activate its receptor in pituitary cells independently of serum levels of this hormone.

DNA methylation of intronic enhancers directs tissue-specific expression of steroidogenic factor 1/adrenal 4 binding protein (SF-1/Ad4BP)

The nuclear receptor steroidogenic factor 1/adrenal 4 binding protein (SF-1/Ad4BP) is an essential regulator of endocrine development and function, and the expression of the corresponding gene (sf-1/ad4bp) is precisely regulated in a time- and tissue-dependent manner. We previously demonstrated that the basal promoter of sf-1/ad4bp is controlled by DNA methylation and that its methylation status reflects the expression pattern of SF-1/Ad4BP. Recently, three intronic enhancers were identified in the sf-1/ad4bp gene that target SF-1/Ad4BP expression to the fetal adrenal (FAdE; fetal adrenal-specific enhancer), to pituitary gonadotropes (PGE; pituitary gonadotrope-specific enhancer), and to the ventromedial hypothalamic nucleus (VMHE; ventromedial hypothalamic nucleus-specific enhancer). Here, we demonstrate that the activity of these enhancers is correlated with their DNA methylation status. We show that they are hypomethylated in tissues where they are active and generally hypermethylated in tissues where they are not active. Furthermore, we demonstrate in transient transfection experiments that forced DNA methylation represses reporter gene activity driven by these enhancers. These data directly demonstrate a functional significance for the enhancers' methylation status. Intriguingly, further analyses of the basal promoter in gonadotropes revealed that it is methylated in these cells, in contrast to other SF-1/Ad4BP-expressing tissues. Consistent with this, sf-1/ad4bp is transcribed from an alternative promoter in gonadotropes. Taken together, our experiments show that the tissue-specific expression of SF-1/Ad4BP is epigenetically regulated and identify tissue-specific differentially methylated regions within the sf-1/ad4bp locus that are essential for its transcriptional control.

Expression of Ki-67, PCNA, and p27kip1 in canine pituitary corticotroph adenomas

Pituitary-dependent hypercortisolism (PDH), which is caused by adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas, is a common endocrinopathy in dogs. Dogs with non-enlarged pituitaries harboring a microadenoma have a better prognosis than those with enlarged pituitaries. The aim of this study was to investigate the expression of the proliferation markers Ki-67 and proliferating cell nuclear antigen (PCNA) and the cell-cycle inhibitor p27kip1 in corticotroph adenomas in enlarged and non-enlarged pituitaries. The expression of Ki-67, PCNA, and p27kip1 was analyzed by immunohistochemical staining of 17 pituitary adenoma samples harvested during pituitary surgery in dogs with PDH. The labeling index was calculated by counting the number of immunopositive cells per 1,000 cells. The mean (+/- standard deviation) labeling index for Ki-67 was 8.4%+/-14.2% for the group with enlarged pituitaries, and 8.8%+/-5.5% for the group with non-enlarged pituitaries; that for PCNA was 35.5%+/-12.2% and 37.0%+/-15.5%; and that for p27kip1 was 29.3%+/-22.6% and 42.5%+/-27.9%, respectively. No significant differences in Ki-67, PCNA, and p27kip1 labeling indices were found between enlarged and non-enlarged pituitaries. However, a trend toward significance was observed when comparing the expression of p27kip1 in enlarged pituitaries versus normal pituitary tissue. It is concluded that Ki-67 and PCNA are not useful as proliferative markers for studying the pathobiology of pituitary corticotroph adenomas in dogs.

Identification of candidate genes for human pituitary development by EST analysis

Background

The pituitary is a critical neuroendocrine gland that is comprised of five hormone-secreting cell types, which develops in tandem during the embryonic stage. Some essential genes have been identified in the early stage of adenohypophysial development, such as PITX1, FGF8, BMP4 and SF-1. However, it is likely that a large number of signaling molecules and transcription factors essential for determination and terminal differentiation of specific cell types remain unidentified. High-throughput methods such as microarray analysis may facilitate the measurement of gene transcriptional levels, while Expressed sequence tag (EST) sequencing, an efficient method for gene discovery and expression level analysis, may no-redundantly help to understand gene expression patterns during development.

Results

A total of 9,271 ESTs were generated from both fetal and adult pituitaries, and assigned into 961 gene/EST clusters in fetal and 2,747 in adult pituitary by homology analysis. The transcription maps derived from these data indicated that developmentally relevant genes, such as Sox4, ST13 and ZNF185, were dominant in the cDNA library of fetal pituitary, while hormones and hormone-associated genes, such as GH1, GH2, POMC, LHβ, CHGA and CHGB, were dominant in adult pituitary. Furthermore, by using RT-PCR and in situ hybridization, Sox4 was found to be one of the main transcription factors expressed in fetal pituitary for the first time. It was expressed at least at E12.5, but decreased after E17.5. In addition, 40 novel ESTs were identified specifically in this tissue.

Conclusion

The significant changes in gene expression in both tissues suggest a distinct and dynamic switch between embryonic and adult pituitaries. All these data along with Sox4 should be confirmed to further understand the community of multiple signaling pathways that act as a cooperative network that regulates maturation of the pituitary. It was also suggested that EST sequencing is an efficient means of gene discovery.

Facial and pituitary morphology are related in Dutch patients with GH deficiency

OBJECTIVE

Classical GH deficiency (GHD) is associated with typical phenotypic features. We have analysed standardized photographs of 137 Caucasian patients with GHD, in order to examine the relations between auxological, biochemical, pituitary and facial morphometric features.

PATIENTS AND MEASUREMENTS

We analysed pictures of 137 patients: 73 (55 Males/18 Females) with Isolated GHD and 64 (48 M/16 F) with multiple pituitary hormone deficiency (MPHD). Of each patient, standardized frontal and lateral digital pictures were taken and analysed using Adobe Photoshop 5.0.

RESULTS

Canthal index (CI), the relative distance between the eyes, was related to pituitary morphology. Patients with an ectopic posterior pituitary (EPP) had significantly higher CI values than patients without EPP. We found CI > 39 to be a good cut-off value to select children with highest probability of having EPP. The combination of CI > 39 with the presence of hormonal deficiencies additional to GHD strongly predicted EPP: 93% of the patients with a CI > 39 and additional hormonal deficiencies had EPP, in contrast to 77% of the patients with additional hormonal deficiencies but a CI < 39, and 29% of the patients with none of these criteria (P = 0.0001).

CONCLUSION

CI, measured on digital pictures, is associated with ectopia of the posterior pituitary and this might be caused by an altered midline development, affecting both the pituitary and the facial structures of GHD patients.

Reporter expression, induced by a growth hormone promoter-driven Cre recombinase (rGHp-Cre) transgene, questions the developmental relationship between somatotropes and lactotropes in the adult mouse pituitary gland

This report describes the development and validation of the rGHp-Cre transgenic mouse that allows for selective Cre-mediated recombination of loxP-modified alleles in the GH-producing cells of the anterior pituitary. Initial screening of the rGHp-Cre parental line showed Cre mRNA was specifically expressed in the anterior pituitary gland of adult Cre+/- mice and cephalic extracts of e17 Cre+/- fetuses. Heterozygote rGHp-Cre transgenic mice were crossbred with Z/AP reporter mice to generate Cre+/-,Z/AP+/- offspring. In this model system, the GH promoter-driven, Cre-mediated recombination of the Z/AP reporter leads to human placental alkaline phosphatase (hPLAP) expression that serves to mark cells that currently produce GH, in addition to cells that would have differentiated from GH cells but currently do not express the GH gene. Double immunocytochemistry of adult male and female Cre+/-,Z/AP+/- pituitary cells revealed the majority (approximately 99%) of GH-producing cells of the anterior pituitary also expressed hPLAP, whereas ACTH-, TSH-, and LH-producing cells were negative for hPLAP, confirming previous reports that corticotropes, thyrotropes, and gonadotropes develop independently of the somatotrope lineage. A small subset (approximately 10%) of the prolactin-producing cells was positive for hPLAP, consistent with previous reports showing lactotropes can arise from somatotropes during pituitary development. However, the fact that 90% of prolactin-producing cells were negative for hPLAP suggests that the majority of lactotropes in the adult mouse pituitary gland develop independently of the somatotrope lineage. In addition to developmental studies, the rGHp-Cre transgenic mouse will provide a versatile tool to study the role of a variety of genes in somatotrope function and neoplastic transformation.

Positioning the extreme anterior in Xenopus: cement gland, primary mouth and anterior pituitary

The extreme anterior of the deuterostome embryo is unusual in that ectoderm and endoderm are directly juxtaposed, without intervening mesoderm. In all vertebrates, this region gives rise to the anterior pituitary, the primary mouth and, in most frogs, to the mucus-secreting cement gland. Using the frog Xenopus laevis as a paradigm, we suggest that, initially, the extreme anterior forms a homogenous domain characterized by expression of pitx genes. Subsequently, this domain becomes subdivided to form these three different structures under the influence of different inductive signals from surrounding tissues.