Matrix metalloproteinase-9 expression in folliculostellate cells of rat anterior pituitary gland

Effects of different coating materials on the morphological characteristics of chicken adenohypophyseal folliculo-stellate cells in vitro

Chicken adenohypophyseal cells were cultured in plates coated with different materials, and their morphologies were examined to confirm the characteristics of chicken folliculo-stellate (FS) cells in vitro. The adenohypophyseal cells were dispersed with a collagenase/trypsin mixture in media and seeded in plates coated in either poly L-lysine (PLL), collagen, or laminin. After 7 days of culture, the cells were fixed and immunocytochemistry was performed. 5-Bromo-2'-deoxyuridine incorporation test indicated that the proliferation activity of the culture cells was different based on the coating materials, and it was higher in the collagen-coated plate than two other coating materials. Fluorescence immunocytochemistry was also performed using mixed antibodies against growth hormone, prolactin, luteinizing hormone β-subunit, basic cytokeratin (bCK), and S100B. The culture cells on the PLL- and laminin-coated surfaces were round or oval in shape, and bCK-immunopositive FS cells were morphologically indistinguishable from endocrine cells. In the collagen-coated plate, many endocrine cells were round or oval in shape, but FS cells displayed a larger and flattened morphology. S100B-immunoreactions were localized in the nuclei of bCK-immunopositive FS cells. These results suggest that culturing the chicken adenohypophyseal cells in the collagen-coated plate enables the distinction of FS cells from endocrine cells.

Alteration of Extracellular Matrix Components in the Anterior Pituitary Gland of Neonatal Rats Induced by a Maternal Bisphenol A Diet during Pregnancy

The extracellular matrix (ECM) plays crucial roles in the anterior pituitary gland via the mechanism of cell-ECM interaction. Since bisphenol A (BPA), a well-known endocrine disruptor, can cross through the placenta from mother to fetus and bind with estrogen receptors, cell populations in the neonatal anterior pituitary gland could be the target cells affected by this chemical. The present study treated maternal rats with 5000 µg/kg body weight of BPA daily throughout the pregnancy period and then investigated the changes in ECM-producing cells, i.e., pericytes and folliculostellate (FS) cells, including their ECM production in the neonatal anterior pituitary at Day 1. We found that pericytes and their collagen synthesis reduced, consistent with the increase in the number of FS cells that expressed several ECM regulators-matrix metalloproteinase (MMP) 9 and the tissue inhibitors of metalloproteinase (TIMP) family. The relative MMP9/TIMP1 ratio was extremely high, indicating that the control of ECM homeostasis was unbalanced. Moreover, transmission electron microscopy showed the unorganized cell cluster in the BPA-treated group. This study revealed that although the mother received BPA at the "no observed adverse effect" level, alterations in ECM-producing cells as well as collagen and the related ECM balancing genes occurred in the neonatal anterior pituitary gland.

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.

Tumor-Associated Macrophages: New Horizons for Pituitary Adenoma Researches

Macrophages are one of the most common infiltrating immune cells and an essential component of tumor microenvironment. Macrophages and the soluble cytokines and chemokines produced play an important role in tumorigenesis, progression, invasion and metastasis in solid tumors. Despite the multiple studies in other solid tumors, there is little known about macrophages in pituitary adenomas. Recently, studies about pituitary adenoma-infiltrated macrophages have been emerging, including the immunohistochemical and immunophenotypic analysis of the pituitary adenomas and further studies into the mechanism of the crosstalk between macrophages and tumor cells in vivo and in vitro. These studies have offered us new insights into the polarization of macrophages and its role in tumorigenesis, progression and invasion of pituitary adenomas. This review describes the advances in the field of pituitary adenoma-infiltrated macrophages and the prospect of targeting macrophages as cancer therapy in pituitary adenoma.

Proteomic Analysis of the Human Anterior Pituitary Gland

The pituitary function is regulated by a complex system involving the hypothalamus and biological networks within the pituitary. Although the hormones secreted from the pituitary have been well studied, comprehensive analyses of the pituitary proteome are limited. Pituitary proteomics is a field of postgenomic research that is crucial to understand human health and pituitary diseases. In this context, we report here a systematic proteomic profiling of human anterior pituitary gland (adenohypophysis) using high-resolution Fourier transform mass spectrometry. A total of 2164 proteins were identified in this study, of which 105 proteins were identified for the first time compared with high-throughput proteomic-based studies from human pituitary glands. In addition, we identified 480 proteins with secretory potential and 187 N-terminally acetylated proteins. These are the first region-specific data that could serve as a vital resource for further investigations on the physiological role of the human anterior pituitary glands and the proteins secreted by them. We anticipate that the identification of previously unknown proteins in the present study will accelerate biomedical research to decipher their role in functioning of the human anterior pituitary gland and associated human diseases.

Characteristics of pericytes in diethylstilbestrol (DES)-induced pituitary prolactinoma in rats

Prolactinomas are the most common tumor of the human pituitary. They result in excessive prolactin secretion and important changes in the vasculature. Pericytes are perivascular cells associated with capillaries and have crucial roles in physiological and pathological neovascularization. We previously reported that pericytes produce type I and III collagens in the anterior pituitary of adult rats. In addition, pituitary pericytes contained well-developed cell organelles and actively synthesized collagens during early postnatal development. However, the characteristics of pericytes in pituitary tumors are unclear. In this study, we used diethylstilbestrol (DES)-treated rats as an animal model of prolactinoma. Using five common pericyte markers, more pericytes were observed in rats treated with DES for 3 months (prolactinoma) compared to the control. Transmission electron microscopy revealed that attached and semidetached pericytes exhibited active cell organelles. Moreover, we identified pericyte migration between capillaries. Although the fine structure of pituitary pericytes was active in prolactinoma, expressions of type I and III collagen mRNAs were greatly diminished. In sum, the characteristics and functions of pericytes were altered in pituitary tumors. This study is the first to clarify fine structural changes of pericytes in rat prolactinomas and improves our understanding of the function of pericytes under pathological conditions.

Tissue inhibitors of metalloproteinase-expressing cells in human anterior pituitary and pituitary adenoma

Extracellular matrix (ECM) is essential in tissue physiology and pathologic conditions such as tumorigenesis. It affects tumor cell behavior, proliferation, and metastasis. Pituitary adenomas differ in their clinical characteristics, including ECM deposition, and we recently reported that the characteristics of collagen-producing cells differed between control human anterior pituitary gland and pituitary adenomas. ECM deposition is not defined solely by production; degradation and maintenance are also important. Tissue inhibitors of metalloproteinases (TIMPs) help maintain ECM by inhibiting degradation caused by matrix metalloproteases. The present study attempted to characterize TIMP-expressing cells in the human anterior pituitary. Specimens of human pituitary adenomas and control pituitary were obtained during surgery, and in situ hybridization for TIMP1, TIMP2, TIMP3, and TIMP4, followed by immunohistochemistry, was used to characterize TIMP-expressing cells. TIMP expression exhibited a distinct pattern in the human anterior pituitary. Azan staining showed that fibrous matrix deposition varied among pituitary adenomas and that the area of fibrosis was associated with the number and number of types of TIMP3-expressing cells. These results suggest that TIMPs are important in the maintenance of ECM in human pituitary and that TIMP expressions are altered in fibrosis associated with pituitary adenoma.

Folliculostellate cell interacts with pericyte via TGFβ2 in rat anterior pituitary

The anterior pituitary gland comprises five types of endocrine cells plus non-endocrine cells including folliculostellate cells, endothelial cells, and capillary mural cells (pericytes). In addition to being controlled by the hypothalamic-pituitary-target organ axis, the functions of these cells are likely regulated by local cell and extracellular matrix (ECM) interactions. However, these complex interactions are not fully understood. We investigated folliculostellate cell-mediated cell-to-cell interaction. Using S100β-GFP transgenic rats, which express GFP in folliculostellate cells, we designed a three-dimensional cell culture to examine the effects of folliculostellate cells. Interestingly, removal of folliculostellate cells reduced collagen synthesis (Col1a1 and Col3a1). Because pericytes are important collagen-producing cells in the gland, we stained for desmin (a pericyte marker). Removal of folliculostellate cells resulted in fewer desmin-positive pericytes and less desmin mRNA. We then attempted to identify the factor mediating folliculostellate cell-pericyte interaction. RT-PCR and in situ hybridization revealed that the important profibrotic factor transforming growth factor beta-2 (TGFβ2) was specifically expressed in folliculostellate cells and that TGFβ receptor II was expressed in pericytes, endothelial cells, and parenchymal cells. Immunocytochemistry showed that TGFβ2 induced SMAD2 nuclear translocation in pericytes. TGFβ2 increased collagen synthesis in a dose-dependent manner. This action was completely blocked by TGFβ receptor I inhibitor (SB431542). Diminished collagen synthesis in folliculostellate cell-deficient cell aggregates was partially recovered by TGFβ2. TGFβ2-mediated folliculostellate cell-pericyte interaction appears to be essential for collagen synthesis in rat anterior pituitary. This finding sheds new light on local cell-ECM interactions in the gland.

Maintenance of the Extracellular Matrix in Rat Anterior Pituitary Gland: Identification of Cells Expressing Tissue Inhibitors of Metalloproteinases

The extracellular matrix (ECM) is important in creating cellular environments in tissues. Recent studies have demonstrated that ECM components are localized in anterior pituitary cells and affect cell activity. Thus, clarifying the mechanism responsible for ECM maintenance would improve understanding of gland function. Tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of matrix metalloproteinases and participate in ECM degradation. In this study, we investigated whether cells expressing TIMPs are present in rat anterior pituitary gland. Reverse transcription polymerase chain reaction was used to analyze expression of the TIMP family (TIMP1-4), and cells producing TIMPs in the gland were identified by using in situ hybridization. Expression of TIMP1, TIMP2, and TIMP3 mRNAs was detected, and the TIMP-expressing cells were located in the gland. The TIMP-expressing cells were also investigated by means of double-staining with in situ hybridization and immunohistochemical techniques. Double-staining revealed that TIMP1 mRNA was expressed in folliculostellate cells. TIMP2 mRNA was detected in folliculostellate cells, prolactin cells, and thyroid-stimulating hormone cells. TIMP3 mRNA was identified in endothelial cells, pericytes, novel desmin-immunopositive perivascular cells, and folliculostellate cells. These findings indicate that TIMP1-, TIMP2-, and TIMP3-expressing cells are present in rat anterior pituitary gland and that they are involved in maintaining ECM components.

Expression of Slug in S100β-protein-positive cells of postnatal developing rat anterior pituitary gland

Among heterogeneous S100β-protein-positive (S100β-positive) cells, star-like cells with extended cytoplasmic processes, the so-called folliculo-stellate cells, envelop hormone-producing cells or interconnect homophilically in the anterior pituitary. S100β-positive cells are known, from immunohistochemistry, to emerge from postnatal day (P) 10 and to proliferate and migrate in the parenchyma of the anterior pituitary with growth. Recent establishment of S100β-GFP transgenic rats expressing specifically green fluorescent protein (GFP) under the control of the S100β-promoter has allowed us to observe living S100β-positive cells. In the present study, we first confirmed that living S100β-positive cells in tissue cultures of S100β-GFP rat pituitary at P5 were present prior to P10 by means of confocal laser microscopy and that they proliferated and extended their cytoplasmic processes. Second, we examined the expression of the Snail-family zinc-finger transcription factors, Snail and Slug, to investigate the mechanism behind the morphological changes and the proliferation of S100β-positive cells. Interestingly, we detected Slug expression in S100β-positive cells and its increase together with development in the anterior pituitary. To analyze downstream of SLUG in S100β-positive cells, we utilized specific small interfering RNA for Slug mRNAs and observed that the expression of matrix metalloprotease (Mmp) 9, Mmp14 and chemokine Cxcl12 was down-regulated and that morphological changes and proliferation were decreased. Thus, our findings suggest that S100β-positive cells express Slug and that its expression is important for subsequent migration and proliferation.

Changes in fine structure of pericytes and novel desmin-immunopositive perivascular cells during postnatal development in rat anterior pituitary gland

Pericytes are perivascular cells associated with capillaries. We previously demonstrated that pericytes, identified by desmin immunohistochemistry, produce type I and III collagens in the anterior pituitary gland of adult rats. In addition, we recently used desmin immunoelectron microscopy to characterize a novel type of perivascular cell, dubbed a desmin-immunopositive perivascular cell, in the anterior pituitary. These two types of perivascular cells differ in fine structure. The present study attempted to characterize the morphological features of pituitary pericytes and novel desmin-immunopositive perivascular cells during postnatal development, in particular their role in collagen synthesis. Desmin immunostaining revealed numerous perivascular cells at postnatal day 5 (P5) and P10. Transmission electron microscopy showed differences in the fine structure of the two cell types, starting at P5. Pericytes had well-developed rough endoplasmic reticulum and Golgi apparatus at P5 and P10. The novel desmin-immunopositive perivascular cells exhibited dilated cisternae of rough endoplasmic reticulum at P5-P30. In addition, during early postnatal development in the gland, a number of type I and III collagen-expressing cells were observed, as were high expression levels of these collagen mRNAs. We conclude that pituitary pericytes and novel desmin-immunopositive perivascular cells contain well-developed cell organelles and that they actively synthesize collagens during the early postnatal period.

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.