Folliculo-stellate Cells: Paracrine Communicators in the Anterior Pituitary

Morris, John F.

doi:10.2174/1876528901104010077

Cited by 21 publications

(27 citation statements)

References 147 publications

(191 reference statements)

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“…It is highly plausible that this intercellular interplay is modulated by folliculostellate cells. Folliculostellate cells are nonendocrine, star-shaped, glial-like cells, which organize themselves into follicles and communicate with each other and with endocrine cells through gap-junctions, generating a 3-dimensional network for the transmission of signals throughout the pituitary to coordinate its function [9], [63], [64], [65]. These cells produce and secrete a number of paracrine factors, which are known to influence both gonadotropes and lactotropes.…”

Section: Intercellular Contacts Underlying Paracrine Regulation Of Pimentioning

confidence: 99%

Intrapituitary mechanisms underlying the control of fertility: key players in seasonal breeding

Tortonese

2016

Domestic Animal Endocrinology

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Recent studies have shown that, in conjunction with dynamic changes in the secretion of GnRH from the hypothalamus, paracrine interactions within the pituitary gland play an important role in the regulation of fertility during the annual reproductive cycle. Morphological studies have provided evidence for close associations between gonadotropes and lactotropes and gap junction coupling between these cells in a variety of species. The physiological significance of this cellular interaction was supported by subsequent studies revealing the expression of prolactin receptors in both the pars distalis and pars tuberalis regions of the pituitary. This cellular interaction is critical for adequate gonadotropin output because, in the presence of dopamine, prolactin can negatively regulate the LH response to GnRH. Receptor signaling studies showed that signal convergence at the level of protein kinase C and phospholipase C within the gonadotrope underlies the resulting inhibition of LH secretion. Although this is a conserved mechanism present in all species studied so far, in seasonal breeders such as the sheep and the horse, this mechanism is regulated by photoperiod, as it is only apparent during the long days of spring and summer. At this time of year, the nonbreeding season of the sheep coincides with the breeding season of the horse, indicating that this inhibitory system plays different roles in short- and long-day breeders. Although in the sheep, it contributes to the complete suppression of the reproductive axis, in the horse, it is likely to participate in the fine-tuning of gonadotropin output by preventing gonadotrope desensitization. The photoperiodic regulation of this inhibitory mechanism appears to rely on alterations in the folliculostellate cell population. Indeed, electron microscopic studies have recently shown increased folliculostellate cell area together with upregulation of their adherens junctions during the spring and summer. The association between gonadotropes and lactotropes could also underlie an interaction between the gonadotropic and prolactin axes in the opposite direction. In support of this alternative, a series of studies have demonstrated that GnRH stimulates prolactin secretion in sheep through a mechanism that does not involve the mediatory actions of LH or FSH and that this stimulatory effect of GnRH on the prolactin axis is seasonally regulated. Collectively, these findings highlight the importance of intercellular communications within the pituitary in the control of gonadotropin and prolactin secretion during the annual reproductive cycle in seasonal breeders.

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Section: Intercellular Contacts Underlying Paracrine Regulation Of Pimentioning

confidence: 99%

Intrapituitary mechanisms underlying the control of fertility: key players in seasonal breeding

Tortonese

2016

Domestic Animal Endocrinology

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“…FS cells are star-shaped, electrically excitable, follicle-forming cells in the pituitary gland that secrete an array of paracrine and juxtacrine factors (10). FS cells were first identified by electron microscopy (EM) as non-endocrine, agranular cells.…”

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confidence: 99%

Ultrastructural Changes in Lactotrophs and Folliculo‐Stellate Cells in the Ovine Pituitary during the Annual Reproductive Cycle

Christian

Imirtziadis

Tortonese

2015

J Neuroendocrinology

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In seasonal mammals living in temperate zones, photoperiod regulates prolactin secretion, such that prolactin plasma concentrations peak during the summer months and are lowest during the winter. In sheep, a short-day breeder, circulating prolactin has important modulatory effects on the reproductive system via inhibitory actions on pituitary gonadotrophs and hypothalamic gonadotrophin-releasing hormone release. The exact cellular mechanisms that account for the chronic hypersecretion of prolactin during the summer is not known, although evidence supports an intrapituitary mechanism regulated by melatonin. Folliculo-stellate (FS) cells are non-endocrine cells that play a crucial role in paracrine communication within the pituitary and produce factors controlling prolactin and gonadotrophin release. The present study examined the morphology of the FS and lactotroph cell populations and their distribution in the sheep pituitary during the annual reproductive cycle. Ovine pituitary glands were collected in the winter (breeding season; BS) and summer (nonbreeding season; NBS) and were prepared for quantitative electron microscopy to assess the effects of season on FS and lactotroph cell density, morphology and distribution, as well as on junctional contacts between cells. It was found that lactotrophs in the NBS are larger in size and contain more numerous PRL granules than lactotrophs in the BS. FS cells were also larger in the NBS compared to BS and showed altered morphology such that, in the BS, long cell processes surrounded clusters of adjacent secretory cells. Although no significant change in the number of junctions was observed between lactotrophs and FS cells, or lactotrophs and gonadotrophs, there was a significant increase in the number of adherens junctions between lactotrophs and between FS cells. These findings demonstrate seasonal plasticity in the morphology of lactotrophs and FS cells that reflect changes in PRL secretion.

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“…For example, they express the S‐100 protein , particularly the β isoform . FS cells do not secrete hormones, although they themselves constitute a source of many cytokines and growth factors that regulate anterior pituitary endocrine activity . FS cells generally exhibit a stellate shape with cytoplasmic processes surrounding the endocrine cells and organising the pituitary parenchyma in incomplete follicles .…”

mentioning

confidence: 99%

Biphasic Effect of Basic Fibroblast Growth Factor on Anterior Pituitary Folliculostellate TtT/GF Cell Coupling, and Connexin 43 Expression and Phosphorylation

Vitale

Barry

2015

J Neuroendocrinology

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Basic fibroblast growth factor (bFGF) is a mitogenic and differentiating cytokine. In the anterior pituitary, folliculostellate (FS) cells constitute the major source of bFGF. bFGF affects endocrine cell proliferation and secretion in the anterior pituitary. In addition, bFGF increases its own expression by acting directly on FS cells. FS cell Cx43-mediated gap junction intercellular communication allows the establishment of an intrapituitary network for the transmission of information. In the present study, we assessed how bFGF regulates FS cell coupling. Time course studies were carried out on the FS cell line TtT/GF. Short-term bFGF treatment induced a transient cell uncoupling and the phosphorylation in Ser368 of membrane-bound Cx43 without modifying Cx43 levels. We demonstrated the involvement of the protein kinase C (PKC) isoform α in the phosphorylation of Cx43 in S368. Moreover, we showed that bFGF induced PKCα activation by stimulating its expression, phosphorylation and association with the plasma membrane. The long-term incubation with bFGF increased TtT/GF cell coupling, total Cx43 levels and Cx43 accumulation at the cell membrane of cytoplasmic projections. The Cx43 level increase was a result of the stimulation of Cx43 gene transcription as mediated by the extracellular-regulated kinase 1/2 signalling pathway. Taken together, the data show that bFGF modulates TtT/GF cell coupling by activating different pathways that lead to opposite effects on Cx43 phosphorylation and expression depending on the duration of the exposure of the cells to bFGF. A short-term bFGF exposure reduces cell-to-cell communication as a mean of desynchronising FS cells. By contrast, long-term exposure to bFGF enhances cell-to-cell communication and facilitates coordination among FS cells.

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Folliculo-stellate Cells: Paracrine Communicators in the Anterior Pituitary

Cited by 21 publications

References 147 publications

Intrapituitary mechanisms underlying the control of fertility: key players in seasonal breeding

Intrapituitary mechanisms underlying the control of fertility: key players in seasonal breeding

Ultrastructural Changes in Lactotrophs and Folliculo‐Stellate Cells in the Ovine Pituitary during the Annual Reproductive Cycle

Biphasic Effect of Basic Fibroblast Growth Factor on Anterior Pituitary Folliculostellate TtT/GF Cell Coupling, and Connexin 43 Expression and Phosphorylation

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