Folliculostellate (FS) Cells
- Thread starter hotblack
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V.R.T.
Senior Member (Voting Rights)
These cells, their function w.r.t. cognition and the links to IFNy, innate immunity etc are really interesting. But based on these marker gene associations, would we not have seen a clear HLA signal in DecodeME if they were involved?
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hotblack
Senior Member (Voting Rights)
I don’t think we’ll see hits for every gene for every protein or receptor for every cell involved in whatever process we uncover. It’s also worth saying these FS cells aren’t showing high expression, just some, it’s that and the patterns and differences which I’m assuming probably account for some of the behaviours seen. Would be interested in what others think though.
There may of course be no relevance here ofc. I’m just going through some mechanisms, learning what I can there’s a few ways I can see them being involved but it doesn’t necessarily mean they are! It’s interesting though and I hope these posts are bringing some others interested along on the journey.
hotblack
Senior Member (Voting Rights)
Hopefully this next bit will help with the wider picture and help explain a bit we’ve covered how these calcium waves propagate through the network but what triggers those calcium waves and what could alter how of when they are?
First Il-6. This confused me a lot as there are clear claims that FS cells produce IL-6. But looking at the papers this is not in humans, rather/mouse models.
Production of Interleukin-6 by Folliculo-Stellate Cells of the Anterior Pituitary Gland in a Histiotypic Cell Aggregate Culture System, 2008, Vankelecom et al
Web | DOI | PDF | Neuroendocrinology
Rather than quoting lots of papers I’ll try to cover what I think the situation is how I reconciled it in my head and others can judge.
Accessing live human pituitary tissue presents understandable challenges. There are studies from autopsies/tumours but there are technical issues around staining and tissue degradation and tumours behave differently with different sources of IL-6. And things just moved on from tissue sampling to RNA sequencing.
Human protein atlas data for Il6 for the pituitary shows the following
Average nTPM: 39.0
Samples: 313
Max nTPM: 736.5
Min nTPM: 0.0
Std nTPM: 97.8
Median nTPM: 4.1
And perhaps more convincingly single cell RNA expression shows this is almost entirely in Pituicytes/FSCs rather than lactotrophs, somatotrophs, macrophages, etc.
Of note the data doesn’t distinguish between anterior and posterior, so we cannot be sure it’s pituicytes or FS cells or both and there is quite a range of values in the samples. But it seems consistent with the claims in other papers and the findings in rodents that FS cells produce IL-6.
First Il-6. This confused me a lot as there are clear claims that FS cells produce IL-6. But looking at the papers this is not in humans, rather/mouse models.
Production of Interleukin-6 by Folliculo-Stellate Cells of the Anterior Pituitary Gland in a Histiotypic Cell Aggregate Culture System, 2008, Vankelecom et al
Web | DOI | PDF | Neuroendocrinology
Rather than quoting lots of papers I’ll try to cover what I think the situation is how I reconciled it in my head and others can judge.
Accessing live human pituitary tissue presents understandable challenges. There are studies from autopsies/tumours but there are technical issues around staining and tissue degradation and tumours behave differently with different sources of IL-6. And things just moved on from tissue sampling to RNA sequencing.
Human protein atlas data for Il6 for the pituitary shows the following
Average nTPM: 39.0
Samples: 313
Max nTPM: 736.5
Min nTPM: 0.0
Std nTPM: 97.8
Median nTPM: 4.1
And perhaps more convincingly single cell RNA expression shows this is almost entirely in Pituicytes/FSCs rather than lactotrophs, somatotrophs, macrophages, etc.
Of note the data doesn’t distinguish between anterior and posterior, so we cannot be sure it’s pituicytes or FS cells or both and there is quite a range of values in the samples. But it seems consistent with the claims in other papers and the findings in rodents that FS cells produce IL-6.
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V.R.T.
Senior Member (Voting Rights)
IL-6 has come up a few times in the research no? I think in long covid in particular
hotblack
Senior Member (Voting Rights)
I’m not sure! You have a far better memory of these things. And the more I look at some of this the more possibilities I see but also the less sure of some other things I become!
Some people/papers talk about the pituitary being at the crossroads of the immune, hormone and nervous systems so I wondered if there was something here. Maybe it could help explain or tie up with the prolactin findings but I’m not sure tbh.
V.R.T.
Senior Member (Voting Rights)
It's too short a term to search on S4ME but I think raised IL-6 was the basis for the tocilizumab trial in the UK and has been seen up in some long covid studies.
[Edit: Tocilizumab study:
]
It does seem like all this could tie together really well. No guarantee that it means anything ofc but it would answer a lot of questions about the quirks of ME/CFS symptoms if the answer (or part of it) was to do with FS cells and the pituitary.
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hotblack
Senior Member (Voting Rights)
It does and it would. You’re not the only one who sees things everywhere 
For instance there is this paper which would maybe tie in with some innate immune angles (LPS, IL-6, TLR4, tick, tick, tick). But human protein atlas data shows it’s mainly macrophages which express CD14 in the pituitary not FS cells and there’s no sign of TLR4. So maybe it’s just not transferable to humans?
Lipopolysaccharide Directly Stimulates the Intrapituitary Interleukin-6 Production by Folliculostellate Cells via Specific Receptors and the p38α Mitogen-Activated Protein Kinase/Nuclear Factor-κB Pathway**Supported by a grant from the DFG: Sta 285/7–3., 2000, Lohrer et al
Web | DOI | Endocrinology
For instance there is this paper which would maybe tie in with some innate immune angles (LPS, IL-6, TLR4, tick, tick, tick). But human protein atlas data shows it’s mainly macrophages which express CD14 in the pituitary not FS cells and there’s no sign of TLR4. So maybe it’s just not transferable to humans?Lipopolysaccharide Directly Stimulates the Intrapituitary Interleukin-6 Production by Folliculostellate Cells via Specific Receptors and the p38α Mitogen-Activated Protein Kinase/Nuclear Factor-κB Pathway**Supported by a grant from the DFG: Sta 285/7–3., 2000, Lohrer et al
Lohrer, P.; Gloddek, J.; Nagashima, A. Carbia; Korali, Z.; Hopfner, U.; Pereda, M. Paez; Arzt, E.; Stalla, G. K.; Renner, U.
Web | DOI | Endocrinology
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hotblack
Senior Member (Voting Rights)
Thanks for the study info @V.R.T. Looks like they’re maybe going the autoimmunity line of thinking? What I was wondering here was more like a localised messenger role. It’s not that the FS cells produce loads of cytokines that would cause systemic issues. More they seem to stimulate release of hormones. Another old/rodent paper
Interleukin 6 possibly induced by interleukin 1β in the pituitary gland stimulates the release of gonadotropins and prolactin, 1990, Yamaguchi et al
Web | DOI | Acta Endocrinologica
Interleukin 6 possibly induced by interleukin 1β in the pituitary gland stimulates the release of gonadotropins and prolactin, 1990, Yamaguchi et al
Web | DOI | Acta Endocrinologica
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hotblack
Senior Member (Voting Rights)
This was also interesting. I’m finding most mechanistic studies are not in humans. Because of the challenges getting healthy live human pituitary tissue most experiments appear to be in rodent models. To try to deal with some of the differences this study inserts human gene fragments into rodent cell lines.
Human Prolactin Gene Promoter Regulation by Estrogen: Convergence with Tumor Necrosis Factor-α Signaling, 2007, Adamson et al
Web | DOI | PMC | PDF | Endocrinology
So I think in this paper they built upon some other papers of the time and found (1) estradiol increased activation of the prolactin gene promoter (2) identified a section of the dna that appeared to be responsible for this (3) found that estradiol and TNFα worked together at this section and (4) that disrupting this section stopped the effects.
Here’s the figure showing the individual and combined effects over time
Human Prolactin Gene Promoter Regulation by Estrogen: Convergence with Tumor Necrosis Factor-α Signaling, 2007, Adamson et al
Web | DOI | PMC | PDF | Endocrinology
So I think in this paper they built upon some other papers of the time and found (1) estradiol increased activation of the prolactin gene promoter (2) identified a section of the dna that appeared to be responsible for this (3) found that estradiol and TNFα worked together at this section and (4) that disrupting this section stopped the effects.
Here’s the figure showing the individual and combined effects over time
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hotblack
Senior Member (Voting Rights)
So again moving to protein atlas data, what do we see in human tissue samples (noting this a measure of normalised transcript expression, not a measure of what’s always happening in a cell, but it can give us an idea of what a cell is likely capable of).
Data doesn’t support any ideas that TNF-alpha is produced locally by FS cells or lactotrophs, so any signal is coming from somewhere else. But the values for NFKB1 (along with RIPK1 and ADAM10) seems to support the findings of the paper that shows TNF-alpha can enhance production of prolactin in lactotrophs, either alone or in concert with estrogen. Because those are used by cell machinery in TNF-alpha related signalling and processing (although not exclusively, they are also used in other things). So human lactotrophs seem to have the machinery to respond to TNF-alpha signals.
Perhaps interestingly, in the data lactotrophs don’t show much in the way of TNF-Alpha receptor (TNFRSF1A or TNFRSF1B) expression though. And the precursor paper to the above (Tumor Necrosis Factor-α Activates the Human Prolactin Gene Promoter via Nuclear Factor-κB Signaling, 2006, Friedrichsen et al) particular focused on this as a route and receptor activity would be expected for direct interaction.
This is where FS cells may come in as they posses the lot. They appear to have the machinery to process and signal but also the receptors. This raises the possibility that FS cells could act as intermediaries in some way.
Data doesn’t support any ideas that TNF-alpha is produced locally by FS cells or lactotrophs, so any signal is coming from somewhere else. But the values for NFKB1 (along with RIPK1 and ADAM10) seems to support the findings of the paper that shows TNF-alpha can enhance production of prolactin in lactotrophs, either alone or in concert with estrogen. Because those are used by cell machinery in TNF-alpha related signalling and processing (although not exclusively, they are also used in other things). So human lactotrophs seem to have the machinery to respond to TNF-alpha signals.
Perhaps interestingly, in the data lactotrophs don’t show much in the way of TNF-Alpha receptor (TNFRSF1A or TNFRSF1B) expression though. And the precursor paper to the above (Tumor Necrosis Factor-α Activates the Human Prolactin Gene Promoter via Nuclear Factor-κB Signaling, 2006, Friedrichsen et al) particular focused on this as a route and receptor activity would be expected for direct interaction.
This is where FS cells may come in as they posses the lot. They appear to have the machinery to process and signal but also the receptors. This raises the possibility that FS cells could act as intermediaries in some way.
Code:
HPA SINGLE-CELL GENE EXPRESSION SUMMARY (Expression Metric: NCPM)
=======================================================================
=========
gene name Category cell type ncpm
S100B Identity / Lineage Marker pituicytes/fscs 64.50
CD14 Identity / Lineage Marker pituicytes/fscs 1.30
PTPRC Identity / Lineage Marker pituicytes/fscs 0.80
SOX2 Identity / Lineage Marker pituicytes/fscs 0.50
NFKBIA Negative Feedback pituicytes/fscs 41.40
TNFAIP3 Negative Feedback pituicytes/fscs 3.10
NFKB1 Receptor Signalling pituicytes/fscs 131.40
RIPK1 Receptor Signalling pituicytes/fscs 37.70
RELA Receptor Signalling pituicytes/fscs 18.40
TRADD Receptor Signalling pituicytes/fscs 6.80
TRAF2 Receptor Signalling pituicytes/fscs 4.70
LTA TNF Ligand (Production) pituicytes/fscs 0.00
LTB TNF Ligand (Production) pituicytes/fscs 0.00
TNF TNF Ligand (Production) pituicytes/fscs 0.00
ADAM17 TNF Processing / Shedding pituicytes/fscs 223.20
ADAM10 TNF Processing / Shedding pituicytes/fscs 89.60
TNFRSF1A TNF Receptor pituicytes/fscs 93.40
TNFRSF1B TNF Receptor pituicytes/fscs 4.20
Code:
HPA SINGLE-CELL GENE EXPRESSION SUMMARY (Expression Metric: NCPM)
================================================================================
gene name Category cell type ncpm
S100B Identity / Lineage Marker lactotrophs 2.10
CD14 Identity / Lineage Marker lactotrophs 1.50
PTPRC Identity / Lineage Marker lactotrophs 1.10
SOX2 Identity / Lineage Marker lactotrophs 0.00
NFKBIA Negative Feedback lactotrophs 15.60
TNFAIP3 Negative Feedback lactotrophs 0.50
NFKB1 Receptor Signalling lactotrophs 113.10
RIPK1 Receptor Signalling lactotrophs 46.00
TRAF2 Receptor Signalling lactotrophs 15.50
RELA Receptor Signalling lactotrophs 7.20
TRADD Receptor Signalling lactotrophs 5.50
LTA TNF Ligand (Production) lactotrophs 0.00
LTB TNF Ligand (Production) lactotrophs 0.00
TNF TNF Ligand (Production) lactotrophs 0.00
ADAM10 TNF Processing / Shedding lactotrophs 154.60
ADAM17 TNF Processing / Shedding lactotrophs 83.10
TNFRSF1A TNF Receptor lactotrophs 8.20
TNFRSF1B TNF Receptor lactotrophs 0.90
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hotblack
Senior Member (Voting Rights)
And then there’s this, something that ties together calcium waves and the coordinated pulses of the earlier reviews with the cytokines above? More to think about although for now my brain is fried. But the result could be some sort of negative feedback loop or maybe just a noisy and less coordinated network when? Again this is in rodents, but some interesting possibilities!
Tumor Necrosis Factor-α-Induced Anterior Pituitary Folliculostellate TtT/GF Cell Uncoupling Is Mediated by Connexin 43 Dephosphorylation, 2007, Meilleur et al
https://academic.oup.com/endo/article/148/12/5913/2501831']Web | DOI | PDF | Endocrinology
Human protein atlas data shows GJA1 (which encodes connexin 43/Cx43) is present in FSCs and vascular endothelial cells in the pituitary.
Tumor Necrosis Factor-α-Induced Anterior Pituitary Folliculostellate TtT/GF Cell Uncoupling Is Mediated by Connexin 43 Dephosphorylation, 2007, Meilleur et al
https://academic.oup.com/endo/article/148/12/5913/2501831']Web | DOI | PDF | Endocrinology
Human protein atlas data shows GJA1 (which encodes connexin 43/Cx43) is present in FSCs and vascular endothelial cells in the pituitary.
hotblack
Senior Member (Voting Rights)
One aspect that perhaps needs highlighting from the earlier paper on gap junctions and calcium waves and also supported by others is that the connections are not just between FS cells but also between FS cells and hormone producing cells, particularly lactotrophs (PRL) and somatotrophs (GH). As an aside, I understand lactotrophs and somatotrophs also share a developmental lineage.
Cell-to-cell communication in the anterior pituitary: evidence for gap junction-mediated exchanges between endocrine cells and folliculostellate cells., 1996, Morand et al
Web | DOI | Endocrinology
Putting this together with earlier papers we have at least two potential routes of involvement of FS cells in influencing hormone production and of specific interest here, lactotrophs.
Firstly direct cell to cell communication through gap junctions. These allow ions and small molecules to directly pass between connected cells. Secondly there is local cytokine signalling, including the outlined role of IL-6.
The two routes may work over different timescales and are not necessarily independent either. Changes in FS cells and the networks they create could potentially affect both. And changes to the local environment (like an influx of IL-1B or TNF-alpha) could affect the network itself.
I hope you’ve enjoyed my Fred talk so far. It’s a bit like a Ted talk but from the west coast of England rather than the US.
Cell-to-cell communication in the anterior pituitary: evidence for gap junction-mediated exchanges between endocrine cells and folliculostellate cells., 1996, Morand et al
Web | DOI | Endocrinology
Putting this together with earlier papers we have at least two potential routes of involvement of FS cells in influencing hormone production and of specific interest here, lactotrophs.
Firstly direct cell to cell communication through gap junctions. These allow ions and small molecules to directly pass between connected cells. Secondly there is local cytokine signalling, including the outlined role of IL-6.
The two routes may work over different timescales and are not necessarily independent either. Changes in FS cells and the networks they create could potentially affect both. And changes to the local environment (like an influx of IL-1B or TNF-alpha) could affect the network itself.
I hope you’ve enjoyed my Fred talk so far. It’s a bit like a Ted talk but from the west coast of England rather than the US.
I’ve been eagerly waiting for the results of this trial, as at some point I wanted to participate in it so much. I hope they answer my recent email about estimated timeline for preliminary findings (the recruitment of patients was stopped a year ago).
hotblack
Senior Member (Voting Rights)
Another paper I had open in a tab which I think I may have half referenced but is probably worth posting is this
Tumor Necrosis Factor-α Activates the Human Prolactin Gene Promoter via Nuclear Factor-κB Signaling, 2006, Friedrichsen et al
Abstract
Pituitary function has been shown to be regulated by an increasing number of intrapituitary factors, including cytokines. Here we show that the important cytokine TNF-α activates prolactin gene transcription in pituitary GH3 cells stably expressing luciferase under control of 5 kb of the human prolactin promoter.
Similar regulation of the endogenous rat prolactin gene by TNF-α in GH3 cells was confirmed using real-time PCR. Luminescence microscopy revealed heterogeneous dynamic response patterns of promoter activity in individual cells.
In GH3 cells treated with TNF-α, Western blot analysis showed rapid inhibitory protein κB (IκBα) degradation and phosphorylation of p65. Confocal microscopy of cells expressing fluorescence-labeled p65 and IκBα fusion proteins showed transient cytoplasmic-nuclear translocation and subsequent oscillations in p65 localization and confirmed IκBα degradation.
This was associated with increased nuclear factor κB (NF-κB)-mediated transcription from an NF-κB-responsive luciferase reporter construct. Disruption of NF-κB signaling by expression of dominant-negative variants of IκB kinases or truncated IκBα abolished TNF-α activation of the prolactin promoter, suggesting that this effect was mediated by NF-κB.
TNF-α signaling was found to interact with other endocrine signals to regulate prolactin gene expression and is likely to be a major paracrine modulator of lactotroph function.
Web | DOI | PMC | PDF | Endocrinology
Tumor Necrosis Factor-α Activates the Human Prolactin Gene Promoter via Nuclear Factor-κB Signaling, 2006, Friedrichsen et al
Friedrichsen, Sönke; Harper, Claire V.; Semprini, Sabrina; Wilding, Michael; Adamson, Antony D.; Spiller, Dave G.; Nelson, Glyn; Mullins, John J.; White, Michael R. H.; Davis, Julian R. E.
Abstract
Pituitary function has been shown to be regulated by an increasing number of intrapituitary factors, including cytokines. Here we show that the important cytokine TNF-α activates prolactin gene transcription in pituitary GH3 cells stably expressing luciferase under control of 5 kb of the human prolactin promoter.
Similar regulation of the endogenous rat prolactin gene by TNF-α in GH3 cells was confirmed using real-time PCR. Luminescence microscopy revealed heterogeneous dynamic response patterns of promoter activity in individual cells.
In GH3 cells treated with TNF-α, Western blot analysis showed rapid inhibitory protein κB (IκBα) degradation and phosphorylation of p65. Confocal microscopy of cells expressing fluorescence-labeled p65 and IκBα fusion proteins showed transient cytoplasmic-nuclear translocation and subsequent oscillations in p65 localization and confirmed IκBα degradation.
This was associated with increased nuclear factor κB (NF-κB)-mediated transcription from an NF-κB-responsive luciferase reporter construct. Disruption of NF-κB signaling by expression of dominant-negative variants of IκB kinases or truncated IκBα abolished TNF-α activation of the prolactin promoter, suggesting that this effect was mediated by NF-κB.
TNF-α signaling was found to interact with other endocrine signals to regulate prolactin gene expression and is likely to be a major paracrine modulator of lactotroph function.
Web | DOI | PMC | PDF | Endocrinology