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Stellate Cell Networks in the Teleost Pituitary.

Golan M, Hollander-Cohen L, Levavi-Sivan B - Sci Rep (2016)

Bottom Line: In the pars intermedia, stellate cells were arranged around neuronal bundles and their processes extended into the pars distalis.Within the pars distalis, stellate cells formed close associations with FSH cells and, to a lesser degree, with GH and LH cells, suggesting differential paracrine regulation of the two gonadotrope populations.The production of follistatin by stellate cells further corroborates the notion of a paracrine role on FSH release.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

ABSTRACT
The folliculostellate cells of the mammalian pituitary are non-endocrine cells that are implicated in long-distance communication and paracrine signaling, but to date, these cells have yet to be characterized in teleosts. We found that the stellate cells of the teleost pituitary share many common attributes with mammalian folliculostellate cells. By labeling of stellate cells in live preparations of tilapia pituitaries we investigated their distribution, association with other endocrine cells and their anatomical and functional coupling. In the pars intermedia, stellate cells were arranged around neuronal bundles and their processes extended into the pars distalis. Within the pars distalis, stellate cells formed close associations with FSH cells and, to a lesser degree, with GH and LH cells, suggesting differential paracrine regulation of the two gonadotrope populations. The production of follistatin by stellate cells further corroborates the notion of a paracrine role on FSH release. We also found stellate cells to form gap junctions that enabled dye transfer to neighboring stellate cells, implicating that these cells form a large-scale network that connects distant parts of the pituitary. Our findings represent the first wide-scale study of stellate cells in teleosts and provide valuable information regarding their functional roles in pituitary function.

No MeSH data available.


Related in: MedlinePlus

Stellate cells are connected via gap junctions to form a large scale functional network.(a,b) Two examples of TEM images displaying junctional complexes (framed) between adjacent stellate cells. (c,d) 3-D reconstruction and volume rendering of stellate cells in tilapia pituitaries incubated without (c) or with (d) the gap junction blocker carbenoxolone (100 μm). Control shows stronger staining and deeper penetration. (e) Application of gap-junction blockers reduces dye penetration into the tissue in a time-dependent manner (n = 8). (f) Staining intensity is unaffected by the treatment in the first cell layer (10 μm) but staining of deeper layers is significantly decreased by application of gap-junction blockers (n = 8).
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f5: Stellate cells are connected via gap junctions to form a large scale functional network.(a,b) Two examples of TEM images displaying junctional complexes (framed) between adjacent stellate cells. (c,d) 3-D reconstruction and volume rendering of stellate cells in tilapia pituitaries incubated without (c) or with (d) the gap junction blocker carbenoxolone (100 μm). Control shows stronger staining and deeper penetration. (e) Application of gap-junction blockers reduces dye penetration into the tissue in a time-dependent manner (n = 8). (f) Staining intensity is unaffected by the treatment in the first cell layer (10 μm) but staining of deeper layers is significantly decreased by application of gap-junction blockers (n = 8).

Mentions: Since folliculostellate cells in mammals are known to communicate via gap junctions, we performed ultrastructural studies of tilapia pituitaries in an attempt to identify gap junctions on the membranes of the stellate cells. At the ultrastructural level, stellate cells were seen to form junctional complexes with adjacent stellate cells (Fig. 5a,b). We were not able to observe junctional complexes on juxtaposing membranes of the stellate cells and adjacent gonadotropes or somatotropes by TEM. To further establish the functional connectivity of the stellate cells population, we utilized their ability to transfer small molecules among themselves. The fluorescent dipeptide β-Ala-Lys-Nε-AMCA used to label the stellate cells is not only taken up into the cells by specific transporters, but is also small enough to be transferred between cells through gap junctions7. We used this trait to determine whether the stellate cells were functionally interconnected. We incubated pituitaries with the labeled dipeptide in medium containing the gap-junction inhibitor carbenoxolone, thus exposing the superficial layer of cells to the labeled dipeptide, and examined dye penetration into the tissue using confocal microscopy. When applied at 100 μM, carbenoxolone significantly inhibited penetration of the dye into the tissue (Fig. 5c,d). Incubation time also affected penetration of the dye into the tissue, with longer incubation times resulting in deeper penetration (Fig. 5e, n = 8). Labeling intensity decreased with depth but the rate of decrease was considerably more pronounced in tissue treated with gap-junction blocker, especially within the first 50 μm. In this region, the labeling intensity remained unchanged in control pituitaries whereas in pituitaries treated with gap-junction blocker, it decreased by over 50%. No difference in dye penetration was observed within the top layer of cells (~10 μm) (Fig. 5f).


Stellate Cell Networks in the Teleost Pituitary.

Golan M, Hollander-Cohen L, Levavi-Sivan B - Sci Rep (2016)

Stellate cells are connected via gap junctions to form a large scale functional network.(a,b) Two examples of TEM images displaying junctional complexes (framed) between adjacent stellate cells. (c,d) 3-D reconstruction and volume rendering of stellate cells in tilapia pituitaries incubated without (c) or with (d) the gap junction blocker carbenoxolone (100 μm). Control shows stronger staining and deeper penetration. (e) Application of gap-junction blockers reduces dye penetration into the tissue in a time-dependent manner (n = 8). (f) Staining intensity is unaffected by the treatment in the first cell layer (10 μm) but staining of deeper layers is significantly decreased by application of gap-junction blockers (n = 8).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834476&req=5

f5: Stellate cells are connected via gap junctions to form a large scale functional network.(a,b) Two examples of TEM images displaying junctional complexes (framed) between adjacent stellate cells. (c,d) 3-D reconstruction and volume rendering of stellate cells in tilapia pituitaries incubated without (c) or with (d) the gap junction blocker carbenoxolone (100 μm). Control shows stronger staining and deeper penetration. (e) Application of gap-junction blockers reduces dye penetration into the tissue in a time-dependent manner (n = 8). (f) Staining intensity is unaffected by the treatment in the first cell layer (10 μm) but staining of deeper layers is significantly decreased by application of gap-junction blockers (n = 8).
Mentions: Since folliculostellate cells in mammals are known to communicate via gap junctions, we performed ultrastructural studies of tilapia pituitaries in an attempt to identify gap junctions on the membranes of the stellate cells. At the ultrastructural level, stellate cells were seen to form junctional complexes with adjacent stellate cells (Fig. 5a,b). We were not able to observe junctional complexes on juxtaposing membranes of the stellate cells and adjacent gonadotropes or somatotropes by TEM. To further establish the functional connectivity of the stellate cells population, we utilized their ability to transfer small molecules among themselves. The fluorescent dipeptide β-Ala-Lys-Nε-AMCA used to label the stellate cells is not only taken up into the cells by specific transporters, but is also small enough to be transferred between cells through gap junctions7. We used this trait to determine whether the stellate cells were functionally interconnected. We incubated pituitaries with the labeled dipeptide in medium containing the gap-junction inhibitor carbenoxolone, thus exposing the superficial layer of cells to the labeled dipeptide, and examined dye penetration into the tissue using confocal microscopy. When applied at 100 μM, carbenoxolone significantly inhibited penetration of the dye into the tissue (Fig. 5c,d). Incubation time also affected penetration of the dye into the tissue, with longer incubation times resulting in deeper penetration (Fig. 5e, n = 8). Labeling intensity decreased with depth but the rate of decrease was considerably more pronounced in tissue treated with gap-junction blocker, especially within the first 50 μm. In this region, the labeling intensity remained unchanged in control pituitaries whereas in pituitaries treated with gap-junction blocker, it decreased by over 50%. No difference in dye penetration was observed within the top layer of cells (~10 μm) (Fig. 5f).

Bottom Line: In the pars intermedia, stellate cells were arranged around neuronal bundles and their processes extended into the pars distalis.Within the pars distalis, stellate cells formed close associations with FSH cells and, to a lesser degree, with GH and LH cells, suggesting differential paracrine regulation of the two gonadotrope populations.The production of follistatin by stellate cells further corroborates the notion of a paracrine role on FSH release.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

ABSTRACT
The folliculostellate cells of the mammalian pituitary are non-endocrine cells that are implicated in long-distance communication and paracrine signaling, but to date, these cells have yet to be characterized in teleosts. We found that the stellate cells of the teleost pituitary share many common attributes with mammalian folliculostellate cells. By labeling of stellate cells in live preparations of tilapia pituitaries we investigated their distribution, association with other endocrine cells and their anatomical and functional coupling. In the pars intermedia, stellate cells were arranged around neuronal bundles and their processes extended into the pars distalis. Within the pars distalis, stellate cells formed close associations with FSH cells and, to a lesser degree, with GH and LH cells, suggesting differential paracrine regulation of the two gonadotrope populations. The production of follistatin by stellate cells further corroborates the notion of a paracrine role on FSH release. We also found stellate cells to form gap junctions that enabled dye transfer to neighboring stellate cells, implicating that these cells form a large-scale network that connects distant parts of the pituitary. Our findings represent the first wide-scale study of stellate cells in teleosts and provide valuable information regarding their functional roles in pituitary function.

No MeSH data available.


Related in: MedlinePlus