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Cholinergic epithelial cell with chemosensory traits in murine thymic medulla.

Panneck AR, Rafiq A, Schütz B, Soultanova A, Deckmann K, Chubanov V, Gudermann T, Weihe E, Krasteva-Christ G, Grau V, del Rey A, Kummer W - Cell Tissue Res. (2014)

Bottom Line: ChAT expression was confirmed by in situ hybridization.They did not express neuroendocrine (chromogranin A, PGP9.5) or thymocyte (CD3) markers but rather thymic epithelial (CK8, CK18) markers and were immunoreactive for components of the taste transduction cascade such as Gα-gustducin, transient receptor potential melastatin-like subtype 5 channel (TRPM5), and phospholipase Cβ2.This cell might participate in intrathymic infection-sensing mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, 35385, Giessen, Germany.

ABSTRACT
Specialized epithelial cells with a tuft of apical microvilli ("brush cells") sense luminal content and initiate protective reflexes in response to potentially harmful substances. They utilize the canonical taste transduction cascade to detect "bitter" substances such as bacterial quorum-sensing molecules. In the respiratory tract, most of these cells are cholinergic and are approached by cholinoceptive sensory nerve fibers. Utilizing two different reporter mouse strains for the expression of choline acetyltransferase (ChAT), we observed intense labeling of a subset of thymic medullary cells. ChAT expression was confirmed by in situ hybridization. These cells showed expression of villin, a brush cell marker protein, and ultrastructurally exhibited lateral microvilli. They did not express neuroendocrine (chromogranin A, PGP9.5) or thymocyte (CD3) markers but rather thymic epithelial (CK8, CK18) markers and were immunoreactive for components of the taste transduction cascade such as Gα-gustducin, transient receptor potential melastatin-like subtype 5 channel (TRPM5), and phospholipase Cβ2. Reverse transcription and polymerase chain reaction confirmed the expression of Gα-gustducin, TRPM5, and phospholipase Cβ2. Thymic "cholinergic chemosensory cells" were often in direct contact with medullary epithelial cells expressing the nicotinic acetylcholine receptor subunit α3. These cells have recently been identified as terminally differentiated epithelial cells (Hassall's corpuscle-like structures in mice). Contacts with nerve fibers (identified by PGP9.5 and CGRP antibodies), however, were not observed. Our data identify, in the thymus, a previously unrecognized presumptive chemosensitive cell that probably utilizes acetylcholine for paracrine signaling. This cell might participate in intrathymic infection-sensing mechanisms.

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Cholinergic medullary epithelial cells are not innervated. a Calcitonin gene-related peptide (CGRP)-immunoreactive varicose nerve fibre (arrows) next to a medullary blood vessel (V). However, the ChAT-eGFP-positive cell with an elongated process (arrowhead) is not approached by a nerve fibre. b Non-innervated ChAT-eGFP-positive cell (arrowhead) distant from a medullary protein gene product 9.5 (PGP9.5)-immunoreactive varicose nerve fibre (arrows). a Female aged 25 weeks. b Female aged 17 weeks. Bars 20 μm (a), 50 μm (b)
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Fig5: Cholinergic medullary epithelial cells are not innervated. a Calcitonin gene-related peptide (CGRP)-immunoreactive varicose nerve fibre (arrows) next to a medullary blood vessel (V). However, the ChAT-eGFP-positive cell with an elongated process (arrowhead) is not approached by a nerve fibre. b Non-innervated ChAT-eGFP-positive cell (arrowhead) distant from a medullary protein gene product 9.5 (PGP9.5)-immunoreactive varicose nerve fibre (arrows). a Female aged 25 weeks. b Female aged 17 weeks. Bars 20 μm (a), 50 μm (b)

Mentions: Chemosensory cells in respiratory epithelia are approached by peptidergic (substance P, calcitonin gene-related peptide [CGRP]) sensory nerve fibers (Finger et al. 2003; Krasteva et al. 2011; Saunders et al. 2014). In agreement with the observations reported previously by Bulloch et al. (1991), immunolabeling for CGRP revealed small CGRP-immunoreactive cortico-medullary cells and nerve terminals in septa and along blood vessels (Fig. 5a). These fibers did not ramify within the medulla nor did they approach ChAT-eGFP-positive cells (Fig. 5a). To test for possible innervation by non-peptidergic sensory nerve fibers, antibodies directed against the general neuroendocrine marker, protein gene product 9.5 (PGP9.5), were used. This antibody also labeled nerve fibers in septa and around blood vessels, but not in the vicinity of ChAT-eGFP-positive cells (Fig. 5b). As reported earlier by other groups (Brelińska et al. 2000; Bai et al. 2008), PGP9.5 immunoreactivity in the thymus was not restricted to nerve fibers but was also observed in several other cell types. ChAT-eGFP-positive cells represented a cell population distinct from these PGP9.5-immunoreactive thymic cells (Fig. 5b).Fig. 5


Cholinergic epithelial cell with chemosensory traits in murine thymic medulla.

Panneck AR, Rafiq A, Schütz B, Soultanova A, Deckmann K, Chubanov V, Gudermann T, Weihe E, Krasteva-Christ G, Grau V, del Rey A, Kummer W - Cell Tissue Res. (2014)

Cholinergic medullary epithelial cells are not innervated. a Calcitonin gene-related peptide (CGRP)-immunoreactive varicose nerve fibre (arrows) next to a medullary blood vessel (V). However, the ChAT-eGFP-positive cell with an elongated process (arrowhead) is not approached by a nerve fibre. b Non-innervated ChAT-eGFP-positive cell (arrowhead) distant from a medullary protein gene product 9.5 (PGP9.5)-immunoreactive varicose nerve fibre (arrows). a Female aged 25 weeks. b Female aged 17 weeks. Bars 20 μm (a), 50 μm (b)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig5: Cholinergic medullary epithelial cells are not innervated. a Calcitonin gene-related peptide (CGRP)-immunoreactive varicose nerve fibre (arrows) next to a medullary blood vessel (V). However, the ChAT-eGFP-positive cell with an elongated process (arrowhead) is not approached by a nerve fibre. b Non-innervated ChAT-eGFP-positive cell (arrowhead) distant from a medullary protein gene product 9.5 (PGP9.5)-immunoreactive varicose nerve fibre (arrows). a Female aged 25 weeks. b Female aged 17 weeks. Bars 20 μm (a), 50 μm (b)
Mentions: Chemosensory cells in respiratory epithelia are approached by peptidergic (substance P, calcitonin gene-related peptide [CGRP]) sensory nerve fibers (Finger et al. 2003; Krasteva et al. 2011; Saunders et al. 2014). In agreement with the observations reported previously by Bulloch et al. (1991), immunolabeling for CGRP revealed small CGRP-immunoreactive cortico-medullary cells and nerve terminals in septa and along blood vessels (Fig. 5a). These fibers did not ramify within the medulla nor did they approach ChAT-eGFP-positive cells (Fig. 5a). To test for possible innervation by non-peptidergic sensory nerve fibers, antibodies directed against the general neuroendocrine marker, protein gene product 9.5 (PGP9.5), were used. This antibody also labeled nerve fibers in septa and around blood vessels, but not in the vicinity of ChAT-eGFP-positive cells (Fig. 5b). As reported earlier by other groups (Brelińska et al. 2000; Bai et al. 2008), PGP9.5 immunoreactivity in the thymus was not restricted to nerve fibers but was also observed in several other cell types. ChAT-eGFP-positive cells represented a cell population distinct from these PGP9.5-immunoreactive thymic cells (Fig. 5b).Fig. 5

Bottom Line: ChAT expression was confirmed by in situ hybridization.They did not express neuroendocrine (chromogranin A, PGP9.5) or thymocyte (CD3) markers but rather thymic epithelial (CK8, CK18) markers and were immunoreactive for components of the taste transduction cascade such as Gα-gustducin, transient receptor potential melastatin-like subtype 5 channel (TRPM5), and phospholipase Cβ2.This cell might participate in intrathymic infection-sensing mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, 35385, Giessen, Germany.

ABSTRACT
Specialized epithelial cells with a tuft of apical microvilli ("brush cells") sense luminal content and initiate protective reflexes in response to potentially harmful substances. They utilize the canonical taste transduction cascade to detect "bitter" substances such as bacterial quorum-sensing molecules. In the respiratory tract, most of these cells are cholinergic and are approached by cholinoceptive sensory nerve fibers. Utilizing two different reporter mouse strains for the expression of choline acetyltransferase (ChAT), we observed intense labeling of a subset of thymic medullary cells. ChAT expression was confirmed by in situ hybridization. These cells showed expression of villin, a brush cell marker protein, and ultrastructurally exhibited lateral microvilli. They did not express neuroendocrine (chromogranin A, PGP9.5) or thymocyte (CD3) markers but rather thymic epithelial (CK8, CK18) markers and were immunoreactive for components of the taste transduction cascade such as Gα-gustducin, transient receptor potential melastatin-like subtype 5 channel (TRPM5), and phospholipase Cβ2. Reverse transcription and polymerase chain reaction confirmed the expression of Gα-gustducin, TRPM5, and phospholipase Cβ2. Thymic "cholinergic chemosensory cells" were often in direct contact with medullary epithelial cells expressing the nicotinic acetylcholine receptor subunit α3. These cells have recently been identified as terminally differentiated epithelial cells (Hassall's corpuscle-like structures in mice). Contacts with nerve fibers (identified by PGP9.5 and CGRP antibodies), however, were not observed. Our data identify, in the thymus, a previously unrecognized presumptive chemosensitive cell that probably utilizes acetylcholine for paracrine signaling. This cell might participate in intrathymic infection-sensing mechanisms.

Show MeSH