Transient Receptor Potential Vanilloid 4 (TRPV4) in the Human Carotid Body

Figures

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  Scheme 1. Diagram of the location, innervation, and structure of the human carotid body. (A) Right-side view of the neck showing the carotid arterial system. (B) The carotid body (CB) is located at the carotid bifurcation, has ovoid morphology, and receives afferent innervation through a collateral nerve (de Casto’s nerve) of the carotid sinus nerve (sinus nerve or Hering’s nerve), branch of the glossopharyngeal nerve (IX). The somas of the afferent terminals are located in the petrosal ganglion (PG) of the IX. In addition, the BC receives efferent innervation through sympathetic sinus nerves (SSNs) that can be individual structures or form perivascular plexuses. SSNs are post-ganglionic sympathetic fibers whose somas are located in the superior sympathetic ganglion (SSG). CCA: common carotid artery, ACE: external carotid artery, ICA: internal carotid artery. (C) The structural unit of the carotid body is the glomic glomerulus that consists of type I cells arranged in contact with the capillaries, and type II cells that surround them. Type I cells are in contact with afferent and efferent nerve endings. In addition to the two main types of glomic cells, there are also precursor cells,…

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  Figure 1. Immunofluorescence-based detection of S100 protein (S100P) and neuron-specific enolase (NSE) in the human carotid body. S100P (a) was found in type II cells (green fluorescence) and NSE (b) in type I cells (red fluorescence). Merge of (c) and (d) was not detected therefore demonstrating that S100P and NSE are segregated and specifically identify type II and type I carotid body cells, respectively. (d) is an enlargement of (c). Blue fluorescence corresponds to the staining of the nuclei with DAPI. Scale bar in a is identical for a–c. Objective: 20×/0.75 oil; pinhole: 1; XY resolution: 156 nm; and Z resolution: 334 nm.

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  Figure 2. Immunofluorescence-based detection of TRPV4 in the human carotid body. TRPV4 was observed in some type I and type II cells throughout glomic glomeruli (yellow arrows). Merge (yellow in (c,d), (e,f), and (g,h)) of TRPV4 (green in (a) and (e)) with SYN (red in (b–d)) or NSE ((e,f) and (g,h)) demonstrate localization of TRPV in type I cells (yellow arrows); (d), (f), and (h) are details of (c), (e), and (g), respectively. Images of TRPV4 immunofluorescence in nerve terminals were also found ((h), white arrows). Blue fluorescence corresponds to the staining of the nuclei with DAPI. SYN: synaptophysin; NSE: neuron-specific enolase. Scale bar in a is identical for a-c and e-g; scale bar in d is identical for d and h. Objective: 20×/0.75 oil; pinhole: 1; XY resolution: 156 nm; and Z resolution: 334 nm.

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  Scheme 2. Schematic representation of a glomic glomerulus of the carotid body and the percentages of the area occupied by cells and nerves displaying TRPV4 immunofluorescence. Red color indicates positivity for TRPV4.

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  Figure 3. Immunofluorescence-based detection of TRPV4 in nerves of the human carotid body. TRPV4 (green in (a)) was detected in nerve fibres within the carotid body since merge of TRPV4 with NFP was found (red in (b)). Merge of TRPV4 with NFP ((c,d) and (e,f)) and NSE (g,h) is indicated with white arrows. (d), (f), and (h) are details of (c), (e), and (g), respectively. Blue fluorescence corresponds to the staining of the nuclei with DAPI. NFP: neurofilament proteins. NSE: neuron-specific enolase. Scale bar in a is identical for a-c and e-g; scale bar in d is identical for d and h. Objective: 20×/0.75 oil; pinhole: 1; XY resolution: 156 nm; and Z resolution: 334 nm.