Background/Purpose: Primary Sjögren’s syndrome (pSS) often results in dysfunction of the salivary glands (hyposalivation and xerostomia) and substantial decrease in patient quality of life. High label uptake on 68Ga-PSMA-11 PET-CT imaging identified a bilateral structure in the nasopharynx as a potential salivary gland (SG)-like additional ‘area of interest’, to be considered in conditions affecting the SGs. This structure was termed the ‘tubarial gland’. We aimed to better understand the histological and immunohistochemical position of the tubarial glands compared to other salivary glands and their potential role in hyposalivation, xerostomia development and swallowing problems in pSS.

Methods: Characterization of tubarial gland tissue was performed using standard immunohistological techniques, in comparison with tissue from the parotid, submandibular, sublingual, palatal and labial SGs.

Results: Acinar cells in SGs are responsible for saliva manufacture. Expression of the acinar cell-associated aquaporin-5 was detected in tubarial glands, in an apical location associated with polarized, secretory acinar cells. α-amylase expression, associated with SGs containing serous acinar cells, was not observed in tubarial glands. Expression of serous/serous demilune (SeD) acinar cell markers PIP and PRH2 was observed in tubarial acinar cell clusters, although SeD cells themselves were not clearly evident. Mucins within putative acinar cells, as inferred from alcian blue labeling, were detected in tubarial glands, similar to the sublingual, palatal and labial mucous-producing SGs. Expression of adrenergic receptor-β1 by acinar-like cells of the tubarial gland suggests ability to transduce a sympathetic neuronal signaling. Tubarial gland tissue also contained keratin 14⁺ (KRT14⁺) cells associated with acini and localized to a position suggestive of myoepithelial cells. In terms of ductal architecture, tubarial glands contained bi-layered KRT14⁺ Keratin7⁺ (KRT7⁺) large excretory ducts (similar to all other SGs), and simple/stratified squamous ducts, comprised of intermingled KRT14⁺ and KRT7⁺ cells (not previously reported, and similar to palatal, sublingual and labial SGs). These simple/stratified ductal cells in tubarial tissue expressed the sodium iodide transporter NIS, implying potential functionality ability to modify saliva ion content. No striated or intercalated ducts were observed in tubarial gland tissue, similar to the palatal SGs.

Conclusion: Based on histological analyses and in comparison to parotid, submandibular and sublingual palatal and labial salivary glands, tubarial glands resemble most convincingly palatal SGs. We draw this conclusion based on the acinar cell morphology (namely lack of notable serous demilune acinar cells, presence of mucins and expression of acinar cell marker proteins), and ductal compartment architecture (absence of intercalated or striated ducts, presence of squamous epithelial cells). Functional analysis is necessary to confirm the involvement of tubarial glands in moistening the pharyngeal mucosa. Imaging modalities incorporating the SGs may be critical to compiling a total picture of SG dysfunction in pSS.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-tubarial-glands-resemble-the-palatal-salivary-glands-based-on-further-histological-characterization-and-may-represent-an-organ-of-interest-in-primary-sjogrens-syndrome/