Highlights of Tuft Cells in Mouse and Human Salivary Glands.

Tuft cells (TCs) are rare chemosensory epithelial cells that regulate mucosal homeostasis in multiple organs, but their role in salivary gland (SG) biology remains poorly defined. This study aimed to define TC structure in mice submandibular glands (SMGs), determine how TC loss affects gland organization and function, and evaluate whether TC abundance in human minor SGs is associated with Sjögren's disease (SjD) features. Specifically, TC ultrastructure and ductal localization were characterized in female and male C57BL/6J mouse SMGs by transmission electron microscopy and immunostaining. Wild-type and C57BL/6J-Pou2f3-/- (TC-deficient mouse strain) SMGs were analyzed by histology and bulk RNA-seq, and salivary function was assessed by saliva flow and proteomics. Human minor SG biopsies from SjD and non-Sjögren sicca (nSjD) patients were analyzed by immunostaining and Poisson regression. In mice SMGs, TCs showed conserved ultrastructural features and localization in both sexes. TC loss was associated with marked sex-biased transcriptome remodeling, morphological disruption, and altered saliva quantity and quality. In humans, TC counts differed between nSjD and SjD groups and were associated with salivary flow, serologic status, and histopathologic features. These findings support a role for TCs in SG epithelial integrity and suggest TC abundance as a candidate biomarker of SG dysfunction.