Granzyme A-producing type 1 innate lymphoid cells promote salivary secretion in the aged submandibular gland

Salivary gland function declines with age, contributing to periodontitis and aspiration pneumonia. However, the cellular mechanisms that preserve secretion during aging remain unclear.

Mice were stratified by aging stage, and saliva output and tissue histology were assessed. To infer cell-cell communication, regions surrounding lymphocyte clusters were microdissected and subjected to site-specific single-cell RNA sequencing. Epithelial cell responses were evaluated in a coculture system using a neutralizing antibody. Finally, physiological relevance was assessed by in vivo depletion, followed by quantification of changes in saliva secretion.

Saliva production was maintained or modestly increased during early aging stages and coincided with the emergence of lymphoid cell clusters. Single-cell and interactome analyses identified Gzma + ILC1 subsets enriched in aged lymphoid cluster regions and predicted crosstalk with epithelial cells via a GZMA-Pard3 axis. Upregulation of epithelial Aqp5 expression was confirmed in vitro. In vivo depletion of ILC1s in aged mice significantly reduced stimulated saliva output, indicating that local ILC1-derived GZMA supports secretory capacity.

Aged submandibular salivary glands accumulated ILC1s that promote epithelial function through a GZMA-dependent pathway and increased AQP5 expression, thereby maintaining salivary secretion during early aging. These findings identify ILC1s as regulators of salivary gland homeostasis and highlight the GZMA-Pard3 axis as a potential therapeutic target.