Impact of NFAT5 conditional knockout on murine salivary glands

Salivary glands contribute to oral health by secreting saliva, in which aquaporin-5 (AQP5), a transmembrane water channel, plays a major role by allowing water movement across acinar cells. The role of nuclear factor of activated T-cells 5 (NFAT5) was investigated in salivary gland physiology using NFAT5 conditional knockout mice. Conditional NFAT5 wildtype and knockout mice were generated and genotyped. Saliva secretion was measured upon pilocarpine stimulation and saliva osmolality determined with an osmometer. Tissue sections were subjected to AQP5 and cleaved-caspase-3 immunostaining, and TUNEL staining. Salivary gland transcriptome was determined by RNA-sequencing. NFAT5 KO mice showed significantly reduced pilocarpine-stimulated salivary flow and increased salivary osmolality compared to NFAT5 wild-type mice. Aquaporin-5 immunostaining revealed a loss of apical selectivity with increased cytoplasmic localization in submandibular glands from NFAT5 knockout mice compared to NFAT5 wild-type mice, but not in parotid glands. Apoptosis was significantly increased in both acinar and ductal structures in submandibular glands NFAT5 knockout mice compared to NFAT5 wild-type mice. Transcriptome analysis by bulk RNA-sequencing revealed 2,086 differentially expressed genes, with up regulation of some transmembrane transporters involved in the mechanism responsible for saliva secretion. NFAT5 knockout compromises saliva secretion, redistributes aquaporin-5 and increases apoptosis in submandibular glands. These data suggest NFAT5 is essential for maintaining salivary gland homeostasis by coupling osmotic regulation, water transport and epithelial survival.