The Impact of Alternate-Day Fasting on the Salivary Gland Ductal Compartments and the Differentiation Potential of Keratin 5+ Salivary Gland Progenitor Cells in an Induced Mouse Model of Sjögren’s-like Hyposalivation

Intermittent fasting confers protection in diverse diseases through various mechanisms, including the clearance of senescent and pathogenic cells, modulation of tissue inflammation and enhancement of stem/progenitor cell niche and functionality. Our previous study demonstrated the beneficial impact of alternate-day fasting (ADF) on xerostomia and sialadenitis, along with an improvement in salivary gland ductal compartments, where salivary gland progenitor cells reside, in non-obese diabetic mice, a spontaneous model of Sjögren’s syndrome (SS). In the present study, we induced SS-associated hyposalivation in KRT5CreERT2; R26tdTomato lineage tracing mice by immunizing them with submandibular gland proteins from wild-type C57BL/6 mice. ADF alleviated salivary gland hypofunction, which was accompanied by decreased expression of the senescent cell marker p16INK4a, reduced protein levels of anti-apoptotic proteins BCL-2, BCL-XL, and MCL-1, and attenuated NLRP3 inflammasome activity in the submandibular glands, particularly within the ductal compartments, of this inducible model. Furthermore, immunofluorescence staining of submandibular gland sections revealed the expression of the acinar cell marker aquaporin 5 in a small subset of Keratin 5+ cells in 2 of 9 mice that were subjected to ADF, whereas no such cells were detected in the control mice. Taken together, these findings indicate that ADF favorably modulates the salivary gland progenitor cell niche, potentially by promoting apoptosis-mediated senescent cell clearance, suppressing NLRP3 inflammasome signaling, and promoting Keratin 5+ progenitor cell-derived acinar cell replenishment, thereby contributing to the structural and functional restoration of damaged salivary glands in autoimmune exocrinopathy.