SHED-Derived Exosomes Ameliorate Sjögren's Syndrome-Induced Hyposalivation by Suppressing Th1 Cell Response via the miR-29a-3p/T-bet Axis.

: Sjögren's syndrome (SS), an autoimmune disease, was characterized by sicca syndrome and systemic manifestations, presenting significant treatment challenges. Exosomes, naturally derived nanoparticles containing bioactive molecules, have garnered interest in regenerative medicine. The present study aimed to elucidate the immunoregulatory properties and mechanism of exosomes obtained from the stem cells derived from human exfoliated deciduous teeth (SHED-exos) in SS-induced sialadenitis. : SHED-exo nanoparticles were injected into submandibular glands (SMGs) of 14-week-old nonobese diabetic (NOD) mice, a classic animal model of SS. At 21 weeks, the saliva flow rate (SFR) was measured. Lymphocyte proportions were examined via flow cytometry. Inflammatory cytokine levels were examined by the Quantibody mouse Th1/Th2/Th17 array and ELISA. miR-29a-3p expression and its regulatory effect on T-bet was detected using FISH and luciferase reporter gene assay, respectively. : SHED-exos injected into SMGs increased SFR, reduced lymphocytic infiltration, and decreased inflammatory cytokine levels in serum, SMG tissues, and saliva. Mechanistically, SHED-exos suppressed the Th1 proportion in spleen lymphocytes in NOD mice. Exosomal miR-29a-3p targeted and suppressed T-bet expression, which is a Th1-specific transcription factor. In vitro, SHED-exos (but not miR-29a-3p-inhibited exosomes) decreased the level of Th1 differentiation and IFN-γ and TNF-α production. Furthermore, SHED-exos (but not miR-29a-3p-inhibited exosomes) blocked the increase in IFN-γ and TNF-α production induced by T-bet overexpression. In vivo, miR-29a-3p-inhibited exosomes neither increase saliva secretion in NOD mice nor decrease lymphocytic infiltration, T-bet expression, and IFN-γ and TNF-α levels in SMGs. : SHED-exos suppress Th1 cell differentiation and response through the miR-29a-3p/T-bet axis, contributing to amelioration of SS-induced hyposalivation.