Exosomes derived from stem cells from apical papilla reduce Th17 cell differentiation and hyposalivation in a murine model of Sjögren’s disease

Sjögren’s disease (SjD) is a chronic autoimmune disease that is characterized by progressive lymphocyte infiltration and a decrease in the secretory function of the salivary glands. Mesenchymal stem cell (MSCs) transplantation has shown great potential in the treatment of SjD. Exosomes are one of the key paracrine factors that allow MSCs to perform their functions, and are more stable and safer than MSCs. Stem cells from apical papilla (SCAP), a kind of dental stem cells that are derived from the neural crest, have a wide range of immunoregulatory properties. However, the roles of exosomes derived from SCAP (SCAP-Exo) in the treatment of SjD are not clear. This study investigated the effects of SCAP-Exo on ameliorating hyposalivation in a murine model of SjD and the underlying mechanisms. SCAP was extracted from human apical papilla tissue. Then, SCAP-Exo were isolated and characterized by western blotting, transmission electron microscopy and nanoparticle tracking analysis. SCAP-Exo were systemically infused into murine models of SjD via the tail vein. The saliva flow rate tests and H&E staining were performed to detect the salivary secretion and pathologic changes of submandibular glands. T helper 17 (Th17) cells percentage and interleukin-17 (IL-17) levels changes were detected by flow cytometry and enzyme-linked immunosorbent assays (ELISA). PIWI-interacting RNA (piRNA) array analysis was conducted to determine the piRNA expression profiles of SCAP-Exo and screen for piRNAs associated with Th17 cell differentiation pathway. A luciferase reporter assay was performed to reveal the possible effect of the exosomal hsa-piR-188154 on interleukin-6 receptor (IL-6R) mRNA. Furthermore, the molecular mechanism by which hsa-piR-188154 regulated Th17 cell differentiation in vitro was tested by flow cytometry, ELISA, and reverse transcription-quantitative polymerase chain reaction. We found that SCAP-Exo transplantation successfully improved saliva secretion, alleviated lymphocyte infiltration in the submandibular glands and reduced the proportion of Th17 cells in SjD mice. Mechanistically, hsa-piR-188154 was enriched in SCAP-Exo; a luciferase reporter assay demonstrated that hsa-piR-188154 directly targeted the IL-6R mRNA 3’ untranslated region. Furthermore, we revealed that hsa-piR-188154 inhibited Th17 differentiation and downregulated the level of IL-17 A in the supernatant and the expression levels of Th17-related genes in vitro. This study demonstrated that SCAP-Exo had a superior therapeutic effect on SjD by inhibiting Th17 cell differentiation. These data suggested that SCAP-Exo could be used in a cell-free approach for the clinical treatment of autoimmune disease.