Scap-Exos Ameliorate Sjogren’S Syndrome By Promoting Tregs Differentiation

To investigate the effects of stem cells from apical papilla-derived exosomes (SCAP-Exos) on ameliorating Sjogren’s syndrome (SS) and its underlying mechanism of promoting CD4+ T cells differentiation into regulatory T cells (Tregs). SCAP-Exos were systemically infused into SS mice via the tail vein. Flow cytometry were used to detect the proportion of Tregs in spleen. Salivary flow rate tests and haematoxylin and eosin staining were performed to detect salivary secretion and pathological changes in the submandibular glands. To further explore the mechanism of SCAP-Exos, we determined the levels of N6-methyladenosine (m6A) modification and related protein in CD4+ T cells by colorimetry and western blot. Additionally, RNA sequencing was conducted to find out the downstream target of methyltransferase-like 3 (Mettl3). Finally, CD4+ T cells from SS mice were treated with different doses of SCAP-Exos to investigate the pivotal role of Mettl3 in Tregs differentiation by flow cytometry and western blot in vitro. SCAP-Exos significantly increased Tregs proportion, enhanced salivary secretion in SS mice and reduced inflammatory cells infiltration of the submandibular glands. The m6A modification level of CD4+ T cells mRNA of SS mice treated with SCAP-Exos was improved. In vitro, SCAP-Exos upregulated Mettl3 expression, thereby decreasing suppressor of cytokine signalling 3 expression and promoting CD4+ T cells differentiation into Tregs. SCAP-Exos could facilitate CD4+ T cells differentiation into Tregs by enhancing Mettl3-mediated m6A modification, ultimately restoring immune homeostasis and salivary gland secretory function in SS mice.