Psoriatic Serum Induce an Abnormal Inflammatory Phenotype and a Decreased Immunosuppressive Function of Mesenchymal Stem Cells

BACKGROUND AND OBJECTIVES: Mesenchymal stem cells (MSCs) have immunomodulatory function and participate in the pathogenesis of many immunoregulation-related diseases, including psoriasis. Previously, we found that MSCs from psoriatic lesions overexpress the proinflammatory microRNA, miR-155 and exhibit a decreased immunosuppressive capacity. But the origin of these aberrant characteristics is still not clear. To investigate whether inflammatory cytokines in serum and peripheral blood mononuclear cells (PBMCs) from psoriatic patients can regulate the expression patterns of immunoregulation-related cytokines and the immunoregulation function of MSCs. METHODS AND RESULTS: Normal dermal mesenchymal stem cells (nDMSCs) were treated with serum or PBMCs derived from patients with psoriasis or healthy donors. Expression of miR-155 and immunoregulation-related genes in each MSCs were measured using real-time PCR or western-blot. Meanwhile, the immunosuppressive capacity of DMSCs was evaluated by its inhibitory ability on proliferation of activated PBMCs. Compared to control serum, psoriatic serum significantly increased the expression levels of miR-155 (27.19±2.40 vs. 3.51±1.19, p<0.001), while decreased TAB(2) expression (0.28±0.04 vs. 0.72±0.20, p<0.01) in DMSCs. Expression levels of immunoregulation-related genes such as PGE(2), IL-10, and TLR4 were also markedly down-regulated following the psoriatic serum treatment. Those DMSCs treated with healthy serum could inhibit PBMC proliferation, while those psoriatic serum-treated DMSCs could not inhibit PBMC proliferation effectively. CONCLUSIONS: Psoriatic serum up-regulate the expression of miR-155, down-regulate the expression of immunoregulation-related genes (PGE(2), IL-10, and TLR4) in DMSCs, and along with the inhibition of the immunosuppressive function of MSCs.