The suppression effect of dendritic cells maturation by adipose-derived stem cells through TGF-β1 related pathway

Background: Our previous studies demonstrated that adipose-derived stem cells (ASCs) could modulate regulatory T cells (Treg) and prolong hind-limb allotransplant survival in vitro and in vivo. Dendritic cells (DCs) play a pivotal role in innate and adaptive immunity. The aim of this study is to investigate the underlying mechanism of ASCs in modulating DC maturation. Materials and Methods: ASCs were isolated from rodent adipose tissue, DCs were derived from the bone marrow, and CD4⁺ T cells were purified from splenocytes. DCs were co-cultured with ASCs to evaluate the suppressive effects of ASCs. CD4⁺ T-cells were co-cultured with DCs pre-treated with or without ASCs. The cell surface markers of DCs were analyzed by flow cytometry. T-cell proliferation was analyzed by the BrdU proliferation test. Tolerogenic cytokines and indoleamine 2,3-dioxygenase (IDO) expressions after different treatments were detected by quantitative real-time PCR, Western blotting, and ELISA analysis. Result: ASCs suppressed DC maturation as evidenced by low expressions of CD80, CD86, and MHC-II. Also, ASC-treated mature DCs showed higher levels of TGF-β1, IL-10, and IDO expressions, as compared to that in matured DCs (mDCs) alone. ASC-treated mDCs co-cultured with CD4⁺ T cells revealed a significant higher percentage of Treg than mDC without treatment. The IDO level in ASC-treated mDCs and Treg induction effects were blocked by the ASCs pre-treated with TGF-β1 siRNAs, but not IL-10 siRNAs. Conclusion: ASC-modulated DC maturation correlated with TGF-β1 secretion, IDO expression, and Treg induction. ASCs could be used as a potential immunomodulatory strategy for clinical application in allotransplantation.