Modulation of human umbilical cord‐derived mesenchymal stromal cells immunophenotype through cellular priming

Abstract

The in vitro immunomodulation effects of bone marrow‐derived mesenchymal stromal cells (BM‐MSCs) can be drastically altered by stimulation of toll‐like receptor (TLR) 3 and 4 into diametrically different immunomodulatory phenotypes similar to activated macrophage type 1 (M1) and macrophage type 2 (M2) polarization. BM‐MSCs activated by TLR4 ligand lipopolysaccharide (LPS) display an enhanced pro‐inflammatory phenotype (MSC1). In contrast, BM‐MSCs stimulated by Poly I:C, a TLR3 ligand that simulates a viral infection, display an anti‐inflammatory phenotype, called MSC2. This phenomenon has been termed “MSC priming”. The objective of this study was to determine whether human umbilical cord‐derived (HUC) MSCs display enhanced immune suppression after MSC1 versus MSC2 priming. Four different media conditions: 1) the TLR4 ligand LPS, 2) the TLR3 ligand Poly I:C, 3) interferon gamma (IFN‐γ) which upregulates TLR4 receptors and 4) human platelet lysate (HPL) versus control (multipotent adult progenitor cell (MAPC) medium. Five independent MSC lines were tested. Immune properties were assayed by examining the cell's suppression on the proliferation of stimulated murine splenocytes and 2) cytokine production: PGE2 and indoleamine 2,3‐dioxygenase (IDO) via ELISA. Cells cultured in IFN‐γ, LPS and Poly I:C media showed significant upregulation of IDO compared to MAPC medium. The expression of PGE2 was not significantly altered. Compared with MAPC medium, HPL medium inhibited the immunosuppressive effects of MSCs. In contrast, IFN‐γ and MAPC medium had the greatest immunosuppressive effects. Umbilical cord‐derived MSCs did not undergo MSC1 priming by TLR3 ligand stimulation like bone marrow‐derived MSCs.