Human Amniotic Fluid Stem Cells Suppress PBMC Proliferation through IDO and IL-10-Dependent Pathways

Abstract

Human amniotic fluid stem cells (hAFSCs) can be readily isolated from human amniotic fluid and display multi-differentiation potential and immunomodulatory properties. The mechanism of hAFSCs immunoregulation has not been defined. Here, we explore the immunomodulatory effects of hAFSCs derived from human amniotic fluid and evaluate the role of IL-10 and the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) in mediating the immunosuppressive actions of hAFSCs. Flow cytometry showed that hAFSCs were positive for the mesenchymal stem cell markers CD29, CD44, CD105, HLA-ABC, and more than 84% of the hAFSCs were positive for SSEA-4, which is a typical marker of embryonic stem cell (ESCs), and negative for HLA-DR. The RT-PCR and immunostaining results revealed that the multipotent stem cells expressed OCT-4, Nanog, CD44, SOX2 and SSEA-1. In vitro differentiation assays demonstrated that hAFSCs underwent osteogenic differentiation. We examined the immunomodulatory function of hAFSCs using a co-culture system with phorbol 12-myristate 13-acetate (PMA) stimulated peripheral blood mononuclear cells (PBMCs). PBMC proliferation was suppressed by the hAFSCs in a dose-dependent manner. The inhibitory effect was caused by increased IL-10 and IDO induction after co-culture. Neutralizing the IL-10 activity or blocking the function of IDO partially abolished the immunosuppressive action of the hAFSCs. In conclusion, these results suggest that the hAFSCs possess immunomodulatory properties, and IL-10 and IDO are involved in immunosuppression by hAFSCs.

Secretion of immunoregulatory cytokines by mesenchymal stem cells

“…IDO is one of the key immunoregulators secreted by MSCs, tumors and during pregnancy. IDO is expressed by a wide range of MSCs, like decidual MSCs [167] , amnionic fluid MSC [168] , multipotent adult progenitor cells (MAPCs) [169] , umbilical cord MSCs [170] , AT-MSCs [171] etc. IDO expression is species specific.…”

“…Damage associated molecular patterns (DAMPs) are also involved in the IDO expression regulated by MSCs [178] . IDO is expressed after stimuli generated by the crosstalk of MSCs and cells co-cultured with them [168,179] . The cross-talk of MSCs and PBMCs causes increased IL-10 and IDO expression from MSCs that seems to be the mechanism responsible for the immunosuppressive action of the human amnionic fluid stem cells [168] .…”

“…IDO is expressed after stimuli generated by the crosstalk of MSCs and cells co-cultured with them [168,179] . The cross-talk of MSCs and PBMCs causes increased IL-10 and IDO expression from MSCs that seems to be the mechanism responsible for the immunosuppressive action of the human amnionic fluid stem cells [168] . After IFNγ priming of MSCs, the IDO expression leads to B-cell growth arrest and apoptosis [180] , in contrast to not activated MSCs that are IDO negative and support B-cell proliferation and survival.…”

Amniotic Fluid Stem Cells for the Treatment of Surgical Disorders in the Fetus and Neonate

“…Amniotic fluid‐derived stem cells genetically originate from the fetus itself, thereby allowing for autologous therapeutic applications to be performed without concern for immunologic rejection of donor cells upon delivery, either prenatally or in the early postnatal period . Studies have shown that second‐trimester amniotic fluid stem cells can proliferate rapidly in culture compared to postnatal somatic cells under Good Manufacturing Practice conditions .…”

“…Although the mechanistic role of amniotic fluid‐derived MSCs in vivo remains poorly described, MSCs from amniotic fluid have been shown to inhibit T‐cell proliferation, to decrease memory T cells, to increase T regulator lymphocytes, and to polarize the Th2 subtype in association with increased IL‐10 and IL‐4 levels in coculture studies when compared to MSCs derived from bone marrow and placenta . It has been hypothesized that amniotic fluid‐derived MSCs may play a critically important paracrine role in the immune response at the maternal‐fetal interface through expression of the CD59 and HLA‐G, among others .…”