Human Amniotic Mesenchymal Stem Cells Exhibit Similar Immunosuppressive Ability with Bone Marrow Mesenchymal Stem Cells and Possess a Higher Proliferation Activity and Clearer Stem Cell Properties in vitro

Objectives: Human bone marrow mesenchymal stem cells (hBMSCs) have been used for the prevention and treatment of acute graft-versus-host disease (aGVHD) in post-hematopoietic stem cell transplant patients. In this study, we compared the biological characteristics and immunosuppressive activity of human amniotic mesenchymal stem cells (hAMSCs) and hBMSCs to provide experimental evidence for the potential use of hAMSCs for treating aGVHD, thus solving the problem of insufficient hBMSCs sources. Methods: HAMSCs were isolated by enzymatic digestion. hBMSCs were isolated using Ficoll-Hypaque density gradients. The biological characteristics of both stem cell types were compared by morphological analysis, analysis of cell growth, cell cycle profiling, immunophenotyping, and immunofluorescence assays. An in vitro co-culture of MSCs and peripheral blood mononuclear cells (PBMCs) was performed and lymphocyte proliferation measured using the Cell Counting Kit-8(CCK-8) assay. IFN-γ production was determined in the co-culture supernatant using enzyme linked immunosorbent assay (ELISA). Results: Both hAMSCs and hBMSCs had fibroblast-like morphology. hAMSCs could be maintained for at least 15 culture passages, but hBMSCs started to show signs of aging and remarkably reduced proliferation at 6-7 passages. There was no significant difference in the proportion of cells in G2/M phase between hAMSCs and hBMSCs (P>0.05). Immunophenotyping revealed positive expression of CD105, CD90, and CD73 and negative expression of CD34, CD45, CD11b, CD19, and HLA-DR on the surface of both hAMSCs and hBMSCs. hAMSCs were positive for Oct-3/4, but hBMSCs were not. Both hAMSCs and hBMSCs expressed vimentin. PHA-stimulated PBMCs proliferation was inhibited by hAMSCs and hBMSCs. This inhibition was stronger, as the proportion of MSCs increased. There were not significant differences between the inhibitory effects of the two MSCs types on PBMCs proliferation (P>0.05). Interferon-γ (IFN-γ) production was lower when PBMCs were co-cultured with either hAMSCs or hBMSCs than when they were cultured alone (P 0.05). Conclusion: The results of this study demonstrated that hAMSCs have higher proliferation activity and clearer stem cell properties than hBMSCs. Both hAMSCs and hBMSCs were able to suppress the proliferation of allogeneic peripheral blood lymphocytes and reduce IFN-γ secretion stimulated by PHA in vitro.