Can the Palatine Tonsil be a Source of Mesenchymal Stem Cells with Immunomodulatory Property?

Background and Objectives: Mesenchymal stem cells (MSCs) are multi potent cells that can differentiate into various cell types and are isolated from various other human adult and fetal tissues. Our study is to isolate palatine tonsil-derived MSCs (T-MSCs) and evaluate their differentiation potential and immunomodulatory effects, compared with bone marrow-derived MSCs (BM-MSCs). Methods: T-MSCs were isolated from human palatine tonsil. The expression of surface markers of T-MSCs was assessed by flow cytometric analysis. Differentiation potential of T-MSCs was analyzed histochemically and by the expression of lineage-related marker genes. Immunomodulatory effects were evaluated by mixed lymphocyte reactions (MLR) and mitogen proliferation assays with phytohemagglutinin (PHA). Results: T-MSCs were isolated from palatine tonsil and displayed a similar morphology to BM-MSCs. T-MSCs were negative for CD 31?CD45, CD117, HLA-DR and positive for CD44, CD73, CD90, and CD105 in flow cytometric analysis. The expression of surface phenotypes and differentiation potential of T-MSCs exhibited the similar finding as BM-MSCs. T-MSCs showed the significant inhibition of the proliferation of T cells stimulated by allergenic T cells in MLR study and by PHA stimuli in mitogen proliferation assay and also significant decrease of the secretion of TNF-a and IFN-γ (p <0.05). The HLA-G5 secretion by T-MSCs showed the significant increase in MLR and mitogen proliferation assays (p<0.05). T-MSCs do satisfy the phenotypical and functional definition of MSCs. T-MSCs also displayed immuno- modulatory effects that were associated with inhibiting T-cell proliferation, decreasing soluble factors, and increasing HLA-G5 secretion in response to various stimuli. Conclusions: We propose that T-MSCs provide a good alternative for allogeneic MSCs in therapeutic applications. (J Clinical Otolaryngol 2012;23:90–100)