IFN-γ and TNF-α Synergistically Induce Mesenchymal Stem Cell Impairment and Tumorigenesis via NFκB Signaling

An inflammatory microenvironment may cause organ degenerative diseases and malignant tumors. However, the precise mechanisms of inflammation-induced diseases are not fully understood. Here we show that the proinflammatory cytokines interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) synergistically impair self-renewal and differentiation of mesenchymal stem cells (MSCs) via nuclear factor κB (NFκB)–mediated activation of Mothers against decapentaplegic homolog 7 (SMAD7) in ovariectomized (OVX) mice. More interestingly, a long-term elevated levels of IFN-γ and TNF-α result in significantly increased susceptibility to malignant transformation in MSCs through NFκB–mediated upregulation of the oncogenes c-Fos and c-Myc. Depletion of either IFN-γ or TNF-α in OVX mice abolishes MSC impairment and the tendency toward malignant transformation with no NFκB–mediated oncogene activation. Systemic administration of aspirin, which significantly reduces the levels of IFN-γ and TNF-α, results in blockage of MSC deficiency and tumorigenesis by inhibition of NF-κB/SMAD7 and NFκB/c-FOS and c-MYC pathways in OVX mice. In summary, this study reveals that inflammation factors, such as IFN-γ and TNF-α, synergistically induce MSC deficiency via NFκB/SMAD7 signaling and tumorigenesis via NFκB–mediated oncogene activation

IFN-γ and TNF-α Synergistically Induce Mesenchymal Stem Cell Impairment and Tumorigenesis via NFκB Signaling

An inflammatory microenvironment may cause organ degenerative diseases and malignant tumors. However, the precise mechanisms of inflammation-induced diseases are not fully understood. Here we show that the proinflammatory cytokines interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) synergistically impair self-renewal and differentiation of mesenchymal stem cells (MSCs) via nuclear factor κB (NFκB)–mediated activation of Mothers against decapentaplegic homolog 7 (SMAD7) in ovariectomized (OVX) mice. More interestingly, a long-term elevated levels of IFN-γ and TNF-α result in significantly increased susceptibility to malignant transformation in MSCs through NFκB–mediated upregulation of the oncogenes c-Fos and c-Myc. Depletion of either IFN-γ or TNF-α in OVX mice abolishes MSC impairment and the tendency toward malignant transformation with no NFκB–mediated oncogene activation. Systemic administration of aspirin, which significantly reduces the levels of IFN-γ and TNF-α, results in blockage of MSC deficiency and tumorigenesis by inhibition of NF-κB/SMAD7 and NFκB/c-FOS and c-MYC pathways in OVX mice. In summary, this study reveals that inflammation factors, such as IFN-γ and TNF-α, synergistically induce MSC deficiency via NFκB/SMAD7 signaling and tumorigenesis via NFκB–mediated oncogene activation

Basic Fibroblast Growth Factor Inhibits Osteogenic Differentiation of SHED through ERK Signaling

Objective Stem cells from human exfoliated deciduous teeth (SHED) are a unique postnatal stem cell population capable of regenerating mineralized tissue and treating immune disorders. However, the mechanism that controls SHED differentiation is not fully understood. Here, we showed that basic fibroblast growth factor (bFGF) treatment attenuated SHED-mediated mineralized tissue regeneration through activation of the extracellular signal-regulated kinase (ERK) 1/2 pathway. Material and Method The level of mineralized nodule formation was assessed by alizarin red staining. Expression levels of osteogenic genes, OCN and Runx2, were examined by RT-PCR. Subcutaneous implantation approach was used to assess in vivo bone formation. Downstream signaling pathways of bFGF were examined by Western blotting. Result Activation of ERK1/2 signaling by bFGF treatment inhibited WNT/β-catenin pathway, leading to osteogenic deficiency of SHED. ERK1/2 inhibitor treatment rescued bFGF-induced osteogenic differentiation deficiency. Conclusion These data suggest that bFGF inhibits osteogenic differentiation of SHED via ERK1/2 pathway. Blockade ERK1/2 signaling by small molecular inhibitor-treatment improves bone formation of SHED after bFGF treatment

Mesenchymal Stem Cell-Induced Immunoregulation Involves Fas Ligand/Fas-Mediated T Cell Apoptosis

Systemic infusion of bone marrow mesenchymal stem cells (BMMSCs) shows therapeutic benefit for a variety of autoimmune diseases, but the underlying mechanisms are poorly understood. Here we show that in mice systemic infusion of BMMSCs induced transient T-cell apoptosis via the Fas ligand (FasL)-dependent Fas pathway and could ameliorate disease phenotypes in fibrillin-1 mutated systemic sclerosis (SS) and dextran sulfate sodium-induced experimental colitis. FasL−/− BMMSCs did not induce T-cell apoptosis in recipients, and could not ameliorate SS and colitis. Mechanistic analysis revealed that Fas-regulated monocyte chemotactic protein 1 (MCP-1) secretion by BMMSCs recruited T-cells for FasL-mediated apoptosis. The apoptotic T-cells subsequently triggered macrophages to produce high levels of TGFβ which in turn led to the upregulation of Tregs and, ultimately, to immune tolerance. These data therefore demonstrate a previously unrecognized mechanism underlying BMMSC-based immunotherapy involving coupling via Fas/FasL to induce T-cell apoptosis

Hydrogen Sulfide Maintains Mesenchymal Stem Cell Function and Bone Homeostasis via Regulation of Ca2+ Channel Sulfhydration

Gaseous signaling molecules such as hydrogen sulfide (H2S) are produced endogenously and mediate effects through diverse mechanisms. H2S is one such gasotrasmitter which regulates multiple signaling pathways in mammalian cells, and abnormal H2S metabolism has been linked to defects in bone homeostasis. Here, we demonstrate that bone marrow mesenchymal stem cells (BMMSCs) produce H2S to regulate their self-renewal and osteogenic differentiation, and H2S deficiency results in defects in BMMSC differentiation. H2S deficiency causes aberrant intracellular Ca2+ influx, due to reduced sulfhydration of cysteine residues on multiple Ca2+ TRP channels. This decreased Ca2+ flux downregulates PKC/Erk-mediated Wnt/β-catenin signaling which controls osteogenic differentiation of BMMSCs. Consistently, H2S-deficient mice display an osteoporotic phenotype, which can be rescued by small molecules which release H2S. These results demonstrate H2S regulates BMMSCs, and restoring H2S levels via non-toxic donors may provide treatments for diseases such as osteoporosis which can arise from H2S deficiencies

Hydrogen Sulfide Promotes Tet1- and Tet2-mediated Foxp3 Demethylation to Drive Regulatory T Cell Differentiation and Maintain Immune Homeostasis

Regulatory T (Treg) cells are essential for maintenance of immune homeostasis. Here we found that hydrogen sulfide (H2S) was required for Foxp3+ Treg cell differentiation and function, and that H2S deficiency led to systemic autoimmune disease. H2S maintained expression of methylcytosine dioxygenases Tet1 and Tet2 by sulfhydrating nuclear transcription factor Y subunit beta (NFYB) to facilitate its binding to Tet1 and Tet2 promoters. Transforming growth factor-β (TGF-β)-activated Smad3 and interleukin-2 (IL-2)-activated Stat5 facilitated Tet1 and Tet2 binding to Foxp3. Tet1 and Tet2 catalyzed conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in Foxp3 to establish a Treg cell-specific hypomethylation pattern and stable Foxp3 expression. Consequently, Tet1 and Tet2 deletion led to Foxp3 hypermethylation, impaired Treg cell differentiation and function, and autoimmune disease. Thus, H2S promotes Tet1 and Tet2 expression, which are recruited to Foxp3 by TGF-β and IL-2 signaling to maintain Foxp3 demethylation and Treg cell-associated immune homeostasis

iPS Cells Reprogrammed From Human Mesenchymal-Like Stem/Progenitor Cells of Dental Tissue Origin

Generation of induced pluripotent stem (iPS) cells holds a great promise for regenerative medicine and other aspects of clinical applications. Many types of cells have been successfully reprogrammed into iPS cells in the mouse system; however, reprogramming human cells have been more difficult. To date, human dermal fibroblasts are the most accessible and feasible cell source for iPS generation. Dental tissues derived from ectomesenchyme harbor mesenchymal-like stem/progenitor cells and some of the tissues have been treated as biomedical wastes, for example, exfoliated primary teeth and extracted third molars. We asked whether stem/progenitor cells from discarded dental tissues can be reprogrammed into iPS cells. The 4 factors Lin28/Nanog/Oct4/Sox2 or c-Myc/Klf4/Oct4/Sox2 carried by viral vectors were used to reprogram 3 different dental stem/progenitor cells: stem cells from exfoliated deciduous teeth (SHED), stem cells from apical papilla (SCAP), and dental pulp stem cells (DPSCs). We showed that all 3 can be reprogrammed into iPS cells and appeared to be at a higher rate than fibroblasts. They exhibited a morphology indistinguishable from human embryonic stem (hES) cells in cultures and expressed hES cell markers SSEA-4, TRA-1-60, TRA-1-80, TRA-2-49, Nanog, Oct4, and Sox2. They formed embryoid bodies in vitro and teratomas in vivo containing tissues of all 3 germ layers. We conclude that cells of ectomesenchymal origin serve as an excellent alternative source for generating iPS cells