Young-Woo Eom

Comparison of immunomodulatory properties of mesenchymal stem cells derived from adult human tissues

Mesenchymal stem cells (MSCs), which evoke only minimal immune reactivity, may have anti-inflammatory and immunomodulatory effects. In this study, we conducted a comparative analysis of the immunomodulatory properties of MSCs derived from adult human tissues including bone marrow (BM), adipose tissues (AT), umbilical cord blood (CB), and cord Whartons jelly (WJ). Using a multiple cytokine detection assay, we showed that there were no significant differences in levels of secreted factors from non-stimulated MSCs. We compared the immunosuppressive effect of BM-MSCs, AT-MSCs, CB-MSCs, and WJ-MSCs on phytohemagglutinin-induced T-cell proliferation. AT-MSCs, CB-MSCs, and WJ-MSCs effectively suppressed mitogen-induced T-cell proliferation as effectively as did BM-MSCs. Levels of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha secreted from activated T-cells increased over time, but these levels were significantly reduced when cocultured with each type of MSCs. In addition, the expression of hepatocyte growth factor, IL-10, transforming growth factor-beta(1), cyclooxygenase (COX)-1, and COX-2 were unchanged in MSCs treated with IFN-gamma and/or TNF-alpha, while indoleamine 2,3-dioxygenase (IDO) expression increased. IFN-gamma and/or TNF-alpha produced by activated T-cells were correlated with induction of IDO expression by MSCs, which, in turn, suppressed T-cell proliferation. These findings suggest that MSCs derived from AT, CB, or WJ could be substituted for BM-MSCs for treatment of allogeneic conflicts.

Two distinct modes of cell death induced by doxorubicin: apoptosis and cell death through mitotic catastrophe accompanied by senescence-like phenotype

Chronic exposure of many human hepatoma cell lines to a low dose (LD) of doxorubicin induced a senescence-like phenotype (SLP) accompanied by enlargement of cells and increased senescence-associated β-galactosidase activity. LD doxorubicin-induced SLP was preceded by multinucleation and downregulation of multiple proteins with mitotic checkpoint function, including CENP-A, Mad2, BubR1, and Chk1. LD doxorubicin-treated cells eventually underwent cell death through mitotic catastrophe. When we investigated whether LD doxorubicin-induced cell death shares biochemical characteristics with high dose (HD) doxorubicin-induced apoptosis in Huh-7 cells, we observed that externalization of phosphatidyl serine and release of mitochondrial cytochrome c into the cytosol was associated with both types of cell death. However, propidium iodide exclusion assays showed that membrane integrity was lost in the initial phase of LD doxorubicin-induced cell death through mitotic catastrophe, whereas it was lost during the late phase of HD doxorubicin-induced apoptosis. Furthermore, HD doxorubicin-induced apoptosis but not LD doxorubicin-induced mitotic catastrophe led to transient activation of NF-κB and strong, sustained activations of p38, c-Jun N-terminal kinase, and caspases. Collectively, these results indicate that different doses of doxorubicin activate different regulatory mechanisms to induce either apoptosis or cell death through mitotic catastrophe.

Involvement of c-Src kinase in the regulation of TGF-beta1-induced apoptosis.

Transforming growth factor-β1 (TGF-β1) is a potent inducer of apoptosis in normal hepatocytes, and acquiring resistance to TGF-β1 may be a critical step in the development of hepatocellular carcinoma (HCC). In this study, we investigated the possible involvement of c-Src in the regulation of TGF-β1-induced apoptosis. TGF-β1 induced transient activation of c-Src and its subsequent caspase-mediated degradation concomitant with cell death in FaO hepatoma cells, which are sensitive to TGF-β1. In response to TGF-β1, activated c-Src was translocated into the cytoplasmic membrane, then relocated to the nuclei of apoptotic cells during its cleavage. In TGF-β1-induced apoptotic cells, c-Src maintained its tight association with p85 FAK fragment cleaved by caspases, possibly contributing to focal adhesion disassembly. TGF-β1-induced apoptosis was enhanced by either inhibition of c-Src activity using PP1 or PP2, or by overexpression of dominant-negative c-Src. In contrast, overexpression of constitutively active c-Src inhibited apoptosis suppressing TGF-β1-induced activation of p38, JNK and caspases. In many HCC cell lines resistant to TGF-β1, enhanced c-Src activity was detected. We hypothesize that activated c-Src in HCC may contribute to resistance against the apoptotic and/ or antiproliferative properties of TGF-β1.

Neurally induced umbilical cord blood cells modestly repair injured spinal cords.

Umbilical cord blood (UCB) is known to have stem/progenitor cells. We earlier showed that novel progenitors could be isolated from cryopreserved human UCB with high efficiency. The multipotent progenitor cells were induced to differentiate into neural-lineage cells under the appropriate condition. In this study, we confirmed these neurally induced progenitor cells (NPCs), containing higher quantities of nerve growth factor, promoted functional recovery in rats with spinal cord injury (SCI). Sprague–Dawley rats with SCI achieved a modest improvement in locomotor rating scale until 10 weeks after transplantation of the NPCs. SCI rats treated with NPCs also showed somatosensory-evoked potentials were recovered, and grafted cells especially exhibited oligodendrocytic phenotype around the necrotic cavity. These findings suggest that UCB-NPCs might be a therapeutic resource to repair damaged spinal cords.

Hepatic differentiation of cord blood-derived multipotent progenitor cells (MPCs) in vitro.

Umbilical cord blood (UCB) is a rich source of hematopoietic stem cells that possesses practical and ethical advantages. We previously reported a novel UCB‐derived adult stem cells which we termed umbilical cord blood‐derived multipotent progenitor cells’ (MPCs). MPCs were capable of differentiating into functional neuronal cells. Under appropriate conditions lasting several days or weeks, we now show that the MPCs differentiate into hepatocyte‐like cells in vitro; their properties were verified using reverse transcription‐polymerase chain reaction (RT‐PCR), Western blot, immunofluorescence, periodic acid‐Schiff (PAS) staining of accumulated glycogen and an enzyme‐linked immunosorbent assay (ELISA). We also found that hepatic differentiated cells expressed hepatocyte specific markers, such as albumin, hepatocyte nuclear factor (HNF)‐1α, HNF4, cytokeratin (CK)‐8, CK‐18, tyrosine amino transferase (TAT), and CYP2B6. Moreover, albumin was secreted, which suggests that MPCs from UCB possess multi‐differentiation potential and have the capacity to differentiate into functional cells of hepatic lineage in vitro.