Introducing pulsed low-intensity ultrasound to culturing human umbilical cord-derived mesenchymal stem cells

The human umbilical cord (hUC) is a source of adult tissue-derived mesenchymal stem cells (MSCs). A pulsed low-intensity ultrasound (PLIUS) method is described for increasing the yield of MSCs from whole hUC without enzymatic digestion or growth factor supplementation. Analysis of the immunophenotype of cells and a differentiation study were performed to show the compatibility of MSCs. The mean number of cells recovered from primocultures of hUC was 6 × 10⁵ cells/cm. PLIUS resulted in a 3.3-fold increase in MSC yield at passage 0. PLIUS exposure increases the yield of hUC-MSCs by promoting release and enhancing proliferation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

In vitro hepatic differentiation of umbilical cord-derived mesenchymal stem cell

Recently hepatic differentiation of mesenchymal stem cells (MSCs) from bone marrow (BM), adipose tissue (AT), umbilical cord blood (UCB), and umbilical cord (UC) has been reported. In this study, the four-step sequential exposure with oncostatin M (OSM) plus trichostatin A (TSA) or OSM plus dimethyl sulfoxide (DMSO) at the final step induced hepatic differentiation of UC-MSCs. As a result, the morphology and protein expression were sequentially changed in the step-dependent manner. And the urea synthesis rates of (OSM plus TSA)- and (OSM plus DMSO)-treated cells on day 21 reached to 23 ± 0.4 and 20 ± 0.5 μg/10⁶ cells/day, respectively. The ammonia concentrations 24 h after culture with 1 mM NH₄Cl-supplemented medium dropped to 0.41 ± 0.08 mM (OSM plus TSA) and 0.57 ± 0.05 mM (OSM plus DMSO). Also the ethoxyresorufin O-deethylase (EROD) activities were 3.4-fold (OSM plus TSA) and 2.2-fold (OSM plus DMSO) higher than non-induced controls on day 21. It is thought that TSA and DMSO cause the expression of key genes through epigenetic change. Although sequential exposure with TSA or DMSO induced some liver-specific functions to some extent, the degree of activities are yet lower than those of mature hepatocytes. So it will be necessary to optimize the concentration and exposure time for achieving comparable activities to normal hepatocytes in the future.     

Basic fibroblast growth factor stimulates hepatocyte growth factor/scatter factor secretion by human mesenchymal cells

Basic fibroblast growth factor (bFGF) together with other pleiotropic factors plays an important role in many complex physiological processes such as embryonic development, angiogenesis, and wound repair. Among these factors, hepatocyte growth factor/scatter factor (HGF/SF) which is secreted by cells of mesodermal origin exerts its mito- and motogenic activities on cells of epithelial and endothelial origin. Knowledge of the regulatory mechanisms of HGF/SF may contribute to the understanding of its role in physio-pathological processes. We observed that the secretion of HGF/SF by MRC-5 cells and by other fibroblast-derived cell cultures in conditioned media was enhanced by exposure to bFGF. HGF/SF was measured by the scatter assay, a bioassay for cell motility, and was further characterized by Western blot analysis with anti-HGF/SF antibodies. Exposure of MRC-5 cultures to 10 ng/ml of bFGF resulted already 6 h posttreatment in a threefold higher amount of scatter factor secreted into the medium as compared to untreated cultures. HGF/SF secretion was sustained after bFGF treatment for the following 72 h when increased amounts of HGF/SF were detected both in conditioned media as well as associated to the extracellular matrix. The secretion of HGF/SF in cell supernatants increased dose dependently upon treatment with bFGF starting from basal levels of 6 U/ml and reaching 27 U/ml at 30 ng/ml bFGF, plateauing thereafter. Upregulation of HGF/SF by IL-1, already described by others, was confirmed in this study. Based on our findings an articulated interaction can be speculated for bFGF, HGF/SF, and IL-1, e.g., in tissue regeneration during inflammatory processes or in wound healing. © 1996 Wiley-Liss, Inc.     

Valproic acid promotes differentiation of hepatocyte-like cells from whole human umbilical cord-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are mesoderm-derived cells that are considered a good source of somatic cells for treatment of many degenerative diseases. Previous studies have reported the differentiation of mesodermal MSCs into endodermal and ectodermal cell types beyond their embryonic lineages, including hepatocytes and neurons. However, the molecular pathways responsible for the direct or indirect cell type conversion and the functional ability of the differentiated cells remain unclear and need further research. In the present study, we demonstrated that valproic acid (VPA), which is a histone deacetylase inhibitor, induced an increase in the expression of endodermal genes including CXCR4, SOX17, FOXA1, FOXA2, GSC, c-MET, EOMES, and HNF-1β in human umbilical cord derived MSCs (hUCMSCs). In addition, we found that VPA is able to increase these endodermal genes in hUCMSCs by activating signal transduction of AKT and ERK. VPA pretreatment increased hepatic differentiation at the expense of adipogenic differentiation. The effects of VPA on modulating hUCMSCs fate were diminished by blocking AKT and ERK activation using specific signaling inhibitors. Together, our results suggest that VPA contributes to the lineage conversion of hUCMSCs to hepatic cell fate by upregulating the expression of endodermal genes through AKT and ERK activation.     

Long-term survival and characterisation of human umbilical cord-derived mesenchymal stem cells on dermal equivalents

During early embryogenesis, mesenchymal cells arise from the primitive epithelium and can revert to an epithelial phenotype by passing through mesenchymal-to-epithelial transition (MET). Mesenchymal stem cells (MSC) of the Wharton's Jelly of the umbilical cord (UC-MSC) express pluripotency markers underlining their primitive developmental state. As mesenchymal stem cells from bone marrow (BM-MSC) possess a strong propensity to ameliorate mesenchymal tissue damage, UC-MSC might also be able to differentiate into cells apart from the mesoderm, allowing replacement of ectodermal and mesodermal tissues.     

Basic fibroblast growth factor and its receptors in human embryonic stem cells

Human embryonic stem cells (hESCs) are pluripotent stem cells with long-lasting capacity to self-renew and differentiate into various cell types of endodermal, ectodermal or mesodermal origin. Unlike mouse ESCs (mESCs), which can be maintained in an undifferentiated state simply by adding leukemia inhibitory factor (LIF) into the culture medium, hESCs are notorious for the sustained willingness to differentiate and not yet clearly defined signaling pathways that are crucial for their "stemness". Presently, our knowledge involves only limited number of growth factor signaling pathways that appear to be biologically relevant for stem cell functions in vitro. These include BMP, TGFbeta, Wnt, and FGF signaling pathway. The purpose of this review is to summarize recent data on the expression of FGFs and their receptors in hESCs, and critically evaluate the potential effects of FGF signals for their undifferentiated growth and/or differentiation in context with our current understanding of FGF/FGFR biology.     

Potential surrogate quantitative immunomodulatory potency assay for monitoring human umbilical cord-derived mesenchymal stem cells production

Mesenchymal stem cells (MSCs) play an important role as immune modulator through interaction with several immune cells, including macrophages. In this study, the immunomodulatory potency of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) was demonstrated in the in vivo middle cerebral artery occlusion (MCAo)-induced brain injury rat model and in vitro THP-1-derived macrophages model. At 24 h after induction of MCAo, hUC-MSCs was administered via tail vein as a single dose. Remarkably, hUC-MSCs could inhibit M1 polarization and promote M2 polarization of microglia in vivo after 14 days induction of MCAo. Compared with THP-1-derived macrophages which had been stimulated by lipopolysaccharide, the secretion of proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interferon-γ inducible protein (IP-10), were significantly reduced in the presence of hUC-MSCs. Moreover, the secretion of anti-inflammatory cytokine, interleukin-10 (IL-10), was significantly increased after cocultured with hUC-MSCs. Prostaglandins E2 (PGE2), secreted by hUC-MSCs, is one of the crucial immunomodulatory factors and could be inhibited in the presence of COX2 inhibitor, NS-398. PGE2 inhibition suppressed hUC-MSCs immunomodulatory capability, which was restored after addition of synthetic PGE2, establishing the minimum amount of PGE2 required for immunomodulation. In conclusion, our data suggested that PGE2 is a crucial potency marker involved in the therapeutic activity of hUC-MSCs through macrophages immune response modulation and cytokines regulation. This study provides the model for the development of a surrogate quantitative potency assay of immunomodulation in stem cells production.     

New culture system for human embryonic stem cells: autologous mesenchymal stem cell feeder without exogenous fibroblast growth factor 2

Human embryonic stem (hES) cells have been successfully maintained using human-cell feeder systems or feeder-free systems. However, despite advances in culture techniques, hES cells require supplementation with fibroblast growth factor 2 (FGF-2), an exogenous stemness factor, which is needed to sustain the authentic undifferentiated status. We developed a new culture system for hES cells; this system does not require supplementation with FGF-2 to obtain hES cells that are suitable for tissue engineering and regenerative medicine. This culture system employed mesenchymal stem cells derived from hES cells (hESC-MSCs) as autologous human feeder cells in the absence of FGF-2. The hES cell line SNUhES3 cultured in this new autologous feeder culture system maintained the typical morphology of hES cells and expression of pluripotency-related proteins, SSEA-4, TRA-1-60, OCT4, and alkaline phosphatase, without development of abnormal karyotypes after more than 30 passages. RNA expression of the pluripotency-related genes OCT4 and NANOG was similar to the expression in SNUhES3 cells maintained on xenofeeder STO cells. To identify the mechanism that enables the cells to be maintained without exogenous FGF-2, we checked the secretion of FGF-2 from the mitomycin-C treated autofeeder hESC-MSCs versus xenofeeder STO cells, and confirmed that hESC-MSCs secreted FGF-2 whereas STO cells did not. The level of FGF-2 in the media from the autofeeder system without exogenous FGF-2 was comparable to that from the xenofeeder system with addition of FGF-2. In conclusion, our new culture system for hES cells, which employs a feeder layer of autologous hESC-MSCs, supplies sufficient amounts of secreted FGF-2 to eliminate the requirement for exogenous FGF-2.     

Influence of obstetric factors on osteogenic potential of umbilical cord-derived mesenchymal stem cells

Wharton's jelly from the umbilical cord is a noncontroversial source of mesenchymal stem cells (WJMSCs) with high plasticity, proliferation rate and ability to differentiate towards multiple lineages. WJMSCs from different donors have been characterized for their osteogenic potential. Although there is large evidence of WJMSCs plasticity, recently scientific debate has focused on MSCs selection, establishing predictable elements to discriminate the cells with most promising osteoprogenitor cell potential.     

Induction of multipotency in umbilical cord-derived mesenchymal stem cells cultivated under suspension conditions

Due to the limitations in the clinical application of embryonic stem cells (ESC) and induced pluripotent stem cells, mesenchymal stem cells (MSCs) are now much more interesting for cell-based therapy. Although MSCs have several advantages, they are not capable of differentiating to all three embryonic layers (three germ layers) without cultivation under specific induction media. Hence, improvement of MSCs for cell therapy purposes is under intensive study now. In this study, we isolated MSCs from umbilical cord tissue at the single-cell level, by treatment with trypsin, followed by cultivation under suspension conditions to form a colony. These colonies were trypsin resistant, capable of self-renewal differentiation to the three germ layers without any induction, and they were somewhat similar to ESC colonies. The cells were able to grow in both adherent and suspension culture conditions, expressed both the MSCs markers, especially CD105, and the multipotency markers, i.e., SSEA-3, and had a limited lifespan. The cells were expanded under simple culture conditions at the single-cell level and were homogenous. Further and complementary studies are required to understand how trypsin-tolerant mesenchymal stem cells are established. However, our study suggested non-embryonic resources for future cell-based therapy.     

Basic fibroblast growth factor modulates integrin expression in microvascular endothelial cells.

During angiogenesis capillary endothelial cells undergo a coordinated set of modifications in their interactions with extracellular matrix components. In this study we have investigated the effect of the prototypical angiogenic factor basic fibroblast growth factor (bFGF) on the expression and function of several integrins in microvascular endothelial cells. Immunoprecipitation experiments with antibodies to individual subunits indicated that microvascular cells express at their surface several integrins. These include the alpha 1 beta 1, alpha 2 beta 1, and alpha 3 beta 1 laminin/collagen receptors; the alpha 6 beta 1 laminin receptor; the alpha 5 beta 1 and alpha v beta 1 fibronectin receptors; the alpha 6 beta 4 basement membrane receptor; and the alpha v beta 3 and alpha v beta 5 vitronectin receptors. Treatment with bFGF caused a significant increase in the surface expression of the alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, alpha 6 beta 1, alpha 6 beta 4, and alpha v beta 5 integrins. In contrast, the level of expression of the alpha 1 beta 1 and alpha v beta 3 integrins was decreased in bFGF-treated cells. Immunoprecipitation of metabolically labeled cells indicated that bFGF increases the biosynthesis of the alpha 3, alpha 5, alpha 6, beta 4, and beta 5 subunits and decreases the production of the alpha v and beta 3 subunits. These results suggest that bFGF modulates integrin expression by altering the biosynthesis of individual alpha or beta subunits. In accordance with the upregulation of several integrins observed in bFGF-treated cells, these cells adhered better to fibronectin, laminin, vitronectin, and type I collagen than did untreated cells. The largest differences in beta 1 integrin expression occurred approximately 72 h after exposure to bFGF, at a time when the expression of the endothelial cell-to-cell adhesion molecule endoCAM was also significantly upregulated. In contrast, a shorter exposure to bFGF (24-48 h) was required for the maximal induction of plasminogen activator production in the same cells. Taken together, these results show that bFGF causes significant changes in the level of expression and function of several integrins in microvascular endothelial cells.     

单纯生物学制剂诱导人脐带间充质干细胞向胰岛素分泌细胞快速分化

为探讨用单纯生物学制剂诱导人脐带间充质干细胞(mesenchymal stem cells derived from human umbilical cord,hUC-MSCs)向胰岛素分泌细胞分化的可行性,本研究用胶原酶Ⅱ、胰蛋白酶次序消化及两步离心法从人胎儿完整脐带中分离、纯化出hUC-MSCs;用表皮生长因子、碱性成纤维生长因子、银杏提取液和高糖培养基IMDM诱导hUC-MSCs向胰岛素分泌细胞分化。在hUC-MSCs诱导前后,用倒置显微镜观察其形态变化,RT-PCR检测其胰岛相关基因的表达;双硫腙染色鉴定胰岛样细胞团(islet-like clusters,ILCs);细胞免疫荧光染色检测ILCs中PDX-1和免疫活性胰岛素(immunoreactive insulin,IRI)的表达;化学发光法检测ILCs的IRI分泌量;Western blot鉴定IRI的性质。结果显示:纯化的hUC-MSCs呈间充质干细胞特有的形态特征:长梭形,平行或螺旋形排列;在上述单纯生物学制剂的诱导下,hUC-MSCs逐渐变圆并聚集成团;在25cm2培养瓶的细胞生长面可见上百个ILCs;ILCs表达胰岛特异性基因pdx-1、insulin;ILCs呈PDX-1和IRI免疫染色阳性反应,双硫腙染色呈阳性;ILCs可分泌IRI,但多为胰岛素原(proinsulin,PI)。以上结果提示,用表皮生长因子、碱性成纤维生长因子、银杏提取液和高糖培养基IMDM可诱导hUC-MSCs快速分化为胰岛素分泌细胞,但ILCs功能不够成熟,难以产生足量真胰岛素。     

Monitoring the biology stability of human umbilical cord-derived mesenchymal stem cells during long-term culture in serum-free medium

Mesenchymal stem cells (MSCs) are multipotent adult stem cells that have an immunosuppressive effect. The biological stability of MSCs in serum-free medium during long-term culture in vitro has not been elucidated clearly. The morphology, immunophenotype and multi-lineage potential were analyzed at passages 3, 5, 10, 15, 20, and 25 (P₃, P₅, P₁₀, P₁₅, P₂₀, and P₂₅, respectively). The cell cycle distribution, apoptosis, and karyotype of human umbilical cord-derived (hUC)-MSCs were analyzed at P₃, P₅, P₁₀, P₁₅, P₂₀, and P₂₅. From P₃ to P₂₅, the three defining biological properties of hUC-MSCs [adherence to plastic, specific surface antigen expression, multipotent differentiation potential] met the standards proposed by the International Society for Cellular Therapy for definition of MSCs. The cell cycle distribution analysis at the P₂₅ showed that the percentage of cells at G0/G1 was increased, compared with the cells at P₃ (P < 0.05). Cells at P₂₅ displayed an increase in the apoptosis rate (to 183 %), compared to those at P₃ (P < 0.01). Within subculture generations 3–20 (P₃–P₂₀), the differences between the cell apoptotic rates were not statistically significant (P > 0.05). There were no detectable chromosome eliminations, displacements, or chromosomal imbalances, as assessed by the karyotyping guidelines of the International System for Human Cytogenetic Nomenclature (ISCN, 2009). Long-term culture affects the biological stability of MSCs in serum-free MesenCult-XF medium. MSCs can be expanded up to the 25th passage without chromosomal changes by G-band. The best biological activity period and stability appeared between the third to 20th generations.     

人脐带间充质干细胞作为维持人胚胎干细胞生长饲养层细胞的研究

目的寻找可以维持人胚胎干细胞未分化生长的人源性细胞作为饲养层细胞,从而解决使用鼠源性细胞作为饲养层带来的安全问题。方法尝试以人脐带间充质干细胞作为饲养层细胞来培养人胚胎干细胞,检验其是否可以维持人胚胎干细胞的未分化生长状态。用胶原酶消化法分离人脐带间充质干细胞,光镜下观察细胞形态;流式细胞仪检测其表面标志;诱导人脐带间充质干细胞向成骨细胞和脂肪细胞进行分化。将人胚胎干细胞系H1接种于丝裂霉素C灭活后的人脐带间充质干细胞上,每隔5d进行一次传代。培养20代后,对人胚胎干细胞特性进行相关检测,包括细胞形态、碱性磷酸酶染色、相关多能性基因的表达、分化能力。结果从人脐带中分离出的间充质干细胞为梭形,呈平行排列生长或漩涡状生长;细胞高表达CD44、CD29、CD73、CD105、CD90、CD86、CD147、CD117,不表达CD14、CD38、CD133、CD34、CD45、HLA-DR;具有分化成脂肪细胞和成骨细胞的潜能。人胚胎干细胞在人脐带间充质干细胞饲养层上培养20代后,继续保持人胚胎干细胞的典型形态,碱性磷酸酶染色为阳性,免疫荧光染色显示OCT4、Nanog、SSEA4、TRA-1-81、TRA-1-60的表达为阳性,SSEA1表达为阴性,体外悬浮培养可以形成拟胚体。结论人脐带间充质干细胞可以作为人胚胎干细胞的饲养层细胞,支持其生长,并维持其未分化生长状态。     

Human umbilical cord-derived mesenchymal stem cells differentiate into epidermal-like cells using a novel co-culture technique

Human umbilical cord-derived mesenchymal stem cells (hUCMSCs) isolated from human umbilical Wharton’s Jelly are a population of primitive and pluripotent cells. In specific conditions, hUCMSCs can differentiate into various cells, including adipocytes, osteoblasts, chondrocytes, neurocytes, and endothelial cells. However, few studies have assessed their differentiation into epidermal cells in vitro. To assess the potential of hUCMSCs to differentiate into epidermal cells, a microporous membrane-based indirect co-culture system was developed in this study. Epidermal stem cells (ESCs) were seeded on the bottom of the microporous membrane, and hUCMSCs were seeded on the top of the microporous membrane. Cell morphology was assessed by phase contrast microscopy, and the expression of early markers of epidermal cell lineage, P63, cytokeratin19 (CK19), and β1-integrin, was determined by immunofluorescence, Western blot, and quantitative real-time PCR (Q-PCR) analyses. hUCMSC morphology changed from spindle-like to oblate or irregular with indirect co-culture with ESCs; they also expressed greater levels P63, CK19, and β1-integrin mRNA and protein compared to the controls (p < 0.01). As compared to normal co-cultures, indirect co-culture expressed significantly greater CK19 protein (p < 0.01). Thus, hUCMSCs may have the capability to differentiate into the epidermal lineage in vitro, which may be accomplished through this indirect co-culture model.     

Cotransplantation of human umbilical cord-derived mesenchymal stem cells and umbilical cord blood-derived CD34+ cells in a rabbit model of myocardial infarction

The objective of the study is to investigate the effect of hypoxic preconditioning on the immunomodulatory properties of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) and the effect of cotransplantation of hUC-MSCs and human umbilical cord blood (hUCB)-derived CD34⁺ cells in a rabbit model of myocardial infarction. hUC-MSCs with or without hypoxic preconditioning by cobalt chloride were plated in a 24-well plate, and then cocultured with hUCB-CD34⁺ cells and PBMCs for 96 h at 37 °C in a 5 % CO₂ incubator. For the negative control, hUC-MSCs were omitted. The groups were divided as follows: A1 = HP-MSCs + hUCB-CD34⁺ cells + PBMC, A2 = hUC-MSCs + hUCB-CD34⁺ cells + PBMC, Negative Control = hUCB-CD34⁺ cells + PBMC. Culture supernatants of each group were collected, and the IL-10 and IFN-γ levels were measured by ELISA. A rabbit model of MI was established using a modified Fujita method. The animals were then randomized into three groups and received intramyocardial injections of 0.4 ml of PBS alone (n = 8, PBS group), hUC-MSCs in PBS (n = 8, hUC-MSCs group), or hUC-MSCs + CD34⁺ cells in PBS (n = 8, Cotrans group), at four points in the infarct border zone. Echocardiography was performed at baseline, 4 weeks after MI induction, and 4 weeks after cell transplantation, respectively. Stem cell differentiation and neovascularization in the infracted area were characterized for the presence of cardiac Troponin I (cTnI) and CD31 by immunohistochemical staining, and the extent of myocardial fibrosis was evaluated by hematoxylin and eosin (H&E) and Masson’s trichrome. IFN-γ was 27.00 ± 1.11, 14.20 ± 0.81, and 7.22 ± 0.14 pg/ml, and IL-10 was 31.68 ± 3.08, 61.42 ± 1.08, and 85.85 ± 1.80 pg/ml for the Control, A1 and A2 groups, respectively, which indicated that hUCB-CD34⁺ cells induced immune reaction of peripheral blood mononuclear cells, whereas both hUC-MSCs and HP-MSCs showed an immunosuppressive effect, which, however, was attenuated by hypoxic preconditioning. The Cotrans group had less collagen deposition in the infarcted myocardium and better heart function than the hUC-MSCs or PBS group. The presence of cTnI-positive cells and CD31-positive tubular structures indicated the differentiation of stem cells into cardiomyocytes and neovascularization. The microvessel density was 12.19 ± 3.05/HP for the hUC-MSCs group and 31.63 ± 2.45/HP for the Cotrans group, respectively (P < 0.01). As a conclusion, both hUC-MSCs and HP-MSCs have an immunosuppressive effect on lymphocytes, which, however, can be attenuated by hypoxic preconditioning. Cotransplantation of hUC-MSCs and hUCB-CD34⁺ cells can improve heart function and decrease collagen deposition in post-MI rabbits. Thus, a combined regimen of hUC-MSCs and hUCB-CD34⁺ cells would be more desirable than either cells administered alone. This is most likely due to the increase of cardiomyocytes and enhanced angiogenesis in the infarcted myocardium.     

Synthetic polymers as xeno-free materials for stabilizing basic fibroblast growth factor in human mesenchymal stem cell cultures

Series of sulfonated polymers were evaluated as additives in cell culture media. Some of the compounds, such as sulfated polyvinyl alcohol (PVA), prevented denaturation and loss of basic fibroblast growth factor during cell culture and enhanced human mesenchymal stem cell proliferation. These compounds are xeno-free alternatives of heparin, an animal-derived sulfated saccharide, often used as an additive. To the best our knowledge, this study is the first to show that chemically defined synthetic chemicals, such as sulfated polyvinyl alcohol, can be used for this purpose.     

Forced expression of indoleamine-2,3-dioxygenase in human umbilical cord-derived mesenchymal stem cells abolishes their anti-apoptotic effect on leukemia cell lines in vitro

The ability of mesenchymal stem cells (MSCs) to preserve cancer cells potentially constitutes the adverse effect of MSC-based cell therapy in the context of hematologic malignancy. In an effort to reverse this undesirable feature of MSCs, we manipulated human umbilical cord-derived MSCs (UC-MSCs) to express indoleamine-2,3-dioxygenase (IDO), an enzyme that induces immune suppression by inhibiting T cell proliferation and triggering apoptosis in immune cells. Cultures of human UC-MSCs were generated by plastic adherence method. Full-length cDNA of human IDO was cloned into adenovirus shuttle vector. Then, the recombinant virus harboring IDO gene was produced in 293 cells and used to infect UC-MSCs. Expression of IDO protein was detected within infected UC-MSCs, and accumulation of kynurenine was observed in the supernatant. Two human leukemia cell lines, Jurkat and HL-60, were cultured on the monolayer of native or infected UC-MSCs, respectively. It was observed that forced IDO expression abolished the anti-apoptotic effect of UC-MSCs on these leukemia cells and enhanced their proliferation inhibitory effect on activated human lymphocytes as well as leukemia cells. These results suggested that equipping MSCs with IDO could be one of the reasonable strategies to reverse their cancer-supportive effect unfavorable for clinical applications.