Mesenchymal stem cells induce apoptosis of activated T cells

Impairment in immunomodulatory function of mesenchymal stem cells from multiple myeloma patients

BACKGROUND AND AIMS

Abnormality of immune regulation exists in multiple myeloma (MM). Mesenchymal stem cells (MSCs), a key regulator for immunomodulatory function, have decreased osteogenic potential in MM patients. Here we investigated the immunomodulatory function of MSCs from MM patients (MM-MSCs) and its relationship with decreased osteogenic potential.

METHODS

Real-time PCR was performed to detect the cytokines expressed in MM-MSCs (n = 22) and MSCs from normal donors (ND-MSCs, n = 11). Lymphocyte proliferative assay was used to detect the effect of MSCs on T cell proliferation. The effect of MSCs on T-cell cycle and T-cell activation markers expression were analyzed by flow cytometry. Flow cytometry and Western blot were used to detect apoptosis of T cells. Influence of T cells on osteogenic potential of MSCs was detected.

RESULTS

MM-MSCs exhibited increased expression of TGF-β1, IL-6, IL-3, TNF-α and RANKL and decreased expression of TGF-β2, TGF-β3 and FasL. The inhibitory effect of MM-MSCs on T.cell proliferative ability was attenuated. ND-MSCs silence more T cells in G0/G1 phase than MM-MSCs. The apoptosis-promoting effect of MM-MSCs on T cells seemed to be dampened. Expression of T-cell activation markers was significantly inhibited by ND-MSCs. T cells from normal donors possessed the ability to promote osteoblastic differentiation of ND-MSCs, but this ability of T cells both directly from MM patients and co-cultured with MM-MSCs was impaired.

CONCLUSIONS

MSCs from MM patients showed impaired immunoinhibitory capability on T cells, which in turn lose the ability to stimulate osteogenesis of MSCs.

The pathology of bleomycin-induced fibrosis is associated with loss of resident lung mesenchymal stem cells that regulate effector T-cell proliferation

Tissue-resident mesenchymal stem cells (MSCs) are important regulators of tissue repair or regeneration, fibrosis, inflammation, angiogenesis, and tumor formation. Here, we define a population of resident lung MSCs (luMSCs) that function to regulate the severity of bleomycin injury via modulation of the T-cell response. Bleomycin-induced loss of these endogenous luMSCs and elicited fibrosis (pulmonary fibrosis), inflammation, and pulmonary arterial hypertension (PAH). Replacement of resident stem cells by administration of isolated luMSCs attenuated the bleomycin-associated pathology and mitigated the development of PAH. In addition, luMSC modulated a decrease in numbers of lymphocytes and granulocytes in bronchoalveolar fluid and demonstrated an inhibition of effector T-cell proliferation in vitro. Global gene expression analysis indicated that the luMSCs are a unique stromal population differing from lung fibroblasts in terms of proinflammatory mediators and profibrotic pathways. Our results demonstrate that luMSCs function to protect lung integrity after injury; however, when endogenous MSCs are lost, this function is compromised illustrating the importance of this novel population during lung injury. The definition of this population in vivo in both murine and human pulmonary tissue facilitates the development of a therapeutic strategy directed at the rescue of endogenous cells to facilitate lung repair during injury.

Mesenchymal stem cells and inflammatory cardiomyopathy: cardiac homing and beyond

Under conventional heart failure therapy, inflammatory cardiomyopathy usually has a progressive course, merging for alternative interventional strategies. There is accumulating support for the application of cellular transplantation as a strategy to improve myocardial function. Mesenchymal stem cells (MSCs) have the advantage over other stem cells that they possess immunomodulatory features, making them attractive candidates for the treatment of inflammatory cardiomyopathy. Studies in experimental models of inflammatory cardiomyopathy have consistently demonstrated the potential of MSCs to reduce cardiac injury and to improve cardiac function. This paper gives an overview about how inflammation triggers the functionality of MSCs and how it induces cardiac homing. Finally, the potential of intravenous application of MSCs by inflammatory cardiomyopathy is discussed.

Fibroblast Growth Factor-2 Enhances Expansion of Human Bone Marrow-Derived Mesenchymal Stromal Cells without Diminishing Their Immunosuppressive Potential

Allogeneic hematopoietic stem cell transplantation is the main curative therapy for many hematologic malignancies. Its potential relies on graft-versus-tumor effects which associate with graft-versus-host disease. Mesenchymal stromal cells (MSCs) possess immunomodulatory properties that make them attractive therapeutic alternatives. We evaluated the in vitro immunosuppressive activity of medium conditioned by human MSCs from 5 donors expanded 13 passages with or without FGF-2. FGF-2 supplementation increased expansion 3,500- and 240,000-fold by passages 7 and 13, respectively. There were no differences in immunosuppressive activity between media conditioned by passage-matched cells expanded under different conditions, but media conditioned by FGF-treated MSCs were superior to population doubling-matched controls. The immunosuppressive activity was maintained in three of the preparations but decreased with expansion in two. The proliferation induced by FGF-2 did not result in loss of immunosuppressive activity. However, because the immunosuppressive activity was not consistently preserved, caution must be exercised to ensure that the activity of the cells is sufficient after extensive expansion.

Human but not murine multipotent mesenchymal stromal cells exhibit broad-spectrum antimicrobial effector function mediated by indoleamine 2,3-dioxygenase

Human multipotent mesenchymal stromal cells (MSCs) exhibit multilineage differentiation potential, support hematopoiesis, and inhibit proliferation and effector function of various immune cells. On the basis of these properties, MSC are currently under clinical investigation in a range of therapeutic applications including tissue repair and immune-mediated disorders such as graft-versus-host-disease refractory to pharmacological immunosuppression. Although initial clinical results appear promising, there are significant concerns that application of MSC might inadvertently suppress antimicrobial immunity with an increased risk of infection. We demonstrate here that on stimulation with inflammatory cytokines human MSC exhibit broad-spectrum antimicrobial effector function directed against a range of clinically relevant bacteria, protozoal parasites and viruses. Moreover, we identify the tryptophan catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) as the underlying molecular mechanism. We furthermore delineate significant differences between human and murine MSC in that murine MSC fail to express IDO and inhibit bacterial growth. Conversely, only murine but not human MSC express inducible nitric oxide synthase on cytokine stimulation thus challenging the validity of murine in vivo models for the preclinical evaluation of human MSC. Collectively, our data identify human MSC as a cellular immunosuppressant that concurrently exhibits potent antimicrobial effector function thus encouraging their further evaluation in clinical trials.

Concise review: Dissecting a discrepancy in the literature: do mesenchymal stem cells support or suppress tumor growth?

The discovery that mesenchymal stem cells (MSCs) are recruited into tumors has led to a great deal of interest over the past decade in the function of MSCs in tumors. To address this, investigators have used a variety of tumor models in which MSCs are added exogenously to determine their impact on tumor development. Interestingly, many studies have reported contradicting results, with some investigators finding that MSCs promote tumor growth and others reporting that MSCs inhibit tumor growth. Many mechanisms have been reported to account for these observations, such as chemokine signaling, modulation of apoptosis, vascular support, and immune modulation. In this review, we analyzed the differences in the methodology of the studies reported and found that the timing of MSC introduction into tumors may be a critical element. Understanding the conditions in which MSCs enhance tumor growth and metastasis is crucial, both to safely develop MSCs as a therapeutic tool and to advance our understanding of the role of tumor stroma in carcinogenesis.

Mesenchymal stem cells improve murine acute coxsackievirus B3-induced myocarditis

Aims

Coxsackievirus B3 (CVB3)-induced myocarditis, initially considered a sole immune-mediated disease, also results from a direct CVB3-mediated injury of the cardiomyocytes. Mesenchymal stem cells (MSCs) have, besides immunomodulatory, also anti-apoptotic features. In view of clinical translation, we first analysed whether MSCs can be infected by CVB3. Next, we explored whether and how MSCs could reduce the direct CVB3-mediated cardiomyocyte injury and viral progeny release, in vitro, in the absence of immune cells. Finally, we investigated whether MSC application could improve murine acute CVB3-induced myocarditis.

Methods and results

Phase contrast pictures and MTS viability assay demonstrated that MSCs did not suffer from CVB3 infection 4–12–24–48 h after CVB3 infection. Coxsackievirus B3 RNA copy number decreased in this time frame, suggesting that no CVB3 replication took place. Co-culture of MSCs with CVB3-infected HL-1 cardiomyocytes resulted in a reduction of CVB3-induced HL-1 apoptosis, oxidative stress, intracellular viral particle production, and viral progeny release in a nitric oxide (NO)-dependent manner. Moreover, MSCs required priming via interferon-γ (IFN-γ) to exert their protective effects. In vivo, MSC application improved the contractility and relaxation parameters in CVB3-induced myocarditis, which was paralleled with a reduction in cardiac apoptosis, cardiomyocyte damage, left ventricular tumour necrosis factor-α mRNA expression, and cardiac mononuclear cell activation. Mesenchymal stem cells reduced the CVB3-induced CD4− and CD8− T cell activation in an NO-dependent way and required IFN-γ priming.

Conclusion

We conclude that MSCs improve murine acute CVB3-induced myocarditis via their anti-apoptotic and immunomodulatory properties, which occur in an NO-dependent manner and require priming via IFN-γ.

IDO1 and IDO2 gene expression analysis by quantitative polymerase chain reaction

Immunomodulatory properties of IDO1 relate to tryptophan catabolism. The degradation of tryptophan by IDO1 leads to suppression of T cell responses. Recently, another enzyme with IDO-like activity, indoleamine 2,3-dioxygenase-like-protein 1 (INDOL1, IDO2), has been described in both mice and humans. In order to study the gene expression of IDO1 and IDO2, we have developed a quantitative PCR (qPCR) assay. In an exploratory application to the study of the differential expression of IDO1 and IDO2 by professional antigen-presenting cells and MSCs (mesenchymal stromal cells) under the influence of interferon-γ (IFN-γ) and T-lymphocyte conditioned media (TCM), substantial differences were observed. IDO expression measured by qPCR was valid and reliable in the cell types investigated. Further studies are needed to delineate factors driving IDO expression in MSCs.

Mesenchymal stem cell therapy for chronic renal failure

IMPORTANCE OF THE FIELD

Chronic kidney disease (CKD) has become a worldwide public health problem. Renal transplantation is the treatment of choice for end-stage renal disease, but is limited by a small number of organ donors and the immune barrier. To overcome these problems, new therapeutic strategies for tissue repair have recently emerged.

AREAS COVERED IN THIS REVIEW

We discuss the therapeutic potential of mesenchymal stem cells (MSCs) in kidney injury and examine the latest reports providing evidence supporting MSC efficacy in the treatment of chronic renal failure (CRF).

WHAT THE READER WILL GAIN

MSCs improve histological and functional outcomes in various CRF model systems. Paracrine effects rather than transdifferentiation might result in the prevention of progressive renal failure. In addition, MSCs can reprogram kidney cell differentiation, and modulate neo-kidney transplantation in CRF.

TAKE HOME MESSAGE

Although many practical problems remain to be addressed, treatment with MSCs will enter the mainstream of CRF treatment.

Mouse mesenchymal stem cells suppress antigen-specific TH cell immunity independent of indoleamine 2,3-dioxygenase 1 (IDO1)

Due to their immunosuppressive properties, human mesenchymal stem cells (hMSC) represent a promising tool for cell-based therapies of autoimmune diseases such as multiple sclerosis (MS). Mouse MSC (mMSC) have been used extensively to characterize and optimize route of administration, motility, cellular targets, and immunosuppressive mechanisms in mouse models of autoimmune diseases, such as experimental autoimmune encephalomyelitis (EAE). Tryptophan (trp) catabolism by indolamine-2,3-dioxygenase 1 (IDO1) is a chief endogenous metabolic pathway that tightly regulates unwanted immune responses through depletion of trp and generation of immunosuppressive kynurenines (kyn). IDO1 activity contributes to the immunosuppressive phenotype of hMSC. Here, we demonstrate that although IDO1 is inducible in bone marrow-derived mMSC by proinflammatory stimuli such as interferon-g (IFN-g) and ligands of toll-like receptors (TLR), it does not lead to catabolism of trp in vitro. This failure to catabolize trp is not due to defective TLR signaling as demonstrated by induction of interleukin 6 (IL-6) by TLR activation. While mMSC suppressed the activation of antigen-specific myelin oligodendrocyte glycoprotein (MOG)-reactive T-cell receptor (TCR) transgenic T-helper (TH) cells in co-culture, neither pharmacologic inhibition nor genetic ablation of IDO1 reversed this suppressive effect. Finally, systemic administration of both, IDO1-proficient and phenotypically identical IDO1-deficient mMSC, equally resulted in amelioration of EAE. mMSC, unlike hMSC, do not display IDO1-mediated suppression of antigen-specific T-cell responses.

Interleukin-10 delivery via mesenchymal stem cells: a novel gene therapy approach to prevent lung ischemia-reperfusion injury

Ischemia-reperfusion (IR) injury is an important cause of primary graft failure in lung transplantation. In this study, viral interleukin-10 (vIL-10)-engineered mesenchymal stem cells (MSCs) were tested for their ability to prevent lung IR injury. Bone marrow-derived MSCs were transduced with rvIL-10-retrovirus. After 120 min of warm left lung ischemia, rats received approximately 15 x 10(6) vIL-10-engineered MSCs (MSC-vIL-10), empty vector-engineered MSCs (MSC-vec), or saline intravenously. Mean blood oxygenation (PaO(2)/FiO(2) ratio, mmHg) was measured at 4 hr, 24 hr, 72 hr, and 7 days. As early as 4 hr post-IR injury with MSC-vIL-10 treatment, blood oxygenation was significantly (p < 0.05) improved (319 +/- 94; n = 7) compared with untreated (saline) controls (63 +/- 19; n = 6). At 24 hr post-IR injury, in the MSC-vIL-10-treated group there was a further increase in blood oxygenation (353 +/- 105; n = 10) compared with the MSC-vec group (138 +/- 86; n = 9) and saline group (87 +/- 39; n = 10). By 72 hr, oxygenation reached normal (475 +/- 55; n = 9) in the MSC-vIL-10-treated group but not in the saline-treated and MSC-vec-treated groups. At 4 hr after IR injury, lungs with MSC-vIL10 treatment had a lower (p < 0.05) injury score (0.9 +/- 0.4) compared with lungs of the untreated (saline) group (2.5 +/- 1.4) or MSC-vec-treated group (2 +/- 0.4). Lung microvascular permeability and wet-to-dry weight ratios were markedly lower in the MSC-vIL10 group compared with untreated (saline) controls. ISOL (in situ oligonucleotide ligation for DNA fragmentation detection) and caspase-3 staining demonstrated significantly (p < 0.05) fewer apoptotic cells in MSC-vIL10-treated lungs. Animals that received MSC-vIL10 therapy had fewer (p < 0.05) CD4(+) and CD8(+) T cells in bronchoalveolar lavage fluid compared with untreated control animals. A therapeutic strategy using vIL-10-engineered MSCs to prevent IR injury in lung transplantation seems promising.

Advances in research of the reversal of liver fibrosis by transplantation of bone marrow mesenchymal stem cells

Bone marrow mesenchymal stem cells (BMSCs) are a group of stem cells capable of multilineage differentiation. Under given conditions, BMSCs can differentiate into a variety of cells, such as osteoblasts, chondrocytes, adipocytes, neuron-like cells and hepatocytes. In recent years, numerous studies have shown that BMSCs can not only inhibit and reduce liver fibrosis but also induce immunosuppression and immune tolerance. Therefore, transplantation of BMSCs can be used to treat end-stage liver disease.

Indoleamine 2,3-dioxygenase in human hematopoietic stem cell transplantation

In recent years tryptophan metabolism and its rate limiting enzyme indoleamine 2,3-dioxygenase (IDO) have attracted increasing attention for their potential to modulate immune responses including the regulation of transplantation tolerance. The focus of this review is to discuss some features of IDO activity which particularly relate to hematopoietic stem cell transplantation (HSCT). HSCT invariably involves the establishment of some degree of a donor-derived immune system in the recipient. Thus, the outstanding feature of tolerance in HSCT is that in this type of transplantation it is not rejection, which causes the most severe problems to HSCT recipients, but the reverse, graft-versus-host (GvH) directed immune responses. We will discuss the peculiar role of IDO activity and accelerated tryptophan metabolism at the interface between immune activation and immune suppression and delineate from theoretical and experimental evidence the potential significance of IDO in mediating tolerance in HSCT. Finally, we will examine therapeutic options for exploitation of IDO activity in the generation of allo-antigen-specific tolerance, i.e. avoiding allo-reactivity while maintaining immunocompetence, in HSCT.

Stem cell paracrine actions and tissue regeneration

Stem cells have emerged as a key element of regenerative medicine therapies due to their inherent ability to differentiate into a variety of cell phenotypes, thereby providing numerous potential cell therapies to treat an array of degenerative diseases and traumatic injuries. A recent paradigm shift has emerged suggesting that the beneficial effects of stem cells may not be restricted to cell restoration alone, but also due to their transient paracrine actions. Stem cells can secrete potent combinations of trophic factors that modulate the molecular composition of the environment to evoke responses from resident cells. Based on this new insight, current research directions include efforts to elucidate, augment and harness stem cell paracrine mechanisms for tissue regeneration. This article discusses the existing studies on stem/progenitor cell trophic factor production, implications for tissue regeneration and cancer therapies, and development of novel strategies to use stem cell paracrine delivery for regenerative medicine.

Targeting improves MSC treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, is an inflammatory autoimmune disease characterized by T-cell infiltration to the colon. Mesenchymal stem cells (MSCs) have the potential to rescue IBD owing to their immunosuppressive capabilities and clinical studies have shown positive influence on intestinal graft versus host disease. We demonstrate here a new method to coat MSCs with antibodies against addressins to enhance their delivery to the colon and thereby increase the therapeutic effectiveness. Bioluminescence imaging (BLI) demonstrated that vascular cell adhesion molecule antibody (Ab)-coated MSCs (Ab(VCAM-1)- MSCs) had the highest delivery efficiency to inflamed mesenteric lymph node (MLN) and colon compared to untreated MSCs, Ab(isotype)-MSCs, and Ab(MAdCAM)-MSCs. Therapeutically, when mice with IBD were injected with addressin Ab-coated MSCs, they showed dramatically improved survival rates, higher IBD therapeutic scores, and significantly improved body weight gain compared to mice injected with MSCs only, isotype Ab, free Ab plus MSCs, or vehicle-only controls. These data demonstrate that anti-addressin Ab coating on MSC increased cell delivery to inflamed colon and increased the efficacy of MSC treatment of IBD. This is the first study showing an increased therapeutic efficacy when stem cells are first coated with antibodies specifically target them to inflamed sites.

Photochemotherapy induces the apoptosis of monocytes without impairing their function

BACKGROUND

Extracorporeal photopheresis (ECP) is a powerful therapy currently used to treat various hematological disorders as in graft versus host disease. Clinical data clearly demonstrate its efficacy and immunomodulation toward the pathogenic T cells. However, ECP mechanism of action is still poorly understood. Monocytes represent up to 30% of the total amount of treated cells and are known to play an important role in adaptive immunity. However, data from previous reports analyzing the effect of psoralen and UV-A irradiation (PUVA) on their functions are heterogeneous. In this study, we focused on the effect of PUVA on human monocytes functions in adaptive immunity.

DESIGN AND METHODS

Purified human monocytes were treated in vitro by PUVA. We measured their kinetic of apoptosis after the treatment. We also determine whether their phenotype and functionalities were modified. Finally, we assessed the functionalities of PUVA-treated monocytes-derived dendritic cells (DC).

RESULTS

PUVA treatment sentenced purified monocytes to die in 6 days and immediately altered their migratory capacities without impairing their ability of endocytosis. It also up-regulated co-stimulatory molecules and production of inflammatory cytokines on activation and consequently stimulated allogeneic or autologous T cells as efficiently as untreated monocytes. Moreover, PUVA-treated monocytes retained their ability to differentiate into fully functional DC that maturated and stimulated T cells as well as normal DC.

CONCLUSIONS

Our data demonstrate that monocytes undergo apoptosis and loose a part of their migratory capacity after ECP and the surviving cell functionalities are not impaired, suggesting that monocytes have a minor effect on ECP-mediated immunomodulation.

Human umbilical cord mesenchymal stem cells hUC-MSCs exert immunosuppressive activities through a PGE2-dependent mechanism

Human umbilical-cord-derived mesenchymal stem cells (hUC-MSCs) constitute an attractive alternative to bone-marrow-derived MSCs for potential clinical applications because of easy preparation and lower risk of viral contamination. In this study, both proliferation of human peripheral blood mononuclear cells (hPBMCs) and their IFN-gamma production in response to mitogenic or allogeneic stimulus were effectively inhibited by hUC-MSCs. Co-culture experiments in transwell systems indicated that the suppression was largely mediated by soluble factor(s). Blocking experiments identified prostaglandin E(2) (PGE(2)) as the major factor, because inhibition of PGE(2) synthesis almost completely mitigated the immunosuppressive effects, whereas neutralization of TGF-beta, IDO, and NO activities had little effects. Moreover, the inflammatory cytokines, IFN-gamma and IL-1beta, produced by hPBMCs upon activation notably upregulated the expression of cyclooxygenase-2 (COX-2) and the production of PGE(2) by hUC-MSCs. In conclusion, our data have demonstrated for the first time the PGE(2)-mediated mechanism by which hUC-MSCs exert their immunomodulatory effects.

What's new in cardiac cell therapy? Allogeneic bone marrow stromal cells as "universal donor cells"

Cardiac cell therapies offer distinct and exciting advantages over current treatments to prevent postinfarction heart failure because they can reverse ventricular remodeling and improve function, but only if the implanted stem cells contribute biological functions and achieve prolonged engraftment within the hostile environment of the damaged heart. Unfortunately, function is diminished in autologous stem cells isolated from older patients and those with comorbidities, and so clinical trials testing the implantation of healthy, allogeneic bone marrow-derived stromal cells (MSCs) isolated from young donors are currently underway. MSCs are unique because, in addition to exerting paracrine effects that restore blood flow and recruit endogenous stem cells to the infarct, they exhibit immune-modulating properties in culture that-if retained after allogeneic implantation-imply the cells may escape immune recognition within the heart. At present, the scope of MSC immune modulation after implantation is unclear.

Inflammation modifies the pattern and the function of Toll-like receptors expressed by human mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are involved in tissue repair and in the regulation of immune responses. MSC express Toll-like receptors (TLR) known to link innate and adaptive immunity. We hypothesized that TLR signaling could influence human MSC (hMSC) function. Here, we show that hMSC express TLR1, TLR2, TLR3, TLR4, TLR5, and TLR6 but not TLR7, TLR8, TLR9, and TLR10. In inflammatory conditions mimicked by culturing hMSC in an inflammatory environment, TLR2, TLR3, and TLR4 are upregulated, whereas TLR6 is downregulated. Interleukin (IL)-1 beta, IL-6, IL-12p35 and transforming growth factor-beta mRNAs are constitutively expressed by hMSC. Inflammation leads to an increase in IL-1 beta, IL-6, IL-12p35, and transforming growth factor-beta transcription and is characterized by IL-23p19 and IL-27p28 transcription. In this setting, poly(I:C) further augments IL-6, IL-12p35, IL-23p19, and IL-27p28 transcription, whereas lipopolysaccharide (LPS) increases IL-23p19 and IL-27p28 transcription. By upregulating TLR3 and TLR4 transcription, inflammation increases the hMSC responsiveness to LPS and poly(I:C), leading to a proinflammatory shift in their cytokine profile. The hMSC osteogenic potential does not change after TLR triggering but stimulation with LPS and poly(I:C) results in a decrease in their immunosuppressive capabilities. In conclusion, TLR activation in hMSC may affect their function and could modify their in vivo fate, especially in an inflammatory context.

Fibroblastic colony-forming unit bone marrow cells delay progression to gastric dysplasia in a helicobacter model of gastric tumorigenesis

Bone marrow mesenchymal stem cells (MSCs) have been shown to have immune modulatory effects. Despite efforts to identify these cells in vivo, to date, MSCs have been defined mainly by their in vitro cell characteristics. Here, we show that Lin(-)CD44(hi)Sca1(-)cKit+CD34(-) cells make up approximately 0.5%-1% of murine whole bone marrow cells and yield nearly an equal amount of fibroblastic colony-forming units (CFU-F) as whole bone marrow. After transplantation into lethally irradiated recipients, Lin(-)CD44(hi)Sca1(-)cKit+CD34(-) cells engrafted in the bone marrow long-term and demonstrated characteristics of MSCs, including capacity to differentiate into osteoblasts and adipocytes. To examine whether Lin(-)CD44(hi)Sca1(-)cKit+CD34(-) cells have immune modulatory effects, in vitro coculture with activated CD4+ T-cells resulted in decreased Th17 cell differentiation by Lin(-)CD44(hi)Sca1(-)cKit+CD34(-) cells. Furthermore, serial infusions with Lin(-)CD44(hi)Sca1(-)cKit+CD34(-) cells reduced the progression to low-grade gastric dysplasia in mice infected with chronic Helicobacter felis (p = .038). This correlated with reduced gastric interleukin (IL)-17F, IL-22, and ROR-gammat gene expression in responding mice (p < .05). These data suggest that bone marrow derived Lin(-)CD44(hi)Sca1(-)cKit+CD34(-) cells have characteristics of MSCs and reduce progression of early gastric tumorigenesis induced by chronic H. felis infection. The prevention of dysplastic changes may occur through inhibition of Th17-dependent pathways.

Mesenchymal stromal cells promote or suppress the proliferation of T lymphocytes from cord blood and peripheral blood: the importance of low cell ratio and role of interleukin-6

BACKGROUND AIMS

Mesenchymal stromal cells (MSC) have been shown to possess immunomodulatory functions and proposed as a tool for managing or preventing graft-versus-host disease (GvHD) as well as promoting clinical transplantation tolerance. We investigated the capacity of human bone marrow (BM) MSC to modulate the proliferation of T cells obtained from peripheral blood (PB) and umbilical cord blood (CB). We addressed the importance of the MSC:T-cell ratio, requirement for cell contact and impact of soluble factors on the MSC-mediated effects. We also analyzed whether regulatory T cells could be modulated by MSC in co-cultures.

METHODS

The effect of different MSC concentrations on T-cell proliferation induced by allogeneic, mitogenic or CD3/CD28 stimulation was analyzed using bromodeoxyuridine (BrdU) incorporation and carboxyfluorescein diacetate-succinimidyl ester (CFDA-SE) labeling. The level of regulatory T cells was assessed using quantitative real-time polymerase chain reaction (PCR) and flow cytometry analysis.

RESULTS

MSC induced a dose- and contact-dependent inhibition of T-cell proliferation but lymphocytes from CB and PB were differentially affected. At low concentrations, MSC supported both CB and PB T-cell proliferation, rather than inhibiting their proliferation. This supportive effect was contact independent and soluble factors such interleukin-6 (IL-6) appeared to be involved. Interestingly, among the expanded T-cell population in both CB and PB, regulatory T cells were increased and were a part of the new cells promoted by MSC at low doses.

CONCLUSIONS

MSC represent an attractive tool for reducing the lymphocyte response by inhibiting T-cell activation and proliferation as well as promoting tolerance by maintaining and promoting the expansion of regulatory cells. Nevertheless, the dual ability of MSC to either sustain or suppress T-cell proliferation according to conditions should be considered in the context of clinical applications.

Intravenous administration of 99mTc-HMPAO-labeled human mesenchymal stem cells after stroke: in vivo imaging and biodistribution

Human mesenchymal stem cells (hMSC) are a promising source for cell therapy after stroke. To deliver these cells, an IV injection appears safer than a local graft. We aimed to assess the whole-body biodistribution of IV-injected (99m)Tc-HMPAO-labeled hMSC in normal rats (n = 9) and following a right middle cerebral artery occlusion (MCAo, n = 9). Whole-body nuclear imaging, isolated organ counting (at 2 and 20 h after injection) and histology were performed. A higher activity was observed in the right damaged hemisphere of the MCAo group [6.5 +/- 0.9 x 10(-3) % of injected dose (ID)/g] than in the control group (3.6 +/- 1.2 x 10(-3) %ID/g), 20 h after injection. In MCAo rats, right hemisphere activity was higher than that observed in the contralateral hemisphere at 2 h after injection (11.6 +/- 2.8 vs. 9.8 +/- 1.7 x 10(-3) %ID/g). Following an initial hMSC lung accumulation, there was a decrease in pulmonary activity from 2 to 20 h after injection in both groups. The spleen was the only organ in which activity increased between 2 and 20 h. The presence of hMSC was documented in the spleen, liver, lung, and brain following histology. IV-injected hMSC are transiently trapped in the lungs, can be sequestered in the spleen, and are predominantly eliminated by kidneys. After 20 h, more hMSC are found in the ischemic lesion than into the undamaged cerebral tissue. IV delivery of hMSC could be the initial route for a clinical trial of tolerance.

Mesenchymal Stem Cell Therapy for Nonmusculoskeletal Diseases: Emerging Applications

Mesenchymal stem cells are stem/progenitor cells originated from the mesoderm and can different into multiple cell types of the musculoskeletal system. The vast differentiation potential and the relative ease for culture expansion have established mesenchymal stem cells as the building blocks in cell therapy and tissue engineering applications for a variety of musculoskeletal diseases, including repair of fractures and bone defects, cartilage regeneration, treatment of osteonecrosis of the femoral head, and correction of genetic diseases such as osteogenesis imperfect. However, research in the past decade has revealed differentiation potentials of mesenchymal stem cells beyond lineages of the mesoderm, suggesting broader applications than originally perceived. In this article, we review the recent developments in mesenchymal stem cell research with respect to their emerging properties and applications in nonmusculoskeletal diseases.

The (in) auspicious role of mesenchymal stromal cells in cancer: be it friend or foe

Recent progress in the research of mesenchymal stromal cells/multipotent stromal cells (MSC) has revealed numerous beneficial innate characteristics, suggesting potential value in an array of cellular therapies. MSC are easily isolated from bone marrow (BM), fat and other tissues, and are readily propagated in vitro. Transplanted/injected MSC have been shown to migrate to a variety of organs and tissues; however, sites of inflammation and pathology elicit enhanced MSC homing for tissue remodeling and repair. Tumors utilize many of the same inflammatory mediators uncovered in wound healing and likewise provide a site for preferential MSC homing. Although incorporation into the tumor microenvironment is apparent, the role of recruited MSC in the tumor microenvironment remains unclear. Some published studies have shown enhancement of tumor growth and development, perhaps through immunomodulatory and pro-angiogenic properties, while others have shown no apparent effect or have demonstrated inhibition of tumor growth and extended survival. This controversy remains at the forefront as clinical applications of MSC commence in anti-tumor therapies as well as as adjuncts to stem cell transplantation and in ameliorating graft-versus-host disease. Careful analysis of past studies and thoughtful design of future experiments will help to resolve the discrepancies in the field and lead to clinical utility of MSC in disease treatment. This review highlights the current theories of the role of MSC in tumors and explores current controversies.

Soluble mediators from mesenchymal stem cells suppress T cell proliferation by inducing IL-10

Mesenchymal stem cells (MSCs) can inhibit T cell proliferation; however, the underlying mechanisms are not clear. In this study, we investigated the mechanisms of the immunoregulatory activity of MSCs on T cells. Irradiated MSCs co-cultured with either na?ve or pre-activated T cells in a mixed lymphocyte reaction (MLR) significantly suppressed T cell proliferation in a dose-dependent manner, irrespective of allogeneic disparity between responders and MSCs. Transwell assays revealed that the suppressive effect was primarily mediated by soluble factors that induced apoptosis. Splenocytes stimulated with alloantigen in the presence of the MSC culture supernatant (CS) produced a significant amount of IL-10, which was attributed to an increase in the number of IL-10 secreting cells, confirmed by an ELISPOT assay. The blockade of IL-10 and IL-10 receptor interaction by anti-IL-10 or anti-IL-10-receptor antibodies abrogated the suppressive capacity of MSC CS, indicating that IL-10 plays a major role in the suppression of T cell proliferation. The addition of 1-methyl-DL-tryptophan (1-MT), an indoleamine 2,3-dioxygenase (IDO) inhibitor, also restored the proliferative capacity of T cells. In conclusion, we demonstrated that soluble mediators from culture supernatant of MSCs could suppress the proliferation of both naive and pre-activated T cells in which IL-10 and IDO play important roles.

Human umbilical cord blood-derived stromal cells suppress xenogeneic immune cell response in vitro

AIM

To explore immunological properties of human umbilical cord blood-derived stromal cells (hUCBDSC) and their effect on xenogeneic immune cells in vitro.

METHODS

Immunological phenotype of freshly isolated and cryopreserved hUCBDSCs was evaluated by flow cytometry. Xenogeneic splenic T-cells were stimulated by phytohemaglutinin A (PHA) or dendritic cells in the absence or presence of hUCBDSCs. T-cell proliferation was measured by cell counting kit-8 after 7-day incubation. The proportion of apoptotic cells and CD4+CD25+Foxp3+ regulatory T-cells (Tregs) was determined in T-cells activated by PHA in the absence or presence of hUCBDSCs by flow cytometry. Phenotype of dendritic cells, cultured alone or with hUCBDSCs, was analyzed by flow cytometry.

RESULTS

Levels of immune molecule expression on freshly isolated hUCBDSCs were as follows: human leukocyte antigen-I (HLA-I) (84.1+/-2.9%), HLA-II (1.6+/-0.3%), CD80 (0.8+/-0.1%), CD86 (0.8+/-0.1%), CD40 (0.6+/-0.1%), and CD40L (0.5+/-0.1%), which was not influenced by cryopreservation. T-cell proliferation in the presence of hUCBDSCs was significantly lower than that of positive control. The coculture led to a 10-fold increase (from 1.2+/-0.3% to 12.1+/-1.4%, P<0.001) in the proportion of CD4+CD25+Foxp3+ regulatory T-cells (Tregs) and a reversion of mature dendritic cells, as indicated by the down-regulation of major histocompatibility complex (MHC)-II molecule (49.3% vs 25.9%, P=0.001), CD80 (47.2% vs 23.3%, P=0.001), and CD86 (40.6% vs 25.1%, P=0.002). When subjected to annexin V binding and propidium iodide uptake assay, the hUCBDSCs did not show the ability to induce apoptosis of xenogeneic T-cells.

CONCLUSION

These results demonstrate low immunogenicity and immunomodulation effect of the hUCBDSCs. Reversion of mature dendritic cells and increase in Treg proportion, but not cell apoptosis, can possibly contribute to the suppression of xenogeneic T-cell proliferation by the hUCBDSCs.

Mesenchymal stem cells in the induction of transplantation tolerance

Mesenchymal stem cells directly suppress ongoing immune responses. Through production of toleragenic cytokines, inhibition of lymphocyte proliferation, delivery of reparative and protective signals after reperfusion injury, and facilitation of hematopoietic chimerism, these cells demonstrate a wide-ranging potential for the development of multifaceted toleragenic strategies after transplantation.

Mesenchymal stem cells for therapeutic purposes

Mesenchymal stem cells (MSC) are multipotent adult stem cells harboring a wide range of differentiations and non-human leukocyte antigen-restricted immunosuppressive properties that lead to an increasing use of MSC in immunomodulation and in regenerative medicine. To produce MSC, definitive standards are still lacking. Whatever the starting material used (e.g., bone marrow, adipose tissue, or cord blood), numerous parameters including cell plating density, number of passages, and culture medium, play a major role in the culture process and have to be determined. To date, the different production processes have been effective, and based on phenotypic analysis and differentiation potential, a first set of simple controls have been defined. However, controls of the final product should provide precise data on efficacy and safety. The next challenge will be to develop production processes that reach good manufacturing practices goals and to define more accurate control methods of cultivated MSC.

Mesenchymal stem cells protect NOD mice from diabetes by inducing regulatory T cells

AIMS/HYPOTHESIS

Displaying immunomodulatory capacities, mesenchymal stem cells (MSCs) are considered as beneficial agents for autoimmune diseases. The aim of this study was to examine the ability of MSCs to prevent autoimmune diabetes in the NOD mouse model.

METHODS

Prevention of spontaneous insulitis or of diabetes was evaluated after a single i.v. injection of MSCs in 4-week-old female NOD mice, or following the co-injection of MSCs and diabetogenic T cells in irradiated male NOD recipients, respectively. The frequency of CD4(+)FOXP3(+) cells and Foxp3 mRNA levels in the spleen of male NOD recipients were also quantified. In vivo cell homing was assessed by monitoring 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE)-labelled T cells or MSCs. In vitro, cell proliferation and cytokine production were assessed by adding graded doses of irradiated MSCs to insulin B9-23 peptide-specific T cell lines in the presence of irradiated splenocytes pulsed with the peptide.

RESULTS

MSCs reduced the capacity of diabetogenic T cells to infiltrate pancreatic islets and to transfer diabetes. This protective effect was not associated with the modification of diabetogenic T cell homing, but correlated with a preferential migration of MSCs to pancreatic lymph nodes. While injection of diabetogenic T cells resulted in a decrease in levels of FOXP3(+) regulatory T cells, this decrease was inhibited by MSC co-transfer. Moreover, MSCs were able to suppress both allogeneic and insulin-specific proliferative responses in vitro. This suppressive effect was associated with the induction of IL10-secreting FOXP3(+) T cells.

CONCLUSIONS/INTERPRETATION

MSCs prevent autoimmune beta cell destruction and subsequent diabetes by inducing regulatory T cells. MSCs may thus offer a novel cell-based approach for the prevention of autoimmune diabetes and for islet cell transplantation.

Immune regulatory neural stem/precursor cells protect from central nervous system autoimmunity by restraining dendritic cell function

Background

The systemic injection of neural stem/precursor cells (NPCs) provides remarkable amelioration of the clinico-pathological features of experimental autoimmune encephalomyelitis (EAE). This is dependent on the capacity of transplanted NPCs to engage concurrent mechanisms of action within specific microenvironments in vivo. Among a wide range of therapeutic actions alternative to cell replacement, neuroprotective and immune modulatory capacities of transplanted NPCs have been described. However, lacking is a detailed understanding of the mechanisms by which NPCs exert their therapeutic plasticity. This study was designed to identify the first candidate that exemplifies and sustains the immune modulatory capacity of transplanted NPCs.

Methodology/Principal Findings

To achieve the exclusive targeting of the peripheral immune system, SJL mice with PLP-induced EAE were injected subcutaneously with NPCs and the treatment commenced prior to disease onset. NPC-injected EAE mice showed significant clinical improvement, as compared to controls. Exogenous NPCs lacking the expression of major neural antigens were reliably (and for long-term) found at the level of draining lymph nodes, while establishing sophisticated anatomical interactions with lymph node cells. Importantly, injected NPCs were never found in organs other than lymph nodes, including the brain and the spinal cord. Draining lymph nodes from transplanted mice showed focal up-regulation of major developmental stem cell regulators, such as BMP-4, Noggin and Sonic hedgehog. In lymph nodes, injected NPCs hampered the activation of myeloid dendritic cells (DCs) and steadily restrained the expansion of antigen-specific encephalitogenic T cells. Both ex vivo and in vitro experiments identified a novel highly NPC-specific–BMP-4-dependent–mechanism hindering the DC maturation.

Conclusion/Significance

The study described herein, identifies the first member of the TGF β/BMP family of stem cell regulators as a novel tolerogenic factor released by NPCs. Full exploitation of this pathway as an efficient tool for vaccination therapy in autoimmune inflammatory conditions is underway.

Cytotoxicity mediated by the Fas ligand (FasL)-activated apoptotic pathway in stem cells

Whereas it is now clear that human bone marrow stromal cells (BMSCs) can be immunosuppressive and escape cytotoxic lymphocytes (CTLs) in vitro and in vivo, the mechanisms of this phenomenon remain controversial. Here, we test the hypothesis that BMSCs suppress immune responses by Fas-mediated apoptosis of activated lymphocytes and find both Fas and FasL expression by primary BMSCs. Jurkat cells or activated lymphocytes were each killed by BMSCs after 72 h of co-incubation. In comparison, the cytotoxic effect of BMSCs on non-activated lymphocytes and on caspase-8(-/-) Jurkat cells was extremely low. Fas/Fc fusion protein strongly inhibited BMSC-induced lymphocyte apoptosis. Although we detected a high level of Fas expression in BMSCs, stimulation of Fas with anti-Fas antibody did not result in the expected BMSC apoptosis, regardless of concentration, suggesting a disruption of the Fas activation pathway. Thus BMSCs may have an endogenous mechanism to evade Fas-mediated apoptosis. Cumulatively, these data provide a parallel between adult stem/progenitor cells and cancer cells, consistent with the idea that stem/progenitor cells can use FasL to prevent lymphocyte attack by inducing lymphocyte apoptosis during the regeneration of injured tissues.

Cellular therapy of systemic lupus erythematosus

Immunoablation with autologous hematopoietic stem cell rescue has been used in over 1,300 autoimmune disease patients, around 150 with SLE. Some patients have experienced durable remissions with loss of autoantibodies, whereas others either did not respond or died as a result of the treatment. Prospective randomised trials are required and are being planned to establish the place for this potentailly curative strategy. Mesenchymal stem cells are in an exploratory phase for the treatment of acute autoimmune disease including SLE. The principle is that they home to inflammed tissue and exert an antiinflammatory paracrine effect.

Mouse pancreatic islets are resistant to indoleamine 2,3 dioxygenase-induced general control nonderepressible-2 kinase stress pathway and maintain normal viability and function

Islet transplantation is a promising treatment for diabetes. However, it faces several challenges including requirement of systemic immunosuppression. Indoleamine 2,3-dioxygenase (IDO), a tryptophan degrading enzyme, is a potent immunomodulatory factor. Local expression of IDO in bystander fibroblasts suppresses islet allogeneic immune response in vitro. The aim of the present study was to investigate the impact of IDO on viability and function of mouse islets embedded within IDO-expressing fibroblast-populated collagen scaffold. Mouse islets were embedded within collagen matrix populated with IDO adenovector-transduced or control fibroblasts. Proliferation, insulin content, glucose responsiveness, and activation of general control nonderepressible-2 kinase stress-responsive pathway were then measured in IDO-exposed islets. In vivo viabilities of composite islet grafts were also tested in a syngeneic diabetic animal model. No reduction in islet cells proliferation was detected in both IDO-expressing and control composites compared to the baseline rates. Islet functional studies showed normal insulin content and secretion in both preparations. In contrast to lymphocytes, general control nonderepressible-2 kinase pathway was not activated in islets cocultured with IDO-expressing fibroblasts. When transplanted to diabetic mice, syngeneic IDO-expressing composite islet grafts were functional up to 100 days tested. These findings collectively confirm normal viability and functionality of islets cocultured with IDO-expressing cells and indicate the feasibility of development of a functional nonrejectable islet graft.

Clinical scale expanded adult pluripotent stem cells prevent graft-versus-host disease

Adherent bone marrow adult stem cells have been used in the treatment of GVHD. In this study, we investigate the capacity of a newly characterized population of stem cells, the Multipotent Adult Progenitor Cells (MAPC), to modulate acute GVHD. These cells were derived from bone marrow cells and grown extensively without evidence for replicative senescence or loss of differentiating capacity. MAPC significantly decreased mortality of acute GVHD. Moreover, they were non immunogenic and they were not sensitive to NK-lysis. When these cells were added to a mixed lymphocyte reaction (MLR), a dose-dependent suppression of T cell proliferation was observed that was non-MHC restricted, was reversible upon removal of MAPC from culture and was mediated by soluble factors. These data show that in vitro expanded adult stem cells can efficiently control an allo-reactive response associated with acute GVHD, that they are immuno-privileged and present strong immunosuppressive properties.

Soluble factors-mediated immunomodulatory effects of canine adipose tissue-derived mesenchymal stem cells

Adipose tissue-derived mesenchymal stem cells (AD-MSCs), which can differentiate into several lineages, have immunomodulatory properties similar to those of bone marrow-derived MSCs. However, the specific mechanism by which the immunomodulatory effect of MSCs occurs is not clear. In this study, we isolated canine AD-MSCs (cAD-MSCs) and induced their development into adipocyte, osteocyte, and neuron-like cells. We then investigated their phenotype and cytokine expression to determine whether they were able to exert an immunomodulatory effect and what the underlying mechanisms of this effect were. cAD-MSCs expressed CD44, CD90, and MHC class I and were also partially positive for the expression of CD34; however, they did not express CD14 and CD45. In addition, they expressed the mRNA of transforming growth factor beta (TGF-beta), IL-6, IL-8, CCL2, CCL5, vascular endothelial growth factor, hepatocyte growth factor (HGF), tissue inhibitor metalloproteinase-1/2, and cyclooxygenase-2 but not that of IL-10. Further, leukocyte proliferation induced by mitogens was suppressed when they were cocultured with irradiated cAD-MSCs, as well as with culture supernatants of cAD-MSCs alone. Moreover, TNF-alpha production significantly decreased, whereas TGF-beta, IL-6, and interferon-gamma production significantly increased in cAD-MSCs that were cocultured with leukocytes. Finally, immonomodulatory factors of MSCs, such as TGF-beta, HGF, prostaglandin E2 (PGE2), and indoleamine 2, 3 dioxygenase (IDO), increased significantly in cAD-MSCs that were cocultured with leukocytes; however, the production of PGE2 and IDO showed different kinetics, and leukocyte proliferation was effectively restored by PGE2 and IDO inhibitors. Taken together, these results indicate that the immunomodulatory effects of cAD-MSCs are associated with soluble factors (TGF-beta, HGF, PGE2, and IDO). Therefore, it is suggested that cAD-MSCs have a potential therapeutic use in the treatment of immune-mediated disease.

MHC expression kinetics and immunogenicity of mesenchymal stromal cells after short-term IFN-gamma challenge

OBJECTIVE

Under the influence of interferon-gamma (IFN-gamma), mesenchymal stromal cells (MSCs) are conditional antigen-presenting cells, which have immunosuppressive potential. Apart from IFN-gamma upregulation of major histocompatibility complexes class I and II (MHC-I and MHC-II) expression, the underlying kinetics and mechanisms have not been described previously. This information is helpful to delineate how human MSCs can be modulated by IFN-gamma in different clinical scenarios.

MATERIALS AND METHODS

Here, we demonstrated that IFN-gamma-treated MSCs underwent classical signal transduction pathway via phosphorylation of signal transducers and activators of transcription-1, activation of interferon regulatory factor-1, and class II transactivator comparable to that of primary human blood macrophages.

RESULTS

IFN-gamma markedly induced expression of MHC-I instantly, while its effects on MHC-II were less dramatic and delayed up to 4 days. This is due to a slower intracellular transport of the MHC-II antigen to the membrane surface. More important is that MSCs showed a reduction in their proliferation by 50% without evidence of cell death after prolonged IFN-gamma treatment for 8 days. High-dose IFN-gamma-treated MSCs (500 U/mL) could initiate T-cell activation as indicated by expression of CD25 and proliferation of allogeneic T cells.

CONCLUSIONS

The summative IFN-gamma effects will adversely affect the immunoprivilege status and lifespan of MSCs.

Immunosuppression by mesenchymal stromal cells: from culture to clinic

Extensive in vitro studies have shown that multipotent mesenchymal stromal cells (MSC) can exert profound immunosuppressive effects via modulation of both cellular and innate immune pathways. Their ability to be readily isolated from a number of tissues and expanded ex vivo makes them attractive candidates for systemic immunosuppressive therapy. In this article, we will review recent experimental data on the mechanisms by which MSC inhibit the alloproliferative response and the clinical relevance for their potential use in hematopoietic stem cell transplantation, solid organ transplantation, and treatment of autoimmune diseases. While in vitro data consistently demonstrate the immunosuppressive capability of MSC, current studies in animals and humans suggest that MSC are less effective in producing systemic immunosuppression. Further mechanistic studies and randomized controlled trials using standardized cell populations are needed to define the optimal conditions for the use of MSC as immunotherapy.

Multipotent mesenchymal stromal cells in articular diseases

Although cartilage defects are common features of osteoarthritis and rheumatoid arthritis, current treatments can rarely restore the full function of native cartilage. Recent studies have provided new perspectives for cartilage engineering using multipotent mesenchymal stromal cells (MSC). Moreover, MSC have been used as immunosuppressant agents in autoimmune diseases and have tested successfully in animal models of arthritis. However, the sequential events occurring during chondrogenesis must be fully understood before we can reproduce the complex molecular events that lead to MSC differentiation and long-term maintenance of cartilage characteristics in the context of chronic joint inflammation. This chapter focuses on the potential of MSC to repair cartilage, with an emphasis on the factors that are known to be required in inducing chondrogenesis and on their immunosuppressive potential.

Multipotent Mesenchymal Stromal Cells for Autoimmune Diseases

SUMMARY: Multipotent mesenchymal stromal cells (MSC) are under consideration for the treatment of autoimmune disease (AD) based on their in vitro antiproliferative properties, efficacy in animal models, apparent low acute toxicity, and the early positive anecdotal outcomes in human acute graft versus host disease. Phase I/II clinical trials are under way in multiple sclerosis and Crohn's disease, and are being planned in systemic lupus erythematosus, systemic sclerosis, systemic vasculitis, and other AD. Open issues include: patient selection, disease stage and activity, MSC source and expansion, and long-term safety. Multidisciplinary groups including EULAR are collaborating to ensure maximal use of available resources to establish the place, if any, of MSC in the treatment of AD.

Systemic administration of multipotent mesenchymal stromal cells reverts hyperglycemia and prevents nephropathy in type 1 diabetic mice

Multipotent mesenchymal stromal cells (MSCs), often labeled mesenchymal stem cells, contribute to tissue regeneration in injured bone and cartilage, as well as in the infarcted heart, brain, and kidney. We hypothesize that MSCs might also contribute to pancreas and kidney regeneration in diabetic individuals. Therefore, in streptozotocin (STZ)-induced type 1 diabetes C57BL/6 mice, we tested whether a single intravenous dose of MSCs led to recovery of pancreatic and renal function and structure. When hyperglycemia, glycosuria, massive beta-pancreatic islets destruction, and mild albuminuria were evident (but still without renal histopathologic changes), mice were randomly separated in 2 groups: 1 received 0.5 x 10(6) MSCs that have been ex vivo expanded (and characterized according to their mesenchymal differentiation potential), and the other group received the vehicle. Within a week, only MSC-treated diabetic mice exhibited significant reduction in their blood glucose levels, reaching nearly euglycemic values a month later. Reversion of hyperglycemia and glycosuria remained for 2 months at least. An increase in morphologically normal beta-pancreatic islets was observed only in MSC-treated diabetic mice. Furthermore, in those animals albuminuria was reduced and glomeruli were histologically normal. On the other side, untreated diabetic mice presented glomerular hyalinosis and mesangial expansion. Thus, MSC administration resulted in beta-pancreatic islets regeneration and prevented renal damage in diabetic animals. Our preclinical results suggest bone marrow-derived MSC transplantation as a cell therapy strategy to treat type 1 diabetes and prevent diabetic nephropathy, its main complication.

Bone marrow-derived mesenchymal stem cells for treatment of heart failure: is it all paracrine actions and immunomodulation?

Despite significant advances in medical and surgical management of heart failure, mostly of ischaemic origin, the mortality and morbidity associated with it continue to be high. Pluripotent stem cells are being evaluated for treatment of heart failure. Bone marrow-derived mesenchymal stem cells (MSCs) have been extensively studied. Emerging evidence suggests that locally delivered MSCs can lead to an improvement in ventricular function, but the cellular and molecular mechanisms involved remain unclear. Myocardial regeneration, as proposed by many researchers as the underlying mechanism, has failed to convince the scientific community. Recently some authors have ascribed improvement in ventricular function to paracrine actions of MSCs.A lot has been written about the host immune response triggered by embryonic stem cells and the consequent need for immunosuppression. Not enough work has been done on immune interactions involving allogeneic bone marrow cells. Full potential of stem cell therapy can be realised only when we are able to use allogeneic cells. The potential use of MSCs in cellular therapy has recently prompted researchers to look into their interaction with the host immune response. MSCs have immunomodulatory properties. They cause suppression of proliferation of alloreactive T cells in a dose-dependent manner.Tissue injury causes inflammation and release of several chemokines, cytokines and growth factors. They can cause recruitment of bone marrow-derived MSCs to the injured area. We review the literature on paracrine actions and immune interactions of allogeneic MSCs.

Mesenchymal stem cells: biology and clinical potential in type 1 diabetes therapy

Mesenchymal stem cells (MSCs) can be derived from adult bone marrow, fat and several foetal tissues. In vitro, MSCs have the capacity to differentiate into multiple mesodermal and non-mesodermal cell lineages. Besides, MSCs possess immunosuppressive effects by modulating the immune function of the major cell populations involved in alloantigen recognition and elimination. The intriguing biology of MSCs makes them strong candidates for cell-based therapy against various human diseases. Type 1 diabetes is caused by a cell-mediated autoimmune destruction of pancreatic β-cells. While insulin replacement remains the cornerstone treatment for type 1 diabetes, the transplantation of pancreatic islets of Langerhans provides a cure for this disorder. And yet, islet transplantation is limited by the lack of donor pancreas. Generation of insulin-producing cells (IPCs) from MSCs represents an attractive alternative. On the one hand, MSCs from pancreas, bone marrow, adipose tissue, umbilical cord blood and cord tissue have the potential to differentiate into IPCs by genetic modification and/or defined culture conditions In vitro. On the other hand, MSCs are able to serve as a cellular vehicle for the expression of human insulin gene. Moreover, protein transduction technology could offer a novel approach for generating IPCs from stem cells including MSCs. In this review, we first summarize the current knowledge on the biological characterization of MSCs. Next, we consider MSCs as surrogate β-cell source for islet transplantation, and present some basic requirements for these replacement cells. Finally, MSCs-mediated therapeutic neovascularization in type 1 diabetes is discussed.