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1.  Type 1 regulatory T cells specific for collagen type II as an efficient cell-based therapy in arthritis 
Arthritis Research & Therapy  2014;16(3):R115.
Introduction
Regulatory T (Treg) cells play a crucial role in preventing autoimmune diseases and are an ideal target for the development of therapies designed to suppress inflammation in an antigen-specific manner. Type 1 regulatory T (Tr1) cells are defined by their capacity to produce high levels of interleukin 10 (IL-10), which contributes to their ability to suppress pathological immune responses in several settings. The aim of this study was to evaluate the therapeutic potential of collagen type II–specific Tr1 (Col-Treg) cells in two models of rheumatoid arthritis (RA) in mice.
Methods
Col-Treg clones were isolated and expanded from collagen-specific TCR transgenic mice. Their cytokine secretion profile and phenotype characterization were studied. The therapeutic potential of Col-Treg cells was evaluated after adoptive transfer in collagen-antibody– and collagen-induced arthritis models. The in vivo suppressive mechanism of Col-Treg clones on effector T-cell proliferation was also investigated.
Results
Col-Treg clones are characterized by their specific cytokine profile (IL-10highIL-4negIFN-γint) and mediate contact-independent immune suppression. They also share with natural Tregs high expression of GITR, CD39 and granzyme B. A single infusion of Col-Treg cells reduced the incidence and clinical symptoms of arthritis in both preventive and curative settings, with a significant impact on collagen type II antibodies. Importantly, injection of antigen-specific Tr1 cells decreased the proliferation of antigen-specific effector T cells in vivo significantly.
Conclusions
Our results demonstrate the therapeutic potential of Col-Treg cells in two models of RA, providing evidence that Col-Treg could be an efficient cell-based therapy for RA patients whose disease is refractory to current treatments.
doi:10.1186/ar4567
PMCID: PMC4075412  PMID: 24886976
2.  Circulating miRNA-125b Is a Potential Biomarker Predicting Response to Rituximab in Rheumatoid Arthritis 
Mediators of Inflammation  2014;2014:342524.
Although biologic therapies have changed the course of rheumatoid arthritis (RA), today's major challenge remains to identify biomarkers to target treatments to selected patient groups. Circulating micro(mi)RNAs represent a novel class of molecular biomarkers whose expression is altered in RA. Our study aimed at quantifying miR-125b in blood and serum samples from RA patients, comparing healthy controls and patients with other forms of rheumatic diseases and arthritis, and evaluating its predictive value as biomarker for response to rituximab. Detectable levels of miR-125b were measured in total blood and serum samples and were significantly elevated in RA patients compared to osteoarthritic and healthy donors. The increase was however also found in patients with other forms of chronic inflammatory arthritis. Importantly, high serum levels of miR-125b at disease flare were associated with good clinical response to treatment with rituximab three months later (P = 0.002). This predictive value was not limited to RA as it was also found in patients with B lymphomas. Our results identify circulating miR-125b as a novel miRNA over expressed in RA and suggest that serum level of miR-125b is potential predictive biomarker of response to rituximab treatment.
doi:10.1155/2014/342524
PMCID: PMC3980876  PMID: 24778468
3.  p16INK4a and its regulator miR-24 link senescence and chondrocyte terminal differentiation-associated matrix remodeling in osteoarthritis 
Introduction
Recent evidence suggests that tissue accumulation of senescent p16INK4a-positive cells during the life span would be deleterious for tissue functions and could be the consequence of inherent age-associated disorders. Osteoarthritis (OA) is characterized by the accumulation of chondrocytes expressing p16INK4a and markers of the senescence-associated secretory phenotype (SASP), including the matrix remodeling metalloproteases MMP1/MMP13 and pro-inflammatory cytokines interleukin-8 (IL-8) and IL-6. Here, we evaluated the role of p16INK4a in the OA-induced SASP and its regulation by microRNAs (miRs).
Methods
We used IL-1-beta-treated primary OA chondrocytes cultured in three-dimensional setting or mesenchymal stem cells differentiated into chondrocyte to follow p16INK4a expression. By transient transfection experiments and the use of knockout mice, we validate p16INK4a function in chondrocytes and its regulation by one miR identified by means of a genome-wide miR-array analysis.
Results
p16INK4a is induced upon IL-1-beta treatment and also during in vitro chondrogenesis. In the mouse model, Ink4a locus favors in vivo the proportion of terminally differentiated chondrocytes. When overexpressed in chondrocytes, p16INK4a is sufficient to induce the production of the two matrix remodeling enzymes, MMP1 and MMP13, thus linking senescence with OA pathogenesis and bone development. We identified miR-24 as a negative regulator of p16INK4a. Accordingly, p16INK4a expression increased while miR-24 level was repressed upon IL-1-beta addition, in OA cartilage and during in vitro terminal chondrogenesis.
Conclusions
We disclosed herein a new role of the senescence marker p16INK4a and its regulation by miR-24 during OA and terminal chondrogenesis.
doi:10.1186/ar4494
PMCID: PMC4060445  PMID: 24572376
4.  Promyelocytic leukemia zinc-finger induction signs mesenchymal stem cell commitment: identification of a key marker for stemness maintenance? 
Introduction
Mesenchymal stem cells (MSCs) are an attractive cell source for cartilage and bone tissue engineering given their ability to differentiate into chondrocytes and osteoblasts. However, the common origin of these two specialized cell types raised the question about the identification of regulatory pathways determining the differentiation fate of MSCs into chondrocyte or osteoblast.
Methods
Chondrogenesis, osteoblastogenesis, and adipogenesis of human and mouse MSC were induced by using specific inductive culture conditions. Expression of promyelocytic leukemia zinc-finger (PLZF) or differentiation markers in MSCs was determined by RT-qPCR. PLZF-expressing MSC were implanted in a mouse osteochondral defect model and the neotissue was analyzed by routine histology and microcomputed tomography.
Results
We found out that PLZF is not expressed in MSCs and its expression at early stages of MSC differentiation is the mark of their commitment toward the three main lineages. PLZF acts as an upstream regulator of both Sox9 and Runx2, and its overexpression in MSC enhances chondrogenesis and osteogenesis while it inhibits adipogenesis. In vivo, implantation of PLZF-expressing MSC in mice with full-thickness osteochondral defects resulted in the formation of a reparative tissue resembling cartilage and bone.
Conclusions
Our findings demonstrate that absence of PLZF is required for stemness maintenance and its expression is an early event at the onset of MSC commitment during the differentiation processes of the three main lineages.
doi:10.1186/scrt416
PMCID: PMC4055047  PMID: 24564963
5.  Tissue-specific and SRSF1-dependent splicing of fibronectin, a matrix protein that controls host cell invasion 
Molecular Biology of the Cell  2013;24(20):3164-3176.
Matching sets of human primary fibroblasts cocultured with placenta explants are used to compare tissue capacities to support trophoblast invasion. Substituting endometrium with dermis dramatically reduces EVCT interstitial invasion, a phenomenon related to the ECM fibronectin content, FN alternative splicing, and expression of the SR protein SRSF1.
Cell invasion targets specific tissues in physiological placental implantation and pathological metastasis, which raises questions about how this process is controlled. We compare dermis and endometrium capacities to support trophoblast invasion, using matching sets of human primary fibroblasts in a coculture assay with human placental explants. Substituting endometrium, the natural trophoblast target, with dermis dramatically reduces trophoblast interstitial invasion. Our data reveal that endometrium expresses a higher rate of the fibronectin (FN) extra type III domain A+ (EDA+) splicing isoform, which displays stronger matrix incorporation capacity. We demonstrate that the high FN content of the endometrium matrix, and not specifically the EDA domain, supports trophoblast invasion by showing that forced incorporation of plasma FN (EDA–) promotes efficient trophoblast invasion. We further show that the serine/arginine-rich protein serine/arginine-rich splicing factor 1 (SRSF1) is more highly expressed in endometrium and, using RNA interference, that it is involved in the higher EDA exon inclusion rate in endometrium. Our data therefore show a mechanism by which tissues can be distinguished, for their capacity to support invasion, by their different rates of EDA inclusion, linked to their SRSF1 protein levels. In the broader context of cancer pathology, the results suggest that SRSF1 might play a central role not only in the tumor cells, but also in the surrounding stroma.
doi:10.1091/mbc.E13-03-0142
PMCID: PMC3806663  PMID: 23966470
6.  Mesenchymal stem cells generate a CD4+CD25+Foxp3+ regulatory T cell population during the differentiation process of Th1 and Th17 cells 
Introduction
Mesenchymal stem cells (MSCs) are adult, multipotent, stem cells with immunomodulatory properties. The mechanisms involved in the capacity of MSCs to inhibit the proliferation of proinflammatory T lymphocytes, which appear responsible for causing autoimmune disease, have yet to be fully elucidated. One of the underlying mechanisms studied recently is the ability of MSCs to generate T regulatory (Treg) cells in vitro and in vivo from activated peripheral blood mononuclear cells (PBMC), T-CD4+ and also T-CD8+ cells. In the present work we investigated the capacity of MSCs to generate Treg cells using T-CD4+ cells induced to differentiate toward the proinflammatory Th1 and Th17 lineages.
Methods
MSCs were obtained from mouse bone marrow and characterized according to their surface antigen expression and their multilineage differentiation potential. CD4+ T cells isolated from mouse spleens were induced to differentiate into Th1 or Th17 cells and co-cultured with MSCs added at day 0, 2 or 4 of the differentiation processes. After six days, CD25, Foxp3, IL-17 and IFN-γ expression was assessed by flow cytometry and helios and neuropilin 1 mRNA levels were assessed by RT-qPCR. For the functional assays, the ‘conditioned’ subpopulation generated in the presence of MSCs was cultured with concanavalin A-activated CD4+ T cells labeled with carboxyfluorescein succinimidyl ester. Finally, we used the encephalomyelitis autoimmune diseases (EAE) mouse model, in which mice were injected with MSCs at day 18 and 30 after immunization. At day 50, the mice were euthanized and draining lymph nodes were extracted for Th1, Th17 and Treg detection by flow cytometry.
Results
MSCs were able to suppress the proliferation, activation and differentiation of CD4+ T cells induced to differentiate into Th1 and Th17 cells. This substantial suppressive effect was associated with an increase of the percentage of functional induced CD4+CD25+Foxp3+ regulatory T cells and IL-10 secretion. However, using mature Th1 or Th17 cells our results demonstrated that while MSCs suppress the proliferation and phenotype of mature Th1 and Th17 cells they did not generate Treg cells. Finally, we showed that the beneficial effect observed following MSC injection in an EAE mouse model was associated with the suppression of Th17 cells and an increase in the percentage of CD4+CD25+Foxp3+ T lymphocytes when administrated at early stages of the disease.
Conclusions
This study demonstrated that MSCs contribute to the generation of an immunosuppressive environment via the inhibition of proinflammatory T cells and the induction of T cells with a regulatory phenotype. Together, these results might have important clinical implications for inflammatory and autoimmune diseases.
doi:10.1186/scrt216
PMCID: PMC3706898  PMID: 23734780
Mesenchymal stem cells; Th1; Th17; Immunosuppression; CD4+CD25+Foxp3+ T cells
7.  Duplication 8q12: confirmation of a novel recognizable phenotype with duane retraction syndrome and developmental delay 
Duane retraction syndrome (DRS) is a rare congenital strabismus condition with genetic heterogeneity. DRS associated with intellectual disability or developmental delay is observed in several genetic diseases: syndromes such as Goldenhar or Wildervanck syndrome and chromosomal anomalies such as 12q12 deletion. We report on the case of a patient with DRS, developmental delay and particular facial features (horizontal and flared eyebrows, long and smooth philtrum, thin upper lip, full lower lip and full cheeks). We identified a duplication of the long arm of chromosome 8 (8q12) with SNP-array. This is the third case of a patient with common clinical features and 8q12 duplication described in the literature. The minimal critical region is 1.2 Mb and encompasses four genes: CA8, RAB2, RLBP1L1 and CHD7. To our knowledge, no information is available in the literature regarding pathological effects caused by to overexpression of these genes. However, loss of function of the CHD7 gene leads to CHARGE syndrome, suggesting a possible role of the overexpression of this gene in the phenotype observed in 8q12 duplication patients. We have observed that patients with 8q12 duplication share a common recognizable phenotype characterized by DRS, developmental delay and facial features. Such data combined to the literature strongly suggest that this entity may define a novel syndrome. We hypothesize that CHD7 duplication is responsible for a part of the features observed in 8q12.2 duplication.
doi:10.1038/ejhg.2011.243
PMCID: PMC3330221  PMID: 22258531
duane retraction syndrome; intellectual disability; 8q12 duplication; CHD7 gene; common facial features
8.  Sox9-Regulated miRNA-574-3p Inhibits Chondrogenic Differentiation of Mesenchymal Stem Cells 
PLoS ONE  2013;8(4):e62582.
The aim of this study was to identify new microRNAs (miRNAs) that are modulated during the differentiation of mesenchymal stem cells (MSCs) toward chondrocytes. Using large scale miRNA arrays, we compared the expression of miRNAs in MSCs (day 0) and at early time points (day 0.5 and 3) after chondrogenesis induction. Transfection of premiRNA or antagomiRNA was performed on MSCs before chondrogenesis induction and expression of miRNAs and chondrocyte markers was evaluated at different time points during differentiation by RT-qPCR. Among miRNAs that were modulated during chondrogenesis, we identified miR-574-3p as an early up-regulated miRNA. We found that miR-574-3p up-regulation is mediated via direct binding of Sox9 to its promoter region and demonstrated by reporter assay that retinoid X receptor (RXR)α is one gene specifically targeted by the miRNA. In vitro transfection of MSCs with premiR-574-3p resulted in the inhibition of chondrogenesis demonstrating its role during the commitment of MSCs towards chondrocytes. In vivo, however, both up- and down-regulation of miR-574-3p expression inhibited differentiation toward cartilage and bone in a model of heterotopic ossification. In conclusion, we demonstrated that Sox9-dependent up-regulation of miR-574-3p results in RXRα down-regulation. Manipulating miR-574-3p levels both in vitro and in vivo inhibited chondrogenesis suggesting that miR-574-3p might be required for chondrocyte lineage maintenance but also that of MSC multipotency.
doi:10.1371/journal.pone.0062582
PMCID: PMC3633883  PMID: 23626837
9.  Anti-neutrophil cytoplasmic antibodies in rheumatoid arthritis: two case reports and review of literature 
Background
Anti-neutrophil cytoplasmic antibodies are typically detected in anti-neutrophil cytoplasmic antibody associated vasculitis, but are also present in a number of chronic inflammatory non-vasculitic conditions like rheumatoid arthritis. Rare cases of granulomatosis with polyangiitis (formerly known as Wegener’s granulomatosis, a vasculitic disorder frequently associated with the presence of anti-neutrophil cytoplasmic antibodies) in patients with rheumatoid arthritis have been described in literature.
Case presentation
We report two middle-aged female patients with rheumatoid arthritis who developed anti-neutrophil cytoplasmic antibodies and symptoms reminiscent of granulomatosis with polyangiitis. Despite the lack of antibodies specific for proteinase 3 and the absence of a classical histology, we report a probable case of granulomatosis with polyangiitis in the first patient, and consider rheumatoid vasculitis in the second patient.
Conclusion
Taken together with previous reports, these cases highlight that anti-neutrophil cytoplasmic antibodies have to be evaluated very carefully in patients with rheumatoid arthritis. In this context, anti-neutrophil cytoplasmic antibodies detected by indirect immunofluorescence appear to have a low diagnostic value for granulomatosis with polyangiitis. Instead they may have prognostic value for assessing the course of rheumatoid arthritis.
doi:10.1186/1710-1492-8-19
PMCID: PMC3552688  PMID: 23253567
Granulomatosis with polyangiitis; Rheumatoid arthritis; ANCA associated vasculitis; Rheumatoid vasculitis
13.  Mesenchymal Stem Cells Repress Th17 Molecular Program through the PD-1 Pathway 
PLoS ONE  2012;7(9):e45272.
MSC display potent suppressive properties initially described a decade ago. More recently, MSC suppressive activities on T-cell effector pathways have been investigated. MSC modulate CD4 differentiation through different mechanisms depending on culture conditions and display disparate activities on T cells according to their differentiation status. A significant amount of evidence for MSC effects on Th17 cells revealed that MSC could be suppressive under diverse circumstances but also enhance Th17 cell activity under other conditions. In the present study, we investigated the suppressive effects of MSC on Th1 and Th17 subsets of T cells using T cells undergoing Th1 and Th17 polarization or mature Th1 and Th17 cells. MSC inhibited the proliferation of T cells during their differentiation toward Th1 cells and mature Th1 cells. This suppressive effect was maintained in a transwell cell culture insert demonstrating the major role played by soluble factors. Using the transwell cell separation barrier, we observed that MSC decrease the number of T cells undergoing Th17 differentiation whereas they did not affect IL-17 production by mature Th17, demonstrating the need for cell contact for suppressing Th17 cell function. Moreover, we reported that PD-L1 is highly expressed on MSC co-cultured with differentiating or polarized Th1 and Th17 cells. Using neutralizing antibodies specific for PD-L1 and PD-1 we showed that the mechanisms by which MSC mediate Th17 cell repolarization depend on PD-L1 expression on MSC. Taken together our results demonstrated a cell-to-cell contact depend mechanism in the selective immunosuppression of MSC on mature Th17 cells through up-regulation of PD-L1.
doi:10.1371/journal.pone.0045272
PMCID: PMC3444478  PMID: 23028899
15.  Mesenchymal stem cell-based therapies in regenerative medicine: applications in rheumatology 
Growing knowledge on the biology of mesenchymal stem cells (MSCs) has provided new insights into their potential clinical applications, particularly for rheumatologic disorders. Historically, their potential to differentiate into cells of the bone and cartilage lineages has led to a variety of experimental strategies to investigate whether MSCs can be used for tissue engineering approaches. Beyond this potential, MSCs also display immunosuppressive properties, which have prompted research on their capacity to suppress local inflammation and tissue damage in a variety of inflammatory autoimmune diseases and, in particular, in rheumatoid arthritis. Currently, an emerging field of research comes from the possibility that these cells, through their trophic/regenerative potential, may also influence the course of chronic degenerative disorders and prevent cartilage degradation in osteoarthritis. This review focuses on these advances, specifically on the biological properties of MSCs, including their immunoregulatory characteristics, differentiation capacity and trophic potential, as well as the relevance of MSC-based therapies for rheumatic diseases.
doi:10.1186/scrt55
PMCID: PMC3226285  PMID: 21457518
19.  Cartilage tissue engineering: towards a biomaterial-assisted mesenchymal stem cell therapy 
Injuries to articular cartilage are one of the most challenging issues of musculoskeletal medicine due to the poor intrinsic ability of this tissue for repair. Despite progress in orthopaedic surgery, the lack of efficient modalities of treatment for large chondral defects has prompted research on tissue engineering combining chondrogenic cells, scaffold materials and environmental factors. The aim of this review is to focus on the recent advances made in exploiting the potentials of cell therapy for cartilage engineering. These include: 1) defining the best cell candidates between chondrocytes or multipotent progenitor cells, such as multipotent mesenchymal stromal cells (MSC), in terms of readily available sources for isolation, expansion and repair potential; 2) engineering biocompatible and biodegradable natural or artificial matrix scaffolds as cell carriers, chondrogenic factors releasing factories and supports for defect filling, 3) identifying more specific growth factors and the appropriate scheme of application that will promote both chondrogenic differentiation and then maintain the differentiated phenotype overtime and 4) evaluating the optimal combinations that will answer to the functional demand placed upon cartilage tissue replacement in animal models and in clinics. Finally, some of the major obstacles generally encountered in cartilage engineering are discussed as well as future trends to overcome these limiting issues for clinical applications.
PMCID: PMC3218613  PMID: 19804369
Animals; Biocompatible Materials; therapeutic use; Cartilage; metabolism; pathology; Cartilage Diseases; pathology; therapy; Cell Differentiation; Chondrocytes; metabolism; pathology; transplantation; Guided Tissue Regeneration; Hematopoietic Stem Cell Mobilization; Humans; Intercellular Signaling Peptides and Proteins; metabolism; Mesenchymal Stem Cell Transplantation; Stem Cell Niche; Tissue Engineering; Tissue Scaffolds
20.  Human bone marrow mesenchymal stem cells: a systematic reappraisal via the genostem experience 
Stem Cell Reviews  2011;7(1):32-42.
Genostem (acronym for “Adult mesenchymal stem cells engineering for connective tissue disorders. From the bench to the bed side”) has been an European consortium of 30 teams working together on human bone marrow Mesenchymal Stem Cell (MSC) biological properties and repair capacity. Part of Genostem activity has been dedicated to the study of basic issues on undifferentiated MSCs properties and on signalling pathways leading to the differentiation into 3 of the connective tissue lineages, osteoblastic, chondrocytic and tenocytic. We have evidenced that native bone marrow MSCs and stromal cells, forming the niche of hematopoietic stem cells, were the same cellular entity located abluminally from marrow sinus endothelial cells. We have also shown that culture-amplified, clonogenic and highly-proliferative MSCs were bona fide stem cells, sharing with other stem cell types the major attributes of self-renewal and of multipotential priming to the lineages to which they can differentiate (osteoblasts, chondrocytes, adipocytes and vascular smooth muscle cells/pericytes). Extensive transcription profiling and in vitro and in vivo assays were applied to identify genes involved in differentiation. Thus we have described novel factors implicated in osteogenesis (FHL2, ITGA5, Fgf18), chondrogenesis (FOXO1A) and tenogenesis (Smad8). Another part of Genostem activity has been devoted to studies of the repair capacity of MSCs in animal models, a prerequisite for future clinical trials. We have developed novel scaffolds (chitosan, pharmacologically active microcarriers) useful for the repair of both bone and cartilage. Finally and most importantly, we have shown that locally implanted MSCs effectively repair bone, cartilage and tendon.
doi:10.1007/s12015-010-9125-6
PMCID: PMC3213118  PMID: 20198518
Animals; Bone Marrow Cells; cytology; Cell Culture Techniques; standards; Cell Differentiation; Cell Proliferation; Humans; Mesenchymal Stem Cells; cytology; Tissue Engineering; differentiation; stem cell; bone; cartilage; tendon; smooth muscle; regenerative medicine
21.  Systems medicine and integrated care to combat chronic noncommunicable diseases 
Genome Medicine  2011;3(7):43.
We propose an innovative, integrated, cost-effective health system to combat major non-communicable diseases (NCDs), including cardiovascular, chronic respiratory, metabolic, rheumatologic and neurologic disorders and cancers, which together are the predominant health problem of the 21st century. This proposed holistic strategy involves comprehensive patient-centered integrated care and multi-scale, multi-modal and multi-level systems approaches to tackle NCDs as a common group of diseases. Rather than studying each disease individually, it will take into account their intertwined gene-environment, socio-economic interactions and co-morbidities that lead to individual-specific complex phenotypes. It will implement a road map for predictive, preventive, personalized and participatory (P4) medicine based on a robust and extensive knowledge management infrastructure that contains individual patient information. It will be supported by strategic partnerships involving all stakeholders, including general practitioners associated with patient-centered care. This systems medicine strategy, which will take a holistic approach to disease, is designed to allow the results to be used globally, taking into account the needs and specificities of local economies and health systems.
doi:10.1186/gm259
PMCID: PMC3221551  PMID: 21745417
22.  Mesenchymal stem cells immunosuppressive properties: is it specific to bone marrow-derived cells? 
Based on their capacity to suppress immune responses, multipotent mesenchymal stromal cells (MSCs) are intensively studied for regenerative medicine. Moreover, MSCs have paracrine effects, including immunomodulation that occurs through the secretion of soluble mediators, including nitric oxide or interleukin-6, transforming growth factor-beta, human leukocyte antigen G5, and prostaglandin E2. MSCs in the bone marrow are in close contact with T and B cells and regulate immunological memory by organizing defined numbers of dedicated survival niches for plasma cells and memory T cells in the bone marrow. All of these biological effects are probably shared by all stromal cells, including fibroblasts and stem cells isolated from exfoliated deciduous teeth. The therapeutical implications are discussed.
doi:10.1186/scrt15
PMCID: PMC2905091  PMID: 20529386
23.  Immunosuppression by mesenchymal stem cells: mechanisms and clinical applications 
Mesenchymal stem cells (MSCs) are multipotential nonhematopoietic progenitor cells that are isolated from many adult tissues, in particular from the bone marrow and adipose tissue. Along with their capacity for differentiating into cells of mesodermal lineage, such as adipocytes, osteoblasts and chondrocytes, these cells have also generated great interest for their ability to display immunomodulatory capacities. Indeed, a major breakthrough came with the finding that they are able to induce peripheral tolerance, suggesting they may be used as therapeutic tools in immune-mediated disorders. The present review aims at discussing the current knowledge on the targets and mechanisms of MSC-mediated immunosuppression as well as the potential use of MSCs as modulators of immune responses in a variety of diseases related to alloreactive immunity or autoimmunity
doi:10.1186/scrt2
PMCID: PMC2873698  PMID: 20504283
24.  Mesenchymal stem cells in arthritis: role of bone marrow microenvironment 
Based on their capacity to suppress immune responses, multipotent mesenchymal stromal cells (MSCs) are intensively studied for regenerative medicine. Moreover, MSCs are potent immunomodulatory cells that occur through the secretion of soluble mediators including nitric oxide, transforming growth factor beta, and HLAG5. The MSCs, however, are also able to express inflammatory mediators such as prostaglandin E2 or IL-6. MSCs in the bone marrow are in close contact with T cells and B cells, and they regulate immunological memory by organizing defined numbers of dedicated survival niches for plasma cells and memory T cells in the bone marrow. The role of MSCs in arthritis remains controversial - in some studies, murine allogeneic MSCs are able to decrease arthritis; in other studies, MSCs worsen the local inflammation. A recent paper in Arthritis Research and Therapy shows that bone marrow MSCs have decreased osteoblastic potential in rheumatoid arthritis, which may be related to chronic inflammation or to loss of expression of IL-1 receptor agonist. That article raises the importance of the bone marrow microenvironment for MSC biology.
doi:10.1186/ar3105
PMCID: PMC2945053  PMID: 20804569
25.  IL-6-Dependent PGE2 Secretion by Mesenchymal Stem Cells Inhibits Local Inflammation in Experimental Arthritis 
PLoS ONE  2010;5(12):e14247.
Background
Based on their capacity to suppress immune responses, multipotent mesenchymal stromal cells (MSC) are intensively studied for various clinical applications. Although it has been shown in vitro that the immunomodulatory effect of MSCs mainly occurs through the secretion of soluble mediators, the mechanism is still not completely understood. The aim of the present study was to better understand the mechanisms underlying the suppressive effect of MSCs in vivo, using cells isolated from mice deficient in the production of inducible nitric oxide synthase (iNOS) or interleukin (IL)-6 in the murine model of collagen-induced arthritis.
Principal Findings
In the present study, we show that primary murine MSCs from various strains of mice or isolated from mice deficient for iNOS or IL-6 exhibit different immunosuppressive potential. The immunomodulatory function of MSCs was mainly attributed to IL-6-dependent secretion of prostaglandin E2 (PGE2) with a minor role for NO. To address the role of these molecules in vivo, we used the collagen-induced arthritis as an experimental model of immune-mediated disorder. MSCs effectively inhibited collagen-induced inflammation during a narrow therapeutic window. In contrast to wild type MSCs, IL-6-deficient MSCs and to a lesser extent iNOS-deficient MSCs were not able to reduce the clinical signs of arthritis. Finally, we show that, independently of NO or IL-6 secretion or Treg cell induction, MSCs modulate the host response by inducing a switch to a Th2 immune response.
Significance
Our data indicate that MSCs mediate their immunosuppressive effect via two modes of action: locally, they reduce inflammation through the secretion of anti-proliferative mediators, such as NO and mainly PGE2, and systemically they switch the host response from a Th1/Th17 towards a Th2 immune profile.
doi:10.1371/journal.pone.0014247
PMCID: PMC2998425  PMID: 21151872

Results 1-25 (31)