Claire Bony

Mesenchymal Stem Cells Inhibit the Differentiation of Dendritic Cells Through an Interleukin‐6‐Dependent Mechanism

Mesenchymal stem cells (MSC) are of particular interest for their potential clinical use in tissue engineering as well as for their capacity to reduce the incidence and severity of graft‐versus‐host disease in allogeneic transplantation. We have previously shown that MSC‐mediated immune suppression acts via the secretion of soluble factor(s) induced upon stimulation. The aim of this study was to identify the molecule(s) involved and the underlying mechanism(s). We show that murine MSC secrete high levels of interleukin (IL)‐6 and vascular endothelial growth factor, which are directly correlated to the inhibition of T‐cell proliferation. The T‐cell activation is partially restored upon addition of a neutralizing anti‐IL‐6 antibody or the prostaglandin E2 inhibitor indomethacin. Interestingly, no indoleamine 2,3‐dioxygenase activity was detected in our conditions. Instead, we show that MSC reduce the expression of major histocompatibility complex class II, CD40, and CD86 costimulatory molecules on mature dendritic cells (DC), which was responsible for a decrease in T‐cell proliferation. Moreover, we show that the differentiation of bone marrow progenitors into DC cultured with conditioned supernatants from MSC was partly inhibited through the secretion of IL‐6. Altogether, these data suggest that IL‐6 is involved in the immunoregulatory mechanism mediated by MSC through a partial inhibition of DC differentiation but is probably not the main mechanism.

Cell specific differences between human adipose-derived and mesenchymal–stromal cells despite similar differentiation potentials

Stromal cells from bone marrow and adipose tissue are attractive sources of adult progenitors for cell-based therapy. However, whether those cell populations represent intrinsically different cell types is still largely under debate. The aim of this study was to systematically and quantitatively compare adipose-derived stromal cells (ADSC) and bone marrow-derived multipotent mesenchymal-stromal cells (BM-MSC). The quantitative comparison was realized using Taqman Low Density Array, 2D electrophoresis and differentiation functional assays in vitro. Furthermore, cells engineered to express TGFbeta1 were injected into the intra-articular space of mouse knee joints in order to determine whether they were able to form new differentiated tissues in vivo. Our data revealed cell specific differences at transcriptional and proteomic levels between both cell types according to their tissue origin as well as functional differences in their differentiation processes towards adipogenic, osteogenic and chondrogenic programs. Nevertheless, in vitro as well as in vivo ADSC displayed the same ability than MSC to differentiate towards chondrocytes/osteoblasts, comforting the status of both cell sources as promising regenerative cells. In summary, our observations indicate that ADSC and MSC are fundamentally different cell types and differently committed cells.

IL-6-Dependent PGE2 Secretion by Mesenchymal Stem Cells Inhibits Local Inflammation in Experimental Arthritis

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.

Microenvironmental changes during differentiation of mesenchymal stem cells towards chondrocytes

Chondrogenesis is a process involving stem-cell differentiation through the coordinated effects of growth/differentiation factors and extracellular matrix (ECM) components. Recently, mesenchymal stem cells (MSCs) were found within the cartilage, which constitutes a specific niche composed of ECM proteins with unique features. Therefore, we hypothesized that the induction of MSC differentiation towards chondrocytes might be induced and/or influenced by molecules from the microenvironment. Using microarray analysis, we previously identified genes that are regulated during MSC differentiation towards chondrocytes. In this study, we wanted to precisely assess the differential expression of genes associated with the microenvironment using a large-scale real-time PCR assay, according to the simultaneous detection of up to 384 mRNAs in one sample. Chondrogenesis of bone-marrow-derived human MSCs was induced by culture in micropellet for various periods of time. Total RNA was extracted and submitted to quantitative RT-PCR. We identified molecules already known to be involved in attachment and cell migration, including syndecans, glypicans, gelsolin, decorin, fibronectin, and type II, IX and XI collagens. Importantly, we detected the expression of molecules that were not previously associated with MSCs or chondrocytes, namely metalloproteases (MMP-7 and MMP-28), molecules of the connective tissue growth factor (CTGF); cef10/cyr61 and nov (CCN) family (CCN3 and CCN4), chemokines and their receptors chemokine CXC motif ligand (CXCL1), Fms-related tyrosine kinase 3 ligand (FlT3L), chemokine CC motif receptor (CCR3 and CCR4), molecules with A Disintegrin And Metalloproteinase domain (ADAM8, ADAM9, ADAM19, ADAM23, A Disintegrin And Metalloproteinase with thrombospondin type 1 motif ADAMTS-4 and ADAMTS-5), cadherins (4 and 13) and integrins (α4, α7 and β5). Our data suggest that crosstalk between ECM components of the microenvironment and MSCs within the cartilage is responsible for the differentiation of MSCs into chondrocytes.

Mesenchymal Stem Cell‐Derived Interleukin 1 Receptor Antagonist Promotes Macrophage Polarization and Inhibits B Cell Differentiation

The role of interleukin 1 receptor antagonist (IL1RA) in mediating the immunosuppressive effect of mesenchymal stem/stromal cells (MSCs) has been reported in several studies. However, how MSC‐derived IL1RA influences the host response has not been clearly investigated. We therefore derived MSCs from the bone marrow of IL1RA knockout mice and evaluated their immunosuppressive effect on different immune cell subsets. IL1RA deficient (IL1RA−/−) or wild type (wt) MSCs inhibited to the same extend the proliferation of T lymphocytes. On the contrary, IL1RA−/− MSCs were less effective than wt MSCs to induce in vitro the macrophage polarization from M1 to M2 phenotype secreting IL10 and exerting a suppressive effect on CD4+ T cells. Moreover compared with wt MSCs, IL1RA−/− MSCs did not efficiently support the survival of quiescent B lymphocytes and block their differentiation toward CD19+CD138+ plasmablasts secreting IgG antibodies. The effectiveness of IL1RA secreted by MSCs in controlling inflammation was further shown in vivo using the collagen‐induced arthritis murine model. MSCs lacking IL1RA expression were unable to protect mice from arthritic progression and even worsened clinical signs, as shown by higher arthritic score and incidence than control arthritic mice. IL1RA−/− MSCs were not able to decrease the percentage of Th17 lymphocytes and increase the percentage of Treg cells as well as decreasing the differentiation of B cells toward plasmablasts. Altogether, our results provide evidence of the key role of IL1RA secreted by MSCs to both control the polarization of macrophages toward a M2 phenotype and inhibit B cell differentiation in vivo. Stem Cells 2016;34:483–492

Mesenchymal stem cell‐derived IL1RA promotes macrophage polarization and inhibits B cell differentiation

The role of interleukin 1 receptor antagonist (IL1RA) in mediating the immunosuppressive effect of mesenchymal stem/stromal cells (MSCs) has been reported in several studies. However, how MSC‐derived IL1RA influences the host response has not been clearly investigated. We therefore derived MSCs from the bone marrow of IL1RA knockout mice and evaluated their immunosuppressive effect on different immune cell subsets. IL1RA deficient (IL1RA−/−) or wild type (wt) MSCs inhibited to the same extend the proliferation of T lymphocytes. On the contrary, IL1RA−/− MSCs were less effective than wt MSCs to induce in vitro the macrophage polarization from M1 to M2 phenotype secreting IL10 and exerting a suppressive effect on CD4+ T cells. Moreover compared with wt MSCs, IL1RA−/− MSCs did not efficiently support the survival of quiescent B lymphocytes and block their differentiation toward CD19+CD138+ plasmablasts secreting IgG antibodies. The effectiveness of IL1RA secreted by MSCs in controlling inflammation was further shown in vivo using the collagen‐induced arthritis murine model. MSCs lacking IL1RA expression were unable to protect mice from arthritic progression and even worsened clinical signs, as shown by higher arthritic score and incidence than control arthritic mice. IL1RA−/− MSCs were not able to decrease the percentage of Th17 lymphocytes and increase the percentage of Treg cells as well as decreasing the differentiation of B cells toward plasmablasts. Altogether, our results provide evidence of the key role of IL1RA secreted by MSCs to both control the polarization of macrophages toward a M2 phenotype and inhibit B cell differentiation in vivo. Stem Cells 2016;34:483–492

Skin fibroblasts are potent suppressors of inflammation in experimental arthritis

Objectives Mesenchymal stromal cells (MSC) are characterised by their capacity to suppress immune reactions. This function was reported to be shared in vitro by fibroblasts but their role has been poorly investigated in vivo. This study explored whether fibroblasts isolated from skin may suppress the host immune response in a model of autoimmune disorder. Methods and Results It was first confirmed that skin fibroblasts lack the capacity to differentiate into osteoblasts or chondrocytes but possess the capacity to inhibit in vitro the proliferation of T lymphocytes. Fibroblasts also secrete modulatory molecules, in particular prostaglandin E2 and nitric oxide, similar to MSC. To assess their role in vivo, the collagen-induced arthritis model was used, and showed that similar to MSC the intravenous injection of fibroblasts efficiently suppress clinical signs of arthritis and delay disease onset. This effect was associated with reduced inflammation as reflected by biological parameters and increased levels of IL-5, IL-10 and IL-13 in the spleens of treated mice. To characterise the mechanism of immunosuppression further, phenotypic analyses were performed and could not detect any induction of CD4 CD25 Foxp3+ regulatory T (Treg) cells. A population of CD4 IL-10+ T cells was, however, detected that was slightly increased after fibroblast injection and significantly upregulated after MSC administration. Conclusions This study gives the first evidence for an immunosuppressive role of fibroblasts in vivo, and strongly suggests that fibroblasts induce a T-helper type 2 immune profile, although the possibility that IL-10-secreting Treg cells may be generated cannot be excluded.

Antifibrotic, Antioxidant, and Immunomodulatory Effects of Mesenchymal Stem Cells in HOCl-Induced Systemic Sclerosis.

Systemic sclerosis (SSc) is a rare intractable disease with unmet medical need and fibrosis‐related mortality. Absence of efficient treatments has prompted the development of novel therapeutic strategies, among which mesenchymal stem cells/stromal cells (MSCs) or progenitor stromal cells appear to be one of the most attractive options. The purpose of this study was to use the murine model of hypochlorite‐induced SSc to investigate the systemic effects of MSCs on the main features of the diffuse form of the disease: skin and lung fibrosis, autoimmunity, and oxidative status.

Comparison between Stromal Vascular Fraction and Adipose Mesenchymal Stem Cells in Remodeling Hypertrophic Scars

Hypertrophic scars (HTS) are characterized by excessive amount of collagen deposition and principally occur following burn injuries or surgeries. In absence of effective treatments, the use of mesenchymal stem/stromal cells, which have been shown to attenuate fibrosis in various applications, seems of interest. The objectives of the present study were therefore to evaluate the effect of human adipose tissue-derived mesenchymal stem cells (hASC) on a pre-existing HTS in a humanized skin graft model in Nude mice and to compare the efficacy of hASCs versus stromal vascular fraction (SVF). We found that injection of SVF or hASCs resulted in an attenuation of HTS as noticed after clinical evaluation of skin thickness, which was associated with lower total collagen contents in the skins of treated mice and a reduced dermis thickness after histological analysis. Although both SVF and hASCs were able to significantly reduce the clinical and histological parameters of HTS, hASCs appeared to be more efficient than SVF. The therapeutic effect of hASCs was attributed to higher expression of TGFβ3 and HGF, which are important anti-fibrotic mediators, and to higher levels of MMP-2 and MMP-2/TIMP-2 ratio, which reflect the remodelling activity responsible for fibrosis resorption. These results demonstrated the therapeutic potential of hASCs for clinical applications of hypertrophic scarring.

Adipose Mesenchymal Stem Cells Isolated after Manual or Water-jet-Assisted Liposuction Display Similar Properties

Mesenchymal stem or stromal cells (MSC) are under investigation in many clinical trials for their therapeutic potential in a variety of diseases, including autoimmune and inflammatory disorders. One of the main sources of MSCs is the adipose tissue, which is mainly obtained by manual liposuction using a cannula linked to a syringe. However, in the past years, a number of devices for fat liposuction intended for clinical use have been commercialized but few papers have compared these procedures in terms of stromal vascular fraction (SVF) or adipose mesenchymal stromal cells (ASC). The objective of the present study was to compare and qualify for clinical use the ASC obtained from fat isolated with the manual or the Bodyjet® water-jet-assisted procedure. Although the initial number of cells obtained after collagenase digestion was higher with the manual procedure, the percentage of dead cells, the number of colony forming unit-fibroblast and the phenotype of cells were identical in the SVF at isolation (day 0) and in the ASC populations at day 14. We also showed that the osteogenic and adipogenic differentiation potentials of ASCs were identical between preparations while a slight but significant higher in vitro immunosuppressive effect was observed with ASCs isolated from fat removed with a cannula. The difference in the immunomodulatory effect between ASC populations was, however, not observed in vivo using the delayed-type hypersensitivity (DTH) model. Our data, therefore, indicate that the procedure for fat liposuction does not impact the characteristics or the therapeutic function of ASCs.