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Musculoskeletal stromal cells’ (MSCs’) metabolism impacts cell differentiation as well as immune function. During osteogenic and adipogenic differentiation, BM-MSCs show a preference for glycolysis during proliferation but shift to an oxidative phosphorylation (OxPhos)-dependent metabolism. The MSC immunoregulatory fate is achieved with cell polarization, and the result is sustained production of immunoregulatory molecules (including PGE2, HGF, IL1RA, IL6, IL8, IDO activity) in response to inflammatory stimuli. MSCs adapt their energetic metabolism when acquiring immunomodulatory property and shift to aerobic glycolysis. This can be achieved via hypoxia, pretreatment with small molecule-metabolic mediators such as oligomycin, or AKT/mTOR pathway modulation. The immunoregulatory effect of MSC on macrophages polarization and Th17 switch is related to the glycolytic status of the MSC. Indeed, MSCs pretreated with oligomycin decreased the M1/M2 ratio, inhibited T-CD4 proliferation, and prevented Th17 switch. Mitochondrial activity also impacts MSC metabolism. In the bone marrow, MSCs are present in a quiescent, low proliferation, but they keep their multi-progenitor function. In this stage, they appear to be glycolytic with active mitochondria (MT) status. During MSC expansion, we observed a metabolic shift toward OXPhos, coupled with an increased MT activity. An increased production of ROS and dysfunctional mitochondria is associated with the metabolic shift to glycolysis. In contrast, when MSC underwent chondro or osteoblast differentiation, they showed a decreased glycolysis and inhibition of the pentose phosphate pathway (PPP). In parallel the mitochondrial enzymatic activities increased associated with oxidative phosphorylation enhancement. MSCs respond to damaged or inflamed tissue through the transfer of MT to injured and immune cells, conveying a type of signaling that contributes to the restoration of cell homeostasis and immune function. The delivery of MT into injured cells increased ATP levels which in turn maintained cellular bioenergetics and recovered cell functions. MSC-derived MT may be transferred via tunneling nanotubes to undifferentiated cardiomyocytes and leading to their maturation. In this review, we will decipher the pathways and the mechanisms responsible for mitochondria transfer and activity. The eventual reversal of the metabolic and pro-inflammatory profile induced by the MT transfer will open new avenues for the control of inflammatory diseases.

International audience; Objectives: Mesenchymal Stem/Stromal Cells (MSC) are promising therapeutic tools for inflammatory diseases due to their potent immunoregulatory capacities. Their suppressive activity mainly depends on inflammatory cues that have been recently associated with changes in MSC bioenergetic status towards a glycolytic metabolism. However, the molecular mechanisms behind this metabolic reprogramming and its impact on MSC therapeutic properties have not been investigated. Methods: Human and murine-derived MSC were metabolically reprogramed using pro-inflammatory cytokines, an inhibitor of ATP synthase (oligomycin), or 2-deoxy-D-glucose (2DG). The immunosuppressive activity of these cells was tested in vitro using co-culture experiments with pro-inflammatory T cells and in vivo with the Delayed-Type Hypersensitivity (DTH) and the Graph versus Host Disease (GVHD) murine models. Results: We found that the oligomycin-mediated pro-glycolytic switch of MSC significantly enhanced their immunosuppressive properties in vitro. Conversely, glycolysis inhibition using 2DG significantly reduced MSC immunoregulatory effects. Moreover, in vivo, MSC glycolytic reprogramming significantly increased their therapeutic benefit in the DTH and GVHD mouse models. Finally, we demonstrated that the MSC glycolytic switch effect partly depends on the activation of the AMPK signaling pathway. Conclusion: Altogether, our findings show that AMPK-dependent glycolytic reprogramming of MSC using an ATP synthase inhibitor contributes to their immunosuppressive and therapeutic functions, and suggest that pro-glycolytic drugs might be used to improve MSC-based therapy.

International audience; Mesenchymal stem cells (MSCs) exhibit potent immunoregulatory abilities by interacting with cells of the adaptive and innate immune system. In vitro, MSCs inhibit the differentiation of T cells into T helper 17 (Th17) cells and repress their proliferation. In vivo, the administration of MSCs to treat various experimental inflammatory and autoimmune diseases, such as rheumatoid arthritis, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and bowel disease showed promising therapeutic results. These therapeutic properties mediated by MSCs are associated with an attenuated immune response characterized by a reduced frequency of Th17 cells and the generation of regulatory T cells. In this manuscript, we review how MSC and Th17 cells interact, communicate, and exchange information through different ways such as cell-to-cell contact, secretion of soluble factors, and organelle transfer. Moreover, we discuss the consequences of this dynamic dialogue between MSC and Th17 well described by their phenotypic and functional plasticity.

International audience; Sepsis is an acute systemic inflammatory response of the body to microbial infection and a life threatening condition associated with multiple organ failure. Survivors may display long-term disability with muscle weakness that remains poorly understood. Recent data suggest that long-term myopathy in sepsis survivors is due to failure of skeletal muscle stem cells (satellite cells) to regenerate the muscle. Satellite cells impairment in the acute phase of sepsis is linked to unusual mitochondrial dysfunctions, characterized by a dramatic reduction of the mitochondrial mass and hyperactivity of residual organelles. Survivors maintain the impairment of satellite cells, including alterations of the mitochondrial DNA (mtDNA), in the long-term. This condition can be rescued by treatment with mesenchymal stem cells (MSCs) that restore mtDNA alterations and mitochondrial function in satellite cells, and in fine their regenerative potential. Injection of MSCs in turn increases the force of isolated muscle fibers and of the whole animal, and improves the survival rate. These effects occur in the context of reduced inflammation markers that also raised during sepsis. Targeting muscle stem cells mitochondria, in a context of reduced inflammation, may represent a valuable strategy to reduce morbidity and long-term impairment of the muscle upon sepsis.

IF 1.331; International audience; The human amniotic membrane (hAM) has been successfully used as a natural carrier containing amniotic mesenchymal stromal cells, epithelial cells and growth factors. It has a little or no immunogenicity, and possesses useful anti-microbial, anti-inflammatory, anti-fibrotic and analgesic properties. It has been used for many years in several indications for soft tissue repair. We previously reported that hAM represents a natural and preformed sheet containing highly potent stem cells, and could thus be used for bone repair. Indeed, native hAM possesses pre-osteoblastic potential that can easily be stimulated, even as far as mineralization, by means of in vitro osteogenic culture. However, cell culture induces damage to the tissue, as well as to cell phenotype and function. The aim of this study was to evaluate new bone formation by fresh and in vitro osteodifferentiated hAM, alone or associated with an additional scaffold presenting osteoinductive properties. Moreover, we also aimed to determine the effect of in vitro hAM pre-osteodifferentiation on its in vivo biocompatibility/tissue degradation. Results showed that neither fresh nor osteodifferentiated hAM induced ectopic bone formation, whether or not it was associated with the osteoinductive scaffold. Secondly, fresh and osteodifferentiated hAM presented similar in vivo tissue degradation, suggesting that in vitro hAM pre-osteodifferentiation did not influence its in vivo biocompatibility.

International audience; Thanks to their immune properties, the mesenchymal stem cells (MSC) are a promising source for cell therapy. Current clinical trials show that MSC administrated to patients can treat different diseases (graft-versus-host disease (GVHD), liver cirrhosis, systemic lupus, erythematosus, rheumatoid arthritis, type I diabetes…). In this case, the most common mode of cell administration is the intravenous injection, and the hemodynamic environment of cells induced by blood circulation could interfere on their behavior during the migration and homing towards the injured site. After a brief review of the mechanobiology concept, this paper will help in understanding how the mechanical environment could interact with MSC behavior once they are injected to patient in cell-based treatment.

International audience; Mesenchymal stem cells (MSC) may transdifferentiate into neural cells in vitro under the influence of matrix molecules and growth factors present in neurogenic niches. However, further experiments on the behavior of such stem cells remain to be done in vivo. In this study, rat MSC (rMSC) have been grafted in a neurogenic environment of the rat brain, the subventricular zone (SVZ), in order to detect and follow their migration using superparamagnetic iron oxide (SPIO) nanoparticles. We sought to characterize the potential effect of iron loading on the behavior of rMSC as well as to address the potential of rMSC to migrate when exposed to the adequate brain microenvironment. 1-hydroxyethylidene-1.1-bisphosphonic acid (HEDP)-coated SPIO nanoparticles efficiently labeled rMSC without significant adverse effects on cell viability and on the in vitro differentiation potential. In opposition to iron-labeled rat neural stem cells (rNSC), used as a positive control, iron-labeled rMSC did not respond to the SVZ microenvironment in vivo and did not migrate, unless a mechanical lesion of the olfactory bulb was performed. This confirmed the known potential of iron-labeled rMSC to migrate toward lesions and, as far as we know, this is the first study describing such a long distance migration from the SVZ toward the olfactory bulb through the rostral migratory stream (RMS).

International audience; INTRODUCTION: Mesenchymal stem cells (MSCs) possess unique immunomodulatory properties. They are able to suppress allogenic T-cell response and modify maturation of antigen-presenting cells. Their role in the treatment of severe graft versus host disease has been reported. The underlying molecular mechanisms of immunosuppression are currently being investigated. Histocompatibility locus antigen (HLA)-G is a nonclassical major histocompatibility complex class I antigen with strong immune-inhibitory properties. METHODS: We studied the role of HLA-G on MSC-induced immunosuppression. The expression of HLA-G on human MSCs cultured alone and in mixed lymphocytes reaction (MSC/MLR) was analyzed. RESULTS: We found that HLA-G can be detected on MSCs by real-time reverse-phase polymerase chain reaction, immunofluorescence, flow cytometry (52.4+/-3.6%), and enzyme-linked immunosorbent assay in the supernatant (38.7+/-5.2 ng/mL). HLA-G protein expression is constitutive and the level is not modified upon stimulation by allogenic lymphocytes in MSC/MLR. The functional role of HLA-G protein expressed by MSCs was analyzed using the 87G anti-HLA-G blocking antibody in a MSC/MLR. We found that blocking HLA-G molecule significantly raised lymphocyte proliferation in MSC/MLR (35.5%, P=0.01). CONCLUSION: Our findings provide evidences supporting involvement of HLA-G in the immunosuppressive properties of MSCs. These results emphasize the potential application of MSCs as a relevant therapeutic candidate in transplantation.

Aims: Mesenchymal stem cells (MSCs) from adult bone marrow provide an exciting and promising stem cell population for the repair of bone in skeletal diseases. Here, we describe a new generation of collagen nanofiber implant functionalized with growth factor BMP-7 nanoreservoirs and equipped with human MSC microtissues (MTs) for regenerative nanomedicine. Materials & methods: By using a 3D nanofibrous collagen membrane and by adding MTs rather than single cells, we optimize the microenvironment for cell colonization, differentiation and growth. Results & conclusion: Furthermore, in this study, we have shown that by combining BMP-7 with these MSC MTs in this double 3D environment, we further accelerate bone growth in vivo. The strategy described here should enhance the efficiency of therapeutic implants compared with current simplistic approaches used in the clinic today based on collagen implants soaked in bone morphogenic proteins.

International audience; A combination of autologous bone marrow stromal cells (BMSCs) and biomaterials is a strategy largely developed in bone tissue engineering, and subcutaneous implantation in rodents or large animals is often a first step to evaluate the potential of new biomaterials. This study aimed at investigating the influence of the immune status of the recipient animal on BMSCs-induced bone formation. BMSCs prepared from C57BL/6 mice, composed of a mixture of mesenchymal stromal and monocytic cells, were combined with a biomaterial that consisted of biphasic calcium phosphate (BCP) particles and plasma clot. This composite was implanted subcutaneously either in syngenic C57BL/6 immune-competent mice or in T-lymphocyte-deficient Nude (Nude) mice. Using histology, immunohistochemistry, and histomorphometry, we show here that this BMSC/BCP/plasma clot composite implanted in Nude mice induces the formation of mature lamellar bone associated to hematopoietic areas and numerous vessels. Comparatively, implantation in C57BL/6 results in the formation of woven bone without hematopoietic tissue, a lower number of new vessels, and numerous multinucleated giant cells (MNGCs). In situ hybridization, which enabled to follow the fate of the BMSCs, revealed that BMSCs implanted in Nude mice survived longer than BMSCs implanted in C57BL/6 mice. Quantitative expression analysis of 280 genes in the implants indicated that the differences between C57BL/6 and Nude implants corresponded almost exclusively to genes related to the immune response. Gene expression profile in C57BL/6 implants was consistent with a mild chronic inflammation reaction characterized by Th1, Th2, and cytotoxic T-lymphocyte activation. In the implants retrieved from T-deficient Nude mice, Mmp14, Il6st, and Tgfbr3 genes were over-expressed, suggesting their putative role in bone regeneration and hematopoiesis. In conclusion, we show here that the T-mediated inflammatory microenvironment is detrimental to BMSCs-induced bone formation and shortens the survival of implanted cells. Conversely, the lack of T-lymphocyte reaction in T-deficient animals is beneficial to BMSCs-induced mature bone formation. This should be taken into account when evaluating cell/biomaterial composites in these models.

Objectives— Studying the mechanisms of neovascularization and evaluating the effects of proangiogenic strategies require accurate analysis of the neovascular network. We sought to evaluate the contribution of the microcomputed tomography (mCT) providing high-resolution 3-dimensional (3D) structural data, to a better comprehension of the well-studied mouse hindlimb postischemic neovascularization. Methods and Results— We showed a predominant arteriogenesis process in the thigh and a predominant angiogenesis-related process in the tibiofibular region, in response to ischemia during the first 15 days. After 15 days, mCT quantitative analysis reveals a remodeling of arterial neovessels and a regression depending on the restoration of the blood flow. We provided also new mCT data on the rapid and potent angiogenic effects of mesenchymal stem cell therapy on vessel formation and organization. We discussed the contribution of this technique compared with or in addition to data generated by the more conventional approaches. Conclusion— This study demonstrated that optimized mCT is a robust method for providing new insights into the 3D understanding of postischemic vessel formation.

International audience; The use of mesenchymal stem cells (MSCs) for tissue regeneration is often hampered by modest engraftment in host tissue. This study was designed to quantitatively compare MSCs engraftment rates after delivery using a polysaccharide-based porous scaffold or endocardial (EC) injection in a rat myocardial infarction model. Cellular engraftment was measured by quantitative reverse transcription-polymerase chain reaction using MSCs previously transduced with a lentiviral vector that expresses green fluorescent protein (GFP). The use of a scaffold promoted local cellular engraftment and survival. The number of residual GFP(+) cells was greater with the scaffold than after EC injection (9.7% vs. 5.1% at 1 month and 16.3% vs. 6.1% at 2 months, respectively [n=5]). This concurred with a significant increase in mRNA vascular endothelial growth factor level in the scaffold group (p

International audience; Since their efficiency to treat graft versus host disease has been proven, mesenchymal stem cells (MSC) represent a promising cell therapy approach for the treatment of immune disorders. In this context, much attention has focused on their mechanisms of action, in particular once the fact that their immune properties are also crucial for their efficiency in regenerative medicine was demonstrated. By their production of various and redundant soluble factors, MSC exert powerful anti-inflammatory and immunosuppressive effects targeting the main immune cell subsets. These immunoregulatory properties are essentially inducible by inflammatory mediators. In addition, it is now clear that allogeneic MSC are not immunoprivileged in immunocompetent recipient in agreement with their low persistence in vivo. They should thus display an early "touch-and-go" effect involving both direct interactions with recruited immune effectors and further amplification of this immunosuppression process through activation or conditioning of other regulatory immune cells. A better understanding of immunological properties of MSC will clearly improve their use in clinical settings.; Les cellules souches mésenchymateuses (CSM) possèdent des propriétés immunosuppressives très vastes liées à la production de facteurs solubles inductibles qui inhibent l'activation des principaux effecteurs de l'immunité. L'intérêt de ces propriétés a été confirmé dans des essais cliniques spectaculaires chez des patients atteints de la maladie du greffon contre l'hôte, une complication fréquente et grave des allogreffes de cellules souches hématopoïétiques. Depuis, les applications de ce potentiel anti-inflammatoire et immunosuppresseur des CSM ont été étendues à la médecine régénératrice puisque les capacités de réparation des CSM semblent étroitement liées à leurs propriétés immunologiques, démontrant tout l'intérêt d'une compréhension fine des interactions entre les CSM et les cellules immunitaires.

International audience; Multipotent mesenchymal stromal cells (MSCs) raise great interest for brain cell therapy due to their ease of isolation from bone marrow, their immunomodulatory and tissue repair capacities, their ability to differentiate into neuronal-like cells and to secrete a variety of growth factors and chemokines. In this study, we assessed the effects of a subpopulation of human MSCs, the marrow-isolated adult multilineage inducible (MIAMI) cells, combined with pharmacologically active microcarriers (PAMs) in a rat model of Parkinson's disease (PD). PAMs are biodegradable and non-cytotoxic poly(lactic-co-glycolic acid) microspheres, coated by a biomimetic surface and releasing a therapeutic protein, which acts on the cells conveyed on their surface and on their microenvironment. In this study, PAMs were coated with laminin and designed to release neurotrophin 3 (NT3), which stimulate the neuronal-like differentiation of MIAMI cells and promote neuronal survival. After adhesion of dopaminergic-induced (DI)-MIAMI cells to PAMs in vitro, the complexes were grafted in the partially dopaminergic-deafferented striatum of rats which led to a strong reduction of the amphetamine-induced rotational behavior together with the protection/repair of the nigrostriatal pathway. These effects were correlated with the increased survival of DI-MIAMI cells that secreted a wide range of growth factors and chemokines. Moreover, the observed increased expression of tyrosine hydroxylase by cells transplanted with PAMs may contribute to this functional recovery.

International audience; Stem cell-based therapy has been proposed as a potential means of treatment for a variety of brain disorders. Because ethical and technical issues have so far limited the clinical translation of research using embryonic/fetal cells and neural tissue, respectively, the search for alternative sources of therapeutic stem cells remains ongoing. Here, we report that upon transplantation into mice with chemically induced hippocampal lesions, human olfactory ecto-mesenchymal stem cells (OE-MSCs) - adult stem cells from human nasal olfactory lamina propria - migrated toward the sites of neural damage, where they differentiated into neurons. Additionally, transplanted OE-MSCs stimulated endogenous neurogenesis, restored synaptic transmission, and enhanced long-term potentiation. Mice that received transplanted OE-MSCs exhibited restoration of learning and memory on behavioral tests compared with lesioned, nontransplanted control mice. Similar results were obtained when OE-MSCs were injected into the cerebrospinal fluid. These data show that OE-MSCs can induce neurogenesis and contribute to restoration of hippocampal neuronal networks via trophic actions. They provide evidence that human olfactory tissue is a conceivable source of nervous system replacement cells. This stem cell subtype may be useful for a broad range of stem cell-related studies.

International audience; 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.

International audience; Interest has increased in the use of exogenous stem cells to optimize lung repair and serve as carriers of a therapeutic gene for genetic airway diseases such as cystic fibrosis. We investigated the survival and engraftment of exogenous stem cells after intratracheal injection, in a murine model of acute epithelial airway injury already used in gene therapy experiments on cystic fibrosis. Embryonic stem cells and mesenchymal stem cells were intratracheally injected 24 hr after 2% polidocanol administration, when epithelial airway injury was maximal. Stem cells were transfected with reporter genes immediately before administration. Reporter gene expression was analyzed in trachea-lungs and bronchoalveolar lavage, using nonfluorescence, quantitative, and sensitive methods. Enzyme-linked immunosorbent assay quantitative results showed that 0.4 to 5.5% of stem cells survived in the injured airway. Importantly, no stem cells survived in healthy airway or in the epithelial lining fluid. Using 5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside staining, transduced mesenchymal stem cells were detected in injured trachea and bronchi lumen. When the epithelium was spontaneously regenerated, the in vivo amount of engrafted mesenchymal stem cells from cell lines decreased dramatically. No stem cells from primary culture were located within the lungs at 7 days. This study demonstrated the feasibility of intratracheal cell delivery for airway diseases with acute epithelial injury.

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 99mTc-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 × 10−3 % of injected dose (ID)/g] than in the control group (3.6 ± 1.2 × 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 × 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.

International audience; Co-transplantation of mesenchymal stem cells (MSCs) and hematopoietic stem cells ameliorate hematopoietic reconstitution and induce tolerance. The immunomodulatory properties of MSCs have been demonstrated both in vivo and in vitro. MSCs can modulate function of immune cells such as T lymphocytes, antigen-presenting cells and natural killer cells. However, it is unknown whether MSCs given to patients that have undergone HSC transplantation could alleviate graft versus leukemia effect or could increase the risk of the infection. Proper characterization of MSC immunomodulatory mechanisms are crucial to anticipate the possible effect of MSC in the host. In the current report, interesting and contradictory results in the literature are reviewed in an attempt to understand the underlying mechanism. Differences in experimental designs and models used seem to be the underlying causes of discrepancy in reported results. Results of the few in vivo studies are controversial and further clinical studies are needed to confirm the efficiency and safety of MSCs in transplantation management.

Gene electrotransfer is an efficient and reproducible nonviral gene transfer technique useful for the nonpermanent expression of therapeutic transgenes. The present study established optimal conditions for the electrotransfer of reporter genes into mesenchymal stem cells (MSCs) isolated from rat bone marrow by their selective adherence to tissue-culture plasticware. The electrotransfer of the lacZ reporter gene was optimized by adjusting the pulse electric field intensity, electric pulse type, electropulsation buffer conductivity and electroporation temperature. LacZ electrotransfection into MSCs was optimal at 1500 V cm(-1) with pre-incubation in Spinner's minimum essential medium buffer at 22 degrees C. Under these conditions beta-galactosidase expression was achieved in 29+/-3% of adherent cells 48 h post transfection. The kinetics of beta-galactosidase activity revealed maintenance of beta-galactosidase production for at least 10 days. Moreover, electroporation did not affect the MSC potential for multidifferentiation; electroporated MSCs differentiated into osteoblastic, adipogenic and chondrogenic lineages to the same extent as cells that were not exposed to electric pulses. Thus, this study demonstrates the feasibility of efficient transgene electrotransfer into MSCs while preserving cell viability and multipotency.

International audience; Autologous stem cell therapy (ACT) has been proposed to prevent irradiated victims from bone marrow (BM) aplasia by grafting hematopoietic stem and progenitor cells (HSPCs) collected early after damage, provided that a functional graft of sufficient size could be produced ex vivo. To address this issue, we set up a baboon model of cell therapy in which autologous peripheral blood HSPCs collected before lethal total body irradiation were irradiated in vitro (2.5 Gy, D0 1 Gy) to mimic the cell damage, cultured in small numbers for a week in a serum-free medium in the presence of antiapoptotic cytokines and mesenchymal stem cells (MSCs) and then cografted. Our study shows that baboons cografted with expanded cells issued from 0.75 and 1 x 10(6)/kg irradiated CD34+ cells and MSCs (n=2) exhibited a stable long-term multilineage engraftment. Hematopoietic recovery became uncertain when reducing the CD34+ cell input (0.4 x 10(6)/kg CD34+ cells; n=3). However, platelet recovery was accelerated in all surviving cografted animals, when compared with baboons transplanted with unirradiated, unmanipulated CD34+ cells (0.5-1 x 10(6)/kg, n=4). Baboons grafted with MSCs alone (n=3) did not recover. In all cases, the nonhematopoietic toxicity remained huge. This baboon study suggests that ACT feasibility is limited.

Background Bone marrow (BM) cells are promising tools for vascular therapies. Here, we focused on the possibility of targeting the hypoxia-induced pulmonary artery hypertension remodeling with systemic delivery of BM-derived mesenchymal stem cells (MSCs) into non-irradiated rats. Methods Six-week-old Wistar rats were exposed to 3-week chronic hypoxia leading to pulmonary artery wall remodeling. Domiciliation of adhesive BM-derived CD45- CD73+ CD90+ MSCs was first studied after a single intravenous infusion of Indium-111-labeled MSCs followed by whole body scintigraphies and autoradiographies of different harvested organs. In a second set of experiments, enhanced-GFP labeling allowed to observe distribution at later times using sequential infusions during the 3-week hypoxia exposure. Results A 30% pulmonary retention was observed by scintigraphies and no differences were observed in the global repartition between hypoxic and control groups. Intrapulmonary radioactivity repartition was homogenous in both groups, as shown by autoradiographies. BM-derived GFP-labeled MSCs were observed with a global repartition in liver, in spleen, in lung parenchyma and rarely in the adventitial layer of remodeled vessels. Furthermore this global repartition was not modified by hypoxia. Interestingly, these cells displayed in vivo bone marrow homing, proving a preservation of their viability and function. Bone marrow homing of GFP-labeled MSCs was increased in the hypoxic group. Conclusion Adhesive BM-derived CD45- CD73+ CD90+ MSCs are not integrated in the pulmonary arteries remodeled media after repeated intravenous infusions in contrast to previously described in systemic vascular remodeling or with endothelial progenitor cells infusions.

ObjectivesMesenchymal stem/stromal cells (MSCs) are widely investigated in regenerative medicine thanks to their immunomodulatory properties. They exert their anti-inflammatory function thanks to the secretion of a number of mediators, including proteins and miRNAs, which can be released in the extracellular environment or in the cargo of extracellular vesicles (EVs). However, the role of miRNAs in the suppressive function of MSCs is controversial. The aim of the study was to identify miRNAs that contribute to the immunomodulatory function of human bone marrow-derived MSCs (BM-MSCs).MethodsHuman BM-MSCs were primed by coculture with activated peripheral blood mononuclear cells (aPBMCs). High throughput miRNA transcriptomic analysis was performed using Human MicroRNA TaqMan® Array Cards. The immunosuppressive function of miRNAs was investigated in mixed lymphocyte reactions and the delayed type hypersensitivity (DTH) murine model.ResultsUpon priming, 21 out of 377 tested miRNAs were significantly modulated in primed MSCs. We validated the up-regulation of miR-29a, miR-146a, miR-155 and the down-regulation of miR-149, miR-221 and miR-361 in additional samples of primed MSCs. We showed that miR-155 significantly reduced the proliferation of aPBMCs in vitro and inflammation in vivo, using the DTH model. Analysis of miRNA-mRNA interactions revealed miR-221 as a potential target gene that is down-regulated by miR-155 both in primed MSCs and in aPBMCs.ConclusionHere, we present evidence that miR-155 participates to the immunosuppressive function of human BM-MSCs and down-regulates the expression of miR-221 as a possible inflammatory mediator.