Mesenchymal stem cells (MSCs) have been shown to migrate to various tissues. There is little information on the fate and potential therapeutic efficacy of the reinfusion of MSCs following total body irradiation (TBI). We addressed this question using human MSC (hMSCs) infused to nonobese diabetic/ severe combined immunodeficient (NOD/SCID) mice submitted to TBI. Further, we tested the impact of additional local irradiation (ALI) superimposed to TBI, as a model of accidental irradiation. NOD/SCID mice were transplanted with hMSCs. Group 1 was not irradiated before receiving hMSC infusion. Group 2 received only TBI at a dose of 3.5 Gy, group 3 received local irradiation to the abdomen at a dose of 4.5 Gy in addition to TBI, and group 4 received local irradiation to the leg at 26.5 Gy in addition to TBI. Fifteen days after irradiation, quantitative and spatial distribution of the hMSCs were studied. Histological analysis of mouse tissues confirmed the presence of radio-induced lesions in the irradiated fields. Following their infusion into nonirradiated animals, hMSCs homed at a very low level to various tissues (lung, bone marrow, and muscles) and no significant engraftment was found in other organs. TBI induced an increase of engraftment levels of hMSCs in the brain, heart, bone marrow, and muscles. Abdominal irradiation (AI) as compared with leg irradiation (LI) increased hMSC engraftment in the exposed area (the gut, liver, and spleen). Hind LI as compared with AI increased hMSC engraftment in the exposed area (skin, quadriceps, and muscles). An increase of hMSC engraftment in organs outside the fields of the ALI was also observed. Conversely, following LI, hMSC engraftment was increased in the brain as compared with AI. This study shows that engraftment of hMSCs in NOD/ SCID mice with significantly increased in response to tissue injuries following TBI with or without ALI. ALI induced an increase of the level of engraftment at sites outside the local irradiation field, thus suggesting a distant (abscopal) effect of radiation damage. This work supports the use of MSCs to repair damaged normal tissues following accidental irradiation and possibly in

This is the first evidence of expanded MSCs homing in numerous tissues following a severe multi-organ injury in primates. Localization of the transduced MSCs correlated to the severity and geometry of irradiation. A repair process was observed in various tissues. The plasticity potential of the MSCs and their contribution to the repair process in vivo remains to be studied.

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.

The therapeutic management of severe radiation burns remains a challenging issue. Conventional surgical treatment (excision and skin autograft or rotation flap) often fails to prevent unpredictable and uncontrolled extension of the radiation necrotic process. We report here an innovative therapeutic strategy applied to the victim of a radiation accident (December 15, 2005) with an iridium gammagraphy radioactive source (192Ir, 3.3 TBq). The approach combined numerical dosimetry-guided surgery with cellular therapy using mesenchymal stem cells. A very severe buttock radiation burn (2000 Gy at the center of the skin surface lesion) of a 27-year-old Chilean victim was widely excised (10 cm in diameter) using a physical and anatomical dose reconstruction in order to better define the limit of the surgical excision in apparently healthy tissues. A secondary extension of the radiation necrosis led to a new excision of fibronecrotic tissues associated with a local cellular therapy using autologous expanded mesenchymal stem cells as a source of trophic factors to promote tissue regeneration. Bone marrow-derived mesenchymal stem cells were expanded according to a clinical-grade technique using closed culture devices and serum-free medium enriched in human platelet lysate. The clinical evolution (radiation pain and healing progression) was favorable and no recurrence of radiation inflammatory waves was observed during the 11 month patient's follow-up. This novel multidisciplinary therapeutic approach combining physical techniques, surgical procedures and cellular therapy with adult stem cells may be of clinical relevance for improving the medical management of severe localized irradiations. It may open new prospects in the field of radiotherapy complications.

Mesenchymal stem cells (MSC) inhibit the response of allogeneic T lymphocytes in culture. Because the mechanisms of this effect may differ according to the existence of cell contact, we investigated the differences in gene expression of inhibitory molecules during MSC-T lymphocyte coculture when cell contact does and does not occur. Human MSC and T lymphocytes were cultured together in standard and transwell cultures. MSC gene expression was analyzed by semiquantitative real-time RT-PCR. MSC elicited a high dose-dependent inhibition of T lymphocytes in cultures with cell contact, but inhibition occurred even without cell contact. In both cases, we observed significant upregulation of IDO, LIF, and HLA-G, along with downregulation of HGF and SDF1. In cultures with cell contact, IL-10 and TGF-β transcripts were expressed in a significantly higher level than in cultures without this contact. Furthermore, in the latter, the increased inhibition of T-cell proliferation was positively correlated with IDO gene expression and negatively correlated with SDF1 gene expression. MSC appear to induce T-cell tolerance by two distinct mechanisms. The first of these, which does not require cell contact, induces expression of the tolerogenic genes IDO, LIF, and HLA-G. The second mechanism, which is contact dependent, modulates IL-10 and TGF-β gene expression. These two mechanisms probably play separate roles in MSC-induced tolerance in allogeneic hematopoietic stem cell transplantation.

IntroductionRecent results have shown that cotransplantation of human ex vivo-expanded mesenchymal stem cells (MSCs) together with hematopoietic stem cells hastens hematopoietic recovery following a bone marrow (BM) transplantation in animal models [1][2][3][4] and in humans. [5][6][7] Human BM contains 2 cell compartments, the hematopoietic cell compartment and the stromal cell compartment, which constitute MSCs. 8,9 MSCs are able to give rise to multiple mesodermal tissue types, including bone, cartilage, tendon, muscles, cardiomyocytes, fat, and brain, 10-16 and a marrow stromal connective tissue that supports the differentiation of hematopoietic stem cells (HSCs). 17,18 However, MSCs are heterogeneous, and little is known on the role of MSC subsets in the hematopoietic engraftment support and in their homing in various tissues. 19 Stro-1 antigen is present on fibroblast colony-forming unit (CFU-F) cells in adult human BM and potentially defines a MSC precursor subpopulation. [20][21][22] The aim of the present study was to evaluate the role of ex vivo-expanded Stro-1 ϩ and Stro-1 Ϫ MSCs on engraftment of human CD34 ϩ cord blood cells in nonobese diabetic/ severe combined immunodeficiency (NOD/SCID) mice. Our data showed that the levels of human hematopoietic engraftment (as assessed by the presence of CD45, CD34, CD19, and CD11b cells) in the blood, spleen, and mouse BM were higher when Stro-1 Ϫ -derived cells were coinfused with CD34 ϩ cells than when Stro-1 ϩ -derived cells were used.In a second step, we investigated the homing of expanded Stro-1 ϩ and Stro-1 Ϫ cells (infused without CD34 ϩ cells) in BM, spleen, liver, brain, heart, lungs, kidneys, and muscles of NOD/ SCID mice. Eight-week-old NOD/SCID mice received 3.5 Gy irradiation, and 24 hours later the cells were infused. We analyzed the homing of cells by polymerase chain reaction (PCR) quantitation of DNA of human ␤-globin. Results showed that the DNA amount from expanded Stro-1 ϩ cells was higher than that of expanded Stro-1 Ϫ cells in spleen (ϫ 8), muscles (ϫ 6), BM (ϫ 2), liver (ϫ 1.5), and kidneys (ϫ 1.5). No significant difference was observed in brain, while more Stro-1 Ϫ than Stro-1 ϩ cell DNA was found in lungs (ϫ 3.5).In conclusion, expanded Stro-1 ϩ cells better migrated than expanded Stro-1 Ϫ cells in most mouse tissues. This indicated that Stro-1 ϩ cells would be potentially a good vector to bring specific therapeutic genes into tissues. To test this hypothesis, we infused into NOD/SCID mice expanded Stro-1 ϩ cells transfected with an enhanced green fluorescent protein (eGFP) gene. The specific eGFP DNA was found in every investigated tissue-namely, BM, liver, brain, heart, spleen, kidneys, muscles, and lungs. Patients, materials, and methods Collection and isolation of CD34 ؉ cells from human umbilical cord blood (hUCB)Human umbilical cord blood (hUCB) samples were obtained from full-term deliveries after informed consent of the mother and were used in accordance with the procedures approved by the human experimentation and ethics com...

The online version of this article has a Supplementary Appendix. BackgroundHuman induced pluripotent stem cells offer perspectives for cell therapy and research models for diseases. We applied this approach to the normal and pathological erythroid differentiation model by establishing induced pluripotent stem cells from normal and homozygous sickle cell disease donors. Design and MethodsWe addressed the question as to whether these cells can reach complete erythroid terminal maturation notably with a complete switch from fetal to adult hemoglobin. Sickle cell disease induced pluripotent stem cells were differentiated in vitro into red blood cells and characterized for their terminal maturation in terms of hemoglobin content, oxygen transport capacity, deformability, sickling and adherence. Nucleated erythroblast populations generated from normal and pathological induced pluripotent stem cells were then injected into non-obese diabetic severe combined immunodeficiency mice to follow the in vivo hemoglobin maturation. ResultsWe observed that in vitro erythroid differentiation results in predominance of fetal hemoglobin which rescues the functionality of red blood cells in the pathological model of sickle cell disease. We observed, in vivo, the switch from fetal to adult hemoglobin after infusion of nucleated erythroid precursors derived from either normal or pathological induced pluripotent stem cells into mice. ConclusionsThese results demonstrate that human induced pluripotent stem cells: i) can achieve complete terminal erythroid maturation, in vitro in terms of nucleus expulsion and in vivo in terms of hemoglobin maturation; and ii) open the way to generation of functionally corrected red blood cells from sickle cell disease induced pluripotent stem cells, without any genetic modification or drug treatment. ABSTRACT© F e r r a t a S t o r t i F o u n d a t i o n

Fibrosis is the endpoint of many chronic inflammatory diseases and is defined by an abnormal accumulation of extracellular matrix components. Despite its slow progression, it leads to organ malfunction. Fibrosis can affect almost any tissue. Due to its high frequency, in particular in the heart, lungs, liver, and kidneys, many studies have been conducted to find satisfactory treatments. Despite these efforts, current fibrosis management therapies either are insufficiently effective or induce severe adverse effects. In the light of these facts, innovative experimental therapies are being investigated. Among these, cell therapy is regarded as one of the best candidates. In particular, mesenchymal stromal cells (MSCs) have great potential in the treatment of inflammatory diseases. The value of their immunomodulatory effects and their ability to act on profibrotic factors such as oxidative stress, hypoxia, and the transforming growth factor-β1 pathway has already been highlighted in preclinical and clinical studies. Furthermore, their propensity to act depending on the microenvironment surrounding them enhances their curative properties. In this paper, we review a large range of studies addressing the use of MSCs in the treatment of fibrotic diseases. The results reported here suggest that MSCs have antifibrotic potential for several organs.