[Mesenchymal stem cells and immunomodulation: toward new immunosuppressive strategies for the treatment of autoimmune diseases?]. / Cellules souches mésenchymateuses et immunomodulation : vers de nouvelles stratégies immunosuppressives pour le traitement des maladies auto-immunes ?

Mesenchymal stem cells (MSC) represent a population of the bone marrow microenvironment, which participates in the regulation of haematopoietic stem cells (HSC) self-renewal and differentiation. MSC are multipotent non-haematopoietic progenitors, which have been explored as a promising treatment in tissue regeneration. Both in vitro and in vivo, the MSC inhibit the T, B, NK and dendritic cell functions. Although MSC immunomodulating properties are not yet completely understood, their low immunogenic potential can be used as a therapeutic tool not only for regenerative medicine, but also for the treatment of graft-versus-host disease (GVHD) after bone marrow transplantation as well as for specific cases of severe refractory autoimmune diseases. Experimental and clinical data gave encouraging results, showing that MSC injection allowed controlling refractory GVHD, restoring bone development in children with osteogenesis imperfecta or improving heart function after myocardial infarction. Phase I-II studies are in progress in various countries to investigate the potential benefit from MSC due to their immunosuppressive properties, as an adjunctive therapy for severe refractory autoimmune disease.

Differentiation potential of human muscle-derived cells towards chondrogenic phenotype in alginate beads culture.

OBJECTIVE: The aim of this study was to evaluate the differentiation potential of two populations of muscle-derived cells (CD56- and CD56+) towards chondrogenic phenotype in alginate beads culture and to compare the effect of transforming growth factor beta 1 (TGFbeta1) on the differentiation process in these populations. METHODS: Muscle CD56- and CD56+ cells were cultured in alginate beads, in a chondrogenic medium, containing or not TGFbeta1 (10 ng/ml). Cultures were maintained for 3, 7, 14 or 21 days in a humidified culture incubator. At harvest, one culture of each set was fixed for alcian blue staining and aggrecan detection. The steady-state level of matrix macromolecules mRNA was assessed by real-time polymerase chain reaction (PCR). Protein detection was performed by western-blot analysis. The binding activity of nuclear extracts to Cbfa1 DNA sequence was also evaluated by electrophoretic mobility shift assays (EMSA). RESULTS: Chondrogenic differentiation of both CD56+ and CD56- muscle-derived cells was improved in alginate scaffold, even without growth factor, as suggested by increased chondrogenesis markers expression during the culture. Furthermore, TGFbeta1 enhanced the differentiation process and allowed to maintain a high expression of markers of mature chondrocytes. Of importance, the combination of alginate and TGFbeta1 treatment resulted in a further down-regulation of collagen type I and type X, as well as Cbfa1 both expression and binding activity. CONCLUSIONS: Thus, alginate scaffold and chondrogenic medium are sufficient to lead both populations CD56+ and CD56- towards chondrogenic differentiation. Moreover, TGFbeta1 enhances this process and allows to maintain the chondrogenic phenotype by inhibiting terminal differentiation, particularly for CD56- cells.

Phenotypical and functional characteristics of in vitro expanded bone marrow mesenchymal stem cells from patients with systemic sclerosis.

BACKGROUND: Mesenchymal stem cells (MSCs) have a potential immunomodulatory role in autoimmune disease; however, the qualitative properties and haematopoietic support capacity of MSCs derived from patients with autoimmune disease is unclear. OBJECTIVES: To further characterise phenotypically and functionally bone marrow (BM)-derived MSCs from patients with systemic sclerosis (SSc). METHODS: Key parameters of BM-derived MSC function and phenotype were assessed in 12 patients with SSc and compared with 13 healthy normal controls. The parameters included the ability to: form colony-forming unit fibroblasts (CFU-F), differentiate along the adipogenic and osteogenic lineages, express cell surface antigens defining the MSCs population, support normal haematopoiesis and suppress in vitro lymphocyte proliferation induced by either anti-CD3epsilon plus anti-CD28 monoclonal antibodies or the mixed lymphocyte reaction. RESULTS: SSc MSCs were shown to have a similar characteristic phenotype, capacities to form CFU-F and to differentiate along adipogenic and osteogenic lineages as those of healthy donor MSCs. The ability of SSc MSCs to support long-term haematopoiesis was also identical to that of controls. Both healthy donor and SSc BM MSCs reduced the proliferation of autologous and allogeneic peripheral blood mononuclear cells in a cell number dependent fashion. CONCLUSIONS: These results show that BM-derived MSCs from patients with SSc under the described culture conditions exhibit the same phenotypic, proliferative, differentiation potential and immunosuppressive properties as their healthy counterparts and could therefore be considered in an autologous setting. Further studies are needed to ensure the quality and safety of large-scale expansion of patient MSCs prior to their potential use in clinical trials.

Phenotypic and functional characterization of bone marrow mesenchymal stem cells derived from patients with multiple myeloma.

Multiple myeloma (MM) is a B-cell neoplasia caused by the proliferation of clonal plasma cells, primarily in the bone marrow (BM). The role of the BM microenvironment in the pathogenesis of the disease has been demonstrated, especially for the survival and growth of the myeloma plasma cells. Functional characterization of the major component of the BM microenvironment, namely the recently characterized mesenchymal stem cells (MSCs), was never performed in MM. Based on a series of 61 consecutive patients, we evaluated the ability of MSCs derived from myeloma patients to differentiate into adipocytes and osteocytes, inhibit T-cell functions, and support normal hematopoiesis. MSCs phenotypic characterization and quantification of interleukin-6 (IL-6) secretion were also performed. As compared to normal MSCs, MSCs from MM patients exhibited normal phenotype, differentiation capacity and long-term hematopoietic support, but showed reduced efficiency to inhibit T-cell proliferation and produced abnormally high amounts of IL-6. Importantly, these characteristics were observed in the absence of any detectable tumor plasma cell. Chromosomal analysis revealed that MM patients MSCs were devoid of chromosomal clonal markers identified in plasma cells. MM MSCs present abnormal features that may participate in the pathogenesis of MM.