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

Different populations and sources of human mesenchymal stem cells (MSC): A comparison of adult and neonatal tissue-derived MSC

The mesenchymal stroma harbors an important population of cells that possess stem cell-like characteristics including self renewal and differentiation capacities and can be derived from a variety of different sources. These multipotent mesenchymal stem cells (MSC) can be found in nearly all tissues and are mostly located in perivascular niches. MSC have migratory abilities and can secrete protective factors and act as a primary matrix for tissue regeneration during inflammation, tissue injuries and certain cancers

Mesenchymal stem cells, autoimmunity and rheumatoid arthritis

The vast majority of literature pertaining to mesenchymal stem cells (MSC) immunomodulation has focussed on bone marrow-derived MSC that are systemically infused to alleviate inflammatory conditions. Rheumatoid arthritis (RA) is the commonest autoimmune joint disease that has witnessed significant therapeutic advances in the past decade, but remains stubbornly difficult to treat in a subset of cases. Pre-clinical research has demonstrated that bone marrow, adipose, synovial and umbilical cord-derived MSC all suppress the functions of different immune cells thus raising the possibility of new therapies for autoimmune diseases including RA. Indeed, preliminary evidence for MSC efficacy has been reported in some cases of RA and systemic lupus erythromatosis. The potential use of bone marrow-MSC (BM-MSC) for RA therapy is emerging but the use of synovial MSC (S-MSC) to suppress the exaggerated immune response within the inflamed joints remains rudimentary. Synovial fibroblasts that are likely derived from S-MSCs, also give rise to a cell-cultured progeny termed fibroblast-like synoviocytes (FLS), which are key players in the perpetuation of joint inflammation and destruction. A better understanding of the link between these cells and their biology could be a key to developing novel MSC-based strategies for therapy. The review briefly focuses on BM-MSC and gives particular attention to joint niche synovial MSC and FLS with respect to immunoregulatory potential therapy roles

Allogeneic Mesenchymal Stem Cells Can Mitigate Early, Ongoing, and Severe Graft Versus Host Disease but Require Delayed Administration for Optimal Effect.

Abstract Mesecnhymal stem cells have been observed to inhibit graft versus host disease clinically, however the timing of infusion of these cells has not been well characterized. In previous studies, we have observed MSC to rescue lethally irradiated hosts that had received sub-optimal numbers of stem cells, permit the reduction of host conditioning while establishing equal or better levels of engraftment than the combination of intensive host conditioning and untreated HSC grafts, and enable xenogeneic engraftment (rat→ mouse) suggesting that administration of MSC in combination with an allogeneic transplant significantly alters host immune responses to enhance engraftment.. These findings could only be observed if MSC were given on the same day as the bone marrow stem cells. The purpose of this study was to determine to what extent MSC might affect donor immune responses involved in GVHD and to determine the optimal timing of these effects, in order to optimize the maximal beneficial effects of allogeneic stem cell grafts engineered with MSC. Since GVHD, mediated by donor T cells, requires host antigen presentation for initiation, we tested whether the effect of MSC occurred before or after this interaction. We used an established GVHD model in which 20x 10^6 Balb/c bone marrow cells in combination with 15 x 10^6 Balb/c splenocytes were administered to lethally irradiated B6 recipients to test whether MSC (1.0 x 105) could inhibit initiation of GVHD and to what extent these cells could mitigate or abrogate ongoing GVHD. In control animals, we observed donor T cell expansion to occur in the absence of B6 host T cells with corresponding destructive effects resulting in 100% lethality by day 48. Four experimental groups (n=10 per group) were used to test MSC administration at 4 time points: 1) on day 0 following co-culture with the graft to test whether cell contact between MSC and GVHD-producing splenocytes is necessary, 2) on day 2 to test whether donor T cell exposure to host antigen is required, 3) on day 20, to test the magnitude of effect of MSC on ongoing GVHD, and 4) on day 30 in which GVHD is severe and usually irreversible. Mice were weighed twice weekly and monitored daily for survival and clinical evidence of GVHD (ruffled fur, cachexia, alopecia, and diarrhea). When compared to survival of control animals, no statistically significant effect was observed when MSC were given with the stem cell grafts on day 0. Strikingly, survival was significantly increased to 60% when given on day 2 (p=0.01, log rank test), to 50% when given on day 20 (p=0.005), and to 40% for day 30 treated animals (p=0.009). Following MSC infusion, those animals that developed signs of GVHD such as ruffled fur and alopecia had dramatic improvement of these physical findings with most surviving animals experiencing a complete reversal to normal appearing fur. The observation that no effect occurred with MSC administered at the time of bone marrow transplantation suggests that the mechanism of effect requires host antigen presentation. We conclude that optimal timing for the infusion of donor specific MSC to abrogate GVHD begins after donor T cells have encountered host antigen and can be equally effective during early, late, and severe GVHD. Clinical strategies involving the use of allogeneic stem cell grafts engineered with MSC are likely to be more powerful in overcoming GVHD if the MSC infusion is administered in a delayed fashion.</jats:p

Thinking out of the box - New approaches to controlling GVHD

Graft-versus-host disease (GVHD) remains a major limitation of allogeneic hematopoietic cell transplantation (allo-HCT). Despite major advances in the understanding of GVHD pathogenesis, standard GVHD prophylaxis regimens continue to bebased on the combination of a calcineurin inhibitor with an antimetabolite, while first line treatmentsstill relies on high-dose corticosteroids. Further, no second line treatment has emerged thus far in acute or chronic GVHD patients who failed on corticosteroids. After briefly reviewing current standards of GVHD prevention and treatment, this article will discuss recent approaches that might change GVHD prophylaxis / treatment in the next decades, with a special focus on recently developed immunoregulatory strategies based on infusion of mesenchymal stromal or regulatory T-cells, or on injection of lowdose interleukin-2

Quantification of Mesenchymal Stem Cell (MSC) Delivery to a Target Site Using In Vivo Confocal Microscopy

The ability to deliver cells to appropriate target tissues is a prerequisite for successful cell-based therapy. To optimize cell therapy it is therefore necessary to develop a robust method of in vivo cell delivery quantification. Here we examine Mesenchymal Stem Cells (MSCs) labeled with a series of 4 membrane dyes from which we select the optimal dye combination for pair-wise comparisons of delivery to inflamed tissue in the mouse ear using confocal fluorescence imaging. The use of an optimized dye pair for simultaneous tracking of two cell populations in the same animal enables quantification of a test population that is referenced to an internal control population, thereby eliminating intra-subject variations and variations in injected cell numbers. Consistent results were obtained even when the administered cell number varied by more than an order of magnitude, demonstrating an ability to neutralize one of the largest sources of in vivo experimental error and to greatly reduce the number of cells required to evaluate cell delivery. With this method, we are able to show a small but significant increase in the delivery of cytokine pre-treated MSCs (TNF-α & IFN-γ) compared to control MSCs. Our results suggest future directions for screening cell strategies using our in vivo cell delivery assay, which may be useful to develop methods to maximize cell therapeutic potential.Sanofi Aventis (Firm