Ex Vivo Induced Regulatory Human/Murine Mesenchymal Stem Cells as Immune Modulators

Abstract

Over the past decade there has been a growing interest in using mesenchymal stem cells (MSCs) as an immune-regulatory agent for prevention and treatment of various immune disorders including graft-versus-host disease (GVHD), transplanted organ rejection, and autoimmune diseases. However, the high diversity in the results from clinical trials using MSCs for such disorders emphasizes the need for MSCs to be "professionalized" ex vivo to a more defined regulatory phenotype before administering to patients. To this aim, we have established an ex vivo immunomodulatory triple combination treatment (TCT) for MSCs, using IFNc, TGFb, and kynurenine. We show that pretreated MSCs acquire an immunomodulatory phenotype, have improved regulatory functions, and upregulate the expression of inducible nitric oxide synthase, indoleamine 2,3-dioxygenase, cyclooxygenase-2 (COX2), heme oxygenase 1, leukemia inhibitory factor (LIF), and programmed death ligand 1. We define the pathway of kynurenine induced aryl hydrocarbon receptor activation in MSCs and how it contributes to the upregulation of COX2 expression and IL-6 downregulation. The combination of reduced IL-6 secretion with enhanced LIF expression leads to the inhibition of Th17 differentiation in coculture of TCT MSCs and lymphocytes. To test the immunomodulatory function of TCT MSCs in vivo, we used the cells as GVHD prophylaxis in a GVHD mouse model. TCT MSCs administration significantly decreased GVHD score and improved mouse survival. Importantly, single administration could attenuate disease symptoms for more than 3 weeks. Based on these results, we suggest considering TCT MSCs as an improved cell therapy for systemic diseases with an underlying inflammatory and immunologic etiology.

A Phase 3, Single-Arm, Prospective Study of Remestemcel-L, Ex Vivo Culture-Expanded Adult Human Mesenchymal Stromal Cells for the Treatment of Pediatric Patients Who Failed to Respond to Steroid Treatment for Acute Graft-versus-Host Disease

“…A trend for greater response was observed in aGVHD grades C and D than in grade B patients-in other words, in patients with more severe disease and higher mortality risk. This finding is consistent with a report that the potent antiinflammatory and immunosuppressive properties of mesenchymal stromal cells are induced by exposure to high levels of specific cytokines [37,38]. Further research may elucidate this hypothesis, which is consistent with our clinical findings of increased rates of OR and overall survival in the presence of more severe aGVHD as defined by risk stratification and aGVHD grade.…”

Ex vivo allotransplantation engineering: Delivery of mesenchymal stem cells prolongs rejection-free allograft survival

“…We primed BMSCs in an inflammatory environment with TNFα or IFNγ, or in reduced oxygen tension (hypoxia, 5% O 2 ), which resulted in increased immunomodulatory efficacy in vitro. These results are corroborated by recently published work from Hinden et al in which they primed MSCs with a triple cocktail of IFNγ, TNFα, and kynurenine to better attenuate graft‐versus‐host disease in a mouse model . Importantly, priming with IFNγ has been previously demonstrated to convert MSCs to an antigen presenting cell phenotype, thereby decreasing their immunomodulatory capacity.…”

Aryl Hydrocarbon Receptor–Dependent Pathways in Immune Regulation

“…MSCs have been proposed as engraftment promoter cells in bone marrow transplantation and as a therapeutic option in solid organ transplantation rejection (35). In an elegant study, Hinden et al reported that kynurenine contributed to the regulatory phenotype of MSCs through the activation of AhR, leading to suppression of IL-6, induction of leukemia inhibitory factor and activation of the EGFR-COX2 pathway, all of which contributed to the inhibition of the Th17 cells (36). Other than highlighting the potential of MSCs as transplant engraftment promoters, these results emphasize the role of kynurenine, a recognized AhR ligand (10,21), in the modulation of immune tolerance to transplants.…”