Time-dependent LPS exposure commands MSC immunoplasticity through TLR4 activation leading to opposite therapeutic outcome in EAE.

BACKGROUND: Mesenchymal stem cells (MSCs) have been recognized for their regenerative and anti-inflammatory capacity which makes them very attractive to cell therapy, especially those ones to treat inflammatory and autoimmune disease. Two different immune-phenotypes have been described for MSCs depending on which Toll-like receptor (TLR) is activated. MSC1 is endowed with a pro-inflammatory phenotype following TLR4 activation with LPS. On the other hand, anti-inflammatory MSC2 is induced by the activation of TLR3 with Poly(I:C). High immunoplasticity of MSCs is a matter of concern in cell-based therapies. In this study, we investigated whether a single stimulus can induce both types of MSCs through a differential activation of TLR4 with LPS. METHODS: MSCs were activated with LPS following a short exposure of 1-h (MSCs-LPS1h) or long-time exposure for 48 h (MSCs-LPS48h), and then, we evaluated the biological response in vitro, the immunosuppressive capacity of MSCs in vitro, and the therapeutic potential of MSCs in an experimental autoimmune encephalomyelitis (EAE) mouse model. RESULTS: Our results showed that 1-h LPS exposure induced a MSC1 phenotype. Indeed, MSCs-LPS1h expressed low levels of NO/iNOS and decreased immunosuppressive capacity in vitro without therapeutic effect in the EAE model. In contrast, MSCs-LPS48h achieved a MSC2-like phenotype with significant increase in the immunosuppressive capacity on T cell proliferation in vitro, together with an improved in the therapeutic effect and higher Treg, compared to unstimulated MSCs. Furthermore, we determine through the MSCs-TLR4KO that the expression of TLR4 receptor is essential for MSCs' suppressive activity since TLR4 deletion was associated with a diminished suppressive effect in vitro and a loss of therapeutic effect in vivo. CONCLUSIONS: We demonstrate that MSCs display a high immunoplasticity commanded by a single stimulus, where LPS exposure time regulated the MSC suppressive effect leading into either an enhanced or an impairment therapeutic activity. Our results underscore the importance of phenotype conversion probably related to the TLR4 expression and activation, in the design of future clinical protocols to treat patients with inflammatory and autoimmune diseases.

The immunosuppressive signature of menstrual blood mesenchymal stem cells entails opposite effects on experimental arthritis and graft versus host diseases.

Recently, a noninvasive and highly proliferative stem cell population from menstrual blood called MenSCs has been identified. Despite their use in clinical studies, their immunomodulatory properties have not yet been investigated. In this context, we studied the immunosuppressive properties of MenSCs in comparison with the well-characterized bone marrow derived-MSCs (BM-MSCs). Using an in vitro proliferation assays, we showed that MenSCs displayed a lower suppressive effect on peripheral blood mononuclear cells and in particular on the proinflammatory CD4(+) IFN-γ(+) and CD8(+) IFNγ(+) cells than BM-MSCs. Moreover, compared to BM-MSCs, MenSCs activated with IFN-γ and IL-1ß produced lower amounts of immunosuppressive factors such as IDO, PDL-1, PGE2, and Activin A and exhibited a substantial lower expression level of IFN-γ receptor subunits. In the collagen induced arthritis model, while BM-MSCs administration resulted in a potent therapeutic effect associated with a significant decrease of proinflammatory T cell frequency in the lymph nodes, MenSCs injection did not. In contrast, in the xeno-GVHD model, only MenSCs administration significantly increased the survival of mice. This beneficial effect mediated by MenSCs was associated with a higher capacity to migrate into the intestine and liver and not to their anti-inflammatory capacities. All together our results demonstrate for the first time that the therapeutic potential of MSC in the experimental xeno-GVHD model is independent of their immunosuppressive properties. These findings should be taken into consideration for the development of safe and effective cell therapies.