Negative costimulatory molecule B7-H4 mediates protective effect of mesenchymal stem cells on experimental autoimmune encephalomyelitis

Our previous study has shown that the negative co-stimulatory molecule B7-H4 is constitutively expressed on human bone marrow-derived mesenchymal stem cells (MSCs) and mediates their immunomodulatory effect on T cells in vitro. However, whether B7-H4 on MSCs can be responsible for their immunomodulation in vivo has not been clarified. The present study investigated the immunomodulatory role and mechanism of B7-H4 on mouse mesenchymal stem cell (MSCs) in the development of experimental autoimmune encephalomyelitis (EAE). Murine MSC C3H/10T1/2 (C3H10) cells were transfected with B7-H4-specific shRNA to silence B7-H4 expression (C3H10-B7H4). The effects of C3H10-B7H4 cells on splenocyte proliferation and cell cycling as well as cytokine responses were examined.We found that B7-H4 silencing mitigated the immune-inhibitory effect of C3H10 cells on PHA-stimulated splenocyte activation and proliferation as well as IL-2, IL-17 and IFN-gamma responses. Female C57BL/6 mice were injected with myelin oligodendrocyte glycoprotein peptide (MOG35-55) to induce EAE, then infused with C3H10-B7H4, C3H10-NC (C3H10 transfected with negative control shRNA) or C3H10 cells. The pathological changes of the injured spinal cord were analyzed by hematoxylin and eosin (H&E) staining, Luxol fast blue (LFB) staining and immunofluorescence. Infusion with C3H10 or C3H10-NC, but not C3H10-B7H4 cells, dramatically slowed the development of EAE, and reduced the severity and degree of inflammatory infiltrates, demyelination, and axonal damages. The plasma levels of interleukin-2 (IL-2), IL-17, interferon-gamma (IFN-gamma), and IL-4 in the different groups of mice were examined. Infusion with C3H10 or C3H10-NC cells significantly decreased the plasma levels of IL-2, IL-17 and IFN-gamma in EAE mice, but infusion with C3H10-B7H4 cells only slightly reduced pro-inflammatory cytokine responses in mice. Taken together,