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

Abstract

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-γ 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 (HE) 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-γ), 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-γ in EAE mice, but infusion with C3H10-B7H4 cells only slightly reduced pro-inflammatory cytokine responses in mice. Taken together, these data indicated that B7-H4 was important for the immune characteristics and immunomodulatory capacity of mouse MSCs. B7-H4 decreased Th1/Th17 responses in EAE mice. This is the first report on the role and possible mechanism of B7-H4 in the protection of MSCs against MOG-induced EAE in mice. These findings may provide a new avenue and target molecule in MSC-based therapy for autoimmune diseases in the central nervous system, such as multiple sclerosis and neuromyelitis optica spectrum disorder.

Keywords

• b7-h4
• mesenchymal stem cell
• experimental autoimmune encephalomyelitis
• immunomodulation