Guangyou Wang

Administration of bone marrow stromal cells ameliorates experimental autoimmune myasthenia gravis by altering the balance of Th1/Th2/Th17/Treg cell subsets through the secretion of TGF-β

Bone marrow stromal cells (BMSCs) are strong candidates for cell therapy against human autoimmune diseases. Intravenous administration of syngenic BMSCs to EAMG-model rats effectively ameliorated the disease, partially through a TGF-beta-dependent mechanism. The proliferative ability of T or B cells from EAMG rats was inhibited by BMSCs at proper cocultured ratios. And the imbalance of Th1, Th2, Th17 and Treg cell subsets accompanied with the development of EAMG was corrected by the administration of BMSCs. These results provide further insights into the pathogenesis of MG, EAMG, and other immune-mediated diseases, and support a potential role for BMSCs in their treatment.

Disequilibrium of T helper type 1, 2 and 17 cells and regulatory T cells during the development of experimental autoimmune myasthenia gravis

Experimental autoimmune myasthenia gravis (EAMG), an animal model of myasthenia gravis (MG), is a rare organ‐specific autoimmune disease targeting the autoantigen nicotinic acetylcholine receptor (AChR). We show here that the balance of T helper type 1 (Th1), Th2, Th17 and regulatory T (Treg) subsets of CD4+ helper T cells were redistributed during the development of EAMG and that the interleukin‐17 (IL‐17) cytokine is involved in this disease. The ratio of Th17 cells changed most notably with disease progression accompanied by an up‐regulated level of IL‐17. Moreover, the proliferative ability of AChR peptide‐specific T cells and the anti‐AChR antibody‐secreting cells increased when stimulated by IL‐17 in vitro. These findings suggested that the disequilibrium of the CD4+ helper T‐cell subsets could promote the development of EAMG, and the pathogenic mechanism by which Th17 cells drives autoimmune responses by secreting cytokine IL‐17 provides a new target for myasthenia gravis therapy.

IL-17 potentiates neuronal injury induced by oxygen–glucose deprivation and affects neuronal IL-17 receptor expression

Interleukin-17 (IL-17) is active in a variety of brain injuries, including ischemia. The objective of this study was to test the hypothesis that IL-17 potentiates neuronal injury after stroke. Increased expression of IL-17 and IL-17 receptor (IL-17R) in serum and cortex was evaluated by ELISA, RT-PCR and immunohistochemistry. In the in vitro model of oxygen-glucose deprivation (OGD), IL-17 showed a dose-dependent effect in promoting neuronal injury through IL-17-IL-17R combination which can be blocked by IL-17R/Fc chimera. Our results demonstrated the up-regulation of IL-17 and IL-17R following permanent middle cerebral artery occlusion and suggested that they contributed to stroke outcome.

BM stromal cells ameliorate experimental autoimmune myasthenia gravis by altering the balance of Th cells through the secretion of IDO

In addition to their capacity to differentiate, BM stromal cells (BMSC) have immunosuppressive qualities that make them strong candidates for use in cell therapy against human autoimmune diseases. We studied the immunoregulatory activities of BMSC on experimental autoimmune myasthenia gravis (EAMG) in vitro and in vivo. Intravenous administration of syngenic BMSC to EAMG‐model rats on the day of their second immunization was effective in ameliorating the pathological features of the disease. In vitro, the proliferative ability of T cells or B cells from EAMG rats was inhibited when they were cocultured with BMSC at proper ratios. This inhibitory effect was at least partially dependent on the secretion of IDO. We also determined that the development of EAMG is accompanied by an imbalance among the Th1, Th2, Th17, and Treg cell subsets, and that this can be corrected by the administration of BMSC, which leads to an increase of Th2 (IL‐4) and Treg (Foxp3) cells, and a reduction of Th1 (IFN‐γ) and Th17 (IL‐17) cells, through an IDO‐dependent mechanism. These results provide further insights into the pathogenesis of MG, EAMG, and other immune‐mediated diseases, and support a potential role for BMSC in their treatment.

Murine Bone Marrow Mesenchymal Stem Cells Cause Mature Dendritic Cells to Promote T-Cell Tolerance

Bone mesenchymal stem cells (BMSC) are attractive not only in regenerative medicine, but also for the treatment of autoimmune diseases and graft‐versus‐host disease. BMSC also play a role in enabling alloantigen tolerance. An in‐depth mechanistic understanding of this phenomenon of tolerance could lead to novel cell‐based therapies for autoimmune disease. We demonstrate here that co‐culture of mature dendritic cells (DC) with BMSC in a transwell system (BMSC‐DC) downregulated expression of the maturation marker, CD83 and CD80/86 co‐stimulatory molecules on DC, while increasing their endocytic activity. This resulted in defective antigen presentation and co‐stimulatory capacity of mature DC. Functionally, BMSC‐DC have impaired T‐cell stimulatory activity in a mixed lymphocyte reaction and orchestrate a shift from predominantly pro‐inflammatory T‐helper (Th)‐1 to anti‐inflammatory Th2 cells. While the expression of MHC II, CD80 and CD86 were upregulated on BMSC co‐cultured with DC, these BMSC lacked the ability to stimulate T‐cell proliferation. Taken together, these data suggest that the interaction between BMSC and DC modulates the immunoregulatory function of these cells in a coordinated manner, effectively skewing the immune response towards T‐cell tolerance.

Reciprocal effect of mesenchymal stem cell on experimental autoimmune encephalomyelitis is mediated by transforming growth factor-β and interleukin-6

Mesenchymal stem cells (MSCs) have the ability to suppress T cell proliferation and modulate cytokine production. Recently, MSCs have been shown to ameliorate autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE), but in some cases shown to stimulate lymphocyte proliferation. So far, mechanisms through which MSCs modulate immune reactions are still undefined. In this report we demonstrate that MSCs have the capacity for either stimulating or inhibiting myelin basic protein‐specific T lymphocytes in a dose‐dependent manner and modulate antigen‐stimulated T cells to differentiate into either T helper type 17 or regulatory T cells, respectively, via pathways involving transforming growth factor‐β and interleukin‐6. These results may lead better utility of MSCs as a treatment for autoimmune disease.

Simulated microgravity promotes cellular senescence via oxidant stress in rat PC12 cells

Microgravity has a unique effect on biological organisms. Organs exposed to microgravity display cellular senescence, a change that resembles the aging process. To directly investigate the influence of simulated microgravity on neuronal original rat PC12 cells, we used a rotary cell culture system that simulates the microgravity environment on the earth. We found that simulated microgravity induced partial G1 phase arrest, upregulated senescence-associated beta-galactosidase (SA-beta-gal) activity, and activated both p53 and p16 protein pathways linked to cell senescence. The amount of reactive oxygen species (ROS) was also increased. The activity of intracellular antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), was all significantly increased at 12h after the microgravity onset, yet decreased at 96h. Furthermore, concomitant block of ROS by the antioxidant N-acetylcysteine significantly inhibited the microgravity-induced upregulation of SA-beta-gal activity. These results suggest that exposure to simulated microgravity induces cellular senescence in PC12 cells via an increased oxidant stress.

RAGE expression is up-regulated in human cerebral ischemia and pMCAO rats

To determine whether the receptor for advanced glycation endproducts (RAGE) contributes to cerebral ischemia, we evaluated RAGE expression in human cerebral ischemia and a model of permanent middle cerebral artery occlusion (pMCAO) in rats. Biopsy specimens were obtained from 12 patients with unilateral cerebral infarction. For the pMCAO model, the middle cerebral artery (MCA) of Sprague-Dawley (SD) rats was permanently occluded. Immunohistochemistry and Western blotting were used to measure RAGE expression in the ischemic hemisphere relative to the normal hemisphere. PC12 cells subjected to oxygen and glucose deprivation (OGD) were used to evaluate the role of RAGE in cell injury. As expected, cerebral ischemia patients expressed elevated levels of RAGE in the ischemic hemisphere. In 1 and 2 days pMCAO rats, levels of RAGE were higher in the ischemic hemisphere relative to the non-ischemic hemisphere, and expression was primarily located in the penumbra of the ischemic hemisphere. In PC12 cells, levels of RAGE increased after 7h of OGD culture. Notably, blockade of RAGE with a selective RAGE antibody in vitro reduced the cytotoxicity caused by OGD. The present data suggest that RAGE is up-regulated in human cerebral ischemia and pMCAO rats, suggesting a role for RAGE in brain ischemia.

TGF-β expression by allogeneic bone marrow stromal cells ameliorates diabetes in NOD mice through modulating the distribution of CD4+ T cell subsets

BMSCs could promote the regeneration of islet beta-cell, but the status of BMSCs under diabetes is still unknown. Our study verified the effect of allogeneic BMSCs (ICR) transferred into NOD mice on blood glucose and CD4+ T cells subsets function. In vivo experiment, BMSCs could decrease blood glucose, weaken lymphocytes proliferation. In vitro experiment, the distribution of CD4+ T cell subsets was changed after co-culture with BMSCs, resulting in a greater frequency of Treg cells and reduced representation of Th17 cells. After TGF-beta blockade, CD4+ T cells differentiated along a route favoring development of Th17, but not Treg cells. Thus, NOD can be treated by BMSCs which changes the distribution of CD4+ T cells, increases the number of Treg cells, and inhibits the differentiation of Th17 cells. And the positive effects of allogeneic BMSCs in the treatment of NOD mice depend on the regulation of TGF-beta secreted by BMSCs.

Activation of the adenosine A2A receptor attenuates experimental autoimmune myasthenia gravis severity

The adenosine A2A receptor (A2AR) is the major cellular adenosine receptor commonly associated with immunosuppression. Here, we investigated whether A2AR activation holds the potential for impacting the severity of experimental autoimmune myasthenia gravis (EAMG) induced following immunization of Lewis rats with the acetylcholine receptor (AChR) R97–116 peptide. This report demonstrates reduced A2AR expression by both T cells and B cells residing in spleen and lymph nodes following EAMG induction. A2AR stimulation inhibited anti‐AChR antibody production and proliferation of AChR‐specific lymphocytes in vitro. Inhibition was blocked with the A2AR antagonists or protein kinase A inhibitor. We also determined that the development of EAMG was accompanied by a T‐helper cell imbalance that could be restored following A2AR stimulation that resulted in increased Treg cell levels and a reduction in Th1‐, Th2‐, and Th17‐cell subtypes. An EAMG‐preventive treatment regimen was established that consisted of (2‐(p‐(2‐carbonylethyl)phenylethylamino)‐5‐N‐ethylcarboxamidoadenosine) (CGS21680; A2AR agonist) administration 1 day prior to EAMG induction. Administration of CGS21680 29 days post EAMG induction (therapeutic treatment) also ameliorated disease severity. We conclude that A2AR agonists may represent a new class of compounds that can be developed for use in the treatment of myasthenia gravis or other T‐cell‐ and B‐cell‐mediated autoimmune diseases.