PF459 ANGELICA SINENSIS POLYSACCHARIDE MAINTAINS THE FUNCTION OF HEMATOPOIETIC STEM CELLS BY REGULATING THE TREG/TH17 RATIO AND THEREBY INDUCES ANTI‐MITOCHONDRIAL APOPTOSIS IN APLASTIC ANEMIA
Authors: R. Xu, X. Cui, S. Cui, J. Xu, X. Dong
Journal: HemaSphere (2019)

Background: Aplastic anemia (AA) is considered a bone marrow failure syndrome because it is characterized by peripheral pancytopenia and marrow hypoplasia. Several studies have confirmed that T helper (Th) cells, such as IL‐17‐producing (Th17) CD4+ T cells, play a negative role in the pathogenesis of AA (Hoyer et al., 2009), whereas regulatory T cells (Tregs) maintain immunological self‐tolerance and immunosuppression (Campbell and Koch, 2011), which play a critical role in protection of the hematopoietic function in AA (Shi et al., 2012). However, whether mitochondrial apoptosis influences hematopoietic stem cells by regulating immunity in AA remains unknown. Aims: To investigate whether mitochondrial apoptosis induced by abnormal regulatory T cell (Treg)/Th17 cell ratios could be corrected by Angelica sinensis polysaccharide (ASP) in a murine model of aplastic anemia (AA). Methods: Abnormal mitochondrial function and mitochondrial apoptosis were first confirmed in AA patients. In the in vivo experiment, ICR mice were randomly divided into five groups: normal control group, AA model control group and three groups treated with different doses. AA mice (the AA model control and treated groups) were treated with 60Co γ‐radiation and then administered daily intraperitoneal injections of cyclophosphamide and chloramphenicol for 3 days. The mice in the various groups were fed saline or ASP for 2 weeks. To confirm that the AA model was successfully established, blood cells and bone marrow cells were obtained from the various groups of animals on day 14, the peripheral blood cell and bone marrow nucleated cells (BMNCs) counts were counted, and a marrow biopsy was performed. The Lin–Sca‐1+c‐Kit+ (LSK) cell populations were then sorted from the bone marrow cells of AA mice and cultured in medium for testing. The mitochondrial function, including the outer membrane integrity and mitochondrial membrane potential (MMP), was tested. The accumulation of reactive oxygen species (ROS), the degree of apoptosis, and the levels of mitochondria‐associated apoptosis‐related proteins, including the Bcl‐2/Bax ratio, the caspase‐3, caspase‐9 and p‐P38/P38 levels, were measured in the groups of AA mice. The Treg/Th17 cell ratio was also tested. Results: The numbers of peripheral blood cells and BMNCs and the hematopoietic tissue area in the bone marrow biopsies from AA mice were notably decreased ( P &lt; 0.05), which indicated successful establishment of the AA mouse model. The mice treated with the medium dose of ASP for 14 days showed increased WBC, RBC, PLT and BMNC counts compared with the mice in the AA group mice. The data showed that ASP decreased damage to the mitochondrial outer membrane, improved the stabilization of the mitochondrial membrane, corrected the abnormal levels of ROS and mitochondrial‐associated apoptosis proteins, including the Bcl‐2/Bax ratio and caspase‐3 and caspase‐9 expression, in the AA mice. The changes to the p‐P38/P38 and Treg/Th17 ratios induced by AA were also recovered by the medium dose of ASP. Summary/Conclusion: The indicators of mitochondrial apoptosis and the Treg/Th17 cell ratio in the ASP‐treated group, particularly the medium‐dose group, were significantly better than those in the AA group, which indicates that ASP might induce anti‐mitochondrial apoptosis to restore the function of hematopoietic stem cells by suppressing abnormal T‐cell immunity in AA. image