P1353: exploring a novel treatment strategy for acquired aplastic anemia targeting ppar signaling pathway.

Topic: 23. Hematopoiesis, stem cells and microenvironment Background: Acquired aplastic anemia (AA) is one typical type of bone marrow failure disease characterized by pancytopenia in the peripheral blood and hypocellular hematopoiesis in the bone marrow (BM), which is largely resulted from over-activated CD8+ T lymphocytes attack. With the course of AA, the red bone marrow has been gradually replaced by bone marrow adipocytes (BMAs) differentiated from bone marrow-derived mesenchymal stem cells, which is called bone marrow adiposity. The bone marrow adipocytes can secret a wide range of adipokines, such as leptin, adiponectin, IL-6 and tumor necrosis factor alpha (TNF-α), which can primarily compromise the hematopoiesis according to established literature. Peroxisome proliferator activated receptor gamma (PPAR γ) is a kind of transcription factor associated with mature adipocytes differentiation, which could activate lipoprotein lipase (LPL) to accumulate the deposition of fat. Aims: Exploring a novel treatment strategy for AA from the perspective of inhibiting the adipogenesis in the bone marrow. Methods: In the current study, all female recipient mice (B6D2F1, n=20) were divided into four groups: Rapa (n=5), CsA (n=5), AA(n=5), normal control (n=5). We established an immune-mediated mouse model for AA via the combination of Cesium-137 γ Rays of 4.5Gy and mixed allogeneic lymphocytes suspension of spleen and thymus of donor female mice (C57BL/6J, n=5) injected intraperitoneally within 4-6 hours. Secondly, we injected intraperitoneally rapamycin (Rapa) at a dose of 2mg/kg/d daily for 13 days or cyclosporine A(CsA) at a dose of 25mg/kg/d daily for 10 days one hours later. Furthermore, we collected the bone marrow mononuclear cells (BMMNCs) of AA and normal group 12 days later to perform the untargeted lipidomics. At the same time, we collected the peripheral blood to detect the blood cell counts of four groups and commit the hematoxylin-eosin (HE) staining for the bone marrow of femurs in four groups. Besides, we detected the mRNA relative expression level and protein translation of adipocyte differentiation-related genes PPAR γ and LPL in BMMNCs in four groups using qRT-PCR and Western Blotting. Results: We successfully established a mouse model of AA characterized by defective three-lineage hematopoiesis in peripheral blood and increased bone marrow adipocytes (Fig.1b). The untargeted lipidomics revealed that PPAR signaling pathway plays an important role in the process of adipogenesis (Fig.1a). The films of HE staining indicated that rapamycin and cyclosporine A contribute to decrease BMAs, however, cyclosporine A is weaker (Fig.1b). From the result of qRT-PCR, rapamycin can downregulate the expression of adipocytes differentiation-related genes PPAR γ and LPL as well as cyclosporine A(P<0.01)(Fig.1c). The Western Blotting showed an outcome in accordance with qRT-PCR (Fig.1d). Summary/Conclusion: In conclusion, the PPAR signaling pathway plays a vital role in adipogenesis of BM, and both rapamycin and cyclosporine A are involved in targeting PPAR signaling pathway and reverse the adipocytes differentiation in BM. The PPAR signaling pathway may be a novel treatment target of AA, contributing to optimize the BM microenvironment.Keywords: Aplastic anemia