Leptin-mediated proinflammatory bone marrow environment in acquired aplastic anemia.

Area of Science:

• Immunology
• Hematology
• Cell Biology

Background:

• Acquired aplastic anemia (AA) is a bone marrow failure syndrome driven by immune dysregulation.
• Enhanced adipogenesis in AA leads to fatty bone marrow, involving mesenchymal stem cells (BM-MSCs).
• Leptin, an adipokine, has known pro-inflammatory roles in autoimmune diseases, but its function in AA is unclear.

Purpose of the Study:

• To investigate the role and mechanism of leptin in the hyperimmune state of acquired aplastic anemia.
• To determine leptin levels and its effects on T cells and associated signaling pathways in AA patients.

Main Methods:

• Quantification of leptin concentration in bone marrow (BM) from AA patients, healthy donors (HD), and myelodysplastic syndrome (MDS) patients.
• Assessment of leptin and leptin receptor expression on BM-MSCs and T cells.
• In vitro analysis of leptin's effects on T cell proliferation, activation, cytokine production (IFN-γ), and regulatory T cell differentiation.
• Detection of intracellular signaling pathways (JAK2/STAT3) in T cells exposed to leptin.

Main Results:

• Leptin concentrations were significantly higher in AA-BM compared to HD-BM and MDS-BM.
• AA-derived mesenchymal stem cells (AA-MSCs) expressed high levels of leptin during adipogenesis.
• Leptin receptor was upregulated on T cells from AA patients.
• Leptin enhanced T cell proliferation and activation, increased interferon-γ production, and inhibited regulatory T cell (CD4+Foxp3+) development.
• Leptin activated the JAK2/STAT3 signaling pathway in T cells from AA patients.

Conclusions:

• Elevated leptin in AA bone marrow contributes to a pro-inflammatory environment by promoting T cell activation and function.
• Leptin's pro-inflammatory effects in AA are mediated through the JAK2/STAT3 signaling pathway.
• These findings highlight leptin as a potential therapeutic target in acquired aplastic anemia.