Aplastic anemia (AA) is characterized by a reduced number of hematopoietic stem cells and fatty replacement in the bone marrow. Transcriptional factor GATA-2 plays several important roles in both hematopoiesis and adipogenesis. Decreased levels of GATA-2 compromise the proliferation and survival of hematopoietic stem cells. GATA-2 suppresses adipocyte differentiation through direct inhibition of adipogenic factors, including peroxisome proliferator-activated receptor-γ (PPARγ). Previous studies have shown that expression of GATA-2 is decreased in marrow CD34-positive cells in AA. To elucidate the mechanisms of fatty marrow replacement, we evaluated the mRNA expression for GATA-2 and PPARγ in mesenchymal stem cells (MSCs) from patients with AA by quantitative real-time polymerase chain reaction. GATA-2 expression by MSCs from AA patients was significantly lower than in normal subjects. Conversely, expression of PPARγ was significantly higher in AA patients. Western blot analysis demonstrated that protein levels of GATA-2 were lower in AA patients than those in normal subjects. Moreover, incubation with interferon-γ induced downregulation of GATA-2 levels in MSCs from normal subjects. These findings indicate that fatty marrow replacement in AA patients can be explained by downregulation of GATA-2 and overexpression of PPARγ in MSCs. Decreased expression of GATA-2 might be responsible for the pathogenesis and development of the clinical features of the disease.
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