Expression data of human mesenchymal stromal cells isolated from bone marrow of ML-DS, AMKL patients and HD

Bone marrow fibrosis (BMF) is a rare complication in acute leukemia. In pediatrics, it predominantly occurs in acute megakaryoblastic leukemia (AMKL) and here especially in patients with trisomy 21, called myeloid leukemia in Down syndrome (ML-DS). Defects in mesenchymal stromal cells (MSCs) and cytokines specifically released by the myeloid blasts are the main drivers of fibrosis in the bone marrow niche (BMN). In order to determine which factors are necessary/sufficient for the BMF, we first established MSCs from pediatric patients with AMKL and ML-DS. Healthy donor (HD) control MSCs were established from children and adolescents ≤18 years of age. Steady-state analyses of the MSCs revealed that patient-derived MSCs exhibited decreased adipogenic differentiation potential, enrichment of proliferation-associated genes and upregulation of the oncofetal protein IF2B3. TGFB1 exposure in vitro promoted early profibrotic changes in all three MSC entities. To study BMF induction for longer periods of time, we created an in vivo humanized artificial BMN in immunodeficient mice. Injection of AMKL blasts as producers of TGFB1 specifically induced fibrosis grade I/II in a dose-dependent fashion, thus strongly suggesting TGFB1 excess to be sufficient for BMF. Our in vivo BMF model will be instrumental to specifically prevent the BMF and to identify potentially druggable target genes.

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