Bone marrow stroma in childhood myelodysplastic syndrome: composition, ability to sustain hematopoiesis in vitro, and altered gene expression.

We studied bone marrow stromal cell cultures from patients with childhood myelodysplastic syndromes (MDS, refractory anemia with excess of blasts, RAEB) and from matched normal donors. Stromal cell monolayers were characterized as myofibroblasts by the expression of smooth muscle alpha-actin, collagen IV, laminin and fibronectin. When normal cord blood cells were plated onto myelodysplastic stromas, a pathologic cell differentiation was observed, indicating altered myelosupportive properties. cDNA array analysis showed that patient stromas expressed increased levels of thrombospondin-1, collagen-I alpha2-chain, osteoblast-specific factor-2 and osteonectin, indicating the presence of increased osteoblast content, as confirmed by enhanced alkaline phosphatase synthesis. Alterations in the myelodysplastic stroma environment might contribute to abnormal hematopoiesis in this pathology.