Properties of myelofibrosis-derived fibroblasts

Fibroblasts derived from bone marrow of patients with primary myelofibrosis and of patients with other well-differentiated myeloproliferative disorders without myelofibrosis (MPD), exhibit in vitro the same properties as fibroblasts derived from normal bone marrow. The cell density distribution, cell sedimentation rate distribution and time-dependent adherence of bone marrow fibroblast colony-forming cells (CFU-F) of MPD patients are similar to those of normals. The in vitro growth parameters, namely anchorage, serum dependence, and contact inhibition are analogous in fibroblasts derived from fibrotic and normal bone marrow. The intra- and extra-cellular distribution of fibronectin, type I, type III and type V collagens is similar in cultured marrow fibroblasts from normals, and from MPD patients with and without myelofibrosis. The plasminogen-dependent fibrinolytic activity elicited from normal and myelofibrotic marrow fibroblasts are equivalent. Moreover, marrow fibroblasts from patients with myelofibrosis do not exhibit the chromosomal abnormalities present in hematopoietic cells. These observations provide strong evidence for the absence of changes associated with neoplastic states in fibroblasts derived from fibrotic bone marrow, and support the hypothesis that myelofibrosis associated with MPD results from the abnormal interaction between hematopoietic cells and marrow collagen-producing cells, rather than from a primary disorder affecting the latter cells.