Bone marrow expression and plasma concentration of basic fibroblast growth factor in patients with idiopathic thrombocytopenic purpura

Background. Basic fibroblast growth factor (bFGF) is one of main regulators of hematopoiesis, including megakaryopoiesis. The main bone marrow finding of patients with idiopathic thrombocytopenic purpura (ITP) is increased megakaryopoiesis. The purposes of this study were to evaluate the change in the production of bFGF and its expression pattern in the bone marrow of patients with ITP and to correlate these characteristics with the plasma concentration of bFGF. Methods. Paraffin sections of bone marrow biopsies from 17 patients with ITP and 5 healthy control subjects without pathologic alterations were investigated by immunohistochemistry for bFGF and CD68. bFGF messenger RNA (mRNA) in situ hybridization was performed with bone marrow biopsy sections, and the plasma levels of bFGF were evaluated by enzyme immunoassay. Results. bFGF was expressed strongly in stromal cells and weakly in megakaryocytes. The density of bFGF-expressing stromal cells was decreased in 70% (12/17) of the patients with ITP but in none of the control subjects. The numbers of stromal cells and the cellular distributions of bFGF mRNA in patients with ITP were similar to those of the control subjects. The plasma levels of bFGF were significantly lower in almost all of the ITP patients relative to those of the control group. Conclusions. The results indicate that the concentrations of bFGF in plasma and bone marrow stromal cells in ITP cases are decreased, whereas the production of bFGF remains unchanged. Although the mechanism of low cellular and plasma concentrations of bFGF needs to be elucidated, these findings may complement the serologic and morphologic diagnosis of ITP.