The relationship of the active and latent forms of TGF-β1 with marrow fibrosis in essential thrombocythemia and primary myelofibrosis.

The aim of this study was to perform an immunohistochemical analysis from 100 megakaryocytes per sample, analyzing positivity and intensity levels of anti-LAP human TGF-β1 (or Latent TGF-β1) and anti-TGF-β1 (or Active TGF-β1) antibodies from 18 essential thrombocythemia (ET) and 38 primary myelofibrosis (PMF) patients (being 19 pre-fibrotic and 19 fibrotic). Six bone marrow donor biopsies were used as controls. Fibrosis in bone marrow biopsies (BMB) was evaluated according to the European Consensus. The average fibrosis grade differed between each group (P=0.001 or P=0.003). Latent TGF-β1 values differed significantly between pre-fibrotic (P=0.018) and fibrotic (P=0.031) groups when compared with the control group. The high immunoexpression level of Latent TGF-β1 in the megakaryocytes from patients with myelofibrosis, which was not observed in patients with essential thrombocythemia, may be associated with the development of bone marrow fibrosis.