Evaluation of the bioactive and total transforming growth factor β1 levels in primary myelofibrosis

TGF beta 1 is secreted as latent protein that requires activation to become biologically active. It negatively regulates the progenitor cell growth, and favours the deposition of extra-cellular matrix in different tissues. We have studied TGF beta 1 levels in Philadelphia-negative (Ph-) myeloproliferative diseases, evaluating patients with primary myelofibrosis (PMF) that is characterized by increased numbers of circulating progenitor cells and bone marrow (BM) fibrosis, and patients with polycythemia vera (PV) or essential thrombocythemia (ET) that do not present BM fibrosis. We found that patients with PMF, PV or ET have higher peripheral blood (PB) plasma levels of both bioactive and total TGF beta 1 than healthy controls, with a balance bioactive/total TGF beta 1 in favour of the latter. The balance between bioactive/total TGF beta 1 in the BM plasma of patients mirrored that of PB, with most of TGF beta 1 in the latent form; on the contrary, in the BM plasma of healthy controls most of the TGF beta 1 was in the bioactive form. In conclusion, increased plasma levels of TGF beta 1 and an altered ratio bioactive/total TGF beta 1 in BM are not peculiar of patients with PMF suggesting that, whether altered levels of TGF beta 1 have a role in myelofibrosis, this may not be related to the induction of BM fibrosis. (C) 2010 Elsevier Ltd. All rights reserved.