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

TGFβ1 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 TGFβ1 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 TGFβ1 than healthy controls, with a balance bioactive/total TGFβ1 in favour of the latter. The balance between bioactive/total TGFβ1 in the BM plasma of patients mirrored that of PB, with most of TGFβ1 in the latent form; on the contrary, in the BM plasma of healthy controls most of the TGFβ1 was in the bioactive form. In conclusion, increased plasma levels of TGFβ1 and an altered ratio bioactive/total TGFβ1 in BM are not peculiar of patients with PMF suggesting that, whether altered levels of TGFβ1 have a role in myelofibrosis, this may not be related to the induction of BM fibrosis.