P1002: ANTI-FIBROTIC ACTIVITY OF BMP2 IN BONE MARROW-DERIVED MESENCHYMAL STROMAL CELLS OF MYELOPROLIFERATIVE NEOPLASMS

Abstract

Background: Myeloproliferative neoplasms (MPN) are clonal hematopoietic disorders that include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Bone marrow fibrosis (BMF) is a shared feature of all MPN, although it is most pronounced in PMF and represents a major diagnostic criteria. Studies suggest a correlation between the grade of BMF and prognosis of MPN, with more fibrosis associated with worse outcome. A large body of evidence has suggested that transforming growth factor beta (TGF-β) is among the most prominent inducers of fibrotic processes. Bone morphogenetic proteins (BMPs) are major regulators of cell fate in tissue homeostasis. In MPN, bone marrow-derived mesenchymal stromal cells (BM-MSC) are identified as a major cellular source of fibrosis, but exact molecular mechanism involved have not been identified so far. Aims: In addition to apoptosis and prolifration, we analyzed the effect of BMP2 and TGF- β / SMAD signaling pathway on the fibrotic phenotype of BM-MSC isolated from MPN patients and healthy donors. Methods: Bone marrow aspirates from 5 newly diagnosed MPN patients (3 PMF and 2 PV patients) and 3 healthy donors were analyzed by immunofluorescence expression of fibronectin and alpha smooth muscle Actin (αSMA), after treatment with TGF-β and / or BMP2. Using immunocytochemistry, we analyzed HEL 92.1.7 cells with a homozygous expression of JAK2V617F for proliferation (Ki67) and apoptosis (ssDNA) during exposure to BMP2 and selective BMP signaling inhibitor LDN-193189. Results: Our results showed that TGF-β significantly increased fibronectin expression, in contrast to BMP2, in BM-MSC of healthy donors. Also, the joint treatment of TGF-β and BMP2 reduced the level of fibronectin expression relative to TGF-β. In addition, TGF-β increased αSMA expression in BM-MSC from healthy donors. In contrast, BMP2 reduces the expression of αSMA and fibronectin in BM-MSC of healthy donors.BMP2 significantly reduced fibronectin expression in BM-MSC compared to untreated cells of patients with MPN. BMP2 dose dependently and significantly (p<0.01) increased the proliferation of HEL 92.1.7 cells, while the BMP signaling inhibitor LDN-193189 also demonstrated dose dependence in stimulation of proliferation (p<0.001). Apoptosis of HEL 92.1.7 cells was slightly affected by BMP2 and LDN-193189. Summary/Conclusion: Our results show that BMP2 has anti-fibrotic activity that is antagonistic to TGF-β. This indicate that BMP2 may modify the TGF-β signaling pathway.