MSCs From Patients with Myelofibrosis Display a Fibrotic Phenotype

Abstract 5160

Myeloproliferative neoplasms (MPNs) are characterized by the excessive production of terminally differentiated nonlymphoid cells or platelets in the bone marrow. They represent a heterogenous group of clonal hematologic malignancies and are classified into chronic myeloid leukemia (CML), essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF) and other rarer diseases.

MPNs are often associated with extramedullary hematopoiesis and progressive hepatosplenomegaly due to displacement of hematopoietic progenitor cells from the BM to spleen and liver. Progenitor mobilization follows the enhanced deposition of extracellular matrix proteins, which can be found in the bone marrow of MPN patients.

Nonhematopoietic bone marrow stromal cells (BMSCs) and their precursors (mesenchymal stem cells) are believed to be conditioned by abundantly released growth factors from the pathological hematopoietic clone in MPNs and in turn contribute to a modified niche environment which participates in the maintenance of the malignant clone and in disease progression.

We therefore aimed at the comparative analysis of BMSCs from MPN patients (displaying myelofibrosis 0–1) and healthy donors as well as at their matrix remodelling capacity.

BMSCs from PMF patients were obtained by trephine biopsies and isolated by plastic adherence in IMDM, 20% FCS and cortisone. BMSCs from PMF patients fulfilled MSC criteria according to common consensus (Dominici et al., 2007). To compare their potential to support hemato-lymphopoiesis, we analyzed their hemato-lymphotropic cytokine transcription by RT-PCR. MSCs from MPN patients and healthy donors expressed gene transcripts for M-CSF, SDF-1, LIF, FLT3L, Oct-4, SCF, IL-6 and IL-7, suggesting no significant difference in cytokine production. However, when activated through contact with collagen I/III and embedded in three-dimensional scaffolds, MSCs from MPN-patients extensively remodelled the collagenous matrix compared to healthy donors. Under osteogenic and undifferentiated culture conditions, the extracellular matrix (ECM) production by MPN-MSC was strongly enhanced compared to MSCs from healthy controls as shown by RT-PCR and immunohistochemistry for collagen I, IV, fibronectin, laminin and osteopontin. Furthermore, MSCs from MPN patients significantly contracted and densified the collagenous matrix and the ECM deposition by MSCs from MPN patients was highly comparable to the ECM changes observed in corresponding bone punches. We therefore hypothesize that MSCs from MPN patients are primed to produce enhanced ECM proteins, whereas their capacity to support hematopoiesis seems to be unchanged.