Contribution of extracellular vesicles in normal hematopoiesis and hematological malignancies.

Extracellular vesicles (EVs) are lipid bilayer-enclosed microparticles that have prominent roles in the intercellular crosstalk. EVs are secreted after fusion of endosomes with the plasma membrane (exosomes) or shed from the plasma membrane (microvesicles). These microparticles modulate bone marrow microenvironment and alter differentiation and expansion of normal hematopoietic cells. EVs originated from mesenchymal stromal cells have been shown to enhance expansion of myeloid-biased hematopoietic progenitor cells. In addition, megakaryocytic microparticles stimulate differentiation of hematopoietic stem and progenitor cells into mature megakaryocytes. The ability of EVs in induction of maturation and expansion of certain hematopoietic cells has implications in transfusion medicine and in targeted therapeutic modalities. Important prerequisites for these interventions are identification the specific targets of EVs, transferred biomolecules and molecular mechanisms underlying the fate decision in the target cells. EVs are also involved in the pathogenesis and progression of hematological malignancies including acute leukemia and multiples myeloma. In the current review, we provide a summary of studies which evaluated the significance of EVs in normal hematopoiesis and hematological malignancies.