Expression profiling in exosomal miRNAs of human bone marrow stromal cells derived from myelodysplastic syndrome patients

Myelodysplastic syndromes (MDS) constitute a heterogeneous group of clonal hematological disorders characterized by the presence of peripheral cytopenias and an increased risk of transformation into acute myeloblastic leukemia (AML). These hematological disorders are complex and their origin in a clonal hematopoietic stem cell disorder is accepted. In the last few years, the importance of the bone marrow (BM) microenvironment has been highlighted. Bone marrow stromal cells (BMSCs) are a non-hematopoietic BM cell population considered to be the osteoblastic progenitors and a key component of the hematopoietic microenvironment. As usual, it was considered that intercellular communication could be achieved by direct cell-to-cell contact or the exchange of soluble factors and intercellular adhesion molecule. Recently, a new mechanism of intercellular communication based on the secretion of extracellular esicles (EVs) has been described. Such a mechanism modifies the functional properties of recipient cells by the transfer of bioactive molecules such as mRNA, proteins and micro-RNAs, among others. BMSCs play an important role in bone marrow environment. Recent evidences suggest that EVs act as a mediator of cell-cell interaction in hematologic neoplasms. To clarify the possible association between the cargo of BMSC-EVs and disease severity, we performed miRNA profiling in BMSC-EVs derived from MDS patients. Human BMSCs of elderly (68 and 72 years old) healthy donors (Normal-BMSCs) were purchased from Lonza. BMSCs from 29 patients (22 patients with MDS, and 7 with post-MDS AML), age 22~87, were obtained by classical adhesion methods after obtaining a written informed consent (IRB approval no.2684). We tentatively separated MDS patients into two groups according to the IPSS-R: low-risk group (n=13; very low to intermediate risk) and high-risk group (n=9; high and very high risk group). The extracellular vesicules (EVs) from culture medium of BMSCs were isolated by Total exosome isolation regent (Invitrogen). Total RNA from each EV fractions (2 Normal-BMSCs, 13 low-risk MDS-BMSCs, 9 high-risk MDS-BMSCs,and 7 AML-BMSCs) was extracted by the miRneasy mini kit (Qiagen). The EV-miRNA profiling was done using a TaqMan low-density array (ABI), and Student’s t-test was used to determine statistical significance for comparisons between low-risk and high-risk groups using R software.