Bone marrow mesenchymal cells from Myelodisplastic Syndromes release microvesicles that incorporate into CD34+ cells and may modify their behaviour.

The secretion of exosomes/ microvesicles (MVs) is a recently described mechanism of intercellular communication that is based on the transfer of bioactive molecules. Our hypothesis was that mesenchymal stromal cells (MSC) from myelodisplastic syndromes (MDS) patients could modify CD34+ hematopoietic progenitor cells (HPC) properties throughout MVs. The latter were isolated from MSC from MDS patients and healthy donors (HD). MVs were purified by ExoQuick-TC exosome precipitation solution or ultracentrifugation and identified by transmission electron microscopy (TEM) and flow cytometry (FC). Their Micro-RNA content was evaluated by microarrays. Incorporation of MVs into CD34+ cells was analyzed by FC and confocal microscopy (CM). Our results showed that MVs displayed the same immunophenotypic pattern and similar morphology. The content of miRNAS in the MVs from MDS and HD was significantly different. Next, MVs incorporation into HPC was observed, being highest after 24 hours of incubation. We demonstrated that MVs could modify the HPC behavior since the incubation of HPC with MVs led to gene expression modification evaluated by RT-PCR and increased cell viability by FC. In summary, we show that BM-MSC produce MVs with different cargo in MDS compared to HD. These structures can incorporate into HPC and modify their properties. In order to study the micro-RNA content of MSC-MVs from both patients and controls, a differential expression analysis of miRNAs was performed. Total RNA from MSC-derived MVs of 8 low-risk MDS and 4 HD were retrotranscribed with Megaplex™ RT Primers pool (Applied Biosystems). 384-well microfluidic cards (TaqMan® MicroRNA Array A) were loaded with retro-transcription product and PCR runs were performed on a 7900HT Fast Real-time PCR system (Applied Biosystems).