[Biological characteristics of Microvesicles Derived from Bone Marrow Mesenchymal Stem Cells and Their Capacities Supporting ex vivo Expansion of Hematopoietic Stem Cells].

Objective: To explore the biological characteristics of microvesicles(MV) derived from bone marrow mesenchymal stem cells (BM-MSC) and their capability supporting ex vivo expansion of hematopoietic stem cells(HSC).

Methods: The MV from cultured BM-MSC supernatant were isolated by multi-step differential velocity contrifugation; the morphological characteristics of MV were observed by electron microscopy with negative staining of samples; the protein level in MV was detected by using Micro-BCA method; the surface markers on MV were analyzed by flow cytometry. The peripheral blood HSC(PB-HSC) were isolated after culture and mobilization; the experiment was diveded into 2 group: in MV group, the 10 mg/L MV was given, while in control group, the same volume of PBS was given; the change of PB-HSC count was observed by cell counting; the change of surface markers on PB-HSC was detected dynamically by flow cytometry; the cell colony culture was used to determin the function change of PB-HSC after co-culture with MV.

Results: MSC-MVs are 20-100 nm circular vesicles under electron microscope. About 10 µg protein could be extracted from every 1×10 MSC. The flow cytometry showed that CD63 and CD44 were positive with a rate of 96.0% and 50.2%, while the HLA-DR, CD34, CD29 and CD73 etc were negative. When being co-cultured with GPBMNC for 2 days, the cell number of MV groups was 1.49±0.15 times of the control group (P>0.05). When being co-cultured for 4 days, the cell number of MV groups was 2.20±0.24 times of the control group(P<0.05). The CD34 cell number of MV groups was 1.76±0.30 times the control group after culture for 2 day and 1.95±0.20 times after culture for 4 day.

Conclusion: The MV has been successfully extracted from MSC culture supernatant by multi-step differential velocity centrifugation. MSC-MV can promote HSC expansion in vitro.