OBJECTIVETo investigate the mechanisms underlying the incorporation of microparticles(MP) derived from human bone marrow mesenchymal stem cells (MSCs) into human umbilical cord endothelial cells (HUVECs).

METHODSMPs were isolated from the supernatants of MSCs which had exposed to a hypoxia/serum-deprivation condition. Electron microscope was used to identify the MPs. The surface molecule profile was evaluated with the bead-based flow cytometry technique. The expression level of the phosphatidylserine receptor (PSR) was detected by immunofluorescence cytochemistry. MPs were co-cultured with HUVECs in the presence or absence PSR-antibody, and the internalization of MPs was observed with laser scanning microscopy.

RESULTSThe MPs derived from MSCs expressed highly PS, while PSR expressed on the surface of HUVECs. The confocal result revealed that MPs could quickly be uptaken by the endothelial cells, and mainly distributed in the cytoplasm surrounding of the nuclei. The internalization of MPs reduced significantly after PSR specific blockage.

CONCLUSIONThe reaction between PS on the MP and the PSR of HUVECs plays an important role in the internalization of MSC-MPs.