Microparticles (MPs) act as vectors of bioactive molecules and disseminate biological information in the vascular compartment. MPs derived from kidney derived-mesenchymal stem cell (MSC) have been reported to ameliorate acute kidney injury. We carried out this study to investigate in vitro biologic effects of MSC-derived MP. MSC were cultured in hypoxic chamber in serum deprived MEM with hydrogen peroxide (200 uM) and MPs were isolated from supernatants by differential ultrafiltration (2,000x g, 10 min, 100,000x g, 1hr). In vitro cell viability and proliferative effects of MSC-derived MPs were assessed in cultured human umbilical vein endothelial cells (HUVEC) using Ez-cytox assay and BrdU assay. Presence of MP was confirmed by electron microscopy and flow cytometry. Flow-cytometry of MP demonstrated the presence of several adhesion molecules shown to be expressed on MSC membrane. The cell viability of HUVEC was significantly increased in the presence of MSC-derived MP in dose-dependent manner (Figure 1A). However, MSC-derived MPs didn``t show the anti-apoptotic effects on HUVEC. The BrdU assay indicated that MSC-derived MPs increased the proliferation of HUVEC (Figure 1B). The present study demonstrates that MSC-derived MP may effect on the cell viability and proliferation of HUVEC.